Natural Compounds in Pomegranates May Prevent Growth of Hormone-Dependent Breast Cancer

Eating fruit, such as pomegranates, that contain anti-aromatase phytochemicals reduces the incidence of hormone-dependent breast cancer, according to results of a study published in the January issue of Cancer Prevention Research, a journal of the American Association for Cancer Research.

Pomegranates. (Credit: iStockphoto/Valentyn Volkov)

Pomegranate is enriched in a series of compounds known as ellagitannins that, as shown in this study, appear to be responsible for the anti-proliferative effect of the pomegranate.

"Phytochemicals suppress estrogen production that prevents the proliferation of breast cancer cells and the growth of estrogen-responsive tumors," said principal investigator Shiuan Chen, Ph.D., director of the Division of Tumor Cell Biology and co-leader of the Breast Cancer Research Program at City of Hope in Duarte, Calif.

Previous research has shown that pomegranate juice -- punica granatum L -- is high in antioxidant activity, which is generally attributed to the fruit's high polyphenol content. Ellagic acid found in pomegranates inhibits aromatase, an enzyme that converts androgen to estrogen. Aromatase plays a key role in breast carcinogenesis; therefore, the growth of breast cancer is inhibited.

Chen, along with Lynn Adams, Ph.D., a research fellow at Beckman Research Institute of City of Hope, and colleagues, evaluated whether phytochemicals in pomegranates can suppress aromatase and ultimately inhibit cancer growth.

After screening and examining a panel of 10 ellagitannin-derived compounds in pomegranates, the investigators found that those compounds have the potential to prevent estrogen-responsive breast cancers. Urolithin B, which is a metabolite produced from ellagic acid and related compounds, significantly inhibited cell growth.

"We were surprised by our findings," said Chen. "We previously found other fruits, such as grapes, to be capable of the inhibition of aromatase. But, phytochemicals in pomegranates and in grapes are different."

According to Gary Stoner, Ph.D., professor in the Department of Internal Medicine at Ohio State University, additional studies will be needed to confirm the chemopreventive action of Urolithin B against hormone-dependent breast cancer.

"This is an in vitro study in which relatively high levels of ellagitannin compounds were required to demonstrate an anti-proliferative effect on cultured breast cancer cells," said Stoner, who is not associated with this study. "It's not clear that these levels could be achieved in animals or in humans because the ellagitannins are not well absorbed into blood when provided in the diet."

Stoner believes these results are promising enough to suggest that more experiments with pomegranate in animals and humans are warranted.

Powel Brown, M.D., Ph.D., medical oncologist and chairman of the Clinical Cancer Prevention Department at the University of Texas M. D. Anderson Cancer Center, agreed with Stoner's sentiments and said these results are intriguing. He recommended that future studies focus on testing pomegranate juice for its effect on estrogen levels, menopausal symptoms, breast density or even as a cancer preventive agent.

"More research on the individual components and the combination of chemicals is needed to understand the potential risks and benefits of using pomegranate juice or isolated compounds for a health benefit or for cancer prevention," Brown said. "This study does suggest that studies of the ellagitannins from pomegranates should be continued."

Until then, Stoner said people "might consider consuming more pomegranates to protect against cancer development in the breast and perhaps in other tissues and organs."

Flower Power May Reduce Resistance to Breast Cancer Drug Tamoxifen

Combining tamoxifen, the world's most prescribed breast cancer agent, with a compound found in the flowering plant feverfew may prevent initial or future resistance to the drug, say researchers at Georgetown Lombardi Comprehensive Cancer Center.

                                     Feverfew plant used in herbal medicines. (Credit: iStockphoto)

The finding, reported online Feb. 12 in The FASEB Journal, provides new insight into the biological roots of that resistance, and also tests a novel way to get around it.

"A solution to tamoxifen resistance is sorely needed, and if a strategy like this can work, it would make a difference in our clinical care of breast cancer," says the study's lead investigator, Robert Clarke, PhD, DSc, a professor of oncology and physiology & biophysics at Lombardi, a part of Georgetown University Medical Center (GUMC). Clarke is also the interim director of GUMC's Biomedical Graduate Research Organization.

Clarke added that the purified research chemical they tested, parthenolide, a derivative of feverfew, is being tested by other scientists as treatment for a variety of cancers, as well as other health conditions. Feverfew has long been a staple of natural medicine, and is particularly known for its effects on headaches and arthritis. Latin for "fever reducer," feverfew is a common garden bush with small daisy-like flowers.

"The chemical clearly has potential, and we ought to be able to figure out fairly quickly if it can help solve tamoxifen's resistance problem," Clarke says.

Tamoxifen is a treatment of choice for breast cancer that is estrogen receptor positive (ER+), meaning that the hormone estrogen drives cancer growth. Most newly diagnosed breast cancers -- about 70 percent -- fall into that category. But about half of these cancers do not initially respond to tamoxifen, which is designed to block the hormone from binding to the cell's protein receptor, and many patients that do respond are at risk for developing resistance and cancer relapse.

In this study, Clarke and a team of researchers set out to study if, as previous research had suggested, tamoxifen resistance is regulated by the protein complex NF-κB (nuclear factor kappa B), which is often found to be over-expressed in ER+ breast cancer. NF-κB is known to help cells survive when damaged. The researchers had earlier discovered that NF-κB is over-expressed in cells that are resistant to tamoxifen, and they had found that resistance to another tamoxifen-like drug, fulvestrant, was controlled by a protein (Bcl2) that is, itself, regulated by NF-κB.

"Our scientific quest was to see if blocking NF-?B affects tamoxifen resistance, and if it does, why?" says Clarke.

They conducted a variety of tests using parthenolide, which has been shown to act on NF-κB. They found that in resistant breast cancer cells, the chemical blocked the activity of NF-κB, making the cells sensitive once again to tamoxifen. They then silenced NF-B in tamoxifen resistant cells, and found that this had the same effect as using parthenolide.

They further found that increased activation of NF-κB can alter sensitivity of tamoxifen by modulating the protein CASP8, which is involved in programmed cell death. That then affects Bcl2, which also helps push a damaged cell to die.

"When you give tamoxifen to a breast cancer cell, that is essentially a pro-death signal, because you are blocking the cell's access to estrogen, and the cell recognizes this is a mortal blow," Clarke says. "Such a damaged cell uses CASP8 and Bcl2 to trigger the cell machinery needed for dying.

"But the cell has ways to counteract the pro-death signal, and one important one is to activate NF-κB, which can control expression of genes necessary for survival," he says. "Now the cell thinks it should be living, not dying."

Because NF-κB controls CASP8 and Bcl2, it can turn those proteins essentially off, Clarke says. "The pro-survival signals override the pro-death signals."

Still, as much as this study advances the understanding of tamoxifen resistance, there is much that is not understood, he adds. "We don't know when NF-κB becomes over-expressed in the transformation of tamoxifen-sensitive to a tamoxifen-resistant breast cancer cells, and we don't know of other adaptations the cell may have made," he says. "It is probably fair to say this is a hideously complex process."

To that end, Clarke cannot predict how many women who try a combination of tamoxifen and parthenolide will benefit. He says the science is much too early to make any recommendations and strongly warns women against adding feverfew supplements to their cancer treatment.

Still, he is hopeful. "Every breast tumor slightly different, but we know many do use NF-κB because excess amounts of the protein are found in these cancers," he says. "That suggests they may be sensitive to targeted approaches that shut down this pro-survival signal."

The study was funded by grants from the U.S. Department of Defense, the Army Medical Research and Material Command, and the National Institutes of Health

'Microtentacles' On Tumor Cells Appear to Play Role in How Breast Cancer Spreads

Researchers at the University of Maryland Marlene and Stewart Greenebaum Cancer Center have discovered that "microtentacles," or extensions of the plasma membrane of breast cancer cells, appear to play a key role in how cancers spread to distant locations in the body. Targeting these microtentacles might prove to be a new way to prevent or slow the growth of these secondary cancers, the scientists say.

Two breast tumor cells attaching to each other. The red color shows the surface of both tumor cells, while the green color shows how the microtentacles from one cell encircle the neighboring cell. (Credit: Copyright University of Maryland Greenebaum Cancer Center)

They report in an article to be published online March 15, 2010, in the journalOncogene that a protein called "tau" promotes the formation of these microtentacles on breast tumor cells which break away from primary cancers and circulate in the bloodstream. While twisted remnants of tau protein have been seen in the brain tissue of patients with Alzheimer's disease, this is the first report that tau could play a role in tumor metastasis by changing the shape of cancer cells. These tau-induced microtentacles can help the cells reattach to the walls of small blood vessels to create new pockets of cancer.

"Our study demonstrates that tau promotes the creation of microtentacles in breast tumor cells. These microtentacles increase the ability of circulating breast tumor cells to reattach in the small capillaries of the lung, where they can survive until they can seed new cancers," says the senior author, Stuart S. Martin, Ph.D., a researcher at the University of Maryland Greenebaum Cancer Center and associate professor of physiology at the University of Maryland School of Medicine. Michael A. Matrone, Ph.D., is the study's lead author.

Healthy cells are programmed to die -- a process called apoptosis -- after they break off of epithelial layers that cover internal organs in the body. They also can be crushed if they are forced through small capillaries. However, cancer cells are able to survive for weeks, months and even years in the body. Once they are trapped in small blood vessels, the cells can squeeze through microscopic gaps in the vessels' lining and spread to organs such as the brain, lung and liver.

"We hope that through our research, we will be able to identify drugs that will target the growth of these microtentacles and help to stop the spread of the original cancer. Drugs that reduce tau expression may hold potential to inhibit tumor metastasis," Dr. Martin says.

He notes that metastatic cancers are the leading cause of death in people with cancer, but methods used to treat primary tumors have limited success in treating metastatic cancer. In breast cancer, metastases can develop years after primary tumors are first discovered.

Tau is present in a subset of chemotherapy-resistant breast cancers and is also associated with poor prognosis, but Dr. Martin adds, "While tau expression has been studied in breast cancers for contributing to chemotherapy resistance, the protein's role in tumor cells circulating in the bloodstream hasn't been investigated. And that's the focus of our research."

In this recent study, the University of Maryland researchers analyzed breast tumor cells from 102 patients and found that 52 percent had tau in their metastatic tumors and 26 percent (27 patients) showed a significant increase in tau as their cancer progressed. Twenty-two of these patients even had tau in metastatic tumors despite having none in their primary tumors.

Dr. Martin says more studies are needed to determine if tau is a clear predictor of metastasis. Given the complex nature of tumors, there most likely are other factors involved in causing cancers to spread, he says.

"Metastasis is a very major concern for people diagnosed with cancer, and the discovery of these microtentacles and the role that tau plays in their formation is a very exciting development that holds great promise for developing new drugs," says E. Albert Reece, M.D., Ph.D., M.B.A., acting president of the University of Maryland, Baltimore, and dean of the University of Maryland School of Medicine.

The University of Maryland, Baltimore, has filed patents on the microtentacle discoveries of Dr. Martin's lab group and is looking to partner with biopharmaceutical companies on new drug development. The researchers identified these cell extensions while they were studying the effects of two drugs that prevent cell division, or mitosis. Most chemotherapy drugs target cell division, aiming to slow or stop tumor growth.

Dr. Martin says his team found that a popular chemotherapy drug, taxol, actually causes cancer cell microtentacles to grow longer and allows tumor cells to reattach faster, which may have important treatment implications for breast cancer patients. Their studies are continuing.

"We think more research is needed into how chemotherapies that slow down cell division affect metastasis. The timing of giving these drugs can be particularly important. If you treat people with taxol before surgery to shrink the primary tumor, levels of circulating tumor cells go up 1,000 to 10,000 fold, potentially increasing metastasis," he adds.

The study being published in Oncogene was funded by grants from the National Cancer Institute, the USA Medical Research and Materiel Command, and the Flight Attendants Medical Research Institute.

Hormone Sensitivity of Breast Stem Cells Presents Drug Target

 Researchers at the Walter and Eliza Hall Institute have discovered that breast stem cells are exquisitely sensitive to the female hormones oestrogen and progesterone, a finding that opens the way for the development of new preventions and treatments for breast cancer.

 Breast stem cells retain a 'memory' of prior female hormone deprivation. These images show mammary (breast) outgrowths (blue branches) derived from stem cells. Stem cells from female mice whose ovaries had been removed produced fewer and smaller outgrowths (left panel) than control mice (right panel). (Credit: Marie-Liesse Asselin-Labat, Walter and Eliza Hall Institute)

 

The discovery, by scientists in the institute's Stem Cells and Cancer and Bioinformatics divisions, also explains decades of evidence linking breast cancer risk to exposure to female hormones.

It has been published online April 11 in the journal Nature.

Dr Jane Visvader, who led the research with Dr Geoff Lindeman, said sustained exposure to oestrogen and progesterone was a well-established risk factor for breast cancer. "There is a clear evidence that the more menstrual cycles a woman has the greater her breast cancer risk," Dr Visvader said. "There is even an increase in breast cancer risk in the short-term following pregnancy. However the cellular basis for these observations has been poorly understood."

In the mid-2000s, Drs Visvader and Lindeman discovered breast stem cells in both mice and humans. Unexpectedly, however, they also found that breast stem cells lacked 'receptors' that would allow them to be directly controlled by the female hormones oestrogen and progesterone.

Now, work by Drs Visvader and Lindeman in collaboration with Drs Marie-Liesse Asselin-Labat, Gordon Smyth and others at the institute, has revealed that despite lacking receptors for oestrogen and progesterone, breast stem cells are still remarkably sensitive to female hormones.

Using mouse models, they showed that when the ovaries were removed or the animals were treated with hormone inhibitors (which are in clinical use as anti-breast cancer agents), breast stem cell numbers dropped and the cells appeared to become dormant.

Dr Lindeman, who is also a medical oncologist at the Royal Melbourne Hospital, said this finding helped to explain why the effects of 'chemoprevention' -- a treatment aimed at breast cancer prevention continued long after anti-estrogen tablets have been stopped.

"Our research also revealed that during pregnancy there is a profound increase in breast stem cell numbers," Dr Lindeman said.

"This might account for the short-term increase in cancer risk associated with pregnancy."

Further studies, in collaboration with Dr Jack Martin at St Vincent's Institute Melbourne and Dr Hisataka Yasuda at the Nagahama Institute for Biochemical Science, identified the RANK ligand pathway as the key cell-signalling pathway responsible for the indirect control of breast stem cells in pregnancy.

Dr Lindeman said inhibitors of RANK signalling have been developed and are currently in clinical trials to help maintain bone strength and treat breast cancer that has spread to the bones. "Our discovery suggests that inhibitors of RANK or other stem cell pathways represent possible therapeutic strategies that could also be investigated as breast cancer prevention agents," Dr Lindeman said.

The research was supported by the Victorian Breast Cancer Research Consortium / Victoria Cancer Agency, Susan G. Komen Foundation, National Breast Cancer Foundation, National Health and Medical Research Council, and the Australian Cancer Research Foundation.

Bone Drug Suppresses Wandering Tumor Cells in Breast Cancer Patients; May Reduce Metastatic Disease

The bone-strengthening drug zoledronic acid (Zometa) can help fight metastatic breast cancer when given before surgery, suggests research at Washington University School of Medicine in St. Louis.

Breast cancer cells taken from a patient's bone marrow. The cancer cells are stained to make them easy to spot among the normal cells of the bone marrow. (Credit: Image courtesy of Washington University School of Medicine)

When the drug was given along with chemotherapy for three months before breast cancer surgery, it reduced the number of women who had tumor cells in their bone marrow at the time of surgery.

The study was published in the May issue of The Lancet Oncology.

Every day, tumors shed thousands of cells, which spread throughout the body and are referred to as disseminated tumor cells (DTCs). Breast cancer DTCs often lodge in bone marrow where bone growth factors help them survive.

Chemotherapy can increase bone turnover and bone growth factors, potentially exacerbating the problem of DTCs in the bone, which can resurface later to cause metastatic disease in cancer patients.

"Bone marrow seems to be a DTC sanctuary, allowing them to adapt and disseminate to different organs, where they're a leading cause of death," says study leader Rebecca Aft, MD, PhD, associate professor of surgery and a breast cancer specialist at the Alvin J. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine. "We believe that zoledronic acid inhibits the release of growth factors that help support the growth of DTCs."

Zoledronic acid is generally prescribed to reduce and delay bone complications due to multiple myeloma and bone metastases from solid tumors. Two recent studies showed that zoledronic acid improves disease-free survival when used along with estrogen-lowering therapy before breast cancer surgery. Estrogen-lowering therapy, like chemotherapy, potentially increases bone loss.

In this randomized phase II clinical trial, researchers split 109 women with newly diagnosed stage II or stage III breast cancer into two groups. The control group received chemotherapy alone, while the other received a combination treatment of chemotherapy and zoledronic acid.

After three months of therapy, patients with DTCs in their bone marrow decreased from 43 percent to 30 percent in the combination group, compared with a decrease from 48 percent to 47 percent in the control group. This result approached statistical significance.

The researchers also found that of those patients who had no DTCs in their bone marrow at the start of the study, 87 percent remained negative after three months of combination treatment compared to 60 percent of those who received chemotherapy alone, a result that was statistically significant.

Zoledronic acid treatment with chemotherapy had additional benefits. Women in the combination group experienced significant gains in bone density after 12 months. This is helpful for breast cancer patients, who often develop osteoporosis as a side effect of chemotherapy and other breast cancer treatments.

The study also suggested that zoledronic acid may help fight certain types of breast tumors directly. Aft speculates that the drug may stop the tumor from making its own blood supply, modify the immune system in a way that makes it harder for tumor cells to survive or even cause the cancer cells to commit suicide.

"Although it's common practice to administer zoledronic acid during chemotherapy given after breast cancer surgery, it isn't common when chemotherapy is given before surgery," Aft says. "Because chemotherapy increases bone loss, we would argue that women should receive zoledronic acid at the time of chemotherapy in the presurgical setting. Our single-institutional study also suggests that similar protocols using zoledronic acid for high-risk breast cancer patients should continue to be tested in larger, multi-institutional studies."

This research was supported by funding from Novartis Pharmaceuticals and Pfizer Inc. Rebecca Aft and Katherine Weilbaecher have received honoria from Novartis. Michael Naughton has received honoria from Novartis, Sanofi -Aventis, and Pfizer. Matthew Ellis is a consultant for Novartis and has received honoria and research funds from Novartis. Kathryn Diemer has received honoria from Novartis.

Adult Mammary Stem Cells in Mice Identified and Isolated for First Time

For the first time, researchers at Fred Hutchinson Cancer Research Center have identified and isolated adult mammary stem cells in mice. Long-term implications of this research may include the use of such cells to regenerate breast tissue, provide a better understanding of the role of adult stem cells in breast cancer development, and develop potential new targets for anti-cancer drugs.

Green fluorescent protein-positive mammary stem cells in mammary tissue of a pubescent mouse. (Credit: The laboratory of Larry Rohrschneider, Ph.D., Basic Sciences Division, Fred Hutchinson Cancer Research Center)

The findings, by Larry Rohrschneider, Ph.D., a member of the Basic Sciences Division at the Hutchinson Center, and Lixia Bai, M.D., Ph.D., a research associate in his lab, are published in the Sept. 1 issue of Genes & Development.

Using a genetically modified mouse model, the researchers tagged stem cells with green fluorescent protein (GFP), which exhibits bright green fluorescence during gene expression and can be easily seen under a microscope. GFP expression is controlled by the promoter of a newly identified gene, specifically expressed in stem cells, called s-SHIP.

"Until now, we have not been able to identify stem cells in mammary tissue. They have never been detected before with such specificity. It is extraordinary. You can see these green stem cells under the microscope in their pure, natural state," said Rohrschneider, who has filed a patent on the s-SHIP promoter-GFP-labeling technology.

Previous systems for isolating stem cells have relied on a variety of biomarkers, none of which have yielded a pure stem cell population. This limitation has prohibited accurate gene-expression analysis of such cells.

The researchers demonstrated the presence of active green stem cells at crucial stages of mammary development, such as puberty and pregnancy. During quiescent stages of development, however, the cells did not "light up."

Such stem cells represent a new alternative to induced pluripotent stem cells, or genetically altered stem cells, for various medical applications.

For example, by isolating the pure green mammary cells from donor female transgenic mice, the researchers have demonstrated the regenerative ability of these cells by transplanting them into the mammary fat tissue of recipient mice whose own mammary epithelium has been removed.

"We have found that those transplanted green stem cells can generate new mammary tissue and this tissue can produce milk, just like normal mammary epithelial cells," said co-author Bai. "Identification of the exact stem cell and its location is the first critical and fundamental step toward understanding the regulatory mechanisms of these important cells."

In addition to potential clinical applications regarding tissue regeneration, the researchers see these isolated stem cells as a window to better understanding how normal stem cells can become cancer stem cells, which are hypothesized to exist in tumors.

"Our belief right now is that perhaps the most aggressive tumors may be coming from the malignant transformation of stem cells in healthy tissue," Rohrschneider said. "This new technology offers a unified model for identifying normal and cancer stem cells."

Cancer stem cells are thought to be responsible for tumor initiation, growth, metastasis, therapy resistance and disease relapse.

"Because stem cells are critical for both normal tissue development and cancer development, exploring how they are regulated in normal development will help us to better understand how they are transformed into breast cancer cells," Bai said. "By searching for new methods to effectively and specifically target cancer stem cells, we hope we can cure breast cancer someday." she said.

The National Institutes of Health, the National Cancer Institute, the Hutchinson Center and financial support from anonymous donors supported this work.

How HRT and the Pill Can Lead to Breast Cancer: New Research Suggests Possible Treatment

Breast cancer is one of the most common cancers, affecting up to one in eight women during their lives in Europe, the UK and USA. Large population studies such as the Women's Health Initiative and the Million Women Study have shown that synthetic sex hormones called progestins used in hormone replacement therapy, HRT, and in contraceptives can increase the risk of breast cancers.

Scientists have uncovered how hormone replacement therapy can increase the risk of breast cancer, according to new research published on Nature’s website today (Wednesday 29 September, 2010). They found that the link is a protein molecule RANKL, which is essential to regulate bone mass and which is also involved in milk production. The Austrian researchers have shown that a synthetic progesterone, frequently used in HRT and hormonal contraception, can switch on the activity of RANKL within breast cells, causing them to divide and multiply and preventing them from dying when they should. Moreover, stem cells in the breast become able to renew themselves, ultimately resulting in breast cancer. (Credit: Copyright IMBA)

Now medical researchers at the Institute of Molecular Biotechnology of the Austrian Academy of Sciences in Vienna have identified a key mechanism which allows these synthetic sex hormones to directly affect mammary cells.

The research builds on previous work by Prof Josef Penninger, the IMBA director, who found the first genetic evidence that a protein called RANKL is the master regulator of healthy bones. In a complex system that regulates bone mass, RANKL activates the cells that break down bone material when it needs to be replaced. When the system goes wrong and we make too much of the protein it triggers bone loss, leading to osteoporosis in millions of patients around the world every year. Finding exactly the same molecule in breast tissues led the scientists to the new link between sex hormones and breast cancer.

In a scientific article published in the journal Nature, the research team show that a synthetic female sex hormone used in HRT and contraceptive pills can trigger RANKL in breast cells of mice. As a consequence, these mammary cells start to divide and multiply and fail to die when they should. Moreover, stem cells in the breast become able to renew themselves, ultimately resulting in breast cancer.

In a different set of mouse treatment tests, reported in a secondNature article, researchers at Amgen have found that pharmacologic blocking of the RANKL system significantly delays mammary tumor formation leading to significantly fewer breast cancers in mice. In another mouse model, RANKL inhibition not only decreased breast tumor formation but also reduced lung metastasis.

"Ten years ago we formulated the hypothesis that RANKL might be involved in breast cancer and it took us a long time to develop systems to prove this idea," says Prof Josef Penninger. " I have to admit it completely surprised me just how massive the effects of the system were. Millions of women take progesterone derivatives in contraceptives and for hormonal replacement therapy. Since our results show that the RANKL system is an important molecular link between a synthetic sex hormone and breast tumors, one day women may be able to reduce their risk by taking blocking medicines in advance to prevent breast cancer."

A monoclonal antibody, denosumab, that blocks RANKL has been recently approved in the US and the EU for the treatment of osteoporosis, and is currently under review for the treatment of bone metastases in patients with advanced cancer. "Further studies will be needed to prove the principle of our findings," says Dr Daniel Schramek, who carried out the studies with Prof Josef Penninger at the Institute of Molecular Biotechnology in Vienna. "But we hope that medical trials using denosumab can be started in the near future to test whether the mouse studies can be directly translated to human breast cancer."

This work was an international collaboration between lead researchers at IMBA and scientists at the Medical University of Vienna; the Garvan Institute of Medical Research, Sydney, Australia; the Ontario Cancer Institute, University of Toronto, Toronto, Canada; Harvard School of Public Health, Harvard Medical School and the Ragon Institute of MGH/MIT and Harvard, Boston, USA; the Institute for Genetics, Centre for Molecular Medicine (CMMC), and Cologne Excellence Cluster (CECAD), University of Cologne, Germany; University College London, UK; and the University of Erlangen-Nuremberg, Germany.

Annual Breast Cancer Screening Beginning at Age 40 Reduces Mastectomy Risk, Study Finds

 Having a yearly mammogram greatly reduces the risk of mastectomy following breast cancer in women between the ages of 40 and 50, according to a study presented today at the annual meeting of the Radiological Society of North America (RSNA).

Mammography image showing localized malignancy which allows treatment with conservative surgery to the breast. (Credit: Image courtesy of Radiological Society of North America)

"The results of this study support the importance of regular screening in the 40 to 50 age group," said lead author Nicholas M. Perry, M.B.B.S., F.R.C.S., F.R.C.R., director of The London Breast Institute at The Princess Grace Hospital in London. "Women in this age group who had undergone mammography the previous year had a mastectomy rate of less than half that of the others."

An estimated 207,090 new cases of invasive breast cancer will be diagnosed in American women in 2010. Currently, the American Cancer Society recommends annual mammography screening for women beginning at age 40 in the U.S., but last year, the U.S. Preventive Services Task Force recommended changing the guidelines to begin screening biennially (every other year) at age 50. There are no routine screening guidelines for women under 50 in the U.K.

The researchers studied the benefits of screening women between the ages of 40 and 50, the frequency of mammography and the type of treatment after breast cancer diagnosis.

Dr. Perry and colleagues reviewed the clinical data available on women from 40 to 50 that had been diagnosed with breast cancer and treated at The London Breast Institute. Between 2003 and 2009, 971 women had been diagnosed with breast cancer. At the time of diagnosis, 393 (40 percent) of the women were under 50, with 156 of these women completing treatment at the center. Of the treated women, 114 (73 percent) had no prior mammograms. Forty-two women had been previously screened with mammography, of whom 29 had at least one mammogram within the previous two years. Of those, 16 women had a mammogram one year prior.

"We reviewed the records of the women needing mastectomy to determine whether or not they had undergone mammography the previous year," Dr. Perry said. "We were surprised at the degree of benefit obtained from yearly screening in this age group."

Data showed that mastectomy was the required treatment for 3 (19 percent) of the 16 women who had been screened the prior year, compared to 64 (46 percent) of the 140 women who had not been screened in the past year.

"Regular screening is already proven to lower the chance of women dying from breast cancer," Dr. Perry said. "The results of our study support the importance of regular screening in the under-50 age group and confirm that annual mammography improves the chances of breast conservation should breast cancer develop."

Dr. Perry's coauthors are Sue Milner, B.Sc., D.C.R., Kefah Mokbel, M.B.B.S., M.S., F.R.C.S., Stephen W. Duffy, B.Sc., M.Sc., and Katja Pinker, M.D.

Potential Target for Breast Cancer Therapy

Overexpression or hyperactivation of ErbB cell-surface receptors drives the growth of many breast cancers. Drugs, like Herceptin, that block the receptors' signals halt tumor progression in some patients. However, not all patients' tumors respond, with some becoming resistant over time. Different drugs that interfere with other steps in the signaling pathway may improve the response of patients, yet little is known about these molecules.

Mammary tissue with cancer cells positive for P-Rex1 (inside oval, stained brown). P-Rex1 is expressed only in the cancer cells but not in the normal tissue. (Credit: Marcelo G. Kazanitez, PhD, University of Pennsylvania School of Medicine)

Now, Marcelo G. Kazanietz, PhD, professor of Pharmacology at the University of Pennsylvania School of Medicine and colleagues, report that a protein called P-Rex1 is crucial for signal transmission from ErbB receptors. What's more, they found that P-Rex1 is overexpressed in nearly 60 percent of breast cancer samples tested and patients whose tumors express P-Rex1 were more likely to develop metastasis, compared with those whose tumors did not express P-Rex1.

"We identified a downstream target of the ErbB receptors which seems to be crucial for cancer cell proliferation, migration, and metastasis," Kazanietz says. "Understanding how this pathway works should allow us to find new drugs or therapeutic approaches in the future."

The team's research is featured on the cover of the December 22 issue of Molecular Cell.

A Well-Known Family

The ErbB family of receptors is well known in the cancer world. The family includes the epidermal growth factor receptor (EGFR, also known as ErbB1); ErbB2 (also known as HER2/neu), which is the target of Herceptin; as well as ErbB and ErbB4.

Previous work from Kazanietz and others suggested the receptors might rely on small proteins in the Rac pathway to help transmit their signal. To find out if that was the case, Kazanietz and colleagues examined human breast cancer cell lines and found that one Rac pathway protein, P-Rex1, is overexpressed in numerous cell lines compared with normal mammary cells. The team also found that P-Rex1 is present in some breast tumors, particularly those that express the Her2/neu receptor or estrogen receptor and belong to the luminal subtype.

"We found that about two-thirds of the patient samples had very high levels of P-Rex1 expression in tumor cells in their lymph nodes," Kazanietz says. "There seems to be a correlation between P-Rex1 expression in the tumor cells and the capacity of these cells to metastasize. And since P-Rex1 is likely to be essential for cell migration and migration is essential for metastasis, we believe blocking this pathway could reduce the risk of metastasis."

P-Rex1 may be important for several other cancer-promoting pathways. For example, estrogen-receptor signaling also appears to rely on P-Rex1, which means that targeted inhibitors of P-Rex1 might improve responses to anti-estrogen therapies such as tamoxifen.

The authors also found that P-Rex1 is also used by another receptor, CXCR4, which has recently shown up in many cancer studies. Despite being used in numerous pathways during cancerous growth, P-Rex1 is not expressed in many normal tissues. "That gives us a very good target. It is really cancer specific," Kazanietz says. "What's more, as P-Rex1 is expressed in some subtypes of breast tumors, it may be an excellent prototype for future personalized medicine."

Preclinical data from other groups supports the importance of the Rac pathway in cancer, according to Kazanietz. And small molecule inhibitors that block proteins in the Rac pathway appear to have strong anti-cancer effects in model systems, though their use in patients still needs to be tested.

This work has been supported by grants from the National Cancer Institute and the Susan Komen Foundation for the Cure.

Maria Soledad Sosa and Cynthia Lopez-Haber from the Penn Department of Pharmacology were co-first authors on the study. Additional co-authors include Hongbin Wang and Mark A. Lemmon from Penn; Chengfeng Yang from Michigan State University, East Lansing; John M. Busillo, Jiansong Luo, and Jeffrey L. Benovic from Thomas Jefferson University, Philadelphia; Andres Klein-Szanto, from Fox-Chase Cancer Center, Philadelphia; Hiroshi Yagi and J. Silvio Gutkind from the National Institute of Dental and Craniofacial Research, Bethesda, MD; and Ramon E. Parsons from Columbia University Medical Center, New York.

Scientists Bring Cancer Cells Back Under Control

Scientists at The University of Nottingham have brought cancer cells back under normal control -- by reactivating their cancer suppressor genes. The discovery could form a powerful new technology platform for the treatment of cancer of the breast and other cancers.

Tumor reduction. (Credit: Image courtesy of University of Nottingham)

Breast cancer is diagnosed in about 1.4 million women throughout the world every year, with half a million dying from the disease. A common cause of cancer is when cells are altered or mutated and the body's tumour suppressor genes are switched off.

Research, published in the journalMolecular Cancer, reveals how Dr Cinzia Allegrucci from the School of Veterinary Science and Medicine and Dr Andrew Johnson in the Centre for Genetics and Genomics reactivated tumour suppressor genes and stopped the cancer from growing by treating them with Axolotl oocyte extract. After 60 days there was still no evidence of cancerous growth.

Cancers occur when the mechanisms that control normal cell division are mutated. The process of cell division is controlled by specific genes and these are turned "on" or "off" depending on their function. Among the most important of these genes are tumour suppressor genes. These genes repress the development of cancers and normally act as a control point in the cell division cycle. Therefore, the switching off of tumour suppressor genes is a common cause of cancers, including breast cancer.

Dr Allegrucci, a lecturer in molecular genetics and cell biology, said: "The on/off switch in genes is controlled by the modification of proteins that are bound to the DNA in a cell -- so called epigenetic modifications. Tumour suppressor genes in many breast cancers are switched off by epigenetic marks, which is the underlying cause of tumours. We sought to reverse this process, activating the tumour suppressor genes, in hope of stopping cancerous cell divisions."

Dr Johnson said: "To do this we used novel technology that makes use of the eggs of the axolotl salamander. Over the years Dr Johnson's lab has shown that humans evolved from animals that closely resemble axolotls, and because of this the proteins in axolotls are very similar to those in humans. Axolotl oocytes -- which are the eggs prior to ovulation -- are packed with molecules that have very powerful epigenetic modifying activity. Previously Johnson's lab showed that extracts prepared from these oocytes have powerful capacity to change epigenetic marks on the DNA of human cells.

And, in a breakthrough, they showed it is important to use oocytes from the ovary, because if the oocytes are ovulated these activities are lost. We thought that by treating cancer cells with extracts made from axolotl oocytes we could reverse the epigenetic marks on tumour suppressor genes, causing these genes to reactivate, and thereby stopping the cancerous cell growth."

The identification of the proteins responsible for this tumour reversing activity in axolotl oocytes is a major goal of future research which could form a powerful new technology platform for the treatment of cancers from the breast, and other tissues.

Discovery of a Biochemical Basis for Broccoli's Cancer-Fighting Ability

Scientists are reporting discovery of a potential biochemical basis for the apparent cancer-fighting ability of broccoli and its veggie cousins. They found for the first time that certain substances in the vegetables appear to target and block a defective gene associated with cancer.

Broccoli. Scientists are reporting discovery of a potential biochemical basis for the apparent cancer-fighting ability of broccoli and its veggie cousins. They found for the first time that certain substances in the vegetables appear to target and block a defective gene associated with cancer. (Credit: iStockphoto)

Their report, which could lead to new strategies for preventing and treating cancer, appears in ACS' Journal of Medicinal Chemistry.

Fung-Lung Chung and colleagues showed in previous experiments that substances called isothiocyanates (or ITCs) -- found in broccoli, cauliflower, watercress, and other cruciferous vegetables -- appear to stop the growth of cancer. But nobody knew exactly how these substances work, a key to developing improved strategies for fighting cancer in humans. The tumor suppressor gene p53 appears to play a key role in keeping cells healthy and preventing them from starting the abnormal growth that is a hallmark of cancer. When mutated, p53 does not offer that protection, and those mutations occur in half of all human cancers. ITCs might work by targeting this gene, the report suggests.

The scientists studied the effects of certain naturally-occurring ITCs on a variety of cancer cells, including lung, breast and colon cancer, with and without the defective tumor suppressor gene. They found that ITCs are capable of removing the defective p53 protein but apparently leave the normal one alone. Drugs based on natural or custom-engineered ITCs could improve the effectiveness of current cancer treatments or lead to new strategies for treating and preventing cancer.

The authors acknowledged funding from the Ruth L. Kirschstein National Research Service Award and a grant from the National Cancer Institute of the National Institutes of Health.

DNA of 50 Breast Cancer Patients Decoded

 In the single largest cancer genomics investigation reported to date, scientists have sequenced the whole genomes of tumors from 50 breast cancer patients and compared them to the matched DNA of the same patients' healthy cells. This comparison allowed researchers to find mutations that only occurred in the cancer cells.

The above Circos plot is a visual representation of the genomic disruptions in one of the breast cancers studied. (Credit: Matthew J. Ellis, MD, PhD)

They uncovered incredible complexity in the cancer genomes, but also got a glimpse of new routes toward personalized medicine. The work was presented at the American Association for Cancer Research 102nd Annual Meeting 2011.

In all, the tumors had more than 1,700 mutations, most of which were unique to the individual, says Matthew J. Ellis, MD, PhD, professor of medicine at Washington University School of Medicine in St. Louis and a lead investigator on the project.

"Cancer genomes are extraordinarily complicated," Ellis says. "This explains our difficulty in predicting outcomes and finding new treatments."

To undertake the massive task, Washington University oncologists and pathologists at the Alvin J. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine collaborated with the university's Genome Institute to sequence more than 10 trillion chemical bases of DNA -- repeating the sequencing of each patient's tumor and healthy DNA about 30 times to ensure accurate data.

"The computing facilities required to analyze this amount of data are similar in scale to those of the Large Hadron Collider, used to understand the workings of sub-atomic particles," Ellis says.

The DNA samples came from patients enrolled in a clinical trial that Ellis is leading for the American College of Surgeons Oncology Group. All patients in the trial had what is called estrogen-receptor-positive breast cancer. These cancer cells have receptors that bind to the hormone estrogen and help the tumors grow.

To slow tumor growth and make the tumors easier to remove, patients received estrogen-lowering drugs before surgery. But, for unknown reasons, this treatment does not always work. Twenty-four of the 50 tumor samples came from patients whose tumors were resistant to this treatment, and 26 came from patients whose tumors responded. Comparing the two groups might help explain why some estrogen-receptor-positive breast cancer patients do well with estrogen-lowering drugs and others poorly.

Confirming previous work, Ellis and colleagues found that two mutations were relatively common in many of the patients' cancers. One called PIK3CA is present in about 40 percent of breast cancers that express receptors for estrogen. Another called TP53 is present in about 20 percent.

Adding to this short list of common mutations, Ellis and colleagues found a third, MAP3K1, that controls programmed cell death and is disabled in about 10 percent of estrogen-receptor-positive breast cancers. The mutated gene allows cells that should die to continue living. Only two other genes, ATR and MYST3, harbored mutations that recurred at a similar frequency as MAP3K1 and were statistically significant.

"To get through this experiment and find only three additional gene mutations at the 10 percent recurrence level was a bit of a shock," Ellis says.

In addition, they found 21 genes that were also significantly mutated, but at much lower rates -- never appearing in more than two or three patients. Despite the relative rarity of these mutations, Ellis stresses their importance.

"Breast cancer is so common that mutations that recur at a 5 percent frequency level still involve many thousands of women," he says.

Ellis points out that some mutations that are rare in breast cancer may be common in other cancers and already have drugs designed to treat them.

"You may find the rare breast cancer patient whose tumor has a mutation that's more commonly found in leukemia, for example. So you might give that breast cancer patient a leukemia drug," Ellis says.

But such treatment is only possible when the cancer's genetics are known in advance. Ideally, Ellis says, the goal is to design treatments by sequencing the tumor genome when the cancer is first diagnosed.

"We get good therapeutic ideas from the genomic information," he says. "The near-term goal is to use information on whole genome sequencing to guide a personalized approach to the patient's treatment."

This work builds on previous collaborations between Washington University oncologists and the Genome Institute. In a study published last year in Nature, they reported the complete tumor and normal DNA sequences of a woman with "triple-negative" breast cancer, a particularly aggressive type that is difficult to treat and more common in younger women and African-Americans.

While many mutations are rare or even unique to one patient, Ellis says quite a few can be classified on the basis of common biological effects and therefore could be considered together for a particular therapeutic approach.

Ellis looks to future work to help make sense of breast cancer's complexity. But these highly detailed genome maps are an important first step.

"At least we're reaching the limits of the complexity of the problem," he says. "It's not like looking into a telescope and wondering how far the universe goes. Ultimately, the universe of breast cancer is restricted by the size of the human genome."

Reference: Ellis et al. Breast cancer genome. Presented April 2, 2011, at the 102nd Annual Meeting of the American Association for Cancer Research in Orlando, Fla.

Ding L, Ellis MJ, Weinstock GM, Aft R, Watson M, Ley TJ, Wilson RK, Mardis ER et al. Cancer remodeling in a basal-like breast cancer metastasis and xenograft. Nature. April 15, 2010.

This work was supported by grants from the National Human Genome Research Institute, the Breast Cancer Research Foundation, the National Cancer Institute, Susan G. Komen for the Cure and Washington University School of Medicine.

Adipose Cells and Breast Cancer: A Dangerous Combination

Apart from its direct effect on health (such as cardiovascular diseases and diabetes), obesity is increasingly suspected of playing a role in the prognosis of breast cancer and, in particular, its propensity to spread. However, no direct cause and effect relationship had been demonstrated until now.

Section of tumor (mauve) in the presence of adipocytes (white discs). The arrows indicate adipocytes modified by the tumor. (Credit: Copyright G. Escourrou)

This breakthrough has finally been made through the collaborative work of two teams of researchers from Inserm, CNRS and the Université Paul Sabatier. Their research has made it possible to highlight, both in vitro and in vivo, the presence of adipose cells (known as adipocytes) near breast tumors. These adipocytes have specific biological characteristics. When associated with tumors, they are capable of modifying the characteristics of cancerous cells, making them more aggressive. The results of this work are published in Cancer Research on 1st April 2011.

Numerous statistical studies have already established a link between obesity and the "aggressiveness" of breast cancer in women, without ever succeeding to explain this phenomenon. In order to find an explanation, the researchers studied the cross-talk between adipose cells and tumor cells.

The external part of the breast essentially contains fat tissue, mainly composed of adipose cells. Apart from storing/releasing fats, these cells are capable of secreting numerous proteins. The researchers therefore attempted to find out whether these proteins play a role in the development of breast cancers.

To do so, the teams headed by Philippe Valet at the Institut des Maladies Métaboliques et Cardiovasculaires (Inserm/Université Paul Sabatier) and Catherine Muller at the Institut de Pharmacologie et de Biologie Structurale (CNRS/Université Paul Sabatier) used an original co-culture system between mammary tumor cells and adipocytes. In the presence of tumor cells, the adipocytes exhibit a modification in the secretion of some of their proteins, including inflammatory proteins such as interleukin-6 (IL-6). Adipose cells progressively establish a real interaction with the tumor, which leads to an increase in its "colonization potential" and thus its aggressiveness.

Indeed, when injecting mice with tumor cells co-cultivated beforehand with adipocytes, the researchers observed that the tumor was more likely to form metastases. A significant factor is that these specific modifications in adipocytes have been observed in human tumors, confirming the importance of the phenomenon. In addition, the researchers observed that the adipocytes near large human tumors, with ganglionic invasion, contained more IL-6. The protein could thus play an important role in the adipocyte-induced spread of breast cancer.

This works shows that adipocytes undoubtedly play an unexpected role in the spread of such tumors. "Our results now demonstrate how adipocytes actively participate in the progression of breast cancer, orchestrated by tumor cells. They suggest that in the case of obesity, the adipocytes associated with breast cancer could be more likely to amplify the 'aggressive' effect of tumors," the researchers say. "This hypothesis still needs to be verified both in mice and humans."

The study targets the development of specific strategies for overweight patients suffering from the most aggressive cancers. For example, identifying the signals supplied by the adipocytes to stimulate the invasive properties of tumor cells could represent a new lead for treating these patients.

This work is financially supported by the French National Cancer Institute.

Tiny Antibody Fragments Raised in Camels Find Drug Targets in Human Breast Cancer Cells

A new discovery published online inThe FASEB Journal promises to help physicians identify patients most likely to benefit from breast cancer drug therapies. If the compound, called "Nanobody," proves effective in clinical trials, it would represent a significant advance for breast cancer drug therapy because some drugs are effective only in some people.

Researchers have discovered that tiny antibody fragments raised in camels can find drug targets in human breast cancer cells. (Credit: © Oleg Seleznev / Fotolia)

In addition, some drugs have side effects that may cause damage to vital organs, making it more crucial for physicians to get the right treatment to the right patient the first time around.

"What makes Nanobodies so promising is that they are robust, small enough for rapid elimination from the body, and easy to produce at a relatively low cost," said Ilse Vaneycken, M.Sc., a researcher involved in the work.

To make this discovery, Vaneycken and her colleagues started with the target of the therapeutic drugs (HER2) and immunized a dromedary camel to raise special antibodies unique to this species. Next, all unnecessary parts of the camel's antibodies were removed and cloned in bacteria. Of 100 million bacterial clones, the team selected those that produced the 40 Nanobodies that recognized― or bound to―the same site targeted by therapeutic drugs. Of this group, the team screened for compounds that picked out breast cancer cells bearing the genetic tag HER2. Their lead compound did just that, and without blocking access to cancer-killing drugs now in use. Other properties of Nanobodies, such as good expression, stability, and visibility―enabled breast cancer tumors to be stained and seen rapidly―were also exploited.

"The scientists went over the hump to get to the lump so to speak," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "This technique not only promises to help doctors target cancer cells with effective drugs today, but to pick out other discrete cancer targets in the future."

New Strategy to Attack Tumor-Feeding Blood Vessels

Scientists at the Walter and Eliza Hall Institute have discovered a key molecule needed to kill the blood vessels that supply tumours.

Cancers such as breast cancer, lung cancer and melanoma release the blood vessel growth factor, VEGF, to encourage blood vessels to grow within the tumor, supplying it with nutrients. Tumors can be treated with anti-cancer medications that kill the cancer cells, and anti-angiogenic medications that starve the tumour by attacking its blood supply. The study suggests that a third type of medication, BH3-mimetics, may enhance the tumor-killing effect of anti-cancer and anti-angiogenic medications. (Credit: Walter and Eliza Hall Institute)

The research team from the institute's Molecular Genetics of Cancer and Cancer and Haematology divisions found that for anti-cancer therapies that target tumour blood vessels to work the death- inducing molecule Bim is required. The finding could lead to improved anti-cancer treatments that are based on a two- or three-pronged attack on both the tumour and its blood supply. The research will be published online in theJournal of Experimental Medicine.

The growth of solid tumours, such as lung cancer, breast cancer and melanoma, depends on nutrients and oxygen being provided by the tumour blood supply. Cancer cells encourage the growth of blood vessels to feed a tumour by producing the hormone-like protein, vascular endothelial growth factor (VEGF). The research by Drs Edwina Naik, Leigh Coultas and Lorraine O'Reilly, and Professors Jerry Adams and Andreas Strasser showed that VEGF produced by tumours blocks production of Bim in the cells that line the tumour blood vessels.

New 'anti-angiogenic' medications that attack the blood vessels within tumours are showing promise in starving many types of cancers by reducing their blood supply.

In this study, in experimental melanoma, lung cancer and breast cancer models, Bim levels increased in the cells lining the blood vessels when VEGF was depleted by anti-angiogenic drugs, ultimately killing the blood vessel cells. VEGF depletion reduced the number of blood vessels in tumours, making the tumours shrink. However, in mice in which the blood vessels do not express Bim, VEGF depletion did not affect the number of tumour-associated blood vessels, and tumours grown in Bim-deficient mice did not respond to anti-angiogenic treatments.

Dr Strasser said this finding suggests that strategies for treating tumours by attacking the tumour blood supply could be optimised by incorporating drugs called BH3-mimetics that cause cell death by acting like Bim at a molecular level. "Similarly, therapies that increase the amount of Bim in tumour blood vessels could enhance the effects of anti-angiogenic agents," Dr Strasser said.

"BH3 mimetics may have two beneficial effects in cancer therapy. Our previous research had showed they can directly trigger death in tumour cells, particularly when the tumour is also attacked by chemotherapeutic drugs. We now think BH3-mimetics could also impact tumour cells indirectly by killing endothelial cells within tumours.

"This suggests that a promising new approach to the therapy of solid tumours may be to use a three-medication combination of a drug that specifically targets the tumour cell, an anti- angiogenic agent to impair the tumour blood vessels, plus a BH3 mimetic that will help the anti- tumour drug to directly kill the tumour cells and also will help the anti-angiogenic agent to kill the intra-tumoral endothelial cells, which in turn will starve the tumour, causing even more tumour cell death."

The research was supported by the Cancer Council Victoria, the National Health and Medical Research Council, the Australian Research Council, the US National Institutes of Health, the Leukemia and Lymphoma Society and Genentech.