Novel Detection Method Unmasks Circulating Breast Cancer Cells

Circulating metastatic breast cancer cells can lose their epithelial receptors, a process that enables them to travel through the bloodstream undetected, according to research from The University of Texas M. D. Anderson Cancer Center.

The findings were presented at the CTRC-AACR San Antonio Breast Cancer Symposium.

Levels of these circulating tumor cells (CTCs) - which are shed from a primary tumor or its metastases - have been used to monitor and tailor cancer therapy and to predict a patient's prognosis. CTCs that have undergone epithelial-mesenchymal transition (EMT), however, evade current detection methods and lose their traditional prognostic and therapeutic value. Those cancer cells also become more resistant to chemotherapy and radiation therapy. Finding a reliable method to detect these stealth breast cancer cells may reveal additional therapeutic targets that could help eradicate micrometastatic disease in patients with breast cancer or other epithelial tumors.

EMT and the Invasion-Metastasis Cascade

EMT is a process in which cancer cells undergo transdifferentiation (transformation into a different type of cell). "The carcinoma cells activate a transdifferentiation program in order to acquire the ability to execute the multiple steps necessary for the invasion-metastasis cascade," said the study's first author Michal Mego, M.D., Ph.D., formerly a fellow at M. D. Anderson. "During EMT, epithelial cells acquire a mesenchymal appearance with increased motility and invasiveness."

The researchers hypothesized that these changes render the EMT-CTCs undetectable by current detection assays, such as CellSearch (Veridex). The cells' acquired resistance to chemotherapy and radiotherapy also suggested that EMT-CTCs are tumor-initiating cells and are responsible for tumor dissemination. Moreover, the researchers had found subgroups of high-risk patients with brain metastases, triple receptor-negative disease, or inflammatory breast cancer whose blood tests did not reveal elevated levels of CTCs, further supporting their hypothesis.

Detecting CTCs Through EMT Gene Expression

The researchers then set out to develop a detection method that could identify EMT-CTCs in the peripheral blood of breast cancer patients. They took approximately 5 mL of peripheral blood from 27 patients ranging in age from 34 - 72 years, with a median age of 54. Sixteen of the women had metastatic disease, 19 had inflammatory breast cancer, and 12 had primary, non-inflammatory breast cancer.

"Using magnetic beads coated with monoclonal antibodies capable of capturing the majority of hematopoietic cells in peripheral blood, we obtained a fraction of cells enriched for CTCs," said Mego, who is now a scientist at the National Cancer Institute in the Slovak Republic. "Next we isolated RNA from these cells to detect genes that are involved in epithelial-mesenchymal transition, using molecular biology technology, such as the polymerase chain reaction."

Five EMT genes were identified: TWIST1, SNAIL1, SLUG, ZEB1, and FOXC2. At least one of these genes was over-expressed in 21 percent of the patients. Over-expression of EMT genes was more common among women with triple receptor-negative breast cancer than among those without this high-risk signature. The researchers found no correlation between EMT gene expression and CTC count as measured by CellSearch or the carcinoma-associated antigen known as Ep-CAM (epithelial cell adhesion molecule).

"We found that current CTC detection methods underestimate the most important subpopulation of CTCs involved in tumor dissemination-those with tumor-initiating properties," said James Reuben, Ph.D., professor in M. D. Anderson's Department of Hematopathology, the study's senior author. "A novel detection method such as ours that is capable of detecting CTCs after EMT could add important new prognostic information and could be useful for monitoring treatment efficacy in real time."

The M. D. Anderson and the Slovak National Cancer Institute teams have initiated a confirmatory study among patients with metastatic breast cancer, prostate cancer, or colon cancer. They also have initiated studies designed to identify therapeutic targets on EMT-CTCs. In addition to Mego and Reuben, other authors on the M. D. Anderson study include: Massimo Cristofanilli, M.D., Eleni Andreopoulou, M.D., and Summer Jackson, all of the Department of Breast Medical Oncology; Hui Gao, Ph.D. Changping Li, M.D., Sanda Tin, M.D. and Evan Cohen, all of the Department of Hematopathology; and Sendurai Mani, Ph.D., Department of Molecular Pathology.

About M. D. Anderson

The University of Texas M. D. Anderson Cancer Center in Houston ranks as one of the world's most respected centers focused on cancer patient care, research, education and prevention. M. D. Anderson is one of only 40 comprehensive cancer centers designated by the National Cancer Institute. For six of the past eight years, including 2009, M. D. Anderson has ranked No. 1 in cancer care in "America's Best Hospitals," a survey published annually in U.S. News & World Report.

Source: University of Texas M. D. Anderson Cancer Center

Those extra helpings of gravy and dessert at the holiday table are even less of a help to your waistline than previously thought. According to a new research report recently appearing online in The FASEB Journal, a diet that is high in fat and in sugar actually switches on genes that ultimately cause our bodies to store too much fat.

This means these foods hit you with a double-whammy as the already difficult task of converting high-fat and high-sugar foods to energy is made even harder because these foods also turn our bodies into "supersized fat-storing" machines.

In the research report, scientists show that foods high in fat and sugar stimulate a known opioid receptor, called the kappa opioid receptor, which plays a role in fat metabolism. When this receptor is stimulated, it causes our bodies to hold on to far more fat than our bodies would do otherwise.

According to Traci Ann Czyzyk-Morgan, one of the researchers involved in the work, "the data presented here support the hypothesis that overactivation of kappa opioid receptors contribute to the development of obesity specifically during prolonged consumption of high-fat, calorically dense diets."

To make this discovery, Czyzyk-Morgan and her colleagues conducted tests in two groups of mice. One group had the kappa opioid receptor genetically deactivated ("knocked out") and the other group was normal. Both groups were given a high fat, high sucrose, energy dense diet for 16 weeks. While the control group of mice gained significant weight and fat mass on this diet, the mice with the deactivated receptor remained lean. In addition to having reduced fat stores, the mice with the deactivated receptor also showed a reduced ability to store incoming nutrients.

Although more work is necessary to examine what the exact effects would be in humans, this research may help address the growing obesity problem worldwide in both the short-term and long-term. Most immediately, this research provides more proof that high-fat and high-sugar diets should be avoided. In the long-term, however, this research is even more significant, as it provides a new drug target for developing therapies for preventing obesity and helping obese people slim down.

"In times when food was scarce and starvation an ever-present threat, an adaptation that allows our bodies to store as much energy as possible during plentiful times was probably a lifesaver," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "By taking that opioid receptor off the table, researchers may have found a way to keep us from eating ourselves to death."

Journal Reference:

1. Traci A. Czyzyk, Ruben Nogueiras, John F. Lockwood, Jamie H. McKinzie, Tamer Coskun, John E. Pintar, Craig Hammond, Matthias H. Tschöp, and Michael A. Statnick. κ-Opioid receptors control the metabolic response to a high-energy diet in mice. The FASEB Journal, 2009; DOI: 10.1096/fj.09-143610