A process that normally occurs in developing embryos the changing of one basic cell type into another has also been suspected of playing a role in cancer metastasis. Now a study from Massachusetts General Hospital (MGH) Cancer Center researchers has associated this process, called epithelial-mesenchymal transition or EMT, with disease progression and treatment response in breast cancer patients. The report also identifies underlying mechanisms that someday may become therapeutic targets.
"Until now, EMT had only been modeled in experimental systems, but its clinical relevance was uncertain. Now we show that it can be detected in samples from breast cancer patients and that the tumor cells oscillate between these two states" says Shyamala Maheswaran, PhD, of the MGH Cancer Center, co-corresponding author of the report in the Feb. 1 issue of Science. "We find that the EMT state of breast cancer cells evolves in response to therapy and to disease recurrence, pointing to involvement of this mechanism in tumor spread and invasiveness."
Epithelial tissues line most bodily surfaces and cavities, and epithelial cells closely adhere to each other. During development, some epithelial cells develop traits of mesenchymal cells, including the ability to migrate to other parts of the embryo, establish themselves and develop into organs or other types of tissue. Several studies have suggested that a transition from epithelial to mesenchymal cell type is also involved with cancer metastasis, which involves tumor cells' migration to and invasion of other sites in the body, but identifying EMT stages of tissues has been challenging.
The MGH investigators developed a new assay that determines EMT stage by screening tumor samples for seven epithelial markers and three mesenchymal markers. In primary tumor samples from several breast cancer patients including samples of estrogen-receptor/progesterone-receptor-positive, HER2-positive
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Massachusetts General Hospital