Study Helps Resolve Debate About How Tumors Spread

A team of scientists, led by researchers at the University of California, San Diego School of Medicine, has shown for the first time how cancer cells control the ON/OFF switch of a program used by developing embryos to effectively metastasize in vivo, breaking free and spreading to other parts of the body, where they can proliferate and grow into secondary tumors. The findings are published in the December 11 issue of the journal Cancer Cell . In 90 percent of cancer deaths, it is the spreading of cancer, known as metastasis, which ultimately kills the patient by impacting ever-more tissues and functions until the body fails. Ten years ago, a French cancer researcher named Jean Paul Thiery hypothesized that tumor cells metastasized by exploiting a developmental process known as epithelial-to-mesenchymal transition or EMT. EMT is seen in developing embryos whose cells transform from stationary epithelial cells into more mobile mesenchymal cells, the latter able to migrate to new locations and create new types of tissue and organs. Thiery proposed that cancer cells also switch "ON" EMT, temporarily changing attributes so that they can detach from primary tumors, enter the bloodstream and seed new tumors elsewhere. After arriving at a new location, the cancer cells then turn "OFF" the EMT program and grow into carcinoma metastases or tumors.