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Surprising discovery identifies new approach to suppress spread of cancer

December 20, 2012

Scientists at Mount Sinai's Samuel Lunenfeld Research Institute have made a major discovery about the way that cancer spreads. In a study published today in the journal Cell, Valbona Luga and Dr. Liang Zhang discovered that proteins produced in normal cells near the environment of a cancer tumour influences the cancer's ability to spread to other tissues of the body, a process called metastasis. The researchers work in the lab of Mount Sinai's Dr. Jeff Wrana, an international leader in cancer research. 
One of the impacts of the study is the ability to target one of the proteins, called Cd81, to halt the spread of breast cancer and other cancers. The newly identified protein is part of tiny fragments of cells called exosomes. In a cancer state, the tumour cell releases exosomes to influence neighbouring cells. The researchers discovered that normal cells surrounding the tumour also secrete exosomes which help the tumour cells to spread.
 "We wanted to find out how these different cells are communicating – from tumour cells to normal cells, and vice versa," says Dr. Jeff Wrana. "Classically, scientists have believed that communication between cells occurs in a simple fashion, that is, one signal (one word) back and forth. We found, to our disbelief, that these cells are exchanging whole paragraphs of information."
 "Instead of only targeting the primary tumour, we can now pinpoint the cells in the tumour's environment that are responding to the tumour and target those too," says Valbona Luga. "We hope to use our new knowledge of the tumour's immediate surroundings to intercept its signals to cancer cells, and by doing so, drastically impede tumour spreading."
When exosomes were initially discovered in the 1980s, they were classified as little more than cell waste. In the 1990s, scientists linked their role to the healthy function of the immune system. Now, the Lunenfeld team has provided compelling evidence that exosomes are linked to cancer metastasis, and identified important proteins and molecules in normal cells and cancer cells that can be targeted to halt cancer's spread.

Funded by the Terry Fox Research Institute and CIHR (Canadian Institutes of Health Research), for this particular study Lunenfeld scientists also collaborated with Dr. Alicia Viloria-Petit from the Department of Biomedical Sciences at the University of Guelph and Dr. Mark Basik from the Lady Davis Institute for Medical Research at Jewish General Hospital in Montreal.

In this video from the research team, breast cancer cells are being stimulated by exosomes, which are tiny cell fragments produced by 'normal' cells. The breast cancer cells display an incredible rate of motility, one of the attributes for metastatic spread. The frames in this video have been captured over a period of 19 hours.

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