Scientists at Toronto’s Mount Sinai Samuel Lunenfeld Research Institute have made a major discovery about the way that cancer spreads.  In the paper Exosomes Mediate Stromal Mobilization of Autocrine Wnt-PCP Signaling in Breast Cancer Cell Migration, published in Cell, Valbona Luga and Dr. Liang Zhang discovered that proteins produced in normal cells near the environment of a cancer tumor 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 tumor cell releases exosomes to influence neighboring cells. The researchers discovered that normal cells surrounding the tumor also secrete exosomes which help the tumor cells to spread.

“We wanted to find out how these different cells are communicating – from tumor 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 tumor, we can now pinpoint the cells in the tumor environment that are responding to the tumor and target those too,” says Valbona Luga. “We hope to use our new knowledge of the tumor immediate surroundings to intercept its signals to cancer cells, and by doing so, drastically impede tumor 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.

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