Chemo creates Leaky Blood Vessels helping Cancer Cells to Spread

A new study adds to the evidence that chemotherapy enhances cancer’s spread beyond the primary tumor, showing how one chemo drug allows breast cancer cells to squeeze through and attach to blood vessel linings in the lungs.

The research in mice leaves no doubt that the chemo drug caused changes to non-cancer cells that enable this process. Scientists pre-treated healthy mice with the chemotherapy agent and gave them intravenous injections of breast cancer cells four days later.

Within three hours of injection, the cancer cells were penetrating weakened junctions between blood vessel cells in the lungs and binding to those vessels’ underlining structure – avoiding being washed away by blood flow.

“This is the key step giving cancer cells a foot in the door at a secondary site,” said Tsonwin Hai, professor of biological chemistry and pharmacology at The Ohio State University and senior author of the study. “The whole point of our pre-treatment model is to ask the question: Does chemotherapy affect normal cells in such a way that they will turn around and help cancer cells? The answer is yes.

“It’s a cautionary note for the use of chemotherapy.”

The study was published online recently in the International Journal of Molecular Sciences.

Hai has studied the underpinnings of cancer metastasis for years, previously finding that activation of a specific gene in immune cells is a crucial link between stress and cancer’s spread and that the chemo drug paclitaxel sets off molecular changes in immune cells that allow breast cancer cells to escape from a tumor.

This new study zeroed in on the effects of the chemo drug cyclophosphamide on non-cancer cells before there is any cancer present, focusing on the lungs as the site of metastasis.


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