London: In a discovery that could lead to new treatments to prevent relapse of cancer, scientists have claimed to have uncovered how a small number of cancer cells escape from chemotherapy by hiding in a protective shield.
In a study of mice, biologists at the Massachusetts Institute of Technology (MIT) in Cambridge found that a few cancer cells hide inside the thymus -- an organ where immune cells mature -- and escape the treatment.
While hiding there, they are bathed in growth factors that protect them from the drugs` effects. Those cells are likely the source of relapsed tumours, said Michael Hemann, MIT assistant professor of biology, who led the study.
The researchers plan to soon begin tests, in mice, of drugs that interfere with one of those protective factors. Those drugs were originally developed to treat arthritis, and are now in clinical trials for that use.
According to the scientists, such a drug, when used in combination with traditional chemotherapy, can offer a one-two punch to eliminate residual cells and prevent cancer relapse.
"Successful cancer therapy needs to involve a component that kills tumour cells as well as a component that blocks pro-survival signals," said Hemann. "Current cancer therapies fail to target this survival response."
In the new study, published in the journal Cell, the researchers treated mice with lymphoma with doxorubicin, a drug commonly used to treat a wide range of cancers, including blood cancers. They found that during treatment, cells that line the blood vessels release cytokines -- proteins that influence immune responses and cell development.
The exact mechanism is not known, but the researchers believe that chemotherapy induced DNA damage provokes those blood-vessel cells to launch a stress response that is normally intended to protect progenitor cells – immature cells that can become different types of blood cells.
That stress response includes the release of cytokines such as interleukin-6, which promotes cell survival.
"In response to environmental stress, the hardwired response is to protect privileged cells in that area, that is progenitor cells," said Hemann. "These pathways are being coopted by tumor cells, in response to the frontline cancer therapies that we use."