The researchers discovered that the cancer-killing action of chemotherapy can trigger a horde of wound-healing, white blood cells that cluster around blood vessels in a treatment-affected tumor. Sometimes these M2 macrophages do too good a job. They repair tissue damage and build new blood vessels, which could help the tumor to grow again after treatment. On the other hand, if the mice with cancer are treated with a drug that stops these repair cells from working, the researchers could scale back the speed at which tumors grew back after chemotherapy.
Professor Claire Lewis at the University of Sheffield’s Department of Oncology, the lead scientist on the study, said, “Scientists already knew that the body’s drive to heal itself can sometimes backfire when the immune system reacts to tissue damage. Our research shows that treating tumors with chemotherapy can activate this part of the immune system, and this then helps tumors re-grow afterwards. But combining chemotherapy with a drug that switches off this part of the body’s repair system, slowed the growth of tumors after chemotherapy. This could be particularly important for patients who can’t have surgery and, therefore, need chemotherapy to help them live for as long as possible.”
The researchers will need clinical trials of patients to confirm that the drug can help cancer patients after chemotherapy. It is already used in patients for other reasons, such as bone marrow transplants -
According to Dr Áine McCarthy, science communications officer at Cancer Research UK, “Chemotherapy is a cornerstone cancer treatment that saves thousands of lives, but sometimes tumors come back, reducing patients’ chances of survival. We don’t understand all the reasons why tumors do come back, but this study sheds new light on the role of the immune system in causing tumors to grow again and, importantly, identifies a drug that could block this happening if given at the same time as chemotherapy. But this is early research carried out in mice and more work is needed to see if blocking M2 macrophages can also slow down tumor re-growth in patients.”