Immunotherapy can destroy majority of dormant cancer cells

Scientists have found that immunotherapy can destroy majority of dormant cancer cells that become resistant to chemotherapy and combining the two treatments may help prevent cancer recurrence. 

Researchers found that chemotherapy alone leads to two types of dormant cancer cells that are not killed outright and become resistant to additional chemotherapy, but when combined with immunotherapy, a majority of dormant cells also are destroyed.

"The best way to apply immunotherapy as cancer prevention is during tumour dormancy to prevent advanced stage disease," said Masoud H Manjili, a researcher from the Virginia Commonwealth University School of Medicine in the US.

To make this discovery, researchers treated breast cancer cells with a common chemotherapeutic agent. Nearly all of the cancer cells died as a result, but a residual population of tumour cells survived and became dormant. By measuring for the presence of a molecule associated with cell division, the scientists determined that this residual population of dormant cancer cells consisted of an indolent as well as a quiescent population. 

They treated the dormant cells with a product of the immune system, and found that dormant cells were susceptible to immunotherapy. They found that quiescent, but not indolent cancer cells, could not escape from immunotherapy.

"This new study demonstrates the importance of this concept of exploiting the immune system in cancer to target residual disease that our cancer drugs miss," said E John Wherry from University of Pennsylvania. The research appears in the Journal of Leukocyte Biology.