Combination of Chemotherapy and Immunotherapy Shows Promise in Prostate Cancer

Treating immune-suppressing cells allows for destruction of tumors.

Treating immune-suppressing cells allows for destruction of tumors.

A combination therapy for larger prostate tumors achieved remission of the disease in mice during a recent study.

While chemotherapy can be highly effective against smaller prostate tumors, larger tumors accumulate immune-suppressing cells that allow cancer cells to continue growing. A study published recently in Nature found that blocking immune-suppressing cells permits a type of chemotherapy that activates immune cells to eradicate prostate tumors.

The experimental combination therapy, called chemoimmunotherapy, caused near complete remission in mouse models of advanced prostate cancer, which does not typically respond to chemotherapy. Prostate cancer also does not respond to checkpoint inhibitors, which are a promising new type of immunotherapy drugs.

These drugs disable the cloaking mechanism of cancer cells so the immune system can better fight the disease. The resistance is thought to be due in part to immunosuppressive B cells, which causes most therapies to be ineffective and allows malignant tumors to grow.

For the study, researchers used 3 different mouse models of advanced prostate cancer, all of which were resistant to low doses of oxaliplatin, which is able to activate cancer-killing immune cells. However, when researchers blocked the development or function of immunosuppressive B cells before administering low-dose oxaliplatin, the tumors were almost completely eradicated by the mice's immune cells.

Similar results were found when low-dose oxaliplatin was combined with a checkpoint inhibitor.

"The presence of such B cells in human prostate cancer calls for clinical testing of this novel therapeutic approach," first author Shabnam Shalapour, PhD, said in a press release.