Prostate Cancer Combination Treatment Could Beat Disease at Its Own Game: Early Study

When prostate cancer advances to the point of spreading, the larger and more stubborn tumors develop cells that suppress the body’s immune response – and defeat doctors’ attempts to launch an attack on it, experts said.

But through chemoimmunotherapy, a chemical one-two punch, a team of doctors said they are now having new success in mouse models. By first stripping the tumors of hijacked immunosuppressive B cells, and then using drugs to arm the immune system, researchers at the University of California – San Diego were able to nearly eradicate the tumors, they said.

“The presence of such B cells in human prostate cancer calls for clinical testing of this novel therapeutic approach,” said Shabnam Shalapour, the postdoctoral researcher who was the first author of the study.

Prostate cancer, if caught early, can be treated successfully. But once it develops to the point of metastasizing, it becomes significantly more deadly. If it spreads to the bone, the five-year survival rates plummet.

In the mouse models, the prostate tumors were all immune to oxaliplatin, which activates the immune system’s response to fight the cancerous cells. But when researchers blocked the development of the immunosuppressive B cells which were allowing the cancer to cloak itself, the tumors were attacked successfully, they said.

The UC – San Diego researchers said a similar two-pronged attack could prove successful with other types of cancer.

“In addition to prostate cancer, similar immunosuppressive B cells can be detected in other human cancers,” said Michael Karin, the school’s Distinguished Professor of Pharmacology and Pathology. “This indicates that B cell-mediated immunosuppression might be the reason several other cancers are also unresponsive to checkpoint inhibitors, raising the hope that chemoimmunotherapy will have broader applications for many cancer types.”

Prostate cancer is the second-deadliest cancer in American men. Some 1 in 7 will be diagnosed in their lifetime, and 1 in 38 overall will die of it. Some 27,540 died of the disease in 2015, according to the American Cancer Society.