Immune Therapy: Chemical Shows Promise as New Cancer-Killing Weapon

Charles Drake, M.D., Ph.D., wasn’t too impressed with a particular kind of chemical, called IL-17, made by immune cells in the prostate. His lab had been studying it, and IL-17, a cytokine made by immune cells called lymphocytes, didn’t seem like much of a fighter; it couldn’t kill target cells in specially designed assays. Nonetheless, “we wanted to test what these cells did in the body,” says Drake, the Nancy and Jim O’Neal Scholar. So, in difficult, time-consuming work, they made up a batch of IL-17- secreting lymphocytes, put them into animals — and were amazed at the results.

“To our surprise, we found that immune cells that make IL-17 are more active than other immune cells,” says Drake. “They seem to move more widely throughout the body, and to do a better job of killing their targets.” Like any good warrior, these IL-17- making cells also turned out to be adept at more than one weapon. “We found that these cells could change after seeing their targets – although they originally made IL-17, they could switch to making another cytokine known as interferon gamma. This is very important, since the production of interferon gamma is associated with the ability of these cells to kill.”

Just a small dose of these IL-17-secreting cells has proven enough to delay significantly the growth of tumors in mice. In other studies, when these cells were targeted at specific proteins, they attacked them with gusto, and just a few were able to produce a significant effect. “We suspect that these results will carry over to prostate cancer,” notes Drake. Next, his lab will see whether IL-producing lymphocytes can actually stop the growth of prostate cancer in mice.

What Drake really wants to know now is whether IL-17-producing cells already exist in the prostates of men with cancer. He plans to look for them in surgical specimens of men who have undergone radical prostatectomy. And if he finds them, “then it might be possible to specifically boost this population of IL-17 secreting lymphocytes,” with the goal of creating a more powerful immune response to prostate cancer. And if he can do this, he believes, one day it may be possible “to help men with the disease live longer without the side effects of hormonal or chemotherapy.”

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