Updated May 2nd, 2019

New Evidence About Why Immunotherapy May Not Work For Colorectal And Prostate Cancers

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A new study from researchers at the University of California, San Francisco sheds light on why some cancers respond to immunotherapy and some don’t.

The study focuses on colorectal and prostate cancers, which both seem at this point to be largely untreatable using immunotherapy, one of the most promising areas of cancer research. Immunotherapy drugs block a certain process that cancer tumors use to grow. The tumor sends signals to shut down the immune system, and it uses a very specific protein on the surface of the tumor to do so. Immunotherapy drugs work by targeting that protein, so that it can’t send its signal. But for cancers that don’t have this protein on the surface of their cells, it’s more difficult to get immunotherapies to work.

In the study, researchers found that they could cure a mouse of prostate cancer using immunotherapy drugs if they removed a protein called PD-L1, that the tumor uses. After removing the protein, the immune system was able to properly attack the cancer.

Researchers also observed that if they removed the immune blocking protein and allowed the immune system to work, when they reintroduced the protein, the immune system was still able to attack the tumor. This suggested to researchers that the immune system could be “trained” to attack the tumor, even in the presence of the protein.

The study only looks at mice, researchers said at the time, which means that the results don’t necessarily transfer to human beings, but can provide information for further studies and extended research.

Dr. Brendan Stiles on immunotherapy for lung cancer

When immunotherapy drugs work, the molecule that signals the immune system to shut down is turned off, and the immune system can resume action to fight the cancer.

For example, immunotherapy has been a significant advance for lung cancer, according to Dr. Brendan Stiles, Thoracic Surgeon at Weill Cornell Medicine and NewYork-Presbyterian. “It's amazing to me now that you can have stage four lung cancer and actually not even need chemotherapy,” he tells SurvivorNet. “If you have high expression of a protein that we know is targeted by immunotherapy, you may just get immunotherapy alone.”

Dr. Nina Shah on immunotherapy for multiple myeloma

Immunotherapy can also be an important part of treatment for multiple myeloma. “We now have drugs that use the immune system to make myeloma go away,” Dr. Nina Shah of the University of California at San Francisco Medical Center tells SurvivorNet.

One of the immune system cells that can help fight multiple myeloma is called a “CAR T cell,” and it’s usually responsible for killing viruses and some bacteria. “Unfortunately, for people with cancer– any type– a lot of times, their T cells just don’t function well,” says Dr. Shah. “And so we have to change how the T cells work and reprogram them with new genes so that those T cells are able to find myeloma cells specifically and attack those myeloma cells.”

“These T cells can actually kill myeloma so much so that people who may have had their bone marrow packed with myeloma, actually are able to see the bone marrow clean of myeloma, which really has been so hard to do, even with all the new drugs we have,” Dr. Shah continues.

Car T therapy is not FDA approved at this point, but a lot of people have access to the therapy through clinical trials.

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