We only have one FDA-approved immunotherapy for prostate cancer, Provenge (sipuleucel-T). However, that may be about to change. Research on how to harness the immune system to treat cancer is advancing rapidly on a broad front.
For example, the treatment of hematologic malignancies, such as leukemias, lymphomas, and multiple myelomas, has been revolutionized by the CAR-T technique. This approach involves removing the patient’s T-cells and inserting a gene that causes the T-cell to recognize and attack the cancer of interest. These modified T-cells are then grown in large numbers in the lab and infused back into the patient, where they, hopefully, attack the patient’s cancer. While this approach has been established in the treatment of hematologic malignancies, carcinomas, such as prostate cancer, have proved to be more difficult to target. As you will read about later in this issue, early results suggest we may finally have a promising CAR T treatment for prostate cancer.
Antibodies’ role in the immune system is to specifically bind to proteins that are present on an invading infectious organism. This can then interfere with the function of that protein. Alternatively, antibody binding can target the invading organism for destruction. An example very much in the news is the neutralizing antibodies binding to the spike protein of the COVID-19 virus. The ability of antibodies to bind to targets with great specificity has been used in innovative ways. In this issue you will read about antibodies linked to radioactive isotopes to image or destroy cancer cells. Another approach is to create molecules that can link to a T cell at one end and the cancer cell at the other end, with the hope that bringing these two cells into proximity will cause the immune cell to attack the cancer cell.
Even when T cell manage to invade a mass of prostate cancer cells, the environment within the cancer mass tends to inactivate these immune cells. Progress in identifying the mechanisms by which the cancer inactivates the immune cells is discussed along with various strategies to reverse the inactivation.
Charles E. Myers, Jr., MD