How does immunotherapy work for cancer

Immunotherapy is a type of cancer treatment that helps your body's own immune system fight cancer. Normally, your immune system is designed to recognize and destroy foreign invaders like bacteria and viruses, as well as abnormal cells, including cancer cells. However, cancer cells can sometimes find ways to "hide" from the immune system or "turn off" its attack. Immunotherapy works by boosting your immune system's natural ability to find and destroy these cancer cells.

Standard Medical Guidance

According to the National Cancer Institute (NCI) and the American Cancer Society, there are several main types of immunotherapy:

1. Immune Checkpoint Inhibitors:

   • How they work: Your immune system has "checkpoints" – molecules on immune cells that act like brakes to prevent the immune response from being too strong and damaging healthy cells. Cancer cells can sometimes use these checkpoints to evade detection and destruction by the immune system. Checkpoint inhibitors are drugs that block these brakes, essentially "releasing the brakes" on the immune system so it can better recognize and attack cancer cells.
   • Common checkpoints targeted:
     • PD-1/PD-L1: These pathways are often targeted. PD-1 is a protein on immune cells (T-cells), and PD-L1 is a protein that can be found on cancer cells or other cells in the tumor environment. When PD-1 binds to PD-L1, it tells the T-cell to stand down. Inhibitors block this binding, allowing the T-cells to attack.
     • CTLA-4: This is another checkpoint protein on T-cells that, when activated, also puts the brakes on the immune response. Inhibitors block CTLA-4, allowing T-cells to remain active.
   • Relevance for Prostate Cancer: While checkpoint inhibitors have revolutionized treatment for many cancers, their role in prostate cancer has been more limited. However, for a specific subset of prostate cancers, particularly those with Microsatellite Instability-High (MSI-H) or Mismatch Repair Deficient (dMMR) tumors, checkpoint inhibitors may be considered. These genetic features indicate a higher number of mutations, making the cancer cells more visible to the immune system. The NCCN Guidelines for Prostate Cancer recommend testing for MSI/dMMR in certain advanced prostate cancer settings.

2. Therapeutic Cancer Vaccines:

   • How they work: Unlike vaccines that prevent infections, therapeutic cancer vaccines are designed to treat existing cancer by boosting the immune system's response to cancer cells. They expose the immune system to specific cancer-related antigens (substances that trigger an immune response), teaching it to recognize and attack cells that have these antigens.
   • Relevance for Prostate Cancer: Sipuleucel-T (Provenge) is an FDA-approved therapeutic cancer vaccine specifically for some men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). It works by taking a patient's own immune cells, exposing them to a prostate cancer antigen, and then reinfusing them into the patient to stimulate an immune response against prostate cancer cells.

3. Monoclonal Antibodies:

   • How they work: These are lab-made proteins that can bind to specific targets on cancer cells or immune cells. Some monoclonal antibodies directly target cancer cells for destruction, while others act as immunotherapies by blocking signals that help cancer cells grow or by marking cancer cells for immune attack.

4. Oncolytic Viruses:

   • How they work: These are viruses that have been modified in the lab to infect and kill cancer cells while sparing healthy cells. When the virus infects a cancer cell, it replicates inside it, causing the cell to burst and die. This