Immune responses - Cancer Science

What is the Role of the Immune System in Cancer?

The immune system plays a critical role in identifying and eliminating abnormal cells, including cancer cells. It comprises various components like T cells, B cells, natural killer (NK) cells, and macrophages, which work together to detect and destroy potentially harmful cells. The immune system can recognize cancer cells through the detection of tumor antigens—proteins or markers on the surface of cancer cells.

How Do Cancer Cells Evade the Immune System?

Cancer cells employ several mechanisms to evade immune detection. One common tactic is the downregulation of Major Histocompatibility Complex (MHC) molecules, which are essential for antigen presentation and T cell recognition. Cancer cells can also secrete immunosuppressive cytokines like TGF-β and IL-10 that inhibit immune responses. Additionally, cancer cells can express immune checkpoint proteins such as PD-L1, which bind to PD-1 receptors on T cells, effectively turning off the immune response.

What is Immunotherapy and How Does It Work?

Immunotherapy is a form of cancer treatment that boosts the body's natural defenses to fight cancer. It encompasses various approaches including checkpoint inhibitors, which block proteins that prevent T cells from attacking cancer cells, and CAR T-cell therapy, which involves modifying a patient's T cells to better recognize and destroy cancer cells. Another form of immunotherapy is cancer vaccines, which aim to stimulate the immune system to target specific cancer antigens.

What are Immune Checkpoint Inhibitors?

Immune checkpoint inhibitors are drugs designed to block checkpoint proteins from binding with their partner proteins. This prevents the "off" signal from being sent, allowing T cells to kill cancer cells. Common checkpoint inhibitors target proteins like PD-1, PD-L1, and CTLA-4. These drugs have shown significant success in treating various types of cancers, including melanoma and lung cancer.

What is the Role of T Cells in Cancer Immunotherapy?

T cells are pivotal in cancer immunotherapy due to their ability to specifically target and kill cancer cells. In therapies like CAR T-cell therapy, T cells are extracted from a patient, genetically engineered to express a receptor specific to cancer antigens, and then reintroduced into the patient's body. These modified T cells can then effectively recognize and destroy cancer cells. Additionally, adoptive cell transfer (ACT) involves the infusion of T cells that are naturally found in the tumor, expanded and activated ex vivo, and then reinfused into the patient.

What are the Side Effects of Immunotherapy?

While immunotherapy can be highly effective, it also comes with potential side effects due to the activation of the immune system. Common side effects include immune-related adverse events (irAEs) such as skin rashes, colitis, hepatitis, and endocrinopathies. These side effects result from the immune system attacking healthy tissue. Management of irAEs often involves the use of immunosuppressive drugs like corticosteroids.

How Effective is Immunotherapy in Treating Cancer?

The effectiveness of immunotherapy varies depending on the type of cancer and the individual patient. Some cancers, like melanoma and certain types of lung cancer, have shown remarkable responses to immunotherapy. However, not all patients respond to these treatments, and research is ongoing to understand the mechanisms of resistance and to identify biomarkers that predict response. Combination therapies, where immunotherapy is used alongside traditional treatments like chemotherapy, are also being explored to enhance efficacy.

What is the Future of Cancer Immunotherapy?

The future of cancer immunotherapy is promising, with ongoing research focused on improving the efficacy and safety of these treatments. Advances in personalized medicine aim to tailor immunotherapy based on the genetic and molecular profile of an individual's tumor. Additionally, the development of bispecific antibodies and oncolytic viruses represents novel strategies to enhance the immune response against cancer. As our understanding of the immune system and cancer biology deepens, the potential for more effective and targeted immunotherapies continues to grow.