The immune system has the intrinsic power to detect and eliminate abnormal cells, such as those derived from tumors. This process, commonly referred to as immune surveillance, takes advantage of numerous biological features that distinguish tumor cells from their normal counterparts. For example, tumor cells display aberrant functional behaviors and an altered surface antigen composition, typically resulting from a myriad of genetic and epigenetic changes. Abnormal cytokine and growth factor expression patterns are also common hallmarks of certain types of cancer, eliciting to either support growth or counteract local inflammation, particularly during cellular invasion and metastasis. With more advanced diseases, tumor cells eventually develop active mechanisms to escape immune surveillance and induce tolerance. There is ample evidence that B cell-driven antibody responses can trigger autologous tumor regression in animals and humans.
Immunotherapy has become an increasingly important part of treating human grievous diseases including some types of cancer. Immunotherapy is the treatment of human disease by modulating an immune response. Immunotherapies designed to induce or enhance an immune response are classified as activation immunotherapies, while immunotherapies that reduce or suppress are classified as suppression immunotherapies. Cancer immunotherapy usually stimulates the immune system to reject and destroy tumors. The active agents of immunotherapy are collectively known as immunomodulators, such as cytokines. The main types of immunotherapy now being used to treat cancer include:
- Monoclonal antibodies (mAbs)
- Immune checkpoint inhibitors
- Cancer vaccines
- Oncolytic viruses
- Cell-based immunotherapies
- Other non-specific immunotherapies
Cell-based immunotherapies are proven to be effective for some cancers. Immune effector cells such as lymphocytes, macrophages, dendritic cells, natural killer cells, cytotoxic T lymphocytes, work together to defend the body against cancer. Adoptive cell transfer uses T cell-based cytotoxic responses to attack cancer cells. In principle T cells that have a natural or genetically engineered reactivity to a patient’s cancer cells are generated in vitro and then transferred back into the cancer patient. For example, genetically engineered T cells are created by infecting patient’s cells with a virus expressing a T cell receptor (TCR) gene or chimeric antigen receptor (CAR) that recognize a specific tumor antigen. The use of adoptive cell transfer with genetically engineered T cells is a promising new approach to the treatment of several types of cancers.