Effective immunotherapy i.e. enlisting the patient’s own immune system to fight disease may mark a milestone in the fight against certain cancers. Three lymphocytes – T cells, B cells and NK-cells – involved in specific immune responses against cancers and other diseases. T cells recognize specific antigens via a T-cell antigen-receptor. The two main types of T cells, CD4- and CD8 T-cells, are categorized according to their respective CD4 and CD8 surface markers. The latter group includes cytotoxic T cells, also known as killer T lymphocytes. These cells kill invading pathogens or other disease-causing agents. Scientists discovered that a type of protein receptor, cytotoxic T-Lymphocyte Antigen 4 (CTLA-4), prevented T cells from launching immune attacks . In the early 1990s, another “brake” was discovered in dying T cells namely programmed death 1 or PD-1. The rationale underlying cancer immunotherapy is that exposing CTLA-4, PD-1 or using other appropriate immune-system-based therapies may enable the release of the immune system to destroy cancer.
Genetically engineering a patient’s T cells to target tumor cells marked one of the promising turning points in cancer immunotherapy. A research group from Memorial Sloan Kettering Cancer Center reported last year that T cell therapy ( chimeric antigen therapy [CAR]) in their studies put 45 of 75 adults and children with leukemia into complete remission, although some relapses were occurred at a later date . Researchers from other institutions have reported promising results such as tumor regression with advanced melanoma. The hope, according to Dr. S. Rosenberg, is that CAR T cell therapy may eventually “become the standard of care for B-cell malignancies” like acute lymphoblastic leukemia and chronic lymphocytic leukemia.
For some patients with metastatic disease, cancer immunotherapy may offer a chance, although researchers have yet to figure out why the treatment works in some patients and not in others. In addition, there are side-effects such as the release of signaling proteins regulating interactions between immune cells, also known as cytokines. Cytokine-release syndrome can be mild and therefore treatable or the rapid and massive release of these molecules could lead to declines in blood pressure and debilitating fevers.
Nevertheless, buoyed by promising results, scientists are turning their attention to developing engineered T cells for other cancers, including pancreatic and brain tumors.
1. Couzin-Frankel, J., Breakthrough of the year 2013. Cancer immunotherapy.Science, 2013. 342(6165): p. 1432-3.