Systematic review on PDL-1 exression in human cancer

Abstract

Cancer is a leading cause of death worldwide with devastating mortality and morbidity. They present with myriad and exhaustively variable prodromes and symptoms or syndromic forms. Therapeutic modalities like chemotherapy and radiotherapy target replicative potential and excessive proliferative nature of neoplasms. Of the hallmarks of cancer, evasion of immune response to tumor proliferation is the target for another treatment option – immunotherapy, which has come into prominence over the last decade. Immunotherapy was developed when Dr. James Allison discovered a protein receptor on T cell surface, the cytotoxic T-lymphocyte antigen 4, which was later found to be involved in immunosuppression in cancer. The idea behind immunotherapy was conceived by Dr. Allison when experiments were conducted over decades and proteins were sought that could antagonize CTLA-4 and in theory could overturn the immunosuppressive nature of T cell behavior in a neoplastic background.Immunotherapeutic strategies have evolved to include vaccines, oncolytic viruses, adoptive transfer of ex vivo activated T and natural killer cells, and administration of antibodies or recombinant proteins that stimulate T cells or block the immune checkpoint pathways, the so-called immune checkpoint inhibitors. Examples of immune check point targets include cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD1;CD279) and programmed cell death protein 1 ligand (PDL-1;CD274).