ABSTRACT
Colorectal cancer (CRC) is one of the most frequently encountered neoplasms and has a high rate of morbidity and mortality. Recent findings showing that tumor immune evasion is an important mechanism underlying propagation of a cancer have changed the landscape of medical oncology through identification of ProgrammedDeath receptor 1 and its ligand (PD1 and PDL1) as novel targets for oncological immune therapies. PD1 is primarily expressed on peritumoral lymphocytes and when activated, it suppresses its immune functions. Conversely, PDL1 is primarily expressed on the tumor infiltrating front with the purpose of deregulating physiological cytotoxic immune responses. Numerous studies have linked PDL1 overexpression to specific adverse clinicopathological features, such as poor differentiation, lymphovascular invasion and worse overall survival in CRC patients. Nevertheless, there is no concrete evidence showing which patients may exhibit the maximal beneficial effects of PD1/PDL1 blockade therapy, and how these novel molecular targets may be optimally integrated into therapeutic regimens for management of CRC patients with resectable and generalized disease.