Resident Memory T Cells and Their Effect on Cancer

Resident memory T (T_RM) cells are a unique subset of CD8⁺ T cells that are present within certain tissues and do not recirculate through the blood. Long term memory establishment and maintenance are dependent on tissue population of memory T cells. They are characterized by dual CD69/CD103 positivity, and play a role in both response to viral infection and local cancer immunosurveillance. Human T_RM cells demonstrate the increased expression of adhesion molecules to facilitate tissue retention, have reduced proliferation and produce both regulatory and immune responsive cytokines. T_RM cell phenotype is often characterized by a distinct expression profile driven by Runx3, Blimp1, and Hobit transcription factors. The accumulation of T_RM cells in tumors is associated with increased survival and response to immunotherapies, including anti-PD-1 and anti-CTLA-4. In this review, we explore potential mechanisms of T_RM cell transformation and maintenance, as well as potential applications for the use of T_RM cells in both the development of supportive therapies and establishing more accurate prognoses.