The activation of endogenous IFNγ signaling pathway or the administration of recombinant IFNγ increases the expression of MHC-I. MHC-I molecules are core elements for antigen recognition in tumor cells. A better understanding of the regulation of their expression would contribute to counteracting tumor immune escape and enduring permanent tumor rejection. Efficient and functional expression of HLAs dramatically impacts the number of tumor-associated antigens presented to CTL for cell recognition. Many patients diagnosed with various types of cancer have inhibited the IFNγ signaling pathway. This review explores how anomalies associated with IFNγ signaling in tumor cells affect HLA-I expression, current immunotherapies association, and outcome. Globally, MHC-I lesions could be divided into reversible and permanent. Irreversible lesions cannot be recapitulated; hence, the patient will not respond to immunotherapies requiring MHC-I activity. However, gaining precise and systematic molecular knowledge improves tumor stratification, which could help predict which tumors will recover expression of MHC-I. Complementary IFNγ effectors can function as a compensatory mechanism that restores the expression of HLA-I proteins in tumors with deleterious IFNγ pathways. For those non-responsive patients with inactive IFNγ pathways, designing personalized approaches to recover HLA-I expression can make the tumor sensitive to immunotherapy, leading to a better outcome.
MHC class I, HLA, IFNγ, Immunotherapy