Prevention of cancer initiation by augmenting MHC-I antigen presentation via EZH2 inhibition

Early intervention of precancers is significant for improving cancer outcome. EZH2-mediated epigenetic modification was responsible for the immune escape of cancers; besides, tumor immune evasion is correlated with the impaired MHC-I antigen presentation machinery (APM). Oral potentially malignant disorders (OPMDs), represented by oral leukoplakia (OLK), usually precede head and neck squamous cell carcinoma (HNSCC). EZH2 is correlated with malignant transformation (MT) of OPMDs including OLK, while it remains undetermined that whether EZH2 mediates the initiation of HNSCC by repressing APM. Herein, EZH2 was first reported to negatively correlate with MHC-I and CD8+ GZMB+ T subsets which promote antitumor immunity in OPMDs. In vitro study uncovered that EZH2 triggers H3K27me3 on the promoters of MHC-I associated genes such as HLA-A/B/C, B2M and TAP1. Next, we constructed one hydrogel loaded with GSK126, a specific EZH2 inhibitor, denoted as PPT@GSK126 which is well-tolerated and highly adhesive to mucosa. Preclinical trials demonstrated that topical PPT@GSK126 could significantly prevent the MT of OPMDs and induce robust specific immune killing of dysplastic cells; while individual local αPD-1 therapy was unavailable, PPT@GSK126 synergized with topical αPD-1 therapy to significantly repress the cancerization of OPMDs. As EZH2 is highly expressed in numerous precancers, PPT@GSK126 has broad application prospects for reducing these tumor burdens. Schematic images presenting the mechanism of action regarding EZH2 in promoting MT of OLK into HNSCC via inhibiting MHC-I associated APM (left panel) and the proposed therapeutic strategy for preventing OLK carcinogenesis (right panel).