Cisplatin disrupts OCT1-DNMT1-piRNA epigenetic regulatory axis to suppress GAB2-mediated aggressiveness in OSCC.

Chemotherapy-induced ncRNA-mediated plasticity is an emerging concept in cancer research. To that end, we observed a cisplatin-responsive regulatory program centered on piRNA activation. OSCC cells exposed to cisplatin markedly promoted the piRNA expression, with piR-hsa-30937 showing the most prominent upregulation. Mechanistically, cisplatin disrupts the OCT1-DNMT1 repressive complex that mediates DNA methylation of transcription factor binding sites of piR-hsa-30937, to derepress its expression. Functionally, piR-hsa-30937 targets GAB2 and sensitizes OSCC cells to cisplatin by suppressing proliferation, enhancing apoptosis, and γ-H2AX accumulation. Furthermore, GAB2 overexpression reversed these effects and desensitized OSCC cells to cisplatin by activating NF-κB-mediated JNK suppression. Overall, cisplatin actively remodels the OCT1-DNMT1-piR-hsa-30937 axis regulating piRNA expression, which in turn potentiates cisplatin cytotoxicity by attenuating GAB2-mediated survival signaling in OSCC.