The limited and inconsistent efficacy of existing therapies for tuberous sclerosis complex (TSC) has driven the exploration of novel strategies, including epigenetic regulation. GSK-J4, an inducer of global H3K27me3 accumulation, shows broad anti-tumor activity. However, its therapeutic potential in TSC remains unclear. In the study, we reported that GSK-J4 inhibited cell cycle progression and induced apoptosis in primary Tsc1+/− and Tsc2+/− MEFs. Mechanistically, Tsc1 or Tsc2 deletion reduced global H3K27me3, correlating with increased viability, accelerated cell cycle, and suppressed apoptosis-phenotypes reversed by GSK-J4. Moreover, GSK-J4 triggered endoplasmic reticulum stress (ERS) by activating the PERK-ATF4-CHOP axis, which concurrently downregulated the proto-oncogene c-Myc, outlining a GSK-J4→p-PERK→c-Myc inhibitory pathway. Notably, GSK-J4 synergized with rapamycin to enhance cell cycle arrest and apoptosis. In vivo, this combination alleviated renal impairment in Tsc1- or Tsc2-deficient models, suggesting a promising therapeutic strategy for TSC patients with suboptimal response to mammalian target of rapamycin complex 1 (mTORC1) inhibitors. Our study elucidates a specific ERS-dependent anti-tumor mechanism of GSK-J4 in Tsc-deficient contexts and demonstrates the synergistic efficacy of combining epigenetic and mTORC1 inhibitors.
Lei et al. (Fri,) studied this question.