MYST1/KAT8 contributes to tumor progression by activating EGFR signaling in glioblastoma cells

With short survival time, glioblastoma (GBM) is the most malignant tumor in the central nervous system. Recently, epigenetic enzymes play essential roles in the regulation of tumorigenesis and cancer development of GBM. However, little is known about MYST1/KAT8/MOF, a histone acetylation enzyme, in GBM. The present study shows that MYST1 promotes GBM progression through activating epidermal growth factor receptor (EGFR) signaling. MYST1 expression was increased in GBM and was negatively correlated with prognosis in patients with glioma and GBM. Knockdown of MYST1 reduced cell proliferation and BrdU incorporation in LN229, U87, and A172 GBM cells. Besides, MYST1 downregulation also induced cell cycle arrest at G2M phase, as well as the reduced expression of CDK1, Cyclin A, Cyclin B1, and increased expression of p21^CIP1/Waf1. Meanwhile, Self‐renewal capability in vitro and tumorigenecity in vivo were also impaired after MYST1 knockdown. Importantly, MYST1 expression was lowly expressed in mesenchymal subtype of GBM and was positively correlated with EGFR expression in a cohort from The Cancer Genome Atlas. Western blot subsequently confirmed that phosphorylation and activation of p‐Try1068 of EGFR, p‐Ser473 of AKT and p‐Thr202/Tyr204 of Erk1/2 were also decreased by MYST1 knockdown. Consistent with the results above, overexpression of MYST1 promoted GBM growth and activated EGFR signaling in vitro and in vivo. In addition, erlotinib, a US Food and Drug Administration approved cancer drug which targets EGFR, was able to rescue MYST1‐promoted cell proliferation and EGFR signaling pathway. Furthermore, the transcription of EGF, an EFGR ligand, was shown to be positively regulated by MYST1 possibly via H4K16 acetylation. Our findings elucidate MYST1 as a tumor promoter in GBM and an EGFR activator, and may be a potential drug target for GBM treatment.

Histone post-translational modifications regulate autophagy flux and outcome

Autophagy is an evolutionarily conserved process in eukaryotes by which cytoplasmic components including macromolecules and organelles are degraded by the lysosome/vacuole. Autophagy is implicated in a number of physiological processes important for human health and disease. Although primarily cytoprotective, autophagy can also contribute to cell death; it is thus important to understand what distinguishes the life or death decision in autophagic cells. Despite the fact that the execution of autophagy includes a unique set of cytoplasmic events, nuclear events, in particular transcriptional programs, have emerged as an important regulator of this process. In addition, a critical linkage was recently unveiled between specific histone posttranslational modifications and the transcriptional regulation of autophagy-related genes, which initiates a regulatory feedback loop, and serves as a key determinant of survival versus death responses upon autophagy induction.