Suberoylanilide hydroxamic acid upregulates reticulophagy receptor expression and promotes cell death in hepatocellular carcinoma cells

ARTICLE HIGHLIGHTS

Research background

Suberoylanilide hydroxamic acid (SAHA) has been demonstrated to trigger multiple forms of cell death in hepatocellular carcinoma (HCC). Family with sequence similarity 134 member B (FAM134B), a reticulophagy receptor, has been recognized as a cancer suppressor protein in multiple tumors, including HCC. However, few researchers have focused on the relationship between reticulophagy and SAHA-induced HCC cell death.

Research motivation

Reticulophagy is involved in a variety of human cancer pathologies. However, its specific function in the modulation of SAHA-initiated HCC cell death remains unproven.

Research objectives

To validate the potential regulatory mechanisms of the FAM134B-mediated reticulophagy in SAHA-induced HCC cell death.

Research methods

The proliferation, apoptosis, and cell cycle of SAHA-treated Huh7 and MHCC97L cells were quantified using cell counting kit-8 and flow cytometry. The migration and invasion of Huh7 and MHCC97L cells were measured using the transwell assay. Proteins related to the reticulophagy pathway, mitochondria-endoplasmic reticulum contact sites, intrinsic mitochondrial apoptosis, and histone H4K16 acetylation were detected using western blotting. ER and lysosome co-localization, and mitochondrial Ca²⁺ levels were observed via confocal microscopy. Autophagy-mediated cell death was validated through Hoechst33342 staining and propidium iodide colocalization. The enrichment of histone H4 lysine 16 acetylation in the FAM134B promoter region was determined using chromatin immunoprecipitation.

Research results

SAHA treatment augmented the expression of proteins related to the reticulophagy pathway and enhanced the level of reticulophagy in HCC cells. Chromatin immunoprecipitation experiments confirmed that SAHA regulated FAM134B expression by increasing the histone H4 lysine 16 acetylation in the FAM134B promoter region. SAHA interfered with Ca²⁺ homeostasis in HCC cells and upregulated the expression of autocrine motility factor receptor-related and mitochondria-endoplasmic reticulum contact sites-related proteins. Furthermore, SAHA reduced mitochondrial membrane potential and aggravated the activation of the reticulophagy-mediated mitochondrial apoptosis pathway and HCC cell death.

Research conclusions

SAHA stimulated excessive reticulophagy and induced autophagy-mediated cell death, which acted synergistically with the mitochondria-dependent apoptotic pathway to facilitate HCC cell death.

Research perspectives

FAM134B-induced reticulophagy may further provide a novel avenue for more effective interventions in HCC treatment. Our results confirmed that reticulophagy participates in SAHA-induced apoptosis and autophagy-mediated cell death in HCC cells, where SAHA-induced regulation of FAM134B expression via histone H4 lysine 16 is the key to HCC cell death.