SEC61 translocon subunit gamma enhances low-dose cisplatin-induced cancer-stem cell properties of head and neck squamous cell carcinoma via enhancing Ca(2+)-mediated autophagy

BACKGROUND/PURPOSE: High SEC61 translocon subunit gamma (SEC61G) expression is associated with an unfavorable prognosis in patients with head and neck squamous cell carcinoma (HNSCC), but the underlying mechanisms remain poorly understood. MATERIALS AND METHODS: HNSCC representative cell lines SCC15 and CAL27 were used to explore the regulation of SEC61G on Ca(2+) leak from the endoplasmic reticulum (ER). Ca(2+−)activated autophagy was monitored by fluorescent labeling of autophagosomes and western blotting assays. CSC marker expression, sphere formation, colony formation, and transwell of invasion were detected to investigate the role of SEC61G in regulating cancer-stem cell (CSC) properties. RESULTS: Among the SEC61 complex genes, only SEC61G upregulation is consistently associated with unfavorable progression-free interval and disease-specific survival in patients with HNSCC. Low-dose cisplatin (CDDP) treatment induced SEC61G upregulation in SCC15 and CAL27 cells. SEC61G knockdown significantly impaired CDDP-induced Ca(2+) from the ER and the phosphorylation of ERK1/2 and AMPK. CDDP-induced autophagy in HNSCC cells were hampered by SEC61G shRNA, in terms of impaired autophagosome formation, lowered LC3-II/GAPDH ratio and restored p62 expression. CDDP-induced CSC properties, including CSC marker expression, sphere formation, colony formation, and invasive capabilities could be suppressed by shSEC61G and chloroquine, a specific autophagy inhibitor. CONCLUSION: Findings of this study revealed the contribution of SEC61G in promoting cisplatin-induced CSC properties of HNSCC cells via promoting Ca(2+)-mediated autophagy.