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Objectives: Targeting the deubiquitinases (DUBs) has become a promising avenue for anti‐cancer drug development. However, the effect and mechanism of pan‐DUB inhibitor, PR‐619, on oesophageal squamous cell carcinoma (ESCC) cells remain to be investigated. Materials and Methods: The effect of PR‐619 on ESCC cell growth and cell cycle was evaluated by CCK‐8 and PI staining. Annexin V‐FITC/PI double staining was performed to detect apoptosis. LC3 immunofluorescence and acridine orange staining were applied to examine autophagy. Intercellular Ca2+ concentration was monitored by Fluo‐3AM fluorescence. The accumulation of ubi‐proteins and the expression of the endoplasmic reticulum (ER) stress‐related protein and CaMKKβ‐AMPK signalling were determined by immunoblotting. Results: PR‐619 could inhibit ESCC cell growth and induce G2/M cell cycle arrest by downregulating cyclin B1 and upregulating p21. Meanwhile, PR‐619 led to the accumulation of ubiquitylated proteins, induced ER stress and triggered apoptosis by the ATF4‐Noxa axis. Moreover, the ER stress increased cytoplasmic Ca2+ and then stimulated autophagy through Ca2+‐CaMKKβ‐AMPK signalling pathway. Ubiquitin E1 inhibitor, PYR‐41, could reduce the accumulation of ubi‐proteins and alleviate ER stress, G2/M cell cycle arrest, apoptosis and autophagy in PR‐619‐treated ESCC cells. Furthermore, blocking autophagy by chloroquine or bafilomycin A1 enhanced the cell growth inhibition effect and apoptosis induced by PR‐619. Conclusions: Our findings reveal an unrecognized mechanism for the cytotoxic effects of general DUBs inhibitor (PR‐619) and imply that targeting DUBs may be a potential anti‐ESCC strategy. [ABSTRACT FROM AUTHOR]

Esophageal squamous cell carcinoma (ESCC) is one of the most malignant tumors in east Asia. However, the molecular mechanism underlying its progression remains unclear. The ubiquitin–proteasome system (UPS) is a central mechanism for protein degradation and turnover. Accumulating evidence showed that more and more deubiquitinases could serve as attractive anti-cancer target. The expression of USP14 and UCH37 in esophagus squamous cell carcinoma tissues were examined by immunohistochemistry and western blot assays. Effect of b-AP15, a USP14 and UCH37 inhibitor, on ESCC cell growth was evaluated by cell viability assay. After cell lines being treated with b-AP15, cell cycle, apoptosis and the expression of related proteins were further explored to investigate the anti-ESCC mechanism of b-AP15. Results showed that deubiquitinating enzymes (DUBs) USP14 and UCH37 expressed at higher levels in ESCC tissues than in adjacent tissues. b-AP15 could inhibit cell proliferation and induce G2/M cell cycle arrest and apoptosis in ESCC cells. Mechanistically, b-AP15 treatment triggered Noxa-dependent apoptosis, which was regulated by c-Myc. Silencing Noxa and c-Myc could reduce b-AP15-induced apoptosis in ESCC cells. Our results revealed a novel mechanism of anti-tumor activity of b-AP15 in ESCC, and b-AP15 could be used as a potential therapeutic agent in ESCC. [ABSTRACT FROM AUTHOR]

• Compound 20 inhibited ESCC cell growth in vitro and in vivo. • Compound 20 induced G2/M phase arrest. • Compound 20 induced cell apoptosis via up-regulating Noxa. A series of novel indoline derivatives were synthesized and evaluated for antiproliferative activity against four selected cancer cell lines (Hela, A549, HepG2 and KYSE30). Among them, compound 20 displayed the potent inhibition activity against esophageal cancer cells (Kyse30, Kyse450, Kyse510 and EC109). Cellular mechanism studies in esophageal squamous cell carcinoma (ESCC) cells elucidated compound 20 inhibited cell growths in vitro and in vivo , reduced colony formation, arrested cell cycle at M phase, and induced Noxa-dependent apoptosis in ESCC. Importantly, compound 20 was identified as a novel Noxa mediated apoptosis inducer. These results suggested that compound 20 might be a promising anticancer agent with potential for development of further clinical applications. [ABSTRACT FROM AUTHOR]