Nuclear MYH9-induced CTNNB1 transcription, targeted by staurosporin, promotes gastric cancer cell anoikis resistance and metastasis

Abstract

<b>Rationale:</b> Peritoneal metastasis predicts poor prognosis of gastric cancer (GC) patients, and the underlying mechanisms are poorly understood. <b>Methods:</b> The 2-DIGE, MALDI-TOF/TOF MS and single-cell transcriptome were used to detect differentially expressed proteins among normal gastric mucosa, primary GC and peritoneal metastatic tissues. Lentiviruses carrying shRNA and transcription activator-like effector nuclease technology were used to knock down myosin heavy chain 9 (MYH9) expression in GC cell lines. Immunofluorescence, immune transmission electron microscopy, chromatin fractionation, co-immunoprecipitation, and assays for chromatin immunoprecipitation, dual luciferase reporter, agarose-oligonucleotide pull-down, flow cytometry and cell anoikis were performed to uncover nuclear MYH9-induced β-catenin (<i>CTNNB1</i>) transcription <i>in vitro</i>. Nude mice and conditional transgenic mice were used to investigate the findings <i>in vivo</i>. <b>Results:</b> We observed that MYH9 was upregulated in metastatic GC tissues and was associated with a poor prognosis of GC patients. Mechanistically, we confirmed that MYH9 was mainly localized in the GC cell nuclei by four potential nuclear localization signals. Nuclear MYH9 bound to the <i>CTNNB1</i> promoter through its DNA-binding domain, and interacted with myosin light chain 9, β-actin and RNA polymerase II to promote <i>CTNNB1</i> transcription, which conferred resistance to anoikis in GC cells <i>in vitro</i> and <i>in vivo</i>. Staurosporine reduced nuclear MYH9 S1943 phosphorylation to inhibit <i>CTNNB1</i> transcription, Wnt/β-catenin signaling activation and GC progression in both orthotropic xenograft GC nude mouse and transgenic GC mouse models. <b>Conclusion:</b> This study identified that nuclear MYH9-induced CTNNB1 expression promotes GC metastasis, which could be inhibited by staurosporine, indicating a novel therapy for GC peritoneal metastasis.