Li, M.; Huang, D.; Ren, Y.; Wang, Z.; Li, Y.; Zuo, W.; Li, Y.; Jin, Y.; Xiong, Y.

Isthmin-1 (ISM1) is a recently identified adipokine that promotes glucose uptake and enhances cellular metabolism. While the activity of the ISM1 protein is regulated by glycosylases, its transcriptional and posttranscriptional regulation remain poorly understood. A novel alternatively spliced variant of ISM1 (ISM1-AS) was recently identified. Unlike canonical ISM1, ISM1-AS lacks an AMOP domain, a key structural element required for ISM1 function, suggesting the loss of its metabolic regulatory activity. In this study, we found that ISM1 expression was significantly reduced in HCC tissues and correlated with poor prognosis. Functional assays revealed that ISM1 overexpression markedly suppressed HCC cell proliferation and invasion, whereas ISM1-AS overexpression had the opposite effect. Importantly, ISM1 co-overexpression attenuated the oncogenic effects of ISM1-AS. Knockdown of the antisense transcript lncRNA-ISM1 reduced ISM1-AS expression while increasing ISM1 expression, thereby suppressing HCC proliferation and migration.Our findings demonstrate that lncRNA-ISM1 promotes HCC progression through the RBM10-mediated alternative splicing of ISM1 and activation of the Akt-S6 signalling pathway, highlighting its potential as a therapeutic target for HCC.