NIPBL-mediated RAD21 facilitates tumorigenicity by the PI3K pathway in non-small-cell lung cancer

It is urgent to identify novel early diagnostic markers and therapeutic targets for non-small-cell lung cancer (NSCLC), which accounts for 85% of lung cancer cases and has a 5-year survival rate of 4-17%. Here, chromatin immunoprecipitation (ChIP) was used to identify DNA‒protein interactions, RNA methylation was determined by methylated RNA immunoprecipitation (MeRIP), RNA stability was tested by an RNA decay assay. We showed that RAD21, a member of the cohesin complex, is upregulated in NSCLC tissues and cell lines and found to be an independent prognostic factor for overall survival (OS) of NSCLC patients. Mechanistically, the cohesin loading factor Nipped-B-Like Protein (NIPBL) promoted RAD21 gene transcription by enhancing histone H3 lysine 27 (H3K27) demethylation via recruiting lysine demethylase 6B (KDM6B) to the RAD21 gene promoter. RAD21 enhanced phosphatidylinositol 3-kinase (PI3K) gene transcription, and NIPBL reversed the effect of enhancer of zeste 2; catalytic subunit of polycomb repressive complex 2 (EZH2) on RAD21-mediated PI3K gene transcription by disrupting the association between EZH2 and RAD21. Moreover, NIPBL level was increased by stabilization of its transcripts through mRNA methylation. These findings highlight the oncogenic role of RAD21 in NSCLC and suggest its use as a potential diagnostic marker and therapeutic target for NSCLC.