Long noncoding RNA CRCMSL suppresses tumor invasive and metastasis in colorectal carcinoma through nucleocytoplasmic shuttling of HMGB2

Long noncoding RNAs (lncRNAs) are pervasive transcripts that play pivotal roles in regulating chromatin dynamics, gene and protein expression. Aberrant expression and mutations of lncRNAs represent a driving force behind tumor invasion and metastasis, making them attractive cancer targets. However, most of the lncRNAs are still being discovered and conclusive experimental evidence for their functional relevance is still lacking for most malignancies. In this study, a differentially expressed lncRNA, designated as lnc-CRCMSL, is identified by microarray-based screenings on non-metastatic and metastatic CRC specimens. Lnc-CRCMSL is verified as an anti-metastatic gene and negatively correlated with the poor prognosis of CRC patients. Lnc-CRCMSL overexpression restricts tumor growth and metastasis in vivo and in vitro. Instead, lnc-CRCMSL silencing accelerates CRC cell proliferation and migration. RNA-pulldown assay identifies high mobility group box 2 (HMGB2) as a downstream protein of lnc-CRCMSL. Mechanically, lnc-CRCMSL physically binds to HMGB2 and stabilizes the localization of HMGB2 in the cytoplasm. Notably, lnc-CRCMSL knockdown lead to the shift of HMGB2 into nuclear, in which it triggers epithelial to mesenchymal transition (EMT) programming. Importantly, lnc-CRCMSL controls the cytoplasmic retention of HMGB2 and attenuates the interaction between HMGB2 and OCT4 to suppress EMT. Treatment of leptomycin B (LMB), a potent and specific nuclear export inhibitor, counteracts lnc-CRCMSL-mediated suppression of aggressive phenotypes and EMT process by accumulating the nuclear HMGB2. Conclusion Our data highlight the anti-metastatic role of lnc-CRCMSL in stabilizing HMGB2 through lncRNA-protein interactions in the cytoplasm, and suggest that targeting lnc-CRCMSL may represent a therapeutic opportunity for managing metastatic CRC.