Hypoxia-Induced miR-675-5p Supports β-Catenin Nuclear Localization by Regulating GSK3-β  Activity in Colorectal Cancer Cell Lines

Abstract

The reduction of oxygen partial pressure in growing tumors triggers numerous survival strategies driven by the transcription factor complex HIF1 (Hypoxia Inducible Factor-1). Recent evidence revealed that HIF1 promotes rapid and effective phenotypic changes through the induction of non-coding RNAs, whose contribution has not yet been fully described. Here we investigated the role of the hypoxia-induced, long non-coding RNA H19 (lncH19) and its intragenic miRNA (miR-675-5p) into HIF1-Wnt crosstalk. During hypoxic stimulation, colorectal cancer cell lines up-regulated the levels of both the lncH19 and its intragenic miR-675-5p. Loss of expression experiments revealed that miR-675-5p inhibition, in hypoxic cells, hampered β-catenin nuclear localization and its transcriptional activity, while lncH19 silencing did not induce the same effects. Interestingly, our data revealed that miRNA inhibition in hypoxic cells restored the activity of Glycogen Synthase Kinase 3β (GSK-3β) reducing the amount of P-Ser9 kinase, thus unveiling a role of the miR-675-5p in controlling GSK-3β activity. Bioinformatics analyses highlighted the serine/threonine-protein phosphatases PPP2CA, responsible for GSK-3β activation, among the miR-675-5p targets, thus indicating the molecular mediator through which miR-675-5p may control β-catenin nuclear localization. In conclusion, here we demonstrated that the inhibition of the hypoxia-induced non-coding RNA miR-675-5p hampered the nuclear localization of β-catenin by regulating GSK-3β activity, thus proposing the miR-675-5p as a new therapeutic target for the treatment of colorectal cancer.

Histone deacetylase inhibitor induced pVHL-independent degradation of HIF-1α and hierarchical quality control of pVHL via chaperone system

“…GSK3β acts as a molecular regulation switch while the role of its activation in tumor progression still remains a controversy. On the one hand, upon the stimulus by Wnt in hypoxia, the GSK3/casein kinase 1 (CK1)/Axin/adenomatous polyposis coli (APC) destruction complex in the cytoplasm disintegrates, and the unphosphorylated β-catenin translocates to the nucleus and recruits on HREs, which interacts physically with HIF-1 to promote cell survival and adaptation to hypoxia [31]. Additionally, a previous study revealed overexpression of GSK3β inhibited β-catenin and HIF-1α expression [32].…”

Glycogen synthase kinase GSK3α promotes tumorigenesis by activating HIF1/VEGFA signaling pathway in NSCLC tumor

“…S3d). Recent studies showed that hypoxia could regulated GSK3β expression by HIF1α [ 35 , 36 ]. However, our study showed that silencing of GSK3α could inhibit HIF1α expression, while had no effect on GSK3β expression.…”

Hypoxia-Induced Non-Coding RNAs Controlling Cell Viability in Cancer

“…It was found up-regulated by HIF in several tumours including Glioblastoma [75,76] and colorectal cancer [77]. Recently it was described its role in controlling cell cycle by regulating Glycogen Synthase Kinase 3β (GSK-3β) activity and allowing β-catenin nuclear localization [78]. MiR-675 was found up-regulated in hypoxic non-small cell lung cancer where in addition to promoting cell proliferation, it acts on apoptosis by directly inhibiting the expression of p53 [79]; also in this case, through the induction of a single miRNA, HIF promotes tumour growth by acting simultaneously on several molecular pathways.…”