m6A RNA methylation-mediated HNF3γ reduction renders hepatocellular carcinoma dedifferentiation and sorafenib resistance

Abstract

Hepatocyte nuclear factor 3γ (HNF3γ) is a hepatocyte nuclear factor, but its role and clinical significance in hepatocellular carcinoma (HCC) remain unclear. Herein, we report that HNF3γ expression is downregulated in patient HCC and inversely correlated with HCC malignancy and patient survival. Moreover, our data suggested that the HNF3γ reduction in HCC could be mediated by METTL14-dependent m6A methylation of HNF3γ mRNA. HNF3γ expression was increased during hepatic differentiation and decreased in dedifferentiated HCC cells. Interestingly, HNF3γ delivery promoted differentiation of not only HCC cells but also liver CSCs, which led to suppression of HCC growth. Mechanistic analysis suggested an HNF3γ-centered regulatory network that includes essential liver differentiation-associated transcription factors and functional molecules, which could synergistically facilitate HCC cell differentiation. More importantly, enforced HNF3γ expression sensitized HCC cells to sorafenib-induced growth inhibition and cell apoptosis through transactivation of OATP1B1 and OATP1B3 expression, which are major membrane transporters for sorafenib uptake. Clinical investigation showed that patient-derived HCC xenografts with high HNF3γ expression exhibited a sorafenib response and patients with high HCC HNF3γ levels benefited from sorafenib therapy. Together, these results suggest that HNF3γ plays an essential role in HCC differentiation and may serve as a therapeutic target and predictor of sorafenib benefit in patients.

The functional roles, cross-talk and clinical implications of m6A modification and circRNA in hepatocellular carcinoma

“…The reduction in HNF3γ expression was mediated by METTL14-dependent m6A methylation of HNF3γ mRNA. In particular, overexpression of HNF3γ could reduce the drug resistance of HCC by upregulating the expression of OATP1B1 and OATP1B3, which are the two major membrane transport proteins affecting sorafenib absorption, thus sensitizing HCC cells to sorafenib-induced growth repression and apoptosis 25 .…”

N6-methyladenosine methyltransferases: functions, regulation, and clinical potential

“…With regard to sorafenib, an oral multitargeted receptor tyrosine kinase inhibitor, the situation is complicated since m6A methyltransferases have been reported to play opposite roles in intrinsic and acquired sorafenib-resistant in HCC. METTL14-mediated HNF3γ reduction, which leads to downregulated OATP1B1 and OATP1B3 expression and thus reduces sorafenib uptake, causes HCC dedifferentiation and intrinsic sorafenib resistance [ 112 ]. Similarly, by establishing HCC sorafenib-resistant (SR) cell lines (HepG2-SR, SKhep1-SR, Huh7-SR and LM3-SR cells), Xu et al found that METTL3 and METTL14 increase the stability of circRNA-SORE, which sequesters miR-103a-2-5p and miR-660-3p by acting as a microRNA sponge, thereby competitively activating the Wnt/β-catenin pathway and inducing sorafenib resistance [ 42 ].…”

N6-methyladenosine-dependent signalling in cancer progression and insights into cancer therapies

“…In addition, m6A modification can promote the translation of FOXO3 mRNA through the YTHDF1-dependent pathways, making liver cancer cells more sensitive to sorafenib [187]. However, the m6A-mediated HNF3γ reduction will cause liver cancer cells to be resistant to sorafenib [188]. Interestingly, m6A modification can stabilize CircRNA-SORE; CircRNA-SORE can act as a miRNA sponge, adsorbing miR-103a-2-5p and miR-660-3p, thereby competitively activating the Wnt/β-catenin pathway and inducing sorafenib resistance [189].…”