METTL3 and STAT3 form a positive feedback loop to promote cell metastasis in hepatocellular carcinoma

Abstract

Background It is well-established that most Hepatocellular carcinoma (HCC) patients die of metastasis, yet the potential mechanisms orchestrating metastasis remain poorly understood. Current evidence suggests that the dysregulation of METTL3-mediated m6A methylation modification is closely associated with cancer progression. STAT3 is an oncogenic transcription factor that reportedly plays a central role in the occurrence and development of HCC. However, the relationship between METTL3 and STAT3 in HCC metastasis remains unclear. Methods The relationship between METTL3 expression and the survival of HCC patients was assessed by online tools GEPIA and Kaplan–Meier Plotter. Western blotting, Tissue microarray (TMA), and immunohistochemistry (IHC) staining were used to evaluate the expression levels of METTL3 and STAT3 in HCC cell lines and metastatic and non-metastatic tissues. Methylated RNA immunoprecipitation (MeRIP), MeRIP sequencing (MeRIP-seq), qRT-PCR, RNA immunoprecipitation (RIP), Western blotting and luciferase reporter gene assay were utilized to clarify the mechanism of METTL3 regulating STAT3 expression. Immunofluorescence staining, Western blotting, qRT-PCR, Co-immunoprecipitation (Co-IP), IHC staining, TMA and Chromatin immunoprecipitation (ChIP) assay were performed to explore the mechanism of STAT3 modulating METTL3 localization. Cell viability, wound healing and transwell assay, and orthotopic xenograft model were used to evaluate the role of METTL3-STAT3 feedback loop in the promotion of HCC metastasis in vitro and in vivo. Results METTL3 and STAT3 are both abundantly expressed in high-metastatic HCC cells and tissues. Moreover, a positive correlation was found between the expression of STAT3 and METTL3 in HCC tissues. Mechanistically, METTL3 could induce the m6A modification of STAT3 mRNA, and then promote the translation of m6A-contained STAT3 mRNA by interacting with the translation initiation machinery. In contrast, STAT3 promoted nuclear localization of METTL3 via transcriptionally upregulating WTAP, a vital member of the methyltransferase complex, and facilitated the methyltransferase function of METTL3. METTL3 and STAT3 form a positive feedback loop to accelerate HCC metastasis in vitro and in vivo. Conclusions Our findings reveal a novel mechanism of HCC metastasis and uncover the METTL3-STAT3 feedback signaling as a potential target for the anti-metastatic treatment of HCC.

WTAP, transcriptionally regulated by p65, promotes inflammation through m6A modification and phase separation

“…Further analyses of transcription factor-binding sites revealed that the WTAP promoter contains NF-κB p65-, C/EBPβ-, IRF3-, STAT3- and HIF1α-binding motifs (Supplementary Table 2). Studies have reported that both STAT3 and HIF1α can transcriptionally upregulate the expression of WTAP in some cancer cells (36, 37), but we found that LPS-induced upregulation of WTAP was not affected by SC144 treatment, which inhibited the activation of STAT3 signaling by binding IL6ST (38) (Supplementary Figure 2, A and B). Similarly, the accumulation of HIF1α induced by CoCl 2 can upregulate WTAP (Supplementary Figure 2C), but inflammatory stimuli did not cause the accumulation of HIF1α (Supplementary Figure 2D).…”

“…In addition to showing the relationship between increased WTAP and higher m 6 A modification in inflammation, we specifically showed that an increase in WTAP protein was accompanied by increases in the pathway is aberrantly hyperactivated in many cancers, and such hyperactivation is generally associated with a poor clinical prognosis (Johnson et al, 2018). Recent studies have also shown that high levels of m 6 A modification enhance JAK1 translation in high-metastatic hepatocellular carcinoma (HCC) cells, thereby promoting the activation of STAT3 (Liu et al, 2023).…”

“…Noteworthy, the transcription and expression of WTAP have been shown to be regulated in various biological processes. For example, at the transcriptional and posttranscriptional levels, HIF1α (Shao et al, 2023) and STAT3 (Liu et al, 2023) can transactivate WTAP gene expression by directly binding to its promoter region, and WTAP can also be upregulated by the epigenetic alteration of H3K4me3, resulting in the senescence of nucleus pulposus cells (NPCs) (Li et al, 2022a). At the translational and posttranslational levels, a recent study revealed that through epigenetic modifications, the pseudogene WTAPP1 can bind to WTAP mRNA to promote its translation by recruiting the EIF3 translation initiation complex, accelerating the progression of pancreatic ductal adenocarcinoma (PDAC) (Deng et al, 2021).…”

“…Moreover, the IL-6/STAT3 pathway is aberrantly hyperactivated in many cancers, and such hyperactivation is generally associated with a poor clinical prognosis (Johnson et al, 2018). Recent studies have also shown that high levels of m 6 A modification enhance JAK1 translation in high-metastatic hepatocellular carcinoma (HCC) cells, thereby promoting the activation of STAT3 (Liu et al, 2023).…”

Non-coding RNA methylation modifications in hepatocellular carcinoma: interactions and potential implications

“…Silencing METTL3 has been shown to heighten HCC sensitivity to chemotherapy by impeding the m6A modification of p53 mRNA [ 147 ]. Furthermore, METTL3 fosters HCC metastasis by establishing a positive feedback loop with STAT3 [ 148 ]. Wang et al have also reported that the METTL3 inhibitor STM2457 targets the epidermal growth factor receptor (EGFR) to improve the sensitivity of HCC to lenvatinib therapy [ 149 ].…”