Liver cancer is the sixth most common cancer and causes the third cancer-related deaths worldwide (Sung et al., 2021). Hepatocellular carcinoma (HCC) accounts for approximately 90% of primary liver cancers (Forner et al., 2018; Siegel et al., 2017). Due to a lack of understanding about preventing tumor recurrence and metastasis, there has been little success on improving disease-free survival in HCC patients (Bruix et al., 2016; Ringelhan et al., 2018). Although potential novel genes have been identified to drive HCC initiation and progression, effective treatment is still a great challenge due to the complex composition of HCC and its interaction with the tumor microenvironment.

Hypoxia is a common feature of HCC. Cells adapt to hypoxia through hypoxia-inducible factors (HIFs), which are heterodimeric proteins consisting of the HIF-1/-2α and HIF-1β subunits (Zhang et al., 2022). Under normoxia conditions, HIF-α is degraded via binding to the pVHL E3 ligase complex and the ubiquitin-proteasome pathway. However, under hypoxic conditions, HIF-α is stabilized and interacts with coactivators such as cAMP response element-binding protein/p300 to regulate the expression of target genes (Ke and Costa, 2006). HIF-1α and HIF-2α, the most extensively studied HIF isoforms, exhibit distinct roles due to their unique regulators, gene targets and differential expression patterns genes. HIF-1α primarily regulates anerobic glycolysis and controls cell death, playing a central role in the regulation of glucose metabolism (Kim et al., 2006; Nagao et al., 2019), while HIF-2α primarily regulates erythropoietin synthesis (EPO) and influences tumor stemness or pluripotency.

Glucose metabolism involves various pathways, including glycolysis, the pentose phosphate pathway (PPP), the serine synthesis pathway (SSP) in the cytoplasm, and citrate cycle (TCA cycle) in the mitochondria (Li and Zhang, 2016). Glycolysis, also known as the Warburg effect, is a hallmark of glucose metabolism (Hsu and Sabatini, 2008). Hypoxia regulates aerobic glycolysis through the modulation of metabolism-related enzymes including hexokinase (HK), glucose-6-phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK), phosphoglycerate mutase (PGAM), enolase (ENO), pyruvate kinase M2 (PKM2), and lactate dehydrogenase (LDHA) (Li and Zhang, 2016). Reprogramming of glucose metabolism plays a crucial role in the initiation and progression of HCC. Therefore, it is necessary to explore HCC therapy targeting glycolytic metabolism-related enzymes during hypoxia.

Transient receptor potential cation channel, subfamily M, member 7 (TRPM7) is ubiquitously expressed in human tissues (Cahalan, 2001; Runnels et al., 2001) and is involved in various physiological and pathological processes such as cellular Mg2+ homeostasis (Schmitz et al., 2003), embryonic development (Jin et al., 2008), cell adhesion (Clark et al., 2006), and anoxic neuronal cell death (Aarts et al., 2003). TRPM7 has also been implicated in carcinogenesis, including breast cancer (Davis et al., 2014; Guilbert et al., 2009; Kuipers et al., 2018; Middelbeek et al., 2012), retinoblastoma (Hanano et al., 2004), gastric cancer (Kim, 2013; Kim et al., 2008), nasopharyngeal cancer (Chen et al., 2010, 2015), pancreatic cancer (Rybarczyk et al., 2017; Yee et al., 2011, 2012, 2015), prostate cancer (Chen et al., 2017; Sun et al., 2013), ovarian cancer (Chen et al., 2022; Liu et al., 2019; Wang et al., 2014a, 2014b) and bladder cancer (Cao et al., 2016; Gao et al., 2017). As a unique cation channel protein, TRPM7 facilitates the transportation of cations such as calcium, thereby initiating Ca2+ signaling in cells (Du et al., 2010; Schappe et al., 2018). In addition, TRPM7 possesses kinase activity and can self-activate and phosphorylate other substrates, dependent on ATP, suggesting its potential regulation under hypoxic conditions (Runnels et al., 2001). Further, inhibition of TRPM7 has been shown to elevate AMPK activation and shift cellular metabolism from glycolysis to oxidative phosphorylation in prostate and ovarian cancers (Chen et al., 2022). Therefore, it is crucial to investigate whether hypoxia regulates TRPM7 and its correlation with glucose metabolism reprogramming in HCC.

In this study, we first demonstrated the upregulation of TRPM7 expression in hypoxia-induced HCC cell lines. Furthermore, we showed that silencing of HIF-1α and HIF-2α using siRNA inhibited TRPM7 levels. We also observed the direct transcriptional regulation of TRPM7 by HIF-1α and its involvement in glycolytic metabolism-related enzymes. Finally, we confirmed the role of TRPM7 in promoting HCC proliferation and metastasis in vitro and in vivo.