SHC4 promotes tumor proliferation and metastasis by activating STAT3 signaling in hepatocellular carcinoma

Background The Src homology and collagen 4 (SHC4) is an important intracellular adaptor protein that has been shown to play a pro-cancer role in melanoma and glioma. However, the biological function and detailed mechanisms of SHC4 in hepatocellular carcinoma progression are unclear. This study aimed to evaluate the potential prognostic and treatment value of SHC4 in patients with HCC. Methods The expression status of SHC4 in HCC tissues were investigated by immunohistochemistry and western blotting. Clinical significance of SHC4 was evaluated in a large cohort of HCC patients. The effects of SHC4 repression or overexpression on migration, invasion, and tumor growth were detected by colony formation assay, wound healing, transwell assays, and xenograft assay. Cell cycle and EMT-related proteins were detected by western blotting and immunofluorescence. In addition, the molecular regulation between SHC4 and STAT3 signaling in HCC were discovered by western blotting, immunofluorescence and xenograft assay. Results SHC4 was overexpressed in HCC compared to adjacent normal liver tissues and increased SHC4 expression was associated with high AFP level, incomplete tumor encapsulation, poor tumor differentiation and poor prognosis. SHC4 was shown to enhance cell proliferation, colony formation, cells migration and invasion in vitro, and promotes cell cycle progression and EMT process in HCC cells. Tumor xenograft model assay confirmed the oncogenic role of SHC4 in tumorigenicity in nude mice. Moreover, activation of STAT3 signaling was found in the SHC4 overexpressed HCC cells and HCC tissues. Further intervention of STAT3 confirmed STAT3 as an important signaling pathway for the oncogenic role of SHC4 in HCC. Conclusions Together, our results reveal that SHC4 activates STAT3 signaling to promote HCC progression, which may provide new clinical ideas for the treatment of HCC.

Oxidative stress promotes liver cancer metastasis via a PKA-activated RNF25/ECAD/YAP circuit

Loss of E-cadherin (ECAD), often caused by epigenetic inactivation, is closely associated with tumor metastasis. However, how ECAD is regulated in response to oxidative stress during tumorigenesis is largely unknown. Here we identify RNF25 as a new E3 ligase of ECAD, whose activation by oxidative stress leads to ECAD protein degradation in hepatocellular carcinoma (HCC). Loss of ECAD activates YAP, which in turn promotes the transcription of RNF25, thus forming a positive feedback loop to sustain the ECAD downregulation. YAP activation mitigates oxidative stress in detached HCC cells by upregulating antioxidant genes, protecting detached HCC cells from ferroptosis, resulting in anoikis resistance. Mechanistically, we found that protein kinase A (PKA) senses oxidative stress by redox modification in its β catalytic subunit (PRKACB) at Cys200 and Cys344, which increases its kinase activity towards RNF25 phosphorylation at Ser450, facilitating RNF25-mediated degradation of ECAD. Moreover, RNF25 expression is associated with HCC metastasis and depletion of RNF25 is sufficient to diminish HCC invasion and metastasis in vitro and in vivo. Together, these results identify a dual role of RNF25 as a critical regulator of ECAD protein turnover, promoting both anoikis resistance and metastasis, and PKA is a necessary redox sensor to enable this process. Our study provides mechanistic insight into how tumor cells sense oxidative stress signals to spread while escaping cell death.

FAM21C Promotes Hepatocellular Carcinoma Invasion and Metastasis by Driving Actin Cytoskeleton Remodeling via Inhibiting Capping Ability of CAPZA1

Hepatocellular carcinoma (HCC) is characterized by a high incidence of metastasis. The dynamic remodeling of the actin cytoskeleton plays an important role in the invasion and migration of HCC cells. In previous studies, we found that CAPZA1, a capping protein, can promote EMT of HCC cells by regulating the remodeling of the actin filament (F-actin) cytoskeleton, thus promoting the invasion and migration of HCC cells. In this study, we found that FAM21C may have a regulatory effect on CAPZA1, and we conducted an in-depth study on its potential regulatory mechanism. First, we found that FAM21C is highly expressed in HCC tissues and its high expression could promote the malignant progression of HCC. Meanwhile, the high expression of FAM21C promoted the invasion and migration of HCC cells in vitro and in vivo. Further, FAM21C interacted with CAPZA1, and their binding inhibited the capping capacity of CAPZA1, thus promoting the invasion and migration of HCC cells. This effect of FAM21C was abolished by mutating the CP-interacting (CPI) domain, the CAPZA1 binding site on FAM21C. In conclusion, high expression of FAM21C in HCC tissues can promote malignant progression of HCC and its potential mechanism involves FAM21C inhibition of CAPZA1 capping capacity by binding to CAPZA1, which drives F-actin cytoskeleton remodeling, and thus promotes invasion and migration of HCC cells.

Sirtuin 1 Protects the Mitochondria in Hepatocellular Carcinoma Cells via Suppressing Hypoxia-induced Factor-1 Alpha Expression

Background: We hypothesized that Sirtuin 1 (SIRT1) might attenuate the Warburg effect in tumor cells by modulating hypoxia-induced factor-1 alpha (HIF-1α) expression. This study aimed to explore the role and the underlying mechanism of SIRT1 in protecting the mitochondrial functions in hepatocellular carcinoma (HCC) cells. Methods: Quantitative real-time PCR and western blot analysis were conducted to determine gene expression in HCC cells. Co-immunoprecipitation (co-IP), chromatin immunoprecipitation (ChIP), and luciferase reporter assays were performed to examine DNA-protein interactions. Colony formation and MTT assays were carried out to explore the role of SIRT1 in HCC cell proliferation in vitro. PLC5 and Huh7 tumor xenografts were generated in mice to investigate the role of SIRT1–HIF-1α signaling in HCC development in vivo. Results: In different HCC cell lines, overexpression of SIRT1 promoted oxidative phosphorylation-associated gene expressions, ATP production, cell proliferation, and apoptotic protein expression while attenuating VEGF expression. In mice, overexpression of SIRT1 resulted in significant reductions in the weights of PLC5 and Huh7 tumor xenografts. Knockdown of SIRT1 exhibited opposite effects. Mechanistically, overexpression of SIRT1 promoted HIF-1α deacetylation, VHL-mediated HIF-1α degradation, and AMPK expression. Furthermore, SIRT1 interfered with the HIF-1α–c-Myc interaction to stimulate the transcription of a mitochondrial biogenesis enhancer mitochondrial transcription factor A (TFAM). Overexpression of HIF-1α completely reversed the effects of SIRT1.Conclusions: SIRT1 protects the mitochondria of HCC cells via suppressing HIF-1α expression, suggesting that SIRT1 may exert antitumor activity in HCC by reducing the Warburg effect.

SERMs (selective estrogen receptor modulator), acting as estrogen receptor β agonists in hepatocellular carcinoma cells, inhibit the transforming growth factor-α-induced migration via specific inhibition of AKT signaling pathway

Selective estrogen receptor modulator (SERM) interacts with estrogen receptors and acts as both an agonist or an antagonist, depending on the target tissue. SERM is widely used as a safer hormone replacement therapeutic medicine for postmenopausal osteoporosis. Regarding hepatocellular carcinoma (HCC), accumulating evidence indicates gender differences in the development, and that men are at higher morbidity risk than premenopausal women, suggesting that estrogen protects against HCC. However, it remains unclear whether SERM affects the HCC progression. Previously, we have shown that transforming growth factor (TGF)-α promotes the migration of HCC cells via p38 mitogen-activated protein kinases (MAPK), c-Jun N-terminal kinase and AKT. In the present study, we investigated whether SERM such as tamoxifen, raloxifene and bazedoxifene, affects the HCC cell migration using human HCC-derived HuH7 cells. Raloxifene and bazedoxifene but not tamoxifen, significantly suppressed the TGF-α-induced HuH7 cell migration. ERB041 and DPN, estrogen receptor (ER) β agonists, inhibited the TGF-α-induced cell migration whereas PPT, an ERα agonist, did not show the suppressive effect on the cell migration. ERB041 attenuated the TGF-α-induced phosphorylation of AKT without affecting the phosphorylation of p38 MAPK and c-Jun N-terminal kinase. Raloxifene and bazedoxifene also inhibited the phosphorylation of AKT by TGF-α. Furthermore, PHTPP, an ERβ antagonist, significantly reversed the suppression by both raloxifene and bazedoxifene of the TGF-α-induced cell migration. Taken together, our results strongly indicate that raloxifene and bazedoxifene, SERMs, suppress the TGF-α-induced migration of HCC cells through ERβ-mediated inhibition of the AKT signaling pathway.

Two Differentially Methylated Region (DMR) Networks in Nonalcoholic Fatty Liver Disease, Viral Hepatitis, and Hepatocellular Carcinoma

Background We previously reported that two differentially methylated region (DMR) networks identified by DMR, and co-methylation analyses are strongly correlated with the fibrosis stages of nonalcoholic fatty liver disease (NAFLD). In the current study, we examined these DMR networks in viral hepatitis and hepatocellular carcinoma (HCC). Methods We performed co-methylation analysis of DMRs using a normal dataset (GSE48325), two NAFLD datasets (JGAS000059 and GSE31803), and two HCC datasets (GSE89852 and GSE56588). Results One DMR network was clearly observed in viral hepatitis and two HCC populations. Methylation levels of genes in this network were higher in viral hepatitis and lower in HCC. Fatty acid binding protein 1 (FABP1), serum/glucocorticoid regulated kinase 2 (SGK2), and hepatocyte nuclear factor 4 α (HNF4A) were potential hub genes in this network. Increased methylation levels of the FABP1 gene deteriorated the protection capacity of hepatocytes from oxidative metabolites in NAFLD and viral hepatitis. The decreased methylation levels of SGK2 facilitated the growth and proliferation of HCC cells. Decreased methylation levels of HNF4A in HCC cells were associated with tumorigenesis. The other DMR network was observed in NAFLD, but not in viral hepatitis or HCC. This second network-included genes involved in transcriptional regulation, cytoskeleton organization, and cellular proliferation, which are specifically related to fibrosis and/or tumorigenesis in NAFLD. Conclusions Our results suggest that one DMR network was associated with fibrosis and tumorigenesis in both NAFLD and viral hepatitis, while the other network was specifically associated with NAFLD progression. FABP1, SGK2, and HNF4A could be possible candidate targets for the prevention and treatment of HCC.

CRISPR screens uncover protective effect of PSTK as a regulator of chemotherapy-induced ferroptosis in hepatocellular carcinoma

Background Hepatocellular carcinoma (HCC) is among the most common forms of cancer and is associated with poor patient outcomes. The emergence of therapeutic resistance has hampered the efficacy of targeted treatments employed to treat HCC patients to date. In this study, we conducted a series of CRISPR/Cas9 screens to identify genes associated with synthetic lethality capable of improving HCC patient clinical responses. Methods CRISPR-based loss-of-function genetic screens were used to target 18,053 protein-coding genes in HCC cells to identify chemotherapy-related synthetic lethal genes in these cells. Synergistic effects were analyzed through in vitro and in vivo analyses, while related mechanisms were explored through RNA-seq and metabolomics analyses. Potential inhibitors of identified genetic targets were selected through high-throughput virtual screening. Results The inhibition of phosphoseryl-tRNA kinase (PSTK) was found to increase HCC cell sensitivity to chemotherapeutic treatment. PSTK was associated with the suppression of chemotherapy-induced ferroptosis in HCC cells, and the depletion of PSTK resulted in the inactivation of glutathione peroxidative 4 (GPX4) and the disruption of glutathione (GSH) metabolism owing to the inhibition of selenocysteine and cysteine synthesis, thus enhancing the induction of ferroptosis upon targeted chemotherapeutic treatment. Punicalin, an agent used to treat hepatitis B virus (HBV), was identified as a possible PSTK inhibitor that exhibited synergistic efficacy when applied together with Sorafenib to treat HCC in vitro and in vivo. Conclusions These results highlight a key role for PSTK as a mediator of resistance to targeted therapeutic treatment in HCC cells that functions by suppressing ferroptotic induction. PSTK inhibitors may thus represent ideal candidates for overcoming drug resistance in HCC.

Epigenetic regulation of ferroptosis via ETS1/miR-23a-3p/ACSL4 axis mediates sorafenib resistance in human hepatocellular carcinoma

Background Drug resistance to sorafenib greatly limited the benefits of treatment in patients with hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) participate in the development of drug resistance. The key miRNA regulators related to the clinical outcome of sorafenib treatment and their molecular mechanisms remain to be identified. Methods The clinical significance of miRNA-related epigenetic changes in sorafenib-resistant HCC was evaluated by analyzing publicly available databases and in-house human HCC tissues. The biological functions of miR-23a-3p were investigated both in vitro and in vivo. Proteomics and bioinformatics analyses were conducted to identify the mechanisms that regulating miR-23a-3p. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were used to validate the binding relationship of miR-23a-3p and its targets. Results We found that miR-23a-3p was the most prominent miRNA in HCC, which was overexpressed in sorafenib non-responders and indicated poor survival and HCC relapse. Sorafenib-resistant cells exhibited increased miR-23a-3p transcription in an ETS Proto-Oncogene 1 (ETS1)-dependent manner. CRISPR-Cas9 knockout of miR-23a-3p improved sorafenib response in HCC cells as well as orthotopic HCC tumours. Proteomics analysis suggested that sorafenib-induced ferroptosis was the key pathway suppressed by miR-23a-3p with reduced cellular iron accumulation and lipid peroxidation. MiR-23a-3p directly targeted the 3′-untranslated regions (UTR) of ACSL4, the key positive regulator of ferroptosis. The miR-23a-3p inhibitor rescued ACSL4 expression and induced ferrotoptic cell death in sorafenib-treated HCC cells. The co-delivery of ACSL4 siRNA and miR-23a-3p inhibitor abolished sorafenib response. Conclusion Our study demonstrates that ETS1/miR-23a-3p/ACSL4 axis contributes to sorafenib resistance in HCC through regulating ferroptosis. Our findings suggest that miR-23a-3p could be a potential target to improve sorafenib responsiveness in HCC patients.

Exosomal hsa_circ_0004658 derived from RBPJ overexpressed-macrophages inhibits hepatocellular carcinoma progression via miR-499b-5p/JAM3

Macrophage-derived exosomes (Mφ-Exo) have multidimensional involvement in tumor initiation, progression, and metastasis, but their regulation in hepatocellular carcinoma (HCC) is not fully understood. RBPJ has been implicated in macrophage activation and plasticity. In this study we assess the role of exosomes derived from RBPJ-overexpressed macrophages (RBPJ+/+ Mφ-Exo) in HCC. The circular RNA (circRNA) profiles in RBPJ+/+ Mφ-Exo and THP-1-like macrophages (WT Mφ)-Exo was evaluated using circRNA microarray. CCK-8, Transwell, and flow cytometry analyses were used to evaluate the function of Mφ-Exo-circRNA on HCC cells. Luciferase reporter assays, RNA immunoprecipitation, and Pearson’s correlation analysis were used to confirm interactions. A nude mouse xenograft model was used to further analyze the functional significance of Mφ-Exo-cirRNA in vivo. Our results shown that hsa_circ_0004658 is upregulated in RBPJ+/+ Mφ-Exo compared to WT Mφ-Exo. RBPJ+/+ Mφ-Exo and hsa_circ_0004658 inhibits proliferation and promotes apoptosis in HCC cells, whereas hsa_circ_0004658 knockdown stimulated cell proliferation and migration but restrained apoptosis in vitro and promotes tumor growth in vivo. The effects of RBPJ+/+ Mφ-Exo on HCC cells can be reversed by the hsa_circ_0004658 knockdown. Mechanistic investigations revealed that hsa_circ_0004658 acts as a ceRNA of miR-499b-5p, resulting in the de-repression of JAM3. These results indicate that exosome circRNAs secreted from RBPJ+/+ Mφ inhibits tumor progression through the hsa_circ_0004658/miR-499b-5p/JAM3 pathway and hsa_circ_0004658 may be a diagnostic biomarker and potential target for HCC therapy.

ZC3H13 Inhibits the Progression of Hepatocellular Carcinoma through m6A-PKM2-Mediated Glycolysis and Enhances Chemosensitivity

Objective. N6-Methyladenosine (m6A) is the most prevalent RNA epigenetic modulation in eukaryotic cells, which serves a critical role in diverse physiological processes. Emerging evidences indicate the prognostic significance of m6A regulator ZC3H13 in hepatocellular carcinoma (HCC). Herein, this study was conducted for revealing biological functions and mechanisms of ZC3H13 in HCC. Methods. Expression of ZC3H13 was examined in collected HCC and normal tissues, and its prognostic significance was investigated in a public database. Gain/loss of functional assays were presented for defining the roles of ZC3H13 in HCC progression. The specific interactions of ZC3H13 with PKM2 were validated in HCC cells via mRNA stability, RNA immunoprecipitation, and luciferase reporter and MeRIP‐qPCR assays. Moreover, rescue experiments were carried out for uncovering the mechanisms. Results. ZC3H13 expression was downregulated in HCC, and its loss was in relation to dismal survival outcomes. Functionally, overexpressed ZC3H13 suppressed proliferation, migration, and invasion and elevated apoptotic levels of HCC cells. Moreover, ZC3H13 overexpression sensitized to cisplatin and weakened metabolism reprogramming of HCC cells. Mechanically, ZC3H13-induced m6A modified patterns substantially abolished PKM2 mRNA stability. ZC3H13 facilitated malignant behaviors of HCC cells through PKM2-dependent glycolytic signaling. Conclusion. Collectively, ZC3H13 suppressed the progression of HCC through m6A-PKM2-mediated glycolysis and sensitized HCC cells to cisplatin, which offered a fresh insight into HCC therapy.