Tumor Suppressor In Hepatocellular Carcinoma Research Articles

CREB3 suppresses hepatocellular carcinoma progression by depressing AKT signaling through competitively binding with insulin receptor and transcriptionally activating RNA-binding motif protein 38.

cAMP responsive element binding protein 3 (CREB3), belonging to bZIP family, was reported to play multiple roles in various cancers, but its role in hepatocellular carcinoma (HCC) is still unclear. cAMP responsive element binding protein 3 like 3 (CREB3L3), another member of bZIP family, was thought to be transcription factor (TF) to regulate hepatic metabolism. Nevertheless, except for being TFs, other function of bZIP family were poorly understood. In this study, we found CREB3 inhibited growth and metastasis of HCC in vitro and in vivo. RNA sequencing indicated CREB3 regulated AKT signaling to influence HCC progression. Mass spectrometry analysis revealed CREB3 interacted with insulin receptor (INSR). Mechanistically, CREB3 suppressed AKT phosphorylation by inhibiting the interaction of INSR with insulin receptor substrate 1 (IRS1). In our study, CREB3 was firstly proved to affect activation of substrates by interacting with tyrosine kinase receptor. Besides, CREB3 could act as a TF to transactivate RNA-binding motif protein 38 (RBM38) expression, leading to suppressed AKT phosphorylation. Rescue experiments further confirmed the independence between the two functional manners. In conclusion, CREB3 acted as a tumor suppressor in HCC, which inhibited AKT phosphorylation through independently interfering interaction of INSR with IRS1, and transcriptionally activating RBM38.

KLF4 Suppresses the Progression of Hepatocellular Carcinoma by Reducing Tumor ATP Synthesis through Targeting the Mir-206/RICTOR Axis.

To address the increased energy demand, tumor cells undergo metabolic reprogramming, including oxidative phosphorylation (OXPHOS) and aerobic glycolysis. This study investigates the role of Kruppel-like factor 4 (KLF4), a transcription factor, as a tumor suppressor in hepatocellular carcinoma (HCC) by regulating ATP synthesis. Immunohistochemistry was performed to assess KLF4 expression in HCC tissues. Functional assays, such as CCK-8, EdU, and colony formation, as well as in vivo assays, including subcutaneous tumor formation and liver orthotopic xenograft mouse models, were conducted to determine the impact of KLF4 on HCC proliferation. Luciferase reporter assay and chromatin immunoprecipitation assay were utilized to evaluate the interaction between KLF4, miR-206, and RICTOR. The findings reveal low KLF4 expression in HCC, which is associated with poor prognosis. Both in vitro and in vivo functional assays demonstrate that KLF4 inhibits HCC cell proliferation. Mechanistically, it was demonstrated that KLF4 reduces ATP synthesis in HCC by suppressing the expression of RICTOR, a core component of mTORC2. This suppression promotes glutaminolysis to replenish the TCA cycle and increase ATP levels, facilitated by the promotion of miR-206 transcription. In conclusion, this study enhances the understanding of KLF4's role in HCC ATP synthesis and suggests that targeting the KLF4/miR-206/RICTOR axis could be a promising therapeutic approach for anti-HCC therapeutics.

CPT1A loss disrupts BCAA metabolism to confer therapeutic vulnerability in TP53-mutated liver cancer

Driver genomic mutations in tumors define specific molecular subtypes that display distinct malignancy competence, therapeutic resistance and clinical outcome. Although TP53 mutation has been identified as the most common mutation in hepatocellular carcinoma (HCC), current understanding on the biological traits and therapeutic strategies of this subtype has been largely unknown. Here, we reveal that fatty acid β oxidation (FAO) is remarkable repressed in TP53 mutant HCC and which links to poor prognosis in HCC patients. We further demonstrate that carnitine palmitoyltransferase 1 (CPT1A), the rate-limiting enzyme of FAO, is universally downregulated in liver tumor tissues, and which correlates with poor prognosis in HCC and promotes HCC progression in the de novo liver tumor and xenograft tumor models. Mechanically, hepatic Cpt1a loss disrupts lipid metabolism and acetyl-CoA production. Such reduction in acetyl-CoA reduced histone acetylation and epigenetically reprograms branched-chain amino acids (BCAA) catabolism, and leads to the accumulation of cellular BCAAs and hyperactivation of mTOR signaling. Importantly, we reveal that genetic ablation of CPT1A renders TP53 mutant liver cancer mTOR-addicted and sensitivity to mTOR inhibitor AZD-8055 treatment. Consistently, Cpt1a loss in HCC directs tumor cell therapeutic response to AZD-8055. ConclusionOur results show genetic evidence for CPT1A as a metabolic tumor suppressor in HCC and provide a therapeutic approach for TP53 mutant HCC patients.

Methylation-regulated tumor suppressor gene PDE7B promotes HCC invasion and metastasis through the PI3K/AKT signaling pathway.

Hepatocellular carcinoma (HCC) has a high mortality rate, and the mechanisms underlying tumor development and progression remain unclear. However, inactivated tumor suppressor genes might play key roles. DNA methylation is a critical regulatory mechanism for inactivating tumor suppressor genes in HCC. Therefore, this study investigated methylation-related tumor suppressors in HCC to identify potential biomarkers and therapeutic targets. We assessed genome-wide DNA methylation in HCC using whole genome bisulfite sequencing (WGBS) and RNA sequencing, respectively, and identified the differential expression of methylation-related genes, and finally screened phosphodiesterase 7B (PDE7B) for the study. The correlation between PDE7B expression and clinical features was then assessed. We then analyzed the changes of PDE7B expression in HCC cells before and after DNA methyltransferase inhibitor treatment by MassArray nucleic acid mass spectrometry. Furthermore, HCC cell lines overexpressing PDE7B were constructed to investigate its effect on HCC cell function. Finally, GO and KEGG were applied for the enrichment analysis of PDE7B-related pathways, and their effects on the expression of pathway proteins and EMT-related factors in HCC cells were preliminarily explored. HCC exhibited a genome-wide hypomethylation pattern. We screened 713 hypomethylated and 362 hypermethylated mCG regions in HCC and adjacent normal tissues. GO analysis showed that the main molecular functions of hypermethylation and hypomethylation were "DNA-binding transcriptional activator activity" and "structural component of ribosomes", respectively, whereas KEGG analysis showed that they were enriched in "bile secretion" and "Ras-associated protein-1 (Rap1) signaling pathway", respectively. PDE7B expression was significantly down-regulated in HCC tissues, and this low expression was negatively correlated with recurrence and prognosis of HCC. In addition, DNA methylation regulates PDE7B expression in HCC. On the contrary, overexpression of PDE7B inhibited tumor proliferation and metastasis in vitro. In addition, PDE7B-related genes were mainly enriched in the PI3K/ATK signaling pathway, and PDE7B overexpression inhibited the progression of PI3K/ATK signaling pathway-related proteins and EMT. PDE7B expression in HCC may be regulated by promoter methylation. PDE7B can regulate the EMT process in HCC cells through the PI3K/AKT pathway, which in turn affects HCC metastasis and invasion.

TGF-β Promotes Hepatocellular Carcinoma Metastasis Through Through m6A Modification of PCDHGA9.

Objective: Hepatocellular carcinoma (HCC) is a highly lethal cancer with significant mortality, primarily attributed to metastasis. Although Protocadherin Gamma Subfamily A, 9 (PCDHGA9) has been identified as a tumor suppressor gene in cancer metastasis, its role in HCC remains ambiguous. This study aims to clarify the role of PCDHGA9 in HCC by examining its expression, clinical significance, and molecular activities. Methods: Tissue microarray immunofluorescence analysis evaluated the expression of PCDHGA9 and its clinical relevance. In vitro experiments involved manipulating PCDHGA9 levels in SK-HEP-1 cells to assess migration through wound-healing and transwell assays. In vivo, shPCDHGA9 cell injections were utilized to observe effects on tumor growth and metastasis. Protein analysis and Western Blot validated epithelial-mesenchymal transition (EMT)-related proteins. Subsequent to TGF-β treatment, cell proliferation and apoptosis were quantified using Cell counting kit-8 and flow cytometry, respectively, followed by investigation of TGF-β effects on PCDHGA9 N6-methyladenosine (m6A) modification via Methylated RNA immunoprecipitation, RT-qPCR, and Western blot analysis. Results: Downregulation of PCDHGA9 expression in HCC tissues is correlated with poor prognosis. In vitro experiments demonstrated that modulating PCDHGA9 expression influenced HCC cell migration. In vivo, PCDHGA9 knockdown is correlated with increased metastasis. Furthermore, TGF-β stimulation promoted cell proliferation and inhibited apoptosis. Mechanistically, TGF-β-mediated m6A modification led to PCDHGA9 decay, promoting EMT in HCC cells. Conclusion: PCDHGA9 serves as a potential tumor suppressor in HCC by inhibiting EMT. During this process, TGF-β is observed to exert regulatory control over m6A modifications of PCDHGA9.

Upregulation of LHPP by saRNA inhibited hepatocellular cancer cell proliferation and xenograft tumor growth.

Hepatocellular carcinoma (HCC) is the most common primary liver cancer worldwide and no pharmacological treatment is available that can achieve complete remission of HCC. Phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) is a recently identified HCC tumor suppressor gene which plays an important role in the development of HCC and its inactivation and reactivation has been shown to result in respectively HCC tumorigenesis and suppression. Small activating RNAs (saRNAs) have been used to achieve targeted activation of therapeutic genes for the restoration of their encoded protein through the RNAa mechanism. Here we designed and validated saRNAs that could activate LHPP expression at both the mRNA and protein levels in HCC cells. Activation of LHPP by its saRNAs led to the suppression of HCC proliferation, migration and the inhibition of Akt phosphorylation. When combined with targeted anticancer drugs (e.g., regorafenib), LHPP saRNA exhibited synergistic effect in inhibiting in vitro HCC proliferation and in vivo antitumor growth in a xenograft HCC model. Findings from this study provides further evidence for a tumor suppressor role of LHPP and potential therapeutic value of restoring the expression of LHPP by saRNA for the treatment of HCC.

CGAS suppresses hepatocellular carcinoma independent of its cGAMP synthase activity.

Cyclic GMP-AMP synthase (cGAS) is a key innate immune sensor that recognizes cytosolic DNA to induce immune responses against invading pathogens. The role of cGAS is conventionally recognized as a nucleotidyltransferase to catalyze the synthesis of cGAMP upon recognition of cytosolic DNA, which leads to the activation of STING and production of type I/III interferon to fight against the pathogen. However, given that hepatocytes are lack of functional STING expression, it is intriguing to define the role of cGAS in hepatocellular carcinoma (HCC), the liver parenchymal cells derived malignancy. In this study, we revealed that cGAS was significantly downregulated in clinical HCC tissues, and its dysregulation contributed to the progression of HCC. We further identified cGAS as an immune tyrosine inhibitory motif (ITIM) containing protein, and demonstrated that cGAS inhibited the progression of HCC and increased the response of HCC to sorafenib treatment by suppressing PI3K/AKT/mTORC1 pathway in cellular and animal models. Mechanistically, cGAS recruits SH2-containing tyrosine phosphatase 1 (SHP1) via ITIM, and dephosphorylates p85 in phosphatidylinositol 3-kinase (PI3K), which leads to the suppression of AKT-mTORC1 pathway. Thus, cGAS is identified as a novel tumor suppressor in HCC via its function independent of its conventional role as cGAMP synthase, which indicates a novel therapeutic strategy for advanced HCC by modulating cGAS signaling.

Epigenetic Activation of Cytochrome P450 1A2 Sensitizes Hepatocellular Carcinoma Cells to Sorafenib.

Cytochrome P450 1A2 (CYP1A2) is a known tumor suppressor in hepatocellular carcinoma (HCC), but its expression is repressed in HCC and the underlying mechanism is unclear. In this study, we investigated the epigenetic mechanisms of CYP1A2 repression and potential therapeutic implications. In HCC tumor tissues, the methylation rates of CYP1A2 CpG island (CGI) and DNA methyltransferase (DNMT) 3A protein levels were significantly higher, and there was a clear negative correlation between DNMT3A and CYP1A2 protein expression. Knockdown of DNMT3A by siRNA significantly increased CYP1A2 expression in HCC cells. Additionally, treating HCC cells with decitabine (DAC) resulted in a dose-dependent upregulation of CYP1A2 expression by reducing the methylation level of CYP1A2 CGI. Furthermore, we observed a decreased enrichment of H3K27Ac in the promoter region of CYP1A2 in HCC tissues. Treatment with the trichostatin A (TSA) restored CYP1A2 expression in HCC cells by increasing H3K27Ac levels in the CYP1A2 promoter region. Importantly, combination treatment of sorafenib with DAC or TSA resulted in a leftward shift of the dose-response curve, lower IC50 values, and reduced colony numbers in HCC cells. Our findings suggest that hypermethylation of the CGI at the promoter, mediated by the high expression of DNMT3A, and hypoacetylation of H3K27 in the CYP1A2 promoter region, leads to CYP1A2 repression in HCC. Epigenetic drugs DAC and TSA increase HCC cell sensitivity to sorafenib by restoring CYP1A2 expression. Our study provides new insights into the epigenetic regulation of CYP1A2 in HCC and highlights the potential of epigenetic drugs as a therapeutic approach for HCC. SIGNIFICANCE STATEMENT: This study marks the first exploration of the epigenetic mechanisms underlying cytochrome P450 (CYP) 1A2 suppression in hepatocellular carcinoma (HCC). Our findings reveal that heightened DNA methyltransferase expression induces hypermethylation of the CpG island at the promoter, coupled with diminished H3K27Ac levels, resulting in the repression of CYP1A2 in HCC. The use of epigenetic drugs such as decitabine and trichostatin A emerges as a novel therapeutic avenue, demonstrating their potential to restore CYP1A2 expression and enhance sorafenib sensitivity in HCC cells.

Abstract 6954: Glycine decarboxylase regulates renal carcinoma progression and DNA damage response via interferon stimulated gene factor 3-mediated pathway

Abstract Glycine decarboxylase (GLDC) is a mitochondrial enzyme of glycine cleavage system which catalyzes glycine to donate for one-carbon metabolism. It is implicated as a tumor suppressor in hepatocellular carcinoma but as an oncogene in lung cancer. Although GLDC expression in the kidney is second highest next to the liver, the role of GLDC in the kidney remains unclear. Thus, this study was designed to determine the role of GLDC in renal carcinoma. We found markedly increased expressions of GLDC in patients with renal cell carcinoma (RCC) classified as poor-risk group based on the Memorial Sloan Kettering Cancer Center prognostic model. In vitro studies revealed that cellular proliferation, colony formation was decreased in GLDC-deficient renal carcinoma cells. Additionally in vivo xenograft studies with GLDC-deficient and -overexpressing cells also revealed that tumor sizes were noticeably decreased in GLDC-deficient cell-injected mice while those were increased in GLDC-overexpressing cell-injected mice. Mechanistically, we found GLDC regulates renal carcinoma progression via interferon (IFN) stimulated gene factor 3 (ISGF3)-mediated pathway. Expressions of IRF9 and STAT2 were increased in GLDC-deficient cells while those were decreased in GLDC-overexpressing cells. Upon inducing expression of ISGF3 subunits, GLDC deletion elevated DNA damage, mitotic catastrophe, mitochondrial deficiency induced by chemotherapy. Finally, GLDC knockdown diminished pyrimidine synthesis to impair renal cancer progression. In summary, our finding reveals that GLDC regulates renal carcinoma progression and DNA damage response via ISFG3-medated pathway and lays a scientific foundation that could support a therapeutic strategy that targets GLDC for the treatment of renal carcinoma. Citation Format: Jin Young Kim, Byung Hoon Kim, Misun Choe, Thi Tuyet Mai Pham, Mikyung Kim, Ji Hae Seo, So Jin Shin. Glycine decarboxylase regulates renal carcinoma progression and DNA damage response via interferon stimulated gene factor 3-mediated pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6954.

MiR-541 is associated with the prognosis of liver cirrhosis and directly targets JAG2 to inhibit the activation of hepatic stellate cells.

The activation of hepatic stellate cells (HSCs) has been emphasized as a leading event of the pathogenesis of liver cirrhosis, while the exact mechanism of its activation is largely unknown. Furthermore, the novel non-invasive predictors of prognosis in cirrhotic patients warrant more exploration. miR-541 has been identified as a tumor suppressor in hepatocellular carcinoma and a regulator of fibrotic disease, such as lung fibrosis and renal fibrosis. However, its role in liver cirrhosis has not been reported. Real-time PCR was used to detect miR-541 expression in the liver tissues and sera of liver cirrhosis patients and in the human LX-2. Gain- and loss-of-function assays were performed to evaluate the effects of miR-541 on the activation of LX-2. Bioinformatics analysis and a luciferase reporter assay were conducted to investigate the target gene of miR-541. miR-541 was downregulated in the tissues and sera of patients with liver cirrhosis, which was exacerbated by deteriorating disease severity. Importantly, the lower expression of miR-541 was associated with more episodes of complications including ascites and hepatic encephalopathy, a shorter overall lifespan, and decompensation-free survival. Moreover, multivariate Cox's regression analysis verified lower serum miR-541 as an independent risk factor for liver-related death in cirrhotic patients (HR = 0.394; 95% CI: 0.164-0.947; P = 0.037). miR-541 was also decreased in LX-2 cells activated by TGF-β and the overexpression of miR-541 inhibited the proliferation, activation and hydroxyproline secretion of LX-2 cells. JAG2 is an important ligand of Notch signaling and was identified as a direct target gene of miR-541. The expression of JAG2 was upregulated in the liver tissues of cirrhotic patients and was inversely correlated with miR-541 levels. A rescue assay further confirmed that JAG2 was involved in the function of miR-541 when regulating LX-2 activation and Notch signaling. Dysregulation of miR-541/JAG2 axis might be a as a new mechanism of liver fibrosis, and miR-541 could serve as a novel non-invasive biomarker and therapeutic targets for liver cirrhosis.

Identification and validation of SLCO4C1 as a biological marker in hepatocellular carcinoma based on anoikis classification features.

Hepatocellular carcinoma (HCC) exhibits a high degree of invasiveness and is closely associated with rapid disease progression. Multiple lines of evidence indicate a strong correlation between anoikis resistance and tumor progression, invasion, and metastasis. Nevertheless, the classification of anoikis in HCC and the investigation of novel biological target mechanisms in this context continue to pose challenges, requiring further exploration. Combined with HCC samples from TCGA, GEO and ICGC databases, cluster analysis was conducted on anoikis genes, revealing novel patterns among different subtypes. Significant gene analysis of different gene subtypes was performed using WCGNA. The anoikis prognostic risk model was established by Lasso-Cox. Go, KEGG, and GSEA were applied to investigate pathway enrichment primarily observed in risk groups. We compared the disparities in immune infiltration, TMB, tumor microenvironment (TME), and drug sensitivity between the two risk groups. RT-qPCR and Western blotting were performed to validate the expression levels of SLCO4C1 in HCC. The biological functions of SLCO4C1 in HCC cells were assessed through various experiments, including CCK8 assay, colony formation assay, invasion migration assay, wound healing assay, and flow cytometry analysis. HCC was divided into 2 anoikis subtypes, and the subtypeB had a better prognosis. An anoikis prognostic model based on 12 (COPZ2, ACTG2, IFI27, SPP1, EPO, SLCO4C1, RAB26, STC2, RAC3, NQO1, MYCN, HSPA1B) risk genes is important for survival and prognosis. Significant differences were observed in immune cell infiltration, TME, and drug sensitivity analysis between the risk groups. SLCO4C1 was downregulated in HCC. SLCO4C1 downregulation promoted the proliferation, invasion, migration, and apoptosis of HCC cells. The tumor-suppressive role of SLCO4C1 in HCC has been confirmed. Our study presents a novel anoikis classification method for HCC that reveals the association between anoikis features and HCC. The anoikis feature is a critical biomarker bridging tumor cell death and tumor immunity. In this study, we provided the first evidence of SLCO4C1 functioning as a tumor suppressor in HCC.

The Tumor Suppressor SOCS1 Diminishes Tolerance to Oxidative Stress in Hepatocellular Carcinoma.

SOCS1 is a tumor suppressor in hepatocellular carcinoma (HCC). Recently, we showed that a loss of SOCS1 in hepatocytes promotes NRF2 activation. Here, we investigated how SOCS1 expression in HCC cells affected oxidative stress response and modulated the cellular proteome. Murine Hepa1-6 cells expressing SOCS1 (Hepa-SOCS1) or control vector (Hepa-Vector) were treated with cisplatin or tert-butyl hydroperoxide (t-BHP). The induction of NRF2 and its target genes, oxidative stress, lipid peroxidation, cell survival and cellular proteome profiles were evaluated. NRF2 induction was significantly reduced in Hepa-SOCS1 cells. The gene and protein expression of NRF2 targets were differentially induced in Hepa-Vector cells but markedly suppressed in Hepa-SOCS1 cells. Hepa-SOCS1 cells displayed an increased induction of reactive oxygen species but reduced lipid peroxidation. Nonetheless, Hepa-SOCS1 cells treated with cisplatin or t-BHP showed reduced survival. GCLC, poorly induced in Hepa-SOCS1 cells, showed a strong positive correlation with NFE2L2 and an inverse correlation with SOCS1 in the TCGA-LIHC transcriptomic data. A proteomic analysis of Hepa-Vector and Hepa-SOCS1 cells revealed that SOCS1 differentially modulated many proteins involved in diverse molecular pathways, including mitochondrial ROS generation and ROS detoxification, through peroxiredoxin and thioredoxin systems. Our findings indicate that maintaining sensitivity to oxidative stress is an important tumor suppression mechanism of SOCS1 in HCC.

Interferon-Gamma-Inducible Protein 16 Inhibits Hepatocellular Carcinoma via Interferon Regulatory Factor 3 on Chemosensitivity.

Previous reports have suggested IFI16 as a tumor suppressor in hepatocellular carcinoma (HC). Nonetheless, the biological significance of IFI16 and its mechanism concerning resistance to cisplatin (DDP) in HC requires further exploration. Samples of tumor and corresponding para-carcinoma tissues were acquired from patients with HC. Furthermore, DDP-resistant cell lines of HC, specifically HCC, Huh7 and Hepatoblastoma, HepG3, were generated by gradually increasing the concentration of DDP. Cell apoptosis and DNA damage were evaluated by utilizing flow cytometry assay and TUNEL staining. The interaction between IFI16 and interferon regulatory factor 3 (IRF3) proteins were analyzed using Co-Immunoprecipitation (Co-IP) assay. In vivo assays were conducted by establishing HC subcutaneous xenograft tumor models. The study found a reduction in IFI16 expression in both HC tissues and DDP-resistant HC cell lines. The binding of IFI16 to IRF3 regulated DNA damage-associated markers in vitro. Overexpression of IFI16 heightened the susceptibility of DDP-induced apoptosis and DNA damage, which was counteracted by IRF3 knockdown, while strengthened by IRF3 overexpression. Moreover, overexpression of IFI16 diminished in vivo DDP-resistant HC tumorigenicity. In summary, our findings suggest that IFI16 serves as a tumor suppressor in HC by promoting DNA damage via its interaction with IRF3, thereby reversing DDP resistance.

Multi-Omics profiling identifies aldehyde dehydrogenase 2 as a critical mediator in the crosstalk between Treg-mediated immunosuppression microenvironment and hepatocellular carcinoma.

Dysregulation of the aldehyde dehydrogenase (ALDH) family has been implicated in various pathological conditions, including cancer. However, a systematic evaluation of ALDH alterations and their therapeutic relevance in hepatocellular carcinoma (HCC) remains lacking. Herein, we found that 15 of 19 ALDHs were transcriptionally dysregulated in HCC tissues compared to normal liver tissues. A four gene signature, including ALDH2, ALDH5A1, ALDH6A1, and ALDH8A1, robustly predicted prognosis and defined a high-risk subgroup exhibiting immunosuppressive features like regulatory T cell (Tregs) infiltration. Single-cell profiling revealed selective overexpression of tumor necrosis factor receptor superfamily member 18 (TNFRSF18) on Tregs, upregulated in high-risk HCC patients. We identified ALDH2 as a tumor suppressor in HCC, with three novel phosphorylation sites mediated by protein kinase C zeta that enhanced enzymatic activity. Mechanistically, ALDH2 suppressed Tregs differentiation by inhibiting β-catenin/TGF-β1 signaling in HCC. Collectively, our integrated multi-omics analysis defines an ALDH-Tregs-TNFRSF18 axis that contributes to HCC pathogenesis and represents potential therapeutic targets for this aggressive malignancy.

LASS2 enhances p53 protein stability and nuclear import to suppress liver cancer progression through interaction with MDM2/MDMX

LASS2 functions as a tumor suppressor in hepatocellular carcinoma (HCC), the most common type of primary liver cancer, but the underlying mechanism of its action remains largely unknown. Moreover, details on its role and the downstream mechanisms in Cholangiocarcinoma (CCA) and hepatoblastoma (HB), are rarely reported. Herein, LASS2 overexpression was found to significantly inhibit proliferation, migration, invasion and induce apoptosis in hepatoma cells with wild-type (HB cell line HepG2) and mutated p53 (HCC cell line HCCLM3 and CCA cell line HuCCT1). Gene set enrichment analysis determined the enrichment of the differentially expressed genes caused by LASS2 in the p53 signaling pathway. Moreover, the low expression of LASS2 in HCC and CCA tumor tissues was correlated with the advanced tumor-node-metastasis (TNM) stage, and the protein expression of LASS2 positively correlated with acetylated p53 (Lys373) protein levels. At least to some extent, LASS2 exerts its tumor-suppressive effects in a p53-dependent manner, in which LASS2 interacts with MDM2/MDMX and causes dual inhibition to disrupt p53 degradation by MDM2/MDMX. In addition, LASS2 induces p53 phosphorylation at ser15 and acetylation at lys373 to promote translocation from cytoplasm to nucleus. These findings provide new insights into the LASS2-induced tumor suppression mechanism in liver cancer and suggest LASS2 could serve as a potential therapeutic target for liver cancer.

Cathelicidin Antimicrobial Peptide Acts as a Tumor Suppressor in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is associated with high rates of metastasis and recurrence, and is one of the most common causes of cancer-associated death worldwide. This study examined the protein changes within circulating exosomes in patients with HCC against those in healthy people using isobaric tags for a relative or absolute quantitation (iTRAQ)-based quantitative proteomics analysis. The protein levels of von Willebrand factor (VWF), cathelicidin antimicrobial peptide (CAMP), and proteasome subunit beta type-2 (PSMB2) were altered in HCC. The increased levels of VWF and PSMB2 but decreased CAMP levels in the serum of patients with HCC were validated by enzyme-linked immunosorbent assays. The level of CAMP (the only cathelicidin found in humans) also decreased in the circulating exosomes and buffy coat of the HCC patients. The serum with reduced levels of CAMP protein in the HCC patients increased the cell proliferation of Huh-7 cells; this effect was reduced following the addition of CAMP protein. The depletion of CAMP proteins in the serum of healthy people enhances the cell proliferation of Huh-7 cells. In addition, supplementation with synthetic CAMP reduces cell proliferation in a dose-dependent manner and significantly delays G1-S transition in Huh-7 cells. This implies that CAMP may act as a tumor suppressor in HCC.

In vivo CRISPR screen identifies LTN1 as a novel tumor suppressor ubiquitinating insulin-like growth factor 2 mRNA-binding protein 1 in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a frequent and aggressive kind of cancer. Although E3 ligases play important roles in HCC development, several E3 ligases remain unknown. Through in vivo CRISPR knockout (KO) screens targeting related E3 ligase genes in HCC nude mice models, we discovered LTN1 as a novel tumor suppressor in HCC. Co-IP paired with 2D-LC-MS/MS and subsequent western blotting in HCC cells were used to identify the interactome of LTN1. Compared to matched normal tissues, the expression of LTN1 was decreased in human HCC tissues (ANT) (157/209). Clinically, patients with HCC who expressed low levels of LTN1 had a poor prognosis. Forced expression of LTN1 decreased cell growth in vitro and in vivo, whereas knockdown of LTN1 increased cell growth. Mechanistically, elevated LTN1 expression inhibited HCC cell growth by ubiquitinating and destabilizing the IGF2BP1 protein, which inhibited the c-Myc and IGF-1R signaling pathways. There was a negative correlation between the LTN1 protein expression and the IGF2BP1 protein expression in HCC tissues (R2=0.2799, P=0.0165). LTN1 may be a crucial tumor suppressor for determining the prognosis and a possible therapeutic target since it inhibits the proliferation of HCC cells by ubiquitinating IGF2BP1.

TRIM16 E121D variant affects the risk and prognosis of hepatocellular carcinoma by modulating the Wnt/β-catenin pathway.

TRIM16 has been identified as a tumor suppressor in hepatocellular carcinoma (HCC). This study aimed to investigate whether there are genetic variants in TRIM16 influencing HCC risk and/or prognosis and explore the mechanisms. We performed a gene-wide single-nucleotide polymorphism (SNP) mining in TRIM16. The associations of SNPs with both HCC risk and prognosis were assessed through two independent cohorts respectively. Functional experiments were performed to investigate the underlying mechanisms. A missense variant rs2074890 (G > T, resulting in an amino acid substitution from glutamate to aspartate at code 121, E121D) of TRIM16 was found to be associated with both HCC risk (odds ratio = 0.806, p = 0.023) and prognosis (hazard ratio = 0.44, p = 0.034). Compared to the rs2074890 G allele (corresponding to TRIM16121E ) homozygote carriers, the rs2074890 T allele (corresponding to TRIM16121D ) carriers showed lower HCC risk and better overall survival. Mechanistically, TRIM16121D has stronger ability to inhibit proliferation, migration, and invasion of HCC cells. Furthermore, TRIM16121D could bind to β-catenin better and mediate K48-linked ubiquitination to degrade β-catenin, which leads to inhibition of Wnt/β-catenin pathway. In conclusion, TRIM16 E121D variant impacts both risk and prognosis of HCC via regulation of Wnt/β-catenin pathway, which may lead to better understanding the pathogenesis of HCC.

RNF125 attenuates hepatocellular carcinoma progression by downregulating SRSF1-ERK pathway.

Hepatocellular carcinoma (HCC) is one of the most deadly malignant cancers worldwide. Research into the crucial genes responsible for maintaining the aggressive behaviour of cancer cells is important for the clinical treatment of HCC. The purpose of this study was to determine whether the E3 ubiquitin ligase Ring Finger Protein 125 (RNF125) plays a role in the proliferation and metastasis of HCC. RNF125 expression in human HCC samples and cell lines was investigated using TCGA dataset mining, qRT‒PCR, western blot, and immunohistochemistry assays. In addition, 80 patients with HCC were studied for the clinical value of RNF125. Furthermore, the molecular mechanism by which RNF125 contributes to hepatocellular carcinoma progression was determined with mass spectrometry (MS), coimmunoprecipitation (Co-IP), dual-luciferase reporter assays, and ubiquitin ladder assays. We found that RNF125 was markedly downregulated in HCC tumour tissues, which was associated with a poor prognosis for patients with HCC. Moreover, the overexpression of RNF125 inhibited HCC proliferation and metastasis both in vitro and in vivo, whereas the knockdown of RNF125 exerted antithetical effects. Mechanistically, mass spectrometry analysis revealed a protein interaction between RNF125 and SRSF1, and RNF125 accelerated the proteasome-mediated degradation of SRSF1, which impeded HCC progression by inhibiting the ERK signalling pathway. Furthermore, RNF125 was detected to be the downstream target of miR-103a-3p. In this study, we identified that RNF125 is a tumour suppressor in HCC and inhibits HCC progression by inhibiting the SRSF1/ERK pathway. These findings provide a promising treatment target for HCC.

Abstract 3810: MicroRNA-483-5p inhibits cell steatosis and fibrosis by targeting PPARa, TIMP2 and HCC cell proliferation by modulating notch signaling

Abstract MicroRNAs (miRNAs) are small non-coding RNA molecules that bind with 3’ untranslated regions (UTRs) of genes and regulate expression. Downregulation of miR-483-5p (miR-483), is associated with the progression of hepatocellular carcinoma (HCC). However, the molecular and mechanistic role of miR-483 in nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD), and HCC remain elusive. In the current study, we investigated the biological significance of miR-483-5p in NAFLD, AFLD, and HCC in vitro and in vivo. Our data show that the expression of miR-483 was downregulated in tumor samples from HCC patients. Overexpression of miR-483 in HCC cells dysregulated Notch signaling, inhibited cell proliferation/migration, induced apoptosis, and increased sensitivity towards sorafenib/regorafenib; anti-HCC drugs. Interestingly, miR-483 overexpression downregulated cell steatosis and fibrogenic signaling in HCC cells. Mechanistically, miR-483 targets peroxisome proliferator-activated receptor α (PPARα) and tissue inhibitor of metalloproteinases 2 (TIMP2) gene expression by binding to 3’-UTR and suppress cell steatosis and fibrosis. Down-regulation of miR-483 was observed in mice fed with a high-fat diet (HFD) or alcohol which lead to increased hepatic steatosis/fibrosis. Our data suggest that miR-483 inhibits cell steatosis and fibrogenic signaling, and functions as a tumor suppressor in HCC. Therefore, miR-483 may be used as a novel therapeutic target for NAFLD/AFLD/HCC management in patients with fatty live diseases/HCC. Citation Format: Suryakant Niture, Sashi Gadi, Qi Qi, Maxwell Gyamfi, Leslimar Rios-Colon, Rency Varghese, Habtom Ressom, Deepak Kumar. MicroRNA-483-5p inhibits cell steatosis and fibrosis by targeting PPARa, TIMP2 and HCC cell proliferation by modulating notch signaling. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3810.