UBA2 SUMOylates NQO1 and promotes the proliferation of hepatocellular carcinoma by modulating the MAPK pathway.

In our previous study, we found that small ubiquitin-related modifier (SUMO)-activating enzyme ubiquitin-associated-2 domain (UBA2) was upregulated in hepatocellular carcinoma (HCC) patients who were insensitive to chemoembolization. In this study, we aimed to investigate the role of UBA2 in HCC progression. Three cohorts were used to evaluate the efficacy of UBA2 as a prognostic factor for HCC. Our results indicated that UBA2 was associated with aggressive clinical behaviors and was a strong indicator of poor prognosis in HCC. In vitro experiments demonstrated that UBA2 accelerated cell growth, invasion, and migration. These results were further supported by in vivo experiments. RNA-sequencing analysis indicated NQO1 as a target of UBA2, with its levels altering following UBA2 manipulation. The results were verified by western blotting (WB) and quantitative PCR. The SUMOplot Analysis Program predicted lysine residue K240 as a modification target of UBA2, which was confirmed by immunoprecipitation (IP) assays. Subsequent mutation of NQO1 at K240 in HCC cell lines and functional assays revealed the significance of this modification. In addition, the oncogenic effect of UBA2 could be reversed by the SUMO inhibitor ML792 in vivo and in vitro. In conclusion, our study elucidated the regulatory mechanism of UBA2 in HCC and suggested that the SUMO inhibitor ML792 may be an effective combinatory treatment for patients with aberrant UBA2 expression.

Clinical and biomarker analyses of hepatic arterial infusion chemotherapy plus lenvatinib and PD-1 inhibitor for patients with advanced intrahepatic cholangiocarcinoma.

Background: Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive cancer with a dismal prognosis and few effective therapeutic approaches. This study aimed to investigate the efficacy, safety, and predictive biomarkers of hepatic arterial infusion chemotherapy (FOLFOX-HAIC) in combination with lenvatinib and PD-1 inhibitor for patients with advanced iCCA. Methods: Locally advanced or metastatic iCCA patients receiving the triple combination therapy of lenvatinib, PD-1 inhibitor, and FOLFOX-HAIC were included in this retrospective study. Primary endpoint was the progression-free survival, evaluated using the RECIST criterion. The secondary endpoints included overall survival, objective response rate, and safety. Whole exome and RNA sequencing of tumor biopsy tissues were performed for biomarker exploration. Results: Between May, 2019 and December 2022, a total of 46 patients were included in this study. The primary endpoint showed a median progression-free survival of 9.40 months (95% CI: 5.28-13.52), with a 6-month progression-free survival rate of 76.1%. The median overall survival was 16.77 months (95% CI, 14.20-19.33), with an objective response rate of 47.8% and disease control rate of 91.3% per RECIST. In addition, 4.3% and 8.7% of patients achieved complete response of all lesions and intrahepatic target lesions per mRECIST, respectively. The most common treatment-related adverse events were neutropenia, thrombocytopenia, elevated aspartate aminotransferase and alanine aminotransferase level. Furthermore, integrated analysis of genetic, transcriptomic, and immunohistochemistry data revealed that pre-existing immunity (high expression level of immune-related signatures and intra-tumoral CD8+ T cell density) in baseline tumor tissues was associated with superior clinical benefits. However, the evaluation of tumor mutation burden did not show potential predictive value in this triple combination. Conclusion: FOLFOX-HAIC in combination with lenvatinib and PD-1 inhibitor demonstrated a promising antitumor activity with manageable safety profiles in patients with advanced iCCA. Moreover, our study also revealed new perspectives on potential biomarkers for clinical efficacy.

MZF1 promotes tumour progression and resistance to anti-PD-L1 antibody treatment in hepatocellular carcinoma.

Background & Aims: The mechanism underlying resistance to immunotherapy involves engagement of immune checkpoint pathways. The transcriptional and epigenetic processes of checkpoint molecules, however, have not been well investigated. We thus studied whether the transcription factor myeloid zinc finger 1 (MZF1) may promote resistance to immunotherapy in hepatocellular carcinoma (HCC). Methods: Single-cell RNA-sequencing was performed to study the correlation between MZF1 and tumour microenvironment features in six patients with HCC. Combined immunohistochemistry and multi-immunofluorescence analyses were performed for verification. Ectopic expression of MZF1 was used in both orthotopic and genetically engineered hydrodynamic mouse HCC models for in vivo experiments. Proteome analysis, including protein degradation assays, ubiquitination assays, and co-immunoprecipitation assays, revealed the function of MZF1 in immune checkpoint pathways. Results: Single-cell RNA-sequencing suggested an immunosuppressive environment and a strong correlation with the immune checkpoint programmed death ligand 1 (PD-L1) in MZF1-overexpressing tumours. Analyses of 163 HCC samples demonstrated that MZF1 expression in HCC cells is associated with decreased T-cell infiltration. In vivo experiments showed that ectopic MZF1 expression in HCC cells impairs T-cell recruitment, resulting in resistance to immune checkpoint blockade. Mechanistically, MZF1 accelerated PD-L1 ubiquitination by binding to the cyclin-dependent kinase 4 (CDK4) activation site, while a direct bond between CDK4 and MZF1 led to increased MZF1 expression. Conclusions: MZF1 promotes PD-L1 ubiquitination via CDK4 and possibly MZF1. Inhibition of CDK4 can therefore restore PD-L1 expression and may be a potential strategy for combination with anti-PD-L1 antibodies. Impact and implications: Resistance to immune checkpoint blockade with anti-programmed death ligand 1 (PD-L1) antibody therapy is attributed to oncogenic alterations of tumour cells, however, effective countermeasures are yet to be established. Here, we report that the transcription factor myeloid zinc finger 1 (MZF1) can bind to the cyclin-dependent kinase 4 (CDK4) activation site and accelerate PD-L1 ubiquitination. A CDK4 inhibitor therefore enhances anti-PD-L1 antibody efficacy by blocking MZF1 signalling. This indicates a potential benefit of combining CDK4 inhibitors and anti-PD-L1 antibodies for the treatment of advanced HCC.

DNA methylation-activated full-length EMX1 facilitates metastasis through EMX1-EGFR-ERK axis in hepatocellular carcinoma.

Altered DNA methylation is a crucial epigenetic event in hepatocellular carcinoma (HCC) development and progression. Through methylation-transcriptomic analysis, we identified a set of sixty potential DNA methylation-based epidriver genes. In this set of genes, we focused on the hypermethylation of EMX1, which is frequently observed in hepatobiliary tumors. Despite of its frequent occurrence, the function of EMX1 remains largely unknown. By utilizing bisulfite-next-generation sequencing, we have detected EMX1 DNA hypermethylation on the gene body, which is positively correlated with EMX1 mRNA expression. Further analysis revealed that EMX1 mRNA terminal exon splicing in HCC generated two protein isoforms: EMX1 full length (EMX1-FL) and alternative terminal exon splicing isoform (EMX1-X1). Cellular functional assays demonstrated that gain-of-function EMX1-FL, but not EMX1-X1, induced HCC cells migration and invasion while silencing EMX1-FL inhibited HCC cells motility. This result was further validated by in vivo tumor metastasis models. Mechanistically, EMX1-FL bound to EGFR promoter, promoting EGFR transcription and activating EGFR-ERK signaling to trigger tumor metastasis. Therefore, EGFR may be a potential therapeutic target for EMX1-high expression HCC. Our work illuminated the crucial role of gene body hypermethylation-activated EMX1-FL in promoting tumorigenesis and metastasis in HCC. These findings pave the way for targeting the EMX1-EGFR axis in HCC tumorigenicity and metastasis.

Construction of a single nucleotide variant score-related gene-based prognostic model in hepatocellular carcinoma: analysis of multi-independent databases and validation in vitro.

BACKGROUND: The accumulation of single nucleotide variants (SNVs) and the emergence of neoantigens can affect tumour proliferation and the immune microenvironment. However, the SNV-related immune microenvironment characteristics and key genes involved in hepatocellular carcinoma (HCC) are still unclear. We aimed to evaluate differences in the SNV-related immune microenvironment, construct a prognostic model and validate the key genes in vitro. METHODS: The categories of samples were defined by the expression of SNV score-related genes to evaluate the differences in mutational features, immune environment and prognosis. The survival model was constructed with survival-associated genes and verified in two independent test datasets. RCAN2, the key gene screened out for biofunction, was validated in vitro. RESULTS: IC2, among the three integrated clusters (IC1, IC2, IC3) classified by the 82 SNV score-related genes, was distinct from the rest in SNV score and immune cell infiltration, showing a better prognosis. Seven prognostic markers, HTRA3, GGT5, RCAN2, LGALS3, CXCL1, CLEC3B, and CTHRC1, were screened to construct a prognostic model. The survival model distinguished high-risk patients with poor prognoses in three independent datasets (log-rank P < 0.0001, 0.011, and 0.0068, respectively) with acceptable sensitivity and specificity. RCAN2 was inversely correlated with NK cell infiltration, and knockdown of RCAN2 promoted proliferation in HCC. CONCLUSIONS: This study revealed the characteristics of the HCC SNV-associated subgroup and screened seven latent markers for their accuracy of prognosis. Additionally, RCAN2 was preliminarily proven to influence proliferation in HCC and it had a close relationship with NK cell infiltration in vitro. With the capability to predict HCC outcomes, the model constructed with seven key differentially expressed genes offers new insights into individual therapy.