Elevated FBXL6 expression in hepatocytes activates VRK2-transketolase-ROS-mTOR-mediated immune evasion and liver cancer metastasis in mice.

Metastatic hepatocellular carcinoma (HCC) is the most lethal malignancy and lacks effective treatment. FBXL6 is overexpressed in human hepatocellular carcinoma (HCC), but whether this change drives liver tumorigenesis and lung metastasis in vivo remains unknown. In this study, we aimed to identify FBXL6 (F-Box and Leucine Rich Repeat Protein 6) as a key driver of HCC metastasis and to provide a new paradigm for HCC therapy. We found that elevated FBXL6 expression in hepatocytes drove HCC lung metastasis and was a much stronger driver than Kras mutation (KrasG12D/+;Alb-Cre), p53 haploinsufficiency (p53+/-) or Tsc1 loss (Tsc1fl/fl;Alb-Cre). Mechanistically, VRK2 promoted Thr287 phosphorylation of TKT and then recruited FBXL6 to promote TKT ubiquitination and activation. Activated TKT further increased PD-L1 and VRK2 expression via the ROS-mTOR axis, leading to immune evasion and HCC metastasis. Targeting or knockdown of TKT significantly blocked FBXL6-driven immune evasion and HCC metastasis in vitro and in vivo. Notably, the level of active TKT (p-Thr287 TKT) was increased and was positively correlated with the FBXL6 and VRK2 expression levels in HCC patients. Our work provides novel mechanistic insights into FBXL6-driven HCC metastasis and suggests that targeting the TKT-ROS-mTOR-PD-L1/VRK2 axis is a new paradigm for treating patients with metastatic HCC with high FBXL6 expression.

Mutant Kras and mTOR crosstalk drives hepatocellular carcinoma development via PEG3/STAT3/BEX2 signaling.

Background & Aims: Abnormal activation of mTOR through loss of tuberous sclerosis complex (Tsc) frequently occurs in hepatocellular carcinoma (HCC). Mutant Kras could induce aggressive HCCs. Here, we aim to identify the predictive or prognostic biomarkers for HCC patients with Kras mutant and mTOR hyperactivation, and to provide potential therapeutic approaches for this subtype of HCCs. Methods: We generated transgenic mice in which hepatocytic mTOR was hyperactivated through Tsc1 insufficiency with or without oncogenic KrasG12D. Bioinformatics and gain- or loss-of-function studies were used to illustrate the mechanisms underlying oncogenic pathway alterations. Transcriptional profiling was used to identify biomarker for the subtype of HCC. The therapeutic efficacy of targeting mTOR was tested in a liver orthotropic homogeneous murine model. Results: Oncogenic KrasG12D facilitated mTOR activation via the Mek/Erk/ROS axis, leading to HCC tumorigenesis and metastasis. Inhibition of Mek/Erk enhanced the anticancer effect of mTOR inhibitor via reduction of mTOR activity. Paternally expressed 3 (PEG3) was responsible for Kras/Erk- and mTOR-driven HCC. Elevated PEG3 protein interacted with STAT3 and promoted its transcriptional activity, resulting in the upregulation of proliferation- and metastasis-related proteins. Targeting mTOR significantly inhibited these actions in vitro and in vivo. Moreover, in clinical samples, PEG3 was identified as a new poor prognostic marker for HCC patients with Kras/Erk and mTOR hyperactivation. Conclusion: These findings reveal the underlying mechanism of hepatocytic Kras/Erk-driven mTOR activation and its downstream targets (PEG3 and STAT3) in HCC, identify PEG3 as a new prognostic biomarker for HCC with Kras/Erk and mTOR hyperactivation, and provide a potential therapeutic strategy for this subset of HCC patients.

p53 haploinsufficiency and increased mTOR signalling define a subset of aggressive hepatocellular carcinoma.

BACKGROUND & AIMS: p53 mutations occur frequently in human HCC. Activation of the mammalian target of rapamycin (mTOR) pathway is also associated with HCC. However, it is still unknown whether these changes together initiate HCC and can be targeted as a potential therapeutic strategy. METHODS: We generated mouse models in which mTOR was hyperactivated by loss of tuberous sclerosis complex 1 (Tsc1) with or without p53 haplodeficiency. Primary cells were isolated from mouse livers. Oncogenic signalling was assessed in vitro and in vivo, with or without targeted inhibition of a single molecule or multiple molecules. Transcriptional profiling was used to identify biomarkers predictive of HCC. Human HCC materials were used to corroborate the findings from mouse models. RESULTS: p53 haploinsufficiency facilitates mTOR signalling via the PTEN/PI3K/Akt axis, promoting HCC tumorigenesis and lung metastasis. Inhibition of PI3K/Akt reduced mTOR activity, which effectively enhanced the anticancer effort of an mTOR inhibitor. ATP-binding cassette subfamily C member 4 (Abcc4) was found to be responsible for p53 haploinsufficiency- and Tsc1 loss-driven HCC tumorigenesis. Moreover, in clinical HCC samples, Abcc4 was specifically identified an aggressive subtype. The mTOR inhibitor rapamycin significantly reduced hepatocarcinogenesis triggered by Tsc1 loss and p53 haploinsufficiency in vivo, as well as the biomarker Abcc4. CONCLUSIONS: Our data advance the current understanding of the activation of the PTEN/PI3K/Akt/mTOR axis and its downstream target Abcc4 in hepatocarcinogenesis driven by p53 reduction and Tsc1 loss. Targeting mTOR, an unexpected vulnerability in p53 (haplo)deficiency HCC, can be exploited therapeutically to treat Abcc4-positive patients with HCC. LAY SUMMARY: Tsc1 loss facilitates the p53 (haplo)insufficiency-mediated activation of the PTEN/Akt/mTOR axis, leading to the elevated expression of Abcc4 to drive HCC tumorigenesis and metastasis in mice. Inhibition of mTOR protects against p53 haploinsufficiency and Tsc1 loss-triggered tumour-promoting activity, providing a new approach for treating an aggressive subtype of HCC exhibiting high Abcc4 expression.

Reduced IκBα promotes hepatocellular carcinoma cell proliferation and migration via regulation of NF-κB/Erbin axis.

Aberrantly low expression of NF-κB inhibitor α (IκBα) is observed in hepatocellular carcinoma (HCC), yet the underlying mechanism via which IκBα regulates HCC remains largely unknown. Therefore, to determine the potential function of IκBα in hepatocarcinogenesis, the present study used immunohistochemistry (IHC) staining to analyze the associations between IκBα protein expression and clinicopathologic characteristics of 107 patients with HCC. It was found that expression of IκBα was significantly associated with tumor recurrence. Moreover, IκBα protein expression was decreased in 107 HCC tissue samples and was positively associated with overall survival. Mechanistically, it was demonstrated that silencing of IκBα activated NF-κB in both Huh7 and HCCLM3 cells, followed by upregulation of Erbb2 interacting protein (Erbin) at both the mRNA and protein levels, confirmed by reverse transcription-quantitative PCR and western blotting, to promote cell proliferation and migration. Furthermore, knockdown of Erbin significantly attenuated NF-κB-mediated cell proliferation and migration. It was also identified that overexpression of Erbin in HCC tissues promoted both cell proliferation and migration, and was negatively associated with IκBα expression in 107 HCC tissue samples. Thus, these results indicated that downregulation of IκBα promoted HCC tumorigenesis via upregulation of NF-κB-mediated Erbin expression.

Prognostic and predicted significance of Ubqln2 in patients with hepatocellular carcinoma.

PURPOSE: Hepatocellular carcinoma (HCC) is a common malignant cancer and the third leading cause of death worldwide. The molecular mechanism of HCC remains unclear. Recent studies have demonstrated that the ubiquitin-proteasome system (UPS) is associated with HCC. Ubqln2, a member of the UPS, is abnormally expressed in HCC. However, whether Ubqln2 is associated with HCC prognosis remains unknown. PATIENTS AND METHODS: We analyzed the associations between overall survival and various risk factors in 355 HCC tissue samples obtained from the Cancer Genomic Atlas (TCGA) database at the mRNA level and in 166 HCC tissue samples from Southwest Hospital at the protein level. qRCR was used to determinate Ubqln2 expression in cancer and noncancerous tissues. The association between Ubqln2 and Ki-67 was analyzed by immunohistochemistry. The association between Ubqln2 expression and survival was analyzed using Kaplan-Meier curve and Cox proportional hazards models. A nomogram was used to predict the impact of Ubqln2 on prognosis. Mutated genes were analyzed to determine the potential mechanism. RESULTS: Ubqln2 highly expressed in HCC tissues. The Ubqln2 mRNA level had significant relations with UICC tumor stage (P = .022), UICC stage (P = .034) and resection potential (P = .017). Concordantly, the Ubqln2 protein was closely associated with tumor size (P = .005), UICC stage (P = .012), and recurrence (P = .009). Ubqln2 was highly expressed in HCC and positively associated with poor survival. The nomogram precisely predicted the prognosis of HCC patients with high or low Ubqln2 expression. A genomic waterfall plot suggested that Ubqln2 expression was closely associated with mutated CTNNB1. CONCLUSION: Our findings reveal that Ubqln2, an independent risk factor for HCC, is a potential prognostic marker in HCC patients. Ubqln2 expression is positively associated with mutated CTNNB1.

FBXW10 promotes hepatocarcinogenesis in male patients and mice.

Hepatocellular carcinoma (HCC) is reported to associate with abnormal expression of SCF E3 ubiquitin ligases. FBXW10, an F-box protein of the E3 ubiquitin ligases, was abnormally regulated in HCC patients. However, whether FBXW10 is associated with HCC has not yet been evaluated. Here, we analyzed the associations between overall survival and various risk factors in 191 HCC tissues. Univariate and multivariate analyses demonstrated that FBXW10 was an independent risk factor related to HCC prognosis. The results showed that FBXW10, gender and tumor state were strongly associated with overall survival in HCC patients. Furthermore, high expression of FBXW10 was associated with poor survival among male HCC patients but not female HCC patients. FBXW10 was more highly expressed in male HCC tissues and more strongly related to vascular invasion in male HCC patients. Consistent with these findings, the male FBXW10-Tg(+) mice were more susceptible to tumorigenesis, changes in regenerative capacity, and liver injury and inflammation but not changes in liver function than FBXW10-Tg(-) mice. FBXW10 promoted cell proliferation and migration in HCC cell lines. Our findings reveal that FBXW10, an independent risk factor for HCC, promotes hepatocarcinogenesis in male patients, and is also a potential prognostic marker in male patients with HCC.