Novel Therapeutic Target For Hepatocellular Carcinoma Research Articles

Elevated FOXC2 Expression Promotes Invasion of HCC Cell Lines and is Associated with Poor Prognosis in Hepatocellular Carcinoma

Background/Aims: Increasing evidence has indicated that Forkhead box protein C2 (FOXC2) plays an important role in carcinogenesis. However, the expression and the role of FOXC2 in hepatocellular carcinoma (HCC) have not been extensively studied. Methods: FOXC2 expression was analyzed by quantitative real-time polymerase chain reaction, Western blot analysis and immunohistochemistry in HCC tissue and cells. The relationship between FOXC2 expression and patient clinical significance and survival were assessed by Pearson’s correlation and Kaplan-Meier analysis, respectively. Cell proliferation assays, colony formation assays, flow cytometric analysis and Transwell assays were employed to measure the effects of FOXC2 on HCC cells in vitro. Results: The expression of FOXC2 was increased in HCC tissue, and high FOXC2 expression was associated with worse patient survival. Knockdown of FOXC2 inhibited HCC cell growth, migration, and invasion in vitro, as well as tumor growth. Furthermore, we found that activation of AKT-mediated MMP-2 and MMP-9 was involved in FOXC2 promoting an aggressive phenotype. Conclusions: Taken together, these findings demonstrate that FOXC2 is upregulated in HCC tissue and is associated with tumor size, vascular invasion and advanced TNM stage. Further investigation suggested that FOXC2 may play a vital role in promoting proliferation and invasion in HCC and serves as a novel therapeutic target in HCC.

Eg5 Overexpression Is Predictive of Poor Prognosis in Hepatocellular Carcinoma Patients.

Eg5 (kinesin spindle protein) plays an essential role in mitosis. Inhibition of Eg5 function results in cell cycle arrest at mitosis, which leads to cell death. To date, Eg5 expression and its prognostic significance have not been studied in hepatocellular carcinoma (HCC). In this study, 26 freshly frozen HCC tissue samples and matched peritumoral tissue samples were evaluated with a one-step qPCR test and immunohistochemical (IHC) analysis was conducted on 156 HCC samples to investigate the relationships among Eg5 expression, clinicopathological factors, and prognosis. Eg5 mRNA and protein expression levels were significantly higher in HCC tissues relative to matched noncancerous tissues (p < 0.05). High Eg5 protein expression was significantly related to liver cirrhosis (p = 0.038) and TNM stage (p = 0.008). Kaplan-Meier survival and Cox regression analyses revealed that Eg5 overexpression (p = 0.001), liver cirrhosis (p = 0.009), and TNM stage (p = 0.025) were independent prognostic factors for overall survival. These findings indicate that Eg5 expression can be used as a biomarker of poor prognosis and as a novel therapeutic target for HCC.

MicroRNA-340 inhibits the proliferation and invasion of hepatocellular carcinoma cells by targeting JAK1

Increasing evidence indicates that dysregulation of microRNAs (miRNAs) contributes to tumorigenesis. MicroRNA-340 (miR-340) is downregulated in several types of cancer. However, the functional mechanism of miR-340 in hepatocellular carcinoma (HCC) remains unclear. Here, we showed that miR-340 was significantly downregulated in HCC tissues and cell lines. Gain-of-function experiments demonstrated that miR-340 overexpression inhibited HCC cell proliferation, migration, and invasion in vitro, and suppressed tumor growth in vivo. Janus kinase 1 (JAK1) was identified as a direct target of miR-340 in HCC cells. Ectopic expression of JAK1 reversed the inhibitory effects of miR-340. Further investigations showed that miR-340 dramatically inhibited the expression of signal transducer and activator of transcription (STAT)3 downstream molecules including Bcl-2, cyclin D1, and matrix metalloprotease (MMP)-2. The present findings indicated that miR-340 suppressed HCC cell proliferation and invasion by regulating the JAK1/STAT3 pathway, suggesting its potential as a novel therapeutic target for HCC.

Oncogenic function of Plac1 on the proliferation and metastasis in hepatocellular carcinoma cells.

Placenta-specific protein 1 (Plac1), which is selectively expressed in the placental syncytiotrophoblast in adult normal tissues, plays an essential role in normal placental and embryonic development. Accumulating evidence suggests that enhanced Plac1 expression is closely associated with the progression of human cancer. Whether Plac1 contributes to the pathophysiology of hepatocellular carcinoma (HCC) remains unclear. In the present study, our data revealed that the expression of Plac1 in human HCC tissues was upregulated, which significantly correlated with metastasis of HCC. Knockdown of Plac1 by small interfering RNA (siRNA) in Bel-7402 and HepG2 cells resulted in decreasing tumor cell proliferation and increasing apoptosis, which implied the oncogenic potential of Plac1. Moreover, silencing of Plac1 induced G1 cell cycle arrest through suppression of cyclinD1 and CDK4 expression. Furthermore, depletion of Plac1 repressed epithelial-mesenchymal transition (EMT), with decreased cell migration and invasion, supporting upregulated E-cadherin expression and downregulated vimentin, twist and snail expression that characterize EMT. Further study suggested that decreased Plac1 expression attenuated the phosphorylation of Akt. These findings have uncovered that Plac1 plays a pivotal role in the progression of HCC, and may serve as a novel therapeutic target for HCC.

Therapeutic inhibition of phospholipase D1 suppresses hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents a leading cause of deaths worldwide. Novel therapeutic targets for HCC are needed. Phospholipase D (PD) is involved in cell proliferation and migration, but its role in HCC remains unclear. In the present study, we show that PLD1, but not PLD2, was overexpressed in HCC cell lines (HepG2, Bel-7402 and Bel-7404) compared with the normal human L-02 hepatocytes. PLD1 was required for the proliferation, migration and invasion of HCC cells without affecting apoptosis and necrosis, and PLD1 overexpression was sufficient to promote those effects. By using HCC xenograft models, we demonstrated that therapeutic inhibition of PLD1 attenuated tumour growth and epithelial-mesenchymal transition (EMT) in HCC mice. Moreover, PLD1 was found to be highly expressed in tumour tissues of HCC patients. Finally, mTOR (mechanistic target of rapamycin) and Akt (protein kinase B) were identified as critical pathways responsible for the role of PLD1in HCC cells. Taken together, the present study indicates that PLD1 activation contributes to HCC development via regulation of the proliferation, migration and invasion of HCC cells, as well as promoting the EMT process. These observations suggest that inhibition of PLD1 represents an attractive and novel therapeutic modality for HCC.

Downregulation of miRNA-638 promotes angiogenesis and growth of hepatocellular carcinoma by targeting VEGF.

The expression and function of microRNA-638 (miR-638) in hepatocellular carcinoma (HCC) remained unknown. Using the miRNA target prediction tools, we predicted that the vascular endothelial growth factor (VEGF) might be a direct target of miR-638. The aim of this study was to test the hypothesis that downregulation of miRNA-638 promotes angiogenesis and growth of HCC by targeting the VEGF signaling pathway. We found that miR-638 was significantly downregulated in HCC cells and clinical HCC specimens, and miR-638 levels were inversely correlated with tumor size, portal vein invasion and poor prognosis. Overexpression of miR-638 inhibited the processes of tumor angiogenesis in vitro and in vivo. The xenograft mouse model experiments showed miR-638 repressed tumor growth of HCC in vivo. Using a luciferase reporter assay, we identified VEGF as a direct target of miR-638. Subsequent investigation revealed that miR-638 expression was inversely correlated with VEGF expression in human HCC samples. Taken together, these results suggested that miR-638 is a novel therapeutic target for HCC and overexpression of miR-638 could suppress angiogenesis and tumor growth of HCC by inhibiting VEGF signaling.

Extracellular signal-regulated kinase 1 and 2 in cancer therapy: a focus on hepatocellular carcinoma.

Extracellular signal-regulated kinases (ERK) pathway plays a crucial role in cancer cell survival and proliferation. This signaling pathway has been related to epithelial to mesenchymal transition and drug resistance in hepatocellular carcinoma (HCC) cells, which is a common challenge in chemotherapy. Consequently, mediators of this pathway have recently been considered as novel therapeutic targets in HCC. In this review the impact of ERK1 and ERK2 as major components of ERK signaling pathway, in HCC biology and drug resistance will be highlighted and discussed.

MicroRNA-548a-5p promotes proliferation and inhibits apoptosis in hepatocellular carcinoma cells by targeting Tg737.

To investigate whether Tg737 is regulated by microRNA-548a-5p (miR-548a-5p), and correlates with hepatocellular carcinoma (HCC) cell proliferation and apoptosis. Assays of loss of function of Tg737 were performed by the colony formation assay, CCK assay and cell cycle assay in HCC cell lines. The interaction between miR-548a-5p and its downstream target, Tg737, was evaluated by a dual-luciferase reporter assay and quantitative real-time polymerase chain reaction. Tg737 was then up-regulated in HCC cells to evaluate its effect on miR-548a-5p regulation. HepG2 cells stably overexpressing miR-548a-5p or miR-control were also subcutaneously inoculated into nude mice to evaluate the effect of miR-548a-5p up-regulation on in vivo tumor growth. As the final step, the effect of miR-548a-5p on the apoptosis induced by cisplatin was evaluated by flow cytometry. Down-regulation of Tg737, which is a target gene of miR-548a-5p, accelerated HCC cell proliferation, and miR-548a-5p promoted HCC cell proliferation in vitro and in vivo. Like the down-regulation of Tg737, overexpression of miR-548a-5p in HCC cell lines promoted cell proliferation, increased colony forming ability and hampered cell apoptosis. In addition, miR-548a-5p overexpression increased HCC cell growth in vivo. MiR-548a-5p down-regulated Tg737 expression through direct contact with its 3' untranslated region (UTR), and miR-548a-5p expression was negatively correlated with Tg737 levels in HCC specimens. Restoring Tg737 (without the 3'UTR) significantly hampered miR-548a-5p induced cell proliferation, and rescued the miR-548a-5p induced cell proliferation inhibition and apoptosis induced by cisplatin. MiR-548a-5p negatively regulates the tumor inhibitor gene Tg737 and promotes tumorigenesis in vitro and in vivo, indicating its potential as a novel therapeutic target for HCC.

Mus81 knockdown improves chemosensitivity of hepatocellular carcinoma cells by inducing S-phase arrest and promoting apoptosis through CHK1 pathway.

As a critical endonuclease in DNA repair, Mus81 is traditionally regarded as a tumor suppressor, but recently correlated with the sensitivity of mitomycin C and 5-fluorouracil in colon cancer and breast cancer cells. However, its role in chemosensitivity of other human malignancies still remains unknown. This study therefore aims to investigate the effects of Mus81 knockdown on the chemosensitivity of hepatocellular carcinoma (HCC), a usually chemorefractory tumor, and explore the underlying mechanisms. Mus81 expression in HepG2 and Bel-7402 HCC cell lines was depleted by lentivirus-mediated short hairpin RNA and the elevated sensitivity of these Mus81-inhibited HCC cells to therapeutic agents, especially to epirubicin (EPI), was evidenced by MTT assay and an HCC chemotherapy mouse model. Flow cytometric analysis also showed that Mus81 knockdown lead to an obvious S-phase arrest and an elevated apoptosis in EPI-treated HepG2 and Bel-7402 cells, which could be rescued by CHK1 inhibition. The activation of CHK1/CDC25A/CDK2 pathway was also demonstrated in Mus81-inhibited HepG2 cells and xenograft mouse tumors under EPI treatment. Meanwhile, the apoptosis of HepG2 cells in response to EPI was remarkably promoted by Mus81 knockdown through activating p53/Bax/Caspase-3 pathway under the controlling of CHK1. In addition, CHK2 inhibition slightly raised CHK1 activity, thereby enhancing the S-phase arrest and apoptosis induced by EPI in Mus81-suppressed HCC cells. In conclusion, Mus81 knockdown improves the chemosensitivity of HCC cells by inducing S-phase arrest and promoting apoptosis through CHK1 pathway, suggesting Mus81 as a novel therapeutic target for HCC.

Cannabinoid WIN55, 212-2 induces cell cycle arrest and inhibits the proliferation and migration of human BEL7402 hepatocellular carcinoma cells.

Hepatocellular carcinoma (HCC) is the leading cause of cancer-associated mortality worldwide; however, only limited therapeutic treatments are currently available. The present study aimed to investigate the effects of cannabinoids as novel therapeutic targets in HCC. In addition, the mechanism underlying the effects of a synthetic cannabinoid, WIN55, 212-2, on the BEL7402 HCC cell line was investigated. The results demonstrated that WIN55, 212-2 induced cell cycle arrest of the BEL7402 cells at the G0/G1 phase via can nabinoid receptor 2 (CB2)-mediated down regulation of phosphorylated-extracellular signal-regulated kinases (ERK)1/2, upregulation of p27, and downregulation of cyclin D1 and cyclin-dependent kinase 4. Furthermore, inhibition of CB2 with the CB2 antagonist AM630 abrogated WIN55, 212-2-induced cell cycle arrest. Inhibition of ERK1/2 also resulted in cell cycle dysregulation and cell cycle arrest at the G0/G1 phase, which subsequently resulted in cell growth inhibition. In addition, the present study detected a significant reduction in matrix metalloproteinase-9, retinoblastoma protein and E2F1 expression, and migration inhibition by WIN treatment. These results suggested that cannabinoid receptor agonists, including WIN, may be considered as novel therapeutics for the treatment of HCC.

DDR2 facilitates hepatocellular carcinoma invasion and metastasis via activating ERK signaling and stabilizing SNAIL1.

BackgroundSeveral studies have found that DDR2 is up-regulated in many tumor types and facilitates tumor progression. However, the role of DDR2 in hepatocellular carcinoma (HCC) progression and its downstream signaling pathways remain unclear.MethodsDDR2 expression was assessed in several cell lines and 112 pairs of HCC and matched adjacent noncancerous liver tissues. Clinical significance of DDR2 in HCC was analyzed. Phosphorylated DDR2 (p-DDR2) expression was detected by immunoblotting to evaluate its correlation with DDR2. The effect of DDR2 on HCC cell migration and invasion were examined. Cycloheximide chase experiments were performed to detect the half-life of SNAIL1. Moreover, DDR2 expression was detected by immunohistochemistry to evaluate its correlation with SNAIL1. The regulatory effect of DDR2 on ERK signaling, SNAIL1, EMT, MT1-MMP and MMP2 was confirmed by immunoblotting. The effect of type I collagen on DDR2/ERK2/SNAIL1 signaling was assessed.ResultsDDR2 was more highly expressed in HCC than in non-HCC tissues. DDR2 overexpression was correlated with clinicopathological features of poor prognosis. Clinical analysis revealed that DDR2 is an independent prognostic marker for predicting overall survival and disease free survival of HCC patients. Overexpression of DDR2 is associated with p-DDR2 amplification. In vitro studies showed that DDR2 facilitates HCC cell invasion, migration and EMT via activating ERK2 and stabilizing SNAIL1. DDR2 can up-regulate MT1-MMP and MMP2 expression through ERK2/SNAIL1 signaling in HCC. Additionally, collagen I can induce DDR2/ERK2/SNAIL1 signaling activation in HCC cells.ConclusionsOur findings suggest that DDR2 plays an important role in promoting HCC cell invasion and migration, and may serve as a novel therapeutic target in HCC.

TRIM26 functions as a novel tumor suppressor of hepatocellular carcinoma and its downregulation contributes to worse prognosis

Hepatocellular carcinoma (HCC) is the one of the most common malignancies worldwide and its prognosis is extremely poor. Tripartite motif (TRIM) proteins play crucial roles in cancer cell biology but the function of tripartite motif 26 (TRIM26) has not been investigated. We demonstrated that low expression level of TRIM26 in tumor samples was significantly correlated with worse prognosis in HCC patients. We also demonstrated its expression level was associated with several clinicopathologic features such as AFP level and T stage of HCC patients. Furthermore, we validated that TRIM26 was significantly downregulated in HCC tissue compared with normal liver tissue. To further clarify the functional role of TRIM26 in HCC, We confirmed that TRIM26 silencing can promote cancer cell proliferation, colony forming, migration and invasion in vitro with HCC cell lines HepG2 and Bel-7402. Then we utilized bioinformatic tool to predict gene influenced by TRIM26, showing TRIM26 could modulate gene sets about cancer cell metabolism. In conclusion, we proved that TRIM26 is a novel tumor suppressor modulating multiple metabolism-related pathways in HCC. To our best knowledge, this is the first study to investigate the function of TRIM26 in cancer biology. Our findings provide useful insight into the mechanism of HCC origin and progression. Moreover, TRIM26 may represent a novel therapeutic target for HCC.

Sox12, a direct target of FoxQ1, promotes hepatocellular carcinoma metastasis through up-regulating Twist1 and FGFBP1.

Metastasis is the main reason for high recurrence and poor survival of hepatocellular carcinoma (HCC) after curative resection. However, the molecular mechanism underlying HCC metastasis remains unclear. Here, we report on a novel function of SRY (sex determining region Y)-box 12 (Sox12), a member of the SYR-related high mobility group box family proteins, in promoting HCC metastasis. Overexpression of Sox12 was significantly correlated with loss of tumor encapsulation, microvascular invasion, and a higher tumor-nodule-metastasis (TNM) stage and indicated poor prognosis in human HCC patients. Sox12 expression was an independent and significant risk factor for recurrence and reduced survival after curative resection. Overexpression of Sox12 induced epithelial-mesenchymal transition by transactivating Twist1 expression. Down-regulation of Twist1 decreased Sox12-enhanced HCC migration, invasion, and metastasis, whereas up-regulation of Twist1 rescued the decreased migration, invasion, and metastasis induced by Sox12 knockdown. Additionally, serial deletion, site-directed mutagenesis, and chromatin immunoprecipitation assays showed that fibroblast growth factor binding protein 1 (FGFBP1) was a direct transcriptional target of Sox12. Knockdown of FGFBP1 decreased Sox12-mediated HCC invasion and metastasis, whereas overexpression of FGFBP1 rescued the decreased invasion and metastasis induced by Sox12 knockdown. Furthermore, forkhead box Q1 (FoxQ1) directly bound to the Sox12 promoter and transactivated its expression, which contributed to Sox12 overexpression in human HCC. Knockdown of Sox12 dramatically decreased FoxQ1-mediated HCC metastasis. In two independent cohorts of human HCC tissues, Sox12 expression was positively correlated with Twist1, FGFBP1, and FoxQ1 expression, and patients with positive coexpression of Sox12/Twist1, Sox12/FGFBP1, or FoxQ1/Sox12 were associated with poorer prognosis. Up-regulated Sox12 induced by FoxQ1 promotes HCC invasion and metastasis by transactivating Twist1 and FGFBP1 expression. Thus, our study implicates Sox12 as a potential prognostic biomarker and a novel therapeutic target for HCC.

ZEB2 promotes vasculogenic mimicry by TGF-β1 induced epithelial-to-mesenchymal transition in hepatocellular carcinoma

AimsZinc finger E-box binding homeobox 2 (ZEB2), an epithelial–mesenchymal transition (EMT) regulator, has been involved in invasion and metastasis of human tumor. Although EMT may be involved in vasculogenic mimicry (VM) formation, no reports describing the relation between ZEB2 and VM are available. We hypothesize that ZEB2 may promote VM formation in hepatocellular carcinoma (HCC). Methods and resultsParaffin-embedded tumor tissue samples from 92 patients were immunostained with anti-ZEB2 antibody. We found that the ZEB2 nuclear expression was significantly associated with VM formation and metastasis. Patients with VM and ZEB2 nuclear expression had a shorter survival period than those without expression. In vitro, ZEB2 overexpression significantly enhanced cell motility, invasiveness, and VM formation of HepG2 cells. ZEB2 upregulation also increased VE-cadherin, Flt-1, and Flk-1 expression and activated MMPs. ZEB2 knockdown inhibited cell motility, invasiveness, and VM formation in Bel7402 cells. ZEB2 knockdown also decreased VE-cadherin, Flt-1, and Flk-1 expression and MMP activity. In addition, EMT in HepG2 cells was induced by TGF-β1 treatment, and the kinetics of expression of EMT markers and regulators were assessed by Western blot analysis. The expression of ZEB2 increased significantly, and VM formation was promoted. ConclusionZEB2 can promote VM formation through the EMT pathway. Our findings may represent a novel therapeutic target in HCC.

Knockdown of autophagy-related gene LC3 enhances the sensitivity of HepG2 cells to epirubicin

Hepatocellular carcinoma (HCC) is a major public health problem. Despite new chemotherapeutic treatments, drug resistance remains a major clinical obstacle to successful treatment in HCC patients. Therefore, novel therapeutic targets and new modalities of treatment are urgently required. In this study, tetracycline-inducible lentivirus-mediated RNA interference (RNAi) was employed to knock down microtubule-associated protein 1 light chain 3 (LC3) gene, which encodes a key protein in the induction of autophagy, to study the protective function of autophagy in liver cancer tolerant to epirubicin. The effect of combined treatment with lentiviral shLC3 and epirubicin on cell growth and chemosensitivity to epirubicin in the HCC cell line HepG2 were also investigated. The results demonstrated that lentivirus-mediated LC3 silencing significantly inhibited cell proliferation. In addition, combined treatment with lentiviral shLC3 and epirubicin significantly decreased the survival rate of HepG2 cells, compared with that following treatment with either agent alone. Overall, the results from this study suggest for the first time, to the best of our knowledge, that LC3 plays a key role in HCC tumorigenesis, and is a novel therapeutic target for HCC.

MiR-148b suppresses cell proliferation and invasion in hepatocellular carcinoma by targeting WNT1/β-catenin pathway.

Accumulating evidences indicate that microRNAs play a vital role in regulating tumor progression. However, the roles of miR-148b in hepatocellular carcinoma (HCC) are still largely unknown. In this study, our data showed that miR-148b was significantly downregulated in 40 pairs of human HCC tissues. Further, the deregulated miR-148b was significantly correlated with larger tumor size, more tumor number, metastasis and worse prognosis in HCC. Overexpression of miR-148b inhibited HCC HepG2 cells proliferation and tumorigenicity. Further, miR-148b induced cells apoptosis by activating caspase- 3 and caspase-9, and induced S phase arrest by regulating cyclinD1 and p21, and also inhibited cell invasion. Data from the dual-luciferase reporter gene assay showed that WNT1 was a direct target of miR-148b, and overexpressed WNT1 inversely correlated with miR-148b levels in HCC tissues. Silencing of WNT1 inhibited the growth of HCC cells, and also induced cells apoptosis and inhibited invasion, which is consistent with the effects of miR-148b overexpression. MiR-148b downregulated expression of WNT1, β-catenin and C-myc, while upregulated E-cadherin expression. We conclude that the frequently downregulated miR-148b can regulate WNT1/β-catenin signalling pathway and function as a tumor suppressor in HCC. These findings suggest that miR-148b may serve as a novel therapeutic target for HCC.

AGK enhances angiogenesis and inhibits apoptosis via activation of the NF-κB signaling pathway in hepatocellular carcinoma.

High levels of angiogenesis and resistance to apoptosis are major clinical features of hepatocellular carcinoma (HCC), a lethal disease with a high incidence worldwide. However, the precise mechanisms underlying these malignant properties remain unclear. Here, we demonstrated that acylglycerol kinase (AGK) is markedly overexpressed in HCC cell lines and clinical tissues. Immunohistochemical analysis of 245 clinical HCC specimens revealed patients with high levels of AGK expression had poorer overall survival compared to patients with low AGK expression. Furthermore, overexpressing AGK significantly enhanced angiogenesis and inhibited apoptosis in vitro and promoted the tumorigenicity of HCC cells in vivo; silencing endogenous AGK had the opposite effects. Importantly, AGK enhanced angiogenesis and inhibited apoptosis in HCC in part via activation of NF-κB signaling. Our findings provide new evidence that AGK plays an important role in promoting angiogenesis and providing resistance to apoptosis, thus AGK may represent a novel therapeutic target for HCC.

NF-κB increased expression of 17β-hydroxysteroid dehydrogenase 4 promotes HepG2 proliferation via inactivating estradiol

Hepatocellular carcinoma (HCC) arises in a setting of chronic inflammation induced by inflammatory cytokines, such as nuclear factor-kappaB (NF-κB). HCC is a male-predominant cancer that can be attenuated by estradiol (E2) in vitro and in vivo. Although 17β-hydroxysteroid dehydrogenase 4 (HSD17B4) has been implicated as an estradiol-inactivating enzyme, and its promoter sequence contains two putative NF-κB elements: it is currently unknown whether HSD17B4 is the link between inflammation, estradiol and proliferation in hepatoma cells. In this study, HepG2 cells were used to investigate the role of HSD17B4 in the proliferation of liver cancer cells treated with the NF-κB activator, tumor necrosis factor-alpha (TNF-α), with the inhibitor of NF-κB activation, pyrrolidinedithiocarbamate (PDTC), or with a related specific siRNA. We demonstrated that the human HSD17B4 gene is a target for NF-κB activation in inflammation-stimulated HepG2 cells. HSD17B4 is up-regulated via the binding of activated NF-κB to the distal NF-κB-responsive element via TNF-α stimulation, which then promotes cell proliferation by decreasing the levels of E2 and enhancing the expression of interleukin 6 (IL-6), cyclin D1 and proliferating cell nuclear antigen (PCAN). These results from HepG2 cells are consistent with the observation that HSD17B4 is highly expressed and activated NF-κB is highly co-localized with the NF-κB-responsive element of HSD17B4 in liver tumor tissues from HCC patients. Our findings indicate for the first time that HSD17B4 plays an important role in aggravated HCC progression and provides a novel therapeutic target for HCC.

Regulation of cell cycle of hepatocellular carcinoma by NF90 through modulation of cyclin E1 mRNA stability.

Activation of cyclin E1, a key regulator of the G1/S cell-cycle transition, has been implicated in many cancers including hepatocellular carcinoma (HCC). Although much is known about the regulation of cyclin E1 expression and stability, its post-transcriptional regulation mechanism remains incompletely understood. Here, we report that nuclear factor 90 (NF90), a double-stranded RNA (dsRNA) binding protein, regulates cyclin E1 in HCC. We demonstrate that NF90 is upregulated in HCC specimens and that suppression of NF90 decreases HCC cell growth and delays G1/S transition. We identified cyclin E1 as a new target of NF90 and found a significant correlation between NF90 and cyclin E1 expression in HCC. The mRNA and protein levels of cyclin E1 were downregulated upon NF90 knockdown. Suppression of NF90 caused a decrease in the half-life of cyclin E1 mRNA, which was rescued by ectopic expression of NF90. Furthermore, NF90 bound to the 3' untranslated regions (3'UTRs) of cyclin E1 mRNA in vitro and in vivo. Knockdown of NF90 also inhibited tumor growth of HCC cell lines in mouse xenograft model. Moreover, we showed that inhibition of NF90 sensitized HCC cells to the cyclin-dependent kinase 2 (CDK2) inhibitor, roscovitine. Taken together, downregulation of NF90 in HCC cell lines can delay cell-cycle progression, inhibit cell proliferation, and reduce tumorigenic capacity in vivo. These results suggest that NF90 has an important role in HCC pathogenesis and that it can serve as a novel therapeutic target for HCC.

Long non-coding RNAs: critical players in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a complex disease with multiple underlying pathogenic mechanisms caused by a variety of etiologic factors. Emerging evidence showed that long non-coding RNAs (lncRNAs), with size larger than 200 nucleotides (nt), play important roles in various types of cancer development and progression. In recent years, some dysregulated lncRNAs in HCC have been revealed and roles for several of them in HCC have been characterized. All these findings point to the potential of lncRNAs as prospective novel therapeutic targets in HCC. In this review, we summarize known dysregulated lncRNAs in HCC, and review potential biological roles and underlying molecular mechanisms of lncRNAs in HCC. Additionally, we discussed prospects of lncRNAs as potential biomarker and therapeutic target for HCC. In conclusion, this paper will help us gain better understanding of molecular mechanisms by which lncRNAs perform their function in HCC and also provide general strategies and directions for future research.