Tissue-specific transcription factors in progression of epithelial tumors

HNF‑4α downregulation promotes tumor migration and invasion by regulating E‑cadherin in renal cell carcinoma

Renal cell carcinoma (RCC) is the most common malignant disease of the kidneys in adults. Patients with metastatic RCC have an unusually poor prognosis and exhibit resistance to all current therapies. Therefore, it is necessary to explore novel molecules involved in the progression of RCC and to identify effective therapeutic targets. Hepatocyte nuclear factor-4α (HNF-4α) serves an important role in hepatocyte differentiation and is involved in the progression of liver cancer; however, the functional role of HNF-4α has not been well established in RCC. The present study reported that HNF-4α expression was markedly downregulated in RCC tissue samples compared with in normal controls by immunohistochemistry and RNA-sequencing analysis. Statistical analysis demonstrated that HNF-4α downregulation was significantly associated with tumor stage, recurrence, metastasis and poor prognosis in patients with RCC. Furthermore, wound-healing and Transwell assays revealed that downregulation of HNF-4α promoted cell migration and invasion by transcriptionally regulating E-cadherin in RCC. Finally, a positive correlation was revealed between HNF-4α expression and E-cadherin expression, and patients with low E-cadherin expression also had a poor prognosis. These findings may provide novel insights into the biological effects of HNF-4α and lay the foundation for the discovery of molecular therapeutic targets in RCC.

Aberrant expression of alternative isoforms of transcription factors in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide and the second leading cause of death among all cancer types. Deregulation of the networks of tissue-specific transcription factors (TFs) observed in HCC leads to profound changes in the hepatic transcriptional program that facilitates tumor progression. In addition, recent reports suggest that substantial aberrations in the production of TF isoforms occur in HCC. In vitro experiments have identified distinct isoform-specific regulatory functions and related biological effects of liver-specific TFs that are implicated in carcinogenesis, which may be relevant for tumor progression and clinical outcome. This study reviews available data on the expression of isoforms of liver-specific and ubiquitous TFs in the liver and HCC and their effects, including HNF4α, C/EBPs, p73 and TCF7L2, and indicates that assessment of the ratio of isoforms and targeting specific TF variants may be beneficial for the prognosis and treatment of HCC.

VHL deficiency augments anthracycline sensitivity of clear cell renal cell carcinomas by down-regulating ALDH2

The von Hippel-Lindau (VHL) is deficient in ∼70% of clear-cell renal cell carcinomas (ccRCC), which contributes to the carcinogenesis and drug resistance of ccRCC. Here we show that VHL-deficient ccRCC cells present enhanced cytotoxicity of anthracyclines in a hypoxia-inducible factor-independent manner. By subtractive proteomic analysis coupling with RNAi or overexpression verification, aldehyde dehydrogenase 2 (ALDH2) is found to be transcriptionally regulated by VHL and contributes to enhanced anthracyclines cytotoxicity in ccRCC cells. Furthermore, VHL regulates ALDH2 expression by directly binding the promoter of −130 bp to −160 bp to activate the transcription of hepatocyte nuclear factor 4 alpha (HNF-4α). In addition, a positive correlation is found among the protein expressions of VHL, HNF-4α and ALDH2 in ccRCC samples. These findings will deepen our understanding of VHL function and shed light on precise treatment for ccRCC patients.

The VHL tumour suppressor gene is lost in approximately 70% of clear cell renal cell carcinoma (ccRCC). In this study, the authors demonstrate that VHL loss in these tumours augments anthracyclines chemotherapy by down-regulation of ALDH2.

Yes-associated protein/TEA domain family member and hepatocyte nuclear factor 4-alpha (HNF4α) repress reciprocally to regulate hepatocarcinogenesis in rats and mice

Great progress has been achieved in the study of Hippo signaling in regulating tumorigenesis; however, the downstream molecular events that mediate this process have not been completely defined. Moreover, regulation of Hippo signaling during tumorigenesis in hepatocellular carcinoma (HCC) remains largely unknown. In the present study, we systematically investigated the relationship between Yes-associated protein/TEA domain family member (YAP-TEAD) and hepatocyte nuclear factor 4-alpha (HNF4α) in the hepatocarcinogenesis of HCC cells. Our results indicated that HNF4α expression was negatively regulated by YAP1 in HCC cells by a ubiquitin proteasome pathway. By contrast, HNF4α was found to directly associate with TEAD4 to compete with YAP1 for binding to TEAD4, thus inhibiting the transcriptional activity of YAP-TEAD and expression of their target genes. Moreover, overexpression of HNF4α was found to significantly compromise YAP-TEAD-induced HCC cell proliferation and stem cell expansion. Finally, we documented the regulatory mechanism between YAP-TEAD and HNF4α in rat and mouse tumor models, which confirmed our in vitro results.

CONCLUSION

There is a double-negative feedback mechanism that controls TEAD-YAP and HNF4α expression in vitro and in vivo, thereby regulating cellular proliferation and differentiation. Given that YAP acts as a dominant oncogene in HCC and plays a crucial role in stem cell homeostasis and tissue regeneration, manipulating the interaction between YAP, TEADs, and HNF4α may provide a new approach for HCC treatment and regenerative medicine. (Hepatology 2017;65:1206-1221).

Hepatitis C virus suppresses Hepatocyte Nuclear Factor 4 alpha, a key regulator of hepatocellular carcinoma

Hepatitis C Virus (HCV) infection presents with a disturbed lipid profile and can evolve to hepatic steatosis and hepatocellular carcinoma (HCC). Hepatocyte Nuclear Factor 4 alpha (HNF4α) is the most abundant transcription factor in the liver, a key regulator of hepatic lipid metabolism and a critical determinant of Epithelial to Mesenchymal Transition and hepatic development. We have previously shown that transient inhibition of HNF4α initiates transformation of immortalized hepatocytes through a feedback loop consisting of miR-24, IL6 receptor (IL6R), STAT3, miR-124 and miR-629, suggesting a central role of HNF4α in HCC. However, the role of HNF4α in Hepatitis C Virus (HCV)-related hepatocarcinoma has not been evaluated and remains controversial. In this study, we provide strong evidence suggesting that HCV downregulates HNF4α expression at both transcriptional and translational levels. The observed decrease of HNF4α expression correlated with the downregulation of its downstream targets, HNF1α and MTP. Ectopic overexpression of HCV proteins also exhibited an inhibitory effect on HNF4α levels. The inhibition of HNF4α expression by HCV appeared to be mediated at transcriptional level as HCV proteins suppressed HNF4α gene promoter activity. HCV also up-regulated IL6R, activated STAT3 protein phosphorylation and altered the expression of acute phase genes. Furthermore, as HCV triggered the loss of HNF4α a consequent change of miR-24, miR-629 or miR-124 was observed. Our findings demonstrated that HCV-related HCC could be mediated through HNF4α-microRNA deregulation implying a possible role of HNF4α in HCV hepatocarcinogenesis. HCV inhibition of HNF4α could be sustained to promote HCC.

A double-negative feedback loop between Wnt-β-catenin signaling and HNF4α regulates epithelial-mesenchymal transition in hepatocellular carcinoma

Wnt-β-catenin signaling participates in the epithelial-mesenchymal transition (EMT) in a variety of cancers; however, its involvement in hepatocellular carcinoma (HCC) and downstream molecular events is largely undefined. HNF4α is the most prominent and specific factor maintaining the differentiation of hepatic lineage cells and a potential EMT regulator in HCC cells. However, the molecular mechanisms by which HNF4α maintains the differentiated liver epithelium and inhibits EMT have not been completely defined. In this study, we systematically explored the relationship between Wnt-β-catenin signaling and HNF4α in the EMT process of HCC cells. Our results indicated that HNF4α expression was negatively regulated during Wnt-β-catenin signaling-induced EMT through Snail and Slug in HCC cells. In contrast, HNF4α was found to directly associate with TCF4 to compete with β-catenin but facilitate transcription co-repressor activities, thus inhibiting expression of EMT-related Wnt-β-catenin targets. Moreover, HNF4α may control the switch between the transcriptional and adhesion functions of β-catenin. Overexpression of HNF4α was found to completely compromise the Wnt-β-catenin-signaling-induced EMT phenotype. Finally, we determined the regulation pattern between Wnt-β-catenin signaling and HNF4α in rat tumor models. Our studies have identified a double-negative feedback mechanism controlling Wnt-β-catenin signaling and HNF4α expression in vitro and in vivo, which sheds new light on the regulation of EMT in HCC. The modulation of these molecular processes may be a method of inhibiting HCC invasion by blocking Wnt-β-catenin signaling or restoring HNF4α expression to prevent EMT.

The role of hepatocyte nuclear factor 4alpha in metastatic tumor formation of hepatocellular carcinoma and its close relationship with the mesenchymal-epithelial transition markers

Background

Mesenchymal–epithelial transition (MET) is now suggested to participate in the process of metastatic tumor formation. However, in hepatocellular carcinoma (HCC) the process is still not well revealed.

Methods

Paraffin-embedded tissue samples were obtained from 13 patients with HCC in Shengjing Hospital of China Medical University. The expression of E-cadherin, Fibronectin, N-cadherin, Vimentin, Hepatocyte nuclear factor 4alpha (HNF4alpha), Snail and Slug was assessed in primary tumors and their corresponding metastases by immunohistochemical staining. Next, the expression of HNF4alpha and E-cadherin in four HCC cell lines was examined. Furthermore, SK-Hep-1 cells were transfected with human HNF4alpha expression vector, and the change of E-cadherin expression was assessed.

Results

45.2% (14/31) of the lesions in the metastases showed increased E-cadherin expression compared with the primaries, suggesting the possible occurrence of MET in metastatic tumor formation of HCC, as re-expression of E-cadherin is proposed to be the important hallmark of MET. The occurrence of MET was also confirmed by the reduced expression of Fibronectin (54.8%, 17/31), N-cadherin (38.7%, 12/31) and Vimentin (61.3%, 19/31) in the metastases. 45.2% (14/31) of the lesions in the metastases also showed increased HNF4alpha expression, and 67.7% (21/31) and 48.4% (15/31) of metastases showed decreased Snail and Slug expression respectively. Statistical results showed that the expression of HNF4alpha was positively related with that of E-cadherin, and negatively correlated with that of Snail, Slug and Fibronectin, suggesting that the expression change of the MET markers in the metastatic lesions might be associated with HNF4alpha. Among the four HCC cell lines, both HNF4alpha and E-cadherin expressed high in Hep3B and Huh-7 cells, but low in SK-Hep-1 and Bel-7402 cells. Furthermore, the expression of E-cadherin increased accordingly when SK-Hep-1 cells were transfected with human HNF4alpha expression vector, further confirming the role of HNF4alpha in the regulation of E-cadherin expression.

Conclusions

Our clinical observations and experimental data indicate that HNF4alpha might play a crucial role in the metastatic tumor formation of HCC, and the mechanism may be related with the process of phenotype transition.

MicroRNA-feedback loop as a key modulator of liver tumorigenesis and inflammation

A recent work of Iliopoulos et al published in Cell highlighted a circuit orchestrated by microRNAs (miRNAs) that results in liver tumorigenesis and inflammation. This feedback loop, governed by miR-24 and miR-629, promotes a hepatocyte nuclear factor-4α transient inhibition resulting in miR-124 induction and signal transducer and activator of transcription 3 activation. These promising data support the use of miRNA mimics or inhibitors as potent therapeutic approaches in liver cancer.

Divergent genomic and epigenomic landscapes of lung cancer subtypes underscore the selection of different oncogenic pathways during tumor development

For therapeutic purposes, non-small cell lung cancer (NSCLC) has traditionally been regarded as a single disease. However, recent evidence suggest that the two major subtypes of NSCLC, adenocarcinoma (AC) and squamous cell carcinoma (SqCC) respond differently to both molecular targeted and new generation chemotherapies. Therefore, identifying the molecular differences between these tumor types may impact novel treatment strategy. We performed the first large-scale analysis of 261 primary NSCLC tumors (169 AC and 92 SqCC), integrating genome-wide DNA copy number, methylation and gene expression profiles to identify subtype-specific molecular alterations relevant to new agent design and choice of therapy. Comparison of AC and SqCC genomic and epigenomic landscapes revealed 778 altered genes with corresponding expression changes that are selected during tumor development in a subtype-specific manner. Analysis of >200 additional NSCLCs confirmed that these genes are responsible for driving the differential development and resulting phenotypes of AC and SqCC. Importantly, we identified key oncogenic pathways disrupted in each subtype that likely serve as the basis for their differential tumor biology and clinical outcomes. Downregulation of HNF4α target genes was the most common pathway specific to AC, while SqCC demonstrated disruption of numerous histone modifying enzymes as well as the transcription factor E2F1. In silico screening of candidate therapeutic compounds using subtype-specific pathway components identified HDAC and PI3K inhibitors as potential treatments tailored to lung SqCC. Together, our findings suggest that AC and SqCC develop through distinct pathogenetic pathways that have significant implication in our approach to the clinical management of NSCLC.

Recombinant adenovirus carrying the hepatocyte nuclear factor-1alpha gene inhibits hepatocellular carcinoma xenograft growth in mice

Hepatocyte nuclear factor-1alpha (HNF1α) is one of the key transcription factors of the HNF family, which plays a critical role in hepatocyte differentiation. Substantial evidence has suggested that down-regulation of HNF1α may contribute to the development of hepatocellular carcinoma (HCC). Herein, human cancer cells and tumor-associated fibroblasts (TAFs) were isolated from human HCC tissues, respectively. A recombinant adenovirus carrying the HNF1α gene (AdHNF1α) was constructed to determine its effect on HCC in vitro and in vivo. Our results demonstrated that HCC cells and HCC tissues revealed reduced expression of HNF1α. Forced reexpression of HNF1α significantly suppressed the proliferation of HCC cells and TAFs and inhibited the clonogenic growth of hepatoma cells in vitro. In parallel, HNF1α overexpression reestablished the expression of certain liver-specific genes and microRNA 192 and 194 levels, with a resultant increase in p21 levels and induction of G(2)/M arrest. Additionally, AdHNF1α inhibited the expression of cluster of differentiation 133 and epithelial cell adhesion molecule and the signal pathways of the mammalian target of rapamycin and transforming growth factor beta/Smads. Furthermore, HNF1α abolished the tumorigenicity of hepatoma cells in vivo. Most interestingly, intratumoral injection of AdHNF1α significantly inhibited the growth of subcutaneous HCC xenografts in nude mice. Systemic delivery of AdHNF1α could eradicate the orthotopic liver HCC nodules in nonobese diabetic/severe combined immunodeficiency mice.

CONCLUSION

These results suggest that the potent inhibitive effect of HNF1α on HCC is attained by inducing the differentiation of hepatoma cells into mature hepatocytes and G(2)/M arrest. HNF1α might represent a novel, promising therapeutic agent for human HCC treatment. Our findings also encourage the evaluation of differentiation therapy for tumors of organs other than liver using their corresponding differentiation-determining transcription factor.

Zhx2 and Zbtb20: novel regulators of postnatal alpha-fetoprotein repression and their potential role in gene reactivation during liver cancer

The mouse alpha-fetoprotein (AFP) gene is abundantly expressed in the fetal liver, normally silent in the adult liver but is frequently reactivated in hepatocellular carcinoma. The basis for AFP expression in the fetal liver has been studied extensively. However, the basis for AFP reactivation during hepatocarcinogenesis is not well understood. Two novel factors that control postnatal AFP repression, Zhx2 and Zbtb20, were recently identified. Here, we review the transcription factors that regulate AFP in the fetal liver, as well as Zhx2 and Zbtb20, and raise the possibility that the loss of these postnatal repressors may be involved in AFP reactivation in liver cancer.

Hepatocyte nuclear factor 4 alpha suppresses the development of hepatocellular carcinoma

Hepatocyte nuclear factor 4α (HNF4α) is a transcription factor that plays a key role in hepatocyte differentiation and the maintenance of hepatic function, but its role in hepatocarcinogenesis has yet to be examined. Here, we report evidence of a suppressor role for HNF4α in liver cancer. HNF4α expression was progressively decreased in the diethylinitrosamine-induced rat model of liver carcinogenesis. In human liver tissues, HNF4α expression was decreased in cirrhotic tissue and further decreased in hepatocarcinoma relative to healthy tissue. Notably, an inverse correlation existed with epithelial-mesenchymal transition (EMT). Enforced expression of HNF4α attenuated hepatocyte EMT during hepatocarcinogenesis, alleviated hepatic fibrosis, and blocked hepatocellular carcinoma (HCC) occurrence. In parallel, stem cell marker gene expression was inhibited along with cancer stem/progenitor cell generation. Further, enforced expression of HNF4α inhibited activation of β-catenin, which is closely associated with EMT and hepatocarcinogenesis. Taken together, our results suggest that the inhibitory effect of HNF4α on HCC development might be attributed to suppression of hepatocyte EMT and cancer stem cell generation through an inhibition of β-catenin signaling pathways. More generally, our findings broaden knowledge on the biological significance of HNF4α in HCC development, and they imply novel strategies for HCC prevention through the manipulation of differentiation-determining transcription factors in various types of carcinomas.

Tight junction protein, claudin-6, downregulates the malignant phenotype of breast carcinoma

Claudin-6 is a protein component of tight junctions and its expression has been found to be undetectable or at low levels in some human and rat breast cancer cells. Here we investigated the effect of claudin-6 upregulation on the malignant phenotype of human MCF-7 breast cancer cells. MCF-7 sublines with stable claudin-6 expression were established by transfection with a pcDNA3.1-claudin-6 expressing vector. The expression of claudin-6 on mRNA and protein levels was confirmed by reverse transcription-PCR, western blot and immunofluorescent assays. Then the effects of claudin-6 on cell proliferation and cell cycle were examined by 5-diphenyl terazolium-bromide assay and flow cytometry, respectively. Colony-forming assays were used to examine two-dimensional and three-dimensional colony forming ability. Invasive and migratory traits of claudin-6 expressing cells were determined by matrigel-based Boyden chamber invasion assay and monolayer wound-healing assay. The structure and function of tight junctions in both parental and claudin-6 expression MCF-7 cells were evaluated by measuring transepithelial electrical resistance. Immunofluorescent assays showed that transfected cells expressed claudin-6 on their membranes. Cells with high level expression of claudin-6 grew slowly and had a higher rate of death than control cells. Anchorage-independent growth, invasive and migratory traits were also substantially decreased in cells with claudin-6 expression; whereas the transepithelial electrical resistance was increased in the claudin-6 transfected cells. In conclusion, these results suggest that claudin-6 may function as a cancer suppressor; its downregulation may contribute to the malignant progression of certain types of breast cancers.