Involvement of MAFB and MAFF in Retinoid-Mediated Suppression of Hepatocellular Carcinoma Invasion

Tissue factor pathway inhibitor-2 (TFPI-2)-an underappreciated partaker in cancer and metastasis

The coagulation system is known to play an important role in cancer development and metastasis, but the precise mechanisms by which it does so remain incompletely understood. With this in mind, we provide an updated overview of the effects of TFPI-2, a protease inhibitor, on cancer development and metastasis. TFPI-2 interacts with the thrombin cascade and also employs other mechanisms to suppress cancer growth and dissemination, which include extracellular matrix stabilization, promotion of caspase-mediated cell apoptosis, inhibition of angiogenesis and transduction of intracellular signals. Down-regulation of TFPI-2 expression is well documented in numerous types of neoplasms, mainly via promoter methylation. However, the exact role of TFPI-2 in cancer progression and possible approaches to up-regulate TFPI-2 expression warrant further studies. Strategies to reactivate TFPI-2 may represent a promising direction for future anticancer studies and therapy development.

The role and regulation of Maf proteins in cancer

The Maf proteins (Mafs) belong to basic leucine zipper transcription factors and are members of the activator protein-1 (AP-1) superfamily. There are two subgroups of Mafs: large Mafs and small Mafs, which are involved in a wide range of biological processes, such as the cell cycle, proliferation, oxidative stress, and inflammation. Therefore, dysregulation of Mafs can affect cell fate and is closely associated with diverse diseases. Accumulating evidence has established both large and small Mafs as mediators of tumor development. In this review, we first briefly describe the structure and physiological functions of Mafs. Then we summarize the upstream regulatory mechanisms that control the expression and activity of Mafs. Furthermore, we discuss recent studies on the critical role of Mafs in cancer progression, including cancer proliferation, apoptosis, metastasis, tumor/stroma interaction and angiogenesis. We also review the clinical implications of Mafs, namely their potential possibilities and limitations as biomarkers and therapeutic targets in cancer.

Involvement of hedgehog signaling in all-trans retinoic acid-mediated suppression of colon cancer

All-trans retinoic acid (ATRA) exerts tumor-inhibitory effects on acute leukemia and certain types of solid tumors. This study was designed to evaluate the mechanism on ATRA-mediated suppression of colon cancer based on the sonic hedgehog (Shh) signaling pathway.

METHODS

Normal intestinal epithelial cells and three colon cancer cell lines were studied to evaluate the inhibitory effect of ATRA on tumor cell activity. The inhibitory effect of ATRA on colon cancer was evaluated by cell invasion, migration, and apoptosis of HCT116 cells. Retinoic acid receptor (RAR)- and Shh-related protein expression was assessed.

RESULTS

ATRA administration inhibited the activity of three different colon cancer lines, but did not inhibit the activity of normal intestinal epithelial cells. Administration of ATRA induced apoptosis and restricted invasion and migration of HCT116 colon cancer cells. Administration of ATRA also increased expression of RAR and transmembrane receptor patched 1 (Ptch1), and decreased expression of the smoothened (Smo) and glioma-associated oncogene homolog1 (Gli-1). RAR_α and RAR_β agonists inhibited Shh signaling, and the mediating effect of ATRA on Shh signaling was abolished by RAR_α or RAR_β antagonists. The combination of purmorphamine (Smo agonist) and ATRA partially abolished the inhibitory effect of ATRA on the proliferation of colon cancer cells. In vivo studies showed that ATRA inhibited tumor growth, which was accompanied by down-regulation of the Shh signaling pathway.

CONCLUSIONS

ATRA inhibits the growth of colon cancer by downregulating the Shh pathway, which further verifies the anticancer activity of ATRA.

CircRNA ITCH: Insight Into Its Role and Clinical Application Prospect in Tumor and Non-Tumor Diseases

CircRNA E3 ubiquitin protein ligase (ITCH) (circRNA ITCH, circ-ITCH), a stable closed-loop RNA derived from the 20q11.22 region of chromosome 20, is a new circRNA discovered in the cytoplasm in recent decades. Studies have shown that it does not encode proteins, but regulates proteins expression at different levels. It is down-regulated in tumor diseases and is involved in a number of biological activities, including inhibiting cell proliferation, migration, invasion, and promoting apoptosis. It can also alter disease progression in non-tumor disease by affecting the cell cycle, inflammatory response, and critical proteins. Circ-ITCH also holds a lot of promise in terms of tumor and non-tumor clinical diagnosis, prognosis, and targeted therapy. As a result, in order to aid clinical research in the hunt for a new strategy for diagnosing and treating human diseases, this study describes the mechanism of circ-ITCH as well as its clinical implications.

Integration of chronological omics data reveals mitochondrial regulatory mechanisms during the development of hepatocellular carcinoma

Mitochondria participate in multiple functions in eukaryotic cells. Although disruption of mitochondrial function has been associated with energetic deregulation in cancer, the chronological changes in mitochondria during cancer development remain unclear. With the aim to assess the role of mitochondria throughout cancer development, we analyzed samples chronologically obtained from induced hepatocellular carcinoma (HCC) in rats. In our analyses, we integrated mitochondrial proteomic data, mitochondrial metabolomic data and nuclear genome transcriptomic data. We used pathway over-representation and weighted gene co-expression network analysis (WGCNA) to integrate expression profiles of genes, miRNAs, proteins and metabolite levels throughout HCC development. Our results show that mitochondria are dynamic organelles presenting specific modifications in different stages of HCC development. We also found that mitochondrial proteomic profiles from tissues adjacent to nodules or tumor are determined more by the stage of HCC development than by tissue type, and we evaluated two models to predict HCC stage of the samples using proteomic profiles. Finally, we propose an omics integration pipeline to massively identify molecular features that could be further evaluated as key regulators, biomarkers or therapeutic targets. As an example, we show a group of miRNAs and transcription factors as candidates, responsible for mitochondrial metabolic modification in HCC.

The underlying molecular mechanism and identification of transcription factor markers for laryngeal squamous cell carcinoma

The screening and treatment of laryngeal squamous cell carcinoma (LSCC) still perplexes clinicians, making it necessary to explore new markers. To this end, this research examined the underlying molecular mechanism of LSCC based on high-throughput datasets (n = 249) from multiple databases. It also identified transcription factors (TFs) independently associated with LSCC prognosis. Through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, differential expression genes of LSCC were deemed relevant to the extracellular matrix and its related structures or pathways, suggesting that the extracellular matrix plays an important role in LSCC. At the same time, several hub genes that may also have important roles in LSCC were identified via protein–protein interaction analysis, including CDC45, TPX2, AURKA, KIF2C, NUF, MUC1, MUC7, MUC4, MUC15, and MUC21. Eight unreported LSCC prognostic TFs – BCAT1, CHD4, FOXA2, GATA6, HNF1A, HOXB13, MAFF, and TCF4 – were screened via Kaplan–Meier curves. Cox analysis determined for the first time that HOXB13 expression and gender were independently associated with LSCC prognosis. Compared to control tissues, elevated expression of HOXB13 was found in LSCC tissues (standardized mean difference = 0.44, 95% confidence interval [0.13–0.76]). HOXB13 expression also makes it feasible to screen LSCC from non-LSCC (area under the curve = 0.77), and HOXB13 may play an essential role in LSCC by regulating HOXB7. In conclusion, HOXB13 may be a novel marker for LSCC clinical screening and treatment.

Alternative splicing related genetic variants contribute to bladder cancer risk

Emerging evidence has shown that aberrant alternative splicing (AS) events are involved in the carcinogenesis. The association between genetic variants in AS and bladder cancer susceptibility remains to be fully elucidated. We searched for single nucleotide polymorphisms (SNPs) which are located in splicing quantitative trait loci (sQTLs) in bladder cancer through CancerSplicingQTL database and the 1000 Genomes Project. A case-control study including 580 cases and 1,101 controls was conducted to assess the association between the functional genetic variants and bladder cancer risk. Next, we used GTEx, TCGA, and GEO databases conducting sQTL analysis and gene expression differences analysis to evaluate the potential biological function of the candidate SNPs and related genes. We found that SNP rs4383 C>G was remarkably related with the reduced risk of bladder cancer (odds ratio = 0.68, 95% confidence interval = 0.59-0.79, P = 3.91 × 10^-7 ). Similar results were obtained in codominant, dominant and recessive model. Stratified analyses revealed that the effect of SNP rs4383 C>G on bladder cancer was more significant in the older subjects (age > 65), female and nonsmokers. sQTL analysis showed that SNP rs4383 was associated with the AS events of its downstream gene MAFF with a splicing event of alternative 5' splice site. The messenger RNA expression of MAFF in bladder tumor tissues was lowered compared with normal tissues. Patients with high expression of MAFF had higher survival rates. These findings indicated that SNP rs4383 related with the AS events of MAFF was associated with bladder cancer risk and could represent a possible biomarker for bladder cancer susceptibility.

The Nuclear Remodeling Induced by Helicobacter Cytolethal Distending Toxin Involves MAFB Oncoprotein

Enterohepatic Helicobacters, such as Helicobacter hepaticus and Helicobacter pullorum, are associated with several intestinal and hepatic diseases. Their main virulence factor is the cytolethal distending toxin (CDT). In the present study, whole genome microarray-based identification of differentially expressed genes was performed in vitro in HT-29 intestinal cells while following the ectopic expression of the active CdtB subunit of H. hepaticus CDT. A CdtB-dependent upregulation of the V-maf musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB) gene encoding the MAFB oncoprotein was found, as well as the CdtB-dependent regulation of several MAFB target genes. The transduction and coculture experiments confirmed MAFB mRNA and protein induction in response to CDT and its CdtB subunit in intestinal and hepatic cell lines. An analysis of MAFB protein subcellular localization revealed a strong nuclear and perinuclear localization in the CdtB-distended nuclei in intestinal and hepatic cells. MAFB was also detected at the cell periphery of the CdtB-induced lamellipodia in some cells. The silencing of MAFB changed the cellular response to CDT with the formation of narrower lamellipodia, a reduction of the increase in nucleus size, and the formation of less γH2AX foci, the biomarker for DNA double-strand breaks. Taken together, these data show that the CDT of enterohepatic Helicobacters modulates the expression of the MAFB oncoprotein, which is translocated in the nucleus and is associated with the remodeling of the nuclei and actin cytoskeleton.

WNT/β-catenin signal inhibitor IC-2-derived small-molecule compounds suppress TGF-β1-induced fibrogenic response of renal epithelial cells by inhibiting SMAD2/3 signalling

Renal fibrosis compromises kidney function, and it is a risk factor for chronic kidney disease (CKD). CKD ultimately progresses to end-stage kidney disease that can be cured only by kidney transplantation. Owing to the increasing number of CKD patients, effective treatment strategies are urgently required for renal fibrosis. TGF-β is a well-established fibrogenic factor that signals through SMAD2/3 signaling pathway. It was shown that there is a cross-talk between TGF-β/SMAD and WNT/β-catenin signaling pathways in renal tubular epithelial cells, and that a WNT/β-catenin inhibitor, ICG-001, ameliorates TGF-β1induced renal fibrosis. IC-2, a derivative of ICG-001, has been shown to potently induce hepatocyte differentiation of human mesenchymal stem cells by inhibiting WNT/β-catenin signaling. In the present study, we examined the effect of ICG-001, IC-2, and IC-2 derivatives (IC-2-506-1, IC-2-506-2, IC-2-506-3, IC-2-Ar-Cl, IC-2-OH, IC-2-OTBS, and IC-2-F) on TGF-β1-induced SMAD activation and fibrogenic response in immortalized human renal tubular epithelial HK-2 cells. All these compounds inhibited LiCl-induced WNT/β-catenin reporter activation to a similar extent, whereas ICG-001, IC-2-OTBS, and IC-2-F almost completely suppressed TGF-β1-induced SMAD reporter activation without apparent cytotoxicity. Phosphorylation of SMAD2/3 by TGF-β1 was more potently inhibited by IC-2-OTBS and IC-2-F than by ICG-001 and IC-2. IC-2-F suppressed TGF-β1-induced COL1A1 protein expression, whereas IC-2-506-1 and IC-2-OTBS suppressed TGF-β1-induced epithelial-mesenchymal transition. These results demonstrated that IC-2 derivatives suppress the TGF-β1-induced fibrogenic response of tubular epithelial cells and thus could be promising therapeutic agents for the treatment of renal fibrosis.

MafF Is Regulated via the circ-ITCH/miR-224-5p Axis and Acts as a Tumor Suppressor in Hepatocellular Carcinoma

MafF is a member of the basic leucine zipper (bZIP) transcription factor Maf family and is commonly downregulated in multiple cancers. But the expression and function of MafF in hepatocellular carcinoma (HCC) remain unclear. In this study, we investigated the relationship between endogenous MafF expression and HCC progression and explored the regulatory mechanism of MafF expression in HCC. We found that MafF decreased in HCC tissues and cells. Lentivirus-mediated MafF overexpression inhibited HCC cell proliferation and induced cell apoptosis. Bioinformatics analysis and luciferase assay identified MafF as a direct target of miR-224-5p. RNA pull-down assay demonstrated that circular RNA circ-ITCH could sponge miR-224-5p specifically in HCC. The rescue experiments further elucidated that the expression and antitumor effects of MafF could be regulated via the circ-ITCH/miR-224-5p axis. This study verified that MafF acted as a tumor suppressor in HCC and revealed the upstream regulation mechanism of MafF, which provided a new perspective for potential therapeutic targets of HCC.

HBx and c-MYC Cooperate to Induce URI1 Expression in HBV-Related Hepatocellular Carcinoma

Unconventional prefoldin RNA polymerase II subunit 5 interactor (URI1) has emerged as an oncogenic driver in hepatocellular carcinoma (HCC). Although the hepatitis B virus (HBV) represents the most common etiology of HCC worldwide, it is unknown whether URI1 plays a role in HBV-related HCC (HCC-B). In the present study, we investigated URI1 expression and its underlying mechanism in HCC-B tissues and cell lines. URI1 gene-promoter activity was determined by a luciferase assay. Human HCC-B samples were used for a chromatin immunoprecipitation assay. We found that c-MYC induced URI1 expression and activated the URI1 promoter through the E-box in the promoter region while the HBx protein significantly enhanced it. The positivity of URI1 expression was significantly higher in HCC-B tumor tissues than in non-HBV-related HCC tumor tissues, suggesting that a specific mechanism underlies URI1 expression in HCC-B. In tumor tissues from HCC-B patients, a significantly higher level of c-MYC was recruited to the E-box than in non-tumor tissues. These results suggest that HBx and c-MYC are involved in URI1 expression in HCC-B. URI1 expression may play important roles in the development and progression of HCC-B because HBx and c-MYC are well-known oncogenic factors in the virus and host, respectively.