Suqin Shen

Phylogenetic and evolutionary analysis of the septin protein family in metazoan

Septins, a conserved family of cytoskeletal GTP‐binding proteins, were presented in diverse eukaryotes. Here, a comprehensive phylogenetic and evolutionary analysis for septin proteins in metazoan was carried out. First, we demonstrated that all septin proteins in metazoan could be clustered into four subgroups, and the representative homologue of every subgroup was presented in the non‐vertebrate chordate Ciona intestinalis, indicating that the emergence of the four septin subgroups should have occurred prior to divergence of vertebrates and invertebrates, and the expansion of the septin gene number in vertebrates was mainly by the duplication of pre‐existing genes rather than by the appearance of new septin subgroup. Second, the direct orthologues of most human septins existed in zebrafish, which suggested that human septin gene repertoire was mainly formed by as far as before the split between fishes and land vertebrates. Third, we found that the evolutionary rate within septin family in mammalian lineage varies significantly, human SEPT1, SEPT 10, SEPT 12, and SEPT 14 displayed a relative elevated evolutionary rate compared with other septin members. Our data will provide new insights for the further function study of this protein family.

Carbonyl reductase 1 as a novel target of (-)-epigallocatechin gallate against hepatocellular carcinoma.

Human carbonyl reductase 1 (CBR1) converts the antitumor drug and anthracycline daunorubicin (DNR) into the alcohol metabolite daunorubicinol (DNROL) with significantly reduced antitumor activity and cardiotoxicity, and this limits the clinical use of DNR. Inhibition of CBR1 can thus increase the efficacy and decrease the toxicity of DNR. Here we report that (−)‐epigallocatechin gallate (EGCG) from green tea is a promising inhibitor of CBR1. EGCG directly interacts with CBR1 and acts as a noncompetitive inhibitor with respect to the cofactor reduced nicotinamide adenine dinucleotide phosphate and the substrate isatin. The inhibition is dependent on the pH, and the gallate moiety of EGCG is required for activity. Molecular modeling has revealed that EGCG occupies the active site of CBR1. Furthermore, EGCG specifically enhanced the antitumor activity of DNR against hepatocellular carcinoma SMMC7721 cells expressing high levels of CBR1 and corresponding xenografts. We also demonstrated that EGCG could overcome the resistance to DNR by Hep3B cells stably expressing CBR1 but not by RNA interference of CBR1‐HepG2 cells. The level of the metabolite DNROL was negatively correlated with that of EGCG in the cell extracts. Finally, EGCG decreased the cardiotoxicity of DNR in a human carcinoma xenograft model with both SMMC7721 and Hep3B cells in mice. Conclusion: These results strongly suggest that EGCG can inhibit CBR1 activity and enhance the effectiveness and decrease the cardiotoxicity of the anticancer drug DNR. These findings also indicate that a combination of EGCG and DNR might represent a novel approach for hepatocellular carcinoma therapy or chemoprevention. (HEPATOLOGY 2010;)

Oligo-microarray analysis reveals the role of cyclophilin A in drug resistance

Cyclophilin A (CYPA) belongs to peptidyl prolyl isomerases (PPIases), which catalyze the cis/trans isomerization of prolyl peptide bonds in cellular communication. CYPA has been implicated in several pathological processes, including cancer, inflammatory diseases, and HIV-1 infection. Up-regulation of CYPA has been found to be a common phenomenon in several tumor types, including in hepatocellular carcinoma (HCC). However, the role of CYPA in tumor cells remains unknown. We generated a stable SK-Hep1 cell line and studied the CYPA regulated genes at the transcriptome level. The microarray results reveal that CYPA can up-regulate the expression of many cytokine and drug resistance related genes. Furthermore, we showed that the elevated CYPA expression contributes to drug resistance. We postulate that the over-expression of CYPA in tumors may play a role in clinical resistance to chemotherapy.

MDM2 SNP309T>G Polymorphism with Hepatocellular Carcinoma Risk: A Meta-analysis

BACKGROUND AND AIMS The murine double minute 2 (MDM2) gene encodes a negative regulator of the tumor protein p53. A single nucleotide polymorphism (SNP) in MDM2 promoter, SNP309 T>G, has been reported to alter MDM2 protein expression and accelerate tumor formation in humans. Studies investigating the association between the polymorphism and human hepatocellular carcinoma (HCC) risk reported conflicting results. We performed a meta-analysis to explore the association of this polymorphism and HCC risk. METHODS All eligible studies published were searched for in PubMed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were assessed for the association using fixed- and random-effects models. RESULTS We identified five case-control studies including 738 cases and 1014 controls for the present meta-analysis. In studies with limited data, we detected significant associations for all genetic models in the overall analysis (OR = 2.51, 95% CI = 1.88-3.36 for GG vs. TT, p <0.001, P(het) = 0.666; OR = 1.71, 95% CI = 1.35-2.18 for TG vs. TT, p <0.001, P(het) = 0.925; OR = 1.94, 95% CI = 1.54-2.43 for dominant model TG + GG vs. TT, p <0.001, P(het) = 0.772; OR = 1.74, 95% CI = 1.39-2.20 for recessive model GG vs. TT + TG, p <0.001, P(het) = 0.656). Moreover, in the subgroup analysis based on Hardy-Weinberg equilibrium (HWE) in controls, sample size, and ethnicity, significant associations were observed in most genetic models. CONCLUSIONS This meta-analysis suggests that the MDM2 309 G allele probably acts as an important HCC risk factor. To further confirm our findings, well-designed studies with large sample sizes and representing different ethnicities are required.

Zinc finger transcription factor 191, directly binding to β‐catenin promoter, promotes cell proliferation of hepatocellular carcinoma

Activation of β‐catenin, the central effector of the canonical wingless‐type (Wnt) pathway, has been implicated in hepatocellular carcinoma (HCC). However, the transcription regulation mechanism of the β‐catenin gene in HCC remains unknown. Here we report that human zinc finger protein 191 (ZNF191) is a potential regulator of β‐catenin transcription. ZNF191, a Krüppel‐like protein, specifically interacts with the TCAT motif, which constitutes the HUMTH01 microsatellite in the tyrosine hydroxylase (TH) gene ex vivo. We demonstrate that ZNF191 is significantly overexpressed in human HCC specimens and is associated with growth of human HCC cells. Global profiling of gene expression in ZNF191 knockdown human hepatic L02 cells revealed that the important Wnt signal pathway genes β‐catenin and cyclin D1 messenger RNAs (mRNAs) are significantly down‐regulated. In agreement with transcription level, β‐catenin and cyclin D1 proteins are also down‐regulated in transient and stable ZNF191 knockdown L02 and hepatoma Hep3B cell lines. Moreover, significant correlation between ZNF191 and β‐catenin mRNA expression was detected in human HCCs. Promoter luciferase assay indicated that ZNF191 can increase transcription activity of the full‐length β‐catenin (CTNNB1) promoter, and nucleotide (nt)‐1407/‐907 of the CTNNB1 promoter exhibited the maximum transcriptional activity. Electrophoretic mobility shift assay showed that purified ZNF191 protein can directly bind to the CTNNB1 promoter, and the binding region is located at nt‐1254/‐1224. Finally, we demonstrate that the key binding sequence of ZNF191 in vivo is ATTAATT. Conclusion: ZNF191 can directly bind to the CTNNB1 promoter and activate the expression of β‐catenin and its downstream target genes such as cyclin D1 in hepatoma cell lines. This study uncovers a new molecular mechanism of transcription regulation of the β‐catenin gene in HCC. (HEPATOLOGY 2012;55:1830–1839)

Linking the septin expression with carcinogenesis.

The septin is a conserved GTP binding protein family which is involved in multiple cellular processes. Many evidences have indicated that some septins were abnormally expressed in certain kinds of tumors and the altered expressions were related to the process of carcinogenesis. To better understand the relationship between septins and cancer, we compared the expression of 14 human septin family members in 35 kinds of tumor types with their normal counterparts using the publicly available ONCOMINE microarray database. We found altered expression of most septin members in many kinds of tumors. Significantly, SEPT2, SEPT8, SEPT9, SEPT11 were consistently up-regulated, and SEPT4, SEPT10 were down-regulated in most cancer types investigated. Furthermore, the abnormal expressions were also in accordance with the tumor malignances or prognosis of corresponding cancer patients. These findings have contributed to the view that septins may belong to a kind of cancer critical genes. More septins might act as potential oncogenes or tumor suppressor genes in cancer development.

The phosphorylation of SEPT2 on Ser218 by casein kinase 2 is important to hepatoma carcinoma cell proliferation

SEPT2 plays an important role in cell division through its effect on cytoskeletons. It is a GTP-binding protein and can also form filament with SEPT6 and SEPT7. Knockdown of SEPT2, 6, and 7 causes stress fibers to disintegrate and then cells lose polarity and divide abnormally. Increasing evidence has shown that septins are related to the regulation of cell proliferation. In this study, the expression of SEPT2 was first identified to be up-regulated in human hepatoma carcinoma cells (HCC). In addition, SEPT2 was found to be phosphorylated on Ser218 by casein kinase 2 (CK2), which was also overexpressed in HCC. By overexpressing SEPT2 and its S218A mutant in SMMC7721 and L02 cell lines, we confirmed that the phosphorylation of SEPT2 on Ser218 by CK2 was crucial to the proliferation of HCC. These results suggest that SEPT2 might be a promising target for liver cancer therapy.

Murine double minute 2 promoter SNP309 polymorphism and prostate cancer risk: A meta-analysis

Objective:  The murine double minute 2 gene encodes a negative regulator of the tumor protein p53. A single nucleotide polymorphism in murine double minute 2 promoter, SNP309 T>G, has been reported to alter murine double minute 2 protein expression and to accelerate tumor formation in humans. We carried out a meta‐analysis to explore the association between this polymorphism and prostate cancer risk.

Involvement of SEPT4_i1 in hepatocellular carcinoma: SEPT4_i1 regulates susceptibility to apoptosis in hepatocellular carcinoma cells

SEPT4 belongs to the Septin family with multiple functions in cell division, cytoskeletal organization and other processes. This study aims to investigate the relationship between SEPT4_i1 isoform and human hepatocellular carcinoma (HCC). We showed that over-expression of SEPT4_i1 in HCC cells was able to sensitize cells to serum starvation-induced apoptosis. By contrast, knockdown of SEPT4_i1 expression in HCC cells was able to rescue cells from apoptosis induced by serum deprivation and to promote cell growth. Expressional analysis of SEPT4_i1 in tumor tissues further revealed that SEPT4_i1 was significantly down-regulated in human HCC tissues. Taken together, these data suggests a tumor suppressor role of SEPT4_i1 in HCC through regulating HCC cell apoptosis.

Meta-analysis shows significant association of the TP53 Arg72Pro with ovarian cancer risk

Growing bodies of studies have been conducted on the association of TP53 Arg72Pro polymorphism with susceptibility to ovarian cancer and have yielded conflicting results. Thus, a meta-analysis was performed to summarize the possible association. 18 case–control studies, including 2,193 ovarian cancer cases and 5,175 controls were identified. The quality of the studies was assessed according to a predefined scale. The strength of the associations between TP53 Arg72Pro polymorphism and ovarian cancer was measured by crude odds ratios (ORs) with 95% confidence intervals (CIs). Overall, no significant association was found between TP53 Arg72Pro polymorphism and ovarian cancer risk when all studies pooled into the meta-analysis in all genetic model. In the subgroup analysis by ethnicity, still no association of this polymorphism with ovarian cancer risk was obtained for all comparison models. However, significantly decreased risks of ovarian cancer were found for Arg/Arg versus Arg/Pro+Pro/Pro (OR 0.84, 95% CI 0.74–0.96) when the analysis was restricted to high quality studies. Conversely, when it was restricted to low quality studies, significantly increased risks were observed for Arg/Arg versus Pro/Pro (OR 1.58, 95% CI 1.09–2.28) and Arg/Arg+Arg/Pro versus Pro/Pro: (OR 1.50, 95% CI 1.10–2.06), which might be spurious due to the poor design of these studies. In conclusion, this meta-analysis suggests that the Arg allele is at a moderately reduced risk for ovarian cancer and this polymorphism might protect against ovarian carcinogenesis.