Beschreibung: MicroRNAs (miRNAs) engage in complex interactions with the machinery that controls the transcriptome and concurrently target multiple mRNAs. Here we demonstrate that microRNA-495-3p (miR-495-3p) functions as a potent tumour suppressor by governing ten oncogenic epigenetic modifiers (EMs) in gastric carcinogenesis. From the large cohort transcriptome datasets of gastric cancer (GC) patients available from The Cancer Genome Atlas (TCGA) and the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO), we were able to recapitulate fifteen EMs as significantly overexpressed in GC among the 51 EMs that were previously reported to be involved in cancer progression. Computational target prediction yielded miR-495-3p, that targets as many as ten of the fifteen candidate oncogenic EMs. Ectopic expression of miRNA mimics in GC cells caused miR-495-3p to suppress ten EMs, and inhibited tumour cell growth and proliferation via caspase-dependent and caspase-independent cell death processing. In addition, in vitro metastasis assays showed that miR-495-3p plays a role in the metastatic behavior of GC cells by regulating SLUG, vimentin and N-cadherin. Furthermore, treatment of GC cells with 5-aza-2'-deoxcytidine restored miR-495-3p expression; sequence analysis revealed hypermethylation of the miR-495-3p promoter region in GC cells. A negative regulatory loop is proposed, whereby DNMT1, among ten oncogenic EMs, regulates miR-495-3p expression via hypermethylation of the miR-495-3p promoter. Our findings suggest that the functional loss or suppression of miR-495-3p triggers overexpression of multiple oncogenic EMs, and thereby contributes to malignant transformation and growth of gastric epithelial cells.

Beschreibung: An accurate tool enabling early diagnosis of hepatocellular carcinoma (HCC) is clinically important, since early detection of HCC markedly improves survival. We aimed to investigate the molecular markers underlying early progression of HCC that can be detected in precancerous lesions. We designed a gene selection strategy to identify potential driver genes by integrative analysis of transcriptome and clinicopathologic data of human multi-stage HCC tissues including precancerous lesions, low- and high-grade dysplastic nodules. The gene selection process was guided by detecting the selected molecules in both HCC and precancerous lesion. Using various computational approaches, we selected 10 gene elements as a candidate and, through immunohistochemical staining, showed that BANF1, PLOD3 and SF3B4 are HCC decision markers with superior capability to diagnose early-stage HCC in a large cohort of HCC patients, as compared to the currently popular trio of HCC diagnostic markers: glypican 3, glutamine synthetase, and heat-shock protein 70. Targeted inactivation of BANF1 , PLOD3 and SF3B4 inhibits in vitro and in vivo liver tumorigenesis by selectively modulating EMT and cell cycle proteins. Treatment of nanoparticles containing siRNAs of the three genes suppressed liver tumor incidence as well as tumor growth rates in spontaneous mouse HCC model. We also demonstrated that SF3B4 overexpression triggers SF3b complex to splice tumor suppressor KLF4 transcript to non-functional skipped exon transcripts. This contributes to malignant transformation and growth of hepatocyte via transcriptional inactivation of p27 Kip1 and simultaneously activation of Slug genes. Conclusion : The findings suggest novel molecular markers of BANF1, PLOD3 and SF3B4 indicating early-stage HCC in precancerous lesion, and also suggest drivers for understanding the development of hepatocarcinogenesis. This article is protected by copyright. All rights reserved.

Beschreibung: Ubiquitin-binding histone deacetylase 6 (HDAC6) is uniquely endowed with tubulin deacetylase activity and plays an important role in the clearance of misfolded protein by autophagy. In cancer, HDAC6 has become a target for drug development due to its major contribution to oncogenic cell transformation. In the present study, we showed that HDAC6 expression was down-regulated in a large cohort of human hepatocellular carcinoma (HCC) patients, and that low expression of HDAC6 was significantly associated with poor prognosis of HCC patients in 5-year overall, disease-free and recurrence-free survivals. Notably, we observed that ectopic overexpression of HDAC6 suppressed tumor cell growth and proliferation in various liver cancer cells, and elicited increased LC3B-II conversion and autophagic vacuole formation without causing apoptotic cell death or cell cycle inhibition. In addition, the sustained-overexpression of HDAC6 reduced in vivo tumor growth rate in a mouse xenograft model. It was also found that HDAC6 mediated autophagic cell death via Beclin 1 and activation of the LC3-II pathway in liver cancer cells, and that HDAC6 overexpression activated c-Jun NH2-terminal kinase (JNK) and increased the phosphorylation of c-Jun. In contrast, the induction of Beclin 1 expression was blocked by SP600125 (a specific inhibitor of JNK) or by small-interfering RNA directed against HDAC6. Conclusion: Our findings suggest that loss of HDAC6 expression in human HCCs and tumor suppression by HDAC6 occur via the activation of caspase-independent autophagic cell death through JNK/Beclin 1 pathway in liver cancer, and thus, that a novel tumor suppressor function mechanism involving HDAC6 may be amenable to non-epigenetic regulation. (H EPATOLOGY 2012.)

Beschreibung: Environmental Science & Technology DOI: 10.1021/es302480v

Beschreibung: Sirtuins are NAD + -dependent deacetylases and function in cellular metabolism, stress resistance and ageing. For Sirtuin7 (SIRT7), a role in ribosomal gene transcription is proposed, but its function in cancer has been unclear. In this study, we showed that SIRT7 expression was up-regulated in a large cohort of human hepatocellular carcinoma (HCC) patients. SIRT7 knockdown influenced the cell cycle and caused a significant increase of liver cancer cells to remain in the G1/S phase and to suppress growth. This treatment restored p21 WAF1/Cip1 , induced Beclin-1 and repressed cyclin D1. In addition, sustained suppression of SIRT7 reduced the in vivo tumor growth rate in a mouse xenograft model. To explore mechanisms in SIRT7 regulation, microRNA (miRNA) profiling was carried out. This identified five significantly down-regulated miRNAs in HCC. Bioinformatics analysis of target sites and ectopic expression in HCC cells evidenced miR-125a-5p and miR-125b to suppress SIRT7 and cyclin D1 expression and to induce p21 WAF1/Cip1 -dependent G1 cell cycle arrest. Furthermore, treatment of HCC cells with 5-aza-2′-deoxycytidine or ectopic expression of wild-type but not mutated p53 restored miR-125a-5p and miR-125b expression and inhibited tumor cell growth to suggest their regulation by promoter methylation and p53 activity. To evidence clinical significance of these findings, mutations in the DNA binding domain of p53 and promoter methylation of miR-125b were investigated. Four out of nine patients with induced SIRT7 carried mutations in p53 gene and one patient showed hypermethylation of miR-125b promoter region. Conclusion : Our findings suggest oncogenic potential of SIRT7 in hepatocarcinogenesis. A regulatory loop is proposed whereby SIRT7 inhibits transcriptional activation of p21 WAF1/Cip1 via repression of miR-125a-5p and miR-125b. This makes SIRT7 a promising target in cancer therapy. (H EPATOLOGY 2012.)