分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-15
摘要: GADD45A is a TP53-regulated and DNA damage-inducible tumor suppressor protein, which regulates cell cycle arrest, apoptosis, and DNA repair, and inhibits tumor growth and angiogenesis. However, the function of GADD45A in autophagy remains unknown. In this report, we demonstrate that GADD45A plays an important role in regulating the process of autophagy. GADD45A is able to decrease LC3-II expression and numbers of autophagosomes in mouse tissues and different cancer cell lines. Using bafilomycin A(1) treatment, we have observed that GADD45A regulates autophagosome initiation. Likely, GADD45A inhibition of autophagy is through its influence on the interaction between BECN1 and PIK3C3. Immunoprecipitation and GST affinity isolation assays exhibit that GADD45A directly interacts with BECN1, and in turn dissociates the BECN1-PIK3C3 complex. Furthermore, we have mapped the 71 to 81 amino acids of the GADD45A protein that are necessary for the GADD45A interaction with BECN1. Knockdown of BECN1 can abolish autophagy alterations induced by GADD45A. Taken together, these findings provide the novel evidence that GADD45A inhibits autophagy via impairing the BECN1-PIK3C3 complex formation.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Human gamma herpesviruses, including Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are capable of inducing tumors, particularly in in immune-compromised individuals. Due to the stringent host tropism, rodents are resistant to infection by human gamma herpesviruses, creating a significant barrier for the in vivo study of viral genes that contribute to tumorigenesis. The closely-related murine gamma herpesvirus 68 (gamma HV68) efficiently infects laboratory mouse strains and establishes robust persistent infection without causing apparent disease. Here, we report that a recombinant gamma HV68 carrying the KSHV G protein-coupled receptor (kGPCR) in place of its murine counterpart induces angiogenic tumors in infected mice. Although viral GPCRs are conserved in all gamma herpesviruses, kGPCR potently activated downstream signaling and induced tumor formation in nude mouse, whereas gamma HV68 GPCR failed to do so. Recombinant gamma HV68 carrying kGPCR demonstrated more robust lytic replication ex vivo than wild-type gamma HV68, although both viruses underwent similar acute and latent infection in vivo. Infection of immunosuppressed mice with gamma HV68 carrying kGPCR, but not wild-type gamma HV68, induced tumors in mice that exhibited angiogenic and inflammatory features shared with human Kaposi's sarcoma. Immunohistochemistry staining identified abundant latently-infected cells and a small number of cells supporting lytic replication in tumor tissue. Thus, mouse infection with a recombinant gamma HV68 carrying kGPCR provides a useful small animal model for tumorigenesis induced by a human gamma herpesvirus gene in the setting of a natural course of infection.
分类: 生物学 >> 生物物理学 >> 肿瘤学 提交时间: 2016-05-11
摘要: Esophageal Squamous Cell Carcinoma (ESCC) is among the most common malignant cancers worldwide. In the past, extensive efforts have been made to characterize the involvement of protein-coding genes in ESCC tumorigenesis but few for long noncoding RNAs (lncRNAs). To investigate the transcriptome profile and functional relevance of lncRNAs, we performed an integrative analysis of a customized combined lncRNA-mRNA microarray and RNA-seq data on ESCCs and matched normal tissues. We identified numerous lncRNAs that were differentially expressed between the normal and tumor tissues, termed "ESCC-associated lncRNAs (ESCALs)", of which, the majority displayed restricted expression pattern. Also, a subset of ESCALs appeared to be associated with ESCC patient survival. Gene set enrichment analysis (GSEA) further suggested that over half of the ESCALs were positively- or nelgativelyassociated with metastasis. Among these, we identified a novel nuclear-retained lncRNA, named Epist, which is generally highly expressed in esophagus, and which is down-regulated during ESCC progression. Epist over-expression and knockdown studies further suggest that Epist inhibits the metastasis, acting as a tumor suppressor in ESCC. Collectively, our analysis of the ESCC transcriptome identified the potential tumor suppressing lncRNA Epist, and provided a foundation for future efforts to identify functional lncRNAs for cancerous therapeutic targeting.
分类: 生物学 >> 生物物理学 >> 基因表达调控与表观遗传学 提交时间: 2016-05-11
摘要: Aim: To examine epigenetic changes and the function of HOXA11 in human gastric cancer (GC). Materials & methods: Seven GC cell lines, five cases of normal gastric mucosa and 112 cases primary GC samples were used in this study. Results: Expression of HOXA11 and lack of promoter region methylation were found in NCI-N87, MKN45, BGC823 and HGC27 cells. Loss of expression and complete methylation were found in AGS gastric cancer cells. Reduced expression and partial methylation were found in MGC803 and SGC7901 cells. Restoration of HOXA11 expression was induced by 5-aza-2'-deoxycytidine. HOXA11 was methylated in 81.25% (91/112) of primary GCs. The presence of methylation was associated with male gender, tumor size, tumor differentiation and lymph node metastasis (all p < 0.05). Restoration of HOXA11 expression reduced cell proliferation, invasion, migration and induced apoptosis and G2/M phase arrest. HOXA11 was found to inhibit Wnt signaling by upregulating NKD1 expression. Conclusion: Epigenetic silencing of HOXA11 promotes GC proliferation, migration and invasion through activation of Wnt signaling.