Relationship Between EBV Infection and Expression of Cellular Proteins c-Myc, Bcl-2, and Bax in Gastric Carcinomas:

Metabolic Control by DNA Tumor Virus-Encoded Proteins

Viruses co-opt a multitude of host cell metabolic processes in order to meet the energy and substrate requirements for successful viral replication. However, due to their limited coding capacity, viruses must enact most, if not all, of these metabolic changes by influencing the function of available host cell regulatory proteins. Typically, certain viral proteins, some of which can function as viral oncoproteins, interact with these cellular regulatory proteins directly in order to effect changes in downstream metabolic pathways. This review highlights recent research into how four different DNA tumor viruses, namely human adenovirus, human papillomavirus, Epstein-Barr virus and Kaposi's associated-sarcoma herpesvirus, can influence host cell metabolism through their interactions with either MYC, p53 or the pRb/E2F complex. Interestingly, some of these host cell regulators can be activated or inhibited by the same virus, depending on which viral oncoprotein is interacting with the regulatory protein. This review highlights how MYC, p53 and pRb/E2F regulate host cell metabolism, followed by an outline of how each of these DNA tumor viruses control their activities. Understanding how DNA tumor viruses regulate metabolism through viral oncoproteins could assist in the discovery or repurposing of metabolic inhibitors for antiviral therapy or treatment of virus-dependent cancers.

Mitochondrial Heat Shock Response Induced by Ectromelia Virus is Accompanied by Reduced Apoptotic Potential in Murine L929 Fibroblasts

Poxviruses utilize multiple strategies to prevent activation of extrinsic and intrinsic apoptotic pathways for successful replication. Mitochondrial heat shock proteins (mtHsps), especially Hsp60 and its cofactor Hsp10, are engaged in apoptosis regulation; however, until now, the influence of poxviruses on mtHsps has never been studied. We used highly infectious Moscow strain of ectromelia virus (ECTV) to investigate the mitochondrial heat shock response and apoptotic potential in permissive L929 fibroblasts. Our results show that ECTV-infected cells exhibit mostly mitochondrial localization of Hsp60 and Hsp10, and show overexpression of both proteins during later stages of infection. ECTV infection has only moderate effect on the electron transport chain subunit expression. Moreover, increase of mtHsp amounts is accompanied by lack of apoptosis, and confirmed by reduced level of pro-apoptotic Bax protein and elevated levels of anti-apoptotic Bcl-2 and Bcl-xL proteins. Taken together, we show a positive relationship between increased levels of Hsp60 and Hsp10 and decreased apoptotic potential of L929 fibroblasts, and further hypothesize that Hsp60 and/or its cofactor play important roles in maintaining protein homeostasis in mitochondria for promotion of cell survival allowing efficient replication of ECTV.

Role of CTLA4 in the proliferation and survival of chronic lymphocytic leukemia

Earlier, we reported that CTLA4 expression is inversely correlated with CD38 expression in chronic lymphocytic leukemia (CLL) cells. However, the specific role of CTLA4 in CLL pathogenesis remains unknown. Therefore, to elucidate the possible role of CTLA4 in CLL pathogenesis, CTLA4 was down-regulated in primary CLL cells. We then evaluated proliferation/survival in these cells using MTT, (3)H-thymidine uptake and Annexin-V apoptosis assays. We also measured expression levels of downstream molecules involved in B-cell proliferation/survival signaling including STAT1, NFATC2, c-Fos, c-Myc, and Bcl-2 using microarray, PCR, western blotting analyses, and a stromal cell culture system. CLL cells with CTLA4 down-regulation demonstrated a significant increase in proliferation and survival along with an increased expression of STAT1, STAT1 phosphorylation, NFATC2, c-Fos phosphorylation, c-Myc, Ki-67 and Bcl-2 molecules. In addition, compared to controls, the CTLA4-downregulated CLL cells showed a decreased frequency of apoptosis, which also correlated with increased expression of Bcl-2. Interestingly, CLL cells from lymph node and CLL cells co-cultured on stroma expressed lower levels of CTLA4 and higher levels of c-Fos, c-Myc, and Bcl-2 compared to CLL control cells. These results indicate that microenvironment-controlled-CTLA4 expression mediates proliferation/survival of CLL cells by regulating the expression/activation of STAT1, NFATC2, c-Fos, c-Myc, and/or Bcl-2.

Impact of MTHFR gene C677T polymorphism on Bcl-2 gene methylation and protein expression in colorectal cancer

OBJECTIVE

To investigate the impact of MTHFR C677T polymorphism on Bcl-2 gene promoter CpG island (CGI) methylation and Bcl-2 protein expression.

MATERIAL AND METHODS

MTHFR polymorphisms of 86 sporadic colorectal cancer (CRC) patients and 100 healthy volunteers were analyzed by PCR-based restriction fragment length polymorphism, and Bcl-2 promoter CGI methylation in 86 CRC tissues and 86 paired nonneoplastic adjacent tissues was determined by methylation-specific PCR. Bcl-2 oncoprotein expression in 70 CRC tissues and paired nonneoplastic adjacent tissues was detected by immunohistochemistry.

RESULTS

The frequency of MTHFR 677 T allele and combined variant genotypes (677CT + TT) in CRC patients was significantly higher than that in healthy controls (p = 0.023 and p = 0.035, respectively), and there is a significant association between 677TT or 677(CT + TT) genotypes and CRC (OR = 2.534, p = 0.045 and OR = 1.888, p = 0.035, respectively). The frequency of methylated Bcl-2 promoter CGI in tumor tissues was significantly lower than that in nonneoplastic adjacent tissues (p = 0.014). The frequency of methylated Bcl-2 promoter CGI in CRC tissues of the individuals with CC genotype was significantly higher than that of those with CT/TT genotypes (p = 0.018), there was significant distribution difference of C and T alleles between individuals with methylated and unmethylated Bcl-2 promoter CGI in colorectal cancer tissues (p = 0.023). Bcl-2 promoter hypomethylation was significantly correlated with Bcl-2 oncoprotein expression in colorectal cancer tissues (r = 0.558, p < 0.001).

CONCLUSION

Bcl-2 promoter is hypomethylated in colorectal cancer tissue, and there is a significant correlation between MTHFR 677 TT or CT/TT genotypes and CRC or Bcl-2 promoter CGI methylation/oncoprotein expression in CRC.

The pathogenic role of Epstein-Barr virus (EBV) in sclerosing polycystic adenosis

Sclerosing polycystic adenosis (SPA) is a pathology of the salivary gland which occurs infrequently and has a controversial etiology. In this study, we investigated the possible roles of HPV and EBV in the pathogenesis of SPA. Archived cases of salivary gland lesions were retrieved, and their diagnoses were re-evaluated; cases that fit the diagnosis of SPA were selected and subjected to Alcian Blue-Periodic Acid Schiff's histochemical staining and immunohistochemical staining for HPV-1, EBV, S-100, and Bcl-2 proteins in addition to the proliferative marker Ki-67. In addition, RNA extracted from formalin-fixed, paraffin-embedded tissues was subjected to RT-PCR to confirm any positive immunohistochemical results. Co-localization of EBV and Bcl-2 in lesional cells was the most striking finding; Ki-67 was expressed in basal cells, while no expression was seen in the adjacent salivary gland cells. Our EBV (+) ve immunostaining results were confirmed by RT-PCR using RNA extracted from paraffin sections. Our results suggest a significant pathogenic role of EBV in SPA. Moreover, they provide new evidence on the neoplastic nature of SPA.