Combination of AT-101/cisplatin overcomes chemoresistance by inducing apoptosis and modulating epigenetics in human ovarian cancer cells

We investigated the effects of AT-101/cisplatin combination treatment on the expression levels of apoptotic proteins and epigenetic events such as DNA methyltransferase (DNMT) and histone deacetylase (HDAC) enzyme activities in OVCAR-3 and MDAH-2774 ovarian cancer cells. XTT cell viability assay was used to evaluate cytotoxicity. For showing apoptosis, both DNA Fragmentation and caspase 3/7 activity measurements were performed. The expression levels of apoptotic proteins were assessed by human apoptosis antibody array. DNMT and HDAC activities were evaluated by ELISA assay and mRNA levels of DNMT1 and HDAC1 genes were quantified by qRT-PCR. Combination of AT-101/cisplatin resulted in strong synergistic cytotoxicity and apoptosis in human ovarian cancer cells. Combination treatment reduced some pivotal anti-apoptotic proteins such as Bcl-2, HIF-1A, cIAP-1, XIAP in OVCAR-3 cells, whereas p21, Bcl-2, cIAP-1, HSP27, Clusterin and XIAP in MDAH-2774 cells. Among the pro-apoptotic proteins, Bad, Bax, Fas, phospho-p53 (S46), Cleaved caspase-3, SMAC/Diablo, TNFR1 and Cytochrome c were induced in OVCAR-3 cells, whereas, Bax, TRAILR2, FADD, p27, phospho-p53 (S46), Cleaved caspase-3, Cytochrome c, SMAC/Diablo and TNFR1 were induced in MDAH-2774 cells. Combination treatment also inhibited both DNMT and HDAC activities and also mRNA levels in both ovarian cancer cells. AT-101 exhibits great potential in sensitization of human ovarian cancer cells to cisplatin treatment in vitro, suggesting that the combination of AT-101 with cisplatin may hold great promise for development as a novel chemotherapeutic approach to overcome platinum-resistance in human ovarian cancer.     

Effects of lactulose and lactitol on coliform bacteria and bacterial translocation in the caecum during 72-h starvation in rats

Lactulose and lactitol, non-absorbable disaccharides, prevent bacterial translocation (BT) arising from the gut. In contrast, lack of food into the gut leads to coliform bacterial overgrowth and even if it does not cause BT, can induce the risk from other stimuli for BT. In this study, we tested whether lactulose and lactitol affected populations of coliform bacteria in the caecum during starvation in Sprague-Dawley rats. Three groups of rats were starved for 72 h and given oral 2 ml undiluted lactulose (670 mg/ml), 2 ml undiluted lactitol (666 mg/ml) or 2 ml physiological saline, respectively, once a day. The caecum and mesenteric lymph nodes (MLNs) were removed for microbiological and histopathological analyses. The highest degree of coliform bacterial overgrowth, BT to MLNs and histopathological damage were observed in lactulose-treated rats, followed by the group treated with lactitol. As a result of this study, both drugs, especially lactulose augmented the proliferation and translocation tendency of coliform bacteria in the caecum during 72-h starvation in rats.     

Diminished transmission of drug resistant HIV-1 variants with reduced replication capacity in a human transmission model

Background

Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.

Results

In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5⁺ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5⁺ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.

Conclusions

Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.

     

Characterization of the mrgRS locus of the opportunistic pathogen Burkholderia pseudomallei: temperature regulates the expression of a two-component signal transduction system

Background  

Burkholderia pseudomallei is a saprophyte in tropical environments and an opportunistic human pathogen. This versatility requires a sensing mechanism that allows the bacterium to respond rapidly to altered environmental conditions. We characterized a two-component signal transduction locus from B. pseudomallei 204, mrgR and mrgS, encoding products with extensive homology with response regulators and histidine protein kinases of Escherichia coli, Bordetella pertussis, and Vibrio cholerae.