Sirtuin activation targets IDH-mutant tumors

BackgroundIsocitrate dehydrogenase (IDH)–mutant tumors exhibit an altered metabolic state and are critically dependent upon nicotinamide adenine dinucleotide (NAD+) for cellular survival. NAD+ steady-state levels can be influenced by both biosynthetic and consumptive processes. Here, we investigated activation of sirtuin (SIRT) enzymes, which consume NAD+ as a coenzyme, as a potential mechanism to reduce cellular NAD+ levels in these tumors.MethodsThe effect of inhibition or activation of sirtuin activity, using (i) small molecules, (ii) clustered regularly interspaced short palindromic repeat/CRISPR associated protein 9 gene editing, and (iii) inducible overexpression, was investigated in IDH-mutant tumor lines, including patient-derived IDH-mutant glioma lines.ResultsWe found that Sirt1 activation led to marked augmentation of NAD+ depletion and accentuation of cytotoxicity when combined with inhibition of nicotinamide phosphoribosyltransferase (NAMPT), consistent with the enzymatic activity of SIRT1 as a primary cellular NAD+ consumer in IDH-mutant cells. Activation of Sirt1 through either genetic overexpression or pharmacologic Sirt1-activating compounds (STACs), an existing class of well-tolerated drugs, led to inhibition of IDH1-mutant tumor cell growth.ConclusionsActivation of Sirt1 can selectively target IDH-mutant tumors. These findings indicate that relatively nontoxic STACs, administered either alone or in combination with NAMPT inhibition, could alter the growth trajectory of IDH-mutant gliomas while minimizing toxicity associated with cytotoxic chemotherapeutic regimens.     

Membrane‐initiated estrogen signaling in prostate cancer: A route to epithelial‐to‐mesenchymal transition

The plasma membrane (PM) is considered as a major druggable site. More than 50% of the existing drugs target PM proteins. In the wake of emerging data indicating a key role of estrogens in prostate cancer (PCa) pathogenesis, the study was undertaken to explore whether the estrogen binding sites exist on the PM and if such sites are functionally relevant in PCa. Estradiol (E2) binding to the PM was detected in androgen‐dependent (LNCaP), androgen‐independent (PC3, DU145) PCa cell lines, nontumorigenic (RWPE1) prostate epithelial cell line, and rat prostate cells. Conventional estrogen receptors (nuclear estrogen receptors), known for their nuclear localization, were detected in the PM enriched extracts. This was indirectly confirmed by reduced localization of ERs on the PM of cells, silenced for the expression of their cognate genes. Further, unlike cell‐permeable E2, stimulation with cell‐impermeable estradiol (E2‐BSA) did not induce proliferation in LNCaP cells. However, stimulation with E2‐BSA led to alterations in the phosphorylation status of several kinases including GSK3 and AKT, along with the hyperphosphorylation of cytoskeletal proteins such as β‐actin and cytokeratin 8 in LNCaP. This was accompanied by epithelial‐to‐mesenchymal (EMT) features such as increased migration and invasion; higher vimentin expression, and a concomitant decrease in the E‐cadherin expression. These effects were not observed in RWPE1 cells. Interestingly, cell‐permeable E2 failed to induce EMT in PCa cells. This in vitro study is the first to suggest that the PM‐initiated estrogen signaling contributes to higher invasiveness in PCa cells. Plasma membrane ERs may act as novel targets for PCa therapeutics.     

Inhibition of matrix degrading enzymes and invasion in human glioblastoma (U87MG) Cells by isoflavones

Summary Glioblastoma multiforme is a primary brain tumor associated with extensive invasion into surrounding brain tissue. Matrix metalloproteinases (MMPs) and urokinase plasminogen activation (uPA) system are shown to be involved in tumor invasion as they help in degradation of extracellular matrix (ECM) proteins and thus assist in the movement of cells. MMP-2 and 9 were shown to be upregulated in gliomas, suggesting their involvement in invasion. Genistein and biochanin A are isoflavones commonly known as phytoestrogens and have some anticancer properties. We hypothesize that these two isoflavones can induce a lowering of tumor invasion by decreasing the activity of matrix degrading enzymes. In this study we investigated the effects of genistein and biochanin A on invasive activity of U87MG cells using the Calbiochem in vitro invasion assay system. Our results suggest that genistein and biochanin A induced a decrease in invasive activity of U87MG cells in a dose-related manner. Genistein also induced a decrease in EGF-stimulated invasion thereby implicating an involvement of EGF-mediated signaling in invasion. Our results also show that treatment of U87MG cells with the two isoflavones induced decreases in the enzymatic activity of MMP-9 and the protein levels of MT1-MMP and uPAR.     

Modeling the Impact of Trichomonas vaginalis Infection on HIV Transmission in HIV-Infected Individuals in Medical Care

BACKGROUND:: To assess factors associated with having a Trichomonas vaginalis (TV) infection among persons receiving care for human immunodeficiency virus (HIV) and estimate the number of transmitted HIV infections attributable to TV. METHODS:: HIV clinic patients were recruited from 2 secondary prevention studies, screened by urine nucleic-acid amplification tests for sexually transmitted infections, and interviewed about risk factors (baseline, 6, and 12 months). We conducted mathematical modeling of the results to estimate the number of transmitted HIV infections attributable to TV among a cohort of HIV-infected patients receiving medical care in North Carolina. RESULTS:: TV was prevalent in 7.4%, and incident in 2% to 3% of subjects at follow-up. Individuals with HIV RNA <400 copies/mL (odds ratio, 0.32; 95% CI: 0.14-0.73) and at least 13 years of education (odds ratio, 0.24; 95% CI: 0.08-0.70) were less likely to have TV. Mathematical modeling predicted that 0.062 HIV transmission events occur per 100 HIV-infected women in the absence of TV infection and 0.076 HIV infections per 100 HIV- and TV-infected women (estimate range: 0.070-0.079), indicating that 23% of the HIV transmission events from HIV-infected women may be attributable to TV infection when 22% of women are coinfected with TV. CONCLUSIONS:: The data suggest the need for improved diagnosis of TV infection and suggest that HIV-infected women in medical care may be appropriate targets for enhanced testing and treatment.