Viral infections are responsible for many illnesses, and recent outbreaks have raised public health concerns. Despite the availability of many antiviral drugs, they are often unsuccessful due to the generation of viral mutants and less effective against their target virus. Identifying novel antiviral drugs is therefore of critical importance and natural products are an excellent source for such discoveries. Coumarin is one such natural compound that is a potential drug candidate owing to its properties of stability, solubility, and low toxicity. There are numerous evidences showing its inhibitory role against infection of various viruses such as HIV, Influenza, Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16). The mechanisms involve either inhibition of proteins essential for viral entry, replication and infection or regulation of cellular pathways such as Akt-Mtor (mammalian target of rapamycin), NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), and anti-oxidative pathway including NrF-2 (The nuclear factor erythroid 2 (NFE2)-related factor 2). This review summarizes the present state of understanding with a focus on coumarin's antiviral effect and their possible molecular mechanisms against Influenza virus, HIV, Hepatitis virus, Dengue virus and Chikungunya virus.

BackgroundInsulin is tightly associated with cancer progression; however, mechanistic insights into such observations are poorly understood. Recent studies show that metabolic transformation is critical to cancer cell proliferation. Here, we attempt to understand the role of insulin in promotion of cancer metabolism. To this end, the role of insulin in regulating glycolytic enzyme pyruvate kinase M2 (PKM2) was examined.ResultsWe observed that insulin up-regulated PKM2 expression, through PI3K/mTOR mediated HIF1α induction, but significantly reduced PKM2 activity independent of this pathway. Drop in PKM2 activity was attributed to subunit dissociation leading to formation of low activity PKM2 oligomers, as assessed by density gradient centrifugation. However, tyrosine 105 phosphorylation of PKM2, known for inhibiting PKM2 activity, remained unaffected on insulin treatment. Interestingly, insulin-induced ROS was found responsible for PKM2 activity reduction. The observed changes in PKM2 status led to augmented cancer metabolism. Insulin-induced PKM2 up-regulation resulted in enhanced aerobic glycolysis as confirmed by PKM2 knockdown studies. Further, PKM2 activity reduction led to characteristic pooling of glycolytic intermediates and increased accumulation of NADPH; suggesting diversion of glucose flux towards macromolecular synthesis, necessary for cancer cell growth.ConclusionThe study identifies new PKM2-mediated effects of insulin on cancer metabolism, thus, advancing the understanding of insulin’s role in cancer.

IntroductionNew levels of gene regulation with microRNA (miR) and gene copy number alterations (CNAs) have been identified as playing a role in various cancers. We have previously reported that sporadic breast cancer tissues exhibit significant alteration in H2AX gene copy number. However, how CNA affects gene expression and what is the role of miR, miR-24-2, known to regulate H2AX expression, in the background of the change in copy number, are not known. Further, many miRs, including miR-24-2, are implicated as playing a role in cell proliferation and apoptosis, but their specific target genes and the pathways contributing to them remain unexplored.MethodsChanges in gene copy number and mRNA/miR expression were estimated using real-time polymerase chain reaction assays in two mammalian cell lines, MCF-7 and HeLa, and in a set of sporadic breast cancer tissues. In silico analysis was performed to find the putative target for miR-24-2. MCF-7 cells were transfected with precursor miR-24-2 oligonucleotides, and the gene expression levels of BRCA1, BRCA2, ATM, MDM2, TP53, CHEK2, CYT-C, BCL-2, H2AFX and P21 were examined using TaqMan gene expression assays. Apoptosis was measured by flow cytometric detection using annexin V dye. A luciferase assay was performed to confirm BCL-2 as a valid cellular target of miR-24-2.ResultsIt was observed that H2AX gene expression was negatively correlated with miR-24-2 expression and not in accordance with the gene copy number status, both in cell lines and in sporadic breast tumor tissues. Further, the cells overexpressing miR-24-2 were observed to be hypersensitive to DNA damaging drugs, undergoing apoptotic cell death, suggesting the potentiating effect of mir-24-2-mediated apoptotic induction in human cancer cell lines treated with anticancer drugs. BCL-2 was identified as a novel cellular target of miR-24-2.Conclusionsmir-24-2 is capable of inducing apoptosis by modulating different apoptotic pathways and targeting BCL-2, an antiapoptotic gene. The study suggests that miR-24-2 is more effective in controlling H2AX gene expression, regardless of the change in gene copy number. Further, the study indicates that combination therapy with miR-24-2 along with an anticancer drug such as cisplatin could provide a new avenue in cancer therapy for patients with tumors otherwise resistant to drugs.

Gemcitabine, an effective agent in treatment of cancer of pancreas, has undergone failures in many instances after multiple cycles of therapy due to emergence of drug resistance. Combination of dietary compounds with clinically validated drugs has emerged as an effective therapeutic approach to treat pancreatic tumors, refractory to gemcitabine therapy. In order to optimize a possible synergistic combination of Gemcitabine (GCB) with dietary molecules, Betuilnic acid (BA) and Thymoquinone (TQ), stand-alone IC50 dose of GCB, BA and TQ was calculated for pancreatic cancer cell lines. Fixed IC50 dose ratio of the dietary molecules in combination with reduced IC50 dose of GCB was tested on GCB resistant PANC-1 and sensitive MIA PaCa-2 cells for synergism, additive response and antagonism, using calcusyn. Combination index (CI) revealed that pre-treatment of BA and TQ along with GCB synergistically inhibited the cancer cell proliferation in in-vitro experiments. Pyruvate kinase (PK) M2 isoform, a promising target involved in cancer cell metabolism, showed down-regulation in presence of TQ or BA in combination with GCB. GCB with BA acted preferentially on tumor mitochondria and triggered mitochondrial permeability transition. Pre-exposure of the cell lines, MIA PaCa-2 and PANC-1, to TQ in combination with GCB induced apoptosis. Thus, the effectiveness of BA or TQ in combination with GCB to inhibit cell proliferation, induce apoptosis and down-regulate the expression of PKM2, reflects promise in pancreatic cancer treatment.