Browsing by Author "Ratheeshkumar, T"

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    Estrogen-dependent cell signaling and apoptosis in BRCA1-blocked BG1 ovarian cancer cells in response to plumbagin and other chemotherapeutic agents
    (ANNALS OF ONCOLOGY, 2008) Thasni, KA; Rakesh, S; Rojini, G; Ratheeshkumar, T; Srinivas, G; Priya, S
    Background: Cellular response to chemotherapeutic drugs in the absence of BRCA1 either completely or partially had drawn less attention. The present study evaluated whether there is a differential inhibition of cell growth by selected compounds with respect to BRCA1 status in estrogen receptor (ER)-positive ovarian cancer cells. Materials and methods: The BG1 ovarian cancer cells used in the experiments were antisensely blocked with BRCA1 gene. Growth inhibition and apoptotic induction were analyzed to evaluate the cytotoxic effects. Small interfering RNA (SiRNA) transfection, western blot analysis, RT-PCR analysis and molecular modeling were carried out to analyze the estrogen-dependent action of plumbagin. Results: Although we found that all the compounds studied induce apoptosis, the induction was in the order of plumbagin > doxorubicin > tamoxifen > cisplatin. Plumbagin can bind to the active site of ER-alpha. Plumbagin, however, induced ER-alpha 46 kDa truncated isoform, which was found abundantly preempted in the cytoplasm compared with a 66-kDa full-length isoform. The truncated isoform is known to inhibit classical ER-alpha signaling pathways. SiRNA-transfected cells for ER-alpha exhibited lower cytotoxicity upon plumbagin treatment than the control-transfected cells. Conclusion: Taken together, this study indicates that plumbagin has chemotherapeutic potential in BRCA1-mutated/defective ER-positive cancers.
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    Genistein induces apoptosis in ovarian cancer cells via different molecular pathways depending on Breast Cancer Susceptibility gene-1 (BRCA1) status
    (EUROPEAN JOURNAL OF PHARMACOLOGY, 2008) Thasni, KAA; Rojini, G; Rakesh, SN; Ratheeshkumar, T; Babu, MS; Srinivas, G; Banerji, A; Srinivas, P
    It has been reported that Breast Cancer Susceptibility gene-1 & 2 (BRCA1 & 2 are potential molecular targets for chemoprevention by isoflavone genistein (4' 5, 7-trihydroxy isoflavone), in breast and prostate cancer cells. It is also known that BRCA1 has inhibitory activity on estrogen receptor-a and genistein's action on cells is mainly through modulation of estrogen receptor activity. The action of genistein with respect to BRCA1 status in ovarian cancer cells has not been reported so far. Therefore in this study, we analyzed the action of genistein on BRCA1 antisense blocked (AS4) and unblocked (NEO) BG-1 ovarian cancer cells. We found that genistein induced comparable cytotoxic effect in both AS4 and NEO cells, but through different pathways. We found that genistein induces caspase 8 dependent apoptotic pathway in NEO cells. Genistein inhibits estrogen receptor-alpha and activates BARD1 in BRCA1 blocked cells and induces estrogen receptor-beta and FAS in presence of BRCA1. It can be concluded that even though there is no difference in the extent of cell death or apoptosis, the molecular mechanism of action of genistein in inducing apoptosis is different in BRCA1 blocked and unblocked cells. This could partially explain the beneficial effects of genistein in both wild type and mutated BRCA1 estrogen receptor positive tumors. (C) 2008 Elsevier B.V. All rights reserved.
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    Structure activity relationship of plumbagin in BRCA1 related cancer cells
    (MOLECULAR CARCINOGENESIS, 2013) Thasni, KA; Ratheeshkumar, T; Rojini, G; Sivakumar, KC; Nair, RS; Srinivas, G; Banerji, A; Somasundaram, V; Srinivas, P
    It has been shown earlier that plumbagin, a naturally occurring naphthaquinone has specific anticancer activity in BRCA1 blocked ovarian cancer cells. Plumbagin can induce estrogen dependent cell signaling and apoptosis in BRCA1 blocked ovarian cancer cells. Being a reactive oxygen species (ROS) generator and apoptosis inducing agent, plumbagin has immense potential as a promising anticancer agent. In this study we analyzed whether there would be increased anticancer activity if the positions of the functional groups on plumbagin were altered and further to analyze the detailed molecular mechanism of action of the lead molecule. Methods like MTT assay, apoptosis analysis by flow cytometry, assessment of mitochondrial membrane potential-m, suppression subtractive hybridization, microarray, molecular docking and estrogen receptorDNA binding activity by electrophoresis mobility shift assay (EMSA) were adopted for assessing the anticancer activity. Consequently we found that, plumbagin was the most potent anticancer agent when compared to structurally related compounds. The anti-cancer activities were in the order plumbagin>1,4-naphthaquinone>juglone>lawsone>menadione. Molecular docking studies showed that plumbagin could be well docked in the receptor ligand complex of TRAILDR5 complexes to activate the extrinsic pathway of apoptosis. Since the antiproliferative activity of plumbagin could be reduced by inhibiting ER, we speculated that plumbagin interferes with the binding of ER to ERE and we confirmed this by EMSA. This study clearly indicates that plumbagin can induce multiple pathways of apoptosis and cell cycle arrest in BRCA1 blocked cells compared to unblocked cells. (c) 2012 Wiley Periodicals, Inc.