Doctor of Philosophy, Central University of Gujarat, India, Cancer Biology (2016)
Sanjay Malhotra, Postdoctoral Faculty Sponsor
Triple negative breast cancer is an aggressive, heterogeneous disease with high recurrence and metastasis rates even with modern chemotherapy regimens and thus is in need of new therapeutics. Here, three novel synthetic analogues of chalcones, plant-based molecules that have demonstrated potency against a wide variety of cancers, were investigated as potential therapeutics for triple negative breast cancer. These compounds exhibit IC50 values of 5 muM in triple negative breast cancer cell lines and are more potent against triple negative breast cancer cell lines than against nontumor breast cell lines according to viability experiments. Tandem mass tag-based quantitative proteomics followed by gene set enrichment analysis and validation experiments using flow cytometry, apoptosis, and Western blot assays revealed three different anticancer mechanisms for these compounds. First, the chalcone analogues induce the unfolded protein response followed by apoptosis. Second, increases in the abundances of MHC-I pathway proteins occurs, which would likely result in immune stimulation in an organism. And third, treatment with the chalcone analogues causes disruption of the cell cycle by interfering with microtubule structure and by inducing G1 phase arrest. These data demonstrate the potential of these novel chalcone derivatives as treatments for triple negative breast cancer, though further work evaluating their efficacy in vivo is needed.
View details for PubMedID 30200768
View details for Web of Science ID 000447609102077
Benzyl isothiocyanate (BITC) is a highly promising phytochemical abundant in cruciferous vegetables with preclinical evidence of in vivo efficacy against breast cancer in xenograft and transgenic mouse models. Mammary cancer chemoprevention by BITC is associated with apoptotic cell death but the underlying mechanism is not fully understood. Herein, we demonstrate for the first time that altered mitochondrial dynamics is an early and critical event in BITC-induced apoptosis in breast cancer cells. Exposure of MCF-7 and MDA-MB-231 cells to plasma achievable doses of BITC resulted in rapid collapse of mitochondrial filamentous network. BITC treatment also inhibited polyethyleneglycol-induced mitochondrial fusion. In contrast, a normal human mammary epithelial cell line (MCF-10A) that was derived from fibrocystic breast disease, was resistant to BITC-mediated alterations in mitochondrial dynamics as well as apoptosis. Transient or sustained decrease in levels of proteins engaged in regulation of mitochondrial fission and fusion was clearly evident after BITC treatment in both cancer cell lines. A trend for a decrease in the levels of mitochondrial fission- and fusion-related proteins was also observed in vivo in tumors of BITC-treated mice compared with control. Immortalized mouse embryonic fibroblasts from Drp1 knockout mice were resistant to BITC-induced apoptosis when compared with those from wild-type mice. Upon treatment with BITC, Bak dissociated from mitofusin 2 in both MCF-7 and MDA-MB-231 cells suggesting a crucial role for interaction of Bak and mitofusins in BITC-mediated inhibition of fusion and morphological dynamics. In conclusion, the present study provides novel insights into the molecular complexity of BITC-induced cell death.
View details for DOI 10.1016/j.mito.2016.06.006
View details for PubMedID 27374852
Sodium butyrate (NaBt) is the byproduct of anaerobic microbial fermentation inside the gastro-intestinal tract that could reach up to 20mM, and has been shown to inhibit the growth of various cancers. Herein, we evaluated its effect on mitochondrial fusion and associated induction of apoptosis in colorectal cancer cells (CRC). NaBt treatment at physiological (1-5mM) concentrations for 12 and 24h decreased the cell viability and induced G2-M phase cell cycle arrest in HCT116 (12h) and SW480 human CRC cells. This cell cycle arrest was associated with mitochondria-mediated apoptosis accompanied by a decrease in survivin and Bcl-2 expression, and generation of reactive oxygen species (ROS). Furthermore, NaBt treatment resulted in a significant decrease in the mitochondrial mass which is an indicator of mitochondrial fusion. Level of dynamin-related protein 1 (DRP1), a key regulator of mitochondrial fission and fusion where its up-regulation correlates with fission, was found to be decreased in CRC cells. Further, at early treatment time, DRP1 down-regulation was noticed in mitochondria which later became drastically reduced in both mitochondria as well as cytosol. DRP1 is activated by cyclin B1-CDK1 complex by its ser616 phosphorylation in which both cyclin B1-CDK1 complex and phospho-DRP1 (ser616) were strongly reduced by NaBt treatment. DRP1 was observed to be regulated by apoptosis as pan-caspase inhibitor showing rescue from NaBt-induced apoptosis also caused the reversal of DRP1 to the normal level as in control proliferating cells. Together, these findings suggest that NaBt can modulate mitochondrial fission and fusion by regulating the level of DRP1 and induce cell cycle arrest and apoptosis in human CRC cells.
View details for DOI 10.1016/j.mito.2013.10.004
View details for Web of Science ID 000336472000008
View details for PubMedID 24177748
Angiogenesis is an effective target in cancer control. The antiangiogenic efficacy and associated mechanisms of acacetin, a plant flavone, are poorly known. In the present study, acacetin inhibited growth and survival (up to 92%; P < 0.001), and capillary-like tube formation on Matrigel (up to 98%; P < 0.001) by human umbilical vein endothelial cells (HUVEC) in regular condition, as well as VEGF-induced and tumor cells conditioned medium-stimulated growth conditions. It caused retraction and disintegration of preformed capillary networks (up to 91%; P < 0.001). HUVEC migration and invasion were suppressed by 68% to 100% (P < 0.001). Acacetin inhibited Stat-1 (Tyr701) and Stat-3 (Tyr705) phosphorylation, and downregulated proangiogenic factors including VEGF, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2), and basic fibroblast growth factor (bFGF) in HUVEC. It also suppressed nuclear localization of pStat-3 (Tyr705). Acacetin strongly inhibited capillary sprouting and networking from rat aortic rings and fertilized chicken egg chorioallantoic membrane (CAM; ?71%; P < 0.001). Furthermore, it suppressed angiogenesis in Matrigel plugs implanted in Swiss albino mice. Acacetin also inhibited tyrosine phosphorylation of Stat-1 and -3, and expression of VEGF in cancer cells. Overall, acacetin inhibits Stat signaling and suppresses angiogenesis in vitro, ex vivo, and in vivo, and therefore, it could be a potential agent to inhibit tumor angiogenesis and growth.
View details for DOI 10.1158/1940-6207.CAPR-13-0209
View details for Web of Science ID 000325272400015
View details for PubMedID 23943785
View details for PubMedCentralID PMC3808880