Ramesh Ummanni

Statin‐induced inhibition of breast cancer proliferation and invasion involves attenuation of iron transport: intermediacy of nitric oxide and antioxidant defence mechanisms

Accumulating evidence from in vitro, in vivo, clinical and epidemiological studies shows promising results for the use of statins against many cancers including breast carcinoma. However, the molecular mechanisms responsible for the anti‐proliferative and anti‐invasive properties of statins still remain elusive. In this study, we investigated the involvement of nitric oxide, iron homeostasis and antioxidant defence mechanisms in mediating the anti‐proliferative and anti‐invasive properties of hydrophobic statins in MDA‐MB‐231, MDA‐MB‐453 and BT‐549 metastatic triple negative breast cancer cells. Fluvastatin and simvastatin significantly increased cytotoxicity which was reversed with mevalonate. Interestingly, fluvastatin downregulated transferrin receptor (TfR1), with a concomitant depletion of intracellular iron levels in these cells. Statin‐induced effects were mimicked by geranylgeranyl transferase inhibitor (GGTI‐298) but not farnesyl transferase inhibitor (FTI‐277). Further, it was observed that TfR1 downregulation is mediated by increased nitric oxide levels via inducible nitric oxide synthase (iNOS) expression. NOS inhibitors (asymmetric dimethylarginine and 1400W) counteracted and sepiapterin, a precursor of tetrahydrobiopterin, exacerbated statin‐induced depletion of intracellular iron levels. Notably, fluvastatin increased manganese superoxide dismutase (by repressing the transcription factor DNA damage‐binding protein 2), catalase and glutathione which, in turn, diminished H2O2 levels. Fluvastatin‐induced downregulation of TfR1, matrix metalloproteinase‐2, ‐9 and inhibition of invasion were reversed in the presence of aminotriazole, a specific inhibitor of catalase. Finally, we conclude that fluvastatin, by altering iron homeostasis, nitric oxide generation and antioxidant defence mechanisms, induces triple negative breast cancer cell death.

Synthesis and evaluation of novel fluorinated pyrazolo-1,2,3-triazole hybrids as antimycobacterial agents

A library of novel 3-trifluoromethyl pyrazolo-1,2,3-triazole hybrids (5-7) were accomplished starting from 5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-amine (1) via key intermediate 2-azido-N-(5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)acetamide (3) through click chemistry approach. Thus obtained compounds in 5-7 series were evaluated for in vitro antimycobacterial activity against Mycobacterium smegmatis (MC(2) 155) and also verified the cytotoxicity. These studies engendered promising lead compounds 5q, 7b and 7c with MIC (μg/mL) values 15.34, 16.18 and 16.60, respectively. Amongst these three compounds, 2-(4-(4-methoxybenzoyl)-1H-1,2,3-triazol-1-yl)-N-(5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl) acetamide (5q) emerged as the most promising antitubercular agent with lowest cytotoxicity against the A549 cancer cell line. This is the first report to demonstrate the pyrazolo triazole hybrids as potential antimycobacterial agents.

Synthesis, in vitro anticancer and antimycobacterial evaluation of new 5-(2,5-dimethoxyphenyl)-1,3,4-thiadiazole-2-amino derivatives

A series of 2,5-disubstituted-1,3,4-thiadiazole derivatives 5a-5l, 7a-7e and 9 have been synthesised and screened for in vitro antimycobacterial activity against Mycobacterium smegmatis MC-155. In addition these compounds have also been screened for cytotoxic activity against cancer cell lines HT-29, MDA-MB-231 by MTT colorimetric assay. The compounds are well characterized by spectral analysis viz. (1)H NMR, (13)C NMR, FT-IR, mass and HRMS. Screening results indicate that compounds 5g, 7a possess good antitubercular activity with MIC value 65.74 and 40.86, respectively, compounds 5g, 7a, 7b, 7d, 7e and 9 displayed promising cytotoxic activity against the cell lines tested. 5g and 7a stand out to be potent antimycobacterial and anticancer agents among the tested series. Further the title compounds were also tested on human normal cells HEK293T and are found to be safer with lesser cytotoxicity. It is interesting to observe that compound 5g has come out to be safer, potent anticancer and antimycobacterial agent.

Imidazole derivatives show anticancer potential by inducing apoptosis and cellular senescence

Imidazole-based compounds are attractive targets in the design of novel chemical structures for the discovery of new drugs. In the current study, we have synthesized a series of new 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by multicomponent reaction (MCR). Vanillin and isovanillin derivatives were reacted with benzil/pyridil and diverse amines and ammonium acetate in acetic acid at 50–110 °C for 24 h to afford respective imidazoles in 55–70% yields. The series of molecules were evaluated for anti-cancer potential against the National Cancer Institutes 60 human cancer cell line panel. Preliminary screening highlighted the anticancer potential of 2,2′-(2-(3-(cyclopentyloxy)-4-methoxyphenyl)-1-isobutyl-1H-imidazole-4,5-diyl)dipyridine (NSC 771432) against different cancer cell types. A549 cells were treated in vitro to determine the mode of action of NSC 771432 on growth of these cells. This compound inhibits anchorage independent growth and cell migration, and induces cell cycle arrest in the G2/M phase. Also, the exposure of A549 cells to NSC 771432 leads to cellular senescence.

Investigation of triazole-linked indole and oxindole glycoconjugates as potential anticancer agents: novel Akt/PKB signaling pathway inhibitors

In continuation of our venture towards the synthesis of novel bioactive agents, two sets of triazole-linked glycoconjugates were synthesized from indole/oxindole (29 compounds) and were further characterized by IR (infrared spectroscopy), 1H NMR (nuclear magnetic resonance), 13C NMR and mass spectral analysis. The newly synthesized target compounds were evaluated for their preliminary in vitro anticancer activity against DU145 (prostate cancer), HeLa (cervical cancer), A549 (lung cancer) and MCF-7 (breast cancer) cell lines. In the sulforhodamine B (SRB) assay, the results indicated that compounds 5f (indole derivative) and E-9b (oxindole derivative) displayed remarkable cytotoxic activity against DU145 cells. Moreover, the colony formation assay (soft agar assay) revealed that compounds 5f and E-9b can inhibit the growth and proliferation of DU145 cells. The impact of the most active cytotoxic compounds 5f and E-9b on the cell cycle distribution was assessed in DU145 cells, which displayed a cell cycle arrest at the sub-G1 phase. Next, compounds 5f and E-9b were tested for caspase activation in DU145 cells, and the results specified that these compounds have the capability to induce apoptosis in cells through an intrinsic pathway leading to subsequent cell death. Further studies also confirmed that compounds 5f and E-9b act against the protein kinase B (Akt/PKB) pathway to inhibit the proliferation of cancer cells. Thus, compounds 5f and E-9b could be novel potential anticancer leads as the normal cell line NIH/3T3 (fibroblast) studies showed no significant cytotoxicity.

Oxazolidinone derivatives: cytoxazone-linezolid hybrids induces apoptosis and senescence in DU145 prostate cancer cells.

In this study, we report the synthesis of novel oxazolidinone derivatives derived from linezolid 3 having p-methoxyphenyl group at C-4 position. In vitro evaluation for their anticancer activity toward cultured A549, DU145, HELA, and MCF7 were carried out. The series of compounds prepared displayed wide range of cytotoxicity in MTT assays (10-70 μM) across the cell lines tested. Of the all tested compounds 16 and 17 displayed good anticancer potential against A549 (lung) and DU145 (prostate) cancer cells. Further, to determine their anticancer potential, in the present study we have assessed effect of 17 on DU145 cells growth in in vitro assays. The results clearly demonstrated that the exposure of DU145 cells to 17 inhibits cell proliferation and induces apoptosis by activation of caspase-3 and -9. Long term exposure of DU145 cells to 17 induced cellular senescence confirmed by senescence marker β-galactosidase staining of cells on post exposure to 17. The results from this current report support that the oxazolidinone derivatives with ethyl and acryl substitutions showed promising anticancer activity which will be helpful to develop further novel anticancer agents with better therapeutic potential.

Design, synthesis and biological activity evaluation of novel pefloxacin derivatives as potential antibacterial agents

A facile and efficient method for the synthesis of novel derivatives of pefloxacin hydrazone via condensation of various aldehydes and pefloxacin acid hydrazide using conventional as well as solvent-free microwave irradiation methods was reported. The biological activity of these compounds was screened using array of techniques and found to exhibit promising broad spectrum of antibacterial activity against Gram-positive and Gram-negative bacteria, moderate antimycobacterial activity against Mycobacterium smegmatis and moderate antifungal activity opposed to Aspergillus clavatus and Candida albicans. Cytotoxic assay of the title compounds was evaluated against human Pc-3 cancer cell lines, and interestingly, very good anticancer properties were shown by the compounds. To explore the binding mode of the compounds and understand the key active site residues with Staphylococcusaureus DNA gyrase, a molecular docking study has been performed. The results of the docking studies of the reported derivatives were quite promising and manifested strong non-bonded interactions with DNA Gyrase.

Fluvastatin Mediated Breast Cancer Cell Death: A Proteomic Approach to Identify Differentially Regulated Proteins in MDA-MB-231 Cells

Statins are increasingly being recognized as anti-cancer agents against various cancers including breast cancer. To understand the molecular pathways targeted by fluvastatin and its differential sensitivity against metastatic breast cancer cells, we analyzed protein alterations in MDA-MB-231 cells treated with fluvastatin using 2-DE in combination with LC-MS/MS. Results revealed dys-regulation of 39 protein spots corresponding to 35 different proteins. To determine the relevance of altered protein profiles with breast cancer cell death, we mapped these proteins to major pathways involved in the regulation of cell-to-cell signaling and interaction, cell cycle, Rho GDI and proteasomal pathways using IPA analysis. Highly interconnected sub networks showed that vimentin and ERK1/2 proteins play a central role in controlling the expression of altered proteins. Fluvastatin treatment caused proteolysis of vimentin, a marker of epithelial to mesenchymal transition. This effect of fluvastatin was reversed in the presence of mevalonate, a downstream product of HMG-CoA and caspase-3 inhibitor. Interestingly, fluvastatin neither caused an appreciable cell death nor did modulate vimentin expression in normal mammary epithelial cells. In conclusion, fluvastatin alters levels of cytoskeletal proteins, primarily targeting vimentin through increased caspase-3- mediated proteolysis, thereby suggesting a role for vimentin in statin-induced breast cancer cell death.

Identification of New Molecular Entities (NMEs) as Potential Leads against Tuberculosis from Open Source Compound Repository

The purpose of this study was to provide a number of diverse and promising early-lead compounds that will feed into the drug discovery pipeline for developing new antitubercular agents. The results from the phenotypic screening of the open-source compound library against Mycobacterium smegmatis and Mycobacterium bovis (BCG) with hit validation against M. tuberculosis (H37Rv) have identified novel potent hit compounds. To determine their druglikeness, a systematic analysis of physicochemical properties of the hit compounds has been performed using cheminformatics tools. The hit molecules were analysed by clustering based on their chemical finger prints and structural similarity determining their chemical diversity. The hit compound library is also filtered for druglikeness based on the physicochemical descriptors following Lipinski filters. The robust filtration of hits followed by secondary screening against BCG, H37Rv and cytotoxicity evaluation has identified 12 compounds with potential against H37Rv (MIC range 0.4 to 12.5 μM). Furthermore in cytotoxicity assays, 12 compounds displayed low cytotoxicity against liver and lung cells providing high therapeutic index > 50. To avoid any variations in activity due to the route of chemical synthesis, the hit compounds were re synthesized independently and confirmed for their potential against H37Rv. Taken together, the hits reported here provides copious potential starting points for generation of new leads eventually adds to drug discovery pipeline against tuberculosis.

Epigenetic suppression of human telomerase (hTERT) is mediated by the metastasis suppressor NME2 in a G-quadruplex dependent fashion

Transcriptional activation of the human telomerase reverse transcriptase (hTERT) gene, which remains repressed in adult somatic cells, is critical during tumorigenesis. Several transcription factors and the epigenetic state of the hTERT promoter are known to be important for tight control of hTERT in normal tissues, but the molecular mechanisms leading to hTERT reactivation in cancer are not well-understood. Surprisingly, here we found occupancy of the metastasis suppressor non-metastatic 2 (NME2) within the hTERT core promoter in HT1080 fibrosarcoma cells and HCT116 colon cancer cells and NME2-mediated transcriptional repression of hTERT in these cells. We also report that loss of NME2 results in up-regulated hTERT expression. Mechanistically, additional results indicated that the RE1-silencing transcription factor (REST)–lysine-specific histone demethylase 1 (LSD1) co-repressor complex associates with the hTERT promoter in an NME2-dependent way and that this assembly is required for maintaining repressive chromatin at the hTERT promoter. Interestingly, a G-quadruplex motif at the hTERT promoter was essential for occupancy of NME2 and the REST repressor complex on the hTERT promoter. In light of this mechanistic insight, we studied the effects of G-quadruplex–binding ligands on hTERT expression and observed that several of these ligands repressed hTERT expression. Together, our results support a mechanism of hTERT epigenetic control involving a G-quadruplex promoter motif, which potentially can be targeted by tailored small molecules.