Burri Nagaraju

Synthesis and biological evaluation of 1,2,3-triazole linked aminocombretastatin conjugates as mitochondrial mediated apoptosis inducers

A series of 1,2,3-triazole linked aminocombretastatin conjugates were synthesized and evaluated for cytotoxicity, inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant anticancer activity against some representative human cancer cell lines and two of the conjugates 6d and 7c displayed potent cytotoxicity with IC50 values of 53 nM and 44 nM against A549 human lung cancer respectively, and were comparable to combretastatin A-4 (CA-4). SAR studies revealed that 1-benzyl substituted triazole moiety with an amide linkage at 3-position of B-ring of the combretastatin subunit are more active compared to 2-position. G2/M cell cycle arrest was induced by these conjugates 6d and 7c and the tubulin polymerization assay (IC50 of 1.16 μM and 0.95 μM for 6d and 7c, respectively) as well as immunofluorescence analysis showed that these conjugates effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Colchicine competitive binding assay suggested that these conjugates bind at the colchicine binding site of tubulin as also observed from the docking studies. Further, mitochondrial membrane potential, ROS generation, caspase-3 activation assay, Hoechst staining and DNA fragmentation analysis revealed that these conjugates induce cell death by apoptosis.

Synthesis and biological evaluation of arylcinnamide linked combretastatin-A4 hybrids as tubulin polymerization inhibitors and apoptosis inducing agents

A series of new molecules have been designed based on a hybridization approach by combining the arylcinnamide and combretastatin pharmacophores. These were synthesized and evaluated for their cytotoxic activity, effect on inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant cytotoxic activity against some representative human cancer cell lines and two of the conjugates 6i and 6p displayed potent cytotoxicity with GI50 values of 56nM and 31nM respectively against the human breast cancer cell line (MCF-7). SAR studies revealed that 3,4-substitution on the phenyl ring of the cinnamide moiety is beneficial for enhanced cytotoxicity. Moreover, G2/M cell cycle arrest was induced by these conjugates (6i and 6p) apart from tubulin polymerization inhibition (IC50 of 1.97μM and 1.05μM respectively). Further, mitochondrial membrane potential, Annexin V-FITC and caspase-9 activation assays suggested that these conjugates induce cell death by apoptosis. Docking studies revealed that these conjugates interact and bind at the colchicine binding site of the tubulin.

Development of pyrrolo[2,1-c][1,4]benzodiazepine β-glucoside prodrugs for selective therapy of cancer

Cancer chemotherapy has several limitations such as often insufficient differentiation between malign tissue and benign tissue. The clinical utility of the pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are inadequate because of the lack of selectivity for tumor tissues, high reactivity of the pharmacophoric imine functionality, low water solubility, and stability. To address these limitations two new β-glucoside prodrugs of PBDs have been synthesized and evaluated for their potential use in selective therapy of solid tumors by ADEPT. The preliminary studies reveal the prodrugs are much less toxic compared to the parent moieties. These prodrugs are activated by β-glucosidase to produce the active cytotoxic moiety signifying their utility in ADEPT of cancer. The prodrugs 1a and 1b were evaluated for their cytotoxic activity in three human cancer cell lines, i.e., A375, MCF-7 and HT-29 by employing MTT assay. The results reveal that the prodrugs have shown significant cytotoxic activity in the presence of enzyme. Another important property of these molecules is their enhanced water solubility and stability, which are essential for a molecule to be an effective drug.

Synthesis of imidazo-thiadiazole linked indolinone conjugates and evaluated their microtubule network disrupting and apoptosis inducing ability

A series of imidazo[2,1-b][1,3,4]thiadiazole linked indolinone conjugates were synthesized and investigated for antiproliferative activity in different human cancer cell lines by changing various substitutions at indolinone and phenyl ring systems. Among them conjugates 7, 14 and 15 were exhibited potent antiproliferative activity with GI50 values from 0.13 to 3.8 μΜ and evaluated for cell cycle analysis, tubulin polymerization assay and apoptosis. Treatment with 7, 14 and 15 were resulted in accumulation of cells in G2/M phase, inhibition of tubulin assembly, disruption of microtubule network. Inhibition of tubulin polymerization was further supported by Western blot analysis. In addition, the conjugates (7, 14 and 15) also showed apoptosis in HeLa cell line, detailed biological studies such as Hoechst 33,258 staining, DNA fragmentation and caspase-3 assays suggested that these compounds induce cell death by apoptosis. Docking studies revealed that these compounds (7, 14 and 15) bind with αAsn101, αThr179, αSer178, βCys241, βLys254 and βLys352 in the colchicine-binding site of the tubulin.