4ß-amidotriazole linked podophyllotoxin congeners: DNA topoisomerase-IIα inhibition and potential anticancer agents for prostate cancer.

Topoisomerases (topo-I and topo-II) have occupied a significant role in DNA replication, transcription, and are a promising set of antitumor targets. In the present approach, a series of new 4ß-amidotriazole linked podophyllotoxin derivatives (10a-i and 11a-k) were designed, synthesized by employing the click chemistry and their biological activities were evaluated. The majority of derivatives showed promising antiproliferative activity with IC50 values ranging from 1 to 10 µM on the six human cancer cell lines; cervical (HeLa), breast (MCF-7), prostate (DU-145), lung (A549), liver (HepG2) and colon (HT-29). Among them, some of the congeners 10b, 10g and 10i have shown remarkable cytotoxicity with IC50 values of, < 1 µM against the tested cancer cell lines and found to be more active than etoposide. Topoisomerase-mediated DNA relaxation assay results showed that the derivatives could efficiently inhibit the activity of topoisomerase-II. In addition, flow cytometry analysis on DU-145 cells revealed that these compounds arrest G2/M phase of cell cycle. Further apoptotic studies were also performed on these DU-145 cells, which showed that this class of compounds could induce apoptosis effectively.

Design, synthesis and biological evaluation of 1, 4-dihydro indeno[1,2-c] pyrazole linked oxindole analogues as potential anticancer agents targeting tubulin and inducing p53 dependent apoptosis.

A series of 1, 4-dihydroindeno-[1,2-c] pyrazole linked oxindole conjugates have been synthesized by using Knoevenagel condensation method and further evaluated for their antiproliferative activity against HeLa, A549 and MDA-MB-231 human cancer cell lines along with HEK-293 (normal human embryonic kidney cells). Among the derivatives, compounds 12a, 12b, and 12d showed excellent cytotoxicity with IC50 values ranging between 1.33 to 4.33 µM. Furthermore, detailed biological assays showed that there was accumulation of mitotic cells in G2/M phase, disruption of microtubule network and increase in the G2/M checkpoint proteins (Cyclin B1 and CDK1). Moreover, compound 12d with IC50 value of 1.33 µM showed significant upregulation of tumor suppressor proteins like p53, p21 and pro-apoptotic Bax. The molecular docking analysis demonstrated that these congeners occupy the colchicine binding pocket of the tubulin.

Synthesis of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates as microtubule targeting and apoptosis inducing agents.

A series of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates (5a-aa) were designed, synthesized and evaluated for their cytotoxic potency against a panel of human cancer cell lines like lung (A-549), breast (MDA MB-231), prostrate (DU-145) and colon cancer (HT-29). Preliminary results revealed that some of these conjugates like 5d and 5u exhibited significant antiproliferative effect against human breast cancer (MDA MB-231) with IC50 values of 1.3 and 1.2 µM respectively. To investigate the mechanistic aspects underlying the activity, the detailed biological studies of these promising conjugates (5d and 5u) were carried out on the MDA MB-231 cancer cells. Flow cytometric analysis revealed that these conjugates induce cell-cycle arrest in the G2/M phase. The tubulin polymerization assay suggests that these conjugates effectively inhibit microtubule assembly. In addition, morphological changes, reactive oxygen species (ROS) detection by 2', 7'-dichlorofluorescin diacetate (DCFDA) and annexin V-FITC/PI assays indicate that 5d and 5u induces apoptosis. Furthermore, in silico computational studies, including molecular docking studies have been carried out to rationalise the binding modes of these conjugates with the tubulin protein.

Design, synthesis and biological evaluation of 1,3-diphenyl-1H-pyrazole derivatives containing benzimidazole skeleton as potential anticancer and apoptosis inducing agents.

A series of forty different pyrazole containing benzimidazole hybrids (6-45) have been designed, synthesized and evaluated for their potential anti-proliferative activity against three human tumor cell lines - lung (A549), breast (MCF-7), and cervical (HeLa). Some of the compounds, specifically 9, 17, and 28, showed potent growth inhibition against all the cell lines tested, with IC50 values in the range of 0.83-1.81 µM. Breast cancer cells were used for further detailed studies to understand the mechanism of cell growth inhibition and apoptosis inducing effect of compounds. The morphology, cell migration and long term clonogenic survival of MCF-7 breast cancer cells were severely affected by treatment with these compounds. Flow-cytometry revealed the compounds arrested MCF-7 cells in the G1 phase of the cell cycle via down regulation of cyclin D2 and CDK2. Fluorescent staining and DNA fragmentation studies showed that cell proliferation was inhibited by induction of apoptosis. Moreover, the compounds led to collapse of mitochondrial membrane potential (DΨm) and increased levels of reactive oxygen species (ROS) were noted. The ease of synthesis and the remarkable biological activities make these compounds promising new frameworks for the development of cancer therapeutics.

Synthesis and biological evaluation of podophyllotoxin congeners as tubulin polymerization inhibitors.

A series of new podophyllotoxin derivatives containing structural modifications at C-7, C-8, and C-9 were synthesized and evaluated for their cytotoxic activity against three human cancer cell lines. All the synthesized compounds showed significant growth inhibition with GI50 values in micromolar levels while some of the compounds were several times more potent against MCF-7 and HeLa cell lines than MIAPACA cell line. Three compounds (12a, 12d and 12e) emerged as potent compounds with broad spectrum of cytotoxic activity against all the tested cell lines with GI50 values in the range of 0.01-2.1 µM. These compounds induce microtubule depolymerization and arrests cells at the G2/M phase of the cell cycle. Moreover, compounds 12d and 12e disrupted microtubule network and accumulated tubulin in the soluble fraction in a similar manner to their parent podophyllotoxin scaffold. In addition, structure activity relationship studies within the series were also discussed. Molecular docking studies of these compounds into the colchicine-binding site of tubulin, revealed possible mode of inhibition by these compounds.