Benzimidazole-linked pyrazolo[1,5-a]pyrimidine conjugates: synthesis and detail evaluation as potential anticancer agents.

A library of benzimidazole briged pyrazolo[1,5-a]pyrimidine (6a-q) was designed, synthesized and subjected for evaluation for cytotoxic potential. Antiproliferative activity, ranging from 3.1-51.5 µM, was observed against a panel of cancer cell lines which included MCF-7 (breast cancer), A549 (lung cancer), HeLa (cervical cancer) and SiHa (cervical cancer). Among them, 6k, 6l, 6n and 6o have shown significant cytotoxicity and were investigated further to study their probable mechanism of action against MCF-7 cell line. Accumulation of cells at sub-G1 phase was observed in flow cytometric analysis. The detachment of cells from substratum and membrane blebbing seen under bright field microscopy supports the ability of these conjugates to induce apoptosis. Immunostaining and western blot analysis showed EGFR, p-EGFR, STAT3, and p-STAT3 significant downregulation. Western blot analysis demonstrated an elevated level of apoptotic proteins such as p53, p21, Bax, whereas a decrease in the antiapoptotic protein Bcl-2 and procaspase-9, confirming the ability of these conjugates to trigger cell death by apoptosis. EGFR kinase assay confirms the specific activity of conjugates. Molecular docking simulation study disclosed that these molecules fit well in ATP-binding pocket of EGFR. The analysis of docking poses and the atomic interactions of different conjugates rationalize the structural-activity relationship in this series. Benzimidazole-linked pyrazolo[1,5-a]pyrimidine conjugates were synthesized and evaluated for their anticancer potential. All the conjugates have significant anticancer potential. Further mechanistic studies revealed that these conjugates arrest cancer cell growth by EGFR/STAT3 inhibition.

Synthesis and biological evaluation of chalcone-linked pyrazolo[1,5-a]pyrimidines as potential anticancer agents.

A series of pyrazolo[1,5-a]pyrimidines substituted at C5 with 1-phenylprop-2-en-1-one (6a-q) and 3-phenylprop-2-en-1-one (7a-k) was synthesized and evaluated for antiproliferative activity. Among them, 6h was found to be the most active compound against the MDA-MB-231 cell line with an IC50 of 2.6 µM . The antiproliferative activity of this series of compounds ranged from 2.6 to 34.9 µM against A549 (lung cancer), MDA-MB-231 (breast cancer) and DU-145 (prostate cancer) cell lines. FACS analysis revealed that these hybrids arrest the cell cycle at the subG1 phase. Western blot analysis and an immunofluorescence assay showed the inhibition of the EGFR and STAT3 axis, which plays an important role in cell survival and apoptosis. Western blot and RT-PCR analyses that displayed an increase in apoptotic proteins such as p53, p21 and Bax and a decrease in the anti-apoptotic proteins Bcl-2 and procaspase-9 confirmed the ability of these hybrids to trigger cell death by apoptosis. Molecular docking studies described the binding of these hybrids to the ATP binding site of EGFR.

Synthesis of a terphenyl substituted 4-aza-2,3-didehydropodophyllotoxin analogues as inhibitors of tubulin polymerization and apoptosis inducers.

A series of terphenyl based 4-aza-2,3-didehydropodophyllotoxin conjugates (8a-r) were synthesized by a straightforward one-step multicomponent synthesis that demonstrated anticancer activity against five human cancer cell lines (lung, colon, renal, prostate and cervical). All the tested compounds showed potent anticancer activity with IC50 values ranging from 0.87 to 16.59 µM. Among them compounds 8n and 8p showed significant anticancer activity in lung cancer cells with IC50 values 0.91 and 0.87 µM, respectively. Flow cytometric analysis revealed that these compounds induced cell cycle arrest in G2/M phase in A549 cell line leading to caspase-3 dependent apoptotic cell death. The tubulin polymerization assay and immunofluorescence analysis showed that these compounds effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Further, Hoechst staining, DNA fragmentation analysis also suggested that these compounds induced cell death by apoptosis. Overall, the current study demonstrated that the synthesis of terphenyl based 4-aza-2,3-didehydropodophyllotoxin conjugates as promising anticancer agents with G2/M cell cycle arrest and apoptotic-inducing activities via targeting tubulin.

Quinazolino linked 4ß-amidopodophyllotoxin conjugates regulate angiogenic pathway and control breast cancer cell proliferation.

A series of new conjugates of quinazolino linked 4ß-amidopodophyllotoxins 10aa-af and 10ba-bf were synthesized and evaluated for their anticancer activity against human pancreatic carcinoma (Panc-1) as well as breast cancer cell lines such as MCF-7 and MDA-MB-231 by employing MTT assay. Among these conjugates, some of them like 10bc, 10bd, 10be and 10bf exhibited high potency of cytotoxicity. Flow cytometric analysis showed that these conjugates arrested the cell cycle in the G2/M phase and caused the increase in expression of p53 and cyclin B1 protein with concomitant decrease in Cdk1 thereby suggesting the inhibitory action of these conjugates on mitosis. Interestingly, we observed a decrease in expression of proteins that control the tumor micro environment such as VEGF-A, STAT-3, ERK1/2, ERK-p, AKT-1 ser 473 phosphorylation in compounds treated breast cancer cells. Further, these effective conjugates have exhibited inhibitory action on integrin (αVßIII). Furthermore, the MCF-7 cells that were arrested and lost the proliferative capacity undergo mitochondrial mediated apoptosis by activation of caspases-9. Thus these conjugates have the potential to control breast cancer cell growth by effecting tumor angiogenesis and invasion.

Novel anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates modulate the expression of p53-MYCN associated micro RNAs in neuroblastoma cells and cause cell cycle arrest and apoptosis.

It has previously been shown that anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates activate p53 and cause apoptosis in cervical cancer cells such as HeLa and SiHa. Here we establish the role of these conjugates in activating p53 pathway by phosphorylation at Ser15, 20 and 46 residues and downregulate key oncogenic proteins such as MYCN and Mdm2 in IMR-32 neuroblastoma cells. Compounds decreased the proliferation rate of neuroblastoma cells such as IMR-32, Neuro-2a, SK-N-SH. Compound treatment resulted in G2/M cell cycle arrest. The expression of p53 dependent genes such as p21, Bax, caspases was increased with concomitant decrease of the survival proteins as well as anti-apoptotic proteins such as Akt1, E2F1 and Bcl2. In addition the expression of important microRNAs such as miR-34a, c, miR-200b, miR-107, miR-542-5p and miR-605 were significantly increased that eventually lead to the activation of apoptotic pathway. Our data revealed that conjugates of this nature cause cell cycle arrest and apoptosis in IMR-32 cells [MYCN (+) with intact wild-type p53] by activating p53 signalling and provides a lead for the development of anti-cancer therapeutics.

Synthesis of pyrazolo[1,5-a]pyrimidine linked aminobenzothiazole conjugates as potential anticancer agents.

A series of pyrazolo[1,5-a]pyrimidine linked 2-aminobenzothizole conjugates (6a-t) were synthesized and evaluated for their anticancer activity against five human cancer cell lines. Among them two compounds 6p and 6m showed significant anticancer activity with IC50 values ranging from 2.01 to 7.07 and 1.94-3.46 µM, respectively. Moreover, cell cycle arrest in G2/M and reduction in Cdk1 expression level were observed upon treatment of these compounds and they also induced caspase-3 dependent apoptosis. This was further confirmed by staining as well as DNA fragmentation analysis.

Synthesis and anticancer activity of heteroaromatic linked 4ß-amido podophyllotoxins as apoptotic inducing agents.

A series of different heteroaromatic linked 4ß-amidopodophyllotoxin conjugates (16a-i, 17a-i and 18a-d) were synthesized and evaluated for anticancer activity against five human cancer cell lines. Among the series, one of the compound 17g showed significant antiproliferative activity in A549 (lung cancer) cell line. Flow cytometric analysis showed that 17g arrested the cell cycle in the G2/M phase leading to caspase-3 dependent apoptotic cell death. Further, Hoechst 33258 staining and DNA fragmentation assay also suggests that 17g induces cell death by apoptosis.

Anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates as p53 activators in cervical cancer cells.

A library of new anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates were designed, synthesized, and evaluated for their anticancer activity in cervical cancer cells such as HeLa and SiHa that possess low levels of p53. All 24 conjugates showed antiproliferative activity, while some of them exhibit significant cytotoxicity. In assays related to cell-cycle distribution, these conjugates induced G(2) /M arrest in HeLa cells and G(1) cell-cycle arrest in SiHa cells. Immunocytochemistry assays revealed that these compounds cause nuclear translocation of p53, thereby indicating the activation of p53. In cervical cancer cells, the p53 protein is degraded by E6 oncoprotein. Immunoblot and RT-PCR analyses proved the presence of mitochondria-mediated apoptosis with involvement p53 target genes such as BAX, Bcl2, and p21 (CDKI). Moreover, these compounds increased the phosphorylated forms of p53 and provide signals for apoptosis induction. Interestingly, one of the conjugates, (2-phenyl-7-(3,4,5-trimethoxyphenyl)pyrazolo[1,5-a]pyrimidin-5-yl)(4-(2-(thiophen-2-ylmethylamino)benzoyl)piperazin-1-yl)methanone, is the most promising candidate in this series and has the potential to be taken up for further detailed studies.

Synthesis of chalcone-amidobenzothiazole conjugates as antimitotic and apoptotic inducing agents.

A series of chalcone-amidobenzothiazole conjugates (9a-k and 10a,b) have been synthesized and evaluated for their anticancer activity. All these compounds exhibited potent activity and the IC(50) of two potential compounds (9a and 9f) against different cancer cell lines are in the range of 0.85-3.3 µM. Flow cytometric analysis revealed that these compounds induced cell cycle arrest at G2/M phase in A549 cell line leading to caspase-3 dependent apoptotic cell death. The tubulin polymerization assay (IC(50) of 9a is 3.5 µM and 9f is 5.2 µM) and immuofluorescence analysis showed that these compounds effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Further, Annexin staining also suggested that these compounds induced cell death by apoptosis. Moreover, docking experiments have shown that they interact and bind efficiently with tubulin protein. Overall, the current study demonstrates that the synthesis of chalcone-amidobenzothiazole conjugates as promising anticancer agents with potent G2/M arrest and apoptotic-inducing activities via targeting tubulin.

Synthesis and anticancer activity of 4ß-alkylamidochalcone and 4ß-cinnamido linked podophyllotoxins as apoptotic inducing agents.

A series of 4ß-alkylamidochalcone and 4ß-cinnamido linked podophyllotoxin congeners have been synthesized. All the twenty nine compounds were evaluated for anticancer activity against five human cancer cell lines (A-549, A375, MCF-7, HT-29 and ACHN). Some of the synthesized compounds showed good anticancer activity that is comparable to etoposide. The IC(50) of compounds 17a and 17f is 2.7 and 2.1 µM respectively against A-549 cancer cell line. Flow cytometric analysis showed that these two compounds arrested the cell cycle in the G2/M phase leading to caspase-3 dependent apoptotic cell death. Further, Hoechst 33258 staining and DNA fragmentation assay also suggested that 17a and 17f induced cell death by apoptosis.

Synthesis of a new 4-aza-2,3-didehydropodophyllotoxin analogues as potent cytotoxic and antimitotic agents.

A series of novel conjugates of 4-aza-2,3-didehydropodophyllotoxins (11a-w) were synthesized by a straightforward one-step multicomponent synthesis that demonstrated cytotoxicity against five human cancer cell lines (breast, oral, colon, lung and ovarian). All the twenty three compounds (11a-w) have been examined for the inhibition of tubulin polymerization. Among these compounds, 11a, 11k and 11p exhibited inhibition of polymerization tubulin comparable to podophyllotoxin apart from disruption of microtubule organization within the cells. Flow cytometric analysis showed that these compounds (11a, 11k and 11p) arrested the cell cycle in the G2/M phase of cell cycle leading to caspase-3 dependent apoptotic cell death.