Synthesis and mechanistic aspects of 2-anilinonicotinyl-pyrazolo[1,5-a]pyrimidine conjugates that regulate cell proliferation in MCF-7 cells via estrogen signaling.

A series of anilinonicotinyl linked pyrazolo[1,5-a]pyrimidine conjugates (6a-x) were synthesized and evaluated for their antiproliferative activity. Some of these conjugates exhibited promising cytotoxic effects in the MCF-7 cell line and among these 6a and 6c exhibited significant effects, apart from G2/M cell cycle arrest. Interestingly they showed profound effects on cyclin D1, Bcl-2 and survivin proteins that regulate breast cancer cell proliferation. Moreover, ER alpha protein expression was studied to understand regulatory role of these conjugates on estrogen activity in estrogen positive breast cancer cells like MCF-7 and compounds 6a and 6c reduced their activity.

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.

Synthesis and study of benzothiazole conjugates in the control of cell proliferation by modulating Ras/MEK/ERK-dependent pathway in MCF-7 cells.

By applying a methodology, a series of benzothiazole-pyrrole based conjugates (4a-r) were synthesized and evaluated for their antiproliferative activity. Compounds such as 4a, 4c, 4e, 4g-j, 4m, 4n, 4o and 4r exhibited significant cytotoxic effect in the MCF-7 cell line. Cell cycle effects were examined for these conjugates at 2 µM as well as 4 µM concentrations and FACS analysis show an increase of G2/M phase cells with concomitant decrease of G1 phase cells thereby indicating G2/M cell cycle arrest by them. Interestingly 4o and 4r are effective in causing apoptosis in MCF-7 cells. Moreover, 4o showed down regulation of oncogenic expression of Ras and its downstream effector molecules such as MEK1, ERK1/2, p38 MAPK and VEGF. The apoptotic aspect of this conjugate is further evidenced by increased expression of caspase-9 in MCF-7 cells. Hence these small molecules have the potential to control both the cell proliferation as well as the invasion process in the highly malignant breast cancers.

4ß-[4'-(1-(Aryl)ureido)benzamide]podophyllotoxins as DNA topoisomerase I and IIα inhibitors and apoptosis inducing agents.

A series of 4ß-[4'-(1-(aryl)ureido)benzamide]podophyllotoxin congeners (11a-l) were synthesized and evaluated for their cytotoxic activity against six human cancer cell lines. Some of the compounds like 11a, 11h, 11k and 11l showed significant anti-proliferative activity in Colo-205 cells and were superior to etoposide. The flow-cytometric analysis studies indicated that these compounds show strong G1 cell cycle arrest, as well exhibited improved inhibitory activities on DNA topoisomerase I and IIα enzymes. These compounds induce apoptosis by up regulating caspase-3 protein as observed by ELISA and Western blotting analysis. In addition, a brief structure-activity relationship studies within the series along with docking results of representative compounds 11a, 11h, 11k, 11l were presented.

Synthesis and biological evaluation of diaryl ether linked DC-81 conjugates as potential antitumor agents.

A series of new diaryl ether linked pyrrolobenzodiazepine (PBD) conjugates (4a-i, 5a-i and 6a-f) was synthesized and evaluated for their anticancer activity against a panel of 11 human cancer cell lines. These conjugates exhibited significant anticancer activity with GI50 values in the range of 0.1-3.88 µM. Some of the potent conjugates (4b, 4h, 5h, 6b, 6c and 6e) were further investigated on cell cycle distribution. FACS analysis showed the accumulation of cells in G0 phase indicating the apoptosis inducing nature of these conjugates. Moreover, compound 6b caused a decrease in the mitochondrial membrane potential, which indicates the apoptotic nature of the compound through mitochondrial mediated pathway. Further conjugates 4b, 4h and 6b induce the activation of caspase and PARP proteins, followed by apoptotic cell death in MCF7 cell line.

Synthesis and biological evaluation of combretastatin-amidobenzothiazole conjugates as potential anticancer agents.

A series of combretastatin-amidobenzothiazole conjugates have been synthesized and evaluated for their anticancer activity. All these compounds exhibited significant anticancer activity and the most potent compound (11a) showed GI(50) values ranging 0.019-11 µM. Biological studies such as cell cycle distribution, effect on tubulin polymerization and effect on ERK signalling pathway have been examined in MCF-7 cell line. FACS analysis revealed that these compounds induced cell cycle arrest at G2/M phase. Compound 11a showed significant effect on tubulin polymerization and affected the ERK signalling pathway that result in the decreased levels of ERK1/2, p-ERK and c-Jun proteins. Docking experiments have shown that the active molecules interact and bind well in the ATP binding pocket of ERK protein.

Synthesis and biological evaluation of novel triazoles and isoxazoles linked 2-phenyl benzothiazole as potential anticancer agents.

A new series of isoxazoles and triazoles linked 2-phenyl benzothiazole were synthesized and evaluated for their anticancer activity. These compounds have been tested for their cytotoxicity three cancer cell lines. Among the compounds tested, compound 5d showed good cytotoxicity against Colo-205 and A549 cells in comparison to standard control PMX 610(1). Further compound 5d has been tested for its apoptotic activity and its inhibitory activity against caspase and PARP proteins. Hence this compound has the potential that it can be selected for further biological studies.

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.

Plant HDAC inhibitor chrysin arrest cell growth and induce p21WAF1 by altering chromatin of STAT response element in A375 cells.

BACKGROUND: Chrysin and its analogues, belongs to flavonoid family and possess potential anti-tumour activity. The aim of this study is to determine the molecular mechanism by which chrysin controls cell growth and induce apoptosis in A375 cells. METHODS: Effect of chrysin and its analogues on cell viability and cell cycle analysis was determined by MTT assay and flowcytometry. A series of Western blots was performed to determine the effect of chrysin on important cell cycle regulatory proteins (Cdk2, cyclin D1, p53, p21, p27). The fluorimetry and calorimetry based assays was conducted for characterization of chrysin as HDAC inhibitor. The changes in histone tail modification such as acetylation and methylation was studied after chrysin treatment was estimated by immuno-fluorescence and western blot analysis. The expression of Bcl-xL, survivin and caspase-3 was estimated in chrysin treated cells. The effect of chrysin on p21 promoter activity was studied by luciferase and ChIP assays. RESULTS: Chrysin cause G1 cell cycle arrest and found to inhibit HDAC-2 and HDAC-8. Chrysin treated cells have shown increase in the levels of H3acK14, H4acK12, H4acK16 and decrease in H3me2K9 methylation. The p21 induction by chrysin treatment was found to be independent of p53 status. The chromatin remodelling at p21WAF1 promoter induces p21 activity, increased STAT-1 expression and epigenetic modifications that are responsible for ultimate cell cycle arrest and apoptosis. CONCLUSION: Chrysin shows in vitro anti-cancer activity that is correlated with induction of histone hyperacetylation and possible recruitment of STAT-1, 3, 5 proteins at STAT (-692 to -684) region of p21 promoter. Our results also support an unexpected action of chrysin on the chromatin organization of p21WAF1 promoter through histone methylation and hyper-acetylation. It proposes previously unknown sequence specific chromatin modulations in the STAT responsive elements for regulating cell cycle progression negatively via the induction of the CDK inhibitor p21WAF1.

Synthesis and biological evaluation of 4ß-sulphonamido and 4ß-[(4'-sulphonamido)benzamide]podophyllotoxins as DNA topoisomerase-IIα and apoptosis inducing agents.

A series of new 4ß-sulphonamido and 4ß-[(4'-sulphonamido)benzamide] conjugates of podophyllotoxin (11a-j and 15a-g) were synthesized and evaluated for anticancer activity against six human cancer cell lines and found to be more potent than etoposide. Some of the compounds 11b, 11d and 11e that showed significant antiproliferative activity in Colo-205 cells, were superior to etoposide. The flow cytometric analysis indicates that these compounds (11b, 11d and 11e) showed G2/M cell cycle arrest and among them 11e is the most effective. It is observed that this compound (11e) caused both single-strand DNA breaks as observed by comet assay as well as double-strand DNA breaks as indicated by γ-H2AX. Further 11e showed inhibition of topo-IIα as observed from Western blot analysis and related studies. Compounds caused activation of ATM as well as Chk1 protein indicating that the compound caused effective DNA damage. Moreover activation of caspase-3, p21, p16, NF-kB and down regulation of Bcl-2 protein suggests that this compound (11e) has apoptotic cell death inducing ability, apart from acting as a topo-IIα inhibitor.

3-substituted 2-phenylimidazo[2,1-b]benzothiazoles: synthesis, anticancer activity, and inhibition of tubulin polymerization.

A new series of 3-substituted 2-phenylimidazo[2,1-b]benzothiazoles (3 a-h) were synthesized by C-arylation of 2-arylimidazo[2,1-b]benzothiazoles using palladium acetate as catalyst, and the resulting compounds were evaluated for their anticancer activity. Compounds 3 a, 3 e, and 3 h exhibited good antiproliferative activity, with GI50 values in the range of 0.19-83.1 µM. Compound 3 h showed potent anticancer efficacy against 60 human cancer cell lines, with a mean GI50 value of 0.88 µM. This compound also induced cell-cycle arrest in the G2/M phase and inhibited tubulin polymerization followed by activation of caspase-3 and apoptosis. A high-throughput tubulin polymerization assay showed that the level of inhibition for compound 3 h is similar to that of combretastatin A-4. Molecular modeling studies provided a molecular basis for the favorable binding of compounds 3 a, 3 e, and 3 h to the colchicine binding pocket of tubulin.

Synthesis, anticancer activity and apoptosis inducing ability of bisindole linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

A series of bisindole-pyrrolobenzodiazepine conjugates (5a-f) linked through different alkane spacers was prepared and evaluated for their anticancer activity. All compounds exhibited significant anticancer potency and the most potent compounds 5b and 5e were taken up for detailed studies on MCF-7 cell line. Cell cycle effects were examined apart from investigating the inhibition of tubulin polymerization for compounds 2a, 2b, 5b and 5e at 2µM. FACS analysis showed that at higher concentrations (4 and 8µM) there was an increase of sub-G1 phase cells and decrease of G2/M phase cells, thus indicating that compounds 5b and 5e are effective in causing apoptosis in MCF-7 cells. It was also observed that compounds 5b and 5e showed the down regulation of histone deacetylase protein levels such as HDAC1, 2, 3, 8 and increase in the levels of p21, followed by apoptotic cell death. The apoptotic nature of these compounds was further evidenced by increased expression of cleaved-PARP and active caspase-7 in MCF-7 cells.

Synthesis and apoptosis inducing ability of new anilino substituted pyrimidine sulfonamides as potential anticancer agents.

A series of anilino substituted pyrimidine sulfonamides were prepared and evaluated for their anticancer activity. These sulfonamides showed promising activity with IC(50) values ranging from 5.6 to 12.3 µM. The detailed biological aspects of some of the promising compounds (3d, 3e and 3g) on the K562 cell line were studied. Interestingly, compounds induced G1 cell cycle arrest and down regulation of G1 phase cell cycle regulatory proteins such as cyclin D1, CDK4. These compounds also exhibited inhibition of NF-κB as well as its downstream target gene Akt1 and the phosphorylated form of AKt ser 474 proteins. One of the representative compound 3e could be considered as the potential lead for its development as a new anticancer agent.

Synthesis and biological evaluation of 4ß-acrylamidopodophyllotoxin congeners as DNA damaging agents.

A series of new 4ß-acrylamidopodophyllotoxin derivatives (13a-o) were synthesized by coupling of substituted acrylic acids (10a-l and 11m-o) to the 4ß-aminopodophyllotoxin. The synthesized derivatives 13a-o were evaluated for their cytotoxicity against five human cancer cell lines (breast, oral, colon, lung and ovarian). These podophyllotoxin conjugates have shown promising activity with GI50 values ranging from <0.1 to 0.29 µM. Some of the compounds 13j, 13k and 13l that showed significant antiproliferative activity were also evaluated for related cytotoxic effects in MCF-7 cells, and compared to etoposide. These compounds (13j, 13k and 13l) showed G2/M cell cycle arrest and the apoptotic event was found to be due to both the single-strand DNA breaks as observed by comet assay as well as double-strand breaks as observed by the large accumulation of gamma H2AX foci.

Synthesis of aryl-substituted naphthalene-linked pyrrolobenzodiazepine conjugates as potential anticancer agents with apoptosis-inducing ability.

A library of new aryl-substituted naphthalene C8-linked pyrrolo[2,1-c][1,4]benzodiazepine (PBD) conjugates with various linker architectures were designed, synthesized, and evaluated for their anticancer activity against a panel of 11 human cancer cell lines. All 32 conjugates show anticancer potential, with some of them exhibiting particularly high activity (0.01-0.19 µM). Thermal denaturation studies showed effective DNA binding capacity relative to DC-81. In assays for biological activity relating to cell-cycle distribution, these PBD conjugates induce G0/G1-phase arrest and also cause an increase in the levels of p53 and caspase-9 proteins, followed by apoptotic cell death. One conjugate in particular is the most promising candidate of the series, with the potential to be selected for further studies, either alone or in combination with existing anticancer therapies.

Synthesis and biological evaluation of novel Mannich bases of 2-arylimidazo[2,1-b]benzothiazoles as potential anti-cancer agents.

A new series of Mannich bases of 2-arylimidazo[2,1-b]benzothiazoles were synthesized and evaluated for their anti-cancer activity. These compounds showed better cytotoxicity activity with IC(50) values ranging from 2.8 to 8.0 µM in HepG2, MCF-7 and HeLa cell lines. Further mechanism aspects responsible for the anti-cancer activity of two promising compounds 3c and 3f in HepG2 cell line were studied. Interestingly, 3c, 3f induced G2/M cell cycle arrest with down regulation of cyclin B and up regulation of Chk2 protein. Moreover, compounds 3c, 3f also showed the characteristic features of apoptosis such as enhancement in the levels of caspase-3. Treatments with compounds led to a decrease in levels of vital cell proliferation proteins such as Jun (C-Jun, JunB), p38 MAPK, p-JNK and PKCα. The compound 3f of the series could be considered as the potential lead for its development as a novel anti-cancer agent.

Synthesis and anticancer activity of chalcone-pyrrolobenzodiazepine conjugates linked via 1,2,3-triazole ring side-armed with alkane spacers.

Aiming to develop multitarget drugs for the anticancer treatment, a new class of chalcone-pyrrolo[2,1-c] [1,4]benzodiazepine (PBD) conjugates linked through a 1,2,3-triazole moiety containing alkane spacers has been designed and synthesized. Combining these two core pharmacophore structures with modifications at A-C8/C-C2-position of PBD ring system yielded analogs with improved efficacy and have shown promising in vitro anticancer activity ranging from <0.1-2.92 µM. These PBD-conjugates caused G1 cell cycle arrest with effect on G1 cell cycle regulatory proteins such as Cyclin D1 and Cdk4. These conjugates also exhibited inhibitory effect on NF-kB, Bcl-XL proteins that play a vital role in breast cancer cell proliferation. These findings suggest that one of the compound 4d among this series is most effective and has potential for detailed investigations.

Synthesis and biological evaluation of estradiol linked pyrrolo[2,1-c][1,4]benzodiazepine (PBD) conjugates as potential anticancer agents.

A series of new estradiol linked pyrrolo[2,1-c][1,4]benzodiazepine (E(2)-PBD) conjugates (3a-f, 4a-f and 5a-f) with different linker architectures including a triazole moiety have been designed and synthesized. All the 18 compounds have been evaluated for their anticancer activity and it is observed that some of the compounds particularly 4c-e and 5c,d exhibited significant anticancer activity. The detailed biological aspects relating to the cell cycle effects and tubulin depolymerization activity have been examined with a view to understand the mechanism of action of these conjugates. Among all these conjugates, one of the compound 5c could be considered as the most effective compound particularly against MCF-7 breast cancer cell line.

Synthesis and biological evaluation of 3,5-diaryl isoxazoline/isoxazole linked 2,3-dihydroquinazolinone hybrids as anticancer agents.

A series of new 3,5-diaryl isoxazoline/isoxazole linked 2,3-dihydro quinazolinone hybrids with different linker architectures have been designed and synthesized. These compounds have been evaluated for their anticancer activity. One of the compounds 4c amongst this series has shown promising anticancer activity. Further some detailed biological assays relating to the cell cycle aspects and tubulin depolymerization activity have been examined with a view to understand the mechanism of action of this conjugate.

Synthesis of imidazothiazole-chalcone derivatives as anticancer and apoptosis inducing agents.

A new class of imidazo[2,1-b]thiazole chalcone derivatives were synthesized and evaluated for their anticancer activity. These chalcone derivatives show promising activity, with log GI(50) values ranging from -7.51 to -4.00. The detailed biological aspects of these derivatives toward the MCF-7 cell line were studied. Interestingly, these chalcone derivatives induced G(0)/G(1)-phase cell-cycle arrest, down-regulation of G(1)-phase cell-cycle regulatory proteins such as cyclin D1 and cyclin E1, and up-regulation of CDK4. Moreover, these compounds elicit the characteristic features of apoptosis such as enhancement in the levels of p53, p21, and p27, suppression of NF-κB, and up-regulation of caspase-9. One of these chalcone derivatives, 3 d, is potentially well suited for detailed biological studies, either alone or in combination with existing therapies.