Synthesis and anticancer activity of 2-benzylidene indanones through inhibiting tubulin polymerization

In an attempt to discover a potent and selective anticancer agent, gallic acid has been modified to benzylidene indanones as tubulin polymerization inhibitors. These compounds were evaluated against several human cancer cell lines and also evaluated for inhibition of tubulin polymerase in in vitro assays. Three of the analogues exhibited strong cytotoxicity against human cancer cell lines IC(50)=10-880 nM and also showed tubulin polymerization inhibition (IC(50)=0.62-2.04 μM). Compound 9j, the best candidate of the series was found to be non-toxic in acute oral toxicity in Swiss-albino mice up to 1000 mg/kg dose.     

Synthesis and biological evaluation of B-ring modified colchicine and isocolchicine analogs

A series of modified colchicine and isocolchicine analogs (C-7 substituent) were synthesized and evaluated in vitro against a PC3 cancer cell line and for inhibition of microtubule polymerization. The colchicine analogs all displayed strong inhibition of tubulin polymerization, while compounds 6 and 20 also possessed an increased cytotoxic activity as compared to colchicine. More importantly, isocolchicine analogs 7, 15, and 17 showed inhibition of microtubule polymerization with IC(50) values ranging from 58 to 68muM. In addition, 7 displayed strong cytotoxic activity with an IC(50)=93nM which was more potent than colchicine analog 12.     

Synthesis, biological evaluation, and molecular modeling of cinnamic acyl sulfonamide derivatives as novel antitubulin agents

A series of novel cinnamic acyl sulfonamide derivatives (9a-16e) have been designed and synthesized and their biological activities were also evaluated as potential tubulin polymerization inhibitors. Among all the compounds, 10c showed the most potent growth inhibitory activity against B16-F10 cancer cell line in vitro, with an IC(50) value of 0.8μg/mL. Docking simulation was performed to insert compound 10c into the crystal structure of tubulin at colchicine binding site to determine the probable binding model. Based on the preliminary results, compound 10c with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Discovery of 1-benzoyl-3-cyanopyrrolo[1,2-a]quinolines as a new series of apoptosis inducers using a cell- and caspase-based high-throughput screening assay. Part 1: Structure-activity relationships of the 1- and 3-positions

1-Benzoyl-3-cyanopyrrolo[1,2-a]quinoline (2a) was identified as a novel apoptosis inducer through our caspase- and cell-based high-throughput screening assay. Compound 2a had good activity against several breast cancer cell lines but was much less active against several other cancer cell lines. SAR studies of 2a found that substitution at the 4-position of the 1-benzoyl group was important for activity. Replacing the 3-cyano group by an ester or ketone group led to inactive compounds. Interestingly, 4-substituted analogs such as 1-(4-(1H-imidazol-1-yl)benzoyl)-3-cyanopyrrolo[1,2-a]quinoline (2k) were found to be broadly and highly active in the caspase activation assay as well as in the cell growth inhibition assay with low nM EC(50) and GI(50) values in human breast cancer cells T47D, human colon cancer cells HCT116, and hepatocellular carcinoma cancer cells SNU398. Compound 2a was found not to inhibit tubulin polymerization up to 50 microM, while 2k was found to inhibit tubulin polymerization with an IC(50) value of 5 microM, indicating that certain substituents at the 4-position of the 1-benzoyl group can change the mechanism of action.     

Synthesis and preliminary biological evaluation of new anti-tubulin agents containing different benzoheterocycles

A new series of compounds, in which the 2-amino-4-methoxyphenyl ring of phenstatin analogue 5 was replaced with 2- or 3-amino-benzoheterocycles, was synthesized and evaluated for antiproliferative activity and inhibition of colchicine binding. The lack of activity of 3',4'-dimethoxy- and 4'-methoxy-benzoyl derivatives (8 and 9, respectively) indicates that the 3',4',5'-trimethoxybenzoyl moiety is critical for the activity. Two compounds, 7 and 11, displayed potent antiproliferative activity, with IC50 values ranging from 25 to 100 nM against a variety of cancer cell lines. Derivative 11 was more active than CA-4 as an inhibitor of tubulin polymerization. The results demonstrated that the antiproliferative activity was correlated with inhibition of tubulin polymerization.     

Examination of the 1,4-disubstituted azetidinone ring system as a template for combretastatin A-4 conformationally restricted analogue design

A series of novel 1,4-diaryl-2-azetidinones was prepared by stereospecific Staudinger reaction as conformationally restricted analogues of combretastatin A-4 because molecular modeling studies suggested close geometric similarities. They were evaluated for cytotoxicity against a number of human tumor and normal cell lines. Strong potencies were observed, with the best compounds exhibiting IC(50)'s of 25-74 nM against human neuroblastoma IMR 32 cell growth and a variety of other cell lines. Compounds inhibited tubulin polymerization with potencies commensurate with their cytotoxic activity and a more soluble anilino-containing analogue was very effective in inhibiting the growth of AR42J rat pancreatic tumors transplanted into in nude mice. Further studies on this interesting group of compounds as anti-cancer agents appear warranted.     

Design, synthesis and biological evaluation of novel chalcone derivatives as antitubulin agents

A series of novel chalcone derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of tubulin. These compounds were assayed for growth-inhibitory activity against MCF-7 and A549 cell lines in vitro. Compound 3d showed the most potent antiproliferative activity against MCF-7 and A549 cell lines with IC(50) values of 0.03 and 0.95 μg/mL and exhibited the most potent tubulin inhibitory activity with IC(50) of 1.42 μg/mL. Docking simulation was performed to insert compound 3d into the crystal structure of tubulin at colchicines binding site to determine the probable binding model. Based on the preliminary results, compound 3d with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Inhibitors and promoters of tubulin polymerization: synthesis and biological evaluation of chalcones and related dienones as potential anticancer agents

A series of dihalogenated chalcones and structurally related dienones were synthesized and evaluated for their antiproliferative activity in 10 different cancer cell lines and for their effect on microtubule assembly. All compounds showed cytotoxic activity, with IC(50) values in the 5-280 μM range depending on the chalcone structure and the cell line. Five of the compounds were found to be tubulin polymerization inhibitors. In contrast, one of the compounds was found to stabilize tubulin to the same extent as the anticancer drug docetaxel. Molecular modeling suggested that the tubulin inhibitors bind to the colchicine binding site of β-tubulin while the novel tubulin stabilization agent seems to interact with the paclitaxel binding site.     

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 biological evaluation of cinnamido linked benzophenone hybrids as tubulin polymerization inhibitors and apoptosis inducing agents

A new class of hybrid molecules containing cinnamide subunit linked to benzophenone as inhibitors of tubulin polymerization were synthesized and evaluated for their anticancer potential. These hybrids exhibit anticancer activity with IC₅₀ values ranging from 0.06 to 16.3 μM. Compounds 4f and 4g possessing fluoro and trifluoromethyl on the cinnamido subunit showed significant cytotoxic activity with IC₅₀ values 0.06 and 0.09 μM against HeLa cell line, respectively. These compounds showed cell cycle arrest at G2/M phase of the cell cycle and inhibited tubulin polymerization followed by activation of caspase-3 activity and apoptotic cell death. Further in vitro tubulin polymerization assay showed that the level of tubulin inhibition was comparable to that of 2a for the compounds 4f and 4g. Moreover, Hoechst 33258 staining and DNA fragmentation assay suggested that these compounds induce cell death by apoptosis. Overall, the current study demonstrates that the synthesis of benzophenone linked cinnamide subunit conjugates as promising anticancer agents with G2/M arrest and apoptotic-inducing ability via targeting tubulin.     

Phenylimino-10H-anthracen-9-ones as novel antimicrotubule agents-synthesis, antiproliferative activity and inhibition of tubulin polymerization

A novel series of phenylimino-10H-anthracen-9-ones and 9-(phenylhydrazone)-9,10-anthracenediones were synthesized and evaluated for interaction with tubulin and for cytotoxicity against a panel of human tumor cell lines. The 10-(3-hydroxy-4-methoxy-phenylimino)-10H-anthracen-9-one 15h and its dichloro analog 16b were identified as potent inhibitors of tumor cell growth (16b, IC(50) K562 0.11 μM), including multidrug resistant phenotypes. Compound 15h had excellent activity as an inhibitor of tubulin polymerization. Concentration-dependent cell cycle analyzes by flow cytometry confirmed that KB/HeLa cells treated by 15h and 16b were arrested in the G2/M phases of the cell cycle. In competition experiments, 15h strongly displaced radiolabeled colchicine from its binding site on tubulin, showing IC(50) values similar to that of colchicine. The results obtained demonstrate that the antiproliferative activity is related to the inhibition of tubulin polymerization.     

1,1-Diarylalkenes as anticancer agents: dual inhibitors of tubulin polymerization and phosphodiesterase 4

A series of 1,1-diarylalkene derivatives were prepared to optimize the properties of CC-5079 (1), a dual inhibitor of tubulin polymerization and phosphodiesterase 4 (PDE4). By using the 3-ethoxy-4-methoxyphenyl PDE4 pharmacophore as one of the aromatic rings, a significant improvement in PDE4 inhibition was achieved. Compound 28 was identified as a dual inhibitor with potent PDE4 (IC(50)=54 nM) and antitubulin activity (HCT-116 IC(50)=34 nM and tubulin polymerization IC(50) ～1 μM). While the nitrile group at the alkene terminus was generally required for potent antiproliferative activity, its replacement was tolerated if there was a hydroxyl or amino group on one of the aryl rings. Conveniently, this group could also serve as a handle for amino acid derivatization to improve the compounds' solubility. The glycinamide analog 45 showed significant efficacy in the HCT-116 xenograft model, with 64% inhibition of tumor growth upon dosing at 20 mg/kg qd.     

New imidazoquinoxaline derivatives: Synthesis,biological evaluation on melanoma,effect on tubulin polymerization and structure–activity relationships

Microtubules are considered as important targets of anticancer therapy. EAPB0503 and its structural imidazo[1,2-a]quinoxaline derivatives are major microtubule-interfering agents with potent anticancer activity. In this study, the synthesis of several new derivatives of EAPB0503 is described, and the anticancer efficacy of 13 novel derivatives on A375 human melanoma cell line is reported. All new compounds show significant antiproliferative activity with IC₅₀ in the range of 0.077–122 μM against human melanoma cell line (A375). Direct inhibition of tubulin polymerization assay in vitro is also assessed. Results show that compounds 6b, 6e, 6g, and EAPB0503 highly inhibit tubulin polymerization with percentages of inhibition of 99%, 98%, 90%, and 84% respectively. Structure–activity relationship studies within the series are also discussed in line with molecular docking studies into the colchicine-binding site of tubulin.     

Synthesis, biological evaluation, and molecular docking studies of cinnamic acyl 1,3,4-thiadiazole amide derivatives as novel antitubulin agents

A series of cinnamic acyl 1,3,4-thiadiazole amide derivatives (6a-10e) have been designed and synthesized, and their biological activities were also evaluated as potential antiproliferation and tubulin polymerization inhibitors. Among all the compounds, 10e showed the most potent activity in vitro, which inhibited the growth of MCF-7 and A549 cell lines with IC(50) values of 0.28 and 0.52μg/mL, respectively. Compound 10e also exhibited significant tubulin polymerization inhibitory activity (IC(50)=1.16μg/mL). Docking simulation was performed to insert compound 10e into the crystal structure of tubulin at colchicine binding site to determine the probable binding model. Based on the preliminary results, compound 10e with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Synthesis, biological evaluation, and molecular docking studies of 2,6-dinitro-4-(trifluoromethyl)phenoxysalicylaldoxime derivatives as novel antitubulin agents

A series of 2,6-dinitro-4-(trifluoromethyl)phenoxysalicylaldoxime derivatives (1h-20h) have been designed and synthesized, and their biological activities were also evaluated as potential antiproliferation and tubulin polymerization inhibitors. Among all the compounds, 2h showed the most potent activity in vitro, which inhibited the growth of MCF-7, Hep-G2 and A549 cell lines with IC(50) values of 0.70 ± 0.05, 0.68 ± 0.02 and 0.86 ± 0.05 μM, respectively. Compound 2h also exhibited significant tubulin polymerization inhibitory activity (IC(50)=3.06 ± 0.05 μM). The result of flow cytometry (FCM) demonstrated that compound 2h induced cell apoptosis. Docking simulation was performed to insert compound 2h into the crystal structure of tubulin at colchicine binding site to determine the probable binding model. Based on the preliminary results, compound 2h with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Antimitotic activities of 2-phenylindole-3-carbaldehydes in human breast cancer cells

Small molecules such as indoles are attractive as inhibitors of tubulin polymerization. Thus a number of 2-phenylindole-3-carbaldehydes with lipophilic substituents in both aromatic rings was synthesized and evaluated for antitumor activity in MDA-MB 231 and MCF-7 breast cancer cells. Some 5-alkylindole derivatives with a 4-methoxy group in the 2-phenyl ring strongly inhibit the growth of breast cancer cells with IC(50) values of 5-20nM. Their action can be rationalized by the cell cycle arrest in G(2)/M phase due to the inhibition of tubulin polymerization.     

Synthesis, biochemical evaluation of a range of potent 4-substituted phenyl alkyl imidazole-based inhibitors of the enzyme complex 17alpha-Hydroxylase/17,20-Lyase (P45017alpha)

We report the synthesis, biochemical evaluation and rationalisation of the inhibitory activity of a number of azole-based compounds as inhibitors of the two components of the cytochrome P-450 enzyme 17alpha-hydroxylase/17,20-lyase (P450(17alpha)), i.e. 17alpha-hydroxylase (17alpha-OHase) and 17,20-lyase (lyase). The results suggest that the compounds synthesised are potent inhibitors, with 7-phenyl heptyl imidazole (11) (IC(50)=320 nM against 17alpha-OHase and IC(50)=100 nM against lyase); 1-[7-(4-fluorophenyl) heptyl] imidazole (14) (IC(50)=170 nM against 17alpha-OHase and IC(50)=57 nM against lyase); 1-[5-(4-bromophenyl) pentyl] imidazole (19) (IC(50)=500 nM against 17alpha-OHase and IC(50)=58 nM against lyase) being the most potent inhibitors within the current study, in comparison to ketoconazole (KTZ) (IC(50)=3.76 microM against 17alpha-OHase and IC(50)=1.66 microM against lyase). Furthermore, consideration of the inhibitory activity against the two components shows that all of the compounds tested are less potent towards the 17alpha-OHase in comparison to the lyase component, a desirable property in the development of novel inhibitors of P450(17alpha). From the modelling of these compounds onto the novel substrate heme complex (SHC) for the overall enzyme complex, the length of the compound, along with its ability to undergo interaction with the active site corresponding to the C(3) area of the steroidal backbone, are suggested to play a key role in determining the overall inhibitory activity.     

Synthesis and biological evaluation of 2-amino-3-(3',4',5'-trimethoxybenzoyl)-6-substituted-4,5,6,7-tetrahydrothieno[2,3-c]pyridine derivatives as antimitotic agents and inhibitors of tubulin polymerization

Microtubules are among the most successful targets of compounds potentially useful for cancer therapy. A new series of inhibitors of tubulin polymerization based on the 2-amino-3-(3,4,5-trimethoxybenzoyl)-4,5,6,7-tetrahydrothieno[b]pyridine molecular skeleton was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. The most promising compound in this series was 2-amino-3-(3,4,5-trimethoxybenzoyl)-6-methoxycarbonyl-4,5,6,7-tetrahydrothieno[b]pyridine, which inhibits cancer cell growth with IC(50)-values ranging from 25 to 90 nM against a panel of four cancer cell lines, and interacts strongly with tubulin by binding to the colchicine site. In this series of N(6)-carbamate derivatives, any further increase in the length and in the size of the alkyl chain resulted in reduced activity.     

The total synthesis of an aurone isolated from Uvaria hamiltonii: aurones and flavones as anticancer agents

The naturally occurring aurone 1, isolated from Uvaria hamiltonii, and a series of aurones analogues based structurally on known tubulin binding agents were prepared and evaluated for anticancer activity. Aurone 20 was the most active (IC(50) K562 50 nM) and caused significant G2/M cell-cycle arrest.     

Synthesis of unsymmetrical biphenyls as potent cytotoxic agents

Twenty-six unsymmetrical biphenyls were synthesized and evaluated for cytotoxic activity against DU145, A549, KB and KB-Vin tumor cell lines. Three compounds 27, 35 and 40 showed very potent activity against the HTCL panel with an IC(50) value range of 0.04-3.23 microM. In addition, fourteen active compounds were all more potent against the drug-resistant KB-Vin cell line than the parental KB cell line. Preliminary SAR analysis indicated that two bulky substituents on the 2,2'-positions of unsymmetrical biphenyl skeleton are necessary and crucial for in vitro anticancer activity, thus providing a good starting point to develop unsymmetrical biphenyls as novel anticancer agents.