Imidazo[1,2-a]pyridines linked with thiazoles/thiophene motif through keto spacer as potential cytotoxic agents and NF-κB inhibitors

A series of new imidazo[1,2-a]pyridine linked with thiazole/thiophene motif through a keto spacer were synthesized and tested for their cytotoxic potential against three human cancer cell lines including A549, HeLa and U87-MG using MTT assay. Compounds A2, A3, A4, C1 and C2 showed cytotoxicity against all the three cell lines. The selectivity index for compound A4 for A549 and HeLa cells was comparable to that of doxorubicin. Among the synthesized compounds, B5 showed the maximum inhibition of NF-κB activity as ascertained by NF-κB reporter assay (IC₅₀?=?6.5?±?0.6?µM). Treatment of NCI-H23 cells (EGFR overexpressed, KRAS G12V mutant) with erlotinib and gefitinib along with compounds A4 and B5 indicated synergistic and additive potential of combination therapy.     

Acyl derivatives of boswellic acids as inhibitors of NF-κB and STATs

Boswellic acid acylates including their epimers were synthesized and screened against a panel of human cancer cell lines. They exhibited a range of cytotoxicity against various human cancer cell lines thereby leading to the development of a possible SAR. One of the identified lead compounds was found to be an inhibitor of the NF-κB and STAT proteins, warranting further investigations to be developed into a potential anticancer lead.     

Design,synthesis and anticervical cancer activity of new benzofuran–pyrazol-hydrazono- thiazolidin-4-one hybrids as potential EGFR inhibitors and apoptosis inducing agents

This study represents the synthetic approaches of a new set of 2-(((3-(benzofuran-2-yl)-1-phenyl-1H-pyrazol-4-yl)methylene)hydrazono)-5-(aryl)thiazolidin-4-one derivatives 4–22 aiming to obtain new antiproliferative candidates against human cervix carcinoma cells (Hela) of EGFR PK inhibiting potency. The cancer cells represented promising sensitivity towards the compounds 6, 7, 11, 13, 14, 16, 17 more than or equal to that against the reference drug doxorubicin. In addition, the latter compounds were tested as EGFR protein kinase inhibitors. The results revealed that compound 14 showed more significant EGFR PK inhibitory activity than the reference drug erlotinib (IC50; 0.07, 0.08 µM, respectively). Moreover, cell cycle analysis and apoptosis assay were performed for compound 14 proving its ability to cause G1/S phase arrest and apoptosis in Hela cancer cells, in addition to its activation of the caspases-7 and -3. In addition, derivative 14 increased the expression level of p53 and the ratio of Bax/Bcl-2 which confirmed its mode of action. Molecular docking study of 14 was performed to investigate its binding mode of interaction with EGFR PK in the active site with the aim of rationalizing its promising inhibitory activity. Accordingly, compound 14 might be considered as a promising scaffold anticervical cancer chemotherapeutic and deserves further optimization and in-depth biological studies.     

Rugulactone derivatives act as inhibitors of NF-κB activation and modulates the transcription of NF-κB dependent genes in MDA-MB-231cells

Rugulactone and its analogues were synthesized following Horners–Wadsworth–Emmons and ring-closing metathesis as the key reactions. A library of new rugulactone analogues were designed, synthesized and evaluated for their anticancer activity in breast cancer cells. All analogues have shown anti-proliferative activity, while some of them exhibited significant cytotoxicity. In assays related to cell-cycle distribution, these conjugates induced G1 cell-cycle arrest in MDA-MB-231 cells. The cell cycle arrest nature was further confirmed by examining the effect on Cyclin E and Cdk2 proteins that acts at G1-S phase transition. Immunocytochemistry assay revealed that these compounds inhibited nuclear translocation of NF-κB protein, thereby activation of NF-κB was inhibited. The expression of NF-κB target genes such as Cyclin D1 and Bcl-xL were severely affected. Apart from acting on NF-κB, these compounds also regulate class I Histone deacetylase proteins such as (HDAC-3 and 8) that have a crucial and regulatory role in cell-proliferation. Simultaneously, the apoptotic inducing nature of these compounds was confirmed by activation of PARP protein, a protein that plays a key role in DNA damage and repair pathways. Among all compounds of this series 3g is the most potent compound and can be used for further studies.     

Theoretical studies on pyrimidine substituent derivatives as dual inhibitors of AP-1 and NF-κB

Theoretical studies on the three-dimensional (3D) quantitative structure-activity relationship (QSAR) and mechanisms of action of a series of pyrimidine substituent derivatives as dual inhibitors of AP-1 and NF-κB were carried out using comparative molecular field analysis (CoMFA) and docking methods. The established 3D-QSAR model exhibits a satisfying statistical quality and prediction ability. Docking results show somewhat lower average values of the flexible and rigid energy scores in the chosen binding sites. The docking analysis offers appropriate orientations and conformations of these compounds at the binding sites to both AP-1 and NF-κB in good agreement with the 3D-QSAR model from CoMFA. The combined CoMFA and docking study suggests the following substituent selections: substituent R₂ should be a kind of H–N–thienyl or CH₃–N–thienyl group; substituent R₅ should be a kind of COO–tBu or COOEt group; and substituent R₄ should be a CH₂CH₃ or 2-thienyl group. The docking analysis also shows that the binding sites fall just at the joint regions between AP-1 (or NF-κB) and DNA, where these compounds can effectively prevent free AP-1 and NF-κB from binding to DNA, and this may be the reason that derivatives with pyrimidine substituents have an inhibition function. In addition, a very interesting finding was that the binding sites of both AP-1 and NF-κB have a common structural characteristic, thereby providing a reasonable explanation for the dual inhibition functions of these compounds towards both AP-1 and NF-κB. These theoretical results help to deepen our understanding of the inhibition mechanism of these pyrimidine substituent derivatives, and will aid in directing further drug-molecular design.     

Antitumor agents 294. Novel E-ring-modified camptothecin-4β-anilino-4'-O-demethyl-epipodophyllotoxin conjugates as DNA topoisomerase I inhibitors and cytotoxic agents

Two conjugates (1 and 2) of camptothecin (CPT) and 4β-anilino-4'-O-demethylepipodophyllotoxin were previously shown to exert antitumor activity through inhibition of topoisomerase I (topo I). In this current study, two novel conjugates (1E and 2E) with an open E-ring in the CPT moiety were first synthesized and evaluated for biological activity in comparison with their intact E-ring congeners. This novel class of CPT-derivatives exhibits its antitumor effect against CPT-sensitive and -resistant cells, in part, by inhibiting topo I-linked DNA (TLD) religation. An intact E-ring was not essential for the inhibition of TLD religation, although conjugates with an open E-ring were less potent than the closed ring analogs. This lower religation potency resulted in decreased formation of protein-linked DNA breaks (PLDBs), and hence, less cell growth inhibition. In addition to their impact on topo I, conjugates 1E, 2, and 2E exhibited a minor inhibitory effect on topo II-induced DNA cleavage. The novel structures of 1E and 2E may present scaffolds for further development of dual function topo I and II inhibitors with improved pharmacological profiles and physicochemical properties.     

Synthesis and in vitro cytotoxicity evaluation of β-carboline-combretastatin carboxamides as apoptosis inducing agents: DNA intercalation and topoisomerase-II inhibition

To explore a new set of cytotoxic agents, β-carboline-combretastatin carboxamide conjugates were designed, synthesized and evaluated for their in vitro cytotoxicity potential, DNA binding affinity and Topoisomerase-II (topo-II) inhibition activity. Among the designed hybrids, 10v and 10af have shown significant cytotoxic effect against A549 (lung cancer) cell line having IC₅₀ value 1.01 µM and 1.17 µM respectively. Further, it was speculated that treatment with compound 10v may induce apoptosis among A549 cells, which was supported by Hoechst staining, DCFDA, Annexin V-FITC and morphological assays. Flow cytometric analysis revealed that the hybrid 10v arrests A549 cells in G2/M phase of cell cycle in a dose dependent manner. Amongst the active hybrids, most potent hybrid 10v was tested for DNA topo-II inhibition activity. Moreover, to further support the biological activity and to infer the mode of interaction between ligands and DNA, spectroscopy and molecular docking studies were carried out. The docking and spectroscopy results showed that the ligands exhibited an intercalative mode of binding with DNA and could efficiently bind to DNA and form topo-II ternary complex. Based on these experiments, the hybrids 10v and 10af were identified as proficient new scaffolds which need to be developed as hit molecules for therapeutic interest.     

Discovery of novel antitumor dibenzocyclooctatetraene derivatives and related biphenyls as potent inhibitors of NF-κB signaling pathway

Several dibenzocyclooctatetraene derivatives (5–7) and related biphenyls (8–11) were designed, synthesized, and evaluated for inhibition of cancer cell growth and the NF-κB signaling pathway. Compound 5a, a dibenzocyclooctatetraene succinimide, was discovered as a potent inhibitor of the NF-κB signaling pathway with significant antitumor activity against several human tumor cell lines (GI₅₀ 1.38–1.45 μM) and was more potent than paclitaxel against the drug-resistant KBvin cell line. Compound 5a also inhibited LPS-induced NF-κB activation in RAW264.7 cells with an IC₅₀ value of 0.52 μM, prevented IκB-α degradation and p65 nuclear translocation, and suppressed LPS-induced NO production in a dose-dependent manner. The antitumor data in cellular assays indicated that relative positions and types of substituents on the dibenzocyclooctatetraene or acyclic biphenyl as well as torsional angles between the two phenyls are of primary importance to antitumor activity.     

Downregulation of NF-κB and PCNA in the regulatory pathways of apoptosis by cyclooxygenase-2 inhibitors in experimental lung cancer

Non-steroidal anti-inflammatory drugs (NSAIDs) are emerging as novel chemopreventive agents against a variety of cancers owing to their capability in blocking the tumor development by cellular proliferation, angiogenesis and by promoting apoptosis. The present study further explored the comparative role of a traditional NSAID, indomethacin and a newly developed coxib, etoricoxib against 9,10-dimethylbenz(a)anthracene (DMBA)-induced lung carcinogenesis in rats. Morphological and histological analysis revealed the occurrence of tumors and lesions along with constricted alveolar spaces in the DMBA treated animals which were largely corrected both by indomethacin and etoricoxib. COX-1 was found to be uniformly expressed in all the groups while COX-2 levels were raised prominently in the DMBA treated animals. Proliferation, as studied by PCNA expression was found to be markedly increased in the DMBA group as compared to the others. Increased NF-κB expression in the DMBA group was found to correct with the co-administration of NSAIDs. Also, fluorescent co-staining of the isolated lung cells revealed a significantly decreased apoptosis and altered mitochondrial membrane potential. In conclusion, these parameters indicate to the chemopreventive action of the two NSAIDs studied in lung cancer and as their mechanism of action suggests, can be achievable both by COX-dependent and COX-independent pathways.