1-p-chlorophenyl-4,4-dimethyl-5-diethylamino-1-penten-3-one hydrobromide, a sulfhydryl-specific compound which reacts irreversibly with protein thiols but reversibly with small molecular weight thiols

Novel Unsymmetric 3,5-Bis(benzylidene)-4-piperidones That Display Tumor-Selective Toxicity

Two series of novel unsymmetrical 3,5-bis(benzylidene)-4 piperidones 2a-f and 3a-e were designed as candidate antineoplastic agents. These compounds display potent cytotoxicity towards two colon cancers, as well as several oral squamous cell carcinomas. These compounds are less toxic to various non-malignant cells giving rise to large selectivity index (SI) figures. Many of the compounds are also cytotoxic towards CEM lymphoma and HL-60 leukemia cells. Representative compounds induced apoptotic cell death characterized by caspase-3 activation and subG1 accumulation in some OSCC cells, as well as the depolarization of the mitochondrial membrane potential in CEM cells. A further line of inquiry was directed to finding if the SI values are correlated with the atomic charges on the olefinic carbon atoms. The potential of these compounds as antineoplastic agents was enhanced by an ADME (absorption, distribution, metabolism, and excretion) evaluation of five lead molecules, which revealed no violations.

Cytotoxic Tumour-Selective 1,5-Diaryl-3-Oxo-1,4-Pentadienes Mounted on a Piperidine Ring

A series of 3,5-bis(benzylidene)-4-piperidones 2a–u were prepared as candidate cytotoxic agents. In general, the compounds are highly toxic to human gingival carcinoma (Ca9-22), human squamous carcinoma-2 (HSC-2) and human squamous carcinoma-4 (HSC-4) neoplasms, but less so towards non-malignant human gingival fibroblast (HGF), human periodontal ligament fibroblast (HPLF) and human pulp cells (HPC), thereby demonstrating tumour-selective toxicity. A further study revealed that most of the compounds in series 2 were more toxic to the human Colo-205 adenocarcinoma cell line (Colo-205), human HT29 colorectal adenocarcinoma cells (HT-29) and human CEM lymphoid cells (CEM) neoplasms than towards non-malignant human foreskin Hs27 fibroblast line (Hs27) cells. The potency of the cytotoxins towards the six malignant cell lines increased as the sigma and sigma star values of the aryl substituents rose. Attempts to condense various aryl aldehydes with 2,2,6,6-tetramethyl-4-piperidone led to the isolation of some 1,5-diaryl-1,4-pentadien-3-ones. The highest specificity for oral cancer cells was displayed by 2e and 2r. In the case of 2r, its selective toxicity exceeded that of doxorubicin and melphalan. The enones 2k, m, o have the highest SI values towards colon cancer and leukemic cells. Both 2e,r inhibited mitosis and increased the subG1 population (with a transient increase in G2/M phase cells). Slight activation of caspase-3, based on the cleavage of poly(ADP-ribose)polymerase (PARP) and procaspase 3, was detected.

Design, Synthesis and Tumour-Selective Toxicity of Novel 1-[3-{3,5-Bis(benzylidene)-4-oxo-1-piperidino}-3-oxopropyl]-4-piperidone Oximes and Related Quaternary Ammonium Salts

A novel series of 1-[3-{3,5-bis(benzylidene)-4-oxo-1-piperidino}-3-oxopropyl]-4-piperidone oximes 3a-h and related quaternary ammonium salts 4a-h were prepared as candidate antineoplastic agents. Evaluation against neoplastic Ca9-22, HSC-2 and HSC-4 cells revealed the compounds in series 3 and 4 to be potent cytotoxins with submicromolar CC50 values in virtually all cases. In contrast, the compounds were less cytocidal towards HGF, HPLF and HPC non-malignant cells revealing their tumour-selective toxicity. Quantitative structure-activity relationships revealed that, in general, both cytotoxic potency and selectivity index figures increased as the magnitude of the Hammett sigma values rose. In addition, 3a-h are cytotoxic towards a number of leukemic and colon cancer cells. 4b,c lowered the mitochondrial membrane potential in CEM cells, and 4d induced transient G2/M accumulation in Ca9-22 cells. Five compounds, namely 3c,d and 4c-e, were identified as lead molecules that have drug-like properties.

Silencing lncRNAs PVT1 Upregulates miR-145 and Confers Inhibitory Effects on Viability, Invasion, and Migration in EC

Long non-coding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) is correlated to various malignant tumors. Consequently, we explored effects of lncRNA PVT1 on esophageal carcinoma (EC) targeting microRNA-145 (miR-145). EC tissues, adjacent normal tissues, and EC-related cell lines were collected and cultured. Expression of lncRNA PVT1, miR-145, fascin-1 (FSCN1), and related genes with intervening expression of PVT1 and miR-145 was determined. Bioinformatic website, dual-luciferase reporter assay, and RNA immunoprecipitation (RIP) were carried to verify target relationship among lncRNA PVT1, FSCN1, and miR-145. Scratch test, Transwell assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and flow cytometry were performed for detection of migration, invasion, viability, and apoptosis of transfected cells, respectively. Finally, tumor formation in nude mice was measured. After database analysis, lncRNA PVT1, miR-145, and FSCN1 were selected for study. lncRNA PVT1 and FSCN1 can bind to miR-145. After overexpressing miR-145 or inhibiting lncRNA PVT1, EC cell viability, migration, and invasion were inhibited, while volume and weight of tumor formation in nude mice decreased. Expression of lncRNA PVT1, FSCN1, Bcl-2, CD147, VEGFR2, and MTA1 decreased and expression of miR-145 and Bax increased. Silencing lncRNA PVT1 can upregulate miR-145, which is a tumor suppressor in EC via knockdown of FSCN1. Thus, we might provide a potential theoretical basis for EC treatment.

Down-regulation of long noncoding RNA PVT1 inhibits esophageal carcinoma cell migration and invasion and promotes cell apoptosis via microRNA-145-mediated inhibition of FSCN1

Accumulating evidence has established that long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) is a tumor regulator in many cancers. Here, we aimed to investigate the possible function of lncRNA PVT1 in esophageal carcinoma (EC) via targeting of microRNA-145 (miR-145). Initially, microarray-based gene expression profiling of EC was employed to identify differentially expressed genes. Moreover, the expression of lncRNA PVT1 was examined and the cell line presenting with the highest level of lncRNA PVT1 expression was selected for subsequent experiments. We then proceeded to examine interaction among lncRNA PVT1, FSCN1, and miR-145. The effect of lncRNA PVT1 on viability, migration, invasion, apoptosis, and tumorigenesis of transfected cells was examined with gain-of-function and loss-of-function experiments. We observed that lncRNA PVT1 was robustly induced in EC. lncRNA PVT1 could bind to miR-145 and regulate its expression, and FSCN1 is a target gene of miR-145. Overexpression of miR-145 or silencing of lncRNA PVT1 was revealed to suppress cell viability, migration, and invasion abilities, while also stimulating cell apoptosis. Furthermore, our in vivo results showed that overexpression of miR-145 or silencing of lncRNA PVT1 resulted in decreased tumor growth in nude mice. In conclusion, our research reveals that down-regulation of lncRNA PVT1 could potentially promote expression of miR-145 to repress cell migration and invasion, and promote cell apoptosis through the inhibition of FSCN1. This highlights the potential of lncRNA PVT1 as a therapeutic target for EC treatment.

Synthesis and biological evaluation of some new mono Mannich bases with piperazines as possible anticancer agents and carbonic anhydrase inhibitors

New mono Mannich bases, (2-(4-hydroxy-3-((4-substituephenylpiperazin-1-yl)methyl)benzylidene)-2,3-dihydro-1H-inden-1-one), were prepared to evaluate their cytotoxic/anticancer properties and also their inhibitory effects on human carbonic anhydrase I and II isoenzymes (hCA I and II). Amine part was changed as [N-phenylpiperazine (1), N-benzylpiperazine (2), 1-(2-fluorophenyl)piperazine (3), 1-(4-fluorophenyl)piperazine (4), 1-(2-methoxyphenyl)piperazine (5)]. The structure of the synthesized compounds was characterized by ¹H NMR, ¹³C NMR and HRMS spectra. Cytotoxicity results of the series pointed out that the compound 4 had the highest tumor selectivity value (TS: 59.4) possibly by inducing necrotic cell death in series. Additionally, all compounds synthesized showed a good inhibition profile towards hCA I and II isoenzymes with the Ki values between 29.6 and 58.4 nM and 38.1-69.7 nM, respectively. These values were lower than the reference compound AZA. However, it seems that the compounds 4 and 2 can be considered as lead compounds of CA studies with the lowest Ki values in series for further designs.

3,5-Bis(3-dimethylaminomethyl-4-hydroxybenzylidene)-4-piperidone and related compounds induce glutathione oxidation and mitochondria-mediated cell death in HCT-116 colon cancer cells

This study aims at investigating the cytotoxicity and some of the modes of action of 3,5-bis(3-dimethylamino-4-hydroxybenzylidene)-4-piperidone trihydrochloride 3 and two related compounds 2 (which lacks the dimethylaminomethyl groups) and 4 (which has an additional dimethylaminoethyl substituent in both aryl rings) in order to ascertain the contribution of dimethylaminoethyl substituent to bioactivity. The bioactivities of 2-4 were compared with curcumin 5. Both 2 and 3 displayed submicromolar GI₅₀ values towards HCT-116 cells and were significantly more potent than 4, 5 and 5-fluorouracil (5-FU). All of the compounds displayed greater toxicity towards HCT-116 cells than human CRL-1790 non-malignant colon cells. In HCT-116 cells, the compounds 2, 3 and 5 increased the ratio of oxidised to reduced glutathione and destabilized the mitochondrial membrane potential. Both 2 and 5 produced an increase in mitochondrial superoxide and a burst in intracellular reactive oxygen species in HCT 116 cells. In addition, 2 and 4 stimulated respiration in rat liver mitochondria while 2 and 5 induced mitochondrial swelling. The results suggest that 2 and 5 cause oxidation or cross-linking of the thiols which control the mitochondrial permeability transition.

Covalent Modifiers: A Chemical Perspective on the Reactivity of α,β-Unsaturated Carbonyls with Thiols via Hetero-Michael Addition Reactions

Although Michael acceptors display a potent and broad spectrum of bioactivity, they have largely been ignored in drug discovery because of their presumed indiscriminate reactivity. As such, a dearth of information exists relevant to the thiol reactivity of natural products and their analogues possessing this moiety. In the midst of recently approved acrylamide-containing drugs, it is clear that a good understanding of the hetero-Michael addition reaction and the relative reactivities of biological thiols with Michael acceptors under physiological conditions is needed for the design and use of these compounds as biological tools and potential therapeutics. This Perspective provides information that will contribute to this understanding, such as kinetics of thiol addition reactions, bioactivities, as well as steric and electronic factors that influence the electrophilicity and reversibility of Michael acceptors. This Perspective is focused on α,β-unsaturated carbonyls given their preponderance in bioactive natural products.

Niacin esters of chalcones with tumor-selective properties

Novel series of niacin esters of chalcones 2, 4 and 6 were designed as antineoplastic agents that have the potential to release the chemoprotectant niacin. These enones are cytotoxic to human CD4(+ )T-lymphocyte Molt 4/C8 and CEM and murine leukemia L1210 cells. Quantitative structure-activity relationship (QSAR) studies of the biodata in series 4 revealed that cytotoxic potency was enhanced by placing electron-repelling groups in one of the aryl rings. The compounds are lethal to HL-60, HSC-2, HSC-3 and HSC-4 neoplasms but less toxic to nonmalignant hepatocyte growth factor, hematopoietic progenitor cell and human periodontal ligament fibroblast cells. Hence, the compounds display tumor-selective toxicity. These chalcones are well tolerated in mice and no overt toxicity was noted. The results establish that in general the compounds in series 2, 4 and 6 have positive characteristics which warrant further studies.

A novel curcumin-like dienone induces apoptosis in triple-negative breast cancer cells

PURPOSE

According to the World Health Organization (WHO), breast cancer is the most common cancer affecting women worldwide. In the USA ~12.3 % of all women are expected to be diagnosed with various types of breast cancer, exhibiting varying degrees of therapeutic response rates. Therefore, the identification of novel anti-breast cancer drugs is of paramount importance.

METHODS

The 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore was incorporated into a number of cytotoxins. Three of the resulting dienones, 2a, 2b and 2c, were tested for their anti-neoplastic potencies in a variety of human breast cancer-derived cell lines, including the triple negative MDA-MB-231 cell line and its metastatic variant, using a live-cell bio-imaging method. Special emphasis was put on dienone 2c, since its anti-cancer activity and its mode of inflicting cell death have so far not been reported.

RESULTS

We found that all three dienones exhibited potent cytotoxicities towards the breast cancer-derived cell lines tested, whereas significantly lower toxicities were observed towards the non-cancerous human breast cell line MCF-10A. The dienones 2b and 2c exhibited the greatest selective cytotoxicity at submicromolar concentration levels. We found that these two dienones induced phosphatidylserine externalization in MDA-MB-231 cells in a concentration-dependent manner, suggesting that their cytotoxic effect might be mediated by apoptosis. This possibility was confirmed by our observation that the dienone 2c can induce mitochondrial depolarization, caspase-3 activation, cell cycle disruption and DNA fragmentation in MDA-MB-231 cells.

CONCLUSION

Our findings indicate that dienone 2c uses the mitochondrial/intrinsic pathway to inflict apoptosis in triple negative MDA-MB-231 breast cancer-derived cells. This observation warrants further assessment of dienone 2c as a potential anti-breast cancer drug.

1-[3-(2-Hydroxyethylsulfanyl)propanoyl]-3,5-bis(benzylidene)-4-piperidones: A novel cluster of P-glycoprotein dependent multidrug resistance modulators

A series of 1-[3-(2-hydroxyethylsulfanyl)propanoyl]-3,5-bis(benzylidene)-4-piperidones 4a-e display promising P-glycoprotein dependent multidrug resistance (MDR) revertant properties and are significantly more potent than a reference drug verapamil when evaluated against L-5178Y MDR lymphoma cells. These dienones may be referred to as dual agents having both MDR revertant properties and tumour-selective cytotoxicity. In particular, 3,5-bis(4-chlorobenzylidene)-1-[3-(2-hydroxyethylsulfanyl]propanoyl-4-piperidone 4d emerged as a lead molecule for further development based on its MDR revertant properties, cytotoxic potencies and tumour-selective toxicity. The structure-activity relationships reveal important structural requirements for further designing of potent MDR revertants.

Synthesis of mono Mannich bases of 2-(4-hydroxybenzylidene)-2,3-dihydroinden-1-one and evaluation of their cytotoxicities

Chalcones and Mannich bases are a group of compounds known for their cytotoxicities. In this study restricted chalcone analogue, compound 2-(4-hydroxybenzylidene)-2,3-dihydroinden-1-one MT1, was used as a starting compound to synthesize new mono Mannich bases since Mannich bases may induce more cytotoxicity than chalcone analogue that they are derived from by producing additional alkylating center for cellular thiols. In this study, cyclic and acyclic amines were used to synthesize Mannich bases. All compounds were tested against Ca9-22 (gingival carcinoma), HSC-2, HSC-3 and HSC-4 (oral squamous cell carcinoma) as tumour cell lines and HGF (gingival fibroblasts), HPC (pulp cells) and HPLF (periodontal ligament fibroblasts) human normal oral cells as non tumour cell lines. Cytotoxicity, selectivity index (SI) values and potency selectivity expression (PSE) values expressed as a percentage were determined for the compounds. According to data obtained, the compound MT8 with the highest PSE value bearing N-methylpiperazine moiety seems to be a good candidate to develop new cytotoxic compounds and is suited for further investigation.

Evaluation of α,β-unsaturated ketones as antileishmanial agents

In this study, we assessed the antileishmanial activity of 126 α,β-unsaturated ketones. The compounds NC901, NC884, and NC2459 showed high leishmanicidal activity for both the extracellular (50% effective concentration [EC50], 456 nM, 1,122 nM, and 20 nM, respectively) and intracellular (EC50, 1,870 nM, 937 nM, and 625 nM, respectively) forms of Leishmania major propagated in macrophages, with little or no toxicity to mammalian cells. Bioluminescent imaging of parasite replication showed that all three compounds reduced the parasite burden in the murine model, with no apparent toxicity.

All trans 1-(3-arylacryloyl)-3,5-bis(pyridin-4-ylmethylene)piperidin-4-ones as curcumin-inspired antineoplastics

A series of eleven N-acryloyl/N-cinnamoyl 3,5-bis(pyridin-4-yl)methylene-4-piperidones were synthesized as curcumin-based candidate antineoplastic agents. The cytostatic potency of these compounds was evaluated against three representative cell lines and all compounds were found to exhibit significant anti-cancer cell activity in vitro. QSAR studies using several physicochemical parameters and 50% inhibitory concentration (IC50) values resulted in certain important correlations which will aid design of more potent analogs. Representative test compounds were investigated in the NCI 60-cell line panel where they were found to display a profound cytotoxicity. These compounds were also potent anti-oxidants and inhibitors of human topoisomerase IIα. Representative compounds were well-tolerated by human fibroblasts and by mice during the survival/toxicity studies.

Electronic structure, novel synthesis, and O-H...O and C-H...O interactions in two 6-oxopiperidine-2-carboxylic acid derivatives

Molecules of (S)-6-oxo-1-(thiophen-2-ylmethyl)piperidine-2-carboxylic acid, C11H13NO3S, crystallize as single enantiomers in the space group P21 and the thiophene ring is disordered over two positions, while (S)-6-oxo-1-(thiophen-3-ylmethyl)piperidine-2-carboxylic acid, C11H13NO3S, crystallizes as a single enantiomer in the space group P212121. Their absolute configurations were confirmed by anomalous dispersion effects in diffraction measurements on the crystals. The molecules of each compound are linked by a combination of strong O-H...O hydrogen bonds and weak C-H...O interactions, resulting in two- and three-dimensional networks, respectively, in the crystal structures.

Identification of T. gondii myosin light chain-1 as a direct target of TachypleginA-2, a small-molecule inhibitor of parasite motility and invasion

Motility of the protozoan parasite Toxoplasma gondii plays an important role in the parasite’s life cycle and virulence within animal and human hosts. Motility is driven by a myosin motor complex that is highly conserved across the Phylum Apicomplexa. Two key components of this complex are the class XIV unconventional myosin, TgMyoA, and its associated light chain, TgMLC1. We previously showed that treatment of parasites with a small-molecule inhibitor of T. gondii invasion and motility, tachypleginA, induces an electrophoretic mobility shift of TgMLC1 that is associated with decreased myosin motor activity. However, the direct target(s) of tachypleginA and the molecular basis of the compound-induced TgMLC1 modification were unknown. We show here by “click” chemistry labelling that TgMLC1 is a direct and covalent target of an alkyne-derivatized analogue of tachypleginA. We also show that this analogue can covalently bind to model thiol substrates. The electrophoretic mobility shift induced by another structural analogue, tachypleginA-2, was associated with the formation of a 225.118 Da adduct on S57 and/or C58, and treatment with deuterated tachypleginA-2 confirmed that the adduct was derived from the compound itself. Recombinant TgMLC1 containing a C58S mutation (but not S57A) was refractory to click labelling and no longer exhibited a mobility shift in response to compound treatment, identifying C58 as the site of compound binding on TgMLC1. Finally, a knock-in parasite line expressing the C58S mutation showed decreased sensitivity to compound treatment in a quantitative 3D motility assay. These data strongly support a model in which tachypleginA and its analogues inhibit the motility of T. gondii by binding directly and covalently to C58 of TgMLC1, thereby causing a decrease in the activity of the parasite’s myosin motor.

Oridonin ring A-based diverse constructions of enone functionality: identification of novel dienone analogues effective for highly aggressive breast cancer by inducing apoptosis

Oridonin (1) has attracted considerable attention in recent years because of its unique and safe anticancer pharmacological profile. Nevertheless, it exhibits moderate to poor effects against highly aggressive cancers including triple-negative and drug-resistant breast cancer cells. Herein, we report the rational design and synthesis of novel dienone derivatives with an additional α,β-unsaturated ketone system diversely installed in the A-ring based on this class of natural scaffold that features dense functionalities and stereochemistry-rich frameworks. Efficient and regioselective enone construction strategies have been established. Meanwhile, a unique 3,7-rearrangement reaction was identified to furnish an unprecedented dienone scaffold. Intriguingly, these new analogues have been demonstrated to significantly induce apoptosis and inhibit colony formation with superior antitumor effects against aggressive and drug-resistant breast cancer cells in vitro and in vivo while also exhibiting comparable or lower toxicity to normal human mammary epithelial cells in comparison with 1.

Antifungal activity of fused Mannich ketones triggers an oxidative stress response and is Cap1-dependent in Candida albicans

We investigated the antifungal activity of fused Mannich ketone (FMK) congeners and two of their aminoalcohol derivatives. In particular, FMKs with five-membered saturated rings were shown to have minimum inhibitory concentration (MIC90s) ranging from 0.8 to 6 µg/mL toward C. albicans and the closely related C. parapsilosis and C. krusei while having reduced efficacy toward C. glabrata and almost no efficacy against Aspergillus sp. Transcript profiling of C. albicans cells exposed for 30 or 60 min to 2-(morpholinomethyl)-1-indanone, a representative FMK with a five-membered saturated ring, revealed a transcriptional response typical of oxidative stress and similar to that of a C. albicans Cap1 transcriptional activator. Consistently, C. albicans lacking the CAP1 gene was hypersensitive to this FMK, while C. albicans strains overexpressing CAP1 had decreased sensitivity to 2-(morpholinomethyl)-1-indanone. Quantitative structure-activity relationship studies revealed a correlation of antifungal potency and the energy of the lowest unoccupied molecular orbital of FMKs and unsaturated Mannich ketones thereby implicating redox cycling-mediated oxidative stress as a mechanism of action. This conclusion was further supported by the loss of antifungal activity upon conversion of representative FMKs to aminoalcohols that were unable to participate in redox cycles.

Mitochondrial dysfunction contributes to the cytotoxicity of some 3,5-bis(benzylidene)-4-piperidone derivatives in colon HCT-116 cells

The objectives of this study are to investigate the possible ways by which the curcumin analogs 2a and 2b exert their antiproliferative properties. The analogs 2a and 2b have submicromolar IC(50) values towards human HCT-116 colon cancer cells but are far less toxic to human non-malignant CRL-1790 colon cells. Both compounds affected a number of mitochondrial functions in HCT-116 cells namely increasing the intracellular concentrations of reactive oxygen species, inhibiting oxygen consumption and decreasing the mitochondrial membrane potential. These molecules also produced swelling of isolated rat liver mitochondria, supporting a mitochondrial mechanism of cytotoxicity. Both compounds reacted with glutathione in the presence of glutathione S-transferase π and hence they may be classified as thiol alkylators.

Bis[3,5-bis(benzylidene)-4-oxo-1-piperidinyl]amides: a novel class of potent cytotoxins

The principal objective of this study was the examination of the theory of cytotoxic synergism. In this exploratory study, we tested the hypothesis that doubling the number of sites available for thiol alkylation in a series of candidate cytotoxins increases potency more than two-fold. This concept was verified in one-third of our comparisons using human Molt 4/C8 and CEM T-lymphocytes and murine L1210 cells. In addition, the significant potencies of various members of our compound series justified further studies. Molecular modeling revealed that relative locations of the amidic groups correlate with cytotoxicity. A potent cytotoxic compound, 1,2-bis(3,5-dibenzylidene-4-oxo-piperidin-1-yl)ethane-1,2-dione (1a) inhibited the growth of a large number of human tumor cell lines and displayed greater toxicity toward certain non-adherent cells than toward adherent neoplasms or fibroblasts. The mode of action of 1a includes induction of apoptosis and necrosis.

3,5-Bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones: a novel cluster of potent tumor-selective cytotoxins

Novel 3,5-bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones (3a-e) display potent cytotoxicity and a preferential lethality toward various neoplasms compared to some normal cells. The corresponding sulfonic acid analogues 5a-e and an isostere 4 demonstrated substantially lower activity. The leads 3d and 3e possess very high activity against colon cancer and leukemia cell lines, caused DNA fragmentation, and activated caspase-3 in HL-60 cells. The enones 3b-e were well tolerated in a short-term toxicity screen in mice.

Sequential cytotoxicity: a theory examined using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines and related phosphonic acids

The concept of sequential cytotoxicity, which states that successive chemical attacks on cellular constituents can be more deleterious to neoplasms than normal cells, was evaluated using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines 1 and related phosphonic acids 2, which were screened against a panel of malignant and normal cell lines. The compounds proved to be not only potent cytotoxins (71% of the CC(50) figures are submicromolar) but to display greater cytotoxicity to the neoplastic cells. QSAR revealed that both cytotoxic potencies and selective toxicity were increased by a rise in the electron-withdrawing properties and a decrease in the hydrophobicity of the aryl substituents. Utilisation of the PL10 concept and evaluation of druglike properties revealed 1c as the lead tumour-specific cytotoxin. This molecule activated caspase-3 in HL-60 cells but not in the HSC-2 cell line. While 1c caused internucleosomal DNA fragmentation in HL-60 cells, it did not elicit this effect in either HSC-2 and HSC-4 cells. Clearly 1c exerts its cytotoxic potencies by different mechanisms and such pleiotropy is likely the principal reason for the remarkable display of preferential toxicity towards malignant cells of the compounds in series 1 and 2.

Symmetrical alpha-bromoacryloylamido diaryldienone derivatives as a novel series of antiproliferative agents. Design, synthesis and biological evaluation

In a continuing study of hybrid compounds containing the alpha-bromoacryloyl moiety as potential anticancer drugs, we synthesized a novel series of hybrids 4a-h, in which this moiety was linked to a 1,5-diaryl-1,4-pentadien-3-one system. Many of the conjugates prepared (4b, 4c, 4e and 4g) demonstrated pronounced, submicromolar antiproliferative activity against four cancer cell lines. Moreover, compound 4b induced apoptosis through the mitochondrial pathway and activated caspase-3 in a concentration-dependent manner.

Derivatives of aryl amines containing the cytotoxic 1,4-dioxo-2-butenyl pharmacophore

Several series of compounds containing the 1,4-dioxo-2-butenyl moiety have been prepared as candidate cytotoxins, including the methyl N-arylmaleamates, methyl N-arylfumaramates, and N-arylmaleimides. In addition, the N-arylisomaleimides were synthesized which are the structural isomers of N-arylmaleimides. These compounds were evaluated against human Molt 4/C8 and CEM T-lymphocytes as well as murine L1210 cells. Methyl N-arylfumaramates showed the highest cytotoxic potencies and, in particular, methyl N-(3,4-dichlorophenyl)fumaramate is six times more potent than melphalan towards L1210 cells and is equipotent with this drug in the Molt 4/C8 assay. Electrophilicity of compounds under investigation was demonstrated by carrying out thiolation using model benzyl mercaptan on representative compounds. Methyl N-(3,4-dichlorophenyl)fumaramate and methyl N-(4-chlorophenyl)maleamate inhibited human N-myristoyltransferase, a possible molecular target, in high micromolar range. QSAR and molecular modeling revealed some correlations between different structural features of a number of the molecules and cytotoxic potencies. Methyl N-arylfumaramates were well tolerated in mice in comparison to the analogs in other series of compounds tested. The data obtained in this investigation affords guidelines for preparing new series of molecules with greater potencies.

3,5-Bis(benzylidene)-1-[4-2-(morpholin-4-yl)ethoxyphenylcarbonyl]-4-piperidone hydrochloride: a lead tumor-specific cytotoxin which induces apoptosis and autophagy

A number of N-4-(2-aminoethoxy)phenylcarbonyl derivatives of various 3,5-bis(benzylidene)-4-piperidones 2-5 demonstrated noteworthy cytotoxic potencies towards human HL-60 leukemic cells as well as human HSC-2 and HSC-4 squamous cell carcinomas. In general, toxicity towards HGF, HPC, and HPLF normal cells was substantially lower. The highest selective toxicity was noted when the terminal base is morpholine. Lead optimization was based on finding compounds which had (i) high cytotoxic potencies, (ii) a greater toxicity to neoplasms than normal cells, and (iii) drug-likeness based on the rule of five. From the biodata generated, 5a evolved as a promising lead compound for further development. The mode of action of 5a included the induction of apoptosis in HL-60 cells in which internucleosomal DNA fragmentation and activation of caspase-3 was noted. In addition, 5a caused autophagy in HSC-2 cells.

r-2,c-6-Bis(4-methoxy-phenyl)-c-3,t-3-dimethyl-1-nitro-sopiperidin-4-one

In the title compound, C₂₁H₂₄N₂O₄, the piperidine ring adopts a distorted boat conformation. The crystal structure is stabilized by C—H⋯π inter­actions involving one of the methoxy­phenyl rings.

13-Hydroxy-4,16-dimethyl-4,16-diazapentacyclo[12.3.1.01,5.05,13.07,12]octadeca-7(12),8,10-triene-6,18-dione

In the title compound, C₁₈H₂₀N₂O₃, the N-methyl­piperidone ring adopts a chair conformation. The pyrrolidine ring and the five-membered cyclo­pentane rings adopt envelope conformations. The five-membered ring of the ninhydrin system adopts an envelope conformation with the central C atom deviating by 0.217 (1)Å from the mean plane through the other atoms. The mol­ecular packing is characterized by inter­molecular C—H⋯O and intra­molecular C—H⋯O and O—H⋯N inter­actions.

1,5-diaryl-3-oxo-1,4-pentadienes: a case for antineoplastics with multiple targets

A number of organic molecules which contain the 1,5-diaryl-3-oxo-1,4-pentadienyl group, referred to hereafter as the dienone moiety, have antineoplastic properties. Emphasis is made on the attachment of this structural moiety to several molecular scaffolds, namely piperidines, N-acylpiperidines, cycloalkanes and 3,4-dihydro-1H-napthalenes. Many of these compounds are potent cytotoxins having micromolar and nanomolar IC(50) values towards a wide range of neoplastic and transformed cells. On occasions, greater toxicity towards neoplasms than normal cells has been demonstrated. A number of these compounds have in vivo anticancer properties and in general excellent tolerability in rodents is demonstrated. The way in which a number of physicochemical properties such as redox potentials, torsion angles, atomic charges and logP values govern cytotoxic potencies are presented. The importance of the shapes of different compounds as determined by molecular modeling in contributing to antineoplastic properties is outlined. Arguments are presented in favour of designing antineoplastics which have multiple sites of action in contrast to those bioactive molecules which have only one molecular target. A number of compounds which possess the dienone group have different modes of action some of which are chronicled in this review, such as inducing apoptosis, affecting respiration in mitochondria, inhibiting macromolecular biosynthesis and both inhibiting and stimulating certain enzymes. Other important properties of these compounds are discussed including their anti-angiogenic, MDR-revertant and antioxidant properties. It is hoped that this eulogy of the importance of the dienone group will encourage researchers to consider incorporating this structural unit into candidate cytotoxins in the future.

The cytotoxic properties and preferential toxicity to tumour cells displayed by some 2,4-bis(benzylidene)-8-methyl-8-azabicyclo[3.2.1] octan-3-ones and 3,5-bis(benzylidene)-1-methyl-4-piperidones

This study demonstrated that replacement of the axial protons on the C2 and C6 atoms of various 1-methyl-3,5-bis(benzylidene)-4-piperidones 3 by a dimethylene bridge leading to series 2 lowered cytotoxic potencies. Four compounds 2a and 3a-c emerged as lead molecules based on their toxicity towards different neoplasms and their selective toxicity for malignant rather than normal cells. Some possible reasons for the disparity between the IC(50) values in the two series of compounds are presented based on molecular modeling, logP values and respiration in rat liver mitochondria.

r-2,c-6-Bis(4-methoxy-phen-yl)-c-3,t-3-dimethyl-piperidin-4-one

The asymmetric unit of the title compound, C₂₁H₂₅NO₃, contains two crystallographically independent mol­ecules (A and B). In both mol­ecules, the piperidine ring adopts a chair conformation, with the methoxy­phenyl rings attached equatorially. The dihedral angle between the two benzene rings in mol­ecule A is 73.79 (8)°; the corresponding value in mol­ecule B is 77.71 (8)°. The mol­ecules are linked by N—H⋯O hydrogen bonds. In addition, C—H⋯π inter­actions are also found in the crystal structure.

Molecular modifications of 2-arylidene-1-indanones leading to increased cytotoxic potencies

A series of 2-arylidene-1-indanones, 1, had been shown previously to display cytotoxic properties towards Molt 4/C8, CEM and L1210 cells. In the present study, two series of analogues of 1 were prepared namely various 2-arylidene-1,3-indandiones, 2, and chalcones, 3. In general, the potencies of compounds 2 and 3 were greater than the analogues bearing the same aryl substituents in series 1. Molecular modeling was undertaken in order to seek explanations for the variation in bioactivities.

3,5-Bis(Phenylmethylene)-1-(N-arylmaleamoyl)-4-piperidones: A Novel Group of Cytotoxic Agents

A series of novel 3,5-bis(phenylmethylene)-1-(N-arylmaleamoyl)-4-piperidones 3 have been synthesized which displayed potent cytotoxicity towards human Molt 4/C8 and CEM T-lymphocytes as well as murine P388 and L1210 leukemic cells. In contrast, the related N-arylmaleamic acids 4 possessed little or no cytotoxicity in these four screens. Molecular modeling revealed certain interplanar and bond angles and interatomic distances which were perceived to contribute to the observed bioactivity as well as providing suggestions for future structural modifications of the piperidones 3. Evaluation of representative compounds in series 3 and 4 on the activity of human N-myristoyltransferase revealed that, at the maximum concentration utilized, namely 250 microM, only weak inhibiting properties were displayed by some of the compounds in series 4. Various members of series 3 and 4 were well tolerated in mice.

Cytotoxic and Topographical Properties of 6-Arylidene-2-dimethylaminomethylcyclohexanone Hydrochlorides and Related Compounds

A number of 2-arylidenecyclohexanones (1a-h) were converted into the corresponding Mannich bases (2a-h) and (3a,f). Evaluation against murine L1210 cells as well as human Molt 4/C8 and CEM T-lymphocytes revealed the marked cytotoxicity of the Mannich bases and also the fact that almost invariably these compounds were more potent than the precursor enones (1a-h). Further evaluation of most of the Mannich bases towards a panel of nearly 60 human tumour cell lines confirmed their utility as potent cytotoxins. In this assay, the compounds showed growth-inhibiting properties greater than the anticancer alkylator melphalan. QSAR studies revealed that in some cell lines compounds possessing small electron-attracting aryl substituents showed the greatest potencies. Molecular modeling and X-ray crystallography demonstrated that various interatomic distances and torsion angles correlated with cytotoxicity. A representative compound (2a) demonstrated weak inhibiting properties towards human N-myristoyltransferase and stimulated a tyrosine protein kinase. A single dose of 100 mg/kg of most of the compounds did not prove to be lethal in mice.

1-Bromo-acetyl-2,6-bis-(4-methoxy-phen-yl)-3,5-dimethyl-piperidin-4-one

In the title compound, C(23)H(26)BrNO(4), the piperidinone ring adopts a boat conformation. The dihedral angle between the two benzene rings is 70.9 (1)°. The two meth-oxy groups are close to coplanar with the attached benzene rings [C-C-O-C torsion angles of 6.3 (5) and 16.4 (4)°]. A weak C-H⋯Br intra-molecular inter-action is observed. In the crystal structure, mol-ecules are linked into a chain along [101] by inter-molecular C-H⋯O hydrogen bonds. A short inter-molecular Br⋯O contact [3.063 (2) Å] is observed.