In this study, we screened a chemical library to find potent anticancer compounds that are less cytotoxic to non-cancerous cells. This study revealed that pyrazole PTA-1 is a potent anticancer compound. Additionally, we sought to elucidate its mechanism of action (MOA) in triple-negative breast cancer cells. Cytotoxicity was analyzed with the differential nuclear staining assay (DNS). Additional secondary assays were performed to determine the MOA of the compound. The potential MOA of PTA-1 was assessed using whole RNA sequencing, Connectivity Map (CMap) analysis, in silico docking, confocal microscopy, and biochemical assays. PTA-1 is cytotoxic at a low micromolar range in 17 human cancer cell lines, demonstrating less cytotoxicity to non-cancerous human cells, indicating a favorable selective cytotoxicity index (SCI) for the killing of cancer cells. PTA-1 induced phosphatidylserine externalization, caspase-3/7 activation, and DNA fragmentation in triple-negative breast MDA-MB-231 cells, indicating that it induces apoptosis. Additionally, PTA-1 arrests cells in the S and G2/M phases. Furthermore, gene expression analysis revealed that PTA-1 altered the expression of 730 genes at 24 h (198 upregulated and 532 downregulated). A comparison of these gene signatures with those within CMap indicated a profile similar to that of tubulin inhibitors. Subsequent studies revealed that PTA-1 disrupts microtubule organization and inhibits tubulin polymerization. Our results suggest that PTA-1 is a potent drug with cytotoxicity to various cancer cells, induces apoptosis and cell cycle arrest, and inhibits tubulin polymerization, indicating that PTA-1 is an attractive drug for future clinical cancer treatment.

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.