Discovery of Anticancer Indole-Based 4,5-Dihydroisoxazole Derivative with Selectivity toward Leukemia Cells

Isoxazole-derived compounds possess various bioactivities including anticancer, immunomodulatory, antimicrobial, anti-inflammatory, or antipsychotic effects with successful implementation in clinical practice. Treatment of hematological malignancies with isoxazole derivatives represents a promising area of research. The present study aimed to synthesize 11 novel 3,5-diaryl-4,5-dihydroisoxazole compounds and assess their antiproliferative effects using cell viability assay in a panel of nine cancer types including breast (MCF-7), colon (HCT-116), cervical (HeLa), lung (A549), ovarian cancer (A2780), glioblastoma (U87), hepatocellular carcinoma (HepG2), and leukemia (Jurkat and HL-60) cells as well as two noncancerous cell lines (Bj-5ta and MCF-10A). The most promising compound was further screened using flow cytometry, Western blot, fluorescence microscopy, and chemotaxis/migration cell assays. Compound (±)-3-[3-(4-bromophenyl)-4,5-dihydro-1,2-oxazol-5-yl]-1-methyl-1H-indole (4a, DHI1) showed the most promising potential due to its high selectivity toward leukemia Jurkat and HL-60 cells while having at the same time minimal toxicity to noncancerous cells as well as healthy human peripheral blood mononuclear cells. For the first time, DHI1 was shown to inhibit the migration and invasiveness of Jurkat and HL-60 cells via disruption of cytoskeletal actin filaments coupled to G2/M cell cycle arrest in Jurkat and HL-60 cells and S phase arrest in HL-60 cells. Treatment with DHI1 affected signaling proteins associated with the cell cycle, including p21, Cyclin B1, Cdc2, Wee1, Rb, and Chk1. The binding interaction between DHI1 and BSA revealed that the Stern–Volmer constant (K_sv) for BSA fluorescence quenching increases with temperature, rising from 8.06 × 10⁴ to 11.09 × 10⁴ M^–1. Herein, the novel synthesized indolyl dihydroisoxazole derivative DHI1 possesses promising therapeutic potential and superior safety profile due to its high selectivity toward Jurkat and HL-60 leukemia cells and low toxicity to noncancerous cells.