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-1<i>H</i>-indole (<b>4a, DHI1</b>) 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, <b>DHI1</b> 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 <b>DHI1</b> affected signaling proteins associated with the cell cycle, including p21, Cyclin B1, Cdc2, Wee1, Rb, and Chk1. The binding interaction between <b>DHI1</b> and BSA revealed that the Stern-Volmer constant (<i>K</i> _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 <b>DHI1</b> 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.