The Tyro3 Inhibitor UNC9426 Induces Apoptosis in OEC-M1 OSCC Cells

BACKGROUND/AIM: Elevated Tyro3 expression has been associated with tumor cell survival and malignant progression, suggesting that Tyro3 may represent a therapeutic target in oral squamous cell carcinoma (OSCC). We evaluated the effects of the selective Tyro3 inhibitor UNC9426 in OEC-M1 OSCC cells and associated apoptosis-related signaling changes. MATERIALS AND METHODS: OEC-M1 cells and non-malignant HGF-1 gingival fibroblasts were used. Cell viability, apoptotic morphology, protein expression, caspase-cleaved cytokeratin-18 fragment release, and JC-1 fluorescence were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, light microscopy, immunoblotting, enzyme-linked immunosorbent assay, and JC-1 staining, respectively. Z-VAD-FMK, the Fas-blocking antibody ZB4, and BAX activation inhibitor 1 (BAI1) were used to examine caspase, Fas, and BAX involvement. RESULTS: . 3.987 μM). UNC9426 increased membrane blebbing, poly(ADP-ribose) polymerase cleavage, caspase-cleaved cytokeratin-18 fragment release, and cleavage of caspase-8, -9, -3, and -7. Qualitative JC-1 imaging showed an apparent increase in monomer-associated green fluorescence consistent with changes associated with mitochondrial membrane depolarization. Z-VAD-FMK attenuated UNC9426-induced cytokeratin-18 fragment release. UNC9426 reduced Tyro3 protein abundance and Akt and extracellular signal-regulated kinase (ERK) phosphorylation after 24 h and increased Fas and BAX protein levels after 48 h. ZB4 or BAI1 partially reversed the reduction in cell viability and attenuated cytokeratin-18 fragment release. CONCLUSION: UNC9426 induces apoptosis in OEC-M1 cells in association with reduced Tyro3 protein abundance and Akt/ERK phosphorylation, with Fas signaling and BAX activity contributing functionally to the apoptotic response.