Isoxazolyl-urea derivative evokes apoptosis and paraptosis by abrogating the Wnt/β-catenin axis in colon cancer cells.

Deregulated activation of the Wnt/β-catenin pathway is observed in many types of human malignancies including colon cancer. Abrogation of the Wnt/β-catenin pathway has been demonstrated as an effective way of inducing cancer cell death. Herein, a new isoxazolyl-urea (QR-5) was synthesized and examined its efficacy on the viability of colon cancer cell lines. QR-5 displayed selective cytotoxicity towards colon cancer cells over normal counterparts. QR-5 induced apoptosis as evidenced by elevation in sub-G1 cells, decrease in Bcl-2, MMP-9, COX-2, VEGF and cleavage of PARP and caspase-3. QR-5 reduced the mitochondrial membrane potential, decreased the expression of Alix and elevated the expression of ATF4 and CHOP indicating the induction of paraptosis. The inhibitor of apoptosis (Z-DEVD-FMK) and paraptosis (CHX) could not restore Alix expression and PARP cleavage in QR-5 treated cells, respectively suggesting the complementation between the two cell death pathways. QR-5 suppressed the expression of Wnt/β-catenin pathway proteins which was also evidenced by the downregulation of nuclear and cytoplasmic β-catenin. The dependency of QR-5 on β-catenin for inducing apoptosis and paraptosis was demonstrated by knockdown experiments using β-catenin specific siRNA. Overall, QR-5 induces apoptosis as well as paraptosis by mitigating the Wnt/β-catenin axis in colon cancer cells.