Synthesis and Biological Evaluation of Novel N-phenyl-5-carboxamidyl Isoxazoles as Potential Chemotherapeutic Agents for Colon Cancer

Abstract

A new series of isoxazole derivatives, <i>N</i>-phenyl-5-carboxamidyl isoxazoles, was investigated for their anticancer activity with solid tumor selectivity. Six <i>N</i>-phenyl-5-carboxamidylisoxazoles were chemically synthesized and evaluated by the <i>in vitro</i> disk-diffusion assay and IC₅₀ cytotoxicity determination. The results showed that one of the derivatives, compound <b>3,</b><i>N</i>-(4-chlorophenyl)-5-carboxamidyl isoxazole, was the most active against colon 38 and CT-26 mouse colon tumor cells with an IC₅₀ of 2.5 μg/mL for both cell lines. Western blot analysis showed that compound <b>3</b> significantly down-regulated the expression of phosphorylated STAT3 in both human and mouse colon cancer cells indicating that the mechanism of action for compound <b>3</b> may involve the inhibition of JAK3/STAT3 signaling pathways. Flow cytometric analysis with Annexin V staining showed that the death induced by compound <b>3</b> is mediated through cell necrosis and not apoptotic pathway. In summary, our results show that compound <b>3</b> is a new <i>N</i>-phenyl-5-carboxamidyl isoxazole with potential anticancer activity. Compound <b>3</b> inhibits the phosphorylation of STAT3, a novel target for chemotherapeutic drugs, and is worthy of further investigation as a potential chemotherapeutic agent for treating colon cancer.