Does Mutated Oncogene Attenuate the Effect of Sulindac in Colon Cancer Chemoprevention?

The NSAID sulindac has been successfully used alone or in combination with other agents to suppress colon tumorigenesis in patients with genetic predisposition and also showed its efficacy in prevention of sporadic colon adenomas. At the same time, some experimental and clinical reports suggest that a mutant oncogene may negate sulindac antitumor efficacy. To directly assess sulindac activity at suppressing premalignant lesions carrying K-RAS mutation, we utilized a novel mouse model with an inducible colon-specific expression of the mutant oncogene ( ). Tumor development and treatment effects were monitored by minimally invasive endoscopic Optical coherence tomography. Expression of the mutant allele accelerated azoxymethane (AOM)-induced colon carcinogenesis in C57BL/6 mice, a strain otherwise resistant to this carcinogen. Sulindac completely prevented AOM-induced tumor formation in wild-type ( wt) animals. In -mutant mice, a 38% reduction in tumor number, an 83% reduction in tumor volume ( <= 0.01) and an increase in the number of adenoma-free mice ( = 0.04) were observed. The partial response of animals to sulindac treatment was evident by the decrease in mucosal thickness ( < 0.01) and delay in progression of the precancerous aberrant crypt foci to adenomas. Molecular analyses showed significant induction in cyclooxygenase 2 (COX-2), cleaved caspase-3 (CC3), and Ki-67 expression by AOM, but not sulindac treatment, in all genotypes. Our data underscore the importance of screening for mutations in individuals with colon polyps to provide more personalized interventions targeting mutant signaling pathways. .