Inhibitory effects of c-MYC degrading rLON protease on intestinal polyps in PIRC rat, a familial adenomatous polyposis model

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide, accounting for approximately 10% of all cases, and is the second leading cause of cancer-related deaths in the United States. In patients with Familial Adenomatous Polyposis (FAP), APC mutations drive c-MYC overexpression, promoting metabolic and immune dysregulation that contributes to CRC development, making c-MYC a potential target for FAP-associated chemoprevention. Although no c-MYC inhibitors are currently available, recent evidence indicates that a uropathogenic E. coli protease can degrade c-MYC protein. This study evaluated recombinant LON protease (rLONP) for chemopreventive efficacy in PIRC rats, a model of FAP. Rat pups were genotyped, baseline polyp burden was established by colonoscopy, and animals were randomized to receive saline or rLONP twice daily (2.5 mg/kg, p.o.) for 2 or 4 weeks. Serum analyses showed no significant changes in liver or kidney function markers in rLONP-treated rats compared with controls. rLONP-treated male rats exhibited a ∼40% reduction in colonic polyps at both time points, and small intestinal polyp counts were also lower in treated males and females. Combined analysis demonstrated a ≥60% reduction in total intestinal polyp multiplicity after 2-4 weeks of treatment (p<0.001). Protein expression analyses of colonic polyps revealed decreased c-MYC protein levels following rLONP treatment. Immunohistochemistry further showed reduced Ki-67, Cyclin D1, and c-MYC expression in treated polyps compared with controls. Overall, rLONP was well tolerated and significantly reduced intestinal polyp burden in PIRC rats in this short-term study, supporting further long-term efficacy evaluation.