Abstract 2373: Colonic polyp preventive effect of rLON protease in FAP-rat intestinal polyposis model

Abstract Hereditary Familial Adenomatous Polyposis (FAP) patients develop large number of colonic polyps that can progress to aggressive carcinomas. In the FAP patients, Apc or β-catenin mutations lead to c-Myc overexpression, which in turn drives the metabolic and immune alterations leading to colorectal cancer, making it a potential target for CRC prevention. Unfortunately, finding c-Myc inhibitors has been difficult and only recently studies show that uropathogenic E. Coli rLON protease (rLONP) can degrade the c-Myc in tumor tissues. In this study, PIRC rats (10- or 12- weeks age) were treated with rLONP (0.375mg/rat/day dose) in PBS by oral gavage twice daily for either 2- or 4- weeks and assessed for toxicity and intestinal tumor burden. Organ morphology and weight were not significantly different from control PIRC rats. Also, hematological profile was very similar in control and rLONP treated male rats, however in female PIRC rats, rLONP treatment for 4 weeks showed significant differences in WBC, neutrophils, and lymphocytes count compared to control. Serum analysis indicated a non-significant (p>0.05) increase in AST (297.6±74.3 u/L) and ALT (365.3±86.8 u/L) levels with 4-weeks rLONP treatment when compared to control group (133.9±27.5 u/L & 184.5±30.3 u/L respectively). ALKP levels were slightly lower (187.6±14.4 u/L) in rLONP treated rats compared to control (221.3±16.7 u/L). BUN (17.6±0.7 mg/dL) and CREA (0.15±0.03 mg/dL) of the rLONP treated rats were non-significantly different from control group (16.6±1.1 mg/dL & 0.15±0.02 mg/dL respectively). Histopathology of all major organs of rLONP treatment appeared normal, with no significant differences as compared to untreated groups. Colonic and small intestinal polyps were compared between control and rLONP treated rats. Average colonic polyps were less in rLONP treated male rats at both 2- and 4- week endpoints (40% reduction) compared to their respective control rats while this effect was not distinguishable in the females due to low polyp number and slow rate of polyp and tumor development. Small intestinal polyps also appeared to be less in number in rLONP treated male and female rats as compared to control. Total intestinal polyps showed ≥50% reduction of multiplicity, male (p<0.012; p<0.009) and female (p=0.06; p<0.022) with 2- and 4- week rLONP treatment, respectively, as compared to control group. Protein expression analysis of control and treated colonic polyp tissues suggested reduction of c-MYC expression with rLONP treatment. Also, IHC analysis showed reduction in Ki-67, Cyclin D1, and c-Myc expression in the rLONP treated rat colonic polyps when compared with control polyps. Based on these observations, it is concluded that rLONP treatment did not cause any overt-toxicities and reduced intestinal polyps in PIRC rats in a short-term study. (Project funded in whole with Federal funds from the NCI, NIH, DHHS, under Contract 75N91019D00020_75N91022F00001). Citation Format: Venkateshwar Madka, Karthikkumar Venkatachalam, Gopal Pathuri, Nicole Stratton, Anil Singh, Shizuko Sei, Mark S. Miller, Vignesh Gunasekharan, Chinthalapally V. Rao. Colonic polyp preventive effect of rLON protease in FAP-rat intestinal polyposis model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2373.