QS210 - Chemoprevention in Familial Adenomatous Polyposis: Dual Therapy Creates Enhanced Synergy in Patient-Derived 3D Organoid Models

Purpose/Background: Familial Adenomatous Polyposis (FAP) patients are guaranteed to develop colorectal cancer (CRC) without intervention and there are no effective means to slow polyp progression. Although some chemotherapeutic agents have been trialed, none have been particularly effective. FAP is caused by an inherited pathogenic variant in the WNT pathway regulator APC. Therefore, we hypothesized that directly targeting WNT pathways using multiple agents could produce more effective anti-neoplastic effects. We studied this in a patient-derived adenoma organoid model.

Methods/Interventions: Adenomatous polyps were obtained from FAP patients during colonoscopy or surgery. To establish patient-specific organoid lines, adenoma tissues were dissociated and resuspended in Matrigel beads then cultivated using organoid media containing a mixture of L-WRN conditioned media and Advanced DMEM/F12 supplemented with 20% FBS, glutamine, penicillin-streptomycin, ROCK inh, and TGFb inh. Established organoids were treated with WNT inhibitors pyrvinium and niclosamide individually and as dual therapy, and subsequently tested for viability. Synergy scores were calculated using the Loewe Additivity Model.

Results/Outcomes: Five FAP patient-derived adenoma organoid lines were tested for viability after treatment with each of the 2 drugs individually. All lines exhibited a dose dependent decrease in viability 72 hours after treatment with increasing doses of either niclosamide or pyrvinium. There was variability in response, with IC50 ranging from 12 to 185 nmol/L for pyrvinium and 2.4-7.5 μmol/L for niclosamide. To test the effect of dual therapy, 2 lines were treated with combination therapy. Synergistic maps demonstrated different but consistent synergy (more than the additive effect of each drug alone) after dual treatment (Figure 1). The highest synergistic effect between the drugs for the organoid line #1 was noted at concentrations of 50 nmol/L for pyrvinium and 2.5 μmol/L for niclosamide. For organoid line #2, the largest synergistic effect was achieved with 100 nmol/L of pyrvinium and 2.5 μmol/L of niclosamide.

Conclusion/Discussion: We have established an FAP organoid model to test chemopreventative strategies and discovered that dual therapy using WNT pathway inhibitors produced synergistic effects. Differences between the patient derived lines suggest the need for individualized chemopreventative regimens. This work should be expanded with more patients but presents the proof of concept for potential clinical evaluation.