Lead Validation of the Olive Phenolic S-(−)-Oleocanthal for Effective Control of KRASG13D-Mutant Colorectal Cancer Progression and Metastasis

Background/Objectives: Colorectal cancer (CRC) is the second most common cancer-causing death in the United States. The Mediterranean diet, rich in extra-virgin olive oil (EVOO), is associated with a lower risk of colorectal cancer (CRC). Earlier studies reported S-(−)-oleocanthal (OC), the major EVOO phenolic, to be effective in CRC progression and recurrence suppression in a subcutaneous xenograft model by targeting the SMYD2–EZH2/c-MET signaling axis and favorably modulating gut microbiota (GM). However, lead validation in an orthotopically xenografted model that mimics the tumor microenvironment is yet to be achieved. The GM contribution to OC anti-CRC activity remains unknown. Methods: We used an orthotopic intra-cecally xenografted nude mouse model to validate OC anti-KRAS-mutant CRC activity and assessed the contribution of OC GM modulation to this activity using an oral antibiotic depletion strategy. Results: Daily oral 10 mg/kg OC impressively suppressed KRASG13D-mutant CRC HCT-116-Luc progression and metastasis more effectively than intraperitoneal administration 3×/week. By contrast, GM depletion with a broad-spectrum antibiotics cocktail (ABC) partially attenuated this activity, suggesting GM contribution to OC anti-CRC activity. Thus, fecal microbiota transplantation (FMT) was conducted using fresh daily oral fecal GM treatments collected from 20 mg/kg OC-dosed nude mouse donors. A week before FMT dosing, orthotopic HCT-116-Luc tumor-bearing recipient mice were subjected to GM depletion using daily oral ABC dosing. Recipient mice treated with FMT from OC-treated donors exhibited dramatic >99% reductions in primary and near-complete suppression of multi-organ metastatic tumor burden versus FMT controls. Conclusions: Collectively, oral OC is validated as an effective anti-KRASG13D-mutant CRC lead. Future clinical trials can validate its anti-CRC potential in a human model.