Natural-Origin Compounds as Future Precision Partners in Combination Cancer Therapy

Cancer multidrug resistance (MDR), particularly mediated by ATP-binding cassette (ABC) transporters, can link ABC transporters' ATP-dependent efflux to Nrf2-driven antioxidant defence. This connection reduces the oxidative threshold in MDR cancer cells. Natural or nature-inspired compounds can target this vulnerability and induce collateral sensitivity (CS) by simultaneously modulating the redox balance and ABC transporters' activity in MDR cancer cells. Moreover, natural-origin compounds can act on multiple targets by combining efflux inhibition, redox modulation, and immune evasion into a unique therapeutic strategy. However, many challenges should be addressed in their characterisation and preclinical validation to ensure their usefulness for clinical application. These include poor bioavailability, pharmacokinetic interactions, safe toxicity windows, and tumour heterogeneity. In perspective, adaptive trial designs employing biomarker-guided patient stratification can translate natural-origin compounds from preclinical promise to precision partners in clinical oncology.