P-gp inhibitory activity from marine sponges, tunicates and algae

The only effective therapy for metastasis in cancer patients is chemotherapy, which all too frequently fails due to innate or acquired multi-drug resistance (MDR). Historically, ATP binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), are recognized as the major culprits responsible for MDR. Over-expressing of P-gp in cancer cells, can lead to premature efflux of clinical chemotherapeutic agents and correlate with poor chemotherapeutic outcome and relapse of some cancers. The most likely strategy to overcome MDR is to search for inhibitors from natural products. With unique and novel chemical structures, marine-derived metabolites are an attractive new resource, to prime the search for new P-gp inhibitors. This chapter summarizes P-gp inhibitory activity in marine natural products (MNPs) and validates that MNPs can deliver new ABC transporter inhibitor scaffolds