PGP and neoplasm: While it is well known that ABC transporters expressed on plasma membrane facilitate the efflux of many anticancer drugs from tumor cells, resulting in MDR, the inward facing lysosomal P-gp-MDR1 therefore can sequester its substrates in the lysosomes and prevent the cytotoxic payloads from reaching their intracellular targets such as nucleus and microtubules (Yamagishi et al., 2013).