PGP and cancer: Furthermore, similar to the experiments by Yamagishi et al. [8] in KBV1 cancer cells, transport experiments with Rho123 and a Pgp inhibitor in endolysosome-enriched liver fractions indicated that the endolysosomal Pgp is functionally active, pumping a Pgp substrate into the lumen of the organelles, as also indicated by confocal microscopy.