PGP and breast cancer: Furthermore, immunofluorescence study showed that P-gp is also localized in lysosome after transient expression of human P-gp-GFP in HeLa cells or in the human breast cancer MCF-7 cells, which are stably expressed with P-gp-GFP, suggesting P-gp can be moved to the lysosomal degradation compartment, presumably through the early and late endosome (12).