PGP and breast carcinoma: Another encouraging study confirming the potential of nanoparticles as therapeutic methods is the research carried out by Shi X et al. They found that novel redox-responsive, chondroitin sulfate-based nanoparticles might improve the chemo-photodynamic therapy of breast cancer due to the down-regulation of the p-gp on MCF-7/ADR cells and thereby improve the anticancer efficacy of PTX against MCF-7/ADR cells.