PGP and cancer: Singh et al. reported that treatment with nanoformulation containing doxorubicin-loaded cationic surfactant-based nanoparticles with P-gp inhibitor encapsulated within it results in sensitization of DOX-resistant ovarian cancer cells, which was determined by interaction of positively charged nanoparticles with negatively charged cell cancer surface and simultaneous caveolae-dependent endocytosis of nanosystem [138].