Although they do not constitute the only mechanism developed by cancer cells to eliminate drugs, it is one of the most studied ones, and now considered to be one the key target to overcome chemoresistance [71], either by inhibition or by evasion; many of the most widely-used chemotherapeutic agents (e.g., doxorubicin, etoposide, paclitaxel, etc.)are susceptible to P-gp-mediated efflux. The gene discussed is PGP; the disease is cancer.