P-gp transports neutral or cationic hydrophobic and unmodified compounds, and it is involved in the resistance of several important chemotherapy agents including anthracyclines (e.g., doxorubicin), taxanes (e.g., paclitaxel), vinca alkaloids (e.g., vinblastine), antibiotics (e.g., actinomycin D), tyrosine kinase inhibitors (TKIs) (e.g., imatinib), epidermal growth factor receptor TKIs (e.g., erlotinib) which shows why this transporter can modulate the efficiency of treatment regimens used in many cancer types [28]. This evidence concerns the gene PGP and cancer.