P-gp expression has been detected in a high percentage of breast cancers and was found to be increased after exposure to chemotherapeutic drugs (particularly those known to be P-gp substrates), and correlated with a worse response to treatment in both the adjuvant and neoadjuvant settings, but a direct role of P-gp as a cause of clinical drug resistance has not been adequately tested, even in breast cancer [7]. Here, PGP is linked to breast cancer.