ERBB2 and breast cancer: Several new studies suggest that HER2/PI3K/Akt signaling may confer resistance to a panel of chemotherapeutic agents with different mechanisms of actions: adriamycin (an anthracycline) [6,7,8], mitoxantrone (an anthracycline) [8], 5-fluorourocil (an antimetabolite) [7,8], etoposide (a DNA-damaging agent) [7,8], camptothecin (a topoisomerase I inhibitor) [7] etc. Such resistance may be relevant to the effects of MDR in breast cancer.