Transfection of ErbB2 in MCF7 breast cancer cells that express ErbB3 caused a PI3K-dependent activation of Akt, and was associated with an increased resistance of the cells to multiple chemotherapeutic agents (paclitaxel, doxorubicin, 5-fluorouracil, etoposide, and camptothecin) [429]. The gene discussed is PIK3CA; the disease is breast cancer.