PTEN and breast cancer: Thus, the 14-3-3 proteins were co-immunoprecipitated with 9J10 in lysates from the breast cancer cell line MCF7 and the ovarian cancer cell line SKOV3 (both of which carry activating mutations in PI3K), the breast cancer cell line BT-549 (which carries a frameshift mutation inactivating PTEN), and the transformed human embryonic kidney cell line HEK293T.