PDK1 and breast cancer: Given the fact that there were considerable diversities in the expression and activation-specific phosphorylation levels of PDK1 and AKT1 among the BC cell lines, and the fact that the phosphorylation of PDK1 or AKT1 was related to the sensitivity of BC cells to chemotherapy drugs, cells highly expressing Ser241-phosphorylated PDK1 (MDA453 and SKBR3 cells) were shown to be more resistant to gemcitabine than cells exhibiting high levels of Ser473-phosphorylated AKT1 (MDA468 and MDA231 cells).