PIK3CA and breast cancer: p70S6K encoded by RPS6KB1 was knocked down using three different siRNAs in BT-474 and MCF-7 breast cancer cell lines, since these cell lines show high-level amplification and overexpression of RPS6KB1. Ly294002 and rapamycin are known to target PI3K/mTOR pathway upstream of p70S6K.