PIK3CA and breast cancer: PIK3CA knockdown abolished growth promoted by PRR11 overexpression, suggesting that PRR11-mediated cell growth requires PIK3CA. Consistent with these data, the PIK3CA dependence score of 57 breast cancer cell lines significantly correlated with PRR11 copy number in DEMETER2, a combined large-scale RNAi screening dataset41 (Fig. 7a).