PIK3R1 and breast carcinoma: To further evaluate the predictive value of PIK3CA/PIK3R1 mutations, we examined the potential correlation of ARQ 092 and ARQ 751 sensitivity with PIK3CA mutations in breast cancer cell lines and found 88% and 100% (7 out of 8 or 8 out of 8 cell lines) of breast cancer cell lines with PIK3CA mutations were sensitive to ARQ 092 or ARQ 751, respectively (S3A and S3B Table).