To further verify an association between the observed proteomic profile and capivasertib response, we applied corresponding targeted assays, validated in accordance with the NCI’s Clinical Proteomics Tumor Analysis Consortium (CPTAC) guidelines, to precisely quantify proteins of interest in analogous PIK3CA-altered breast cancer cell lines with varying sensitivities to capivasertib. This evidence concerns the gene PIK3CA and breast carcinoma.