Abstract# 1895: PIK3CA mutation-associated gene expression signature correlates with deactivation of the PI3K pathway and predicts benefit to endocrine therapy in high-risk ER+ …

Background: Deregulated phosphatidylinositol 3-kinase (PI3K) signaling has been implicated in all the hallmarks of carcinogenesis. In this present study, we sought to investigate the frequency, phenotype and clinical relevance related to PIK3CA mutation and its associated gene expression patterns in a large homogenous data set of estrogen receptor (ER) positive BC. Material and Methods: Mutational analysis of the PIK3CA gene was performed in 173 primary ER+ BC. PIK3CA mutation-associated gene expression signature was developed using the Affymetrix platform. The association between PIK3CA mutation-associated expression patterns and clinical outcome was performed using several publicly available microarray datasets including ~1000 systemically untreated and ~500 tamoxifen only treated ER+ BC. Results: The incidence of PIK3CA mutations was 26%. Tumors with PIK3CA mutation demonstrated …