PIK3CA and neoplasm: Overall, E2 levels were significantly positively correlated with tumor enrichment in the hallmark estrogen response pathway (red bars, Figure 6a) and with the expression of genes demonstrated to be transcriptionally regulated by ER (BCL2, IGF1R, GATA3, PIK3CA) and ligand-dependent ER (ESR1, XBP1, TFF1) [31] (Figure 6c).