PIK3CA mutations are seemingly the most common driver mutations in breast cancer with H1047R and E545K being the most common of these, accounting together for around 60% of all PIK3CA mutations and have promising therapeutic implications.
Formalin-fixed paraffin-embedded tumour specimens from 118 HER2-overexpressing breast cancer patients treated with radical local therapy and trastuzumab in adjuvant setting were used for the assessment of: (1) PIK3CA gene mutations (p.H1047R and p.E545K) by qPCR, and (2) expression of Ki-67, EGFR, MUC4, HER3 and PTEN by immunohistochemistry.
This study proposed to investigate the relationship of PIK3CA somatic mutations, the most common activating mutations in human breast cancer (BC), and the efficacy of neoadjuvant chemotherapy (NCT).Using a novel liquid chip technology,PIK3CA DNA somatic mutations and HER2, PTEN, EGFR mRNA expression profiles were analyzed in formalin fixed paraffin embedded samples of 93 BC patients treated with epirubicin plus docetaxel NCT.PIK3CA mutations were found in 30 patients (32.3%), in which the point mutations of E542K, E545K, H1047L and H1047R were 4.3, 9.7, 4.3 and 14.0%respectively.
We further validated the approach in breast cancer cells with mutational activation of PIK3CA, where tandem mass spectrometry detected and quantitatively measured the abundance of a helical domain mutant (E545K) of PIK3CA connected to PI3K activation.