Purpose: Mutations of the PI3K/AKT/mTOR signaling pathway occur in 70% of all breast cancers and represent a clinically useful marker for disease prognosis and patient management. The purpose of this work was to study the main somatic PIK3CA gene mutations in breast cancer patients and the search for a relationship with the main clinical and pathological characteristics and the effect of neoadjuvant chemotherapy (NAC).
Methods: The study involved 29 patients with luminal B breast cancer. DNA was isolated from samples of tumor tissue before and after treatment using the QIAamp DNA mini Kit (Qiagen, Germany). Samples were prepared for sequencing by amplification with primers containing TruSeq index and adapter sequences (Illumina, USA) using Encyclo polymerase.
Results: We found 5 different somatic changes in 28% of patients: c.3140A> G (p.His1047Arg), c.3140A> T (p.His1047Leu), c.1624G> A (p.Glu542Lys), c.1633G> A ( p.Glu545Lys), c.3145G> C (p.Gly1049Arg). In the group of patients with mutations, 50% showed PIK3CA gene amplifications. The c.3140A> T (p.His1047Leu) mutation was associated with low disease-free survival rates. PIK3CA gene mutations were observed in 38% of patients with HER2-subtype, and metastasis-free survival rates were, on average, 1.5 times higher than in patients with normal gene status.