Phospho-Akt expression is high in a subset of triple negative breast cancer patients

Abstract

The most commonly used biomarkers to predict the response of breast cancer patients to therapy are oestrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2). Patients positive for these biomarkers are eligible for specific therapies such as anti-oestrogen therapy in the event of ER and PgR positivity, and trastuzumab, a monoclonal antibody, in the case of HER2 positive patients. Patients who are negative for all these three biomarkers, the so-called triple negatives, however, derive little benefit from such therapies. The PI3K/Akt pathway is activated in triple negative breast cancer cases, providing a possible target for therapy.

The activation of Akt was investigated in Maltese triple negative breast cancer cases using an antibody detecting Akt phosphorylated at serine 473 (anti-Akt pS473). The study showed that 26\% of triple negative breast cancer patients had an elevated level of Akt (pS473). Furthermore, FTY720, a pharmacological activator of the phosphatase PP2A, was shown to block Akt activation at a concentration of 1\textmu M, in HCC1937 cells subjected to insulin-like growth factor 1 (IGF-1).

Our data defined a subset of triple negative breast cancer patients based on high activity of AKT (pS473). This subset would be eligible for treatment using therapies which target the PI3K/Akt pathway, such as kinase inhibitors or phosphatase activators. In support of this, the BRCA1 mutant cells (HCC1937) were sensitive to the PP2a activator, FTY720. This suggests that FTY720 is a potential drug for use in adjuvant therapy in breast cancer cases having a high Akt (pS473).