PTEN Gene Expression and Tamoxifen-Resistance in Steroid Hormone Receptor Positive Breast Cancer Patients, a cross-sectional study between 2006 and 2016

PI3K/Akt/mTOR pathway is important in inducing resistance to hormone therapy in patients with hormone positive breast cancer. One regulator of this pathway is the PTEN gene. This study was performed with aim to compare the expression of PTEN gene in hormone receptor positive breast cancer patients between patients with sensitive and resistant to tamoxifen.

This cross-sectional and retrospective study was performed on 80 hormone receptor positive breast cancer patients who had referred to oncology clinics of Mashhad University of Medical Sciences from 2006 to 2016. Tissue samples of tamoxifen-sensitive and -resistant patients (recurrence/metastasis occurring during the first 5 years of adjuvant hormone therapy) were immunohistochemically evaluated for PTEN expression. Data were analyzed by SPSS software (version 16) and Independent t-test, U Mann-Whitney and chi-square tests. P<0.05 was considered statistically significant.

In this study, 80 patients were evaluated in two groups of tamoxifen sensitive and resistant. The expression of PTEN in tamoxifen-sensitive and resistant patients was 97.5% and 27.5%, respectively (p=0.001). However, in patients with more advanced lymph node involvement, the expression of PTEN was significantly reduced (p=0.001), there was no significant relationship between PTEN expression and tumor size (p=0.19), tumor grade (p=0.14) and Her2/neu expression (p=0.85).

There is association between PTEN gene expression and tamoxifen resistance.