Abstract 4612: SET overexpression is associated with recurrence-free survival in patients with primary breast cancer receiving adjuvant tamoxifen treatment

Abstract

Abstract Background: Estrogen receptor (ER) positive breast cancer accounts for 70% of breast cancer. Tamoxifen, a selective ER modulator, remains an important hormone therapeutic agent for patients with ER positive breast cancer. A number of patients receiving adjuvant tamoxifen still experience recurrence in the long term. In current study we explored the clinical significance of four biomarkers including SET, CIP2A, PP2A and Akt in ER positive breast cancer patients receiving adjuvant tamoxifen. Methods: Specimens were from ER positive breast cancer patients treated with adjuvant tamoxifen for a median of duration of 54.8 months with documented outcomes. The median follow-up was 106 months. Immunohistochemical staining for SET, CIP2A, p-PP2A (Tyr 307), p-Akt were performed and a H-score was assigned to quantify protein expression. In silico analysis of gene expression was evaluated from the public database KM plotter (available at: http://kmplot.com/analysis/). Human ER positive breast cancer cell line MCF7 cells were used for in vitro studies. MTT assay, flow cytometry and Western blot were used to assess the cells properties. Estrogen response element (ERE)-dependent luciferase activity was assessed by co-transfection of SET-expressing or control plasmids and 3⊆ERE bearing reporter plasmids into MCF7 cells and stimulated with estrogen. Results: In 218 primary ER positive breast cancer patients treated with adjuvant tamoxifen, 17 (7.8%) suffered from recurrence or metastasis. Higher expressions of SET and CIP2A by IHC analysis were associated with poor recurrence-free survival (RFS). Multivariate analysis revealed SET was independently correlated with worse RFS (Hazard ratio=3.72, 95% confidence interval 1.26-10.94, p=0.017). In silico, KM-plotter analysis revealed higher gene (mRNA) expressions of SET, PPP2CA and Akt1 significantly correlated with worse RFS in breast cancer patients receiving adjuvant tamoxifen therapy. Because SET appeared to be the most prognostic for RFS among the four markers, we next explored the biological role in vitro. Tamoxifen exerted anti-proliferation and apoptotic effects in a dose-dependent manner of MCF7 cells. SET overexpression reduced tamoxifen-induced anti-proliferation in MCF-7 cells, in association with upregulated p-ER, suggesting that SET may affect ER pathway via the serine/threonine kinase PP2A. SET drove luciferase activity in an ERE-dependent manner, and also enhanced estrogen-promoted luciferase activity. Conclusions: Protein SET is a prognostic biomarker in ER positive breast cancer patients treated with tamoxifen and may contribute to tamoxifen resistance by modulating ER signaling pathway. Citation Format: Yu-Hsiang Huang, Pei-Yi Chu, Ji-Lin Chen, Chun-Teng Huang, Chia-Han Lee, Ka-Yi Lau, Wan-Lun Wang, Yu-Ling Wang, Pei-Ju Lien, Ling-Ming Tseng, Chun-Yu Liu. SET overexpression is associated with recurrence-free survival in patients with primary breast cancer receiving adjuvant tamoxifen treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4612.