Analysis of FOXP3 mRNA Expression in Subtypes of Breast Carcinoma and Breast Cancer Cell Lines
Fernando Ortiz-Martinez, Ariadna Perez-Balaguer, J Miguel Sempere-Ortells, Montserrat Rodrigo, Jose Ponce, Pascual Martinez-Peinado, Enrique Lerma, Jose Sanchez-Paya, F Ignacio Aranda, Gloria Peiro. University General Hospital, Alicante, Spain; University of Alicante, Alicante, Spain; Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
Background: The X-linked gene FOXP3 (Xp11.23) plays a key role in the immune suppressive function of regulatory T-cells (Tregs). More recently, it has been identified as a tumor suppressor gene that regulates tumor development. Here, we analyzed the expression of FOXP3 mRNA in breast cancer (BC) cell lines representing different phenotypes together with a series of BC patients.
Design: BC cell lines consisted of MCF-7, T-47D, BT-474, SK-BR-3, MDA-MB-231, MDA-MB-468 and a normal epithelial breast cell line, 184A1. Quantitative RT-PCR was performed using TaqMan® Assays. Mammary tissue and 184A1 were used as calibrators for tumor samples and BC cells, respectively; PUM1 and ACTB were the reference genes. Expression was determined using the ΔΔCT method and was expressed as fold change (FC). 189 BC tumors were classified immunohistochemically into Luminal (32%), HER2+ (36%) or TN/BL (32%).
Results: FOXP3 mRNA expression was higher in Luminal subtype cell lines (MCF-7 FC=4.87; T-47D FC=12.11) and in Luminal/HER2+ cells (BT-474 FC=4.77) compared with HER2+ cells (SK-BR-3 FC=2.83) and TN/BL cells (MDA-MB-231 FC=0.11; MDA-MB-468 FC=0.31). Median patient's age was 57 years (range 26-89) and the median follow-up was 85 months (range 6-259). Tumors showed vascular invasion in 51% (85/167), necrosis in 45% (74/164) and positive lymph node-status in 34% (62/181). Low FOXP3 mRNA expression (FC<0.5) (35%, 67/189) predominated in Luminal (42%, 27/65) and TN/BL subtypes (39%, 25/65; p=0.004), with lower histological grades (1+2 vs 3) (51%, 34/67; p=0.013). Patients with decreased FOXP3 tumor levels had longer overall survival (85% vs 69%; p=0.012). Phenotype stratification also showed a trend to better prognosis in those with Luminal (96% vs 79%), HER2+ (77% vs 63%) and TN/BL (76% vs 68%) tumors (p=0.11; Kaplan-Meier, log-rank test).
Conclusions: Low level of FOXP3 mRNA correlated with good prognostic factors. Moreover, we identified a subgroup of patients with better prognosis in all immunophenotypes of BC. The results of FOXP3 mRNA expression in BC cell lines and tissues were comparable only in TN/BL phenotype, showing low levels of expression.
Supported by Grants FIS 10/00082, AP-172/10, FCVI-HGUA (2010/PC-04 and 2011/PC-03).
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 33, Tuesday Afternoon