Study of GLI1, GLI2 and GLI3 Transcripts Levels of Expression in Immunophenotypes of Breast Carcinoma and Breast Cancer Cell Lines
Ariadna Perez-Balaguer, Fernando Ortiz-Martinez, Maria Niveiro, F Ignacio Aranda, Enrique Lerma, Gloria Peiro. University General Hospital, Alicante, Spain; Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
Background: The Hedgehog (Hh) signaling pathway is a key developmental regulatory pathway, the deregulation of which has been implicated in several types of cancers, including breast carcinoma (BC). The GLI genes are effectors of the Hh signal in the cell. Our aim was to analyze the expression of GLI1, GLI2 and GLI3 genes in cell lines representing the different BC phenotypes, as well as in tumor samples to determine the role of the Hh pathway in the pathogenesis of the subtypes of BC.
Design: BC cell lines consisted of: MCF-7 and T-47D (Luminal type); BT-474 (Luminal with HER2+); SK-BR-3 (HER2+); MDA-MB-231 and MDA-MB-468 (triple negative/basal-like -TN/BL-), and normal epithelial breast cell line (184A1). Relative expression was determined using the ΔΔCT method and was expressed as relative quantification (RQ) unit. Samples of 130 BC were classified immunohistochemically into Luminal A and B (26%), HER2 (36%) or TN/BL (38%) phenotypes. The expression analysis results were correlated with clinicopathological factors and outcome of the patients.
Results: GLI3 was expressed in all cell lines, whereas GLI1 and GLI2 mRNA expression was only detected in TN/BL cell lines subtype. Expression of GLI1 was seen in 48% (63/130) of BC, GLI2 in 46% (60/130) and GLI3 in 100% (130/130). Among immunophenotypes, HER2 expressed less frequently GLI1 (24%, 15/47; p<0.000) or GLI2 (28%, 16/46; p=0.22). Age at diagnosis, tumors size, histologic grade, necrosis, lymph-vascular invasion or lymph-node status showed no significant association (p=ns). Disease-free survival (DFS) analysis showed that patients whose tumors expressed GLI1 had worse prognosis among all immunophenotypes: Luminal (63% vs. 83%), HER2 (64% vs. 68%) and TN/BL (76% vs. 89%) (p=0.048). However, GLI2 results correlated only in TN/BL (75% vs. 90%, p=0.03; Kaplan-Meier; log-rank test).
Conclusions: The Hh pathway is activated in all phenotypes of BC, reflected by the demonstration of GLI genes expression. Interestingly, GLI1 and GLI2 expression stratified patients at higher risk of recurrence specifically in TN/BL, making those genes good candidates for a potential therapy target. Our study shows a correlation of expression of GLI1 and GLI2 in the TN/BL cell lines and BC subtype.
Supported by Grant FCVI-HGUA 2012/C-08.
Wednesday, March 6, 2013 1:00 PM
Poster Session VI # 13, Wednesday Afternoon