Notch and Jak/STAT signaling pathways in breast carcinoma of luminal and basal/triple-negative immunophenotypes.

Abstract

618 Background: Notch and Jak/STAT pathways have a role in normal cell growth and development, but activation has been reported in several neoplasms. A relationship with positive hormonal receptor (HR) breast carcinomas (BC) has been suggested. We studied the Notch and Jak/STAT pathways in a series of BC of luminal and basal/triple negative (TN) immunophenotypes to determine their involvement. Methods: 170 invasive BC of luminal A (ER and PR ≥ 50% positive nuclei; and p53 < 20% or Ki67 < 20%), luminal B (ER and/or PR <50%, and p53 ≥ 20% or Ki67 ≥ 20%), and basal/TN (ER/PR/HER2-negative ± CK5/6 ± EGFR) immunophenotypes were analyzed. Total RNA was isolated from 2-3 paraffin-embedded cylinders from preselected tumor areas, and retrotranscripted to cDNA. RT-PCR was performed by Syber Green to study the expression of Notch1, 2, 4; Jagged1 (Notch pathway), and STAT3 (Jak/STAT pathway). The primers were tested in triplicate; RT minus controls and two commercial positive controls (total human and BC RNA) were included. The quantification was normalized to β-actin gene (Spearman rank correlation coefficient: r = 0.82; p < 0.05). Relative mRNA expression levels were carried out using the ΔΔCT method. A pool of normal breast tissues was used as calibrator for luminal BC, (similar gene expression levels were found in the adjacent tissue to all luminal BC). Each basal/TN BC was correlated with their corresponding normal breast tissue. The results were analyzed statistically by Chi-square and Fisher's exact test. Results: Similar overexpression in all analyzed genes was found in both luminal subtypes. In contrast, in the basal/TN group Notch1 and Jagged1 were down-regulated (Notch1 p < 0.000, OR: 2.849 -1.492-5.439-; Jagged1 p = 0.024, OR: 1.583 -0.964- 2.600-); and no differences were found for Notch4 and Notch2. Regarding STAT3, overexpression was detected in both phenotypes. Conclusions: The Notch pathway is activated in BC of luminal phenotype but not in the basal/TN group, in which down-regulation predominates, supporting its role in HR-positive BC. Nevertheless, up-regulation of the Jak/STAT pathway is present in all analyzed subtypes. Supported by grant FIS 03/1411and FCVI- HGUA/2006. No significant financial relationships to disclose.