Proteomic Profiling of Breast Carcinomas Based on Claudin Expression Pattern.

Abstract

Abstract INTRODUCTION. With the advent of molecular techniques, the UNC workgroup (Perou 2000) has identified at least five biologically distinct subtypes (luminal A, luminal B, Her2+, triple-negative, normal-like) with genomic characterization of human breast tumors. The same lab (Herschkowitz 2007) identified a new and rare molecular subtype of human breast cancer which is now being referred to as the claudin-low subgroup. In our study, we aimed to perform a thorough analysis of the claudin, beta-catenin and E-cadherin protein expression pattern in invasive ductal (IDCs) and lobular (ILCs) breast carcinomas of different grades, their corresponding lymph node metastases (LNMs) and normal adjacent tissues NATs). METHODS. Tissue microarrays of 98 samples (59 IDCs: 20 grade 3, 26 grade 2 and 13 grade 1; 39 ILCs: 8 grade 3, 24 grade 2 and 7 grade 1), their corresponding LNMs and NATs have been analyzed immunohistochemically for beta-catenin, claudin-1, -2, -3, -4, -5, -7 and E-cadherin expression. The stained slides were digitalized with a slide scanner and the reactions were evaluated semiquantitatively according to our previous practice (Kulka 2009). RESULTS. Based on our evaluation, we were able to conclude the following significant results: 1) There is a markedly different expression of beta-catenin, claudin-1, -3, -4 and -7 in normal and neoplastic tissues. 2) Claudin-1, -2 and E-cadherin are able to differentiate ductal and lobular invasive carcinomas. 3) In E-cadherin-negative IDCs beta-catenin and claudin-7 is expressed on lower levels than in the E-cadherin-positive IDCs. In E-cadherin-positive ILCs the beta-catenin, claudin-4 and -7 is expressed at higher levels than in E-cadherin-negative ILCs. 4) Claudin-1 and -2 protein expression in the molecular subtypes can also distinguish luminal subtypes from each other and the HER2+ and triple-negative group. 5) Claudin-3 and E-cadherin or claudin-4 and -7 are both able to separate a claudin-low subtype of tumors with confidence.This later subclass also expresses beta-catenin on a lower level than the others. 6) Hierarchical clustering of primary carcinomas based on claudin expression reflects proliferation rates of the primary tumors. 7) Beta-catenin, claudin-1, -2 can differentiate primary carcinomas and lymph node metastases. 8) Histological grade correlates with claudin-1, -4 and -7 expression. CONCLUSION. According to our observations, the expression of TJ molecules, especially claudins, are different in tumors compared to normal breast tissue. Also, we could identify a claudin-low tumor subtype based on the loss of claudin-4 and -7 expression. Certain claudins are also differently expressed in the lymph node metastases as demonstrated by immunohistochemistry. Claudin profile of breast tumors correlates with histopathological variables and most likely it reflects an important mechanism of cancer differentiation and progression. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6123.