No abstract

Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) are the two major histological types of breast cancer worldwide. Whereas IDC incidence has remained stable, ILC is the most rapidly increasing breast cancer phenotype in the United States and Western Europe. It is not clear whether IDC and ILC represent molecularly distinct entities and what genes might be involved in the development of these two phenotypes. We conducted comprehensive gene expression profiling studies to address these questions. Total RNA from 21 ILCs, 38 IDCs, two lymph node metastases, and three normal tissues were amplified and hybridized to ϳ42,000 clone cDNA microarrays. Data were analyzed using hierarchical clustering algorithms and statistical analyses that identify differentially expressed genes (significance analysis of microarrays) and minimal subsets of genes (prediction analysis for microarrays) that succinctly distinguish ILCs and IDCs. Eleven of 21 (52%) of the ILCs ("typical" ILCs) clustered together and displayed different gene expression profiles from IDCs, whereas the other ILCs ("ductal-like" ILCs) were distributed between different IDC subtypes. Many of the differentially expressed genes between ILCs and IDCs code for proteins involved in cell adhesion/motility, lipid/fatty acid transport and metabolism, immune/defense response, and electron transport. Many genes that distinguish typical and ductal-like ILCs are involved in regulation of cell growth and immune response. Our data strongly suggest that over half the ILCs differ from IDCs not only in histological and clinical features but also in global transcription programs. The remaining ILCs closely resemble IDCs in their transcription patterns. Further studies are needed to explore the differences between ILC molecular subtypes and to determine whether they require different therapeutic strategies.

BACKGROUND It was demonstrated previously that the Snail family of transcription factors and Smad‐interacting protein 1 (Sip1) regulate E‐cadherin and matrix metalloproteinase 2 (MMP‐2) expression, cellular morphology, and invasion in carcinoma. For the current study, the authors analyzed the relation between the expression of Snail, Slug, and Sip1; the expression of MMP‐2 and E‐cadherin; and clinical parameters in patients with metastatic ovarian and breast carcinoma. METHODS One hundred one fresh‐frozen, malignant effusions from patients who were diagnosed with gynecologic carcinomas (78 ovarian carcinomas and 23 breast carcinomas) were studied for mRNA expression of Snail, Slug, Sip1, MMP‐2, and E‐cadherin using reverse transcriptase‐polymerase chain reaction analysis. Snail mRNA and E‐cadherin protein expression levels also were studied in ovarian carcinoma effusions using in situ hybridization and immunocytochemistry. The results were analyzed for possible correlation with clinicopathologic parameters in both tumor types. RESULTS E‐cadherin mRNA expression was lower in breast carcinoma (P = 0.001), whereas Snail expression was higher (P = 0.003). The Snail/E‐cadherin ratio (P < 0.001) and the Sip1/E‐cadherin ratio (P = 0.002) were higher in breast carcinomas. Sip1 mRNA expression (P < 0.001) and Slug mRNA expression (P < 0.001) were correlated with the expression of MMP‐2 in ovarian carcinomas. The Sip1/E‐cadherin ratio was higher in primary ovarian carcinomas at the time of diagnosis compared with postchemotherapy ovarian carcinoma effusions (P = 0.003), higher in Stage IV tumors compared with Stage III tumors (P = 0.049), and higher in pleural effusions compared with peritoneal effusions (P = 0.044). In a univariate survival analysis of patients with ovarian carcinoma, a high Sip1/E‐cadherin ratio predicted poor overall survival (P = 0.018). High E‐cadherin mRNA expression predicted better disease‐free survival (P = 0.023), with a similar trend for a low Slug/E‐cadherin ratio (P = 0.07). High Snail mRNA expression predicted shorter effusion‐free survival (P = 0.008), disease‐free survival (P = 0.03), and overall survival (P = 0.008) in patients with breast carcinoma. CONCLUSIONS Transcription factors that regulate E‐cadherin were expressed differentially in metastatic ovarian and breast carcinoma. Snail may predict a poor outcome in patients who have breast carcinoma metastatic to effusions. E‐cadherin expression generally was conserved in effusions from patients with ovarian carcinoma, but the subset of patients with postulated Sip1‐induced repression of this adhesion molecule had a significantly worse outcome. This finding was in agreement with the stronger suppression of E‐cadherin by Snail and Sip1 in breast carcinoma effusions, a clinical condition associated with extremely poor survival. Cancer 2005. © 2005 American Cancer Society.

Prediction of the clinical outcome of breast cancer is multi-faceted and challenging. There is growing evidence that the complexity of the tumour micro-environment, consisting of several cell types and a complex mixture of proteins, plays an important role in development, progression, and response to therapy. In the current study, we investigated whether invasive breast tumours can be classified on the basis of the expression of extracellular matrix (ECM) components and whether such classification is representative of different clinical outcomes. We first examined the matrix composition of 28 primary breast carcinomas by morphology and gene expression profiling using 22K oligonucleotide Agilent microarrays. Hierarchical clustering of the gene expression profile of 278 ECM-related genes derived from the literature divided the tumours into four main groups (ECM1-4). A set of selected differentially expressed genes was validated by immunohistochemistry. The robustness of the ECM classification was confirmed by studying the four ECM groups in a previously published gene expression data set of 114 early-stage primary breast carcinomas profiled using cDNA arrays. Univariate survival analysis showed significant differences in clinical outcome among the various ECM subclasses. One set of tumours, designated ECM4, had a favourable outcome and was defined by the overexpression of a set of protease inhibitors belonging to the serpin family, while tumours with an ECM1 signature had a poorer prognosis and showed high expression of integrins and metallopeptidases, and low expression of several laminin chains. Furthermore, we identified three surrogate markers of ECM1 tumours: MARCO, PUNC, and SPARC, whose expression levels were associated with breast cancer survival and risk of recurrence. Our findings suggest that primary breast tumours can be classified based upon ECM composition and that this classification provides relevant information on the biology of breast carcinomas, further supporting the hypothesis that clinical outcome is strongly related to stromal characteristics.