The estrogen receptor alpha (ERa) plays a critical role in the pathogenesis and clinical behavior of breast cancer. To obtain further insights into the molecular basis of estrogen-dependent forms of this malignancy, we used real-time quantitative reverse transcription (RT)-PCR to compare the mRNA expression of 560 selected genes in ERa-positive and ERa-negative breast tumors. Fifty-one (9.1%) of the 560 genes were significantly upregulated in ERa-positive breast tumors compared with ERa-negative breast tumors. In addition to well-known ERa-induced genes (PGR, TFF1/PS2, BCL2, ERBB4, CCND1, etc.) and genes recently identified by cDNA microarray-based approaches (GATA3, TFF3, MYB, STC2, HPN/HEPSIN, FOXA1, XBP1, SLC39A6/LIV-1, etc.), an appreciable number of novel genes were identified, many of, which were weakly expressed. This validates the use of large-scale real-time RT-PCR as a method complementary to cDNA microarrays for molecular tumor profiling. Most of the new genes identified here encoded secreted proteins (SEMA3B and CLU), growth factors (BDNF, FGF2 and EGF), growth factor receptors (IL6ST, PTPRT, RET, VEGFR1 and FGFR2) or metabolic enzymes (CYP2B6, CA12, ACADSB, NAT1, LRBA, SLC7A2 and SULT2B1). Importantly, we also identified a large number of genes encoding proteins with either pro-apoptotic (PUMA, NOXA and TATP73) or anti-apoptotic properties (BCL2, DNTP73 and TRAILR3). Surprisingly, only a small proportion of the 51 genes identified in breast tumor biopsy specimens were confirmed to be ERa-regulated and/or E2-regulated in vitro (cultured cell lines). Therefore, this study identified a limited number of genes and signaling pathways, which better delineate the role of ERa in breast cancer. Some of the genes identified here could be useful for diagnosis or for predicting endocrine responsiveness, and could form the basis for novel therapeutic strategies.

The ErbB-driven autocrine growth pathway has been implicated in the development and progression of most common human epithelial malignancies; its blockade is therefore a promising therapeutic strategy, and several candidate drugs are currently undergoing clinical trials. Paradoxically, little is known of the expression pattern of these 4 genes in human tumors, and the clinical significance of the 2 most recently discovered ERBB genes, ERBB3 and ERBB4, is unclear. We used a real-time quantitative RT-PCR assay to quantify ERBB family mRNA copy numbers in a large series of breast tumors from patients with known long-term outcome. ERBB gene expression varied widely, by more than 2 orders of magnitude for ERBB1 and ERBB3, more than 3 orders for ERBB2 and more than 4 orders for ERBB4. We found a positive correlation between ERBB3 and ERBB4 mRNA levels, and a negative correlation between the expression of these 2 latter genes and that of ERBB1. Compared to normal breast tissue, ERBB1 was underexpressed (82.3% of tumors), ERBB2 (16.9%) and ERBB3 (46.2%) were overexpressed and ERBB4 was both underexpressed (24.6%) and overexpressed (29.2%). Links were also found between ERBB status on the one hand and Scarff-Bloom-Richardson (SBR) histopathological grade and estrogen receptor alpha (ERa) status on the other hand. Relapse-free survival (RFS) was shorter among patients with ERBB3-overexpressing tumors (p‫)2900.0؍‬ and longer among those with ERBB4-underexpressing tumors (p‫)5800.0؍‬ relative to patients with normal expression of the respective genes; in contrast, RFS was not significantly influenced by ERBB1 or ERBB2 mRNA status. Only ERBB4 status retained prognostic significance in Cox multivariate regression analysis (p‫.)510.0؍‬ Our results point to the involvement of several ErbB-specific ligands (amphiregulin and neuregulin 1) and enzymes or adaptor molecules (PI3K, Src, Shc and Grb7) in the ErbB pathway dysregulation associated with breast cancer. These findings reveal a complex expression pattern of ERBB gene family members in breast tumors and suggest that it is this pattern of expression, rather than the expression of individual family members, that should be taken into account when evaluating antitumoral drugs designed to target these receptors. © 2003 Wiley-Liss, Inc. Key words: breast cancer; ERBB family gene expression; real-time RT-PCR quantification; prognostic valueIn multicellular organisms, communication among cells is an absolute requirement for the regulation of complex biological processes such as growth, differentiation, motility and death. Receptor tyrosine kinases, which are the primary mediators of many intercellular signals, exist in structurally distinct forms that can be grouped into about 20 functionally related subfamilies. 1 ErbB proteins belong to subclass I of the superfamily of receptor tyrosine kinases. The ErbB family has evolved from a single ligandreceptor combination in Caenorhabditis elegans, 2 to 1 receptor and 4 ligands in Drosophila melanogaster, 3 and to 4 ErbB receptors that bin...

Purpose: Inflammatory breast cancer (IBC) is a rare but particularly aggressive form of primary breast cancer. The molecular mechanisms responsible for IBC are largely unknown.Experimental Design: To obtain further insight into the molecular pathogenesis of IBC, we used real-time quantitative reverse transcription (RT)-PCR to quantify the mRNA expression of 538 selected genes in IBC relative to non-IBC.Results: Twenty-seven (5.0%) of the 538 genes were significantly up-regulated in IBC compared with non-IBC. None were down-regulated. The 27 up-regulated genes mainly encoded transcription factors (JUN, EGR1, JUNB, FOS, FOSB, MYCN, and SNAIL1), growth factors (VEGF, DTR/HB-EGF, IGFBP7, IL6, ANGPT2, EREG, CCL3/ MIP1A, and CCL5/RANTES) and growth factor receptors (TBXA2R, TNFRSF10A/TRAILR1, and ROBO2). We also identified a gene expression profile, based on MYCN, EREG, and SHH, which discriminated subgroups of IBC patients with good, intermediate, and poor outcome.Conclusion: Our study has identified a limited number of signaling pathways that require inappropriate activation for IBC development. Some of the up-regulated genes identified here could offer useful diagnostic or prognostic markers and could form the basis of novel therapeutic strategies.