Cellular responses to ErbB-2 overexpression in human mammary luminal epithelial cells: comparison of mRNA and protein expression

Abstract

Microarray analysis offers a powerful tool for studying the mechanisms of cellular transformation, although the correlation between mRNA and protein expression is largely unknown. In this study, a microarray analysis was performed to compare transcription in response to overexpression of the ErbB-2 receptor tyrosine kinase in a model mammary luminal epithelial cell system, and in response to the ErbB-specific growth factor heregulin b1. We sought to validate mRNA changes by monitoring changes at the protein level using a parallel proteomics strategy, and report a surprisingly high correlation between transcription and translation for the subset of genes studied. We further characterised the identified targets and relate differential expression to changes in the biological properties of ErbB-2-overexpressing cells. We found differential regulation of several key cell cycle modulators, including cyclin D2, and downregulation of a large number of interferon-inducible genes, consistent with increased proliferation of the ErbB-2-overexpressing cells. Furthermore, differential expression of genes involved in extracellular matrix modelling and cellular adhesion was linked to altered adhesion of these cells. Finally, we provide evidence for enhanced autocrine activation of MAPK signalling and the AP-1 transcription complex. Together, we have identified changes that are likely to drive proliferation and anchorage-independent growth of ErbB-2-overexpressing cancer cells.

Copine-III interacts with ErbB2 and promotes tumor cell migration

“…Copine-III was expressed to varying degrees in the breast cancer cells lines, with the highest levels in SKBr3 and BT474, both having ERBB2 amplification (Figure 8a). These data correlate with previous publications showing Copine-III upregulation in response to ErbB2 overexpression (Gharbi et al, 2002;White et al, 2004). We also examined Copine-III RNA expression in 49 primary breast tumors (Farmer et al, 2005).…”

“…In primary human tumors, there was some evidence for a functional relationship between Copine-III and ErbB2, because Copine-III mRNA and protein levels were shown to correlate with ErbB2 expression (Gharbi et al, 2002;White et al, 2004). We have extended these studies by examining a panel of 49 breast tumors (Farmer et al, 2005) and showing that there is a significant correlation between CPNE3 RNA levels, and ERBB2 gene amplification and expression.…”

“…As a control for equal loading, fractions of the input cell lysate were also loaded on the gel (input). (Gharbi et al, 2002;White et al, 2004). Therefore, we examined Copine-III in more detail using the breast cancer cell lines T47D, with moderate ErbB2 levels, and SKBr3, which has ERBB2 amplification and very high levels of the receptor (Lane et al, 2000).…”

“…Interestingly, Copine-III was shown to be upregulated in tumor cells in response to ErbB2 overexpression (Gharbi et al, 2002;White et al, 2004). We examined the role of Copine-III downstream of ErbB2 receptor signaling and show here that Copine-III is a Ca 2 þ -dependent, phospholipid-binding protein that interacts with activated ErbB2 at the plasma membrane (PM) of tumor cells.…”

Proteomic analysis of breast cancer tissue reveals upregulation of actin‐remodeling proteins and its relevance to cancer invasiveness

“…This underscores the need to discover new biological markers or targets for the early detection and management of breast cancer [1]. Breast cancer is a complex disease during which the accumulation of numerous molecular alterations causes genetic instability, cell proliferation, and acquisition of an increasingly invasive and resistant phenotype [2,3]. Since the molecular character of each breast cancer is different and of diverse origin, prognostication, and management of breast cancer can be significantly improved by using multiple markers.…”