Grb2 and Shc Adapter Proteins Play Distinct Roles in Neu (ErbB-2)-Induced Mammary Tumorigenesis: Implications for Human Breast Cancer

Abstract

Amplification of the Neu (ErbB-2 or HER-2) receptor tyrosine kinase occurs in 20 to 30% of human mammary carcinomas, correlating with a poor clinical prognosis. We have previously demonstrated that four (Y1144 Y1201, Y1227 and Y1253) of the five known Neu autophosphorylation sites can independently mediate transforming signals. The transforming potential of two of these mutants correlates with their capacity to recruit Grb2 directly to Y1144 (YB) or indirectly through Shc to Y1227 (YD). Here, we demonstrate that these transformation-competent neu mutants activate extracellular signal-regulated kinases and stimulate Ets-2-dependent transcription. Although the transforming potential of three of these mutants (YB, YD, and YE) was susceptible to inhibition by Rap1A, a genetic antagonist of Ras, the transforming potential of YC was resistant to inhibition by Rap1A. To further address the significance of these ErbB-2-coupled signaling molecules in induction of mammary cancers, transgenic mice expressing mutant Neu receptors lacking the known autophosphorylation sites (NYPD) or those coupled directly to either Grb2 (YB) or Shc (YD) adapter molecules were derived. In contrast to the NYPD strains, which developed focal mammary tumors after a long latency period with low penetrance, all female mice derived from YB and YD strains rapidly developed mammary tumors. Although female mice from several independent YB or YD lines developed mammary tumors, the YB strains developed lung metastases at substantially higher rates than the YD strains. These observations argue that Grb2 and Shc play important and distinct roles in ErbB-2/Neu-induced mammary tumorigenesis and metastasis.Neu (ErbB-2), the epidermal growth factor receptor, ErbB-3, and ErbB-4 are transmembrane receptor tyrosine kinases (RTKs) which comprise the class I or ErbB RTK family (reviewed in references 21, and 35). Neu or ErbB-2 amplification and elevated expression has been implicated in the etiology of human ovarian and breast cancers and correlates with a poor clinical prognosis in breast cancer patients (3,44,45). Moreover, anti-ErbB-2 antibodies demonstrate efficacy for treatment of breast cancer patients with elevated ErbB-2 levels (4). Direct evidence supporting a role for neu in mammary tumorigenesis derives from observations made with transgenic mice expressing oncogenic forms of the neu oncogene under the transcriptional control of mouse mammary tumor virus (MMTV) enhancer. Mammary epithelial cell-specific expression of wildtype Neu or constitutively active Neu or ErbB-2 alleles in the mammary epithelia of transgenic mice results in the induction of metastatic mammary tumors which histologically resemble human comedocarcinomas (2,6,18,19,30). Taken together, these data suggest that activation of ErbB-2 or Neu plays a causal role in mammary tumorigenesis.Despite the importance of Neu in human malignancies, the molecular mechanism by which this RTK transforms cells and confers metastatic potential is not known. Following Neu receptor dimerization, class I R...

SLK-mediated phosphorylation of paxillin is required for focal adhesion turnover and cell migration

“…Overexpression of HER2 (ErbB2 (mouse); Neu (rat); HER2 (human), a receptor tyrosine kinase (RTK) that is a member of the epidermal growth factor (EGF) family, is associated with increased progression and metastasis in human breast cancer [43,118,147]. Approximately, 25-30% of breast cancer patients overexpressing HER2 present with a more aggressive clinical course and decreased disease-free survival due to more invasive tumors [148,149].…”

Integrin-linked kinase has a critical role in ErbB2 mammary tumor progression: implications for human breast cancer

“…Flash-frozen tumor pieces were prepared in phospholipase-C-g lysis buffer (Dankort et al, 2001). Protein amounts were quantified by DC Protein (Bio-Rad, Mississauga, Ontario, Canada).…”

Copine-III interacts with ErbB2 and promotes tumor cell migration

“…Tyr1248 and pTyr1248-containing peptides were incubated with T47D cell lysates and used as affinity reagents. Shc, which has been identified as a pTyr1248-binding protein (Dankort et al, 2001;Schulze et al, 2005), was also examined as a control. These results confirmed the specific binding of Copine-III to the pTyr1248-containing peptide (Figure 1d).…”

“…Tyr1028 couples to a pathway implicated in negative regulation of NeuT transforming potential, whereas the four other sites have a potentiating effect. Tyr1144, Tyr1201 and Tyr1227 signal through the Ras/Erk pathway by binding Grb2, Crk and Shc (Akiyama et al, 1991;Dankort et al, 1997Dankort et al, , 2001, which also binds Tyr1253 (Schulze et al, 2005). The role of pTyr residues has also been examined in migration assays.…”