Amplification of the epidermal growth factor receptor in astrocytic tumours by chromogenic in situ hybridization: association with clinicopathological features and patient survival.

Chromogenic in situ hybridization (CISH) was used to detect amplification of the epidermal growth factor receptor (EGFR) gene in tissue microarrays of tumours derived from 287 patients with grade II-IV diffuse astrocytomas. Amplification was found in 32% of the tumours with a highly significant association with histological grade (4% in grade II, 21% in grade III and 39% in grade IV; P < 0.001). Amplification of the EGFR gene was more common in primary than in secondary glioblastomas (41%vs. 16%, P = 0.033). Overexpression of EGFR mRNA and protein (wild-type and vIII variant) was found to correlate with EGFR gene amplification (P = 0.028, P = 0.035 and P = 0.014 respectively), but wild-type EGFR protein was also frequently overexpressed in tumours without EGFR gene amplification. Patients with older age (P < 0.001) and tumours with lack of p53 overexpression (P = 0.03) and higher apoptosis rate (P < 0.001) had significantly more EGFR gene amplifications than their counterparts. No such correlation with apoptosis was found in glioblastomas. The survival of patients with EGFR gene-amplified grade III tumours was significantly shorter than in those with grade III non-amplified tumours (P = 0.03). No such difference was noted in glioblastomas (grade IV tumours). Our data verify the central role of EGFR in the pathobiology of astrocytic tumours, and highlight the advantages of CISH as a simple and practical assay to screen for EGFR gene amplification in astrocytic tumours.

Amplification of HER-2 in gastric carcinoma: association with Topoisomerase IIalpha gene amplification, intestinal type, poor prognosis and sensitivity to trastuzumab.

BACKGROUND: HER-2/neu gene amplification has predictive value in breast cancer patients responding to trastuzumab. We wanted to investigate the frequency and clinical significance of HER-2/neu amplification in gastric carcinoma. PATIENTS AND METHODS: The frequency of HER-2/neu and Topoisomerase IIalpha gene amplification was studied in adenocarcinomas of the stomach (n=131) and the gastroesophageal junction (n=100) by chromogenic in situ hybridization (CISH). Sensitivity of a gastric cancer cell line N87 with HER-2/neu amplification to trastuzumab was studied by a cell viability assay and compared with that of a HER-2 amplified breast cancer cell line SKBR-3. Growth inhibition of N87 cells was also verified in vivo in N87 xenograft tumors. RESULTS: HER-2/neu amplification was present in 16 (12.2%) of the 131 gastric and in 24 (24.0%) of the 100 gastroesophageal adenocarcinomas. Co-amplification of Topoisomerase IIalpha was present in the majority of gastric (63%) and esophagogastric junction cancers (68%) with HER-2/neu amplification. HER-2/neu amplification was more common in the intestinal histologic type of gastric cancer (21.5%) than in the diffuse (2%) or the mixed/anaplastic type (5%, P=0.0051), but it was not associated with gender, age at diagnosis or clinical stage. Presence of HER-2/neu amplification was associated with poor carcinoma-specific survival (P=0.0089). HER-2/neu targeting antibody trastuzumab inhibited the growth of a p185(HER-2/neu) overexpressing gastric and breast carcinoma cell lines (N87 and SKBR-3) with equal efficacy. CONCLUSIONS: HER-2/neu amplification is common in the intestinal type of gastric carcinoma, and it is associated with a poor outcome. HER-2 might be a useful target in this disease, and this hypothesis deserves to be investigated in clinical trials.

Erbb4 and its isoforms: selective regulation of growth factor responses by naturally occurring receptor variants.

ErbB4 is a member of the epidermal growth factor receptor (EGFR, ErbB) family that mediates responses to neuregulins and other EGF-like growth factors. ErbB4 is a central regulator of cardiovascular and neural development as well as differentiation of the mammary gland. A role for ErbB4 has also been implicated in malignancies and heart diseases. Four structurally and functionally distinct ErbB4 isoforms have recently been identified. One pair of isoforms differs within their extracellular juxtamembrane domains. These juxtamembrane ErbB4 isoforms are either susceptible or resistant to proteolytic processing that release a soluble receptor ectodomain. Another pair of ErbB4 isoforms differs within their cytoplasmic tails. Analysis of the intracellular signal transduction pathways indicates that both cytoplasmic ErbB4 isoforms can couple to the Shc-MAPK signaling pathway, while the other one is incapable of coupling to the phosphoinositide 3-kinase (PI3-K)-Akt pathway. The differences in the activation of signaling cascades are reflected in the cellular responses stimulated via the cytoplasmic isoforms. Both cytoplasmic ErbB4 isoforms can stimulate proliferation, but the isoform that cannot activate PI3-K is defective in stimulating cellular survival and chemotaxis. Together these four naturally occurring receptor variants provide a new level of diversity to the control of growth factor-stimulated cellular responses. Thus, the ErbB4 isoforms may have distinct and specific roles in the regulation of various developmental and pathological processes.