The development and neoplastic progression of human astrocytic tumors appears to result through an accumulation of genetic alterations occurring in a relatively defined order. One such alteration is amplification of the epidermal growth factor receptor (EGFR) gene. This episomal amplification occurs in 40-50% of glioblastomas, which also normally express endogenous receptors. Moreover, a significant fraction of amplified genes are rearranged to specifically eliminate a DNA fragment containing exons 2-7 of the gene, resulting in an in-frame deletion of 801 bp of the coding sequence of the extracellular domain. Here we used retroviral transfer of such a mutant receptor (de 2-7 EGFR) into glioblastoma cells expressing normal endogenous receptors to test whether the mutant receptor was able to augment their growth and malignancy. Western blotting analysis showed that these cells expressed endogenous EGFR of 170 kDa as well as the exogenous de 2-7 EGFR of 140-155 kDa. Although holo-EGFRs were phosphorylated on tyrosine residues only after exposure of the cells to ligand, de 2-7 EGFRs were constitutively phosphorylated. In tissue culture neither addition of EGF nor expression of the mutant EGFR affected the rate of cell growth. However, when cells expressing mutant EGFR were implanted into nude mice subcutaneously or intracerebrally, tumorigenic capacity was greatly enhanced. These results suggest that a tumor-specific alteration of the EGFR plays a significant role in tumor progression perhaps by influencing interactions of tumor cells with their microenvironment in ways not easily assayed in vitro.

https://www.pnas.org/content/pnas/91/16/7727.full.pdf

A mutant epidermal growth factor receptor common in human glioma confers enhanced tumorigenicity.

EGF-R positivity was shown to be present in 2500 (48%) of 5232 breast tumors in 40 different series of patients. The mean of the percentages of EGF-R positivity in the individual series reported by these 40 different groups of investigators is 45% (range 14-91%). Overall there are generally no clear differences between results obtained by radioligand binding assays, immunological methods, autoradiography, and measurement of EGF-R transcripts although the mean percentage of EGF-R-positive tumors determined by immunological methods tends to be somewhat lower. Nearly all studies indicate a negative relationship between EGF-R and steroid receptor status (28 of 31 studies for ER, 12/19 for PR) showing that EGF-R positivity is twice as high in ER or PR- negative tumors compared to ER or PR- positive tumors (approximately 50-60% vs. 30%). With regard to other prognostic factors the majority of investigators (10/18) also reported a significant (positive) correlation with tumor grade, but only a minority found a significant relationship between EGF-R status and patient age (2/9), menopausal status (1/7), histological type (3/7), tumor size (2/17), nodal status (5-9/20), ploidy (1/7), or proliferation indices (3/9). No relationship was observed with tumor insulin-like growth factor I receptor, PRL receptor (PRL-R), and LHRH receptor (LHRH-R) status, but an inverse relationship between EGF-R and somatostatin receptor may be present. However, it has to be stressed that the series in which the relationship between EGF-R status and other prognostic factors were investigated, contained relatively few patients (mostly less than 100). Therefore, when larger groups of patients are investigated, more significant relationships may be observed, especially with respect to nodal status, tumor ploidy, and proliferation indices. In fact, we calculated the presence of EGF-R positivity overall in 35% of 253 aneuploid tumors vs. in only 15% of 114 diploid tumors (P less than 0.0001). In addition most studies observed a trend, if no significant correlation, between higher EGF-R levels in tumors with the highest percentages of S-phase or Ki-67 expression. With regard to relapse-free and overall survival, five of nine different groups of investigators showed significant prognostic value of EGF-R after short-term (1- to 4-yr) follow-up, indicating that patients with EGF-R-positive tumors have a poor prognosis. However, three of five groups with a maximal follow-up of at least 6 yr found only a tendency for any relationship between EGF-R status and long-term outcome.

/pdf/the-clinical-significance-of-epidermal-growth-factor-2mq4nythpu.pdf

The Clinical Significance of Epidermal Growth Factor Receptor (EGF-R) in Human Breast Cancer: A Review on 5232 Patients

The enhanced tumorigenic activity of a mutant epidermal growth factor receptor common in human cancers is mediated by threshold levels of constitutive tyrosine phosphorylation and unattenuated signaling.

The HER2 protooncogene encodes a receptor tyrosine kinase, p185HER2. The overexpression of p185HER2 has been associated with a worsened prognosis in certain human cancers. In the present work we have screened a variety of different tumor cell lines for p185HER2 expression using both enzyme-linked immunosorbent and fluorescence-activated cell sorting assays employing murine monoclonal antibodies directed against the extracellular domain of the receptor. Increased levels of p185HER2 were found in breast (5/9), ovarian (1/6), stomach (2/3) and colorectal (5/16) carcinomas, whereas all kidney and submaxillary adenocarcinoma cell lines tested were negative. Some monoclonal antibodies directed against the extracellular domain of p185HER2 inhibited growth in monolayer culture of breast and ovarian tumor cell lines overexpressing p185HER2, but had no effect on the growth of colon or gastric adenocarcinomas expressing increased levels of this receptor. The most potent growth-inhibitory anti-p185HER2 monoclonal antibody in monolayer culture, designated mumAb 4D5 (a murine IgG1κ antibody), was also tested in soft-agar growth assays for activity against p185HER2-overexpressing tumor cell lines of each type, with similar results. In order to increase the spectrum of tumor types potentially susceptible to monoclonal antibody-mediated anti-p185HER2 therapies, to decrease potential immunogenicity issues with the use of murine monoclonal antibodies for human therapy, and to provide the potential for antibody-mediated cytotoxic activity, a mouse/human chimeric 4D5 (chmAb 4D5) and a “humanized” 4D5 (rhu)mAb 4D5 HER2 antibody were constructed. Both engineered antibodies, in combination with human peripheral blood mononuclear cells, elicited antibody-dependent cytotoxic responses in accordance with the level of p185HER2 expression. Since this cytotoxic activity is independent of sensitivity to mumAb 4D5, the engineered monoclonal antibodies expand the potential target population for antibody-mediated therapy of human cancers characterized by the overexpression of p185HER2.

Differential responses of human tumor cell lines to anti-p185HER2 monoclonal antibodies.

The epidermal growth factor (EGF) receptor is activated by both EGF and transforming growth factor-alpha (TGF-alpha). Using immunohistochemical and immunoblotting techniques we now report that the EGF receptor, EGF, and TGF-alpha are found in both pancreatic acini and ducts in the normal human pancreas, and that all three proteins are expressed at higher levels in human pancreatic cancer tissues. Using in situ hybridization techniques, we also report that the mRNA encoding the EGF receptor, EGF, and TGF-alpha colocalize with their respective proteins. Northern blot analysis of total RNA indicates that, by comparison with the normal pancreas, the pancreatic tumors exhibit a 3-, 15-, and 10-fold increase in the mRNA levels encoding the EGF receptor, EGF, and TGF-alpha, respectively. Furthermore, by in situ hybridization, there is a marked increase in these mRNA moieties within the tumor mass. These findings suggest that EGF and TGF-alpha may participate in the regulation of normal pancreatic exocrine function, and that overexpression of the EGF receptor and its two principal ligands may contribute to the pathophysiological processes that occur in human pancreatic cancer.

/pdf/overexpression-of-the-epidermal-growth-factor-receptor-in-2l67zfs1xy.pdf

Overexpression of the epidermal growth factor receptor in human pancreatic cancer is associated with concomitant increases in the levels of epidermal growth factor and transforming growth factor alpha.

We analyzed the epidermal growth factor receptor gene using a complementary DNA probe of the epidermal growth factor receptor gene in 21 uncultured primary breast carcinomas and found that the gene was amplified in three of these tumors. We further demonstrated by immunohistochemistry using a monoclonal antibody to the epidermal growth factor receptor that the receptor protein product of this gene was over-expressed and displayed elevated kinase activity. Our data indicate that one of the molecular mechanisms for overexpression of epidermal growth factor receptor in human breast cancer is epidermal growth factor receptor gene amplification without rearrangement in a subset of tumors.

https://cancerres.aacrjournals.org/content/canres/48/1/161.full.pdf

Jungsil Ro

Papers

Amplified and Overexpressed Epidermal Growth Factor Receptor Gene in Uncultured Primary Human Breast Carcinoma