Analysis of the epidermal growth factor receptor specific transcriptome: Effect of receptor expression level and an activating mutation

Abstract

Overexpression or expression of activating mutations of the epidermal growth factor receptor (EGFR) is common in cancer and correlates with neoplastic progression. The present study employed Affymetrix oligonucleotide arrays to profile genes induced by ligand-activated EGFR with the receptor either moderately expressed or overexpressed at an in-itself transforming level. These changes were compared to those induced by the naturally occurring constitutively active variant EGFRvIII. This study provides novel insight on the activities and mechanisms of EGFRvIII and EGFR mediated transformation, as genes encoding proteins with functions in promoting cell proliferation, invasion, antiapoptosis, and angiogenesis featured prominently in the EGFRvIII- and EGFR-expressing cells. Surprisingly, it was found that ligand-activated EGFR induced the expression of a large group of genes known to be inducible by interferons. Expression of this module was absent in the EGFRvIII-expressing cell line and the parental cell line. Treatment with the specific EGFR inhibitor AG1478 indicated that the regulations were primary, receptor-mediated events. Furthermore, activation of this module correlated with activation of STAT1 and STAT3. The results thus demonstrate that ligand-activated EGFR at different expression levels results in different kinetics of signaling and induction of gene expression. In addition, the constitutively active variant EGFRvIII seems to activate only a subset of signal pathways and induce a subset of genes as compared to the ligand-activated EGFR.

New pattern of EGFR amplification in glioblastoma and the relationship of gene copy number with gene expression profile

“…The EGFR gene has been found to be expressed at a significantly higher level in glioblastomas. 8,39 The increase in mRNA level caused by amplification is not always proportional to the number of gene copies; 33 and the effects of the gene copy number on expression levels were more relevant for high-level amplifications in a gene-by-gene analysis; results that were also found in breast and prostate cancers. 40,41 In our series, only the cases with dmin amplification, present in more than 10% of the cells, showed an increase of RNA expression.…”

Activation of the EGFR Gene Target EphA2 Inhibits Epidermal Growth Factor–Induced Cancer Cell Motility

“…Recently, we have investigated changes in the transcriptome induced by ligand activation of EGFR or the constitutively active mutant EGFRvIII in mouse fibroblast cell lines expressing either wild-type EGFR (NR6wtEGFR) or EGFRvIII (NR6M) using Affymetrix oligonucleotide arrays (9). One of the genes, whose expression was found to be induced by ligandactivated EGFR and by EGFRvIII, encodes the tyrosine kinase receptor EphA2.…”

“…In correlation, Guo et al (47) recently reported that EphA2 has tumor suppressive functions in mammalian skin and suggested that EphA2 overexpression in tumors is the result of a compensatory feedback defensive mechanism against malignant transformation. In addition, Pedersen et al have shown that activated EGFR induces transcription of a panel of genes (IFN-g responsive genes) whose products have known inhibitory effects on EGFR activity and function, indicative of a negative feedback mechanism abrogating or limiting the tumor-promoting effects of overactivated EGFR (9,48). Furthermore, Macrae et al (35) recently showed that RAF activation stimulates EphA2 expression and that ligand-stimulated EphA2 attenuates activation of the mitogen-activated protein kinase pathway thereby forming a negative feedback loop.…”

“…The cell lines NR6, NR6wtEGFR, and NR6M have previously been described (9). The human epidermoid carcinoma cell line A431 was obtained from the American Type Culture Collection and the head and neck carcinoma cell line HN5 was kindly provided by Dr. Jiri Bartek (Department of Cell Cycle and Cancer, Danish Cancer Society, Copenhagen, Denmark).…”

“…In a global search for EGFR and EGFRvIII regulated genes, we recently found the mRNA level of the receptor tyrosine kinase EphA2 to be up-regulated by ligand-activated EGFR and the constitutively active variant EGFRvIII (9).…”