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

Abstract

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 speifically 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 holoEGFRs were phosphorylated on tyrosine residues only after exposure of the cells to liand, de 2-7 EGFRs were constitutively phosphorylated. In tissue culture neither addition ofEGF 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 oftumor cells with their microenvironment in ways not easily assayed in vitro.

Epidermal growth factor receptor mutation type iii transfected into a small cell lung cancer cell line is predominantly localized at the cell surface and enhances the malignant phenotype

“…In all cases the cell lines exhibiting the EGFRvIII had an increased growth potential or ability to form tumors in the nude mouse model. 22,25,27,30,44 The in vitro invasion assay can mimic some of the events leading to the formation of metastasis, that is, attachment to the basement membrane, local proteolysis and migration. Various growth factors have been implied to play a significant role in the processes leading up to the formation of metastasis.…”

“…Another study has demonstrated that the EGFRvIII could be detected at the cell surface. 30 In the present study, we report our results from the expression of EGFRvIII in an EGFR-negative small cell lung cancer (SCLC) cell line. We used the Tet-On expression system and evaluated the expression of EGFRvIII in the absence and presence of doxycycline.…”

Relationship of p215BRCA1 to tyrosine kinase signaling pathways and the cell cycle in normal and transformed cells

“…Results were also separately con®rmed using scanning densitometry. In U87MG cells, the EGFr is overexpressed and appears to mediate the transformed phenotype (Libermann et al, 1985;Nishikawa et al, 1994). In U87/T691 cells, the T691stop mutant proteins heterodimerize with the EGF receptor, suppressing transformation characteristics of these tumor cells (O'Rourke et al, 1997).…”

EGFRvIII undergoes activation-dependent downregulation mediated by the Cbl proteins

“…The ectopic expression of the EGFRvIII in a glioblastoma cell line increased the speed with which these cells formed tumors in nude mice (Nishikawa et al, 1994;Nagane et al, 1996). The EGFRvIII is also capable of significantly enhancing the tumorgenicity of immortalized murine fibroblasts Moscatello et al, 1996) and the breast cancer cell line MCF-7 (Tang et al, 2000).…”

“…Using the murine hematopoietic 32D cell line, Tang et al (2000) demonstrated that the EGFRvIII is capable of directly transforming a non-tumorigenic cell line. Unlike the wild-type (WT) EGFR, the EGFRvIII is unable to bind to EGF or transforming growth factor-α (Ekstrand et al, 1994;Nishikawa et al, 1994;Moscatello et al, 1996) but, instead, it can dimerize spontaneously (Moscatello et al, 1996;Fernandes et al, 2001;Montgomery, 2002). The spontaneous dimerization and ensuing TK activation of the EGFRvIII is necessary to transform cells (Han et al, 1996;Nagane et al, 1996;Huang et al, 1997;Antonyak et al, 1998;O'Rourke et al, 1998;Montgomery, 2002;Johns et al, 2003;Abulrob et al, 2004;Luwor et al, 2004;Pedersen et al, 2004).…”