N. Engl. J. Med. 353 (19):2012-2024 November 10, 2005
Molecular Determinants of the Response of Glioblastomas to EGFR Kinase Inhibitors
Ingo K. Mellinghoff, M.D., Maria Y. Wang, M.D., Ph.D., Igor Vivanco, Ph.D., Daphne A. Haas-Kogan, M.D., Shaojun Zhu, M.S., Ederlyn Q. Dia, B.S., Kan V. Lu, Ph.D., Koji Yoshimoto, M.D., Ph.D., Julie H.Y. Huang, B.S., Dennis J. Chute, M.D., Bridget L. Riggs, B.S., Steve Horvath, Ph.D., Linda M. Liau, M.D., Ph.D., Webster K. Cavenee, Ph.D., P. Nagesh Rao, Ph.D., Rameen Beroukhim, M.D., Timothy C. Peck, B.S., Jeffrey C. Lee, B.S., William R. Sellers, M.D., David Stokoe, Ph.D., Michael Prados, M.D., Timothy F. Cloughesy, M.D., Charles L. Sawyers, M.D., and Paul S. Mischel, M.D.
ABSTRACT
Background The epidermal growth factor receptor (EGFR) is frequently amplified, overexpressed, or mutated in glioblastomas, but only 10 to 20 percent of patients have a response to EGFR kinase inhibitors. The mechanism of responsiveness of glioblastomas to these inhibitors is unknown.
Methods We sequenced kinase domains in the EGFR and human EGFR type 2 (Her2/neu) genes and analyzed the expression of EGFR, EGFR deletion mutant variant III (EGFRvIII), and the tumor-suppressor protein PTEN in recurrent malignant gliomas from patients who had received EGFR kinase inhibitors. We determined the molecular correlates of clinical response, validated them in an independent data set, and identified effects of the molecular abnormalities in vitro.
Results Of 49 patients with recurrent malignant glioma who were treated with EGFR kinase inhibitors, 9 had tumor shrinkage of at least 25 percent. Pretreatment tissue was available for molecular analysis from 26 patients, 7 of whom had had a response and 19 of whom had rapid progression during therapy. No mutations in EGFR or Her2/neu kinase domains were detected in the tumors. Coexpression of EGFRvIII and PTEN was significantly associated with a clinical response (P<0.001; odds ratio, 51; 95 percent confidence interval, 4 to 669). These findings were validated in 33 patients who received similar treatment for glioblastoma at a different institution (P=0.001; odds ratio, 40; 95 percent confidence interval, 3 to 468). In vitro, coexpression of EGFRvIII and PTEN sensitized glioblastoma cells to erlotinib.
Conclusions Coexpression of EGFRvIII and PTEN by glioblastoma cells is associated with responsiveness to EGFR kinase inhibitors.
Proc Natl Acad Sci U S A. 1994 Aug 2;91(16):7727-31.
A mutant epidermal growth factor receptor common in human glioma confers enhanced tumorigenicity.
Nishikawa R, Ji XD, Harmon RC, Lazar CS, Gill GN, Cavenee WK, Huang HJ.
Ludwig Institute for Cancer Research, La Jolla, CA 92093-0660.
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. |
