Project proposal

Bruce Montgomery, M.D.
Joseph Testa, Ph.D.
Eric Vallieres, M.D.
Howard West, M.D.

Hypothesis

Mutant forms of the epidermal growth factor receptor are important components of the oncogenic growth and proliferation of mesothelioma and are relevant targets in the treatment of patients with this disease.

Background

The epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor which is an integral part of signaling pathways which control normal and malignant cell growth. The EGFR is overexpressed in a broad variety of epithelial malignancies, including lung cancer, ovarian cancer, breast cancer and central nervous system tumors. Overexpression of EGFR in the presence of ligands such as EGF or TGF- a results in constitutive activation of the receptor and transforms these cells, demonstrating the potential role of EGFR in the development of human cancer. There are naturally occurring mutations of the EGFR which result in constitutive activation of the receptor in the absence of any ligands. The most common form, the EGFRvIII, is expressed in brain tumors, lung, ovarian and prostate cancers and not in any other normal human tissues. Because EGFRvIII is a classical oncogene, it has been postulated that blocking its activity either with tyrosine kinase inhibitors which have been designed to block EGFR function, or by generating immunity against the EGFRvIII through vaccination, might be effective means of treating malignancies which express EGFRvIII.

We have recently characterized the expression patterns of EGFRvIII in 50 epithelial ovarian cancers. As part of that study, which documented EGFRvIII expression using immunohistochemistry and polymerase chain reaction (PCR), two peritoneal mesotheliomas were included as controls. Both specimens were positive for high level EGFRvIII expression by immunohistochemistry, and the sample for which cDNA was available demonstrated positivity by PCR, confirming the presence of mRNA for EGFRvIII. These data suggest that EGFRvIII is expressed in mesothelioma, either peritoneal or pleural. Peritoneal and pleural mesothelioma are both caused by asbestos exposure and exhibit similar clinical behavior, suggesting that the same pathways are responsible for cancer development and maintenance. Because small molecule inhibitors of the EGFR such as Iressa and Tarceva are available for clinical study, there is significant potential for studies utilizing these agents as primary or adjuvant therapy of mesothelioma. Immunotherapeutic approaches to targeting EGFRvIII are also in early phase studies, and we are currently studying the utility of a peptide vaccine to EGFRvIII in a Southwest Oncology Group study (SWOG 0114) as a means of increasing patients' immunity to this receptor. Effective endogenous immunity in patients in the form of antibodies or T cells specific to the receptor might be an effective means of preventing relapse of EGFRvIII expressing cancers. This approach could clearly be extended to the treatment of mesothelioma in clinical trials.

Research design and methods

1. To determine the frequency of EGFRvIII expression in pleural and peritoneal mesothelioma using PCR with DNA sequencing, and immunohistochemistry.

2. To assess the efficacy of the small molecule inhibitors of EGFR in the treatment of human mesothelioma in a xenograft model.

1. Polymerase chain reaction (PCR) assay will be carried out on snap frozen human mesothelioma tumors to determine the presence of absence of mRNA for EGFRvIII. At present we have 16 tumor specimens procured to perform these analyses. PCR products of any weight other than that corresponding to wild type EGFR will be cloned and sequenced to determine if they originate from EGFRvIII or other EGFR mutants. Additional tumor specimens will be procured to determine the expression patterns in at least 50 primary mesotheliomas and we will correlate the expression of EGFRvIII with survival in these patients. These studies will be carried out with Institutional Review Board approval of the University of Washington, Fox Chase Cancer Center and Swedish Cancer Institute.

2. Human xenograft models of mesothelioma are readily available, including the H2373, JMN, and ZL5 xenografts. These human mesothelioma xenografts will be grown in Balb/c nu/nu immunodeficient mice and used as preclinical models for human mesothelioma. The therapeutic efficacy of the EGFR specific tyrosine kinase inhibitor Iressa, and the EGFR specific monoclonal antibody Erbitux with and without pemetrexed will be tested in these xenograft models.

Implications of this work

If EGFRvIII is demonstrated to be a relevant target in mesothelioma, it opens up the potential to use EGFR specific tyrosine kinases and EGFR specific monoclonal antibodies as clinical agents in the primary and adjuvant treatment of a disease for which effective therapy has been very limited. It will also raise the potential for the use of EGFRvIII peptide and other EGFR targeting vaccines as means of strengthening patients' own immune responses against their tumors, clearly a very attractive and potentially important therapeutic intervention. These studies, if successful would directly lead to clinical trials incorporating these agents into the treatment of patients with mesothelioma.

References;

1. Montgomery, R. B., Moscatello, D. K., et al. (1995) J Biol Chem 270, 30562-30566
2. Montgomery, R. B., Guzman, J., et al. (2000) J Biol Chem 275, 17358-17363
3. Moscatello, D. K., Holgado-Madruga, M., et al. (1995) Cancer Res 55, 5536-5539
4. Moscatello, D. K., Montgomery, R. B., et al. (1996) Oncogene 13, 85-96
5 Moscatello, D. K., Holgado-Madruga, M., et al. (1998) J Biol Chem 273, 200-206
6. www.swog.org - trial # 0114

*** POSTED JUNE 1, 2004 ***