Grantee Research Project Results

The Role of NF2 in the Development of Mesothelioma

EPA Grant Number: F07D90213
Title: The Role of NF2 in the Development of Mesothelioma
Investigators: Erbe, Amy
Institution: University of Montana
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2007 through September 1, 2009
RFA: GRO Fellowships for Graduate Environmental Study (2007) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Human Health , Fellowship - Toxicology , Fellowship - Health Effects

Objective:

Mesothelioma is an aggressive cancer shown to have an undeniable link to asbestos exposure. While much is known of the initial host response to asbestos inhalation, the molecular mechanisms that lead to the development of the tumors is not well understood. Therefore, it becomes essential to better understand molecular mechanisms involved in the development of these tumors so that more effective therapies can be developed.

The p53 tumor suppressor gene functions as a guardian of the genome, responsible for the integrity of many cell cycle checkpoints and processes. p53 is mutated in about 50% of cancers, however this number may underestimate the actual incidence of p53 inactivation. Another possible explanation for p53 disparity can be through the p53 negative regulator, MDM2. There is evidence to suggest that NF2 (merlin) may play a role in degrading MDM2, thus the loss of NF2 could contribute to tumor progression by allowing MDM2 to remain active indirectly promoting p53 degradation. NF2 has been shown to have a high mutation rate in malignant mesotheliomas, resulting in improper function of the gene. This project will investigate the role the tumor suppressor gene NF2 plays in the development of mesothelioma. Whether inactivation of NF2 in human tumors plays a critical role in abrogating the function of p53 or if it has other roles in releasing cells from normal growth control will be directly assessed.

Approach:

To investigate the downstream effects of improper function of NF2, shRNA will be used to suppress function of the gene in normal mesothelial cell lines. In addition to investigating loss of NF2 in a mesothelial cell line, NF2 will be added back into a cell line that has a mutated NF2 gene. Microarray, genomic, and phenotypic analyses will be used to assess changes in cells. In order to analyze p53 response, cells will be subjected to DNA damage by UV exposure. The role of NF2 in an in vivo model of pleural mesothelioma development will be examined following intratracheal injections of crocidolite asbestos, Libby six-mix asbestos, or PBS control. Using a heterozygous NF2 knockout mouse model, early events in pleural mesothelioma tumor development during robust and predictable tumor induction can be assessed. Phenotype and gene expression changes will be monitored.

Expected Results:

Suppression of NF2 protein expression in normal cells will prevent normal p53 expression and/or function, resulting in a more transformed and possibly tumorigenic phenotype. Replacement of NF2 in mesothelioma tumor cell model will restore p53 function, and some aspects of normal cellular behavior. Both approaches, shRNA and re-expression, will provide new insights into compensatory mechanisms, the absolute requirement for NF2 function, and downstream genes affected due to the presence or absence of NF2. Mice lacking a full complement of NF2 genes will develop tumors at earlier times and in a larger percentage of animals than in control animals. These studies will provide an explanation for the loss of p53 function and the role of asbestos exposure in human mesothelioma. Understanding of the genetic mechanisms of tumor progression will be increased, and it is therefore possible that this will help provide a method for earlier detection of malignant mesothelioma.

Supplemental Keywords:

Mesothelioma, NF2, merlin, MDM2, p53, tumor suppressor, cancer, toxicology, asbestos, gene expression, microarray, molecular biology, animal models, shRNA,

Progress and Final Reports:

2008

Final