Gene Expression Indices in Chemoresistant Lung Cancer

James C. Willey
Medical College of Ohio

Abstract:

Non-small cell lung cancer (NSCLC) is one of the most common causes of cancer death in this country and it is poorly responsive to current chemotherapeutic regimens with an overall regression rate of only 30-50 percent. Histological categorization provides extremely limited information regarding biological behavior of a particular NSCLC tissue. Progress in the genome project and advances in high throughput measurement of gene expression are providing the opportunity to re-define diagnosis of NSCLC tissues on the basis of important phenotypes, such as chemoresistance, rather than on the basis of histology. The primary long-term objectives of the proposed investigation are to improve mechanistic understanding of NSCLC chemoresistance and to develop a method for predicting which NSCLC tumors will respond. The mechanisms of resistance likely to involve multiple gene products. For example, in other studies it was determined that indices comprising multiple independent gene expressions values measured in bronchial epithelial cells correlated better than individual gene expression values when phenotypes for malignancy (c-myc x E2F-1/p21) and risk for lung cancer (GSTP1 x mGST x GSHPx). In preliminary studies, the H1435 non-small cell lung cancer (NSCLC) cell line is 50-fold more resistant to carboplatin than H460. Evaluation of 20 genes putatively associated with carboplatin chemoresistance using standardized mixtures of competitive templates in quantitative RT-PCR revealed that glutathione transferase (GST) p1, Bax alpha, GADD45, ERCC3, glutathione peroxidase and mGST genes are expressed at 100, 20, 10, 6, 5, and 4-fold higher levels respectively in H1435. These genes and other putative chemoresistance genes may be effectively combined into gene expression indices to produce a better marker for the chemoresistant phenotype. The over-all hypothesis of this proposal is that patterns of individual gene expression and/or indices comprising the expression values of multiple individual genes will provide an effective marker for chemoresistant NSCLC tumors. A National Cooperative Tumor Signature Group has assembled to test the hypothesis through completion of the following specific aims. AIM 1) Measure expression of putative chemoresistant genes in primary NSCLC tumor tissues then identify which, if any, correlate with resistant phenotype. AIM 2) Identify gene expression indices that correlate with NSCLC tumor chemoresistance AIM 3) Develop a standardized mixture of competitive templates that will allow inter-laboratory comparison of gene expression data. AIM 4) Automate the quantitative RT-PCR method. AIM 5) Develop an internet based databank for storage of the data acquired during this study and for storage of data acquired by other laboratories.