Identifying specific molecular markers and developing sensitive detection methods are two of the fundamental requirements for detection and differential diagnosis of cancer. Toward this goal, we first performed cDNA array analysis using 65 non-small cell lung cancer and non-involved normal lung tissues. We then used several complementary statistical and analytical methods to examine gene expression profiles generated by us and others from four independent sets of normal and neoplastic lung tissues. We report here that several sets of roughly 20 genes were sufficient to provide a robust distinction between normal and neoplastic tissues of the lung. Next we assessed the predictive ability of these gene sets by using Flow-Thru Chips® (FTC) (MetriGenix, Baltimore, MD) containing 20 genes to screen 48 primary lung tumours and normal lung tissues. Gene expression changes detected by FTC distinguished lung cancers from the normal lung tissues by using an RNA amount equivalent to that present in as few as 300 cells. We also used an independent set of 24 genes and showed that their expression profile was equally effective when measured by quantitative polymerase chain reaction (Q-PCR). Our results demonstrate that lung cancers can be identified based on the expression patterns of just 20 genes and that this approach is applicable for cancer diagnosis, prognosis, and monitoring using small amount of tumor or biopsy samples. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. In lung cancer, several gene expression profiling-based studies involving normal and neoplastic lung tissue have shown that 1) gene expression profiles are distinct for different types of lung cancer and normal tissue [9][10][11]; 2) the set of genes associated with a tumour type reflects the biological basis of the cancer and provide a molecular signature for the disease [10,12]; and 3) gene expression profile could provide prognostic as well as predictive value about the cancer subtype or metastatic potential [13,14]. However, because of the varied platforms and the different types of tissues used for each analysis, addressing the robustness of these predictive gene sets and estimating the minimum number of genes necessary in such sets to accomplish these goals has been difficult.
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ConflictIn this study, we first identified the minimum number of genes sufficient to distinguish lung tumours from adjacent normal lung tissue by using independent training and testing sample sets. We then confirmed the robust nature of such distinction in another set of training and testing samples. We show that one ca...