ABSTRACT
Proteins are responsible for biological systems to function and are favored targets for therapy. Application of cDNA microarrays to cancer aimed to generate new molecularbased classifications of disease and to identify new biomarkers of disease based on gene expression profiles. Preliminary results from these studies have confirmed the existence of gene expression profiles that correlate with lung cancer histopathology and clinical outcome and some aspects of biology.1-5 Most studies have examined pathologically homogeneous sets of tumors to identify occult clinically relevant subtypes, pathologically distinct subtypes of tumors to identify molecular correlates. Studies using DNA microarrays in breast cancer have identified potential new classifications with striking molecular differences,6-9 including powerful predictors of disease outcome.10 Studies in lung cancer are less advanced, but have identified potentially important subgroups of lung adenocarcinoma.1,11
Comparisons of messenger RNA and protein levels for the same tumors reported for lung cancer demonstrated that only a small percentage of genes had a statistically significant correlation between the levels of their corresponding proteins and mRNAs;12 thus the overall correlation between level of expression of the transcriptome and protein expression is relatively poor. This may not be entirely surprising and underscores the potential importance of proteomic analysis.
