Classification of small cell lung cancer and pulmonary carcinoid by gene expression profiles

Small cell lung cancer is a common type of lung cancer that is generally cl assified within the spectrum of neuroendocrine lung neoplasms. Using high-d ensity cDNA arrays, we profiled gene expression of small cell lung cancers and compared these expression profiles to those of normal bronchial epithel ial cells and pulmonary carcinoids, which are classified as benign neuroend ocrine tumors. We found the overall expression profiles of two small cell l ung cancer cell lines, two microdissected tissue samples of primary small c ell lung cancer, and cultured bronchial epithelial cells to be relatively s imilar to one another, with an average Pearson correlation coefficient for these comparisons of 0.63. However, we found the expression profiles of sma ll cell lung cancers land bronchial epithelial cells) to be surprisingly di ssimilar to those of two samples of pulmonary carcinoid tumors, with an ave rage correlation coefficient for these comparisons of 0.20. We then compare d the pulmonary carcinoid expression profiles to those of two samples of in filtrating astrocytic brain cancers (oligodendroglioma and high-grade astro cytoma) and found similarity of gene expression among these four samples (a verage correlation coefficient, 0.57). These gene expression profiles sugge st that small cell lung cancers are closely related to land possibly derive d from) epithelial cells, and that pulmonary carcinoids are related to neur al crest-derived brain tumors. More generally, our results suggest that bro ad profiles of gene expression may reveal similarities and differences betw een tumors that are not apparent by traditional morphological criteria.