Amplification of the c-myc oncogene in a subpopulation of human small cell lung cancer.

We have examined a panel of human lung cancer cell lines for amplification and expression of the c-myc, N-myc, and c-myb oncogenes. The cell lines analyzed represent various histopathological types of lung cancer: small cell carcinoma with neuroendocrine properties; squamous cell carcinoma with epithelial markers; and large cell carcinoma with a mixed neuroendocrine-epithelial phenotype. Two of six cell lines, both of which were small cell carcinomas, showed about a 20-fold amplification of the c-myc oncogene. In both cell lines, the amplification is accompanied by an enhanced expression of c-myc. The N-myc or c-myb genes were not amplified in any of the cell lines, nor were they expressed in detectable amounts. The results confirm and extend earlier findings on c-myc amplification in small cell lung cancer.