A study of myc-related gene expression in small cell lung cancer by in situ hybridization

The expression of myc-related genes (c-myc, N-myc, and L-myc) in small cell lung cancer (SCLC) was studied by RNA-RNA tissue in situ hybridization. The tissues investigated included cytospins of ten cell lines derived from patients with SCLC, four corresponding nude mouse xenografts from cell lines, and metastatic tumor tissue obtained by surgical biopsy and at autopsy. The probes were prepared as ³⁵S labeled complementary RNA. The expression of each gene was demonstrated specifically by autoradiography in the cytoplasm of the neoplastic cell samples. The average levels of oncogene expression in each specimen corroborated previous data obtained by Northern blot assays. In addition, heterogeneity in gene expression from cell to cell in each sample was noted. This study represents the first attempt to demonstrate oncogene expression in lung cncer cell lines and tissues in situ, and confirms that the expression of these myc related genes can be seen in the primary tumor. The technique of RNA-RNA tissue in situ hybridization has great potential in answering fundamental questions of tumor cell heterogeneity and progression in SCLC. It should be useful in both prospective and retrospective studies.