Localization of amplified c-myc and n-myc in small cell lung cancer cell lines

In this study 12 small cell lung cancer cell lines were tested for amplification of myc oncogenes, the location of amplified sequences, and the possible correlation between number of dmin and degree of amplification in dmin-containing lines. C-myc appeared to be amplified in four cell lines, and N-myc amplification was detected in two cell lines. No amplification of L-myc was found. The degree of amplification in the different cell lines varied between 20X and 100X. The cell lines with myc amplification appeared to contain numerous dmin, although in one cell line they occurred in only 10% of the cells. The other cells in this line contained a homogeneously staining region (HSR). In situ hybridization was carried out to find the location of the amplification. In four cell llines the amplified myc genes were found to be located on the dmin. In the cell line with the HSR in most cells and dmin in a minority of its cells, amplification was found both at the HSR and on the dmin. In one cell line the myc sequences seemed to be dispersed through the genome. The ratio between the average number of dmin per cell and the degree of amplification did not vary considerably between the cell lines, with one exception. In that cell line the number of dmin exceeded the number of myc sequences by about one order of magnitude. Apparently, the population of dmin in this cell was heterogeneous and amplified myc genes were only present on a subpopulation.