In a wide variety of neoplasms, proto-oncogenes were found transcriptionally activated by different DNA rearrangements. In the present study we used Namalwa, Wish and C6 cell lines in order to investigate the correlation between gene reorganisations and their expression. According to Southern and fluorescence in situ hybridisation (FISH) analysis the oncogenes c-ras, c-src and c-fos were amplified in Namalwa and Wish cells. reorganisation other than amplification was found for c-mos in the three cell cultures investigated. The amplification levels of the genes studied were assessed by dot blot hybridisation followed by densitometric scanning. c-H-ras and c-src were amplified about 20-fold in the genomes of Namalwa and Wish, while c-fos was amplified approximately 12-fold in the same cell lines. The hybridisation signals in C6 were almost the same as in the control lymphocytes for the four oncogenes investigated. Similar results were obtained for c-mos in the genomes of all cell lines examined. Using RT-PCR, overexpression of proto-oncogenes c-ras, c-src, c-mos and c-fos was found in Namalwa and Wish cells. In C6 cells the expression of the four genes studied was marginal. Overexpression of c-mos was observed in Namalwa and Wish cells, while in C6 it was marginal although existence of reorganisation was found. Hence, it might be suggested that in C6 cells c-mos is down-regulated from other factors and/or genes, or requires for its activation overexpression of other genes.

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