Abundant messenger RNA sequences common to transplanted mouse tumours of different tissue origins

Radioactive cDNA, cell-free-synthesised on poly(A)-rich mRNAs from mouse FLS-ascites tumour cells, were separated into two fractions corresponding to abundant mRNA species and to rare mRNA species respectively, the former being nearly 100-times more abundant per cell than the latter. Aliquots of each fraction were hybridized to a large excess of RNA of different origins; three ascites tumours (the FLS, Krebs 2 and Ehrlich tumours) all transplanted in animals; one established line of Friend erythroleukemia cells serially passaged in culture; adult organs and whole mouse embryos. It was shown that all or nearly all the mRNA species, in particular the abundant ones, were present and similarly distributed in the three transplanted tumour strains studied, despite their different tissue origins. The great majority of abundant mRNA species were also present in Friend erythroleukemia cells but about two-times less frequent relative to transplanted tumours. Much greater differences were found as compared with non-malignant cells. In particular, although the majority of the abundant mRNA species were also found in all normal tissues studied, they were on the average 7-8-times less abundant in adult liver or in 10-days-old embryos, and 10-times less abundant in adult brain, than in tumour cells. Finally about 10% of the abundant RNA species common to all transplanted tumours appeared to be absent in normal cells, whatever their growth rates or stage of differentiation. The possible implications of these findings are discussed.