Increase of AKR-specific sequences in tumor tissues of leukemic AKR mice.

AKR mice produce, from shortly after birth, high titers of their endogenous Gross type murine leukemia virus, and develop a thymus-derived leukemia at 7-9 months of age. We show that this oncogenesis is accompanied by an increase in the number of AKR-specific DNA sequences in the tumor tissues, whereas the "non-target" organs are not affected. Sequence increase was determined by kinetic analysis of DNA reassociation using an AKR-murine leukemia virus (MuLV)-specific cDNA and also by hybridization with excess AKR cDNA. The AKR cDNA was selected to recognize AKR sequences without significant crossreaction with DNA sequences of other endogenous viruses. The results show that during the development of the leukemia, the number of AKR-MuLV-specific genes increases in tumor tissues by a factor of 1 1/2 to 2.