Changes in cellular DNA sequence adjacent to integrated viral genome in transplantable and nontransplantable guinea pig cells transformed by SV40

Guinea pig (strain No13) kidney cells were transformed with SV40 (SVNo13). When this transformant was injected subcutaneously into syngeneic irradiated guinea pigs, tumors were produced in some animals. One of them became transplantable (ST13). Clones were obtained from cultured tumor cells (STC13). About one copy of the viral genome appeared to exist in both SVNo13 and STC13 clones as determined by reassociation kinetics. We have examined the distribution of integrated viral sequences in the host DNA by blot hybridization. In SVNo13, the blotting pattern with BamHI showed two main bands of 6.9 and 4.3 kilobases (kb), whereas in STC13 clones the 6.9-kb band was replaced with a shorter one of 6.1-kb. The blotting pattern with EcoRI also showed distinct changes between SVNo13 and STC13 clones. These results suggest either the occurrence of some mutations or deletions in the cellular DNA adjacent to the integrated viral genome or the transposition of viral DNA sequences during tumor development.