Tumorigenic conversion of NIH 3T3 cells by transfection with Shope fibroma virus DNA

The properties of NIH 3T3 cells transfected with Shope fibroma virus (SFV) DNA were investigated. Six focus-derived cell lines were established that display the following properties: a) They all contained SFV DNA sequences at early passages, b) five of them also expressed SFV RNA at early passages and induced tumors in nude mice, and c) four lines were anchorage independent. Transfection with cloned DNA fragments containing terminal sequences did not induce foci, except with fragment C, which contains the growth-factor gene. However, these transfected cells failed to cause tumors, suggesting that the growth factor alone may not be responsible for tumorigenesis.