Tumors in the rat after injection of neoplastic and preneoplastic nucleic acids.

Hepatomas occurred in the liver of 5 of 386 ACT rats at the site of injection, 10—16weeks previously, of cells of regenerating liver pre-incubated with I)NA derived from the Morris hepatoma 3924C, transplantable in this strain. A tumor of undetermined nature developed in 1 of 62 rats 6 months after intrahepatic injection of a mixture of preneoplastic liver DNA and RNA. No tumors occurred in 1480 other ACT rats (No. in paren theses) treated as follows : I. intrahepatic injection of regenerating liver cells pre-incubated with (a) hepatoma RNA (340), (b) preneoplastic DNA (124), (c) normal liver DNA (40), and (d) normal liver RNA (40) ; TI. intrahepatic injection of (a) hepatoma DNA (280), (b) hepatoma RNA (246), (c) preneoplastic liver DNA (166), (d) preneoplastic liver RNA (184), (e) normal liver DNA (30), and (f) normal liver RNA (30). The circumstances under which the hepatomas occurred seem to warrant the conclusion that a process of cell transformation by the hepatoma DNA was involved in their pathogenesis.