In vitro colonization ability appears soon after initiation of hepatocarcinogenesis in the rat.

Hepatocytes were isolated from rat livers at various intervals after initiating hepatocarcinogenesis by a single administration of methyl(acetoxymethyl)nitrosamine after a partial hepatectomy. Proliferative hepatocyte colonies were regularly observed in primary cultures derived from initiated livers when these cultures were incubated in medium containing the liver tumor promoter, phenobarbital. Fewer colonies generally were observed in initiated cell cultures that were incubated without phenobarbital and in phenobarbital-induced cultures derived from non-initiated control livers. Because in vitro proliferative activity is a characteristic of malignant hepatocytes these results suggest that the feature of in vitro colonization may characterize a population of carcinogen-altered hepatocytes.