Liver tumor promoters stimulate growth of transplanted hepatocellular carcinomas

Cell suspensions or tissue fragments from primary hepatocellular carcinomas and benign neoplastic nodules, induced by treating rats with chemical carcinogens, were transplanted by intraportal injection or subcapsular implantation in the livers of syngeneic host rats. Both nodule and carcinoma transplants produced high numbers of hepatocellular carcinomas in the hosts 2 to 5 mo after transplantation. Treatment of the host rats with liver tumor promoters (phenobarbital or 2-acetylaminofluorene) greatly stimulated tumor outgrowth, demonstrating that even established carcinoma cells can be promoter-sensitive. Tumor outgrowth was also stimulated by partial hepatectomy of the hosts, the regenerative stimulus interacting synergistically with the tumor promoters.