In Vitro Alpha-Fetoprotein Synthesis by Monkey Hepatocellular Carcinoma

Abstract

Five monkeys were treated ip with N-nitrosodlethylamlne (DENA), and one was treated with 1-nitrosopiperidine (PIP), starting within 2 months of birth, until hepatocellular carcinoma (HCC) developed. All animals except the PIP-treated monkey had much elevated serum α-fetoprotein (AFP) values. Fresh, minced, biopsy-derived tumor was cultured with l-[¹⁴C]leucine and l-[¹⁴C]lysine. Synthesis of AFP was determined by radioimmunoassay and by specifically precipitable [¹⁴C]AFP. Good agreement between these two parameters was obtained for the 4 DENA-induced tumors synthesizing AFP in culture. Tumor from 1 DENA-treated monkey did not synthesize AFP. In addition, neither normal liver nor tumor from the PIP-treated monkey showed AFP synthesis. Rates of synthesis were 0.37-5.50 ng AFP/mg tumor/day, or 0.0012-0.0183 pg AFP/cell/day (if one assumes 3.0×10⁵ cells/mg tissue) over 48 or 72 hours. Different nodules from the same animal had similar rates of synthesis. For tumors that synthesized AFP in culture, a positive correlation was generally found between rate of synthesis and serum AFP level. The rate of in vitro AFP synthesis observed was lower than that of immunoglobulin synthesis in human myeloma or of AFP synthesis in a rat HCC, but it was close to the estimated rate of AFP synthesis in a monkey HCC line in long-term culture.