Carcinogenicity of Aflatoxin B1 in Rhesus Monkeys: Two Additional Cases of Primary Liver Cancer2

Abstract

Three of 42 (7%) monkeys given aflatoxin B₁ (AFB₁) for longer than 2 years have developed primary malignant neoplasms of the liver. Liver biopsies performed at intervals during aflatoxin administration revealed that neoplasia was preceded by pathologic lesions of the liver, including toxic hepatitis, proliferation of pseudotubules, and hyperplastic nodules. Serum α-feto-protein levels, monitored in one of the monkeys by radioimmunoassay, paralleled tumor growth and recurrence of the hepatocellular carcinoma. Normal serum α-fetoprotein levels were noted for a monkey with hemangioendothelial sarcoma. Our results implicate AFB₁ as a liver carcinogen in monkeys and add additional support to the hypothesis that humans exposed to this substance may be at risk of developing liver cancer.