In vitro demonstration of Mallory body formation in liver cells from rats fed diethylnitrosamine.

Epithelioid liver cells were established in culture from rats sacrificed 10 to 18 weeks after the administration of the hepatocarcinogen diethylnitrosamine in their drinking water. After approximately 3 months in vitro, more than half the cells propagated from rats that developed hepatocellular carcinomas had bean-shaped, acentrically displaced nuclei with large juxtanuclear homogeneous appearing areas resembling the hyalin or Mallory bodies in the livers of chronic alcoholics. These abnormalities were not seen in the livers of origin, but were retained in the carcinomas that formed after the cultured cells containing such juxtanuclear hyalin inclusions were inoculated into young rats or nude (i.e., thymusless) mice; these features persisted upon reestablishment and continuous passage of the tumor cells in culture. The cells were further characterized by their karyotypes and their growth properties in liquid media and soft agar. By transmission electron microscopy the hyaline bodies in the culture tumor cells were shown to consist of a disorganized meshwork of filaments. Examination by incubating cells with cytochalasin B and by using antiactin and anti-DNase antisera as indirect immunofluorescence probes also revealed a disturbance in the cytoskeleton.