Tumor-Specific Antigens on Rat Liver Cells Transformed In Vitro by Chemical Carcinogens

Abstract

With the use of membrane immunofluorescence and xenogeneic antisera, tumor-specific membrane antigens were detected on rat epithelial-like liver cells transformed in vitro by chemical carcinogens. These antigens were not detected in 10-, 15-, and 19-day rat fetuses. Xenogeneic antisera were produced in rabbits by immunization of the rabbits with cultivated BD rat liver cells transformed by dimethylnitrosamine or N-methyl-N'-nitro-N-nitrosoguanidine. The specific antisera against tumor-associated antigen(s) were obtained by in vivo absorption in syngeneic male rats and by in vitro absorption with various cell lines. One tumor-specific individual antigen and two tumor-specific cross-reacting antigens were shown to be present on the surface of chemically and/or spontaneously transformed rat liver cell lines. They were not detected on liver and spleen cells of normal BD adult rats, on fetal liver cells, or on liver and intestinal carcinoma cells of Wistar rats. Sera from multiparous pregnant rats had no antibodies against these tumor antigens (although they reacted with fetal cells).

Surface antigens of rat liver epithelial cells grown in medium containing foetal bovine serum

“…In the present study the strong reactivity was due to immunization of the antiserum donors with cells bearing surface FCS components which were too strongly bound to be removed by washing. The common antigens observed in earlier studies on carcinogentreated or transformed liver cells (Jype et al, 1973;Yokota et al, 1978) could also be due to adsorbed FCS. Yokota et al (1978) showed no loss of antibody following absorption of antiserum with 20% by volume of FCS, but this procedure was completely inadequate in our studies where two consecutive absorptions with 3-fold volumes of glutaraldehyde-cross-linked FCS were necessary to effect antibody removal.…”

“…The common antigens observed in earlier studies on carcinogentreated or transformed liver cells (Jype et al, 1973;Yokota et al, 1978) could also be due to adsorbed FCS. Yokota et al (1978) showed no loss of antibody following absorption of antiserum with 20% by volume of FCS, but this procedure was completely inadequate in our studies where two consecutive absorptions with 3-fold volumes of glutaraldehyde-cross-linked FCS were necessary to effect antibody removal. In view of the propensity of rat liver cells to incorporate heterologous serum proteins on the cell surface, it is suggested that any future immunological studies on carcinogen-treated cultured liver cells will either have to be carried out in vivo, or new culture methods will have to be devised.…”

“…This antigenic change was different in specificity from those detected in different clones of transformed fibroblasts, and was observed in cells which had not undergone malignant transformation. Similar antigens have been detected on chemically transformed rat liver cells using absorbed rabbit antisera (Yokota et al, 1978). In the present study, we have further investigated the nature ofthese neoantigen(s) to find out whether they are the resultant of cell culture conditions (and therefore trivial and unrelated to the in vivo situation) or related to some ofthe early changes in hepatocarcinogenesis in vivo.…”