Expression and thermal stability of simian virus 40 tumor-specific transplantation antigen and tumor antigen in wild type- and tsA mutant-transformed cells

Abstract

Aspects of a suggested relationship between the expression of SV-40 tumor-specific transplantation antigen (TSTA) and tumor antigen (TA) were explored. A unique rat embryo cell line transformed by a temperature-sensitive A mutant that loses TA during exposure to the nonpermissive temperature (A28-RE) lost TSTA. A typical control tsA-transformed cell line (A239-MB) [mouse brain] expressed TA and TSTA at the non-permissive temperature. TA in lysates obtained from A239-MB cells was 3-4 times more thermolabile by complement fixation than TA obtained from wild-type-transformed cells (SVWT-MB) when incubated at 33 or 40.degree. C. These data complement previous reports using TA from lytic infection and are consistent with the suggestion that TA is virus encoded. In contrast to TA, which even in wild-type-transformed cells was completely destroyed in < 10 min at 50.degree. C, TSTA, assayed in vivo by tumor rejection, and tumor-specific surface antigen(s) (TSSA), defined by an in vitro cytolytic assay, were thermostabile. Even after 24 h of incubation of extracts at 50.degree. C, high levels of TSTA and TSSA activity were present. Since these surface antigens when obtained from cells transformed by ts-A mutants were also thermostabile, they could not be distinguished from the wild-type antigens. These results indicate a coordinate expression of TA and TSTA in transformed cells; conform that TA is virus encoded; and confirm that the antigenic and immunogenic determinants that characterize TA and TSTA activities are distinct. The possibility that TSTA, like TA, is of viral rather than cellular origin is not excluded.