Mitogenic and antimitogenic transforming growth factors secreted by adenovirus 2- and XXXX -transformed hamster cells: possible roles in promoting tumorigenesis.

@entity1659 @entity9504 @entity2235 @entity5 @entity7790 @entity2533 @entity1014
@entity9504 ( @entity9504 )- and @entity2235 (SV40)-transformed hamster embryo cells differ markedly in a number of phenotypic properties including their potential for inducing @entity5 in hamsters. Both @entity9504 - and SV40-transformed cells are immortalized and readily induce @entity5 in immunoincompetent newborn syngeneic hamsters, but only SV40-transformed cells are highly oncogenic in both adult syngeneic and allogeneic immunocompetent hamsters. The reasons for the difference in the oncogenic potential of the @entity9504 - and SV40-transformed phenotypes remain elusive. However, recent studies with transforming growth factors (TGFs) indicate that these factors play an important role in determining many phenotypic characteristics of transformed cells. To determine whether TGFs secreted by @entity9504 - and SV40-transformed hamster embryo cells differ, we have examined the ability of media conditioned by these two transformed cell phenotypes to modulate @entity1014 uptake in quiescent, untransformed cells. We found that both transformed phenotypes secrete very similar @entity7790 -like mitogenic factors which inhibit binding of 125I-labeled epidermal growth factor to its receptor. Our results also show that SV40-transformed cells, but not @entity9504 -transformed cells, secrete a powerful @entity1659 ( @entity1659 ). The @entity1659 secreted by SV40-transformed cells is inhibitory for several transformed and untransformed cell types and exerts a cytostatic, not cytolytic, action on untransformed primary hamster embryo cells. @entity1659 elutes from size exclusion high-performance liquid chromatography columns with a molecular weight of 24,000. Although @entity1659 has about the same molecular weight as @entity2533 , it differs from @entity2533 in two important respects: it is heat labile and it has a different target specificity for antimitogenic activity. The @entity1659 secreted by SV40-transformed cells also inhibits @entity1014 uptake by concanavalin A-stimulated spleen lymphocytes. This finding suggests that @entity1659 might contribute to the extreme oncogenicity of SV40-transformed cells by inhibiting mobilization of immune effector cells at the site of @entity5 cell proliferation.
