Early phenotypic changes of in vitro transformed cells during in vivo progression: possible role of the host innate immunity.

We described the earliest in vivo changes of in vitro transformed cells of various origin manifested in highly-increased H(2)O(2)-catabolizing and PGE(2)-releasing activities. We designate it as [H(2)O(2)(CA) + PGE(S)]-phenotype. It provided tumor cells with resistance to cytotoxicity of Mph and NK cells and correlated with increased tumorigenicity. Used as a functional marker of the early step of in vivo tumor progression [H(2)O(2)(CA) + PGE(S)]-phenotype allowed to estimate the difference in the rates of natural selection of tumor cells grown locally and/or disseminated and its significant delay related to bcl-2 gene expression. The data suggests that in vivo sublethal damage of tumor cells and activation of src gene are relevant to acquisition of [H(2)O(2)(CA) + PGE(S)]-phenotype.