In vivo acquired mechanisms of tumor cells local defense against the host innate immunity effectors: implication in specific antitumor immunity

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.

The fingerprints of the host innate immunity on the cells of primary virus-induced tumors

As shown earlier, the cells transformed in vitro by various oncogenes, during subsequent in vivo growth were gradually replaced by descendant tumor cells, which co-expressed highly increased H(2)O(2)-catabolizing antioxidant activity (H(2)O(2)(CA)), and the ability to release PGE(2) (PGE(S)) in contact with natural killer cells; v-src was the only oncogene, which in vitro induced cells transformation characterised with the expression of [H(2)O(2)(CA)+PGE(S)] phenotype. Expression of [H(2)O(2)(CA)+PGE(S)] phenotype was providing tumor cells with significantly increased resistance to cytotoxic activities of macrophages and NK cells. However, the possible involvement of [H(2)O(2)(CA)+PGE(S)] phenotype in primary carcinogenesis remained obscure. Here, using three models of the primary virus-induced Syrian hamster tumors we demonstrated that Rous Sarcoma Virus-induced tumors arising after short latent period expressed [H(2)O(2)(CA) + PGE(S)] phenotype at appearance. During the latent periods of SV40- and SA7(C8)-induced tumors the cells expressing [H(2)O(2)(CA)+PGE(S)] phenotype gradually replaced the original [H(2)O(2)(CA)+PGE(S)]-phenotype-negative cell populations. The effectiveness of such selection correlated with the duration of in vivo tumor development. Thus it was shown, that selection of tumor cells expressing [H(2)O(2)(CA)+PGE(S)] phenotype is beginning and may be completed during the latent period of primary carcinogenesis. Taken together, data of this and preceding our studies on [H(2)O(2)(CA)+PGE(S)] phenotype demonstrate that in vivo the host innate immunity antitumor reactions are apparently responsible for the selection of rare tumor cell variants capable to defend themselves against CTA of Mph and NK.