Biomedical subjects

Christian K Behrens

Publications and source records attributed to Christian K Behrens.

3 recordsLinked to original sources

PubMed2005

CD95L mediates tumor counterattack in vitro but induces neutrophil-independent tumor rejection in vivo.

Many tumors express CD95L (CD178, FasL, APO-1L) and may thus kill tumor-infiltrating lymphocytes, a phenomenon called tumor counterattack. However, presently it is not clear whether tumor counterattack is a relevant immune escape mechanism. To characterize the effect of CD95L expression of tumor cells on tumor-specific T cells, we established an in vitro system with TCR tg T cells and a model tumor antigen. Preactivated antitumor T cells were able to kill CD95L(-) and CD95L(+) tumor cells. CD95L(+) tumor cells killed activated T cells in vitro and inhibited the expansion of cytotoxic antitumor T cells in mixed lymphocyte tumor reactions. In vivo CD95L expression led to delayed tumor growth or complete tumor rejection. Neutrophils were not responsible for the delayed growth of the CD95L(+) tumors tested. In mice with neutrophils deficient for important cytotoxicity mechanisms (p47phox(-/-) or iNOS(-/-) mice), CD95L(+) tumors grew similarly as in wild-type mice. Incidence and growth rate of CD95L(+) tumors in mice injected with a neutrophil-depleting or an isotype control antibody was the same. In CD95-deficient lpr mice, tumor growth was not altered as compared to wild-type mice. Taken together, CD95L mediated tumor counterattack in vitro, but led to neutrophil-independent tumor rejection in vivo.

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PubMed2003

The influence of CD95L expression on tumor rejection in mice.

Many tumors express the death ligand CD95L (CD178, APO-1L, FasL) and can kill activated T cells in vitro. This may enable the tumor cells to suppress anti-tumor immune responses, a phenomenon called "tumor counterattack". Preliminary evidence of tumor counterattack in human tumors exists. However, CD95L-expressing tumors are rapidly rejected in mice. In order to clarify this controversial situation we investigated whether the level or the time point of CD95L expression might be critical factors determining tumor counterattack versus tumor rejection. We generated CD95-resistant tumor cell lines expressing different levels of CD95L (LKC-CD95L). In nude mice the CD95L expression level had no influence on the growth of the CD95L(+) tumors. In contrast, a CD95L(-) control tumor cell line (LKC) grew much faster. In addition, we generated a CD95-resistant cell line in which CD95L was induced via the tet system (LKCR-tetCD95L). Induction of CD95Lin established tumors in nude and NOD/SCID mice led to rapid rejection of the tumors. Induction of lower CD95L expression levels delayed tumor rejection only marginally. These results demonstrate that rejection of CD95L-expressing tumors in mice is not a result of overexpression and does not depend on the presence of CD95L at the onset of tumor progression.

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PubMed2002

Transcriptomics in predictive toxicology.

Once again, genomics is about to change drug development. Following its major impact on target discovery and assay development, which increased the number of compounds at early stages of the process, genomics is now zeroing in on the prediction of potential toxicological problems of compounds. Toxicogenomics is the analysis of toxicological processes at the transcriptome level of a target organ or cell. By simultaneously monitoring the effect of a compound on the transcription levels of hundreds to thousands of genes, toxicogenomics can provide an enormous amount of data. This data bears information on the way in which compounds act at the molecular level, reaching far beyond the mere conclusion of whether or not a particular toxicological outcome is elicited. By compiling transcription profiles for well-known toxicants, we are beginning to learn how to analyze this novel type of data in the context of mechanistic and predictive toxicology.

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