Significance of apoptosis in metastasizing testis tumors

Testis tumors of embryonal origin (ten metastasized, six non-metastasized) and 17 mixed testis cell carcinomas (eight metastasized, nine non-metastasized) were examined. A triple immunofluorescence microscopic labeling procedure allowed the simultaneous detection of two features of apoptosis, namely morphological changes in the nucleus (DNA condensation visualized by DAPI staining) and the process of DNA fragmentation (TdT-assay) in tumor cells as well as T-cells (recognized by their CD45RO epitope). Both methods for apoptosis detection showed similar apoptotic indices (AI) only in 2.6% of all tumors. Most tumors (81.6%) showed more cells with DNA fragments than condensed chromatin, but in a number of cases (10.5%) the opposite pattern was found. These data add to the few published in vivo examinations of apoptosis using different methods and help to explain differences in the judgment of apoptosis significance for tumor prognosis. With regard to tumorigenesis, non-metastasized testis tumors were characterized by higher AIs of tumor cells and T-cells compared with metastasized tumors, which could be interpreted as a characteristic of tumors in an earlier stage of their development into an apoptosis-resistant phenotype. For the first time, in metastasized tumors a 5 to 25-fold increase of the T-cell’s AIs over the corresponding AIs of tumor cells was shown. This suggests a successful counterattack of tumor cells, thus supporting the process of metastasis. However, only ten out of 33 tumors revealed these AI changes, which again highlights that tumor biology cannot be predicted by a single parametric approach. It remains to be seen whether these characteristics might be suitable for a reliable prediction of metastasis.