Apoptosis: a key effector mechanism of lymphocyte action in human nonseminomatous testicular carcinoma?

Abstract

To correlate the number of tumour-infiltrating T lymphocytes (TILs) with the extent of apoptosis in testicular germ cell tumours, as TILs are considered to be a favourable prognostic factor of human testicular tumours, especially of seminomas, but the mechanism by which TIL contribute to an improved outcome is unclear. Tissue samples from 47 patients with nonseminomatous germ cell tumour (NSGCT) and 15 with seminomatous GCT were investigated immunohistochemically for lymphocyte infiltration and apoptosis. The apoptotic index (AI) was assessed in various categories (DNA condensation and fragmentation) using in-situ end-labelling to identify typical apoptotic DNA strand breaks, and nuclear staining to identify typical apoptotic morphology. In seminomatous GCT there was no correlation between the number of TILs and any AI. In NSGCT there was only a relationship between lymphoid infiltration and those AIs showing morphological criteria of apoptosis in a small subgroup of NSGCT, i.e. metastasized embryonal cell carcinomas. Only 1.2% (AI, chromatin condensation) and 0.8% (AI, fragmentation and condensation) of all tumour cells showed these features of apoptosis. The overall AI in NSGCT was 7.9%. TILs do not seem to induce apoptosis in testicular tumours. Embryonal cell carcinomas might be susceptible to lymphocyte attack, resulting in apoptosis of the tumour cell. The mechanisms of interaction between lymphocytes and testis tumour cells need further investigation.