Germ cell-like telomeric length homeostasis in nonseminomatous testicular germ cell tumors

Telomere maintenance plays an important role in cell proliferation and tumo r survival. Human male germ cells, which carry long telomeres and express t elomerase, give rise to a highly heterogeneous group of malignant tumors. W e compared telomeric length and telomerase activity between two major histo logical types of primary testicular germ cell tumors. Fifteen out of 16 sem inoma samples revealed telomeric restriction fragment (TRF) length below 13 kb; the remaining seminoma showed a major TRF fraction of 18 kb and a dist inct minor fraction of above 23 kb length. In contrast, all 13 samples from nonseminomas showed TRF length greater than or equal to 23 kb, which is si milar to that reported in human sperm. Nine out of 11 seminoma specimens an d six out of seven nonseminomas studied showed moderate to high telomerase activity, the only telomerase-negative non-seminoma being pure mature terat oma. These results indicate to a major difference in telomeric length betwe en seminomas and nonseminomas, which is apparently unrelated to the presenc e of telomerase activity, and suggest a germline-like homeostasis of telome ric length is preserved in human nonseminomas.