Cytogenetic evidence for premeiotic transformation of human testicular cancers.

To determine the point at which transformation of the germ cell occurs during meiosis in nonseminomatous testicular cancer, the sex chromosome compositions of 15 cell lines derived from primary tumors or metastases of 12 patients with testicular cancer were analyzed by trypsin G-banding analysis and Y-body staining. The simultaneous existence of both X- and Y-chromosomes in a single cell has been confirmed in 14 cell lines. This suggests that transformation of the cell occurs before the first meiotic division because it is known that segregation of X- and Y-chromosomes occurs during the first meiotic division. An incidental finding was the presence of Barr bodies in some cell lines containing more than one X-chromosome, which is consistent with the known primitive nature of testicular cancer and its ability to differentiate independently from the male host.