Interpretation of data from comparative genomic hybridization (CGH) analysis of
testicular neoplasms located within normal parenchyma is complicated, because the results may be influenced by a heterogeneity of subpopulations with different
chromosomal aberrations and ploidy. In this study, therefore, early stages of testicular germ cell
neoplasia were cytogenetically analyzed after flow sorting of nuclei according to their
DNA ploidy.
DNA from subpopulations with different ploidy was globally amplified by means of degenerate
oligonucleotide primed polymerase chain reaction, labeled with
FITC-
dCTP and -dUTP by nick translation, and analyzed with high resolution CGH. A characteristic pattern of
chromosomal abnormalities associated with testicular
germ cell cancer (gains in 1q, 7, 8, 12, 14, 21, X; losses from 4, 5, 9, 11, 13, 18, Y) was observed in the tri- to hexaploid but not in the hyperdiploid or in pure
tetraploid subpopulations. Our data suggest that subpopulations with a
triploid to hexaploid
DNA content purified from testes with germ cell
neoplasia harbor a mixture of overt
tumor and
carcinoma-in-situ cells (CIS) and
DNA content of CIS cells being in the
triploid to hypotetraploid range, supporting the current theory of polyploidization as one of the first events of malignant transformation.