Tumour samples from 49 consecutive testicular cancer patients treated in the Cancer Centre and Institute of Oncology, Warsaw, Poland, and control blood samples from 55 healthy men provided by the local blood bank were examined. To analyse the number of CAG repeats in the POLG gene, the second exon of this gene was amplified by PCR and sequenced directly using primers designed by Rovio et al. [3]. Each PCR product was sequenced twice. Of the 55 healthy Polish men, 49 (89%) were homozygotes in the POLG gene with common 10 repeats in both alleles (wild-type), and six (11%) were 10/11, 10/12 and 10/9 heterozygotes in three, two and one individual, respectively. The frequency of wild-type homozygotes in the Polish healthy men population proved to be significantly different (P=0.02 by the
2 test) from that of other European populations (75%) [3
]. This is in accordance with a recent report that different populations were characterised by different numbers of CAG repeats [5
].
Of 49 testicular tumour patients, 36 (74%) were wild-type homozygotes in CAG repeats in POLG gene and 13 (26%) lacked one or both wild-type alleles, with the 10/11 variant in 10 patients and the 10/12, 10/6 and 11/11 variants in one patient each. In the Polish population-specific number of CAG repeats, the polymorphic DNA polymerase gene was significantly more frequent in testicular cancer patients than in healthy men (26% versus 11%, P=0.035 by the Fisher exact test). No significant differences in the pathological and clinical features of the tumours, in the course of the disease or in the response to treatment were found between carriers and non-carriers of polymorphic variants.
Our data support the role of susceptibility genes in testicular cancer and indicate the polymorphic mitochondrial DNA polymerase gene as a likely candidate.
1 Department of Molecular Biology, 2 Department of Urological Oncology, 3 Department of Pathology, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Roentgena 5, 02781Warsaw, Poland
(*Email: radka{at}coi.waw.pl)
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