Variants in KITLG predispose to testicular germ cell cancer independently from spermatogenic function

Epidemiological data suggest an association and a common pathogenetic link between male infertility and testicular germ cell tumor (TGCT) development. Genome-wide studies identified that TGCT susceptibility is associated with KITLG (c-KIT ligand), which regulates the formation of primordial germ cells, from which TGCT is believed to arise and spermatogenesis develops. In this study, we analyzed the link between KITLG, TGCT, and spermatogenic disruption by performing an association study between the KITLG markers rs995030 and rs4471514 and 426 TGCT cases and 614 controls with normal and abnormal sperm count. We found that TGCT risk was increased more than twofold per copy of the major G allele and A allele in KITLG rs995030 and rs4471514 (odds ratio (OR)=2.38, 95% confidence interval (95% CI)=1.81-3.12; OR=2.43, 95% CI=1.86-3.17 respectively), and homozygotes for the risk allele had a sevenfold increased risk of TGCT. KITLG markers were strongly associated with seminoma subtype (per allele risk increased more than threefold, homozygote risk increased by 13- to 16-fold) and weakly with nonseminoma. KITLG markers were not associated with sperm production, as no difference was observed in men with normozoospermia and azoo-oligozoospermia, both in controls and in TGCT cases. In conclusion, this study provides evidence that KITLG variants are involved in TGCT development and they represent an independent and strong specific risk factor for TGCT independently from spermatogenic function. A shared genetic cause and a common pathogenetic link between TGCT development and impairment of spermatogenesis are not evident from this study.