ERVW-1 and testicular germ cell tumor: Besides these virus-specific regulatory functions, a pathological role of Rec was firstly suggested in human germ cell tumors (hGCT), due to the expression of HML2 env spliced mRNA variants (Löwer et al., 1993) and the development of anti-HML2 Env Abs in ~85% of patients (Sauter et al., 1996).