168 research article Loss of heterozygosity of CDKN2A (p16INK4a) and RB1 tumor suppressor genes in testicular germ cell tumors Tomislav Vladusic1*, Reno Hrascan1*, Nives Pecina-Slaus2, Ivana Vrhovac1, Marija Gamulin3, Jasna Franekic1, Bozo Kruslin4 1 Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia 2 Laboratory of Neurooncology, Croatian Institute for Brain Research, Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia 3 Department of Oncology, Rebro University Hospital Center, Zagreb, Croatia 4 Ljudevit Jurak Department of Pathology, Sisters of Mercy University Hospital, Zagreb, Croatia Received: 17 March 2010 Accepted: 25 May 2010 * These two authors contributed to this work equally. Disclosure: No potential conflicts of interest were disclosed. Correspondence to: Tomislav Vladušić, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia. E-mail: tvladusic@pbf.hr Background. Testicular germ cell tumors (TGCTs) are the most frequent malignances in young adult men. The two main histological forms, seminomas and nonseminomas, differ biologically and clinically. pRB protein and its immedi- ate upstream regulator p16INK4a are involved in the RB pathway which is deregulated in most TGCTs. The objective of this study was to evaluate the occurrence of loss of heterozygosity (LOH) of the CDKN2A (p16INK4a) and RB1 tumor suppressor genes in TGCTs. Materials and methods. Forty TGCTs (18 seminomas and 22 nonseminomas) were analyzed by polymerase chain reaction using the restriction fragment length polymorphism or the nucleotide repeat polymorphism method. Results. LOH of the CDKN2A was found in two (6%) out of 34 (85%) informative cases of our total TGCT sample. The observed changes were assigned to two (11%) nonseminomas out of 18 (82%) informative samples. Furthermore, LOH of the RB1 was detected in two (6%) out of 34 (85%) informative cases of our total TGCT sample. Once again, the observed changes were assigned to two (10.5%) nonseminomas out of 19 (86%) informative samples. Both LOHs of the CDKN2A were found in nonseminomas with a yolk sac tumor component, and both LOHs of the RB1 were found in nonseminomas with an embryonal carcinoma component. Conclusions. The higher incidence of observed LOH in nonseminomas may provide a clue to their invasive behavior. Key words: loss of heterozygosity; CDKN2A; RB1; seminomas; nonseminomas Introduction Testicular germ cell tumor (TGCT) is diagnosed mainly after puberty and is the most frequent ma- lignancy in young adult men1, however, it is also not rare in childhood.2 The two main histological forms, seminomas and nonseminomas, differ bio- logically and clinically. About 50% of TGCTs are pure seminomas and 40% pure or mixed nonsemi- nomas. The remaining 10% containing both semi- noma and nonseminoma components are classi- fied as being nonseminoma according to the World Health Organization (WHO) classification system.3 The genetic alterations underlying the develop- ment of these neoplasms have not been understood fully, although much has been done to elucidate them.4,5 The cell cycle regulatory pathway deregulated in almost all human tumors appears to be the G1 phase-controlling mechanism centered around the pRB protein. Different cancers seem to have altered different key components of that mecha- Radiol Oncol 2010; 44(3): 168-173. doi:10.2478/v10019-010-0035-7