Introduction: Testicular tumors are heterogeneous group of neoplasms divided mainly into two types: seminomas and non-seminomas. Nucleolin (NCL) and nucleophosmin (NPM) are abundant nucleolar proteins involved in many physiologic and pathologic processes including cancer. Their overexpression was found in many tumors but it was not studied in testicular cancer.
Material and methods: The study was performed on tissue microarrays of 19 seminomas, 21 embryonal carcinomas and 11 yolk sac tumors. The expression of NCL and NPM was detected with monoclonal antibodies and visualized with EnVision FLEX/HRP technique. Immunohistochemical reactions were measured with Aperio ImageScope Software and analyzed as means of percentages of all immunopositive cells in three groups of reaction intensity, i.e. 3+, 2+, and 1+ as well as of H-score.
Results: Seminomas showed higher expression of nucleolin indicated by higher H-score and higher percentage of positive cells than non-seminomas. The differences in subpopulations of NCL-positive cells were also found. Embryonal carcinomas and yolk sac tumors showed lower expression of NCL than seminomas indicated by H-score. The percentage of NCL-positive cells did not differ between embryonal carcinomas and seminomas while there were significant differences in subpopulations of cells. The percentage of NCL-positive cells in yolk sac tumors was lower than in seminomas. The results show different heterogeneity of subpopulations of NCL-positive cells in embryonal carcinomas and yolk sac tumors compared to seminomas. The analysis of nucleolin expression in embryonal carcinomas and yolk sac tumors showed no differences between these two tumor types. No differences in nucleophosmin expression between seminomas and non-seminomas were found.
Conclusions: The differences in the expression of nucleolin between two groups of germ cell testicular tumors found in the current study indicate a new aspect of biology of these neoplasms and require further studies on the role of nucleolin in germ cell tumorigenesis.
Keywords: IHC; germ cell tumor; nucleolin; nucleophosmin; seminoma; testis.