Expression and amplification of Topoisomerase-2α in type 1 and type 2 papillary renal cell carcinomas and its correlation with HER2/neu amplification.

The current study was undertaken to investigate chromosomal and genetical aberrations leading to overexpression of Topoisomerase-2α (TOP2α) and to reveal the possible association of these aberrations with HER2/neu overexpression and gene amplification, and to search for the relationship between TOP2α and HER2/neu status with prognostical biomarkers in papillary renal cell carcinoma (RCC), a group of tumors with diverse molecular, chromosomal and clinical features. Archival cases of papillary RCC obtained from Departments of Pathology of Pamukkale, Ege and Dokuz Eylul Universities were studied in two groups (type 1 and type 2) each containing 20 cases. The level of TOP2α and HER2/neu expression by tumor cells were determined immunohistochemically. A multicolor FISH probe was used to define both amplification of HER2/neu and TOP2α genes, and polysomy 17. The ratio of cells expressing TOP2α in type 1 and type 2 papillary RCC were 24.29% and 6.89%, respectively. The difference was statistically significant comparing the average or median values of groups separately (p = 0.002). The expression levels of TOP2α and HER2/neu were also correlated. TOP2α and HER2/neu were co-amplified in both groups. Immunohistochemical expression was not observed in 15 of 23 cases with HER2/neu amplification. The most frequent finding detected by FISH method was polysomy of chromosome 17. We had contradictory results compared with the findings reported in the limited numbers of literature. It shows us that papillary RCC constitute a heterogenous group of tumors with various cytogenetic features and morphological classification of these tumors may not be compatible with their molecular characteristics.