Exposed proliferation antigen 210 (XPA-210) in renal cell carcinoma (RCC) and oncocytoma: clinical utility and biological implications.

OBJECTIVE: •  To determine the clinical role of the exposed proliferation antigen 210 (XPA-210) of the proliferation marker thymidine kinase 1 (TK1) in a large cohort of different renal cell carcinoma (RCC) types, oncocytomas and normal renal tissues samples, as TK1 is reported to be of clinical significance in several cancer entities and is suggested as a prognostic serum biomarker for RCC.

PATIENTS AND METHODS: •  Expressions of XPA-210 were determined immunohistochemically in 40 clear cell RCCs (ccRCC), 25 papillary RCCs (papRCC), 17 chromophobe RCC (chRCC), 27 oncocytomas and 64 normal renal parenchyma paraffin-embedded specimens. •  Immunohistochemistry was performed with a monoclonal anti-XPA-210 antibody. Staining was measured by the percentage of positive cells. •  Expression was compared between subgroups and correlated with respective clinical data using one-way analysis of variance with post hoc Tukey-Kramer analyses.

RESULTS: •  XPA-210 staining in the RCC subgroup was significantly different from the oncocytomas (mean [sem] 4.1 [0.4] vs 2.2 [0.4]; P = 0.004) and from normal renal tissue (1.0 [0.1]; P < 0.001], whereas oncocytomas did not differ from normal renal parenchyma staining (P = 0.18). •  Subdivided into RCC groups, only ccRCC (mean [sem] 5.1 [0.6]; P < 0.001) and papRCC (4.4 [0.6]; P < 0.001) varied from normal renal parenchyma, whereas chRCC (1.4 [0.3]; P = 0.99) did not. •  RCC XPA-210 staining was significantly associated with higher tumour stage (T = 3, P = 0.002) and grade (G = 3, P = 0.001).

CONCLUSIONS: •  The malignant character of RCC is reflected by higher XPA-210 expression as compared with oncocytomas and normal kidney. •  The ccRCC and papRCC subgroups had higher XPA-210 levels. •  XPA-210 could be considered a potential marker for the assessment of the proliferative activity in primary RCC.