XPA-210: a new proliferation marker to characterize tumor biology and progression of renal cell carcinoma

Recent lung cancer data have shown an association of XPA-210, a key peptide of thymidine kinase, with advanced disease. We thus assessed its proliferation status in primary (M0) and metastatic (M1) renal cell carcinoma (RCC). Paraffin slides from 30 patients (mean age: 61.2 years; range: 42-84) with clear-cell RCC (M0 in 10; non-osseous M1 in 10; osseous M1 in 10) were T-matched for pT1/pT3. Corresponding malignant and benign renal parenchyma were immunohistochemically stained against XPA-210. Staining density was determined by a semi-quantitative score of positive cell shares. Staining intensity included the precise cellular location. XPA-210 occurred predominantly in the nucleus, with a minor cytoplasmatic component. RCC tissue showed higher density and stronger intensity than did benign renal tissue in both nucleus (P = 0.005) and cytoplasm (P = 0.01). Density and intensity were positively associated with tumor diameters a parts per thousand currency sign7 cm, whereas they tended to correlate inversely in tumors > 7 cm (P = 0.07). Density of stained cells was significantly higher in metastatic than in localized RCC in both nucleus and cytoplasm (P < 0.04). Non-osseous M1 tissue showed significantly higher nuclear and cytoplasmatic expression than did M0 tissue (P < 0.05), whereas osseous M1 tissue did not. In all RCC tissues, XPA-210 staining was significantly higher in the nucleus than in cytoplasm, potentially owing to large cytoplasmatic spaces as a characteristic histologic feature of clear-cell component. XPA-210 expression gradually increased from localized to metastatic disease, peaking in patients without bone involvement. Therefore, XPA-210 might aid the selection of appropriate adjuvant treatment in high-risk patients.