The usefulness of serum X-linked inhibitor of apoptosis protein (XIAP) for predicting recurrence of renal cell carcinoma.

e15055 Background: The X-linked Inhibitor of Apoptosis protein (XIAP) is associated with cell survival by blocking caspase-mediated apoptosis. We have reported the expression and prognostic value of XIAP in human prostate cancer using prostate tissue microarrays (Clin Cancer Res 2007). The expression and prognostic significance of XIAP in renal cell cancer (RCC) has been rarely studied. To our knowledge, no report on the serum XIAP levels from RCC patients has been published. In this study, we examined serum XIAP levels of RCC patients and normal individuals and evaluated its utility as biomarker. Methods: Peripheral blood samples were obtained from 99 patients (68 men and 31 women, median age; 60.7 years [36-85]) with RCC before surgery. All the patients underwent radical or partial nephrectomy. Blood samples were also collected from 52 healthy controls. The histological grade was as follows: grade 1; n= 5, grade 2; n=72, grade 3; n= 22. The serum XIAP levels were measured by a sandwich enzyme-linked immunosorbent assay. Cut off value was calculated by ROC analysis. Results: The serum XIAP levels in patients with RCC were higher than those of normal control individuals (328.3 pg/ml vs 156.2 pg/ml, p<0.001). At a median follow up of 33 months (1-105M), tumor with low serum XIAP showed significantly longer progression free survival (PFS) than those with high serum XIAP in grade 1-2 group (p<0.001). Conclusions: Serum XIAP level is associated with recurrence and prognosis. These results suggest that it may be used as a novel prognosticator and a potential target for renal cell cancer diagnosis and therapy.