Expression of Adipose Differentiation-Related Protein: A Predictor of Cancer-Specific Survival in Clear Cell Renal Carcinoma

Abstract

We recently found that adipose differentiation-related protein (ADFP) is a potential diagnostic and prognostic biomarker for clear cell subtype renal cell carcinoma (RCC). To further evaluate the correlation between ADFP expression levels and clinicopathologic characteristics and patient outcome, we retrospectively examined patients with clear cell RCC. A series of 432 consecutive patients with sporadic clear cell RCC who underwent nephrectomy between March 1986 and June 2004 were enrolled in the study. ADFP expression levels in the primary tumors and in 18 metastases were measured by real-time quantitative PCR. The clinicopathologic and prognostic data were collected, as well as the von Hippel-Lindau disease (VHL) gene alteration status in selected cases. ADFP expression was apparently high in cases without a symptomatic presentation, as well as in cases of low-stage, low-grade, or VHL alteration-positive clear cell RCC, whereas it was down-regulated in undifferentiated tumors with a spindle/pleomorphic component or metastatic lesions. Univariate analyses showed that high ADFP expression was associated with better cancer-specific survival and cancer-free survival. Further Cox multivariate analyses combined with the split-sample validation method showed that ADFP expression still remains an independent predictor for cancer-specific survival in all tumor stages and in advanced metastatic cases, whereas the predictive value of ADFP expression for cancer recurrence is rather weak. The ADFP expression may represent the tumor differentiation status, and the detection of the expression levels provides useful prognostic information for cancer-specific survival in patients with clear cell RCC.