The association of NOX4 mediated nuclear colocalization and overall survival in renal cell carcinoma.

Abstract

639 Background: NOX4 protein are involved in cell differentiation, migration and apoptosis. We recently demonstrated that NOX4 in renal cell carcinoma (RCC) is an energetic sensor and couples energy metabolism to drug-resistance. In this study we demonstrate that enhanced nuclear localization of NOX4 is correlated with poor survival. Methods: We identified 350 RCC patients with (n = 85) and without (n = 265) venous tumor thrombus (VTT) who underwent radical nephrectomy with or without thrombectomy at our institution between 2013-2016. Fifty patients with RCC and VTT were matched 1:1 to patients with RCC and no VTT. Tissue Microarray (TMA) consisting of primary renal tumor, adjacent renal tumor and VTT were created. These matched TMA (n = 174) were stained with NOX4 antibodies; scanned using the Aperio scanning system and analyzed with the ImageScope software. The RCC nucleus was evaluated for roundness, elongation and size. NOX4 nuclear staining was categorized based on intensity as either strong positive, moderate, weak or no localization. Differential protein expression between the primary tumor, adjacent normal parenchyma and VTT was assessed using the Chi-squared test or t-test. Progression-free survival (PFS) and overall-survival (OS), stratified by NOX4 staining intensity, was estimated using the Kaplan-Meier method and compared with the log-rank test. Cox regression model was used to investigate effect of NOX4 staining on survival in multivariate analyses. Results: NOX4 nuclear colocalization was higher in patients who had progression and death from RCC. On univariate analysis, the intensity of NOX4 protein expression in the nucleus was significantly associated with PFS (HR 1.67, 95%CI (1.08-2.57; p = 0.02) and OS (HR 2.31, 95%CI (1.26-4.24; p = 0.007). On multivariate analyses the association between NOX4 protein expression and OS remains statistical significance (HR 2.09, 95%CI (1.05-4.18, p = 0.037). Conclusions: We provide evidence that in high grade/high stage cancer, NOX4 is colocalized within the nucleus of RCC. The prognostic role of NOX4 was determined at the protein level. We provide rationale for further investigation of NOX4, which may serve as a checkpoint in RCC.