Urine gamma-synuclein as a biomarker for the diagnosis of bladder cancer

Caiyun Liu,Qiang Lv,Like Qu,Chao Qin,Chengchao Shou,Jianzhong Shou,Yanning Gao,Jiyu Zhao,Nianzeng Xing,Bingbing Shi,Chonghua Hao,Qinghai Wang

doi:10.18632/oncotarget.9468

Abstract

Gamma-synuclein (SNCG) is secreted from tumor cells and elevated in the urine of bladder cancer (BCa) patients, however, the diagnostic and prognostic values of urine SNCG for BCa remain unknown. Here, we used enzyme immunoassay and western blotting to measure urine SNCG levels. Patients with BCa or other urological diseases and healthy controls were enrolled at four Chinese hospitals from April 2010 to November 2014. Diagnostic performance was evaluated by analyzing the area under receiver operating characteristic curves (AUROCs). The AUROC was 0.903 ± 0.019 (95% confidence interval [CI], 0.867 - 0.940) for the test and 0.929 ± 0.015 (95% CI, 0.901 - 0.958) for the validation cohort. The optimal cutoff value yielded sensitivities of 68.4%, 62.4% and specificities of 97.4%, 97.8% for the test and validation cohort, respectively. Urine SNCG levels were decreased after tumor resection, but were higher in BCa patients with recurrence than those without (P = 0.001). The urine SNCG levels in patients with urological benign diseases were significantly lower than BCa patients (all P < 0.05) but higher than healthy controls (all P < 0.05). Hematuria did not interfere with the SNCG detection by spiking urine specimens with whole blood. Compared with a nuclear-matrix-protein-22 assay in an additional cohort excluding hematuria, SNCG showed a similar sensitivity and higher specificity. In summary, our results demonstrated that urine SNCG can discriminate BCa from urinary diseases, and is a useful prognosticator of postsurgical recurrence.

Highlights

For the analysis of SNCG protein expression in bladder cancer tumors, cell lysates were prepared by homogenizing tumor tissues in a buffer containing 10 mM pH 8.0 PBS, 1% Triton x-100 (PBST), and 0.25% sodium deoxycholate and protease inhibitor cocktail (Roche Applied Science, Indianapolis, IN)
The resolved protein bands electrophoretically transferred to nitrocellulose membranes (GE Healthcare, Waukesha, WI), and blocked for 2 h in 4% nonfat dry milk in PBST
Quality control samples containing three different concentrations of SNCG were analyzed in each microtiter plate

Summary

Introduction

For the analysis of SNCG protein expression in bladder cancer tumors, cell lysates were prepared by homogenizing tumor tissues in a buffer containing 10 mM pH 8.0 PBS, 1% Triton x-100 (PBST), and 0.25% sodium deoxycholate and protease inhibitor cocktail (Roche Applied Science, Indianapolis, IN). Cell lysates or urine samples were analyzed by sodium dodecyl sulfatepolyacrylamide gel electrophoresis in a 15% acrylamide gel. Paired urine and tumor samples were analyzed to compare the levels of SNCG expression.

Results

Conclusion