MicroRNA 193b-3p as a predictive biomarker of chronic kidney disease in patients undergoing radical nephrectomy for renal cell carcinoma

Abstract

Background: A significant proportion of patients undergoing radical nephrectomy (RN) for clear-cell renal cell carcinoma (RCC) develop chronic kidney disease (CKD) within a few years following surgery. Chronic kidney disease has important health, social and economic impact and no predictive biomarkers are currently available. MicroRNAs (miRs) are small non-coding RNAs implicated in several pathological processes.

Methods: Primary objective of our study was to define miRs whose deregulation is predictive of CKD in patients treated with RN. Ribonucleic acid from formalin-fixed paraffin embedded renal parenchyma (cortex and medulla isolated separately) situated >3 cm from the matching RCC was tested for miR expression using nCounter NanoString technology in 71 consecutive patients treated with RN for RCC. Validation was performed by RT-PCR and in situ hybridisation. End point was post-RN CKD measured 12 months post-operatively. Multivariable logistic regression and decision curve analysis were used to test the statistical and clinical impact of predictors of CKD.

Results: The overexpression of miR-193b-3p was associated with high risk of developing CKD in patients undergoing RN for RCC and emerged as an independent predictor of CKD. The addition of miR-193b-3p to a predictive model based on clinical variables (including sex and estimated glomerular filtration rate) increased the sensitivity of the predictive model from 81 to 88%. In situ hybridisation showed that miR-193b-3p overexpression was associated with tubule-interstitial inflammation and fibrosis in patients with no clinical or biochemical evidence of pre-RN nephropathy.

Conclusions: miR-193b-3p might represent a useful biomarker to tailor and implement surveillance strategies for patients at high risk of developing CKD following RN.

Figure 1

Schematic overview of the study. *The eGFR>60 ml min^-1 based on CKD-EPI formula 2009. CKD, chronic kidney disease; eGFR, estimated glomerular fraction rate; ISH, in situ hybridisation; RN, radical nephrectomy.

Figure 2

Heatmap showing miR expression in medulla of patients with normal kidney function (NKF) compared with patients developing chronic kidney disease (CKD) 12 months post nephrectomy for RCC. The miRs with a P-value ⩽0.1 are shown.

Figure 3

Decision curve analysis plot comparing performance of a predictive score including clinical variables (base model) alone or in combination with specific miRs.

Figure 4

MiR-193b-3p in situ hybridisation in ‘normal' parenchyma adjacent to RCC. In situ hybridisation was conducted in samples characterised by high (n=5) and low (n=5) miR-193b-3p expression at nCounter and RT–PCR analysis in patients with high preoperative eGFR. The expression of miR was detectable as a grainy blue cytoplasmic staining. In cases with low miR-193b expression, only faint miR-193b staining was observed in the collector ducts in the medulla, and in distal convoluted tubule and in glomerular endothelial cells in the cortex. High-miR-193b cases were characterised by a moderate to strong miR expression in the inflammatory infiltrate and fibroblasts present in both renal compartments. A significant miR-193b overexpression was observed in atrophic and swollen tubules and ducts within the medulla.