Evaluation of Serum-Based microRNA Expression as a Non-Invasive Diagnostic Tool for Renal Cell Carcinoma (RCC)

Abstract

Background: Kidney cancer, mainly renal cell carcinoma (RCC), is one of the most aggressive urological malignancies with a low five-year survival rate in patients diagnosed with advanced stages < 12%. Limited availability of sensitive, non-invasive early-detection modalities is a significant challenge to overcome to improve patient outcomes. The remarkable stability of miRNAs in serum and deregulation of miRNAs in a tissue-specific manner make them promising liquid biopsy markers. Objectives: This study was designed to evaluate the differential expression of four serum-based miRNAs (miR-210, miR-21, miR-155 and miR-122) and to assess the individual and combinatorial diagnostic value of these miRNAs for distinguishing RCC from benign kidney disease and healthy individuals in an Iraqi cohort. We hypothesised that a panel combining hypoxia-associated (miR-210) and tumour-suppressor (miR-122) miRNAs would outperform single-marker approaches. Methods: 400 subjects were enrolled in the study, including 180 patients with histologically confirmed RCC, 120 patients with benign kidney lesions (BK) and 100 age- and sex-matched healthy controls (HC). miRNA was isolated from serum with miRNeasy Serum/Plasma Kit and quantitative real-time RT-PCR (qRT-PCR) was conducted using cel-miR-39 as an exogenous spike-in normaliser. The relative expression of miRNAs was determined by the 2 − ΔΔCt method. Inter-group comparisons were done by a one-way ANOVA with post hoc Tukey's HSD test; diagnostic performance was determined using receiver operating characteristic (ROC) analysis, and multivariable logistic regression was used to adjust the diagnostic model for age, BMI, hypertension and renal function. The study is reported in accordance with the STROBE statement for observational studies. Results: miR-210 was the most highly upregulated in RCC (5.80 ± 0.90-fold vs. HC; p < 0.001), and had the best diagnostic performance, with an area under the ROC curve (AUC) of 0.941 (95% CI: 0.913-0.969), and a sensitivity of 91.1% and a specificity of 88.3%. Other microRNAs that were significantly upregulated included miR-21 (AUC: 0.912) and miR-155 (AUC: 0.887), while miR-122 was significantly downregulated in RCC (0.31 ± 0.12-fold). The combined miR-210/miR-122 panel had an AUC of 0.968, significantly higher than the individual miRNAs. ANOVA showed that the differences among the groups were significant for all four miRNAs (F > 148.3; p < 0.001). Conclusions: The combination of miR-210, miR-21, miR-155, and miR-122 represents a promising, noninvasive diagnostic panel for renal cell carcinoma that discriminates RCC patients — including those with advanced-stage disease — from individuals with benign kidney disease and healthy controls. The miR-210/miR-122 combination showed the best discriminatory performance; however, in the absence of an external validation cohort these findings should be regarded as hypothesis-generating and require confirmation in independent, multicentre, prospective cohorts before any claim of screening or early-detection utility can be made.