Urinary Metabolomics Validates Metabolic Differentiation Between Renal Cell Carcinoma Stages and Reveals a Unique Metabolic Profile for Oncocytomas

Abstract

Renal cell carcinoma (RCC) is a heterogeneous malignancy which often develops and progresses asymptomatically. Benign oncocytomas are morphologically similar to malignant chromophobe RCC and distinguishing between these two forms on cross-sectional imaging remains a challenge. Therefore, RCC-specific biomarkers are urgently required for accurate and non-invasive, pre-surgical diagnosis of benign lesions. We have previously shown that dysregulation in glycolytic and tricarboxylic acid cycle intermediates can distinguish benign lesions from RCC in a stage-specific manner. In this study, preoperative fasting urine samples from patients with renal masses were assessed by ¹H nuclear magnetic resonance (NMR). Significant alterations in levels of tricarboxylic acid cycle intermediates, carnitines and its derivatives were detected in RCC relative to benign masses and in oncocytomas vs. chromophobe RCC. Orthogonal Partial Least Square Discriminant Analysis plots confirmed stage discrimination between benign vs. pT1 (R2 = 0.42, Q2 = 0.27) and benign vs. pT3 (R2 = 0.48, Q2 = 0.32) and showed separation for oncocytomas vs. chromophobe RCC (R2 = 0.81, Q2 = 0.57) and oncocytomas vs. clear cell RCC (R2 = 0.32, Q2 = 0.20). This study validates our previously described metabolic profile distinguishing benign tumors from RCC and presents a novel metabolic signature for oncocytomas which may be exploited for diagnosis before cross-sectional imaging.

Involvement of Tricarboxylic Acid Cycle Metabolites in Kidney Diseases

“…Similarly, in AKI pediatric patients, urinary citrate levels were found to be reduced [ 174 ]. In RCC, citrate levels decreased in urine [ 175 ], but these are enriched in tissue [ 62 ]. Hence, reduced citrate levels in urine seem to be a promising biomarker of altered kidney function.…”

“…In CKD patients, decreased urinary levels of succinate have been reported [ 42 ], and plasma succinate correlates negatively with eGFR [ 51 ]. In RCC, succinate levels are increased in tissue [ 62 ] and decreased in urine [ 175 ]. However, there is no information related to alterations of this metabolite in urine or serum from AKI patients.…”

Urine-Based Metabolomics and Machine Learning Reveals Metabolites Associated with Renal Cell Carcinoma Stage

“…This dysregulation is required to maintain cell proliferation processes that characterize tumors, and therefore differences in metabolite abundances in this pathway are expected as the tumor progresses. The abundance of citrate has been reported to decrease in urine metabolomics studies comparing healthy controls or benign with malignant RCC tumors [ 46 , 47 ]. Citrate has also been linked to drive increased fatty acid synthesis in tumors [ 48 ], and the overexpression of ATP citrate lyase has been reported as RCC progresses [ 49 ].…”

“…ATP citrate lyase links carbohydrate metabolism to fatty acid biosynthesis via the conversion of citrate to acetyl-CoA. In addition, elevated pyruvate levels, another evidence of dysregulated glucose metabolism, were reported in a urine metabolomics study that compared benign RCC tumors with malignant RCC [ 47 ]. The lower levels of glycine abundance in advanced RCC urine samples agree with the role of glycine in rapid cancer cell proliferation [ 50 , 51 , 52 , 53 ].…”

In Situ Metabolomics Expands the Spectrum of Renal Tumours Positive on 99mTc-sestamibi Single Photon Emission Computed Tomography/Computed Tomography Examination

“…In fact, only a small number of biomarkers are actually shared between different analytical platforms and biological specimens [30] . Towards metabolic differentiation between chRCCs and ROs, urinary metabolomics highlighted citrate, carnitine, transaconitate, succinate, and π-methylhistidine [31] , while tissue metabolomics revealed glycolysis and pentose phosphate pathway intermediates along with certain gamma-glutamyl amino acids as differential metabolites [25] .…”