Effect of benign and tumor parenchyma metabolomic profiles on compensatory renal growth in renal cell carcinoma surgical patients.

446 Background: Pre-operative kidney volume is an independent predictor of glomerular filtration rate in renal cell carcinoma patients. Compensatory renal growth (CRG) can ensue prior to nephrectomy in parallel to tumor growth and benign parenchyma loss. We aimed to test whether renal metabolite abundances significantly associate with CRG, suggesting a causative relationship. Methods: Tissue metabolomics data from 49 patients, with a median age of 60 years, were previously collected and the pre-operative fold-change of their contra to ipsi-lateral benign kidney volume served as a surrogate for their CRG. Contra-lateral kidney volume fold-change within a 3.3 +/- 2.1 years follow-up interval was used as a surrogate for long-term CRG. Using a multivariable statistical model we identified metabolites whose abundances significantly associate with CRG. Results: We identified 13 metabolites in the benign (e.g. L-urobilin) and 163 metabolites in the malignant (e.g. 3-indoxyl-sulfate) tissues to significantly associate with CRG. Benign/tumor fold change in metabolite abundances revealed three additional metabolites with a significant positive association with CRG (e.g. p-cresol sulfate). At the pathway level, we show that fatty-acid oxidation is highly enriched with metabolites whose benign tissue abundances strongly positively associate with CRG, whereas in the tumor tissue significant enrichment of dipeptides (positive association) and benzoate, glycolysis/gluconeogenesis, lysolipid and nucleotide sugar pentose (negative associations) sub-pathways were observed. The effect of metabolite abundances in the benign tissue on long term CRG provided further support for positive association of fatty-acid metabolism sub-pathway enrichment, where sphingolipid, monoacylglycerol, long chain fatty acids, and mid chain fatty acids were enriched for a negative association. Conclusions: These data suggest that specific biological processes in the benign as well as in the tumor parenchyma strongly influence compensatory renal growth.