Benign and tumor parenchyma metabolomic profiles affect compensatory renal growth in renal cell carcinoma surgical patients

Abstract

Background and objectives: 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.

Design, setting, participants, and measurements: 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: Our analysis found 13 metabolites in the benign (e.g. L-urobilin, Variable Influence in Projection, VIP, score = 3.02, adjusted p = 0.017) and 163 metabolites in the malignant (e.g. 3-indoxyl-sulfate, VIP score = 1.3, adjusted p = 0.044) tissues that significantly associate with CRG. Benign/tumor fold change in metabolite abundances revealed three additional metabolites with that significantly positively associate with CRG (e.g. p-cresol sulfate, VIP score = 2.945, adjusted p = 0.033). At the pathway level, we show that fatty-acid oxidation is highly enriched with metabolites whose benign tissue abundances strongly positively associate with CRG, both pre-operatively and long term, whereas in the tumor tissue significant enrichment of dipeptides and benzoate (positive association), glycolysis/gluconeogenesis, lysolipid and nucleotide sugar pentose (negative associations) sub-pathways, were observed.

Conclusion: These data suggest that specific biological processes in the benign as well as in the tumor parenchyma strongly influence compensatory renal growth.

Fig 1. Compensatory renal growth surrogate- contra vs. ipsi-lateral benign kidney parenchyma volume.

Left upper panel represents a VC/VI fold change of ~1, i.e., a surrogate to no compensatory renal growth (CRG). Right upper panel represents a VC/VI fold change higher than 1, i.e., a surrogate to higher CRG. Lower panels show representative 3D images (Aquarius iNtuition Edition software, TeraRecon Inc. CA, USA). VC- Volume of contra lateral kidney, VI- Volume of ipsi-lateral kidney (tumor side), V-Tumor- tumor volume. Lower right 3D image was horizontally flipped to correspond to the illustration.

Fig 2. Association of metabolite abundances with compensatory renal growth (CRG).

The X-axis is the effect size of the association of metabolite abundance with CRG obtained from the OPLS analysis and the Y-axis is the OPLS VIP score. Panels A and B describe OPLS fit to metabolite abundances in benign and tumor tissue, respectively, with pre-operative CRG as response. Panel C describes OPLS fit to benign/tumor metabolite abundance fold change with pre-operative CRG as response. Panel D describes OPLS fit to metabolite abundances in benign tissue with LT-CRG as response. Statistically significant variables are defined as those with VIP score > 1 and FDR adjusted p-value (p’-value) < 0.05 and are colored red. Variables with VIP score > 1 and p’-value > 0.05 are colored orange, and the remaining variables are colored gray. Panel E describes the associations of a sample of metabolites with pre-operative CRG. Arrows facing up represent a positive association and arrows facing down represent a negative association. The pink arrow represents metabolites within the benign tissue, the blue arrow represents metabolites within the tumor tissue, and the pink arrow with the blue outline represents the benign/tumor metabolite fold-change.

Fig 3. Metabolic sub-pathways enriched in pre-operative compensatory renal growth (CRG).

The X-axis is the FDR adjusted p-value (p’-value) of the sub-pathway enrichment analysis, -10log10 transformed, and the Y-axis is the sub-pathway which the metabolites correspond to. In red shades are sub-pathways enriched in metabolites whose abundances are positively associated with CRG (“P” in the legend indicating positive), and in blue shades are sub-pathways enriched in metabolites whose abundances are negatively associated with CRG (“N” in the legend indicating negative). All other sub-pathways (indicated with “I” for invariant in the legend) are colored in gray. Panels A and B describe OPLS fit to metabolite abundances in benign and tumor tissue, respectively, with pre-operative CRG as response. Panel C describes OPLS fit to benign/tumor metabolite abundance fold-change with pre-operative CRG as response. Panel D describes OPLS fit to metabolite abundances in benign tissue with LT-CRG as response. Panel E describes a sample of sub-pathways enriched with metabolites strongly associated with pre-operative CRG. Arrows facing up represent sub-pathways enriched with metabolites with a positive association and arrows facing down represent sub-pathways enriched with metabolites with a negative association. The pink arrow represents sub-pathways enriched with metabolites within benign tissue, the blue arrows represent sub-pathways enriched with metabolites within the tumor tissue, and the pink arrows with the blue outline represent sub-pathways enriched with metabolites from the benign/tumor metabolite fold-change.