Fat Tissue Lipid Fuels Kidney Cancer Growth Through a Novel Metabolic Signaling Chain

Clear cell renal cell carcinoma (ccRCC) is defined histologically by massive intracellular lipid droplet accumulation, yet the upstream signals driving this metabolic reprogramming have remained poorly characterized. This study from Yue et al. (2025) addressed a specific gap: how does the peritumoral fat pad (perinephric adipose tissue, PAT) surrounding kidney tumors communicate metabolic signals that actively promote cancer growth?

Using paired tissue and blood samples from ccRCC patients, the team performed multiomics metabolomic profiling of PAT, subcutaneous adipose tissue (SAT), tumor tissue, and arterial/venous renal blood. They found that PAT adjacent to ccRCC tumors undergoes 'browning'—a thermogenic transformation marked by elevated UCP1, PGC1-α, and PRDM16 expression. This browning is associated with elevated production of lysophosphatidylethanolamine 18:1 (LPE18:1), a bioactive lipid enriched in PAT and renal arterial blood but notably depleted within tumor tissue, suggesting active consumption by ccRCC cells. Tumor cells consumed exogenous LPE18:1 significantly faster than normal kidney epithelial cells.

Functional experiments demonstrated that LPE18:1 promotes ccRCC proliferation, lipid droplet deposition, and mitochondrial energy production in a dose-dependent manner. Through RNA sequencing and proteomics, CAPZA1 (an F-actin capping protein) was identified as a key downstream effector upregulated by LPE18:1. CAPZA1 was found to recruit the deubiquitinase USP48, which stabilizes SIRT6 by blocking its proteasomal degradation. Elevated SIRT6 then epigenetically activates ACAT2, a cholesterol esterification enzyme, driving free cholesterol accumulation—the metabolic signature of aggressive ccRCC.

Clinically, CAPZA1 and SIRT6 levels correlated with advanced tumor stage and poor patient prognosis across ccRCC cohorts. Pharmacological inhibition using the SIRT6 inhibitor OSS-128167, combined with CAPZA1 depletion, significantly suppressed ccRCC cell growth in xenograft mouse models, demonstrating translational potential. The CAPZA1/USP48/SIRT6/ACAT2 axis represents a fully novel, druggable signaling cascade connecting the tumor microenvironment's lipid output to intratumoral metabolic rewiring.

Caveats include the primarily preclinical nature of therapeutic interventions, reliance on cell line and xenograft models without immunocompetent systems, and the need for prospective clinical validation of LPE18:1, CAPZA1, and SIRT6 as biomarkers. The mechanisms by which LPE18:1 specifically upregulates CAPZA1 at the receptor or membrane level also remain to be fully elucidated.