Loss of ANGPTL4 is associated with enrichment for lipid metabolism genes. A, Volcano plot for CAKi1 A4KO versus WT cells. Genes with an absolute value log2 fold change ≥1 and an adjusted P value of ≤0.05 are indicated. Genes upregulated in A4 KO cells are red and genes downregulated in A4KO cells are blue. B, GSEA was performed for CAKi-1 A4KO and WT cells. Graph depicts the nominal enrichment score (NES) of gene sets related to metabolism that were enriched—had a FDR <0.25—with A4KO cells. The nominal P value is indicated by the heat bar. Gray bars had a nominal P value that was lower than the threshold for the package used and thus had a value of 0. C, Enrichment plot for the indicated gene set from the GSEA analysis in B. The FDR and nominal P value are indicated. D, Heatmap of the genes in the gene set from C, for CAKi-1 A4KO and WT cells. E, GSEA analysis was performed for 786O A4KO and WT cells. Enrichment plot for the indicated gene set showing enrichment in A4KO cells. The FDR and nominal P value are indicated. F, Graphs depict the average mRNA expression relative to PPIA of the indicated genes in CAKi-1 WT and A4KO cells ± SD. Welch’s t test was done to determine significance.
ARTICLE ABSTRACT
Renal cell carcinoma (RCC), the most common form of kidney cancer, is a heterogeneous disease with clear cell RCC (ccRCC) being the most prevalent and aggressive subtype. While most ccRCC tumors have elevated expression of angiopoietin-like4 (ANGPTL4), in our study we identified a significant subset of patients whose cancers show no increase in ANGPTL4 expression. These patients have a worse prognosis compared to the patients with high expression of ANGPTL4. These ANGPTL4-low cancers are characterized by the increased frequency of wild-type Von Hippel-Lindau(WT VHL), a gene that is commonly mutated in ccRCC, and an enrichment for genes associated with lipid metabolism. Using RCC tumor models with WT VHL, we demonstrate that ANGPTL4 behaves as a tumor suppressor. The loss of ANGPTL4 in ccRCC cell lines results in increased tumor growth and colony formation in a lysosomal acid lipase (LAL)-dependent manner, a phenotype rescued by the expression of N-terminus ANGPTL4. At the mechanistic level, the loss of ANGPTL4 increases LAL activity in ccRCC cells. These data suggest that ANGPTL4 enacts its tumor-suppressive effects in ccRCC by regulating LAL activity. Importantly, the identified patient cohort with low ANGPTL4 expression may exhibit increased reliance on lipid metabolism, which can be a point of target for future therapy.
Our data indicate angiopoietin-like 4 (ANGPTL4) acts as a tumor suppressor in clear cell renal cell carcinoma via regulating lipid metabolism and identifies a cohort of patients with lower expression of ANGPTL4 that are correlated with shorter survival.
