Signaling metabolite succinylacetone activates HIF-1α and promotes angiogenesis in GSTZ1-deficient hepatocellular carcinoma
Huating Luo, Qiujie Wang, Fan Yang, Rui Liu, Qingzhu Gao, Bin Cheng, Xue Lin, Luyi Huang, Chang Chen, Jin Xiang, Kai Wang, Bo Qin, Ni Tang
Huating Luo, Qiujie Wang, Fan Yang, Rui Liu, Qingzhu Gao, Bin Cheng, Xue Lin, Luyi Huang, Chang Chen, Jin Xiang, Kai Wang, Bo Qin, Ni Tang
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Research Article Oncology

Signaling metabolite succinylacetone activates HIF-1α and promotes angiogenesis in GSTZ1-deficient hepatocellular carcinoma

Abstract

Aberrant angiogenesis in hepatocellular carcinoma (HCC) is associated with tumor growth, progression, and local or distant metastasis. Hypoxia-inducible factor 1α (HIF-1α) is a transcription factor that plays a major role in regulating angiogenesis during adaptation of tumor cells to nutrient-deprived microenvironments. Genetic defects in Krebs cycle enzymes, such as succinate dehydrogenase and fumarate hydratase, result in elevation of oncometabolites succinate and fumarate, thereby increasing HIF-1α stability and activating the HIF-1α signaling pathway. However, whether other metabolites regulate HIF-1α stability remains unclear. Here, we reported that deficiency of the enzyme in phenylalanine/tyrosine catabolism, glutathione S-transferase zeta 1 (GSTZ1), led to accumulation of succinylacetone, which was structurally similar to α-ketoglutarate. Succinylacetone competed with α-ketoglutarate for prolyl hydroxylase domain 2 (PHD2) binding and inhibited PHD2 activity, preventing hydroxylation of HIF-1α, thus resulting in its stabilization and consequent expression of vascular endothelial growth factor (VEGF). Our findings suggest that GSTZ1 may serve as an important tumor suppressor owing to its ability to inhibit the HIF-1α/VEGFA axis in HCC. Moreover, we explored the therapeutic potential of HIF-1α inhibitor combined with anti–programmed cell death ligand 1 therapy to effectively prevent HCC angiogenesis and tumorigenesis in Gstz1-knockout mice, suggesting a potentially actionable strategy for HCC treatment.

Authors

Huating Luo, Qiujie Wang, Fan Yang, Rui Liu, Qingzhu Gao, Bin Cheng, Xue Lin, Luyi Huang, Chang Chen, Jin Xiang, Kai Wang, Bo Qin, Ni Tang

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Figure 5

Loss of GSTZ1 results in SA accumulation and HIF-1α activation.

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Loss of GSTZ1 results in SA accumulation and HIF-1α activation. (A) Sche...
(A) Schematic representation of the phenylalanine and tyrosine (Phe/Tyr) catabolic pathway (left) and the concentrations of SA in parental and GSTZ1-KO HepG2 cells (right). Data are shown as mean ± SEM (n = 6 in each group). (B) Western blot shows protein expression of HIF-1α and VEGFA in HepG2 cells and Huh7 cells treated with SA (0, 100, 200, 300, 500 μM) under normoxia for 48 hours. (C) Western blot shows cytoplasmic and nuclear protein expression of HIF-1α in HepG2 cells treated with SA (300 μM) for 48 hours. (D) Western blot shows protein expression of HIF-1α in HepG2 cells treated first with Phe (2.0 mM) or SA (300 μM) for 48 hours, then with NTBC (0, 4, 7, 14, 28 μg/mL) for the last 12 hours. (E) Western blot shows protein expression of HIF-1α and hydroxylated HIF-1α in GSTZ1-KO HepG2 cells treated with or without NTBC. (F) Western blot shows protein expression of HIF-1α and hydroxylated HIF-1α in GSTZ1-OE Huh7 cells treated with SA (300 μM) for 48 hours. (G and H) Migration by Transwell assays (scale bar = 10 μm). Data are shown as mean ± SEM (n = 3 in each group). (I and J) Tube formation assay. The original magnification of I and J is 10×. Data are shown as mean ± SEM (n = 3 in each group). Statistical analysis was performed using 2-tailed unpaired Student’s t test (A) or 1-way ANOVA with Tukey’s test (G–J); *P < 0.05, **P < 0.01.