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Signaling Metabolite Succinylacetone Activates HIF-1α and Promotes Angiogenesis in GSTZ1-Deficient Hepatocellular Carcinoma
57 Pages Posted: 5 Aug 2022
More...Abstract
Background: 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 microenvironment. However, how exactly HIF-1α stability is regulated by metabolites is unclear.
Methods: RNA sequencing (RNA-seq) was used to screen the target genes of glutathione S-transferase zeta 1 (GSTZ1). Western blotting, quantitative real-time PCR (RT-qPCR) and immunohistochemistry (IHC) were used to investigate GSTZ1, HIF-1α, PHD2, VEGFA expression levels in HCC cell lines and HCC tissues. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect succinylacetone (SA) and α-ketoglutarate (a-KG) levels. Surface plasmon resonance (SPR) was used to explore the specific binding of SA and PHD2. Protein stability and in vitro hydroxylation experiments were used to investigate the interaction of PHD2 and HIF-1α ODD domain caused by GSTZ1 deletion and SA accumulation. DEN/CCl4-induced HCC mouse model was applied to explore therapeutic potential of HIF-1α inhibitor combined with anti-PD-L1 therapy in Gstz1 -knockout mice.
Findings: We reported that GSTZ1 deficiency led to accumulation of SA, which is structurally similar to a-KG. SA competed with α-KG for 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 suggested 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-PD-L1 therapy to effectively prevent HCC angiogenesis and tumorigenesis in Gstz1-knockout mice.
Interpretation: Our study revealed that GSTZ1 deficiency promoted HCC angiogenesis via SA-mediated HIF-1α activation. Combination therapy with an HIF-1α inhibitor and anti-PD-L1 antibody may be a promising strategy for HCC treatment.
Funding: This work was supported by the National Natural Science Foundation of China (No. 81872270).
Declaration of Interest: No potential conflicts of interest were disclosed.
Ethical Approval: This study was approved by the Research Ethics Committee of Chongqing Medical University. All animal experiments were performed according to guidelines approved by the Institutional Animal Care and Use Committee of Chongqing Medical University. All mice were maintained under specific pathogen-free conditions at the Laboratory Animal Center of Chongqing Medical University
Keywords: Angiogenesis, Glutathione S-transferase zeta 1(GSTZ1), Oncometabolite Succinylacetone, PHD2, HIF-1α
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