Decreased expression of cystathionine β-synthase promotes glioma tumorigenesis
Naoharu Takano1, Yasmeen Sarfraz2, Daniele M Gilkes3
1Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland. McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland. Department of Biochemistry, School of Medicine, Keio University, Tokyo, Japan.
Unlabelled:
Cystathionine β-synthase (CBS) catalyzes metabolic reactions that convert homocysteine to cystathionine. To assess the role of CBS in human glioma, cells were stably transfected with lentiviral vectors encoding shRNA targeting CBS or a nontargeting control shRNA, and subclones were injected into immunodeficient mice. Interestingly, decreased CBS expression did not affect proliferation in vitro but decreased the latency period before rapid tumor xenograft growth after subcutaneous injection and increased tumor incidence and volume following orthotopic implantation into the caudate-putamen. In soft-agar colony formation assays, CBS knockdown subclones displayed increased anchorage-independent growth. Molecular analysis revealed that CBS knockdown subclones expressed higher basal levels of the transcriptional activator hypoxia-inducible factor 2α (HIF2α/EPAS1). HIF2α knockdown counteracted the effect of CBS knockdown on anchorage-independent growth. Bioinformatic analysis of mRNA expression data from human glioma specimens revealed a significant association between low expression of CBS mRNA and high expression of angiopoietin-like 4 (ANGPTL4) and VEGF transcripts, which are HIF2 target gene products that were also increased in CBS knockdown subclones. These results suggest that decreased CBS expression in glioma increases HIF2α protein levels and HIF2 target gene expression, which promotes glioma tumor formation.
Implications:
CBS loss-of-function promotes glioma growth.
Insights
Reduced cystathionine β-synthase (CBS) expression promotes human glioma growth by increasing hypoxia-inducible factor 2α (HIF2α) and its target genes, driving tumor formation and progression.
Area of Science:
- Neuro-oncology
- Cancer Metabolism
- Molecular Biology
Background:
- Cystathionine β-synthase (CBS) is crucial for homocysteine metabolism.
- The role of CBS in human glioma pathogenesis is not well understood.
Purpose of the Study:
- To investigate the role of CBS in human glioma development and progression.
- To elucidate the molecular mechanisms by which CBS influences glioma growth.
Main Methods:
- Stable transfection of human glioma cells with shRNA targeting CBS.
- In vitro proliferation and soft-agar colony formation assays.
- Subcutaneous and orthotopic xenograft implantation in immunodeficient mice.
- Molecular analysis of hypoxia-inducible factor 2α (HIF2α) and its target genes.
- Bioinformatic analysis of human glioma mRNA expression data.
Main Results:
- Decreased CBS expression did not impact in vitro proliferation but accelerated tumor xenograft growth.
- CBS knockdown increased tumor incidence and volume in orthotopic models.
- CBS knockdown led to increased anchorage-independent growth and elevated HIF2α levels.
- HIF2α knockdown mitigated the effects of CBS knockdown on anchorage-independent growth.
- Low CBS mRNA correlated with high expression of HIF2α target genes (ANGPTL4, VEGF) in human glioma specimens.
Conclusions:
- Loss-of-function of CBS promotes glioma growth and tumor formation.
- Decreased CBS expression enhances glioma aggressiveness through increased HIF2α signaling.
- CBS may represent a potential therapeutic target in glioma.
