Context: Head and neck paragangliomas (HNPGLs) arise from parasympathetic paraganglias and 35% to 45% are hereditary caused by mutations in succinate dehydrogenase (SDH) genes. The connection between SDH and tumor development is unclear. The most accepted hypothesis proposes a central role for the pseudohypoxic (pHx) pathway activated by hypoxia-inducible factor (HIF). Paradoxically, we showed that activation of HIF in HNPGLs is restricted to a subset of HNPGLs lacking SDH mutations. These tumors overexpress HIF-1α protein and target genes and the HIF-inducible microRNA miR-210 (pHx-HNPGLs).
Objective: The present study aimed at unraveling the SDH-independent mechanisms involved in the activation of HIF in HNPGLs.
Design: The VHL gene was analyzed in 53 tumors by gene sequencing, multiplex-ligation-dependent probe amplification, and quantitative PCR. The miR-210, HIF-1α, and CA9 levels were used as markers of the pHx gene signature. Meta-analysis of the transcriptome of pHx-HNPGLs was performed using the Oncomine platform. Assays in cells lacking functional pVHL and HIF-1α were performed to analyze the role of pVHL/HIF-1α on miR-210 expression.
Results: We identified, for the first time, somatic VHL mutations in HNPGLs. These were found in 2 of 4 pHx-HNPGLs with concomitant loss of heterozygosity in one of them; but not in non-pHx-HNPGLs. Meta-analysis of the transcriptome of pHx-HNPGLs revealed that these tumors are highly related to clear cell renal cell carcinoma. Cell-based assays showed that loss of pVHL lead to upregulation of miR-210 mainly via HIF-1α activation.
Conclusions: VHL, involved in tumorigenesis of PGLs and clear cell renal cell carcinomas, may be an important player in the pathogenesis of sporadic HNPGLs via activation of an HIF-1α/miR-210 pHx pathway.