Paragangliomas (PGLs) are neurovascular autonomic nervous system tumors, still incurable when radical surgery is not possible. They are frequently associated with susceptibility mutations in genes encoding the mitochondrial SDH complex components. However, the etiology of PGLs remains unclear as the penetrance of SDHx mutations is incomplete (21% at age 50). Studying a large set of freshly- collected head and neck PGLs (HNPGLs) by electron microscopy we found herpesvirus-like particles in all tumors. These were similar to particles attributed to cytomegalovirus (HCMV) reported in 1971 by Heine et al. in a retroperitoneal PGL. MATERIALS AND METHODS The HNPGL series of over 140 collected cases was characterized for SDHx mutational status and HCMV virus infection. The germline point mutations and large deletion/rearrangements of the SDHx genes were analysed by PCR, sequencing and MLPA. Blood and tumor DNAs were analysed for HCMV sequences using PCR. Tumor tissues were analysed by RISH, EM, IF, IHC and WB. Viral infection using HNPGL tumor extracts was assessed in vitro using a modified protocol of Peyton-Rous (1911). HNPGL derived cells were treated by the antiviral Ganciclovir in vitro and in vivo. RESULTS SDHx mutational analysis showed a mutation frequency of 34.3%. Viral particles were observed in all analysed cases by EM. The HCMV reactive proteins (IE, gB, pp65, vMIA) and their interacting host proteins (PDGFRA, viperin) were detected by IF, IHC and WB. In our attempts to amplify the viral DNA using HCMV-specific primers, we detected viral glycoprotein B for only 68.2% and 82.3% in tumors and in blood samples respectively. Viral infection using HNPGL in HEK293T and MRC5 cell lines induced cell fusion and cell death. Moreover, cell-derived xenografts presented the same viral particles and HCMV sequences were retrievable from the blood of xenografted mice. Ganciclovir inhibited HNPGL cell growth and prevented tumor xenograft formation (P=0.005). CONCLUSION Infection with this virus appears to be a constitutive feature of PGL, found in all cases, both associated, or not with germline SDHx mutations. Coherently with emerging evidence concerning other neural cancers, our data suggest that HCMV-like virus plays a role in the PGL pathogenesis, possibly favoured by germline mutations predisposing to oncogenic infection.
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