Frequent detection of human cytomegalovirus in neuroblastoma: A novel therapeutic target?

Neuroblastoma is the most common and deadly tumor of childhood, where new therapy options for patients with high-risk disease are highly warranted. Human cytomegalovirus (HCMV) is prevalent in the human population and has recently been implicated in different cancer forms where it may provide mechanisms for oncogenic transformation, oncomodulation and tumor cell immune evasion. Here we show that the majority of primary neuroblastomas and neuroblastoma cell lines are infected with HCMV. Our analysis show that HCMV immediate-early protein was expressed in 100% of 36 primary neuroblastoma samples, and HCMV late protein was expressed in 92%. However, no infectious virus was detected in primary neuroblastoma tissue extracts. Remarkably, all six human neuroblastoma cell lines investigated contained CMV DNA and expressed HCMV proteins. HCMV proteins were expressed in neuroblastoma cells expressing the proposed stem cell markers CD133 and CD44. When engrafted into NMRI nu/nu mice, human neuroblastoma cells expressed HCMV DNA, RNA and proteins but did not produce infectious virus. The HCMV-specific antiviral drug valganciclovir significantly reduced viral protein expression and cell growth both in vitro and in vivo. These findings indicate that HCMV is important for the pathogenesis of neuroblastoma and that anti-viral therapy may be a novel adjuvant treatment option for children with neuroblastoma. What's new? Relapse and invasiveness of neuroblastoma, a frequently fatal cancer of early childhood, may be linked to the presence of human cytomegalovirus (HCMV), one of the most common congenital viral infections known. In this study, HCMV was observed in primary neuroblastoma tumors and in six neuroblastoma cell lines. Although no infectious virus was isolated from tumors, the HCMV-specific drug valganciclovir significantly reduced viral protein expression and tumor cell growth both in vitro and in vivo. The results suggest that HCMV may be important in the pathogenesis of neuroblastoma and that antiviral therapy may represent a possible future treatment option for affected children. We have shown that all examined primary neuroblastoma tumors and six neuroblastoma cell lines were infected with HCMV, but no infectious virus was isolated from tumors. The HCMV-specific drug Valganciclovir significantly reduced viral protein expression and tumor cell growth in vitro and in vivo. Thus, HCMV may be important in the pathogenesis of neuroblastoma and anti-viral therapy may provide a novel treatment option for children with neuroblastoma.