Oncolytic herpes simplex virus mutants are more efficacious than wild-type adenovirus Type 5 for the treatment of high-risk neuroblastomas in preclinical models.

Background: High-risk neuroblastoma (Nb) is incurable using current treatment regimens in the majority of patients. Oncolytic virotherapy is a novel approach being tested for several types of adult cancers.

Objectives: To compare the susceptibility of Nb tumor models to oncolytic adenovirus and HSV mutants and delineate the mechanisms of resistance or sensitivity.

Methods: Human Nb cell lines were used to determine susceptibility to adenovirus type 5 wild-type and HSV1 mutant (NV1066) infection, adenovirus receptor expression, support of NV1066 replication, and induction of apoptosis. Human xenograft tumors in immunodeficient mice were evaluated for histological effects and tumor response to intratumoral injection of an oncolytic HSV mutant.

Results: All eight Nb cell lines tested in culture were relatively resistant to infection with wild type and attenuated adenoviruses. Cells expressed the cocksackie-adenovirus attachment receptor (CAR) but had low or absent expression of the internalization receptors (alphavbeta3, alphavbeta5 integrins). In contrast, all cells were uniformly sensitive to infection with the attenuated HSV mutant, NV1066. Productive virus replication and induction of apoptosis were observed in HSV-infected cells. CHLA-20 and LAN-5 xenograft tumors injected with a single dose of NV1066 showed a significant antitumor response, and the animals had a prolonged survival post infection in comparison to the PBS-treated control group. HSV injected tumors showed extensive areas of necrosis and morphologic evidence of apoptosis.

Conclusions: Nb tumor models are resistant to adenovirus mediated oncolysis but highly sensitive to HSV mediated oncolysis. Further studies of HSV virotherapy as a novel treatment for Nb are warranted.