Influenza Virus Induces Apoptosis in Osteosarcoma Cells
K Suzuki, M Kanamori, T Yasuda, T Hori, T Kimura. University of Toyama, Toyama, Japan
Background: Osteosarcoma (OS) is the most frequent primary malignant bone tumor in young adults and adolescents. Despite recent advances in multimodality treatment comprising aggressive adjuvant chemotherapy and wide local excision, pulmonary metastasis occurs in approximately 30% of patients with OS and remains a major cause of fatal outcome. Among the number of naturally occurring viruses being investigated as oncolytic agents for cancer treatment, a strain of influenza virus has been reported to induce apoptosis in numerous cell types. In this study, we analyzed susceptibility of human OS cell lines to apoptosis after influenza virus infection in vitro.
Design: Three OS cell lines MG63, HOS and Saos2 were infected with influenza A/Aichi/2/68 (Aichi) virus. We assessed the susceptibility of OS cells to Aichi virus by plaque assay and the growth of OS cells infected with Aichi virus by MTT assay. To detect apoptotic cells after infection with Aichi virus, TUNEL assay was performed and we examined caspase-3 activation by Western blotting analysis.
Results: Aichi virus replicated in MG63, HOS and Saos2, and formed plaques on MDCK cell monolayers. Aichi virus induced cytopathic effects in MG63 cells at 48 hours after viral infection. The viability of MG63 cells infected with Aichi virus was reduced more significantly at a multiplicity of infection (MOI) of 10 when compared to MOIs of 1 and 5. TUNEL-positive MG63 cells were observed at 48 hours after Aichi virus infection and were significantly more numerous at an MOI of 10 when compared to MOIs of 1 and 5. Western blotting analysis showed that protein levels of caspase-3 (35 kDa) were lower, and cleaved caspase-3 (19 and 17 kDa) was observed in MG63 cells infected with Aichi virus at an MOI of 10.
Conclusions: We confirmed the susceptibility of human OS cells to apoptosis induction by Influenza A/Aichi/2/68. To date, the influenza A virus has been explored as an oncolytic virus. The NS1 protein is a virulence factor that counteracts the PKR-mediated antiviral response of the host. As a consequence, influenza virus lacking the NS1 open reading frame fails to replicate in normal cells, but produces infectious particles in PKR-deficient cells. The oncolytic properties of this mutant virus are dependent on activated Ras, as oncogenic Ras induces an inhibitor of PKR. It may be possible to use the influenza virus as an agent for oncolytic virotherapy in OS.
Category: Bone & Soft Tissue
Tuesday, March 23, 2010 9:30 AM
Poster Session III # 15, Tuesday Morning