DISC-GMCSF (GM-CSF Gene Transduced Defective Infectious Single Cycle Herpes Virus) Gene Therapy in the Established SCCVII squamous cell carcinoma model

Kim, Se Heon; Choi, Eun Chang; Hong, Won Pyo; Yoon, Hyun Chul; Oh, Jong Seok

Abstract

BACKGROUND AND OBJECTIVES: Over the past five years, preclinical studies evaluating viral-vector-mediated gene transfer in the treatment of head and neck cancer have reported promising results. The main goal of this study was to evaluate the efficacy of intra-tumoral treatment with DISC virus (defective infectious single cycle herpes virus) carrying a GM-CSF immunomodulatory genes as cancer gene therapy. MATERIALS AND METHOD: Using the SCCVII squamous cell carcinoma model, we determined the in vivo GM-CSF production by ELISA method and evaluated the in vivo effects of DISC-GMCSF on the established tumor model. One of the following preparations was injected every two days to a total of three-doses intratumorally: group I (control): PBS alone, group II: heat inactivated DISC-GMCSF, group III: DISC-GMCSF. To prove the specific anti-tumor response, we analyzed the surface phenotype of tumor infiltrating cells. A flow cytometric analysis was performed using FACScan.
RESULTS
Clinically relevant gene transfer could be possible by direct injection of tumors in situ. Intratumoral injection of the DISC-GMCSF (GM-CSF gene transduced defective infectious single cycle herpes virus) resulted in effective in vivo production of cytokines (4,500 pg/0.5 g tumor tissue), but as the progeny of the DISC virus could not be infected by other host cells, the effective cytokine production time seems limited. However, the DISC vector was safe and also allowed to be administered repeated treatments as needed. Effects of DISC-GMCSF injection on tthe established syngeneic tumor model showed the greatest inhibition of tumor growth in the DISC-GMCSF treated group (control vs DISC-GMCSF, p<0.01). In contrast to this, heat inactivated DISC-GMCSF showed no significant tumor suppression effect. It was interesting to note from our in vivo analysis of tumor infiltrating cells that treatment of flank tumors with the DISC-GMCSF virus resulted in a significant increase in the percentage of CD8 positive cells within the tumor (control vs DISC-GMCSF, p<0.05).
CONCLUSION
Intratumoral injection of DISC-GMCSF significantly suppressed the tumor growth in established tumor model and induced intratumoral increase in immune effector cells. The results not only confirmed clinically relevant gene transfer but also demonstrated the gene transfer to be an effective anti-cancer therapy.