Combination gene therapy using multiple immunomodulatory genes transferredby a defective infectious single-cycle herpes virus in squamous cell cancer

Herpes simplex type 2-defective infectious single-cycle (DISC) viruses are attenuated viruses that were originally produced as viral vaccines; however , these viruses are also efficient gene transfer vehicles. The main goals o f this study were to examine determinants of the gene transfer by using DIS C vi rus for squamous cancer and to evaluate the antitumoral efficacy of va ccination with tumor eel is modified by DISC viruses carrying a combination of immunomodulatory genes (interleukin-2 (IL-2), granulocyte-macrophage co lony-stimulating factor (CM-CSF), B7-1) in a model of squamous cell cancer (SCCVII) in C3H/HeJ mice. SCCVII cells transduced by DISC viruses (multipli city of infection of 10) carrying the IL-2 or CM-CSF gene produced nanogram quantities of IL-2 or GM-CSF per 10(6) cells. Irradiated (5,000 cGy, 10,00 0 cGy) cells secreted levels of CM-CSF or IL-2 that were comparable with no nirradiated cells. In vivo vaccination using tumor cells transduced ex vivo with DISC-IL2 or DISC-GMCSF resulted in protection against subsequent tumo r challenge (P <.01), with DISC-GMCSF-transduced, irradiated tumor cells sh owing the greatest effects (P <.001). Marked growth arrest also was noted i n established tumors after direct injection of DISC-GMCSF (P <.001). These data demonstrate that (a) DISC virus is capable of efficient gene transfer, (b) GM-CSF-secreting genetically modified tumor vaccine protects against t umor cell challenge and suppresses tumor growth, and (c) intratumoral injec tion of DISC-GMCSF significantly suppresses the growth of established tumor s. These results not only confirm clinically relevant gene transfer bur als o demonstrate that the gene transfer is an effective anti-cancer therapy.