Enhanced anti-cancer activity of microglia by AAV2-mediated IL-12 in the therapy of glioblastoma multiforme

Abstract

Microglia has been found to diversify its function by cancerous cells or in a cancerous environment, thereby contributing to cancer growth and metastasis. Its immuno-activity, however, can be modulated by interleukin-12. So a strategy was designed using AAV2 carrying IL-12 to activate microglia then to eliminate cancerous cells. The transduction efficacy of AAV was evaluated with AAV2 encoding GFP and IL-12 on cancerous and CNS cells. The bioactivity of microglia modulated by IL-12 was examined and death receptors 4 and 5 were detected on cancerous cells. The effects of IL-12 and AAV2/IL-12 on microglial cytoxoxicity were evaluated too. The results demonstrated human cell line DBTRG, surgical specimen of GBM, and rat astrocyte expressed GFP quite well. Tremendous IL-12 secretion was detected in DBTRG, RG2, and astrocyte after transfection of AAV2/IL-12. TRAIL releasing and phagocytotic activity of microglia were significant, increasing (p<0.05) after the stimulation of IL-12. DR4 and DR5 were expressed in all of the examined GBM cells. MTT assay of microglial cytotoxicity elicited significant increase (p<0.05) when the IL-12 protein or RG2-secreting IL-12 could have contact with microglial cells. Conclusively, AAV2 is an effective vector in transferring therapeutic genes such as IL-12 to induce or enhance microglial anti-cancer activity.