IL-10 gene transfer to intracranial 9L glioma: Tumor inhibition and cooperation with IL-2

This study examines the effects of interleukin-10 (IL-10) and combination IL-10 + IL-2 gene transfer on experimental brain tumor growth in vivo. 9L gliosarcoma cells were engineered to stably express murine IL-10 (9L-IL-10 cells) and implanted subcutaneously or to the caudate/putamen of syngeneic rats. The growth of tumors expressing IL-10 was substantially reduced compared to that of control tumors (p < 0.05). Intracranial tumors expressing IL-10 and IL-2 were established by co-implanting 9L-IL-10 cells with endothelial cells engineered to express IL-2. At 14 days post- implantation, tumors expressing IL-10 + IL-2 were 99% smaller than control- transfected tumors (p < 0.0001). This extent of anti-tumor effect could not be achieved by expression of IL-10 or IL-2 alone within tumors. Neither IL- 10 nor a combination of IL-10 + IL-2 gene delivery inhibited tumor growth in severe combined immunodeficient (SCID-Beige) mice (p > 0.05). Immunohistochemical analysis revealed that IL-10 + IL-2 gene delivery markedly increased T-cell infiltration within the striatum ipsilateral to tumor cell implantation. These findings establish that IL-10 expression, particularly in combination with IL-2 expression, can have significant immune-dependent anti-tumor actions within intracranial gliomas.