The role of minocycline in the treatment of intracranial 9L glioma.

This study was designed to explore the question of whether minocycline, a semisynthetic tetracycline shown to inhibit tumor-induced angiogenesis, could control the growth of the rat intracranial 9L gliosarcoma. Minocycline was tested alone and in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in vivo. Treatment was started at the time of intracranial implantation of 9L gliosarcoma into male Fischer 344 rats, 5 days later, or after tumor resection. Minocycline was delivered locally with a controlled-release polymer or systemically by intraperitoneal injection. Systemic minocycline did not extend survival time. Local treatment with minocycline by a controlled-release polymer implanted at the time of tumor implantation extended median survival time by 530% (p < 0.001) compared to treatment with empty polymer. When treatment was begun 5 days after tumor implantation, minocycline delivered locally or systemically had no effect on survival. However, after tumor resection, treatment with locally delivered minocycline resulted in a 43% increase in median survival time (p < 0.002) compared to treatment with empty polymer. Treatment with a combination of minocycline delivered locally in a controlled-release polymer and systemic BCNU 5 days after tumor implantation resulted in a 93% extension of median survival time compared to BCNU alone (p < 0.002). In contrast, treatment with a combination of systemic minocycline and BCNU did not increase survival time compared to systemic BCNU alone. These results demonstrate that minocycline affects tumor growth when delivered locally and suggest that minocycline may be a clinically effective modulator of intracranial tumor growth when used in combination with a chemotherapeutic agent and surgical resection.