Irinotecan: a potential new chemotherapeutic agent for atypical or malignant meningiomas.

OBJECT: There is currently no effective chemotherapy for meningiomas. Although most meningiomas are treated surgically, atypical or malignant meningiomas and surgically inaccessible meningiomas may not be removed completely. The authors have investigated the effects of the topoisomerase I inhibitor irinotecan (CPT-11) on primary meningioma cultures and a malignant meningioma cell line in vitro and in vivo. METHODS: The effects of irinotecan on cellular proliferation in primary meningioma cultures and the IOMM-Lee malignant meningioma cell line were measured by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide assay and flow cytometry. Apoptosis following drug treatment was evaluated by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and the DNA laddering assays. The effects of irinotecan in vivo on a meningioma model were determined with a subcutaneous murine tumor model using the IOMM-Lee cell line. Irinotecan induced a dose-dependent antiproliferative effect with subsequent apoptosis in the primary meningioma cultures (at doses up to 100 microM) as well as in the IOMM-Lee human malignant meningioma cell line (at doses up to 20 microM) irinotecan. In the animal model, irinotecan treatment led to a statistically significant decrease in tumor growth that was accompanied by a decrease in Bcl-2 and survivin levels and an increase in apoptotic cell death. CONCLUSIONS: Irinotecan demonstrated growth-inhibitory effects in meningiomas both in vitro and in vivo. Irinotecan was much more effective against the malignant meningioma cell line than against primary meningioma cultures. Therefore, this drug may have an important therapeutic role in the treatment of atypical or malignant meningiomas and should be evaluated further for this purpose.

Efficacy of celecoxib in the treatment of CNS lymphomas: an in vivo model.

OBJECT: The incidence of primary central nervous system lymphomas (PCNSLs) has increased over the past several decades. Unfortunately, even with the most effective therapeutic regimen (that is, methotrexate with wholebrain radiation therapy), PCNSL recurs within a few years in more than half of the treated patients and is eventually fatal. Because PCNSL usually occurs in older patients and in those with acquired immunodeficiency syndrome, combination treatments in which both chemo- and radiation therapy are used is often poorly tolerated and results in a significant reduction in the quality of life. Recently, it has been demonstrated that the selective cyclooxygenase- 2 inhibitor celecoxib (Celebrex), can block the growth of lymphoma cells in vitro. METHODS: To create an experimental animal model in vivo for the PCNSL study, the authors intracranially injected a human B-cell lymphoma cell line into nude mice. Their data demonstrate that this experimental model is an excellent one for human PCNSL with brain and leptomeningeal involvement. They also evaluated the feasibility of using celecoxib as a therapeutic agent in the treatment of PCNSL. Nude mice with intracranial lymphomas were treated with celecoxib contained in the animal chow. The treated animals demonstrated significantly prolonged survival times compared with the untreated animals. CONCLUSIONS: Based on the authors' data, celecoxib may be a promising therapeutic agent for the treatment of PCNSL.

Enhancement of glioblastoma cell killing by combination treatment with temozolomide and tamoxifen or hypericin.

OBJECT: The chemotherapeutic agent temozolomide has demonstrated antitumor activity in patients with recurrent malignant glioma. Because responses are not enduring and recurrence is nearly universal, further improvements are urgently needed. METHODS: In an effort to increase the clinical activity of temozolomide, the authors investigated whether its antitumor activity could be enhanced by adding tamoxifen or hypericin, two drugs that are known to inhibit the activity of protein kinase C. Human glioblastoma multiforme cell lines A172 and LA567 were treated with combinations of temozolomide and tamoxifen or hypericin in vitro, and cell survival was analyzed using various methods. Tamoxifen and hypericin were able to greatly increase the growth-inhibitory and apoptosis-stimulatory potency of temozolomide via the downregulation of critical cell cycle-regulatory and prosurvival components. Furthermore, with the use of an in vivo xenograft mouse model, the authors demonstrated that hypericin was able to enhance the antiglioma effects of temozolomide in the in vivo setting as well. CONCLUSIONS: Taken together, analysis of the results indicated that combination therapy involving temozolomide and tamoxifen or hypericin potently inhibited tumor growth by inducing apoptosis and provided an effective means of treating malignant glioma.

Interleukin-8 differentially regulates migration of tumor-associated and normal human brain endothelial cells.

Interleukin-8 (IL-8) is a chemokine involved in angiogenesis, a process vital to tumor growth. Previously, we showed that endothelial cells derived from human tumor tissue have different functional and phenotypic properties compared with normal endothelial cells. This study analyzes the role of IL-8 in regulating angiogenesis of tumor-associated brain endothelial cells (TuBEC). Results show that TuBECs have a higher baseline migration rate compared with normal brain endothelial cells (BEC). TuBECs are unaffected when stimulated with IL-8 whereas BECs are activated. This lack of response of TuBECs to IL-8 is due to the constitutive production of IL-8. Endogenously produced IL-8 activates TuBECs in an autocrine manner as shown by IL-8 receptor inhibition. Blocking either CXCR1 or CXCR2 partially reduces TuBEC migration, whereas blocking both receptors further reduces migration. Treatment with antibody against vascular endothelial growth factor (VEGF) shows that production of IL-8 by TuBECs is dependent on VEGF. Transforming growth factor-beta1 (TGF-beta1), shown to down-regulate IL-8 production in BECs, does not inhibit IL-8 production in TuBECs. In summary, these studies show that TuBECs constitutively secrete IL-8 and autocrine activation by IL-8 is the result of VEGF stimulation. Furthermore, TuBECs do not respond to the feedback inhibition normally induced by TGF-beta1. These data emphasize the functional uniqueness of TuBECs. Understanding the functions and regulatory processes of tumor-associated endothelial cells is critical for developing appropriate antiangiogenic therapies.