Topotecan enhances immune clearance of gliomas.

Despite aggressive surgery, radiation therapy, and chemotherapy, glioblastoma multiforme (GBM) is refractory to therapy, recurs quickly, and results in a median survival time of only 14 months. The modulation of the apoptotic receptor Fas with cytotoxic agents could potentiate the response to therapy. However, Fas ligand (FasL) is not expressed in the brain and therefore this Fas-inducing cell death mechanism cannot be utilized. Vaccination of patients with gliomas has shown promising responses. In animal studies, brain tumors of vaccinated mice were infiltrated with activated T cells. Since activated immune cells express FasL, we hypothesized that combination of immunotherapy with chemotherapy can activate Fas signaling, which could be responsible for a synergistic or additive effect of the combination. When we treated the human glioma cell line U-87 and GBM tumor cells isolated from patients with TPT, Fas was up regulated. Subsequent administration of soluble Fas ligand (sFasL) to treated cells significantly increased their cell death indicating that these Fas receptors were functional. Similar effect was observed when CD3(+) T cells were used as a source of the FasL, indicating that the up regulated Fas expression on glioma cells increases their susceptibility to cytotoxic T cell killing. This additive effect was not observed when glioma cells were pre-treated with temozolomide, which was unable to increase Fas expression in tumor. Inhibition of FasL activity with the antagonistic antibody Nok-1 mitigated these effects confirming that these responses were specifically mediated by the Fas-FasL interaction. Furthermore, the CD3(+) T cells co-cultured with topotecan treated U-87 and autologous GBM tumor cells showed a significant increase in expression in IFN-gamma, a key cytokine produced by activated T cells, and accordingly enhanced tumor cytotoxicity. Based on our data we conclude that drugs, such as topotecan, which cause up regulation of Fas on glioma cells can be potentially exploited with immunotherapy to enhance immune clearance of tumors via Fas signaling.

Preferential migration of regulatory T cells mediated by glioma-secreted chemokines can be blocked with chemotherapy.

Despite the immunogenicity of glioblastoma multiforme (GBM), immune-mediated eradication of these tumors remains deficient. Regulatory T cells (Tregs) in the blood and within the tumor microenvironment of GBM patients are known to contribute to their dismal immune responses. Here, we determined which chemokine secreted by gliomas can preferentially induce Treg recruitment and migration. In the malignant human glioma cell lines D-54, U-87, U-251, and LN-229, the chemokines CCL22 and CCL2 were detected by intracellular cytokine analysis. Furthermore, tumor cells from eight patients with GBM had a similar chemokine expression profile. However, only CCL2 was detected by enzyme-linked immunosorbent assay, indicating that CCL2 may be the principal chemokine for Treg migration in GBM patients. Interestingly, the Tregs from GBM patients had significantly higher expression levels of the CCL2 receptor CCR4 than did Tregs from healthy controls. Glioma supernatants and the recombinant human chemokines CCL2 and CCL22 induced Treg migration and were blocked by antibodies to the chemokine receptors. Production of CCL2 by glioma cells could also be mitigated by the chemotherapeutic agents temozolomide and carmustine [3-bis (2-chloroethyl)-1-nitrosourea]. Our results indicate that gliomas augment immunosuppression by selective chemokine-mediated recruitment of Tregs into the tumor microenvironment and that modulating this interaction with chemotherapy could facilitate the development of novel immunotherapeutics to malignant gliomas.

Transient hyperglycemia in Hispanic children with acute lymphoblastic leukemia.

BACKGROUND: Transient hyperglycemia occurs commonly during the treatment for childhood acute lymphoblastic leukemia (ALL). The purpose of this study was to examine the incidence of and risk factors for transient hyperglycemia during induction chemotherapy in Hispanic pediatric patients diagnosed with B-Precursor ALL. PROCEDURE: The study cohort consisted of 155 Hispanic pediatric patients diagnosed with ALL and treated at one of two South Texas pediatric oncology centers between 1993 and 2002. Hyperglycemia was defined as > or = 2 glucose determinations of > or = 200 mg/dl during the first 28 days of induction chemotherapy. RESULTS: Overall, 11.0% of the study cohort developed transient hyperglycemia during induction chemotherapy. Age and body mass index (BMI) were both positively associated with the risk of hyperglycemia. Females exhibited a substantially higher risk of hyperglycemia than males, but this association did not reach statistical significance after adjusting for other covariates. Among patients who developed hyperglycemia, 100% of those who required insulin were in the 13-18-year age group and reported a family history of diabetes. Hyperglycemic patients classified as obese (BMI > or = 95 centile) were more than twice as likely to have required insulin therapy compared to overweight patients (BMI 85-<95 centile) and three times as likely to have required insulin compared to normal weight (BMI < 85 centile) patients. CONCLUSIONS: The incidence of chemotherapy-induced transient hyperglycemia in the present study cohort is comparable to that reported in previous pediatric ALL patients. This finding is interesting in view of the elevated prevalence of obesity and the underlying dietary behaviors in this Hispanic study cohort.