Measurements of water diffusivity and cellularity suggest that higher cellularity contributes to more restricted diffusion.

Purpose: Patients with malignant glioma suffer global compromise of their cellular immunity, characterized by dramatic reductions in CD4 + T cell numbers and function. We have previously shown that increased regulatory T cell (T reg ) fractions in these patients explain T-cell functional deficits. Our murine glioma model recapitulates these findings. Here, we investigate the effects of systemic CTLA-4 blockade in this model. Experimental Design: A monoclonal antibody (9H10) to CTLA-4 was employed against wellestablished glioma. Survival and risks for experimental allergic encephalomyelitis were assessed, as were CD4 + T cell numbers and function in the peripheral blood, spleen, and cervical lymph nodes. The specific capacities for anti-CTLA-4 to modify the functions of regulatory versus CD4 + CD25À responderTcells were evaluated. Results: CTLA-4 blockade confers long-term survival in 80 % of treated mice, without eliciting experimental allergic encephalomyelitis. Changes to the CD4 compartment were reversed, as anti-CTLA-4 reestablishes normal CD4 counts and abrogates increases in CD4 À T cells from treated mice show improved proliferative responses and resistance to T reg -mediated suppression, whereas T regs from the same mice remain anergic and exhibit no restriction of their suppressive capacity. Conclusions: CTLA-4 blockade is a rational means of reversing glioma-induced changes to the CD4 compartment and enhancing antitumor immunity. These benefits were attained through the conferment of resistance toT reg -mediated suppression, and not through direct effects onT regs .

We employed a genetically defined human cancer model to investigate the contributions of two genes upregulated in several cancers to phenotypic changes associated with late stages of tumorigenesis. Specifically, tumor cells expressing two structurally unrelated bonerelated genes, osteonectin and osteoactivin, acquired a highly invasive phenotype when implanted intracranially in immunocompromised mice. Mimicking a subset of gliomas, tumor cells invaded brain along blood vessels and developed altered vasculature at the brain-tumor interface, suggesting that production of those two proteins by tumor cells may create a complex relationship between invading tumor and vasculature co-opted during tumor invasion. Interestingly, the same tumor cells formed massive spontaneous metastases when implanted subcutaneously. This dramatic alteration in tumor phenotype indicates that cellular microenvironment plays an important role in defining the specific effects of those gene products in tumor behavior. In vitro examination of tumor cells expressing either osteonectin or osteoactivin revealed that there was no impact on cellular growth or death but increased invasiveness and expression of MMP-9 and MMP-3. Specific pharmacologic inhibitors of MMP-2/9 and MMP-3 blocked the increased in vitro invasion associated with osteoactivin expression, but only MMP-3 inhibition altered the invasive in vitro phenotype mediated by osteonectin. Results from this genetically defined model system are supported by similar findings obtained from several established tumor cell lines derived originally from human patients. In sum, these results reveal that the expression of a single bonerelated gene can dramatically alter or modify tumor cell behavior and may confer differential growth characteristics in different microenvironments. Genetically defined human cancer models offer useful tools in functional genomics to define the roles of specific genes in late stages of carcinogenesis.

Purpose: Elevated proportions of regulatory T cells (T reg ) are present in patients with a variety of cancers, including malignant glioma, yet recapitulative murine models are wanting. We therefore examinedT regs in mice bearing malignant glioma and evaluated anti-CD25 as an immunotherapeutic adjunct. + T cells, despite themselves being reduced in number. Similar trends are observed in cervical lymph node and spleen, but not in bone marrow. Systemic anti-CD25 administration hinders detection of CD25 + cells but fails to completely eliminate T regs , reducing their number only moderately, yet eliminating their suppressive function. This elimination of T reg function permits enhanced lymphocyte proliferative and IFN-g responses and up to 80% specific lysis of glioma cell targets in vitro. When combined with dendritic cell immunization, anti-CD25 elicits tumor rejection in 100% of challenged mice without precipitating experimental allergic encephalitis. Conclusions: Systemic anti-CD25 administration does not entirely eliminateT regs but does prevent T reg function. This leads to safe enhancement of tumor immunity in a murine glioma model that recapitulates the tumor-induced changes to the CD4 and T reg compartments seen in patients with malignant glioma.