Crosstalk between Medulloblastoma Cells and Endothelium Triggers a Strong Chemotactic Signal Recruiting T Lymphocytes to the Tumor Microenvironment

Cancer cells can live and grow if they succeed in creating a favorable niche that often includes elements from the immune system. While T lymphocytes play an important role in the host response to tumor growth, the mechanism of their trafficking to the tumor remains poorly understood. We show here that T lymphocytes consistently infiltrate the primary brain cancer, medulloblastoma. We demonstrate, both in vitro and in vivo, that these T lymphocytes are attracted to tumor deposits only after the tumor cells have interacted with tumor vascular endothelium. Macrophage Migration Inhibitory Factor (MIF)” is the key chemokine molecule secreted by tumor cells which induces the tumor vascular endothelial cells to secrete the potent T lymphocyte attractant “Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES).” This in turn creates a chemotactic gradient for RANTES-receptor bearing T lymphocytes. Manipulation of this pathway could have important therapeutic implications

Glioma cells display complex cell surface topographies that resist the actions of cytolytic effector lymphocytes.

Gliomas are invasive cancers that resist all forms of attempted therapy. Immunotherapy using Ag-pulsed dendritic cells has improved survival in some patients. We present evidence that another level of complexity may also contribute to lack of responses by the lymphocytes toward gliomas. Atomic force microscopy of four different glioma types-human U251 and rat T9 and F98 glioma cells, including freshly isolated human glioblastoma multiforme neurosphere cultures (containing "stem cell-like cells")-revealed a complex surface topography with numerous microvilli and filopodia. These structures were not found on other cell types. Electron microscopy and immunofluorescence microscopy of glioma cells confirmed that microvilli are present. U251 cells with microvilli resisted the cytolytic actions of different human effector cells, (lymphokine-activated killer cells, γδ T cells, conventional CTLs, and chimeric Ag-receptor-redirected T cells) better than their nonmicrovilli-expressing counterparts. Killer lymphocytes released perforin, which was detected within the glioma's microvilli/filopodia, indicating these structures can receive the cytolytic effector molecules, but cytotoxicity is suboptimal. Air-dried gliomas revealed nodes within the microvilli/filopodia. The microvilli that penetrated 0.4-μm transwell chamber's pores resisted the actions of CTLs and physical damage. Those nodelike structures may represent a compartmentalization that resists physical damage. These microvilli may play multiple roles in glioma biology, such as invasion and resistance to lymphocyte-mediated killing

Immunotherapy for Osteosarcoma: Genetic Modification of T cells Overcomes Low Levels of Tumor Antigen Expression

Human epidermal growth factor receptor 2 (HER2) is expressed by the majority of human osteosarcomas and is a risk factor for poor outcome. Unlike breast cancer, osteosarcoma cells express HER2 at too low, a level for patients to benefit from HER2 monoclonal antibodies. We reasoned that this limitation might be overcome by genetically modifying T cells with HER2-specific chimeric antigen receptors (CARs), because even a low frequency of receptor engagement could be sufficient to induce effector cell killing of the tumor. HER2-specific T cells were generated by retroviral transduction with a HER2-specific CAR containing a CD28.ζ signaling domain. HER2-specific T cells recognized HER2-positive osteosarcoma cells as judged by their ability to proliferate, produce immunostimulatory T helper 1 cytokines, and kill HER2-positive osteosarcoma cell lines in vitro. The adoptive transfer of HER2-specific T cells caused regression of established osteosarcoma xenografts in locoregional as well as metastatic mouse models. In contrast, delivery of nontransduced (NT) T cells did not change the tumor growth pattern. Genetic modification of T cells with CARs specific for target antigens, expressed at too low a level to be effectively recognized by monoclonal antibodies, may allow immunotherapy to be more broadly applicable for human cancer therapy