Mesenchymal Stromal Stem Cell-Derived Microvesicles Enhance Tumor Lysate Pulsed Dendritic Cell Stimulated Autologous T lymphocyte Cytotoxicity

Abstract

Background: Immunotherapy is one promising therapeutic strategy against glioma, an aggressive form of brain<br />cancer. Previous studies have demonstrated that multiple tumor antigens exist and can be used to induce tumor specific<br />T cell responses. Furthermore, recently it was shown that TLR4-primed mesenchymal stem cells (MSCs), also known<br />as MSC1, mostly elaborate pro-inflammatory mediators. Compared to MSCs, MSC-derived microvesicles (MVs) have<br />advantageous properties that present them as stable, long lasting effectors with no risk of immune rejection. Therefore,<br />peripheral blood monocyte derived dendritic cells (MoDCs) have been used to load tumor antigens and stimulate T<br />cell mediated responses in the presence of MSC1-derived MVs in vitro. Methods: The B92 tumor cell line was heated<br />to 43°C for 90 min prior to preparation of tumor cell lysates. MVs were purified by differential ultracentrifugation<br />after isolation, stimulation of proliferation and treatment of MSCs. Autologous T cells isolated from non-adherent<br />cells were harvested during the procedure to generate MoDCs and then incubated with heat stressed tumor cell lysate<br />pulsed DCs in the presence of MSC1-derived MVs. T cells were then co-cultured with tumor cells in 96-well plates at<br />a final volume of 200 μl CM at an effector: target ratio of 100:1 to determine their specific cytotoxic activity. Results:<br />Flow cytometric analysis, T cell mediated cytotoxicity showed that heat stressed tumor antigen pulsed MoDCs and<br />MSC1-derived MVs primed T cells elicited non-significantly enhanced cytotoxic activity toward B92 tumor cells<br />(P≥0.05). Conclusion: These findings may offer new insights into tumor antigen presenting technology involving<br />dendritic cells and MSC1-derived MVs. Further exploration of the potential of such nanoscale particles in immunotherapy<br />and in novel cancer vaccine settings appears warranted.