Gliomas display complex cell surface topographies that resist cytolytic lymphocytes but are reversed by using fascin siRNA

Abstract Gliomas are invasive cancers that resist all forms of attempted therapy, but immunotherapy has improved survival for some patients. We present evidence that another level of complexity may also contribute to lack of responses by the lymphocytes towards gliomas. Atomic force microscopy of four different glioma types: human U251 and rat T9 and F98 glioma cells, including freshly isolated human GBM 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 cytolytic T lymphocytes, [CTL], and chimeric antigen receptor redirected T cells) better than their non-microvilli expressing counterparts. Killer cells released perforin which was detected within the glioma’s microvilli/ filopodia, indicating these structures can receive the cytolytic effector molecules, but cytotoxicity is suboptimal. Transfection of fascin siRNA into U251 cells prevented the microvilli from forming and allowed cytolytic cells to kill these adherent cells just as well as the non-attached glioma cells. These microvilli play multiple roles in glioma biology, such as invasion and resistance to lymphocyte-mediated killing.