Glioma stem cells reconstruct similar immunoinflammatory microenvironment in different transplant sites and induce malignant transformation of tumor microenvironment cells.

PURPOSE: This study aimed to examine whether the different tumor-transplanted sites could construct a similar immunoinflammatory microenvironment and to investigate the interactions between tumor microenvironment cells.

METHODS: The red fluorescent protein-SU3 (SU3-RFP) or SU3 glioma stem cells (GSC) were inoculated into the brain, liver, abdominal cavity, and subcutis of green fluorescent protein (GFP)-nude mice. The tumor tissues were taken to observe the tissue cell distribution. The single cell suspension of tumor tissues was prepared and cultured, while the SU3-RFP cells were co-cultured with the cells from GFP-transgenic mice. The RFP+ , GFP+ , and RFP+ /GFP+ cells were traced by fluorescence microscope, and their protein expressions were determined by Western blot analysis. The markers of immunoinflammatory cells, including F4/80, CD11b, CD11c, CD80, CD47, and SIRP-α, were determined by RT-PCR and immunocytochemistry assays, respectively.

RESULTS: The xenograft models of all transplant sites were inducible, and the red tumor cells of tumor tissues were encircled by a great quantity of host-derived green cells, including immunoinflammatory cells with CD80, F4/80, CD11b, and CD11c expressions, which might generate the cell colonies and possess the pseudopodia. Additionally, the interactions between red tumor cells and green immunoinflammatory cells, including cell fusion process and yellow fusion cell formation, were observed in cultured cells. The fusion cells-derived B4 cells with expressions of CD47 and SIRP-α proteins had the strong proliferation ability and tumorigenic effect.

CONCLUSIONS: The similar tumor immunoinflammatory microenvironment was constructed by GSC in different transplant sites, and the cell fusion indicated a malignant transformation of the tumor microenvironment cells.