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The regression of glioblastoma multiforme is time dependent in wild-type rat xenograft model

Introduction: Glioblastoma multiforme (GBM) is an aggressive case of primary brain cancer which remains among the most fatal tumors worldwide. Although, some in vitro and in vivo models have been developed for a better understanding of GBM behavior; a natural model of GBM would improve the efficiency of experimental models to human GBM tumors. We aimed at the present study to examine the survival and durability of U87 cells in the brain of wild-type rats. Methods: U87 cells were intracranially implanted in twenty-one wild-type rats. Tumor size and morphology as well as infiltration of immune cells were investigated at three-time points by H&E and immunohistochemistry (IHC). Results: The results demonstrated that the inoculation of GBM cells led to the infiltration of host defense system cells which caused to immunological regression of the tumor mass after six weeks. While the tumors successfully developed without any sign of host defense invasion in the second week of GBM inoculation. Also, the decrease of tumor size and infiltration of immune system cells were observed at the fourth week. Conclusion: These data remarkably suggest that time plays a crucial role in activating the immune system against human GBM tumors in rats; and it shows that the regression of tumor mass depends on a time slope.