Mutant IDH1 regulates the tumor-associated immune system in gliomas. Mus musculus

Gliomas harboring mutations in isocitrate dehydrogenase 1/2 (IDH1/2) have the CpG island methylator phenotype (CIMP) and significantly longer patient survival time than wild-type IDH1/2 tumors. Although there are many factors underlying the differences in survival between these two tumor types, immune-related differences in cell content are potentially important contributors. In order to investigate the role of IDH mutations in immune response, we created a syngeneic pair mouse model for mutated IDH1 (mutIDH1) and wild-type IDH1 (wtIDH1) gliomas and demonstrated that muIDH1 mice showed many molecular and clinical similarities to muIDH1 human gliomas, including a 100-fold higher concentration of 2-hydroxygluratate (2-HG), longer survival time, and higher CpG methylation compared to wtIDH1. Also, we showed that IDH1 mutations caused downregulation of leukocyte chemotaxis, resulting in repression of the tumor-associated immune system. Given that significant infiltration of immune cells such as macrophages, microglia, monocytes, and neutrophils is linked to poor prognosis in many cancer types, these reduced immune infiltrates in muIDH1 glioma tumors may contribute in part to the differences in aggressiveness of the two glioma types. Overall design: Ntva_Ink4a/Arf-/- mice were used to generate mouse gliomas. The genetic backgrounds of tva mice are FVB/N, C57BL6, BALB/C, and 129. To generate wtIDH1- and muIDH1-expressing mouse gliomas, we used the RCAS/tva system as described previously. PDGFa-expressing DF1 cells were mixed with either wtIDH1-shp53- or muIDH1-shp53-expressing DF1 cells. These mixed DF1 cells were injected into Ntva_ Ink4a/Arf-/- mice. Mice were monitored daily until they developed signs of illness, such as lethargy, poor grooming, weight loss, dehydration, macrocephaly, seizure, jumping, and/or paralysis. Whole tumor tissue was used for RNA extraction. Total RNA was extracted from tumor tissues using RNeasy Mini kits (QIAGEN).