ID1 and central nervous system cancer: Therefore, whereas both Id1 and Id2 genes expression appear to be upregulated in microglial cells exposed to glioma cells, and ID1 and ID2 proteins can form protein-protein complexes with ETS2 in microglia, only a transcriptional axis formed by ID2 and ETS2 seems to be of relevance for the acquisition of the microglial tumour-supportive phenotype.