APOE and glioblastoma: Early GBM microglia (4) demonstrated gain in expression of complement genes (C1qb, C1qa, C1qc) and lipoprotein catabolic process (Apoe, Ctsd) (Fig. 6a) and loss of gene expression involved in mitochondrial electron transport, ATP-synthesis-coupled electron transport and aerobic respiration (mt-Nd1/2/4/5/6, mt-Co1/2) during early to late GBM progression (Fig. 6a), suggestive of changes in energy use in microglia (4) during GBM progression.