C3 and neoplasm: Considering the high C3 levels found in hypoxic tumor areas and the association between C3-expressing GBM cells and the hypoxia gene signature (Figure 1I), to further investigate the relationship of complement expression to hypoxia, we applied the HALLMARK_COMPLEMENT and HALLMARK_HYPOXIA gene expression signatures to a publicly available data set of spatial transcriptomics from 19 patients with GBM (26).