Moreover, immunohistochemistry (IHC) staining of tumor sections for the regulatory T cell (Treg) marker forkhead box P3 (FoxP3) showed that CAF-HIF-2α KO tumors had significantly fewer Tregs than CAF-HIF-2α WT tumors, suggesting that the survival improvement in tumor-bearing mice may have been driven by indirect deficiency of pro-tumor macrophages and T regulatory cells. This evidence concerns the gene EPAS1 and neoplasm.