HIF1α, the principal mediator of hypoxic effects on tumor cells, regulates CSC stemness, modulating various signaling pathways, including the Notch, Hedgehog, Hippo, wingless (Wnt)/β-catenin, Janus-activated kinase/signal transducer, activator of transcription (JAK/STAT), phosphatidylinositol 3-kinase/phosphatase, tensin homolog (PI3K/PTEN) and nuclear factor-kB (NF-kB) pathways [119]. Here, HIF1A is linked to neoplasm.