ZEB1 and neoplasm: Under hypoxic conditions, the tumor microenvironment activates major EMT-triggering pathways (e.g., TGFβ signaling, Notch signaling) that facilitate tumor growth and metastasis, and HIF modulates major transcription factors (e.g., TWIST, SNAIL, SLUG, SIP1, ZEB1) that regulate EMT (Jiang et al., 2011).