ID1 and cancer: ID1 has been proven to control the proliferation and differentiation of stem cells.[14] It is also linked to tumorigenesis and is highly expressed in numerous types of cancers.[26] It exerts its tumor‐promoting effects through different signaling pathways including the K‐Ras, BMP, PI3K/Akt, STAT3, MAPK, and TGF‐β pathways.