TGFB1 and chronic myelogenous leukemia, BCR-ABL1 positive: Meanwhile, the exosomes derived from chronic myeloid leukemia cells contained a cytokine, TGFβ1, which binds to the TGFβ1 receptor on the leukemia cells, thereby promoting tumor growth through activation of extracellular signal-regulated kinase, protein kinase, and anti-apoptotic pathways in the producer cells16.