Disclosed are methods of predicting responsiveness of a cancer cell to a tyrosine kinase inhibitor, and methods of predicting the risk of progression of a cancer cell to a more aggressive form. Also provided are methods of reducing proliferation or promoting differentiation of a cancer cell having reduced level of Numb or increased level of Msi. Further disclosed are methods of treating a mammalian subject having cancer and methods of assessing an agent for chemotherapeutic potential.