Inadequate serum TPO levels increase during induction chemotherapy in c-mpl functional AML blast cells. Serial serum TPO levels expressed after logarithmic transformation according to platelet counts in 4 AML patients treated with induction chemotherapy (left). Solid line represents the regression line computed in ALL patients after the first 2 weeks of induction chemotherapy (n = 38). Dashed lines depict the 95% confidence limits of this regression. Flow cytometry analyses of c-mpl expression at diagnosis in blast cells of the 4 AML patients (right). Filled histograms represent negative controls.