TPO and neoplasm: It has been reported that granulocyte colony-stimulating factor (G-CSF) treatment enhanced bone tumor growth in mice.(29) Both G-CSF and TPO may increase bone marrow cellularity, but since TPO treatment reduced tumor growth and G-CSF increased tumor growth in bone, this suggests that the decrease in skeletal tumor burden in TPO-treated mice was less likely due to the general changes in bone marrow cellularity.