This increase could be related to tumour-derived factors that may either promote the mobilisation of CD34+ cells from the bone marrow, such as GM-CSF (Garrity et al, 1997), or inhibit DC maturation from CD34+ precursors, such as VEGF, M-CSF and IL-6 (Almand et al, 2000). The gene discussed is CSF2; the disease is neoplasm.