SPP1 and plasma cell myeloma: Plasma samples from myeloma patients receiving G-CSF therapy for mobilization of autologous stem cells were available only immediately before leukapheresis (after five days of G-CSF treatment); the plasma osteopontin levels then showed a wide variation and were significantly increased for the myeloma patients (median 89 ng/mL; range 41–356 ng/mL) compared with the pre-apheresis levels of the healthy stem cell donors (Mann-Whitney U test, p = 0.001).