Leukemia decreases osteoblastic number and function. (A-B) Osteopontin immunohistochemistry was performed on paraffin-embedded sections. Representative images are shown of (A) a naive femur and (B) a leukemic femur. Left panels 20×, and right panels 60× objectives. Osteopontin⁺ cells are stained brown, and sections were counterstained with hematoxylin (blue). Arrowheads indicate osteopontin⁺ cells. (C) Quantification of serum osteocalcin measured by ELISA. (D) Real-time RT-PCR quantifying osteocalcin RNA expression in osteoblast-like cells collected from the long bones of normal or leukemic mice at day 6 or 11 and magnetically separated based on CD45 expression. Statistical significance was determined compared with naive mice (day 0). n = 5 samples per experimental group. (E-F) CFU-OBs formed per well from (E) whole marrow after 28 days in culture and (F) cells collected by collagenase digestion of bone fragments after 15 days in culture. **P ≤ .01. ***P ≤ .001.