Monitoring of murine osteosarcoma by serial alkaline phosphatase determinations.

To establish that alkaline phosphatase (AP) was released by osteosarcoma cells, we measured this enzyme in C3H/HeJ mice with im-implanted osteosarcoma and in in vitro cultures of neoplastic cells subjected to short-term incubation. We found that 10(5) osteosarcoma cells synthesized a significant amount of AP in vitro in 30 minutes at 37 degrees C. A good correlation existed between pulmonary metastatic tumors and the AP values. Serum AP measurements indicated approximate sizes of disseminated and localized tumors, but could not monitor early localized tumors.