PHOSPHO1 and osteosarcoma: Roberts and colleagues11 purified recombinant human PHOSPHO1 by amplification of a curtailed cDNA transcript from the SaOS‐2 osteosarcoma cell line, and continuous spectrophotometric phosphate assays with several potential phosphomonoester substrates revealed PHOSPHO1's specific activity toward the metabolites phosphoethanolamine (PEA) and phosphocholine (PCho), with highest activity between pH 6.0 to 7.2.