PTHRP-MEDIATED HYPERCALCEMIA IN A CASE OF CML BLAST CRISIS

We report a 52-year-old man with chronic myelogenous leukaemia (CML) w ho developed hypercalcaemia in blast crisis, There was a high serum le vel of parathyroid hormone-related protein (PTHrP). The leukaemia cell s secreted PTHrP into culture medium when cultured in vitro and were s hown to express PTHrP mRNA by reverse transcription-polymerase chain r eaction. Transplantation of the leukaemia cells into nude mice resulte d in the production of Ph(1) chromosome-positive tumours which caused increased levels of calcium and PTHrP in the blood. These results indi cated that the hypercalcaemic event in the patient was induced by PTHr P of CML cell origin.