PARATHYROID HORMONE-RELATED PROTEIN IN AN ESOPHAGEAL SQUAMOUS-CELL CARCINOMA WITH TUMOR-INDUCED HYPERCALCEMIA

Cancers from patients with tumor-induced hypercalcemia usually produce a circulating factor that mimics the parathyroid hormone activity, te rmed parathyroid hormone-related protein. Incidence of tumor-induced h ypercalcemia appears to be high in patients with squamous cell carcino ma of the esophagus, and the presence of parathyroid hormone-related p rotein have been shown in some primary esophageal cancers. In the pres ent study, we have investigated the presence of parathyroid hormone-re lated protein in a patient with metastased squamous cell carcinoma of the esophagus complicated with tumor-induced hypercalcemia. Protein wa s searched by immunohistochemistry, and messenger RNA was investigated by reverse transcriptase-polymerase chain reaction and S1 nuclease as say. Both messenger RNA and protein were detected in hepatic metastase s, whereas normal esophageal mucosa and primary cancer did not express detectable protein or messenger RNA using the S1 nuclease assay. Reve rse transcriptase-polymerase chain reaction was positive in all these tissues, including normal esophageal mucosa. In conclusion, the presen t case suggests that tumor-induced hypercalcemia due to esophageal squ amous cell carcinoma may be caused by parathyroid hormone-related prot ein mostly released by liver metastases.