Establishment of a parathyroid hormone-like factor-producing esophageal carcinoma cell line (EC-GI).

A new cell line, designated EC-GI, was established from a 65-year-old patient with esophageal carcinoma who developed humoral hypercalcemia. The original tumor as well as the cell line caused marked hypercalcemia in tumor-bearing nude mice, in which a marked increase in osteoclastic bone resorption was demonstrated. The conditioned medium of EC-GI cells contained potent bone resorbing activity which stimulated cyclic AMP production in parathyroid hormone (PTH)-responsive osteoblast-like cells (ROS 17/2.8). EC-GI cells will be useful for characterization and purification of the PTH-like factor responsible for humoral hypercalcemia of malignancy.