PLASMA INTER-ALPHA-TRYPSIN INHIBITOR-RELATED URINARY GLYCOPROTEIN EDC1 INHIBITS THE GROWTH OF A BURKITTS-LYMPHOMA CELL-LINE

A homogeneous preparation of a urinary glycoprotein has been isolated from urine of patients with malignant melanoma and advanced adenocarcinomas of colon and lung. This molecule, Mr 30 kDa, is homologous to EDC1, a proteinase inhibitor antigenically related to plasma inter‐α‐trypsin inhibitor (IATI) originally isolated from the urine of a leukemic patient, E.D. The newly isolated EDC1 inhibits cellular proliferation of a Burkitt's lymphoma cell line, Raji, growing in serum‐free medium supplemented with insulin, transferrin, selenium, and linoleic acid. This concentration‐dependent inhibitory effect was monitored in terms of change in cell number and 3H‐thymidine incorporation. The growth of cells treated with ∼3.3 pmol EDCl/ml was 50% that of the control group by both assays. EDC1 was not cytotoxic to the cells because the EDC1‐treated cells excluded trypan blue and resumed normal growth after removal of EDC1. In addition, EDC1 treatment of Raji cells prelabeled with 3H‐labeled DNA did not release more radioactivity into the conditioned medium than the untreated labeled cells. EDC1 did not affect the growth of Hs2B2, a B‐lymphoblast cell line, and Hs294T, a human malignant melanoma cell line. Equimolar and larger quantities of other proteinase inhibitors with inhibitory profiles similar to that of EDC1 (α‐1 proteinase inhibitor, soybean trypsin inhibitor, lima bean trypsin inhibitor, and turkey ovomucoid) did not affect the growth of Raji cells. Raji cells have an absolute requirement of transferrin as a nutrient and require insulin to modulate the expression of transferrin receptors. The cells also synthesize interleukin‐I as an autocrine growth stimulator. EDC1 did not form a detectable complex with transferrin, insulin, or any autocrine factor synthesized by the cells. Copyright © 1990 Wiley‐Liss, Inc.