EXTRACELLULAR UBIQUITIN REGULATES THE GROWTH OF HUMAN HEMATOPOIETIC-CELLS

We investigated the effects of extracellular ubiquitin on the colony f ormation of human hematopoietic progenitor cells (CFU-GM, CFU-E and BF U-E) and a granulocyte-colony stimulating factor (G-CSF)-dependent hum an myeloblastic leukemic cell line, OCI/AML/1a. Ubiquitin exhibited in hibitory effects on CFU-GM, CFU-E, BFU-E and OCI/AML/1a colony formati on. Extracellular ubiquitin also inhibited the growth of KT3 (T lympho blast), K562 (erythroleukemia) and Daudi (Burkitt's lymphoma) cells, s timulated the growth of HL60 (promyelocytic leukemia) and Jurkat (T-AL L) cells and showed no effect on the growth of U937 cells (monocytic l eukemia). These results indicate that another, previously unrecognized function of extracellular ubiquitin is to regulate hematopoiesis. (C) 1996 Academic Press, Inc.