INSULIN-LIKE GROWTH-FACTOR-I IS A GROWTH AND SURVIVAL FACTOR IN HUMANMULTIPLE-MYELOMA CELL-LINES

Human multiple myeloma (MM) represents a highly aneuploid tumor as sho wn by cytogenetic studies. This may partly explain the heterogeneity w ith regard to growth factor requirements demonstrated among MM cells. We have previously reported the expression of insulin-like growth fact or I (IGF-I) and IGF-I receptor (IGF-IR) mRNA in some MM cell lines, I n this study we investigated the role of IGF-I as a growth and/or surv ival factor in three MM cell lines: LP-1, EJM, and Karpas 707. We repo rt that all cell lines expressed IGF-I and IGF-IR mRNA and protein, LP -1 and Karpas 707, but not EJM, were stimulated to proliferation in a dose-dependent manner by exogenous IGF-I. An IGF-IR blocking antibody inhibited both the IGF-I-induced and spontaneous growth of LP-1 and Ka rpas 707, while the EJM cell line was unaffected by the addition of th e antibody. In conclusion, our results show that IGF-I can act as a gr owth factor in human MM, and they suggest that an autocrine IGF-I loop may contribute to the growth and survival in some MM cell lines. (C) 1996 by The American Society of Hematology.