Autocrine Regulation of Human Tumor Cell Proliferation by Insulin-Like Growth Factor II: anin-VitroModel*

Abstract

We have shown that a pleomorphic cell line of abnormal human karyotype derived from a stomach carcinoma (LIM-1839) proliferates in serum-free medium, expresses insulin-like growth factor II (IGF-II) mRNA, and secretes IGF-II (up to 56 ng/ml in serum-free conditioned medium, as measured in a rat liver RRA. No detectable levels of IGF-I can be measured in serum-free conditioned medium by RIA. These cells also secrete IGF-binding proteins, detected by a charcoal adsorption assay. The release of IGF-II and IGF binding proteins into serum-free conditioned medium (1.7 pmol/10(6) cells.24 h and 0.8 pmol binding sites/10(6) cells.24 h for 3 days, respectively) is inhibited 80% by cycloheximide (10 micrograms/ml). The LIM-1839 cells have type I and type II IGF receptors, determined by affinity cross-linking and competition binding studies. These cells proliferated 1.6-fold over 4 days in serum-free medium, with fresh medium changes on days 0 and 2: their growth was inhibited 56% by 40 micrograms/ml Sm 1.2, a monoclonal antibody which recognizes IGF-I and IGF-II. The addition of 20 and 50 ng/ml multiplication stimulating activity (rat IGF-II) caused 1.8- and 1.7-fold increases in cell growth between days 0 and 4 compared to controls, while [Thr59]IGF-I, at 20 and 50 ng/ml, caused 1.6- and 2.0-fold increases. Insulin, at 2 and 10 micrograms/ml, had no significant effect. The stimulatory effects of endogenous and exogenous IGFs on LIM-1839 cell proliferation were inhibited by a monoclonal antibody to the type I IGF receptor, alpha IR-3. These results suggest that the LIM-1839 cells are biologically responsive to endogenously produced IGF-II, and may thereby provide an in vitro model for autocrine regulation of human tumor growth by IGF-II.

Blockade of the insulin‐like growth‐factor‐I receptor inhibits growth of human colorectal cancer cells: Evidence of a functional IGF‐II‐mediated autocrine loop

“…We chose the second approach, using the aIR3 MAb, which recognizes the human IGF-I-R (Kull et al, 1983) and potently neutralizes IGF-I-and IGF-11-mediated signal transduction (Chen et al, 1991;Macaulay et al, 1990;Ohmura et aL, 1990;Thompson et al, 1990). Indeed, blocking the IGF-I-R inhibited growth in 7 out of 12 colorectal carcinoma cell lines tested: aIR3 significantly reduced proliferation (up to 42%), inhibited cell division, as reflected by the decrease in cell numbers (up to 72%), and prolonged generation doubling times (up to 2-fold).…”

Enhanced growth capacity of neonatal pulmonary artery smooth muscle cells in vitro: Dependence on cell size, time from birth, insulin‐like growth factor I, and auto‐activation of protein Kinase C

“…A likely mediator would be PDGF-AA, which contributes to autocrine growth of other vascular cells (Majack et al, 1990). IGF-I and -11 could also be involved as they are locally present in vascular PA tissue (Perkett et al, 1992), expressed by SMC (Delafontaine et al, 1991), developmentally regulated (Daughaday and Rotwein, 1989) and implicated in autocrine or paracrine growth of transformed cells (Thompson et al, 1990) and fetal fibroblasts (Stiles and D'Ercole, 1990).…”

The Efficacy of IGF-I Receptor Monoclonal Antibody against Human Gastrointestinal Carcinomas is Independent of k-ras Mutation Status

“…IGFs stimulate the proliferation of GI cancer cells and blocking of IGF-IR signaling inhibits tumor growth (9,(12)(13)(14)(15)(16)(17)(18)(19)(20). High serum concentration of IGF-I increases the risk of developing several cancers (10).…”