Figueroa J A, Sharma J, Jackson J G, McDermott M J, Hilsenbeck S G, Yee D
Department of Medicine, University of Texas Health Science Center, San Antonio 78284-7884.
J Cell Physiol. 1993 Nov;157(2):229-36. doi: 10.1002/jcp.1041570204.
The insulin-like growth factors (IGFs) are potent mitogens for breast cancer cells and their activity is modulated by high affinity binding proteins (IGFBPs). We have recently shown that IGFBP-1 purified from human amniotic fluid neutralizes IGF-I-dependent growth of MCF-7 cells. In this study we examined the effects of recombinant IGFBP-1 (rBP-1) on IGF-I, estradiol (E2), and serum-induced monolayer and anchorage independent growth (AIG) of MCF-7 cells. Under serum-free conditions, rBP-1 had no effect on MCF-7 basal monolayer growth. However, 40 nM rBP-1 completely blocked the mitogenic action of both IGF-I and 5% charcoal stripped serum (CSS). This concentration of rBP-1 partially inhibited E2-induced growth, while 80 nM rBP-1 completely abolished E2 mitogenicity. The addition of either excess IGF-I or 5 nM [Arg3]IGF-I, a species that does not bind IGFBPs, neutralized rBP-1 inhibitory effects. In AIG assays, 80 nM rBP-1 reduced colony number by at least 70% and decreased colony size in all treatment groups compared to control. We examined rBP-1 effects on both IGF-I binding to MCF-7 membranes and activation of type I IGF receptor (IGFR1) and found that 80 nM rBP-1 reduced IGF-I receptor binding to levels of nonspecific binding and completely abolished ligand-dependent IGFR1 phosphorylation. However, neither treatment with 5% CSS nor exposure to E2 resulted in IGFR1 phosphorylation suggesting that different mechanism(s) are responsible for rBP-1 inhibitory action under this condition. Our data suggest rBP-1 may serve as an antagonist of human breast cancer growth by interfering with growth factor-mediated cell proliferation.
胰岛素样生长因子（IGFs）是乳腺癌细胞的强效促有丝分裂原，其活性受高亲和力结合蛋白（IGFBPs）调节。我们最近发现，从人羊水中纯化的IGFBP-1可中和IGF-I依赖的MCF-7细胞生长。在本研究中，我们检测了重组IGFBP-1（rBP-1）对IGF-I、雌二醇（E2）以及血清诱导的MCF-7细胞单层生长和锚定非依赖性生长（AIG）的影响。在无血清条件下，rBP-1对MCF-7细胞的基础单层生长无影响。然而，40 nM的rBP-1完全阻断了IGF-I和5%活性炭处理血清（CSS）的促有丝分裂作用。该浓度的rBP-1部分抑制E2诱导的生长，而80 nM的rBP-1则完全消除了E2的促有丝分裂活性。添加过量的IGF-I或5 nM的[Arg3]IGF-I（一种不与IGFBPs结合的物质）可中和rBP-1的抑制作用。在AIG试验中，与对照组相比，80 nM的rBP-1使所有处理组的集落数减少至少70%，并减小了集落大小。我们检测了rBP-1对IGF-I与MCF-7细胞膜结合以及I型IGF受体（IGFR1）激活的影响，发现80 nM的rBP-1将IGF-I受体结合降低至非特异性结合水平，并完全消除了配体依赖性IGFR1磷酸化。然而，用5% CSS处理或暴露于E2均未导致IGFR1磷酸化，这表明在此条件下rBP-1的抑制作用由不同机制介导。我们的数据表明，rBP-1可能通过干扰生长因子介导的细胞增殖而作为人乳腺癌生长的拮抗剂。
