Insulin-like growth factor (IGF)-binding protein-3 mutants that do not bind IGF-I or IGF-II stimulate apoptosis in human prostate cancer cells
Insulin-like growth factor (IGF)-binding protein-3 mutants that do not bind IGF-I or IGF-II stimulate apoptosis in human prostate cancer cells
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DOI：
10.1074/jbc.m109604200
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发表时间：
2002-03-22
影响因子：
4.8
通讯作者：
Rechler, MM
中科院分区：
文献类型：
--
作者：
Hong, J;Zhang, G;Rechler, MM
胰岛素样生长因子（IGF）结合蛋白-3（IGFBP-3）可以直接和独立于结合IGF而刺激细胞凋亡和抑制细胞增殖，或者通过与IGF-I和IGF-II形成复合物而间接地刺激细胞凋亡和抑制细胞增殖，所述复合物阻止IGF-I和IGF-II激活IGF-I受体以刺激细胞存活和增殖。迄今为止，IGF独立的行动只在有限数量的细胞中证明，这些细胞不合成或响应IGF。为了评估IGF非依赖性机制的普遍重要性，我们通过用丙氨酸取代所提出的IGF结合位点Ile（56）/Tyr（57）/Arg（75）/Leu（77）/Leu（80）/Leu（81）中的六个残基，并在中国仓鼠卵巢细胞中表达6 m-hIGFBP-3突变体构建体，产生了不能结合IGF-I或IGF-II的人IGFBP-3突变体。IGF-I和IGF-II与6 m-hIGFBP-3的结合降低> 80倍。非结合性6 m-hIGFBP-3突变体仍然能够抑制水貂肺上皮细胞系中的DNA合成，其中野生型hIGFBP-3的抑制先前已被证明是完全不依赖于IGF的。6 m-hIGFBP-3只能通过IGF非依赖性机制发挥作用，因为它不能与抑制其作用的IGF形成复合物。接下来，我们比较了野生型和6 m-hIGFBP-3刺激血清缺乏的PC-3人前列腺癌细胞凋亡的能力。已知PC-3细胞合成并响应IGF-II，因此IGFBP-3可能通过IGF依赖性或IGF非依赖性机制起作用。事实上，6 m-hIGFBP-3刺激PC-3细胞死亡和刺激凋亡诱导的DNA片段化的程度和浓度依赖性与野生型hIGFBP-3相同。这些结果表明，胰岛素样生长因子非依赖性机制的主要贡献者IGFBP-3诱导PC-3细胞凋亡，并可能发挥更广泛的作用，在抗增殖和抗肿瘤作用的IGFBP-3。
Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) can stimulate apoptosis and inhibit cell proliferation directly and independently of binding IGFs or indirectly by forming complexes with IGF-I and IGF-II that prevent them from activating the IGF-I receptor to stimulate cell survival and proliferation. To date, IGF-independent actions only have been demonstrated in a limited number of cells that do not synthesize or respond to IGFs. To assess the general importance of IGF-independent mechanisms, we have generated human IGFBP-3 mutants that cannot bind IGF-I or IGF-II by substituting alanine for six residues in the proposed IGF binding site, Ile(56)/Tyr(57)/Arg(75)/Leu(77)/Leu(80)/Leu(81), and expressing the 6m-hIGFBP-3 mutant construct in Chinese hamster ovary cells. Binding of both IGF-I and IGF-II to 6m-hIGFBP-3 was reduced > 80-fold. The nonbinding 6m-hIGFBP-3 mutant still was able to inhibit DNA synthesis in a mink lung epithelial cell line in which inhibition by wild-type hIGFBP-3 previously had been shown to be exclusively IGF-independent. 6m-hIGFBP-3 only can act by IGF-independent mechanisms since it is unable to form complexes with the IGFs that inhibit their action. We next compared the ability of wild-type and 6m-hIGFBP-3 to stimulate apoptosis in serum-deprived PC-3 human prostate cancer cells. PC-3 cells are known to synthesize and respond to IGF-II, so that IGFBP-3 could potentially act by either IGF-dependent or IGF-independent mechanisms. In fact, 6m-hIGFBP-3 stimulated PC-3 cell death and stimulated apoptosis-induced DNA fragmentation to the same extent and with the same concentration dependence as wild-type hIGFBP-3. These results indicate that IGF-independent mechanisms are major contributors to IGFBP-3-induced apoptosis in PC-3 cells and may play a wider role in the antiproliferative and antitumorigenic actions of IGFBP-3.