Human ribonuclease inhibitor (RI) is an acidic cytoplasmic glycoprotein with molecular mass of 50 ku. RI can inhibit the activity of ribonuclease A ( RNase A). Angiogenin (Ang) is a member of RNase A superfamily. RI also can inhibit Ang activities by tight combination. Angiogenesis is an essential condition for the development of tumors and their metastatic dissemination. So anti-angiogenesis will be an efficient method in the inhibition of the growth and metastasis of tumor. The experiment demonstrated that RI might effectively block the angiogenesis that was induced by angiogenin. RI is constructed almost entirely of leucine-rich repeats that might involve in other unclear biological effect. In order to understand further the potential function of RI and investigate the role of RI in invasion and metastasis. The study established a transfection of human RI cDNA into B16 melanoma cells by the retroviral packaging cell line PA317 carrying the pLNCX-RI in vitro. Transfected B16 cells by PA317 carrying the pLNCX and untransfected B16 cells were used as control. The B16pLNCX-RI cell line with a stably high expression of RI was identified by PCR, RT-PCR, Western blot and immunofluorescence assay respectively. The results showed that the transfected RI gene might significantly inhibit cell proliferation, migration, and enhance cell adhesion, as well as, make morphological changes in vitro. Cell doubling time were (24.98 ±0.16) h, (25.62 ±0.28) h, (32.64 + 1.11) h in B16 cells, B16 pLNCX and B16 pLNCX-RI cells respectively. Cell adhesion rate was significantly increased by 19. 5% and 17. 8% as well as cell migration was reduced by 60% and 61.4% in B16 pLNCX-RI cells compared with pLNCX B16 cells and B16 cells respectively. B16 pLNCX-RI cells became flatter, less nucleoli, less division phases and weaker alkalophilic quality of cytoplasm compared with control groups, which should imply that cell proliferation viability was decreased and malignant phenotype was improved on the cell transfected RI. Mice injected with B16 pLNCX-RI cells show a significant inhibition of the metastasis of tumor with lighter lung weight, fewer metastasis nodules, a lower incidence rate, a lower density of blood vessels and longer survival with respect to the control groups, which implied that RI might be involved in metastasis of melanoma. The results of experiments show RI has a significant antitumor metastasis effect and suggest that it is partially responsible for inhibiting angiogenesis, decreasing cell proliferation, reducing cell migration and enhancing cell adhesion.%人核糖核酸酶抑制因子(human ribonuclease inhibitor,RI)是一种细胞质中分子质量为50 ku的酸性糖蛋白.RI能抑制核糖核酸酶A(RNase A)的活性,RNase A与血管生成因子(angiogenin,Ang)的氨基酸有着高度保守的同源序列.Ang是RNase A超家族的一员,RI通过与RNase A和Ang的紧密结合而抑制其活性.血管生成及新血管的形成,是肿瘤发生和转移的必要条件.所以抗血管生成将是一种很有希望的对抑制肿瘤生长和转移的有效方法.实验显示RI能有效地抑制肿瘤诱导血管的生成.RI由含有许多亮氨酸重复序列的多肽组成.含有这样重复序列的100多种蛋白质显示了广泛的功能,包括细胞周期调节,DNA修复,对细胞外基质相互作用以及抑制酶活性等.RI被认为是胚胎发育,创伤愈合及肿瘤发生中新血管形成的一种调节因子.RI定位于染色体的11p15.5,与ras基因邻近,在肿瘤病人中经常存在染色体11p15.5部位的变异和异常.RI可能与细胞的生长和分化有关,因此,RI可能还具有尚未知的生物学作用.为了进一步了解RI的潜在功能以及探讨RI与肿瘤侵润、转移的关系,将人的核糖核酸酶抑制因子基因的cDNA通过逆转录包装细胞PA317,并转染到B16小鼠黑色瘤细胞中,用转染空载体和未转染的B16细胞作为对照.通过PCR,RT-PCR,蛋白质免疫印迹,免疫荧光分析鉴定,获得稳定表达人核糖核酸酶抑制因子的细胞株.结果显示,转染的RI基因在体外能显著地抑制细胞增殖和细胞迁移,增加了细胞的粘附以及改善细胞的恶性形态,B16,B16 pLNCX,B16 pLNCX-RI 3种细胞的倍增时间分别为(24.98±0.16)h,(25.62±0.28)h,(32.64±1.11)h.与对照组相比,转RI的细胞粘附率增加17.8%和19.5%而迁移降低了61.4%和60%.转RI的细胞比对照组细胞较平展,核仁和分裂相较少,胞质嗜碱性减弱,提示细胞增殖活性降低和恶性表型的改善.将3种B16细胞静脉注射到C57BL/6小鼠中,结果表明,转染RI基因的实验组显著地抑制了肿瘤的转移,与两个对照组相比,荷瘤小鼠有更长的存活时间,少得多的转移节结,更低的肿瘤血管密度和肺重量.结果显示,RI的表达可能与黑色瘤的转移有关,提示RI能显著地抑制肿瘤的转移,可能由于其与抑制血管作用,增加细胞粘附,降低细胞迁移及增殖有关.
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