Musat Madalina, Korbonits Márta, Pyle Megan, Gueorguiev Maria, Kola Blerina, Morris Damian G, Powell Michael, Dumitrache Constantin, Poiana Catalina, Grossman Ashley B
Department of Endocrinology, St. Bartholomew's Hospital, London EC1A 7BE, UK.
Pituitary. 2002;5(4):235-42. doi: 10.1023/a:1025325832698.
The CDK inhibitor p27 plays a pivotal role in controlling cell proliferation during development, and has been implicated in tumorigenesis. Previous studies have demonstrated changes in p27 protein expression, but not in mRNA levels, in human pituitary tumors. It seems probable that the fall in p27 is due to increased degradation through the ubiquitin-proteasome pathway. Skp2 (S-phase kinase-interacting protein) is a specific F-box protein that allows the recognition and binding of phosphorylated p27 to the ubiquitin complex. The aim of our study was thus to investigate the possible role of Skp2 in pituitary tumorigenesis. A total of 59 human pituitary samples, 7 normal and 52 adenomas, were assessed for transcriptional expression of Skp2; 51 pituitary samples were assessed for protein expression. Real-time RT-PCR was performed on cDNA of reverse-transcribed mRNA for relative quantification of the Skp2 transcript. Immunostaining was performed using mouse monoclonal anti-Skp2 antibody. Skp2 mRNA and protein was detectable in every sample studied. Our results showed no significant difference between the pituitary tumors and normal pituitary tissue in Skp2 mRNA or nuclear protein expression. Individual tumor types had similar mRNA expression and variable protein expression. However, samples with high p27 protein expression showed significantly less Skp2 expression than samples with low p27 staining. Our data suggest that increased p27 degradation through the ubiquitin-proteasome pathway could be regulated in pituitary tumors by changes in Skp2 expression, although other factors probably also play a role.
细胞周期蛋白依赖性激酶（CDK）抑制剂p27在发育过程中对细胞增殖的控制起着关键作用，并且与肿瘤发生有关。先前的研究表明，在人类垂体肿瘤中，p27蛋白表达有变化，但mRNA水平没有变化。p27的下降似乎可能是由于通过泛素-蛋白酶体途径的降解增加所致。Skp2（S期激酶相关蛋白）是一种特异性F-box蛋白，它能使磷酸化的p27识别并结合到泛素复合物上。因此，我们研究的目的是探讨Skp2在垂体肿瘤发生中的可能作用。总共对59个人类垂体样本进行了评估，其中7个为正常样本，52个为腺瘤样本，检测Skp2的转录表达；对51个垂体样本进行了蛋白表达评估。对逆转录mRNA的cDNA进行实时RT-PCR，以相对定量Skp2转录本。使用小鼠单克隆抗Skp2抗体进行免疫染色。在所研究的每个样本中都可检测到Skp2 mRNA和蛋白。我们的结果显示，垂体肿瘤与正常垂体组织在Skp2 mRNA或核蛋白表达方面没有显著差异。个别肿瘤类型具有相似的mRNA表达和可变的蛋白表达。然而，p27蛋白表达高的样本显示出的Skp2表达明显低于p27染色低的样本。我们的数据表明，尽管其他因素可能也起作用，但在垂体肿瘤中，通过泛素-蛋白酶体途径增加的p27降解可能受Skp2表达变化的调节。
