Shapira Ma'anit, Ben-Izhak Ofer, Bishara Bishara, Futerman Boris, Minkov Ira, Krausz Michael M, Pagano Michele, Hershko Dan D
Department of Surgery A, Rambam Medical Center, Technion-Israel Institute of Technology, Haifa, Israel.
Cancer. 2004 Apr 15;100(8):1615-21. doi: 10.1002/cncr.20172.
Low levels of p27(Kip1) are associated with high aggressiveness and poor prognosis in various malignancies, including colorectal carcinoma. The authors showed that S phase kinase protein 2 (Skp2), the specific ubiquitin ligase subunit that targets p27(Kip1) for degradation, was overexpressed and was inversely related to p27(Kip1) levels in patients with colorectal carcinoma. The essential role of cyclin kinase subunit 1 (Cks1) in Skp2-dependent p27 degradation was recently discovered, but its role in human malignancies is unknown.
Quick-frozen colorectal tumor samples from 30 patients were separated by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, transferred to nitrocellulose, and probed with highly specific monoclonal antibodies directed against Cks1, Skp2, and p27(Kip1). The expression of Cks1 was also examined by immunohistochemistry using formalin-fixed, paraffin-embedded tissue sections from the same patients.
A strong correlation was found between Cks1 levels and Skp2 expression and loss of tumor differentiation. A significant inverse relation was also observed between levels of Cks1 and p27(Kip1) and overall survival.
The results of the current study suggest that increased expression of Cks1 may have an important causative role in decreasing levels of p27 in patients with aggressive colorectal carcinoma.
在包括结直肠癌在内的多种恶性肿瘤中，p27（Kip1）水平较低与高侵袭性和不良预后相关。作者发现，作为靶向p27（Kip1）进行降解的特异性泛素连接酶亚基，S期激酶相关蛋白2（Skp2）在结直肠癌患者中过表达，且与p27（Kip1）水平呈负相关。细胞周期蛋白激酶亚基1（Cks1）在Skp2依赖的p27降解中的重要作用最近被发现，但其在人类恶性肿瘤中的作用尚不清楚。
对30例患者的结直肠肿瘤速冻样本进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离，转移至硝酸纤维素膜上，并用针对Cks1、Skp2和p27（Kip1）的高度特异性单克隆抗体进行检测。还使用同一患者的福尔马林固定、石蜡包埋组织切片通过免疫组织化学检测Cks1的表达。
发现Cks1水平与Skp2表达及肿瘤分化丧失之间存在强相关性。在Cks1水平与p27（Kip1）水平及总生存率之间也观察到显著的负相关。
本研究结果表明，Cks1表达增加可能在侵袭性结直肠癌患者p27水平降低中起重要的致病作用。
