Proteome analysis in normal liver, chronic hepatitis, liver cirrhosis and hepatocellular carcinoma-For a novel diagnosis, treatment and protection of hepatocellular carcinoma

在人类癌症中，细胞周期蛋白、细胞周期蛋白依赖性蛋白依赖性蛋白激酶(CDK)及其抑制物(CDKI)经常发生改变。P18^&lt；INK4C&gt；是CDKI中INK4家族的成员，是一种潜在的肿瘤抑制基因产物。然而，p18^&lt；INK4C&gt；在肝细胞癌中的表达仍不清楚。本研究的目的是检测p18^&lt；INK4C&gt；在包括肝细胞癌在内的多种肝病中的表达，并评价其在肝细胞癌中的临床意义。为此，我们用免疫组织化学方法检测了p18^-lt；INK4C&gt；在包括51例肝细胞癌在内的各种肝病中的表达，并研究了p18^-lt；INK4C&gt；表达与视网膜母细胞瘤蛋白(PRB)的磷酸化以及CDK4和CDK6活性水平之间的关系。免疫组织化学分析显示，p18^&lt；INK4C&gt；在肝细胞癌尤其是低分化肝细胞癌中表达频繁缺失。与p18^&lt；INK4C&gt；-阳性相比，p18^&lt；INK4C&gt；表达缺失与预后不良有关。此外，p18^&lt；INK4C&gt；阴性的肝细胞癌中CDK4的Kinas活性高于p18^&lt；INK4C&gt；阳性的肝癌。然而，CDK6活性水平在两组肝癌中是相似的。在p18^&lt；INK4C&gt；阳性的肝癌中，p18^&lt；INK4C&gt；主要与CDK4相互作用，而不是与CDK6相互作用。P18^lt；INK4C&gt；阴性的肝癌中pRb在Ser 780位发生磷酸化的频率高于p18^lt；INK4C&gt；阳性的肝癌。提示p18^&lt；INK4C&gt；表达缺失可能通过上调CDK4活性在肝细胞癌的分化和发展中起作用。

Cyclins, cyclin-dependent kinases (Cdks), and Cdk inhibitors (CdkIs) are frequently altered in human cancer. p 18^<INK4C>, a member of the INK4 family among CdkIs, is a potential tumor suppressor gene product. However, the expression of p 18^<INK4C> in hepatocellular carcinoma (HCC) remains unknown. The aim of this study was to examine the expression of p18^<INK4C> in various liver diseases including HCC and to assess its clinical significance in HCC. To that end, we examined the expression of p 18^<INK4C> by immunohistochemistry in various liver diseases including 51 HCCs, and also studied the relationship among p 18^<INK4C> expression, the phosphorylation of retinoblastoma protein (pRb), and the activity level of Cdk4 and Cdk6. Immunohistochemical analysis revealed the frequent loss of p18^<INK4C> expression in HCC, especially in poorly differentiated HCC. The loss of p18^<INK4C> expression was shown to be associated with a poor prognosis as compared with that associated with p18^<INK4C>-positivity. Further, the kinas activity of Cdk4 was found to be higher in p18^<INK4C>-negative HCCs than in p 18^<INK4C>-positive HCCs. However, the level of Cdk6 activity was similar in the two groups of HCCs. In p18^<INK4C>-positive HCCs, p18^<INK4C> dominantly interacted with Cdk4 rather than with Cdk6. pRb phosphorylated at Ser 780 was detected more frequently in p18^<INK4C>-negative than in p 18^<INK4C>-positive HCCs. These data suggest that the loss of p18^<INK4C> expression may play a role in the differentiation and development of HCC through the upregulation of Cdk4 activity.