Significance Of P57～(KIP2) Protein And Proliferating Cell Nuclear Antigen In Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant neoplasms in the world, as the second morbidity in cancers in China. Its tumorigenesis and progression is a complex process involved of multigene and multiprocedure. How to control the growth of HCC cells and inhibit the development, recurrence and metastasis of HCC remain to be elucidated. The abnormality of mammalian cell cycle regulation is closely associated with genesis and progression of tumors, which has been a focus of oncological research at present. Cyclins, cyclin-dependent kinases (CDKs) and cyclin-dependent kinase inhibitors (CKIs) play important roles in controlling major check points in the cell cycle. Progression through the cell cycle is catalyzed by cyclin-CDK complexes. CKIs are negative regulators of cell cycle progression by binding the cyclin-CDK complexes and inhibiting the CDKs activity. CKIs includes INK4 family and CIP/KIP family. p57^KIP2 protein is an important member of CIP/KIP family, a potent tight-binding inhibitor of several G1 cyclin-CDK complexes, and a negative regulator of cell proliferation. Detection of p57^KIP2 protein in tumor tissues conduces to judge proliferative activity of tumor cells and to evaluate prognosis indirectly. Proliferating cell nuclear antigen (PCNA) is a nuclear protein, which expresses only in proliferative cells. The expression is closely related to the proliferative state of the cell. In this study, we detected the expression of p57^KIP2 protein and PCNA by immunohistochemistry method in 65 HCC specimens during operation to investigatetheir roles in the carcinogenesis and progression of HCC, the relationship between these two genes, as well as the clinicopathological significance of these two genes. Materials and MethodsSpecimens of HCC were obtained from 65 patients who underwent surgery. Adjacent noncancer liver tissues (ANLT) were also obtained from 38 cases of them. There were 44 males and 21 females, aged from 32 to 72 years old(mean:50.7 years old). AFP level of 47 patients (72.3%) exceeds 400ng/ml, HBsAg of 49 patients (75.4%) was positive. The diameters of tumor ranged from 2cm to 18cm (mean 7.0cm). Tumors were graded according to the Edmondson-Steiner criteria: Grade I, 11 samples; Grade II, 20 samples; Grade III, 26 samples; Grade IV, 8 samples. 37 samples were well encapsulated, 26 samples had portal vein thrombosis. According to clinicopathological feature of HCC, the cases were divided into highly invasive HCC group (43samples) and low invasive HCC group (22samples). The case was classified into highly invasive HCC group if it had one of the following characteristics: 1) With portal vein thrombosis; 2) With more than 2 tumors or numerous satellite tumors at the periphery of the major tumor within one hepatic lobe or the capsule was damaged; 3) With lymphatic node metastasis in the hepatic portal. None of the patients had received radiotherapy, chemotherapy, immunotherapy or transcatheter arterial chemoembolization before operation. 5 cases of laceration injury of liver were used as normal controls. Immunohistochemical staining of p57HP2 protein and PCNA were detected with S-P (Streptavidin-Peroxidase) method. It was considered as positive expression of p57 if its labeling index (LI) was more than 15%; It was taken as highly expression of PCNA if its LI was more than 25%. Statistical analysis was executed by SPSS 10.0 software, P value less than 0.05 were considered significant. Results1. p57K3p2 protein showed positive expression in 5 normal hepatic tissues while PCNA showed negative in them.2. Positive expression of pS?101*2 protein was detected in 34 of 65 HCC samples (52.3%) . and in 30 of 38 ANLT(78.9%). High positive expression (LI^25%) of PCNA was detected in 31 of 65 HCC samples (47.7%) and only in 2 of 38 ANLT (5.3%).3. There was no obvious relationship between pSl*1*2 protein and age, sex, AFP or HBV infection (P>0.05). Positive expression of pS?10^ protein was detected in 19 of 44 HCCs (43.2%) with tumor diameter over 5cm and 15 of 21 HCCs (71.4%) with tumor diameter less than 5cm, and there was a significantly statistical difference (P<0.05). The p<57KiP2 positive-expression rate was 67.7%(21/31) in well-differentiated group (Grade I and Grade II) and higher than 38.2%(13/34) in poor-differentiated group (Grade III and Grade TV) (P<0.05). Moreover, it was more frequent in tumors with intact capsula or without portal embolus than in tumors with poor capsula or with portal embolus (P<0.05). The p57KIP2 positive-expression rate was 39.5%(17/43) in highly invasive group and lower than 77.3%(17/22) in low invasive group (P<0.01).4. The high-expression (LI^25%) of PCNA was not significantly linked to age, sex, AFP, HBV infection or tumor size (P>0.05). Whereas PCNA was highly-expressed (LI ^25%) in 9 of 31(29.0%) well-differentiated HCCs and in 22 of 34(64.7%) poor-differentiated HCCs. There was a significant difference between them(P<0.05). Furthermore, it was more frequent in tumors with poor capsula or portal embolus than in tumors with intact capsula or without portal embolus (P<0.05). And PCNA high-expression rate was 60.5%(26/43) in highly invasive group and lower than 5.3%(5/22) in low invasive group (P<0.01).5. The expression of p57KIP2 protein had negative correlation with that of PCNA (P < 0.05).Conclusion1. The positive-expression rate of p57KIP2 protein in HCC samples was significantly lower than that in ANLT or normal hepatic tissues. This abnormality may play a role in the tumorigenesis and progression of HCC.2. Abnormal expression of pSl*1*2 protein was closely associated with the pathologicalgrade, portal vein thrombosis and capsulae, as well as tumor size. Detecting p57 protein may be used to predict malignant degree and evaluate prognosis of HCC. 3. PCNA was not expressed in normal hepatic tissues. However, it was upregulated in HCC, and was significantly linked to the pathological grade, portal vein thrombosis and capsulae. It strongly suggested that PCNA was closely associated with malignant degreeand invasion metastasis of HCC, which help us evaluated prognosis indirectly.4. In HCC, the expression of p57 protein showed negative correlation with PCNA,indicating that they might have coordinated effects in tumorigenesis and progression ofHCC.