Expression Of Skp2 And P27～(kip1) As Well As Its Relationship With Proliferation Activity In Oral Squamous Cell Carcinoma

The regulation of cell-cycle and cell proliferation is decided by the phase change of cell-cycle regulatory proteins, while the abundance of cell-regulatory proteins is decided by the expression of related genes and proteins degradation. It is well known that the proliferation and progression of cancer cells are closely related to abnormalities of various positive and negative cell cycle regulators, so studying the proteolysis of these proteins is important to understanding the mechanism of the proliferation and progression of cancer cells. Skp2 (S-phase kinase associated protein 2) target many ubiquitin-mediated degradation of Gl- and S-phase regulators. p27Kipl, which is a Cdk inhibitor and plays an important role in negative regulation of the cell-cycle during GO and Gl phases, is specifically recognized as and targeted for ubiquitination by Skp2. Skp2 binds to and mediates the ubiquitylation of CKI p27Kipl, through which Skp2 plays an important role in cell-cycle and cell proliferation. Skp2 is thought to be an oncogene now. Oral squamous cell carcinoma (OSCC) is the most frequent malignant neoplasm of the head and neck region, but the research on the mechanism of Skp2 in OSCC is still rare. ObjectiveThe aim of this study is to investigate the expression of Skp2 and p27kipl in OSCCand the correlation between them, to assess the relationship between them and proliferation activity, clinicopathologic parameters, to evaluate their roles in tumorigenesis and progression of OSCC, and to understand the biological character of OMFS, so as to provide a potentially new way for early diagnosis, prognosis assessment and treating of OSCC. MethodsPV-9000, a two-phase immunohistochemistry technique, was used to determine the expression of Skp2, p27kipl, and Ki-67, in 58 OSCC tissues, 19 epithelial dysplasia tissues and 12 normal oral mucosa tissues. The proliferation activity of them was detected by labeling indexes (LI) of Ki-67. Statistical analysis was performed using SPSS 11.0 software, with Wilcoxon test, Kruskal-Waillis test. Possible correlations between variables of the analyzed tumor samples were examined by Spearman test, a =0.05 was specified for significance. Results1. The positive immunostaining of Skp2, Ki-67 was observed in the nucleus. Skp2 staining in well differentiated carcinomas is confined to the peripheral cells of tumor islands, and increased Skp2 staining in poorly differentiated carcinoma is interspersed or congregated. Compared with Skp2, Ki-67 is more focused towards the active proliferation regions. The positive immunostaining of p27Kipl was mainly observed in the nucleus with only few cytoplasmic staining. P27Kipl staining in well differentiated carcinomas is reduced in the peripheral cells but increased in the central areas of tumor islands, and p27Kipl staining in poorly differentiated carcinoma is remarkably reduced.2. The positive immunostaining ratio of Skp2 was significantly higher in OSCC (93.1%) than those in epithelial dysplasia (20.5%) and normal oral mucosa (16.7%) (P<0.05). In highly, moderately and poorly differentiated OSCC groups, the positive rates of Skp2 expression were 88.0%, 95.7% and 100.0% respectively, and a statistical significance was observed among them(jP<0.05). There were significant differences between the group with lymph node metastasis and the group without (P<0.05). No correlation was observed between expression of Skp2 protein and the otherclinicopathologic parameters of OSCC (f^O.05).3. In OSCC, epithelial dysplasia and normal oral mucosa groups, the positive rates of p27Kipl expression were 29.3%, 68.4% and 91.7%, respectively, and a statistical significance was observed among them (P<0.05). The expression of p27Kpl protein was significantly reduced in poorly differentiated OSCCs (0.0%) compared with moderately (21.5%) and highly differentiated OSCCs (48.0%). There were significant differences between the group with lymph node metastasis and the group without lymph node metastasis (P<0.05). No correlation was observed between expression of p27Kipl protein and other clinicopathologic parameters of OSCC (P>0.05).4. Spearman rank correlation analysis showed a strong inverse correlation between Skp2 and p27 LI for OSCCs (rs=-0.859, P<0.00l).5. The positive immunostaining ratio of Ki-67 was significantly higher in OSCC (100%) than that in epithelial dysplasia (84.2%) (P<0.05), and the positive ratio in OSCC was significantly higher than that in normal oral mucosa (66.7%) (P<0.05). Ki-67 protein was significantly overexpressed both in poorly differentiated and moderately differentiated OSCCs compared with highly differentiated OSCCs (P<0.05). There were significant difference between the group with lymph node metastasis and the group without lymph node metastasis (P<0.05). No correlations were observed between expression of Ki-67 protein and the other clinicopathologic parameters of OSCC (F>0.05).6. Spearman rank correlation analysis showed a positive correlation between Skp2 and Ki-67 LI (rs=0.762, /M).001) and an inverse correlation between p27Kipl and Ki-67 LI (r5=-0.604, F<0.001) for OSCCs.Conclusions1. The mechanism of abnormal Skp2 may contribute to the malignant phenotype during oral epithelial carcinogenesis. Within OSCCs, the expression of Skp2 protein increases as the grades of differentiation worsen. The higher expression of Skp2 protein, the more probability of lymph node metastasis.2. The abnormal expression of p27Kipl protein may be an important event duringoral cancer development. There was a general trend of increased expression of Skp2 protein associated with oral epithelial carcinogenesis.3. There was a significant inverse correlation between expression of Skp2 and p27Kipl protein, suggesting that Skp2 played an important role in the expression of p27Kipl protein.4. OSCC has stronger potential of proliferation than epithelial dysplasia and normal oral mucosa.5. Skp2 and p27Kpl may play important roles in tumor cell proliferation. The expression of Skp2 has a positive correlation with that of Ki-67, while there was a negative correlation between the expression of p27Kipl and Ki-67.