Expression Of P27 In Carcinoma Of Stomach And It's Relationship To Cyclin D₁ And Cyclin E

IntroductionCell cycle is the basic program of cell actinvation. Abnormality of cell cycle will induce carcinogenesis. P27 is a new cell cycle inhibitor. It can control cell proliferation through inhibiting multiple cyclin - CDK activity. P27 has close relation with origination ,progression and prognosis of cancers. Apoptosis will lose balance and cell will proliferate when p27 expression decrease. This will accelerate origination and progression of cancer. The porpose of the present study was to detect the expression of p27 and the relativity of cyclin D₁,cyclinE expression in gastric cancer and to provide a new way to diagnose and treat gastric cancer.Materials and MethodsPatients and specimen54 Gastric cancer specimens were selected from paraffin wax embedded specimens with full clinicopathological data. All the patients underwent operations in the 2nd affiliated hospital of China Medical University duiring 2001 -2003 and the postoperative pathologic diagnosis was gastric cancer. All specimens were not treated with chemotherapy and radiotherapy.Main reagentsrabit anti -human p27 monoclonal antibody,mouse anti -human cyclin D, monoclonal antibody ,rabit anti - human cyclinE monoclonal antibody ( zhongs-han Corp. ) , rabit Immunohistochemical staining p - s and DAB ( Maixin Corp. ).Immunohistochemical stainingSpecimens from the paraffin wax blocks were cut into 5|xm sections. The first section was routinely stained with hematoxylin - eosin for histological diagnosis and differentiation. Immunohistochemical staining for p27Ncyclin D^cy-clinE was performed with a standard avidin - biotin - peroxidase complex detection kit. The sections were dewaxed and rehydrated; antigen repair 1. 5 min through high temperature and pressure method with 0.01M PH6.0 citrate buffer solution. Endogenous peroxidase activity and nonspecific bindings were blocked by incubation with 3% hydrogen peroxide and non - immune serum, respectively. Slides were then incubated sequentially with primary antibodies overnight at 4t with a biotinylated secondary antibodies for 30 min and with SP complex for 30 min. Then the chromogen DAB test was performed to be able to localize the positive staining by microscope sequentially. The sections were counterstained with hematoxylin, dehydrated in graded ethanol, cleared in xylene and mounted. Positive staining of breast cancer was used as a positive control. Negative control sections were prepared by substituting primary antibodies with PBS.Evaluation of the resultsThe positive staining was defined as light yellow to brown stain in cytoplasm or nuclei, taked count of 5 highest positive cell HP( x400) , caculate positive rate, prescribed >5% as positive <5% as negative.Statistics analysisSPSS11.5 for windows was used for statistical analysis. Statistical significance was calculated by the x2 test. The level of significance was set at P < 0.05.ResultsPositive immunohistochemistry was seen in 20 cases(37.0% ) of 54 gastric cancer and in 11 cases (73. 3%) of 15 normal gastric tissue. P27 expression had significant difference between gastric cancer and normal gastric tissue, had no relation with sex ^ age N tumor size ? invasive deepth and differerntiation, but had signifiant relationship with TNM staging and lymphnode metastasis. P27 ex-pression had a negative correlation with cyclin Dt (r = -0.332) and no relationship with cyclin E P >0.05.DiscussionAs a cell cycle negative control factor p27 level shifts in different cell stage. In Gj stage p27 has a high expression, while in S stage when DNA syn-thesization achieves the highest level p27 expression obtains the lowest level. P27 protein combined with cyclin - GDK complex can inhibit CDK kinase acti-vaty, then cell mitosis is stopped at Gj stage. P27 level also has significant correlation with cell apoptosis. Some studies have shown that p27 has a low expression in cancer and high expression in normal tissue. Our study found that p27 KIPI positive rate (37. 0% ) in gastric caner was signigicent lower than normal gastric tissue(73. 3% ). This result suggestted p27 KIPI could be a important factor to evaluate gastric cancer malignant degree and prognosis.The signigicant difference of p27 protein expression in gastric cancer and normal tissue suggestted p27 protein expression decrease may due to gastric cancer origination and progression. P27 protein expression is reverse to cyclin E expression. P27 expression decrease and cyclin E increase may promote cancer origination.ConclusionThe difference of p27 expression in gastric cancer and noral gastric tissue was remarkable. P27 protein expression decrease may due to gastric cancer origination and progression. The expression had no relation with sex N age stumor size ^invasive deepth and differerntiation, but had signifiant relationship with TNM staging and lymphnode metastasis. P27 expression had a negative correlation with cyclin D, and no relationship with cyclin E.