The Abstract purpose Chk1 / 2 (checkpoint kinase 1,2) and Plk1 (polo  like kinase 1) various cell cycle checkpoint to start DNA damage repair kinase This study examined three kinases in endometrial cancer and normal expression in the endometrial tissue, to explore the three kinds of protein expression differences between the clinical and pathological features of endometrial cancer, and three kinds of protein expression correlation. Methods Immunohistochemical SP method detected 44 endometrial cancer tissues and 21 cases of normal endometrial tissue in Chk1, Chk2 and Plk1 protein expression. Results, the positive rate of Chk1, Chk2 and Plk1 protein in endometrial cancer patients were 47.7%, 75.0% and 31.8%, respectively, the normal endometrial positive rates were 61.9%, 61.9% and 4.8%; of Plk1 protein 0.05)。">expression in endometrial cancer tissues was significantly higher than the normal endometrial tissue (P <0.01), while the expression of Chk1, Chk2 was no significant difference (P> 0.05). 0.05);但Chk1的表达在不同分化程度的子宫内膜癌患者">Chk1, Chk2 and Plk1 protein expression in endometrial cancer patients of different age, pathological type and clinical stage the difference was not statistically significant (P> 0.05); of Chk1 expression of endometrial cancer in patients with various degrees of differentiation in the difference was statistically significant (P <0.01). Spearman rank correlation analysis, 44 endometrial cancer, Chk2 and Plk1 expression was positively correlated (r = 0.482, P = 0.001). Conclusion Plk1 may be ideal therapeutic target for endometrial cancer, and CHK1 / 2 expression in endometrial cancer and its significance remains to be further studied.

Key words Chk1 Chk2 of Plk1 endometrial cancer

   Endometrial cancer (endometrial carcinoma, EC) is a common malignant tumors of the female reproductive system, according to the American Cancer Society, the United States in 2005 cases to 40,880 cases, while the 7,310 patients will die from the disease [1]. But it is so far unclear etiology and pathogenesis of endometrial cancer. The cell cycle checkpoint kinase 1,2 (checkpoint kinase 1,2, Chk1, Chk2) is the major kinase, cell cycle checkpoints (G1 / S, S and G2 / M) play a role in cancer radiotherapy, chemotherapy-induced DNA damage have a repair [2]; polo-like kinase 1 (polo  like kinase 1, Plk1) is a highly conserved serine / threonine kinase, the normal cell cycle, the centrosome maturation and tumorigenesis important. But this is less three checkpoint kinases expression in tumor tissue, endometrial cancer is no research. In this study, the use of immunohistochemical methods to detect Chk1, Chk2 and Plk1 protein expression in endometrial cancer and normal endometrium, three different species of cell cycle protein expression differences in the two discussed with endometrial cancer clinical pathological features, provide the basis for clinical treatment.

    1 Materials and Methods

    1.1 General Information

    Randomly selected from our hospital in April 2000 to 44 cases of endometrial cancer diagnosed in June 2002. Serous cystadenocarcinoma 22 cases, 15 cases of mucinous cystadenocarcinoma, endometrioid carcinoma cases, two cases of vegetative cell carcinoma, the other three cases. Histological grade: 26 cases of well-differentiated, moderately differentiated 11 cases, poorly differentiated seven cases. Reference to the International Federation of Gynecology and Obstetrics (FIGO) standard clinical staging: Ⅰ 10 cases, II in 14 cases, 11 cases, Ⅲ, Ⅳ of nine cases. Age 24 to 80 years old, with a median age of 48 years old. Organization of 21 cases randomly selected normal endometrial surgical resection in our hospital in 2002, aged 20 to 69 years, with a median age of 42 years old. The above pathological examination of patients were not receiving chemotherapy and radiotherapy.

    1.2 Immunohistochemical detection of protein expression

    Mouse anti-human Chk1 monoclonal antibody (dilution 1:200), mouse anti-human, Chk2 mAb (diluted 1:100) and mouse anti-human the Plk1 mAb (diluted 1:100) were Santa Cruz, USA products; SP kit, reagent DAB purchased from Beijing Zhongshan. Immunohistochemical staining SP kit instructions PBS instead of primary antibody as a negative control, known positive piece as a positive control. Chk1, Chk2 and Plk1 is expressed mainly in the nucleus, the part of the expression in the cytoplasm. According to the coloring degree denoted 0, 1, 2, 3. Positive cells <10% recorded 0 points, 10 percent to 24 percent scored 1 point, from 25% to 49% 2 points, 50% to 74% three points ≥ 75% recorded. Overall judgment taken tinctorial strength and the plot of the percentage of positive cells scores: 0 point referred to as (-), 1,2 stars referred to as (+) 3,4 stars referred to as referred to as (+ +), 6,8% ( + + +), 9,12 points referred to as (+ + +); (-) and (+) is defined as negative, i.e. low expression (+ +) to (+ + + +) was defined as positive that is highly expressed.

    1.3 statistical methods

    SPSS11.5 software χ2 test and Spearman rank correlation analysis, define P <0.05 for the difference was statistically significant.

    2 Results

    2.1 protein expression in endometrial cancer and normal endometrial tissue

    44 cases of endometrial cancer, Chk1 positive rate was 47.7%, Chk2 positive rate of 75.0% of Plk1-positive rate was 31.8%. 21 cases of normal endometrial tissue Chk1, Chk2 and Plk1-positive rate of 61.9%, 61.9% and 4.8%, respectively. Chk2 and Plk1 in endometrial carcinoma were significantly higher than normal endometrial tissue, which Plk1 expression difference was statistically significant (P <0.01), but Chk2 expression was no significant difference (P> 0.05 ), Table 1, Figure 1.

    2.2 three protein expression of endometrial cancer in patients with clinical pathological features of the relationship between

    Statistical analysis showed that Chk1, Chk2 and Plk1 expression of endometrial cancer patient age, histopathologic type and clinical stage (P> 0.05). However, the of Chk1 expression of differences in the different degree of differentiation of endometrial cancer was statistically significant (P <0.01), as shown in Table 2. Table 1 three proteins expressed in endometrial carcinoma and normal endometrial tissue

2.3 three proteins expressed in endometrial carcinoma.

    44 endometrial cancer Chk1, Chk2 and Plk1 protein expression levels do the Spearman rank correlation analysis revealed: Chk2 and Plk1 positive correlation, r = 0.482, P = 0.001; Chk1 and Chk2 and Chk1 and Plk1 no correlation (statistical parameters were r = 0.146, P = 0.344 and r = 0.262, P = 0.096). Chk2 and Plk1 protein expression on the existence of close ties.

    a: Chk1 protein expression in the nucleus and cytoplasm of endometrial cancer; b: Chk2 protein expression in the nucleus and cytoplasm of endometrial cancer;

    c: Plk1 protein positive expression in endometrial cancer tissue, expressed mainly in the nucleus, the part of the expression in the cytoplasm; negative d: of Plk1 protein in normal endometrial tissue Table 2 three cell cycle checkpoint kinase protein expression the relationship between the expression of endometrial cancer in patients with clinical and pathological features

3 Discussion

    Previous studies have shown that endometrial cancer is a tumor Chk 1/2 defects, the study found no significant differences Chk1 and Chk2 protein expression in endometrial carcinoma and normal endometrial tissue. 3 kinase protein expression with clinical and pathological features of endometrial cancer were statistically analyzed based only Chk1 expression difference was statistically significant in patients with different degree of differentiation of endometrial cancer, lower differentiation The higher the expression, suggesting that Chk1 play some role in the development of poorly differentiated endometrial cancer. This result is due to fewer cases needs further studies.

    Plk1 is a highly conserved serine / threonine kinase involved in cell cycle centrosome maturation, spindle formation and chromosome separation process [3], when DNA damage, Plk1 detected in M ​​phase point play a role, so that the cell cycle arrest at M phase. Important mechanism after radiotherapy or chemotherapy, the tumor cell DNA damage will be blocked at each of these cycle checkpoint objectively cell survival conditions, clinical tumor radiation resistance and resistance to chemotherapy [4 ]. Detected by immunohistochemistry of Plk1 expression in endometrial cancer tissues was significantly higher than in normal endometrial tissue expression, with statistical significance, consistent with previous reports [5,6], indicating that this protein has a relatively on the expression of tumor-selective, better targeting specificity, and no obvious expression of Plk1 in benign lesions, indicating that Plk1 may be ideal therapeutic target for endometrial cancer.

    Chk1, Chk2 and Plk1 protein expression levels of 44 endometrial cancer patients do the Spearman rank correlation analysis found a positive correlation between: Chk2 and Plk1. Both play a similar role in the facts. But both have a different expression levels and endometrial cancer patients with clinical and pathological features of the relationship, both also differences.

    In summary, Plk1 expression in endometrial cancer tissue than normal endometrial tissue, suggesting that Plk1 may can become the ideal endometrial cancer targeted therapeutic targets. Further, since the Plk1 complementary in function Chk2 exist, the former function in the M phase, and the latter function in the G1 / S, S, G2 / M period, combined inhibition of both may be more promising endometrial cancer treatment strategy. Chk1 / 2 expression in endometrial cancer and needs further study.