Expression And Significance Of Minichromosome Maintenance Proteins 2, 5 And 7 In Ovarian Epithelial Tumors

Ovarian malignant tumor is one of the three kinds of malignant tumors of female genitalia. Owning to the absence of effective early diagnostic method, about 60% of the patients have developed extensive peritoneal metastasis and a great amount of ascites upon diagnosis. Besides, as there is still no effective therapeutic method for patients under advanced stage, the five year survival rate remains at a low level. Therefore, the ovarian cancer has emerged as a great threat to women's life. According to previous reports, the mostly covered significant prognostic indicators include disease stage, tumour grade,histologic type and extent of surgical cytoreduction. However, the fact that significant biological heterogeneity exists in the same prognostic subset will interfere with the accuracy of clinical prognosis. In conclusion, further efforts are needed in the pursuit of ovarian cancer biological behavior related molecular determinants, in order to detect the patients with especially adverse prognosis. Minichromosome maintenance protein is an essential factor for the priming and extention of DNA replication and an important mark for potent cell reproductive activity is the positive expression of MCM. Abnormal expression of this family has been detected in different kinds of tumor tissues, including those of digestive, respiratory, urinary and reproductive system. Furthermore, positive correlation has been determined between the expression level and the cell proliferation degree, while negative correlation between the expression level and the cell differentiation degree. Therefore, MCM has been recognized as an effective indicator for tumor and precancerous change, as well as a reference index for tumor prognostic evaluation. MCM is a more ideal cell proliferation marker, able to reflect the cell reproductive activity in greater accuracy compared to those traditional indexes like PCNA, Ki-67 and etc.In the present study, immunohistochemisty method is employed to examine the expression level of MCM2,5,7 in ovarian epithelial tumor, in order to investigate the relationship between clinical pathological characteristic, common multiplicaiton factor Ki67 and the prognostic condition of the ovarian patients, in an attempt to release the molecular biological and clinical significance.Material and method1. Histological sampleThe samples, collected from pathological department of China People's Liberation Army affiliated 202 Hospital, were paraffin embedded tissue samples of 93 cases of ovarian epithelial tumor, including 55 cases of ovarian epithelial cancer,29 cases of borderline epithelial tumor and 12 cases of benign epithelial tumor. All patients involved had received no chemotherapy, radiotherapy or other anti-cancer therapy. Follow-up study was conducted for all ovarian cancer patients, and the average time course was 30 months, from 8 months (earliest death) to 50 months(the end of follow-up).2. ImmunohistochemistryStreptavvidin-biotin peroxidase was used to examine the expression level of MCM2,5,7 and Ki-67 in 96 cases of ovarian epithelial tumor tissues. Results determination:5 areas with the expression of the biggest density of positive cells and most clear background were selected out of each section under low power lens, and then the number of positive cells was counted out of 100 cells under high power lens for each area. The labeling index was calculated as the average positive cell number of the 5 areas. negative (-) :labeling index<10%; weak positive (+):labeling index 10%-25%; positive (++):labeling index 25%-50%; strong positive (+++):positive cell number≥50%. Positive cell number≥25% was determined as positive case.3. Statistical treatmentSPSS(V13.0) was used for data analysis, including the statistical method of X2 test, Wilcoxon rank test, Spearman rank correlation analysis, Kruskal Wallis test, Mann-Whitney test and Log Rank test. a=0.05 was set as the standard. p<0.05 and p< 0.01 was recognized respectively as with statistical significance and great significance.Result1. Expression of MCM2, MCM5, MCM7 and Ki-67 in ovarian epithelial tumorsThe staining areas were mostly located in the nucleus. Immunoreactivity for MCM-2, MCM-5,MCM-7 and Ki-67 LI was seen in all cases with the mean of 17.04%,19.79%,21.19%和15.45%, respectively. The pattern of staining was mostly in nuclear, although a faint cytoplasmic staining was seen in some cases, which was disregarded during evaluation. Significant difference was detected between the population distribution of the median of MCM2,5,7 and Ki-67LI in benign tumor (3.58%,4.50%,4.42%和3.58%, respectively), borderline tumor (6.52%,8.00%, 9.21%和5.38%, respectively) and adenocarcinoma (25.53%,29.35%,31.18%和23.36%, respectively) (Kruskal-Wallis test, P<0.001). The expression of MCM2,5,7 and Ki-67 displayed significant difference between adenocarcinoma, benign tumor and borderline tumor, while only the expression of MCM7 showed the significant difference between borderline and benign tumor (P=0.002)2. The correlation between the expression of MCM2, MCM5 and MCM7 in ovarian epithelial tumors and multiplicaiton factor Ki-67.A positive correlation was established between MCM2,5 or MCM-7 expression level and Ki-67 LI (Spearman's r>0.9, P<0.0001 for both), which remained after stratification of our cases into benign, borderline or adenocarcinoma categories. According to correlation coefficient, the strongest correlation was determined between Ki-67LI and MCM2LI.3. The correlation between the expression of MCM2, MCM5 and MCM7 in ovarian epithelial tumors and the patients clinical pathological characteristic.The labeling index of MCM2,5,7 increased with high grade, and a total difference was detected between tumors with different differentiation degree(1 vs 2 vs 3, Kruskal-Wallis test:P<0.001 for all). MCM2,5,7 LI displayed a total difference between different patients with clinical staging (ⅠvsⅡvsⅢvsⅣ, Kruskal Wallis test: P<0.001 for all). According to Mann-Whitney test, significant difference was determined in MCM5LI and MCM7LI betweenⅢandⅣ(P<0.001), while the other two indexes showed no difference.4. The correlation between the expression of MCM2, MCM5 and MCM7 in ovarian epithelial tumors and the patients prognostic conditionThe median survival time in MCM2 expression negative group was 43 months, and 35.4 months in positive group. According to Log Rank, Chi-square value was 8.605, p=0.003<0.05, therefore significant difference in the survival time was determined between the two groups, with higher value in negative group. The median survival time in MCM7 expression negative group was 40.7 months, and 29 months in positive group. According to Log Rank, Chi-square value was 14.595, p=.000<0.05, therefore significant difference in the survival time was determined between the two groups, with higher value in negative group.Conclusion1. The expression level of MCM2, MCM5 and MCM7 increased in gradual manner with the cell differentiation degree, from normal to cancer cell, which could help us to distinguish the nature of ovarian epithelial tumor.2. The expression level of MCM2, MCM5 and MCM7 proteins displayed significant difference between different clinical staging and tumor differentiation degree in ovarian carcinoma, and the level increased with the higher staging, but decreased with higher differentiation degree.3. MCM2, MCM5 and MCM7 might be able to serve as an independent index for assistant evaluation of the adverse prognosis of ovarian cancer.4. MCM2, MCM5 and MCM7 are effective markers for cell proliferation.