Semi-quantitative Analysis Of The CYP1A1, CYP1B1 And COMT MRNA Expression In Peripheral Blood Lymphocytes From Endometrial Cancer

Objective: Endometrial cancer is a common malignancy in gynecology, which is known as an estrogen-dependent cancer. It is believed that exposure to estrogens, which is not opposed by progesterone, increases the risk of developing endometrial cancer. Cytochrome P4501A1 and 1B1 are involved in estrogen metabolism,whose metabolites are associated with the initiation and progression of cancer. COMT converts those metabolites to innoxious substances and clears them from the body. Therefore these three enzymes play a role in the metabolism of estrogen and are important for endometrial carcinogenesis. This study was designed to investigate the association between CYP1A1, 1B1 and COMT mRNA expression and endometrial cancer.Methods: The population-based case-control study included 48 endometrial cancer patients and 53 healthy controls. Five milliliter of venous blood from each subject was drawn in vacuum tubes containing EDTA while the information of every subject was obtained. Total RNA was extracted and the mRNA expression levels were measured by using semi-quantity reverse transcriptase polymerase chain reaction (RT-PCR) analysis.Statistical analysis was performed using SPSS11.5 software package. P<0.05 was considered significant for all statistical analysis. The t-test was used to examine the difference of ages between cases and controls. The normality of mRNA expression level was analyzed by the test of normality. Comparison of two groups was performed by the t-test and three groups by the One-Way ANOVA. The odds ratio (OR) and 95% confidence interval (CI) were calculated using an unconditional logistic regression model.Results:1. The age difference was not significant between the endometrial cancer patients and healthy controls (P=0.976). The distributions of the CYP1A1, 1B1å’ŒCOMT mRNA expression were normal.2. The expression of CYP1A1 and CYP1B1 mRNA in the endometrial cancer patients were significantly higher than healthy controls (P=0.008, P=0.000). But, no significant difference was found on the expression of COMT mRNA between two groups (P=0.708). Since COMT catalyzes the products of CYP1A1 and CYP1B1, the ratios between the expression of CYP1A1 mRNA and COMT mRNA as well as between CYP1B1 mRNA and COMT mRNA were calculated. The CYP1B1/COMT in the endometrial cancer patients were significantly higher than controls (P=0.002), but CYP1A1/COMT in two groups were not (P =0.560).3. According to the means of the CYP1A1,CYP1B1 and COMT mRNA expression as well as CYP1A1/COMT and CYP1B1/COMT, the endometrial cancer patients and healthy controls were divided into high and low expressers respectively. The proportion of CYP1B1 mRNA high expressers in the endometrial cancer patients was significantly higher than the healthy controls (P=0.000). Compared with the low level, the CYP1B1 mRNA high level could increase the risk of endometrial cancer, the odds ratio (OR) was 4.727(95%CI=1.975~11.300). High level of CYP1B1/COMT could also increase the risk of endometrial cancer (P=0.026, OR=2.563 , 95%CI=1.109~5.925). No associations were found between the CYP1A1, COMT mRNA expression, CYP1A1/COMT and endometrial cancer respectively.4. According to the surgery- pathological stage, the endometrial cancer patients were divided into 24 early patients and 18 advanced patients. The expression of CYP1A1 mRNA in the advanced patients was lower than that of the early patients, but there was no significant difference between them (P=0.742). The CYP1B1 mRNA expression in the endometrial cancer patients was significantly higher than that in the healthy controls (P=0.023). According to means of the CYP1A1,CYP1B1 and COMT mRNA expression as well as CYP1A1/COMT and CYP1B1/COMT, the early patients and advanced patients were divided into high or low expressers respectively. The proportion of CYP1B1 mRNA high expressers in the advanced patients was higher than that of the early patients and there was significant difference between them (P=0.038). Compared with the low level, the high level could increase the risk of developing endometrial cancer, the odds ratio was 3.816 (95%CI=1.047~13.910). No associations were found between the CYP1A1,COMT mRNA expression, CYP1A1/COMT, CYP1B1/COMT and clinical stage respectively.5. There are 28 shallow myometrial invasion patients and 10 deep myometrial invasion patients. The CYP1A1,CYP1B1 and COMT mRNA expression as well as CYP1A1/COMT and CYP1B1/COMT were not significantly different between two groups.6. Simultaneously, the gene polymorphisms of 36 endometrial cancer patients were tested in another experiment. Only COMT genotype affected mRNA expressions. The mRNA expression in patients with COMT wild genotype (G/G) was lower than that in the patients with the heterozygous genotype (G/A) and homozygous genotype (A/A). The difference was significant (P=0.047). The gene polymorphism of the CYP1A1 MspI, CYP1B1 Ala119Ser, Leu432Val was not associated with the CYP1A1 and CYP1B1 mRNA expression.Conclusions:1. The CYP1A1 mRNA expression in peripheral blood lymphocytes from endometrial cancer was increased, but the risk of developing endometrial cancer was not confirmed. The association between the CYP1A1 mRNA expression and surgery - pathological stage as well as myometrial invasion was also not confirmed.2. The CYP1B1 mRNA expression and CYP1B1/COMT in peripheral blood lymphocytes from endometrial canner was increased, and it may increase the risk of developing endometrial cancer. Further study showed that the CYP1B1 mRNA expression in peripheral blood lymphocytes from advanced patients was increased and it may increase the risk of developing advanced endometrial cancer. But the associations between CYP1B1 mRNA expression as well as CYP1B1/COMT and myometrial invasion were not confirmed.3. The COMT mRNA expression in peripheral blood lymphocytes from endometrial cancer was not increased or decreased and further study doesn't show any association between the COMT mRNA expression and the risk of developing endometrial cancer, surgery - pathological or myometrial invasion stage.4. In the simultaneous study of COMT gene polymorphism, the individuals with wild genotype (Val108/158Val) expressed lower COMT mRNA than ones with the heterozygous genotype (Val108/158Met) and homozygous genotype (Met108/158Met). Since the correlation among COMT mRNA expression, COMT gene polymorphism and endometrial cancer was not confirmed, the effect of lower COMT mRNA to the endometrial cancer was uncertain.