| Objective Based on the establishment of spontaneous breast tumor in SD rats model.Then to investigate the expression of mitochondrial cytochrome c-mediated apoptotic pathway related factors in the SD rats spontaneous breast cancer.Methods This experimental study is divided into two parts. The first part is about spontaneous breast cancer screening of SD rats:130 SPF Spargue-Dawley rats (♀:♂=1:1) were fed in a specific pathogen free (SPF) breeding barrier. Then collect the occurrence of spontaneous breast tumors and histopathology was carried out to identify the types of tumors. Afterwards they were divided into 3 groups:normal breast tissues, begin tumors tissues and malignant tumors tissues. The second part of study is investigate the expression of mitochondrial cytochrome C-mediated apoptotic pathway related factors in SD rats spontaneous breast cancer:Expression of Bcl-2、Bid、P53、AIF、Cyt C、 Apaf-1、 Caspase-3、 XIAP in protein level and mRNA level were detected by using Immunohistochemistry (IHC) and RT-PCR methods.Results Among these 130 SD rats,14 rats were observed having spontaneous mammary neoplasm with the incident rate of 10.77%, femal cancer incidence was 21.54%. In these neoplasm cases,7 cases were mammary fibroadenomas,7 cases of breast carcinoma, and the incident rates were 5.38%, femal cancer incidence was 10.77%.The upstream factors of mitochondria apoptosis pathway:The immunohistochemical results showed that the expression of Bcl-2 protein have significant differences, benign breast tumor in the quantity of protein expression is significantly higher than normal breast tissue (p<0.05);the expression in malignant breast tumor significantly higher than those. Bid protein was strong positive expression in normal breast tissues, the positive expression rate was significantly higer than benign tumor and malignant breast tumor (p<0.01).At the same time, the relative expression levels of Bid mRNA in group Ⅰ、Ⅱ、Ⅲ ranging from strong to weak, it has the same trend with expression of protein. P53 protein have some expression in normal breast tissues, the expression of benign breast tumor is significantly higher than normal breast tissue(p<0.05),the expression of malignant breast cancer is statistically higher(p<0.01). the relative expression levels of Bid mRNA in group Ⅰ、Ⅱ、 Ⅲ ranging from weak to strong, it has the same trend with expression of protein, the difference was statistically significant(p<0.01).Then the middle factors AIF protein have high expression in normal breast tissues, the positive expression rate was significantly higher than benign tumorand malignant breast tumor, the difference was statistically significant(p<0.01). the relative expression levels of AIF mRNA in three group ranging from strong to weak, it has the same trend with expression of protein, the difference was statistically significant(p<0.01). The positive expression of Cyt C protein in benign breast tumor was significantly higher than normal breast tissues and malignant breast tumor, the difference was statistically significant(p<0.01). in addition, the expression in normal breast tissues was significantly higher than malignant breast tumor, the difference was statistically significant(p<0.05). the relative expression levels of AIF mRNA in three group ranging from high to low, it has the same trend with expression of protein, the difference was statistically significant(p<0.01). Apaf-1 protein was strong positive expression in normal breast tissues, the positive expression in benign breast tumor significantly lower than it; the positive expression in malignant breast tumor was significantly higher than benign breast tumor but lower than normal breast tissues, the difference was all statistically significant(p<0.01). the relative expression levels of Apaf-1 mRNA in group Ⅰ、Ⅱ、Ⅲ ranging from strong to weak, it has little difference trend with expression of pretein, it was may related to transcription and translation are not in sync.Last is the downstream factors:Caspase-3 protein have high expression in normal breast tissues, the positive expression rate was significantly higher than benign tumor and malignant breast tumor,and the express in benign breast tumor higher than malignant breast tumor, the difference was statistically significant(p＜0.01). the relative expression levels of Caspase-3 mRNA in three group ranging from strong to weak, it has the same trend with expression of protein, the difference was statistically significant(p＜0.01). XIAP protein have some expression in normal breast tissues, the expression of benign breast tumor is higher than normal breast tissues, the expression of malignant breast cancer is statistically higher(p<0.01). the relative expression levels of XIAP mRNA in group Ⅰ、 Ⅱ、Ⅲranging from weak to strong, it has the same trend with expression of protein, the difference was statistically significant(p<0.01).Above the result, we can see the critical factors protein and mRNA in middle and lower reachers of mitochondrial apoptotic pathways all have statistically significant difference among the three group, showed that mitochondrial apoptotic pathways involved in the occurrence of breast tumor.Conclusion Mammary tumor was the most common spontaneous neoplasm in SD rats, and female middle-aged the majority. It’s similar to humor breast cancer incidence, suitable for human breast-tumor related research. The expression of mitochondrial apoptosis pathway key factors Bcl-2. Bid、P53、AIF、Cyt C、APAF-1、Caspase-3、XIAP, not only protein but also mRNA levels have significantly difference,it show that they might be correlated with the carcinogenesis and development of breast cancer. |
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