The Effect Of Oophorectomy On The Carcinogenesis Of Breast Cancer Induced By DMBA In Female SD Rat

Objective: The development of breast cancer is a multi-stage graduallyprocess, there are many factors involved in, chemical carcinogenic agents isone of the carcinogenic factors. The7,12-dimethylbenz[a]anthracene (DMBA)is a common chemical carcinogen in animal experimental models, whichinduces the breast cancer in rats is very similar to the human breast cancer. Aseveryone knows, breast cancer is a kind of sex hormone-dependent tumor, andmost of the breast cancers induced by DMBA in rats are sex hormone-dependent, however, it is unclear that whether the sex hormone involved inthe carcinogenesis of DMBA. In this topic, we used DMBA to induced thebreast cancer in female SD rat, and resected the ovarian in a certain time afterthe carcinogenic factor was given. Observed the influence of ovariectomy onthe occurrence and development of rat breast cancer, to explore the role ofestrogen on carcinogenesis of DMBA, and hope to guide people learn aboutthe prevention and cure of human breast cancer, reduce the incidence of breastcancer.Methods:166healthy female virgin Sprague-Dawley rats,6weeks old,were radomedlydivided into3groups:①experimental group:22female virgin SD rats of6weeks, ovariectomy after one week when treatment by DMBA;②negativecontrol group:22female virgin SD rats of6weeks, treatment by DMBA;③blank control group:22female virgin SD rats of6weeks, no treatment.2Experiment begining after all rats to adapt to feed one week. Rats weregiven DMBA gastric lavage twice10mg/100g by weight in experimentalgroup and negative control group (interval1week), the ovarian were removedafter treatment drug one week in experimental group.3All of the rats were killed after24weeks when given the second DMBA. The morphological was observed in macroscopic observation. Breast tissueand tumor tissue were imbedded with paraffin stained with HE.4The data was organized and processed with SPSS13.0statistical software.Results:1Incidence: When the experiment was ended at the24th weeks, there were28rats had breast cancer in the56survival rats. In experimental group there were10rats had breast cancer in the16survival rats, the tumor incidence was62.5%. In negative control group,there were18survival rats and all of themhad tumors, the tumor incidence was100%. Blank control group had no tumor.It shows statistical difference among experimental group,negative controlgroup and blank control group (P=0.000). negative control group>experim-ental group>blank control group.2Latency: From the first time to give DMBA to touch the first tumor. Whenthe experiment was ended, the tumor latency in the experimental group was93.70±44.56days; the negative control group was60.22±29.86days; It showsstatistical difference between experimental group and negative control group(P=0.017). experimental group>negative control group.3Diameter of tumors(RECIST1.1standard): The diameter of tumors in theexperimental group was7.11±5.77cm; the negative control group diameter oftumors was12.67±7.33cm; It shows statistical difference betweenexperimental group and negative control group (P=0.049). negative controlgroup>experimental group.4The average number of malignant tumors: Calculating the number of themalignant tumors per rat. There were23tumors in the experimental group,20of them were malignant tumors, the average number of malignant tumors was1.25±1.39. There were108tumors in the negative control group,91of themwere malignant tumors, the average number of malignant tumors was5.06±2.80. It shows statistical difference between experimental group andnegative control group (P=0.000). negative control group>experimental group.5Types of tumors and the proportion of malignant tumors: There were23tumors in the experimental group, and there were20malignant tumors (It included13breast infiltrating carcinoma,1carcinomatous change,3carcinosarcoma,1interstitial canceration, and2pathological types was notclear), the proportion of malignant tumor was87%. There were108tumors inthe negative control group,91of them were malignant tumors(It included73breast infiltrating carcinoma,15carcinomatous change,2carcinosarcoma,1sarcoma), the proportion of malignant tumor was84.3%. It shows nostatistical difference between experimental group and negative controlgroup(P=0.994).Conclusion:1The animal model of breast cancer in rat can be established successfully bygiven SD rats twice10mg/100g DMBA intragastric administration.2The incidence of breast cancer induced by DMBA in female SD rats can bereduced by oophorectomy after intragastric administration.3The latency of breast cancer induced by DMBA in female SD rats can beprolonged by oophorectomy after intragastric administration.4The diameter of breast tumors induced by DMBA in female SD rats can benarrowed by oophorectomy after intragastric administration.5The number of breast malignant tumors induced by DMBA in female SDrats can be decreased by oophorectomy after intragastric administration.6The malignant tumor proportion of breast induced by DMBA in female SDrats has no relationship with oophorectomy.