Pathologic Characterization Of Spontaneous Breast Tumors In SPF Rats And Establishment And Characterization Of A Cell Line ZHL2006

Rat is one of the most popular laboratory animal in medical research. Spontaneous tumors is an important biological characteristics in rats. The study tries to characterize the epidemiologic and pathologic features of spontaneous breast tumor in SPF rats. The epidemiology and pathology of the spontaneous breast tumor may be valuable for the animal-model-establishment and pathogenesis of tumor. In this study we investigated the tumor epidemiology, and observed the clinical pathology in SPF rats. The cases were to classify according to qualitation by macroexamination and microscopic examination. The incidence of spontaneous breast tumor in Sprague-Dawley rats is approximately 10.5%, in which the incidence of benign tumor is approximately 8.5 %, and that of malignant tumor 2.0%; the incidence of Wistar rat is 2.0%, in which incidence of benign tumor is 1.5%, and the malignant tumor 0.5%. The incidence of benign tumor is higher than that of malignant tumor both in Sprague-Dawley rats and wistar rats, in which the adenofibroma and adenoma are the most. This research enriched the Closed Colony SPF rats biology background data, and may provide one method for establishing animal tumor model for human corresponding disease.Tumor development is a complex process with multi-gene participation, and is correlated not only with abnormal activation of oncogenes and deactivation of tumor-suppressing gene but also with apoptosis. Wild-type p53 gene has negative regulation to multiplication and differentiation of cells, mutant p53 gene losts normal function and gains oncogene characteristics. Bcl-2 is control gene of apoptosis and its abnormality may interruption apoptosis that leads to tumorigenesis. SABC method of immunohistochemistry was used to detect proteinum expression of p53, Bcl-2 in rats breast tumor specimen. Results showed that the expression rate of p53 in rats benign and malignant tumor were 46.1% ( 12/26 ) and 85.7% ( 6/7 ) respectively, the positive rate of p53 proteinum became higher with the increase of tumor cancerization degree. The overexpression of p53 proteinum hinted the tumor cancerization degree which is similar sense human in malignant tumor. The expression rate of Bcl-2 in benign and malignant tumor were 26.9% ( 7/26 ) and 57.1% ( 4/7 ) respectively. The expression rate of Bcl-2 increased gradually with the development of cancerization. The mutation rate was 81.8% in 11 Bcl-2 positive expression tumor cases, and was 40.9% in 22 Bcl-2 negative expression tumor cases. Both p53 and Bcl-2 proteinums high positive expression may suggest the two proteins had synergistic effect in the tumor genesis and development.A strain of breast tumor cell line ZHL2006 was established and biologically identified. The ZHL2006 cells grew fast in vitro and the population doubling time was 43.6h. Electronmicroscopical observation showed that there were microvilli on the surface of the cells, nucleus irregularity, karyoplasmic ratio increased, nucleolus distinctness, et al.. Chromosome number and structure were abnormal. Immunohistochemistry showed that PCK were expressed. The ZHL2006 cell line could form onto clone in soft agar and had oncogenicity in athymic mice. After long-term vitro cultivation the cell line had become immortalized cells with conspicuous malignant cell phenotype.