| The breast cancer is a kind of malignant tumor which endangers the life and health of the female. The occurring incidence ranks the second of female tumor in our country. It is well accepted that breast cancer arises in a multistep fashion in which exposures to environmental carcinogens is a major etiological factor. But by now no genuine pathogeny of breast cancer have been found, mainly because of lacking the suitable model system in research of breast cancer. It is reported that not every cell within breast cancer is capable of regenerating the tumor, while only a limited number of cells are capable of initiating the tumor ,which was called tumor –initiating cell(T-IC) .Moreover T-IC surface phenotype of the initiating the tumor is similar to that of the normal human mammary stem cell. The research on the mammary stem cells has just started .The mammary stem cell were studied at the beginning of the 80th of this century.Based on the well knowledge of the morphologies characteristic of every kind of epithelium in mammary gland with the optical microscope and the electronic microscope .Mammary epithelium have been cultured from human and rodents by plating fragment of epithelium ,called "organoids"in several laboratories such as Ben,Nandi,Hackett,Furmanski,etc of the united states ,England and Europe .Based on the development that the epithelium were single cell-cloning from organoids ,and the cloned cells were immortalized and induced differentiation .in March 2002,Denmark Peterson first declared that he had separated and cultured the mammary stem cells from tissues of reduction mammoplasty by the immunomagnetic beads sorting and proved that the stem cell were able to divide by themselves and convert to the other cell types in the mammary glands and gived rise to terminal duct lobular units structure. The epithelium compartment of the human breast comprise two distinct lineages :the luminal epithelial and the myoepithelial lineage.we have shown previously that a subset of the luminal epithelial cells could convert to myoepithelial cells in culture .Using cell surface markers :MUC/ESA/K19/ASMA and immunomagnetic sorting ,we isolated two luminal epithelial cell population fromprimary culture of reduction mammoplasties. Surface markers of luminal epithelial are MUC/ESA/K19.The use of immunomagnetic sorting technology with cell surface-specific markers will allow the specification of phenotype to be studied on a single-cell level in real time. Furthermore, when used in conjunction with other antigens, this strategy might permit the enrichment of any breast phenotypes or cell types with the phenotype-specific markers. Biomagnetic sorting is direct and rapid, which is an important factor in conserving the viability of human breast cells. . At present we separated the human mammary epithelial cell with some stem cell properties from the tissue surrounding the primary breast tumor . Two morphological types of clone were seen by phase-contract microscope.Most of luminal epithelium are spread out in an attenuated fashion and the individual cell boundaries are difficult to discern .The cells have round or cube square.The clones have a continuous and sharply demarcated boundary.some cells at the periphery are elongated and circumjacent Orientated with the impression of being under the tension .The myoepithelium are composed of more tightly packed cells distinguished by their brightly refractile boundaries,some form regular pavement-like arrays. The types of the cells are distinguished byimmunohistochemistic technique as the major luminal epithelial cells express epithelial specific antigen(ESA+) and Sialomucin(MUC+) whereas the minor population express epithelial specific antigen but no sialomucin (MUC-/ESA+);Myoepithelial ones express the smooth muscle action (ASMA).The (MUC-/ESA+) epithelial cell line further differed from the (MUC+/ESA+) epithelial cell line by the expression of keratin K19. (MUC-/ESA+/k19+) epithelial cell could convert to myoepithelial cell,which are tested by immunohistochemistic technique(MUC-/ESA+/k19+).In order to obtain the immortalized and passaged for longtime epithelial cells which were transfected with a plasmid carrying an origin-defective Simian virus 40 genome gene fragment ,by feeding the (MUC-/ESA+/k19+)epithelial cell on the system of three dimension made up of collagen gel and Matrigel.,We could discover that the cell clones form terminal duct units. It is well accepted that high x-ray radiation and 17β-estradiol are two major etiological factors of breast cancer. It was reported that breast cancer-initating cell was mammary stem cell .The aim of the this work is to establish an experimental breast cancer model by high X-ray radiation in the presence of 17β-estradiol(E). (MUC-/ESA+/k19+)epithelial cell irradiated showed gradual phenotypic changes including altered morphology ,increase in cellproliferation relative to the control ,invasive capability before becoming tumorigenic in nude mice. (MUC-/ESA+/k19+) epithelial cell were cultured in the presence of E in vitro ,increased BRCA1,BRCA2 expression were detected by RT-PCR.Among various transformed markers of human breast cells,BRCA1 and BRCA2 are tumor suppressor gene that hasve been implicated in hereditary forms of breast cancer .It is transcriptionally regulated in a proliferation-dependent manner.Mutation in these breast cancer susceptibility genes are believed to account for 50% of families with high incidence of breast cancer and at least 80% of families with increased incidence of early onset of breast cancer .likewise ,carriers of mutation in the breast cancer susceptibility gene BRCA2 have a highly how mutated genotypes predispose to cancer.A role of BRCA2 protein in repair of double-strand breaks through its regulation of the association of BRCA1 Protein.in addition deregulation of mutated BRCA2 protein may lead to deficient DNA repair and genomic instability . Progressively growing tumor will produce when(MUC-/ESA+/k19+) epithelial cells irradiated were inoculated into nude mice,which is testified by pathologic methods . The results of this part of experiment showed that luminal epithelial cell(MUC-/ESA+/k19+) which were...
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