| Bone is the common part in the breast cancer metastasis, bone metastasis is almostly found in the lately breast cancer patient . Bone metastasis is the main reason for influence of the quality and existence which is the complex progress of multifactor interaction. Bone metastasis of tumor cells begin to seprate primer tumor from primary, invade into blood circulation or lymph circulation, adere to endothelial tissue, migrate into bone and induce angiogenesis to maintain tumor growth. In 1994, Bellahcence first indicated that BSP was expressed in the breast cancer patients who were easy to bone metastasis. Bone sialoprotein (BSP) is one family number of SBLINGs that is a highly phosphorylation and glycosylation secreted protein in extracellular matrix. BSP has important role in tumor cell adhesion, proliferation, invasion, matrix degradation, immune functions (inflammation and complement evasion), angiogenesis and metastasis. It is a potential drug target of bone metastases. Therefore, studying BSP in breast cancerr metastasis mechanisim is great important of the diagnosis and therapy of breast cancer.For investigate the value of gene interference whose target is BSP in the invasive and metastasis regulation of breast cancer cells, previous experiments has constructed BSP-siRNA retrovirus recombinant plasmids that were packaged into retrovirus by 293 cells, infected bone-seeking human breast cancer cells (MDA-MB-231BO) with the retrovirus, and obtained successfully infected cells by puromycin screening, that is 231BO-BSP 27 and 231BO-scrambled cells. 231BO-BSP27 is stable suppression of BSP gene in breast cancer cell strain.Based on it, by observing vicious invaive phenotype of 231BO-BSP27 cells ,which include cell proliferation, cell migration,cell invasive ,and cells growth and metastasis in the nude mice, this study further investigated the effect of BSP-siRNA in the invasive and metastasis of breast cancer cells, so as to supply a new treatment target for breast cancer. The main research results are as follows:1. qPCR results showed that the quantity of mRNA of BSP was reduced 69% in 231BO-BSP27 cells .2. Western blotting results showed that the quantity of BSP was reduced 65% in 231BO-BSP27 cells .3. BSP immunostaining in MDA-MB-231BO and 231BO-scrambled were strongly positive, which mainly located in cytoplasm, while in 231BO-BSP27 was rhamnose positive.4. Cell growth curve and plate colony formation assay showed the growth rate and colony formation ability were both significantly lower in 231BO-BSP27 cells than those in the mock and negative control group.5. Cell cycle distribution showed the cell cycle of 231BO-BSP27 arrested at G0/G1 phase with a significant decrease of cells in S phase, that is , inhibited the proliferation in 231BO-BSP27 cells.6. Compare to mock and negative control group, the migration and invasion ability were both decreased in 231BO-BSP27 by cell scarification test and Transwell.7. The X-ray results showed partly of nude mice appeared bone metastasis of breast cancer cells; HE staining results showed the the incidence rate of bone metastasis indued by 231BO-BSP27 cells was apparently lower than MDA-MB-231BO and 231BO-scrambled cells; the results of bone immunostaining were the same to HE staining results, that is, BSP immunostaining was positive in the position where appeared tumor cells in the bone tissue. In a word, BSP gene silencing can decrease the incidence rate of bone metastasis.
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