Role Of Tumor-derived PTHrP In Breast Cancer Growth And Progression And Tumor-mediated Osteoblast Inhibition And Osteoclast Activation And Bone Destruction

Breast cancer is a common malignancy among women,causing high morbidity and mortality;almost 500,000 people die of breast cancer every year all over the world.At the initial stage,it is simply manifested as excessive proliferation and abnormal apoptosis reduction;but at the advance stage,metastasis is the main cause for mortality,bone is the most common target.PTHrP is a kind of protein that is found in hypercalcemia-related malignancies,it is highly expressed in many breast cancer cells.PTHrP can increase RANKL and reduce OPG expression in osteoblasts and stromal cells and activate osteoclast.This study aimed to determine the role of tumor-derived PTHrP in breast cancer growth and progression and the tumor-mediated osteoblast inhibition and osteoclast activation and bone destruction.This study used shRNA strategy and knocked down PTHrP expression in human MDA-MB-231 cells.The effects of PTHrP knock down on tumor growth and tumor-bone interactions were examined.We choosed the most efficient cells 995,996 and negative control to make three kinds of condition medium;We used these three conditon medium to check the relative expression of osteoblast marker genes OCN/OSX/Runx2/ALP/BSP and Osteoclast maker genes CatK/RANK/Trap/MMP-9,ALP activity,AR-S staining and Trap staining in order to find out the difference among them.Then we used the intratibia injection of 995,996,NC three kinds of cells in Balb/C nude mouse.After 28 days,we used X-ray,IHC and so on to check the difference related to proliferation and differentiation of osteoblast and osteoclast.In vitro,we used the way of cell-cycle analysis,relative expression of apoptosis related protein Caspase8 and bcl-2,relative expression of autophagy marker protein LC3A/B and Beclinl,transmission electron microscope,cell growing curve and so on in order to check the difference between the three kinds;in vivo,we used the Balb/C nude mouse subcutaneous tumor of 995,996 and NC cells,through the comparation of growing curve,size,and weight,we examined the difference between the three kinds.From this study,we got the conclusion that in both vivo and vitro,the breast cancer derived-PTHrP can inhibit the proliferation and differentiation of osteoblast and activate the proliferation and differentiation of osteoclast directly through increasing IL-6;in both vivo and vitro,the breast cancer derived-PTHrP can increase the proliferation of tumor cell itself and decrease the apoptosis and authophagy in order to adapt itself to the tumor metastasis microenvironment.