Role Of Cytochrome P450s In Bone Biology And Breast Cancer

Steroid hormones and seco-steroids play a critical role in bone homeostasis,and their biosynthesis in bone cells(as in other cells)depends on the activity of cytochrome P450 enzymes(CYPs or P450s).However,only limited information is available on the expression of different CYPs in human bone cells and their role in bone biology.In this study we analyzed the expression levels of eight different CYPs in four different human osteoblast models:In osteoblasts cultured from human bone pieces,in osteoblasts differentiated from human periosteum mesenchymal stem cells(HPDC),in primary human osteoblasts(HOB),and in the human osteoblast cell line MG63,respectively.All eight CYPs we studied were expressed in all four human osteoblast models,albeit at significantly different levels spanning five orders of magnitude.These results confirm previous reports about the expression of CYP11A1,CYP17A1,CYP24A1,and CYP27B1,respectively,in human osteoblasts,while demonstrating expression of CYP2E1,CYP26A1,CYP39A1,and CYP51A1,respectively,for the first time.In addition,it has been reported that inflammation has adverse effects on bone forming cells(osteoblasts)and thus causes bone loss and osteoporosis.Interestingly,inflammation can also affect CYP expression.However,the role of CYPs in bone biology and the effect of inflammation on CYP expression in osteoblasts are poorly understood.Based on the findings on CYPs expression in human osteoblasts,we continued the investigation on the expression pattern of9 CYPs(CYP2E1,CYP11A1,CYP17A1,CYP19A1,CYP24A1,CYP26A1,CYP27B1,CYP39A1 and CYP51A1)in different differentiation stages of primary human osteoblasts(HOB)and the human osteoblast cell line MG63 and,moreover,determined the effect of tumor necrosis factor-alpha(TNF-α),an inflammatory cytokine,on CYP expression.CYP expression in these two kinds of cells showed different expression patterns.However,not all CYPs under study were affected by inflammation.In MG63,only CYP17A1 was affected at both day 3 and day7,while in primary human osteoblasts,CYP27B1 and CYP39A1 are affected at both day3and day7.Breast cancer is now the most frequently diagnosed cancer and leading cause of cancer death in women worldwide.Metastatic disease,or the spread of tumor cells throughout the body,is responsible for the vast majority of cancer patient deaths.Bone is one of the most common metastatic sites for breast cancer.Bone metastasis has become a huge threatening for people’s life.It has been reported that estrogens context play an important role in the development of breast cancer.CYPs are essential in the biosynthesis and metabolism of estrogens.However,there is limited information about the role of CYPs in breast cancer bone metastases.In recent years,the role of microenvironment in cancer progression received increasing attention and several studies have demonstrated that the reciprocal crosstalk between cancer cells and host cells governs cancer cell behavior,also in the of metastatic cascade.Thus,in this project,in order to elucidate whether CYPs are involved in breast cancer bone metastasis and make a further investigation on the key factors involved with modulation of CYPs in the microenvironment,we planned to determine CYPs expression level in human osteoblasts and breast cancer cells upon the treatment of breast cancer cells and human primary osteoblast conditioned-medium respectively,and detect the cytokines in the conditioned medium after the reciprocal crosstalk between cancer cells and osteoblast cells.