Effects Of Cytokine CCL20 On The Proliferation,Migration And Osteolysis In Giant Cell Tumor Of Bone

Giant cell tumor of bone(GCTB)is one of the most common primary bone tumors,averaging 5-6% of all clinical bone tumors.Usually occurs in the metaphysis,thoracic vertebra and sacrum.The common age of onset is between 20-40 years old,and women are more susceptible.Through the giant cell tumor of bone is treated as a borderline tumor,it still has a strong tendency of local infiltration and lung metastasis.Causing local osteolytic destruction as its main feature,patients with GCTB show pathological fracture with persistent pain as the first symptom.Additionally causing neural dysfunction and other adverse consequences,GCTB leads to serious damage in life quality of patients.This tumor is neither sensitive to radiotherapy nor chemotherapy,so the recommended treatment is surgical resection combined with targeted drug therapy.However,the giant cell tumor of bone has a high recurrence tendency with the recurrence rate high as 41.7%.GCTB originated from the bone marrow mesenchymal cells.The main pathological feature of the tumor is the wide existence of multinucleated giant cells(MNGC),which has the shape and biological behavior close to osteoclasts.It is considered that there are two other kinds of cell types lies in the GCTB: osteoblast derived giant cell tumor stromal cells(GCTSC)and mononuclear histiocytic cells(MNHC).The GCTSC with its ability to proliferate and stimulate the MNHC to form MNGC in giant cell tumor and then bone dissolution plays a key role in bone destruction process.It is considered to be the actual tumor components in GCTB.Therefore,the study on the differentiation and proliferation of GCTSC and the ability to induce the differentiation and migration of MNGC can provide a new horizon for the prevention,diagnosis and treatment of GCTB.The chemokine family includes four subfamilies,named C,CC,CXC and CX3 C.Chemokine CCL20,also known as macrophage inflammatory protein-3 alpha(MIP3 alpha),belongs to CC subfamily and its receptor is CCR.Its coding DNA is located on chromosome two.CCL20 mRNA translated into a 96 amino acid precursor protein.After the processing it forms mature CCL20 with 70 amino acids.CCL20 is expressed mainly in the mononuclear cells,T lymphocytes,dendritic cells and endothelial cells of the liver,lung and lymphoid tissue.It can be induced by a variety of cytokines such as tumor necrosis factor alpha(TNF alpha),interleukin 1(IL-1)and interferon gamma(IFNgamma).CCL20 is known to be participating in the physiological and pathological processes such as inflammatory cell chemotaxis,tumor cell proliferation and metastasis.At present,it is confirmed that CCL20 is closely related to the invasion and metastasis of breast cancer,liver cancer,colon cancer and pancreatic cancer.However,there is no report on the relationship between CCL20 and the occurrence and development of giant cell tumor of bone.In this study,we first compared the expression of different chemokines in GCTSC of GCTB and normal cancellous bone cells by qRT-PCR and microarray analysis.ELISA was used to compare the expression levels of chemokine CCL20 in normal and GCTB patients' serum.Also the difference of the expression level of GCTB of different size is measured.Secondly,we evaluated the CCL20 autocrine promoting effect on the proliferation of GCTSC through the conditional cell culture test.the effect of chemokine CCL20 on the migration ability of GCTSC was verified by cell migration and invasion assay(Transwell).And the effect of CCL20 on the formation of osteoclasts was verified by conditional cell culture test and bone slice analysis.And finally,we explored the possible signal transduction pathway of CCL20 in giant cell tumor of bone by detecting the expression of osteoclast associated Maker gene under the stimulation of CCL20..For the first time we confirmed the increased expression of chemokine CCL20 in GCTB,as well as its abilities of promoting GCTSC proliferation,migration and formation of osteoclasts,and found a possible molecular mechanism.The results of this series of experiments are as follows: 1.Chemokine CCL20 expression is significantly increased in GCTB;2.Chemokine CCL20 can promote GCTSC differentiation,proliferation,migration and formation of osteoclasts;3.Chemokine CCL20 may exert biological effects on giant cell tumor of bone by affecting AKT phosphorylation.