The Molecular Regulatory Mechanism Of Proto-oncogene CT45A1 To Trigger Aberrantly Overexpression Of Metastatic Gene SULF2 In Breast Cancer Cells

Breast cancer is the leading cancer thataaffects women globalfy.Although the earfy stage of breast cancer patients can be effectively treated by surgery and radiotherapy combined with chemotherapy,the 5-year survival rates of breast cancer may reach 77%,unfortunately,many breast cancer patients are on late stage with metastasis when they are diagnosed,and surgery cannot do anything about it at this moment.Furthernore,metastatic breast cancer often show features of resistance to radiotherapy and chemotherapy,there is cuirently no curable treatments as to metastatic breast cancer.At present,there are 70,000 breast cancer patients died every year;thus,breast cancer is one of the most lethal cancers in women all over the world.Tumor metastasis is the major cause of death in the breast cancer patients,and studies have shown that 90%of breast cancer death was caused by tumor metastasis.The mechanism of breast cancer metastasis is enigmatic.The efficacy of current anti-breast cancer metastatic drugs are very poor.Hence,elucidation of the mechanism of breast cancer metastasis has become a urgently prominent scientific question to be solved in cancer research of the world,and it is also in the front of science in the early diagnosis and prevention of breast cancer.The mechanism of breast cancer metastasis is very complex,involving multiple genes and signaling pathways.The key genes responsible for the breast cancer metastasis is still unclear.CT45A1,one of the femily members of cancer-testis Antigen CT45,is highly expressed during embryonic development stage,after the birth,it only strictly expressed in male testicle spermatogonia cells,not expressed in any other organs and cells.Our lab recently reported that CT45A1 act as a new proto-oncogene and induces overexpression of multiple carcinogenic genes,including tumor metastatic gene sulfatase ?(SULF2),to promote breast cancer metastasis.(Shang B,et al.Cell Death Dis 2014);however,the mechanism of CT45A1-induced SULF2 overexpression has not been reported in the literatures yet.In light of that CT45A1 is a nuclear protein and can bind to DNA,we raise a hypothesis that CT45A1 binds to specific SULF2 promoter region to enhance the promoter activity of SULF2 gene,and that it may intereact with transcription factor to trigger the overexpression of SULF2.In order to prove the hypothesis,we used series of experimental procedure,including Inciferase gene report system,nucleic acid-protein binding assay,immunoprecipitation,and several specific inhibitors,and found that:(1)CT45A1 larkedly elevated SULF2 protein levels in breast cancer cells.(2)Luciferase gene reporter system showed that CT45A1 significanly activated SULF2 gene promoter activity.(3)DNA-protein binding assay showed that CT45A1 bound to the SULF2 promoter region-107bp to-145bp,which contains the core binding sequence of transcription factor Sp1(ATGCCCCCTGG).(4)Inmunoprecipipation proved that CT45A1 interacted with Sp1,convincingly,Sp1 specific inhibitors blocked the overexpression of SULF2.These results indicate that CT45A1 acts as an activator of transcriptor factor Sp1 to promote SULF2 gene transcription.Collectively,we found that CT45A1 promoted SULF2 aberrant overexpression in breast cancer through binding to the promoter of SULF2 gene,interacting with tumor master transcriptor factor Sp1,and revealing the regulatory mechanism of CT45A1-activated overexpression of tumor-metastatic gene SULF2 in breast cancer cells.Thus,this study has conderable significance in the elucidate the mechanisms of breast cancer metastasis,not only get new insigji into breast cancer metestasis,but also provide novel sategy and new target for new drug discovery for anti-breast cancer metastasis.