The Mechanism Of HDAC3 Regulating FOXO1 Downstream Target Gene Expression In Prostate Tumor Cells

Prostate cancer(PCa)is the most common malignancy affecting men's health in the western world and it's the fifth lethal disease.According to statistics,in the United States,there are more than 230,000 men are diagnosed with prostate cancer in 2013,and the mortality rate is as high as 12%.Although the morbidity and mortality of prostate cancer in China are much lower than those in Europe,the United States,and other developed countries,the incidence of prostate cancer in our country has shown a significant trend of growth with the aging of population and the increasing popularity of PSA screening.To date,the incidence of prostate cancer in China ranks third among male urinary and reproductive system malignancies.Prostate cancer has become a primary threat to the health of the country's aging men.FOXO1 is the first member of FOXO subfamily to be found,which is also the most representative for research.It is involved in a variety of intracellular signal transduction pathways and plays an important role in many physiological and pathological processes.As a transcription factor,FOXO1 plays these biological functions by regulating the expression of target genes.For example,FOXO1 up-regulates the expression of FasL,Bim,Bcl-6 and TRAIL to induce apoptosis in a variety of hematopoietic cells,nerve cells,tumor cells.Activation of FOXO1 results in anoikis of prostate cancer cells.The inhibitory effect of SIRT1 on VAF apoptosis is partly mediated by the deacetylation of FOXO1.Histone deacetylases(HDACs)is one of the key enzymes in maintaining the balance of histone acetylation levels of nucleosomes.HDACs family with 18 members,by according to their structure and.function,are divided into four categories.Studies have shown that HDACs may deacetylate different nuclear transcription factors and proteins,and result in inhibiting the expression of a variety of tumor suppressors and causing excessive cell proliferation and tumorigenesis.Significance of this study is to investigate the effect of HDAC3 on maintaining FOXO1 acetylation levels and its target gene expression,understand the role of HDAC3 and FOXO1 in the process of tumorigenesis.To carry the above points,experiments are designed as following sections.First,after treating with different concentrations of histone deacetylase inhibitor TSA,we found that the expression of PSA was declined in CWR22RV1 cells,while the expression of Bim,target gene of FOXO1,was increased.Second,after transient transfection of eukaryotic expression vector of HDAC1,HDAC2,and HDAC3 in vitro,RT-PCR and Western blot were performed to explore the expression of Bim and the regulation of FOXO1 acetylation in prostate cancer cells.The result showed that HDAC3 altered the acetylation levels of FOXO1 and the expression of Bim,and HDAC3 interacted with FOXO1.Finally,deletion mutant plasmids of HDAC3,pcDNA3.1(+)-HDAC3-180 and pcDNA3.1(+)-HDAC3-122,had been constructed.By transient transfecting these mutant into CWR22RV1 cells,we found that HDAC3 would not cause the changes of FOXOl acetylation and Bim expression levels when losing the deacetylation activity of HDAC3.Taken together,this research demonstrated that,in CWR22RV1 cells,HDAC3 interacted with FOXO1 protein and regulated the acetylation level of FOXOl through its deacetylase activity;and further affected the expression of FOXO1 target genes.