Characterization And Transcriptional Regulation Of Cancer Stem Cell Marker CD133 In Hepatocellular Carcinoma

Cancer stem cells(CSCs)are cancer cells that possess the capacity to self-renew and differentiate into non-CSCs.CSCs have the properties of poor differentiation,high chemoresistance and high radioresistance and are considered key contributors to tumor recurrence and metastasis.Therefore,understanding the regulation mechanism of CSCs is important for tumor therapy.Ikaros plays the critical roles in the development of lymphocytes.However,the function of Ikaros in hepatocellular carcinoma is still unclear.We analyze Ikaros expression in 236 pairs of human primary HCC and paired nontumorous liver specimens by immunohistochemical staining(IHC).The IHC results demonstrate that Ikaros is expressed at low levels in HCC samples.We find that the expression of Ikaros inversely correlates with CD133 expression in HCC cells by western blot and realtime PCR.Ch IP array and DNA pull-down array show that Ikaros directly binds to the CD133 promoter and suppresses CD133 expression in HCC.Further,we show that Ikaros inhibits the tumorigenic and self-renewal capacity of CD133+ HCSCs and is able to increase the susceptibility of CSCs to drugs.Ikaros interacting with co-repressors as complexes regulates target genes.Ct BP and Ikaros cooperate to regulate CD133 expression in HCC cells by coimmunoprecipitation(Co-IP)and Ch IP.Meanwhile,we show that ETS1 directly binds to the Ikaros promoter and suppresses CD133 expression in HCC by Ch IP and DNA pull-down.The results that the specific Erk1/2 inhibitors PD98059 and U0126 areutilized to block the phosphorylation of ETS1 shows that MAPK pathway is able to regulate Ikaros and CD133 expression through the phosphorylation of ETS1.CXCL3 is the down-stream molecular of CD133 and regultes the Self-renewal,Tumorigenesis of CD133+ HCSCs.Silencing CD133 inhibits the expression of CXCL3.Silencing CXCL3 induces the differentiation of CD133+ HCSCs,decreases the susceptibility of CSCs to drugs and inhibits the tumorigenesis.Western blot show that CD133 expression is increase after CXCL3 treatment.These results suggest that Ikaros could be an attractive target in targeted CSCs therapy and that CXCL3 could be a novel potential serum biomarker of progression and outcome in HCC.