The Study And Identification Of SOX2 As A Marker For Bladder Cancer Stem Cell

Bladder Cancer(BCa)is one of the most common malignant tumors in the urinary system and seriously endangers people's health.According to the report of the incidence of cancer shows that in recent years,the incidence of bladder cancer in most cities of raised rapidly.The biological behavior of bladder cancer is complicated,previous study shows that majority of bladder cancer is urothelial carcinoma,which has a high recurrence rate.Although many progresses have been made in bladder cancer management,the mechanism of BCa initiation,progression and metastasis is still not fully understood.It has been reported that functionally distinct cancer stem cells(CSCs)exist in human bladder cancer(BCa).Here,we found that Sox2,which is a well-characterized transcription factor for stem cell markers,is up-regulated in both mouse and human BCa.First,we established a bladder cancer model by induced the Sox2 Cre ER: R26 tdtomato mice with N-butyl-N-4-hydroxybutyl Nitrosamine(BBN)and detected the expression of SOX2 by immunohistochemistry and fluorescence assessment.We found SOX2 expression is higher in bladder hyperplasia and invasive bladder cancer,but absent in normal bladder tissue.In addition,we found that SOX2-positive cells are neither proliferating nor differentiated in BCa tissues,but may have stem cell properties.To demonstrate this,we use lineage tracing and limited dilution assay in vivo and sphere formation assay in vitro to prove that SOX2-positive(SOX2+)cells have a more pronounced ability of self-renew,form secondary tumors and spheres.Moreover,Sox2+ cells are found more aggressive than SOX2-cells.These results indicate that SOX2-positive cells are bladder cancer stem cells.We also investigate the relationship among SOX2 and other previously reported markers of bladder cancer stem cells(BCSCs),including CD44v6 and keratin 14(KRT14)by flow cytometry and immunofluorescence staining.SOX2-positive cells also expressed KRT14 and CD44v6 which suggest that they may be a subset of KRT14 + and / or CD44V6 + cells and are more specific than these two markers.In addition,we also explored briefly the mechanism by which SOX2 regulates the stemness of BCSCs and identified some possible target genes and signaling pathways regulated by SOX2.Finally,we eliminated SOX2+ cells by tamoxifen administration in Sox2 Cre ER: Rosa-DTA mouse and found that ablation of Sox2-expressing cells in primary invasive BCa resulted in an dramatic decrease of tumor formation.Our data showed that Sox2 is a marker of bladder CSCs and suggests that it is a potential clinical target for BCa therapy.