Abstract: The incidence of bladder cancer ranks first in urogenital neoplasms in China, but there are no specific and effective therapies. As the ideal target of the targeted therapy, bladder cancer stem cells (BCSCs) possess the characteristics of self-renewal, infinite proliferation and pluripotency, and are the source of bladder cancer tumorigenesis, progression, recurrence and metastasis. However, the self-renewal mechanisms of BCSCs remain unclear. Therefore, it is of great importance to clarify the mechanisms of stemness and screen of targeted inhibitors of BCSCs. Our previous studies uncovered that histone methyltransferase KMT1A was highly and specifically expressed in BCSCs. Moreover, depletion of KMT1A significantly abrogated self-renewal of BCSCs. In the proposed project, we plan to screen of a KMT1A inhibitor harboring the high-specificity and low side effects targeting to KMT1A in BCSCs with the tumor immunological and epigenetic methods. Furthermore, the optimal KMT1A inhibitor of BCSCs will be picked out with the evaluation of the inhibitory effects to BCSCs and bladder tumor, in vitro and in vivo. Finally, the inhibitory mechanisms of KMT1A inhibitor to BCSCs will be elucidated with the analysis of transcriptome and epigenomics of BCSCs. Collectively, the results of this project will illuminate the suppressive effects of KMT1A inhibitor targeting KMT1A in BCSCs and provide a theoretical and practical foundation to develop novel therapies targeted BCSCs.