Role For Sp1, C-Myc And Micro-203 In Drug Resistance And Stemness Of Leukemia Stem Cells

Objective: Acute myeloid leukemia(AML) is initiated and maintained by a subset of selfrenewing leukemia stem cells(LSCs), which contribute to the progression, recurrence and therapeutic resistance of leukemia. However, the mechanisms underlying the maintenance of LSCs drug resistance have not been fully defined. In this study, we attempted to elucidate the mechanisms of LSCs drug resistance.Methods: We performed reverse phase protein arrays to analyze the expression of antiapoptotic proteins in the LSC-enriched leukemia cell line KG-1a. Immuno-blotting, cell viability and clinical AML samples were evaluated to verify the micro-assay results. The characteristics and transcriptional regulation of survivin were analyzed with the relative luciferase reporter assay, mutant constructs, chromatin immuno-precipitation(Ch IP), quantitative real-time reverse transcription polymerase chain reaction(RT-q PCR), and western blotting. The levels of Sp1, c-Myc, phospho-extracellular signal-regulated kinase(p-ERK), phospho-mitogen and stress-activated protein kinase(p-MSK) were investigated in paired CD34+ and CD34- AML patient samples. The relative luciferase reporter assay, QRT-PCR and Western blot were used to detect the effect of mi R-203 on drug resistance and self-renewal capacity in leukemia stem cells.Results: Survivin was highly over-expressed in CD34 + CD38- KG-1a cells and paired CD34+ AML patients compared with their differentiated counterparts. Functionally, survivin contributes to the drug resistance of LSCs, and Sp1 and c-Myc concurrently regulate levels of survivin transcription. Clinically, Sp1 and c-Myc were significantly upregulated and positively correlated with survivin in CD34+ AML patients. Moreover, Sp1 and c-Myc were further activated by the ERK/MSK mitogen-activated protein kinase(MAPK) signaling pathway, modulating survivin levels. Mi R-203 targeting Survivin and Bmi-1 3 ’-UTR region to regulate the drug resistance and self-renew ability of leukemia stem cells.Conclusion: Our findings demonstrated that ERK/MSK/Sp1/c-Myc axis functioned as a critical regulator of surviving expression in LSCs, and mi R-203 involved the critical roles in leukemia stem cells’ phenotype, which offering a potential new therapeutic strategy for LSCs therapy.