The Study On Pathogenesis In MDS

Objective: To explore the relationship between the SF3B1 mutation and biological characteristics in patients with MDS-RS(myelodysplastic syndromes with ring sideroblasts).In addition,the underlying apoptosis mechanism in patients with refractory anemia with ring sideroblast(RARS)was investigated.Thirdly,miRNAs-regulated pathways were identified through the integration of microRNA-mRNA microarray and bioinformatics analysis in CD34+ cells of myelodysplastic syndromes.Methods and Results:(1)SF3B1 mutations were detected in 33 out of fifty-two MDS-RS patients(63%).The higher proportion of good or intermediate risk karyotypes were found in SF3B1 mutated patients.The vast majority of SF3B1 mutated patients were categorized into the lower IPSS risk groups.MDS-RS patients carrying SF3B1 mutations had a better overall survival(median 38 vs.18 months,P=0.001)compared to those without mutations.The prognostic significance of SF3B1 mutation was lost during multivariable analysis.(2)The ultrastructural alterations in SF3B1-mutated patients were the abundant electron-dense deposits in the erythroblastic mitochondria.MDS-RS patients with mutations presented both improper iron uptake and distribution(lower serum hepcidin-25 concentration,P = 0.028)and enhanced erythropoietic activity(higher soluble transferrin receptor level,P = 0.132;higher growth differentiation factor 15 concentration,P < 0.001).(3)The quantity growth of cells from RARS patients was significantly less than that of the normal control in vitro erythropoiesis culture(720 vs.30000).Annexin V binding cells was increasing in RARS patients compared with control group during the course of in vitro liquid culture.In RARS patients,mitochondrial membrane potential significantly decreased,as well as the number of caspase 9 positive cells increased on 13 d.There was no significant change in the number of Caspase 8 positive cells in the culture process.Colony-formation assay showed that the number of burst-forming unit–erythroid(BFU-E)in RARS patients was significantly less than control group(34 vs 185).(4)25 dysregulated miRNAs and 394 targeted mRNAs were screened.Through a combination of Pathway and miRNA-Gene or GO-Network analysis,several miRNAs-regulated pathways such as miR-195/DLL1/Notch signaling pathway were identified.Luciferase assay showed that DLL1 was a direct target of miR-195.Overexpression of miR-195 leads to increased cell apoptosis and cell growth was reduced through inhibition of Notch signaling pathway.Conclusions:(1)MDS-RS patients carrying SF3B1 mutations harbored a more severe iron overload and corresponding over-erythropoiesis.(2)The prognostic significance of the SF3B1 mutation was primarily accounted for by IPSS risk categorization.(3)The number of erythroid progenitor cell in RARS patients was obvious less than control group.(4)In RARS patients,there was early-stage apoptosis in the erythropoiesis,and the stimulation of mitochondrial pathway in the late-stage erythropoiesis resulted in the progress of apoptosis.(5)Inhibition of Notch signaling pathway by miR-195-DLL1 axis contributes to the excess apoptosis in low-grade MDS.