Chengming Fei

Down-regulation of Dicer1 promotes cellular senescence and decreases the differentiation and stem cell-supporting capacities of mesenchymal stromal cells in patients with myelodysplastic syndrome.

Although it has been reported that mesenchymal stromal cells are unable to provide sufficient hematopoietic support in myelodysplastic syndrome, the underlying mechanisms remain elusive. In this study, we found that mesenchymal stromal cells from patients with myelodysplastic syndrome displayed a significant increase in senescence, as evidenced by their decreased proliferative capacity, flattened morphology and increased expression of SA-β-gal and p21. Senescent mesenchymal stromal cells from patients had decreased differentiation potential and decreased stem cell support capacity. Gene knockdown of Dicer1, which was down-regulated in mesenchymal stromal cells from patients, induced senescence. The differentiation and stem cell-supporting capacities were significantly inhibited by Dicer1 knockdown. Overexpression of Dicer1 in mesenchymal stromal cells from patients reversed cellular senescence and enhanced stem cell properties. Furthermore, we identified reduced expression in the microRNA-17 family (miR-17-5p, miR-20a/b, miR-106a/b and miR-93) as a potential factor responsible for increased p21 expression, a key senescence mediator, in Dicer1 knockdown cells. Moreover, we found that miR-93 and miR-20a expression levels were significantly reduced in mesenchymal stromal cells from patients and miR-93/miR-20a gain of function resulted in a decrease of cellular senescence. Collectively, the results of our study show that mesenchymal stromal cells from patients with myelodysplastic syndrome are prone to senescence and that Dicer1 down-regulation promotes cellular senescence and decreases the differentiation and stem cell-supporting capacities of mesenchymal stromal cells. Dicer1 down-regulation seems to contribute to the insufficient hematopoietic support capacities of mesenchymal stromal cells from patients with myelodysplastic syndrome.

Senescence of bone marrow mesenchymal stromal cells is accompanied by activation of p53/p21 pathway in myelodysplastic syndromes

The contribution of bone marrow mesenchymal stromal cells (BMMSCs) to the pathogenesis of myelodysplastic syndrome (MDS) has created controversies. In this study, we confirmed that BMMSCs from MDS patients showed prominent features of senescence, which were characterized by increased cell size, decreased proliferation and colony‐forming potential, alteration of cytoskeleton, and increased senescence‐associated β‐galactosidase (SA‐β‐Gal) activity. Interestingly, the apoptosis assay results showed that the percentage of apoptosis cells was very low and the difference was not significant between MDS patients and normal controls. Moreover, the osteogenic differentiation potential of BMMSCs from lower risk but not higher risk MDS was impaired, indicated by cytochemical stainings and reduced expressions of RUNX2. In addition, BMMSCs from MDS patients had impaired hematopoietic supporting function. Furthermore, the expression of p53 and p21 which played an important role in regulating the senescence progress of BMMSCs was significantly increased, whereas levels of p16 and pRb expression were not changed in the BMMSCs from MDS patients. Taken together, our comprehensive analysis shows that BMMSCs from MDS patients exhibited senescent behavior and activation of p53/p21 pathway probably played an important role in the senescence process.

Impaired osteogenic differentiation of mesenchymal stem cells derived from bone marrow of patients with lower-risk myelodysplastic syndromes

The pathogenesis of myelodysplastic syndromes (MDS) has not been completely understood, and insufficiency of the hematopoietic microenvironment can be an important factor. Mesenchymal stem cells (MSCs) and osteoblasts are key components of the hematopoietic microenvironment. Here, we measured the expression of multiple osteogenic genes in 58 MSCs from MDS patients with different disease stages and subtypes by real-time PCR and compared the osteogenic differentiation of MSCs from 20 MDS patients with those of MSCs from eight normal controls quantitatively and dynamically. The mRNA level of Osterix and RUNX2, two key factors involved in the early differentiation process toward osteoblasts, was significantly reduced in undifferentiated MSCs from lower-risk MDS. After osteogenic induction, lower-risk MDS showed lower alkaline phosphatase activity, less intense alizarin red S staining, and lower gene expression of osteogenic differentiation markers; however, higher-risk MDS was normal. Finally, in bone marrow biopsy, the number of osteoblasts was significantly decreased in lower-risk MDS. These results indicate that MSCs from lower-risk MDS have impaired osteogenic differentiation functions, suggesting their insufficient stromal support in MDS.

Whole-exome and targeted sequencing identify ROBO1 and ROBO2 mutations as progression-related drivers in myelodysplastic syndromes

The progressive mechanism underlying myelodysplastic syndrome remains unknown. Here we identify ROBO1 and ROBO2 as novel progression-related somatic mutations using whole-exome and targeted sequencing in 6 of 16 (37.5%) paired MDS patients with disease progression. Further deep sequencing detects 20 (10.4%) patients with ROBO mutations in a cohort of 193 MDS patients. In addition, copy number loss and loss of heterogeneity (LOH) of ROBO1 and ROBO2 are frequently observed in patients with progression or carrying ROBO mutations. In in vitro experiments, overexpression of ROBO1 or ROBO2 produces anti-proliferative and pro-apoptotic effects in leukaemia cells. However, this effect was lost in ROBO mutants and ROBO-SLIT2 signalling is impaired. Multivariate analysis shows that ROBO mutations are independent factors for predicting poor survival. These findings demonstrate a novel contribution of ROBO mutations to the pathogenesis of MDS and highlight a key role for ROBO-SLIT2 signalling in MDS disease progression.

High expression of APAF-1 elevates erythroid apoptosis in iron overload myelodysplastic syndrome

Apoptotic protease-activating factor 1 (APAF-1) is a central component of the intrinsic pathway of apoptosis. Our study aims at searching the role of APAF-1 in iron overload myelodysplastic syndrome (MDS). Erythroid apoptosis rate, mRNA expression levels of APAF-1, and caspase-9 activity were determined by flow cytometry, quantitative real-time PCR, and colorimetric assay in MDS patients, respectively. In addition, K562 and MDS-L cell lines were incubated with different concentrations of ferric ammonium citrate (FAC) or ferric ammonium citrate + desferrioxamine (FAC + DFO) in vitro to observe the alteration in erythrocyte apoptosis rate, APAF-1 mRNA, and protein expression levels. Moreover, as control, erythroid apoptosis rate and APAF-1 mRNA expression were detected after silencing APAF-1 expression by endoribonuclease-prepared small interfering RNAs (esiRNAs) in K562 and MDS-L cell lines. Both erythroid apoptosis rate and APAF-1 mRNA expression of the iron overload (IO) group were significantly higher than those of the non-IO group (P < 0.001 and P < 0.001). There is a significant difference of caspase-9 activity between the IO group and the non-IO group (P < 0.001). Erythroid apoptosis rate and APAF-1 mRNA expression of K562 and MDS-L cell lines significantly elevated after FAC incubation in different concentrations (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L), while erythroid apoptosis rate and APAF-1 mRNA expression in the FAC + DFO group declined (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L). After silencing of APAF-1 expression with specific esiRNAs, erythroid apoptosis rate and APAF-1 mRNA expression of K562 and MDS-L cell lines markedly decreased (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L). APAF-1 plays an important role in iron-induced erythroid apoptosis increase in MDS.

Rigosertib as a selective anti-tumor agent can ameliorate multiple dysregulated signaling transduction pathways in high-grade myelodysplastic syndrome

Rigosertib has demonstrated therapeutic activity for patients with high-risk myelodysplastic syndrome (MDS) in clinical trials. However, the role of rigosertib in MDS has not been thoroughly characterized. In this study, we found out that rigosertib induced apoptosis, blocked the cell cycle at the G2/M phase and subsequently inhibited the proliferation of CD34+ cells from MDS, while it minimally affected the normal CD34+ cells. Further studies showed that rigosertib acted via the activation of the P53 signaling pathway. Bioinformatics analysis based on gene expression profile and flow cytometry analysis revealed the abnormal activation of the Akt-PI3K, Jak-STAT and Wnt pathways in high-grade MDS, while the p38 MAPK, SAPK/JNK and P53 pathways were abnormally activated in low-grade MDS. Rigosertib could markedly inhibit the activation of the Akt-PI3K and Wnt pathways, whereas it activated the SAPK/JNK and P53 pathways in high-grade MDS. A receptor tyrosine kinase phosphorylation array demonstrated that rigosertib could increase the activation of RET and PDGFR-β while reducing the activation of Tie2 and VEGFR2 in MDS cells. Taken together, these data indicate that rigosertib is a selective and promising anti-tumor agent that could ameliorate multiple dysregulated signaling transduction pathways in high-grade MDS.

Iron overload promotes erythroid apoptosis through regulating HIF-1a/ROS signaling pathway in patients with myelodysplastic syndrome

Erythroid apoptosis increases significantly in myelodysplastic syndrome (MDS) patients with iron overload, but the underlying mechanism is not fully clear. In this study, we aim to explore the effect of HIF-1a/ROS on erythroid apoptosis in MDS patients with iron overload. We found that iron overload injured cellular functions through up-regulating ROS levels in MDS/AML cells, including inhibited cell viability, increased cell apoptosis and blocked cell cycle at G0/G1 phase. Interestingly, overexpression of hypoxia inducible factor-1a (HIF-1a), which was under-expressed in iron overload models, reduced ROS levels and attenuated cell damage caused by iron overload in MDS/AML cells. And gene knockdown of HIF-1a got the similar results as iron overload in MDS/AML cells. Furthermore, iron overload caused high erythroid apoptosis was closely related with ROS in MDS patients. Importantly, the HIF-1a protein levels of erythrocytes elevated obviously after incubation with desferrioxamine (DFO) from MDS patients with iron overload, accompanied by ROS levels inhibited and erythroid apoptosis reduced. Taken together, our findings determine that the HIF-1a/ROS signaling pathway plays a key role in promoting erythroid apoptosis in MDS patients with iron overload.

The prognostic impact of multiparameter flow cytometry immunophenotyping and cytogenetic aberrancies in patients with multiple myeloma

Objectives: The aim of this study was to evaluate the prognostic impact of immunophenotyping in patients with multiple myeloma (MM), as well as other markers of disease, such as serum hyaluronan and cytogenetic aberrancies. Methods: We have prospectively analyzed the prognostic impact of antigenic markers, assessed by multiparametric flow cytometry (MFC), in a series of newly diagnosed MM patients (n = 79). Results and discussion: Our results show that the expression of CD44, CD45, and CD28 and the absence of CD117 were associated with a significantly shorter progression free-survival (PFS). Clinical characteristics were collected; Cytogenetic aberrancies were assessed in 40 patients. Multivariate survival analyses identified that the CD117−, CD28+, CD45+, and the percentage of bone marrow plasma cells by MFC are survival predictor, along with the International Staging System stage. Interestingly, the CD117− patients were associated with chromosomal aberrancies, including del (17p), +1q21, and IgH translocations. Conclusion: The incorporation of multiparameter flow cytometry immunophenotyping into the routine diagnostic evaluation of MM patients can help to identify patients at a high risk of progression.

The Evaluation of iron overload through hepcidin level and its related factors in myelodysplastic syndromes

Abstract We chose hepcidin and its related factors as evaluating indicators to determine the degrees of iron overload in myelodysplastic syndromes (MDS) patients. A total of 73 patients and 28 healthy volunteers were enrolled in this study. We performed enzyme-linked immunosorbent assay to measure both bone marrow and peripheral blood serum hepcidin. Real-time quantitative polymerase chain reaction was used to determine the gene expression of growth differentiation factor 15 and twisted gastrulation 1. Serum ferritin (SF), C-reactive protein (CRP), and erythropoietin were measured by routine standard laboratory assays. CD4+ and CD19+ lymphocytes and Th polarization were detected by flow cytometry. Twenty-four MDS patients were measured their cardiac and liver iron deposition levels through magnetic resonance imaging (MRI) T2* examination. No significant difference was found between the bone marrow hepcidin levels and peripheral blood hepcidin levels (P = 0.134). Stratified according to different World Health Organization subtypes, refractory anemia with ringed sideroblasts patients had the lowest hepcidin levels (105.40 ± 5.13 ng/ml), while refractory anemia with excess blasts-1 had the highest levels (335.71 ± 25.16 ng/ml). Stratified according to International Prognostic Scoring System and WHO Classification-based Prognostic Scoring System, there was a significant difference of hepcidin levels between low-risk group and high-risk group in two systems, respectively (P = 0.033 and 0.009). The hepcidin levels of CD4+ high-expression group were demonstrated higher than the normal expression groups (P = 0.02), but the CD19+ high-expression group did not show the same result (P = 0.206). Meanwhile, patients with a Th1 polarization trend had a high level of hepcidin versus normal group (P < 0.001). Liver iron concentration (LIC) measured by MRI T2* had a closer correlation (r = 0.582, P < 0.001) to hepcidin than serum ferritin, by stepwise regression. C-reactive protein and LIC seemed to be the key determinants of hepcidin, by multivariate regression. Inflammation plays an important role in the regulation of hepcidin expression. T-lymphocyte activation and Th polarization trend might participate in the regulatory mechanism partly. The capability of organ iron load assessment of MRI T2* seems better than that of SF. It seems that hepcidin with CRP and LIC measured by MRI T2* are potential indicators of iron overload in MDS patients.

Iron overload promotes mitochondrial fragmentation in mesenchymal stromal cells from myelodysplastic syndrome patients through activation of the AMPK/MFF/Drp1 pathway

Iron overload (IO) has been reported to contribute to mesenchymal stromal cell (MSC) damage, but the precise mechanism has yet to be clearly elucidated. In this study, we found that IO increased cell apoptosis and lowered cell viability in MSCs, accompanied by extensive mitochondrial fragmentation and autophagy enhancement. All these effects were reactive oxygen species (ROS) dependent. In MSCs with IO, the ATP concentrations were significantly reduced due to high ROS levels and low electron respiratory chain complex (ETC) II/III activity. Reduced ATP phosphorylated AMP-activated protein kinase (AMPK). Activation of AMPK kinase complexes triggered mitochondrial fission. Moreover, gene knockout of AMPK via CRISPR/Cas9 reduced cell apoptosis, enhanced cell viability and attenuated mitochondrial fragmentation and autophagy caused by IO in MSCs. Further, AMPK-induced mitochondrial fragmentation of MSCs with IO was mediated via phosphorylation of mitochondrial fission factor (MFF), a mitochondrial outer-membrane receptor for the GTPase dynamin-related protein 1 (Drp1). Gene knockdown of MFF reversed AMPK-induced mitochondrial fragmentation in MSCs with IO. In addition, MSCs from IO patients with myelodysplastic syndrome (MDS) showed increased cell apoptosis, decreased cell viability, higher ROS levels, lower ATP concentrations and increased mitochondrial fragmentation compared with MSCs from non-IO patients. In addition, iron chelation or antioxidant weakened the activity of the AMPK/MFF/Drp1 pathway in MDS-MSCs with IO from several patients, accompanied by attenuation of mitochondrial fragmentation and autophagy. Taken together, the AMPK/MFF/Drp1 pathway has an important role in the damage to MDS-MSCs caused by IO.