[Research Advances on Role of Extracellular Vesicles in the Bone Marrow Microenvironment of Patients with Hematological Malignancies--Review].

Bone marrow (BM) microenvironment appears to play an important role in the pathogenesis of hematological malignancies. Apart from soluble factors and direct cell-cell contact, the extracellular vesicles (EVs) were identified as a third mediator for cell communication within BM microenvironment. Recently, more and more evidences have demonstrated that EVs are also involved in the dysregulation of the BM microenvironment in patients with hematological malignancies. Therefore this review focuses on the biological characteristics of EVs, the clinical value of EVs as biomarkers, the BM microenvironment reprogramming in hematological malignancies by EVs, and the potential role of EVs in drug resistance and therapy of hematological malignancies.

Clinical significance of hyaluronan levels and its pro-osteogenic effect on mesenchymal stromal cells in myelodysplastic syndromes.

BACKGROUND: Hyaluronan (HA), a major component of the extracellular matrix, has been proven to play a crucial role in tumor progression. However, it remains unknown whether HA exerts any effects in myelodysplastic syndromes (MDS). METHODS: A total of 82 patients with MDS and 28 healthy donors were investigated in this study. We firstly examined the bone marrow (BM) serum levels of HA in MDS by radioimmunoassay. Then we determined HA production and hyaluronan synthase (HAS) gene expression in BM mesenchymal stromal cells (MSC) and mononuclear cells derived from MDS patients. Finally, we investigated the effects of HA on osteogenic differentiation of MSC. RESULTS: The BM serum levels of HA was increased in higher-risk MDS patients compared to normal controls. Meanwhile, patients with high BM serum HA levels had significantly shorter median survival than those with low HA levels. Moreover, the HA levels secreted by MSC was elevated in MDS, especially in higher-risk MDS. In addition, HAS-2 mRNA expression was also up-regulated in higher-risk MDS-MSC. Furthermore, we found that MSC derived from MDS patients with high BM serum HA levels had better osteogenic differentiation potential. Moreover, MSC cultured in HA-coated surface presented enhanced osteogenic differentiation ability. CONCLUSIONS: Our results show that elevated levels of BM serum HA are related to adverse clinical outcome in MDS. Better osteogenic differentiation of MSC induced by HA may be implicated in the pathogenesis of 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.

Genomic loss of EZH2 leads to epigenetic modifications and overexpression of the HOX gene clusters in myelodysplastic syndrome.

The role of EZH2 in cancer is complex and may vary depending on cancer type or stage. We examined the effect of altered EZH2 levels on H3K27 methylation, HOX gene expression, and malignant phenotype in myelodysplastic syndrome (MDS) cell lines and an in vivo xenograft model. We also studied links between EZH2 expression and prognosis in MDS patients. Patients with high-grade MDS exhibited lower levels of EZH2 expression than those with low-grade MDS. Low EZH2 expression was associated with high percentages of blasts, shorter survival, and increased transformation of MDS into acute myeloid leukemia (AML). MDS patients frequently had reductions in EZH2 copy number. EZH2 knockdown increased tumor growth capacity and reduced H3K27me3 levels in both MDS-derived leukemia cells and in a xenograft model. H3K27me3 levels were reduced and HOX gene cluster expression was increased in MDS patients. EZH2 knockdown also increased HOX gene cluster expression by reducing H3K27me3, and H3K27 demethylating agents increased HOX gene cluster expression in MDS-derived cell lines. These findings suggest genomic loss of EZH2 contributes to overexpression of the HOX gene clusters in MDS through epigenetic modifications.

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.

[Osteogenic Differentiation Potential of Bone Marrow Mesenchymal Stem Cells in Patients with Myelodysplastic Syndromes].

OBJECTIVE: To investigate the osteogenic differentiation potential of bone marrow mesenchymal stem cells (BMMSC) in patients with myelodysplastic syndromes (MDS) and to explore the role of BMMSC osteogenic differentiation in the pathogenesis of MDS. METHODS: BMMSC were isolated from bone marrow of patients with MDS and healthy donors, then expanded in vitro. The expression of transcription factor gene RUNX2, Osterix and osteogenic differentiation markers (ALP, BSP, OPN, OCN) were measured by real-time PCR, the alkaline phosphatase(ALP) activity was assessed at 3, 7, 10 days after osteogenic differentiation. Mineralization analysis was performed at day 21 of osteogenic induction. RESULTS: The expression level of RUNX2 and Osterix were significantly decreased in BMMSC from lower-risk MDS patients compared with normal controls (P<0.05). After osteogenic induction, low-risk MDS showed lower alkaline phosphatase activity at day 3 (P<0.05), less intense alizarin red S staining at day 21 (P<0.05), and lower gene expression of osteogenic differentiation markers (P<0.05), however, these expressions in higher-risk MDS were normal. CONCLUTION: BMMSC from low-risk MDS have abnormalities in osteogenic differentiation, it may contribute to the ineffective hamatopoiesis of MDS.

[mRNA expression of notch ligand-delta-like-1 and jagged-1 in mesenchymal stem cells of MDS patients].

This study was aimed to investigated the mRNA expression levels of Notch ligands- Delta-like-1 and Jagged-1 in bone marrow mesenchymal stem cells of patients with myelodysplastic syndrome (MDS), and to explore their relation with onset of MDS. Bone marrow mesenchymal stem cells of 38 patients with MDS and 16 normal subjects as control were collected to detect mRNA expression of Delta-like-1 and Jagged-1 by using real-time quantitative polymerase chain reaction. The results showed that the expression levels of Delta-like-1 and Jagged-1 in mesenchymal stem cells of MDS patients were significantly higher than that in normal controls (P < 0.05). According to WHO criteria, the mRNA expression of Delta-like-1 in RA/RAS, RCMD and RAEB groups were significantly higher than that in normal controls (P < 0.05), the mRNA expression of Jagged-1 in RAEB group was also significantly higher than that in normal controls (P < 0.05). The mRNA expression of Delta-like-1 was significantly correlated with the proportion of blasts in the bone marrow of MDS patients (r = 0.502, P < 0.05). The expression levels of Delta-like-1 and Jagged-1 in MDS patients with abnormal karyotypes were significantly higher than those in MDS patients with normal karyotypes (P < 0.05). The mRNA expression of Delta-like-1 in higher risk group according to International Prognostic Scoring System was significantly higher than that in lower risk group (P < 0.05), there was no significant difference in Jagged-1 expression levels between higher risk group and lower risk group (P > 0.05). It is concluded that the changes of Delta-like-1 and Jagged-1 expression level in MSC may play a role in the pathogenesis of myelodysplastic syndrome.

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-ß 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.

[Roles of osteoblasts in hematopoietic stem cell niche and relationship between osteoblasts and hematopoietic diseases].

Hemopoietic stem cells(HSCs) are regulated by two niches: osteoblastic niche and vascular niche. Osteoblasts are the critical constitutive regulators of the osteoblastic niche. The significance of osteoblasts for hematopoietic disease has not escaped attention. This review attempts to capture the discoveries of the last few years regarding the role of osteoblasts in hematopoietic stem cell niche and relationship between osteoblasts and hematopoietic diseases.

[Research advance of hematopoietic microenvironment for myelodysplastic syndromes].

Myelodysplastic syndrome (MDS) is a group of heterogeneous clonal diseases characterized by ineffective hematopoiesis, peripheral blood cytopenias and high risk of transformation to acute myeloid leukemia.Recently more and more investigations indicate that the abnormality of bone marrow microenvironment is one of important reasons related to MDS. In this article the abnormality of stroma cells, cytokines and signaling pathways in hematopoietic micro-environment of MDS is reviewed.