Study On The Role Of SDF-1 And SHP-1 In The Development Of MDS Disease

So far, the pathogenesis of MDS (Myelodysplastic syndrome, MDS) has not yet fully addressed, and the diagnosis, classification and treatment of this disease remain largely uncertain. Bone marrow stroma plays a very important role in the generation and differentiation of hematopoietic cells. Bone marrow stromal cell is an important component of hematopoietic stroma. Stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 play a crucial role on HSC/HPC homing, normal hematopoiesis and mobilization from the bone marrow to peripheral blood.To study the role of SDF-1/CXCR4 in MDS, CD34 positive cells from bone marrows of patients were cultured in 60ng SDF-1 to perform transwell invasion assay. The results show that the percentage of invasive cells for low risk group, normal control group and high risk group were (16.7±3.5)%, (18.9±2.4) % and (31.7±3.3)% respectively. There are no significant differences between the control group and the low risk group, but the high-risk group is significantly high (P<0.05). And the concentration of SDF-1αin bone marrow plasma was determined with enzyme-linked immunoassay. The results show the concentration of SDF-1 a in the low risk group, the high-risk group and the control group is 2301.3±413.1pg/ml,1173.3±501.1pg/ml, and 689.3±189.7g/ml respectively and it is statistically significant between either group (P<0.05). The expression of CXCR4 in CD34-positive cells was detected by flow cytometry. CXCR4 positivity in the high risk group, the low risk group and the control group is (59.0±9.5)%, (21.4±5.0)%, and (18.8±3.4)% respectively. Compared to the low risk group or the control group, the high risk group is significantly different (P <0.01), while there is no significant difference between the low risk group and the control group (P> 0.05). The apoptosis in CD34-positive cells was also determined by flow cytometry. In the low risk group, the high risk group and the normal control group, the percentage of apoptotic cells is (56.8±10.2)%, (24.34±7.9)% and (18.5±8.7)% respectively. Compared to the high risk group or the normal control group, the apoptosis rate in the low risk group is significantly different (P<0.01). Therefore, we conclude that, compared with the normal control, the CXCR4 expression is normal in the CD34-positive cells from the MDS patients with low risk, but the bone marrow stromal cells produce excess SDF-1a factor, resulting in extremely high bone marrow apoptosis, and leading to the typical clinical phenotype. However, in the high risk MDS patients, compared with low risk patients, the number of CD34 positive cells expressing CXCR4 is significantly increased, while the bone marrow SDF-la levels decrease and the apoptosis is significantly decreased. So the SDF-1/CXCR4 axis plays a very important role in the invalid hematopoiesis in bone marrow of low risk MDS patients and in the progression from low risk to high risk.SHP-1 gene was recently identified as a tumor suppressor gene which negatively regulates JAK/STAT pathway and promoter methylation is the main mechanism for silence of its expression. To figure out if SHP-1 plays a role in MDS, methylation specific PCR was used to detect methylation in promoter region of SHP-1 gene. In 18.2% of samples in the normal control and low risk group, SHP-1 gene was found to be methylated, while in high risk group, the percentage is increased to 71.4%, and in SKK-1 cell line SHP-1 is partially methylated. In normal control group no methylation was detected. The sequencing results of methylation PCR products further confirm the specificity of MSP. Our data suggest that promoter methylation of SHP-1 gene may activate the JAK/ STAT pathway and play a role in MDS development.In summary, bone marrow stromal cells through SKD-1/CXCR4 axis, and promoter methylation of SHP-1 gene, may be involved in MDS development and could be targeted for MDS therapy.