Analysis the Expression of Rho Family GTPases and Its regulator's in Myelodysplastic Syndrome.

Abstract 2779

Poster Board II-755

The myelodysplastic syndrome (MDS) is a group of clonal hematological disorders characterized by some shared features of refractory cytopenia, dysplastic cellular morphology, and a propensity toward malignant transformation. The variable manifestations and clinical courses are reflected in evolving classification schemes based largely on the morphology of BM cells in aspirate smears and in biopsies. The diagnosis of MDS based on morphology of BM cells is somehow difficult due to the lack of “golden standard”. However, dysplasia is one of the most distinct features of MDS, which may be closely related to cytoskeleton. Rho family GTPases are important network which regulate cytoskeleton. Study on the expression of Rho family GTPases members including RAC1, RAC2, RhoH, RhoBTB3 and its regulator of SPA-1, Rap1GAP in MDS cells may help to explore the mechanism of MDS, and to provide possible biomarkers for differential diagnosis of MDS. To approach this issue, 111 BM specimens were collected and classified into five groups consisting of RA(22), RAEB(22), RAEBt(9), AML(33), and control group (22, including hyperplastic anemia , iron deficiency anemia, leukocytopenia and thrombocytopenia etc ). The mononuclear cells were isolated by Ficoll density gradient centrifugation, and the relative expression level of RAC1, RAC2, RhoH, RhoBTB3, SPA-1 and Rap1GAP compared with GAPDH were detected by quantitative real time reverse transcription PCR. Wilcoxon non-parametric test and SNK method were used to analyze the expression level of these genes among different groups. No difference could be found in expression of RAC1 and RhoH among five groups, while the expression of RAC2, Rap1GAP and SPA-1 showed significant difference among groups (P=0.0002, P<0.0001 and P=0.0182 respectively). For RAC2, The highest expression level was found in RA group and the lowest level in AML with RAEB in between. Significant difference were found between RA and control group, RA and AML, RAEB and AML, respectively. The expression of Rap1GAP differed between AML and MDS, and among the MDS groups, the expression level sequentially decreased from RA to REAB, RAEBt, control and AML. There were no difference in SPA-1 expression compared within each pair of groups However, an elevated tendency could be seen from control group to RA, RAEB, REABt, and the expression decreased dramatically to the lowest expression level in AML. For RhoBTB3, there were no difference among groups if the significant level was set at 0.05(P=0.0620), but when it was compared between two groups, a significant difference could be seen between RAEBt and others, and RAEBt had the highest expression level. The study on expression profile of Rho family GTPases in MDS had not been reported so far. Their effects on the cell morphology focused primly on some fibroblasts. The results of our present study suggested that the expression and function of Rho family GTPases, especially RAC2, Rap1GAP and RhoBTB3, may play important roles in the development and progression of MDS. Their altered expression pattern could provide valuable biomarkers to help the diagnosis and stratification of MDS and to understand its pathogenesis.