Rap1 is a small G protein belonging to the RAS superfamily. Rap1 signalling has effects on cell growth, cell proliferation and involves in regulation of the mitogen activated protein (MAP) kinase or ERK (extracellular signal regulated kinase) cascade. Rap1 will directly activate ERK through B-Raf. B-Raf is a member of Raf family, and presents in neuronal and hematopoietic cells. Oncogenic mutations of gene RAS are most frequent and detected in 20% - 30% of human leukemias and 10% - 15% of MDS cases. The review summarizes the regulatory function of Rap1 in development of hematopoietic cells and effect of Rap1 in hematologic malignancies.
Hematologic Neoplasms ; genetics ; metabolism ; Humans ; Signal Transduction ; rap1 GTP-Binding Proteins ; genetics ; metabolism

Previous study on the gene expression profile of human MDS by using microarray discovered that transcription of RAP1GAP was up-regulated, which was confirmed by quantitative RT-PCR in expanding cohort of MDS patients. This study was pourposed to investigate the expression of RAP1GAP in human MDS and its clinical relevance. The expression of RAP1GAP in bone marrow cells of 19 MDS patients was detected by flow cytometry and was compared with that in patients with non-malignant blood diseases and acute leukemias, meanwhile the relevance between expression level of RAP1GAP and hemoglobin, leukocytes, platelets, blasts percentage in bone marrow cells and IPSS score was analyzed. The results indicated that the expression level of RAP1GAp in MDS patients significantly increased as compared with patients with non-malignant blood diseases or AML (8.42 +/- 8.37% vs 2.97 +/- 4.75% or 2.26 +/- 4.24%). Among MDS patients, the expression level of RAP1GAP in MDS-RA was significantly higher than that in MDS-RAEB (11.64 +/- 9.07% vs 4.37 +/- 4.65%). However, no definitive correlation of expression level with above-mentioned clinical parameters was found in detected patients with DMS. In conclusion, the expression of RAP1GAP in MDS patients obviously increases, the relationship between expression level of RAP1GAP and laboratory hematological parameter and IPSS score does not be confirmed. The role played by RAP1GAP expression in the pathogenesis of MDS and its clinical significance during progression of MDS towards AML deserves further studies.
Adult ; Aged ; Aged, 80 and over ; Female ; Flow Cytometry ; GTPase-Activating Proteins ; genetics ; metabolism ; Gene Expression Profiling ; Humans ; Male ; Middle Aged ; Myelodysplastic Syndromes ; genetics ; metabolism