Page 4 of 5 GRAF level 2.76 45.90 3.22 0.49 0.76 0.25 1.02 No. 1 2 3 4 5 6 7 Sex F F M M M M M 51 63 67 74 85 39 41 RAEB-2 RCMD RAEB-1 RARS RAEB-1 RCMD RAEB-1 46, XX 46, XX, del(20)(q11) 46, XY 46, XY, del(5)(q13q33) 46, XY, del(5)(q13q33) 46, XY 44-45, XY, del(5)(q13q33), -7, -15, -21[cp] Qian et al. Journal of Experimental & Clinical Cancer Research 2010, 29:111 http://www.jeccr.com/content/29/1/111 Table 2 Clinical and laboratory characteristics of patients with MDS Age (year) Diagnosis Karyotype transcript was lower in these cases (0.49-1.02, median 0.76) than the other four cases without 5q- (0.25-45.90, median 2.99), however, statistical difference was not observed (P > 0.05). Discussion In this study, we demonstrated that the expression level of GRAF transcript was decreased in primary leu- kemic cells of all types of myeloid malignancies. Boje- sen et al [10] found that GRAF promoter was hypermethylated in 38% cases with AML and MDS but not in healthy individuals, however, they did not detect the GRAF transcript in primary leukemic cells of AML and MDS. GRAF contains a centrally located GTPase- activating protein (GAP) domain, followed by a serine/ proline rich domain and a carboxy-terminal Srchomol- ogy 3 (SH3) domain. GRAF acts as a negative regulator of RhoA because the GRAF GAP domain enhances GTP hydrolysis of both Cdc42 and RhoA in vitro [7]. Rho family GTPases play a role in the growth control besides regulating the organization of the actin cytos- keleton [18,19]. RhoA inhibits p21Cip1, p27Kip and p16Ink4 activities, permitting cell cycle progression [20-24]. Furthermore, RhoA has been shown involved in the regulation of apoptosis, migration, proliferation, differentiation [18,19]: for example, in vitro, constitu- tively active RhoA can stimulate transformation. In normal epithelia, RhoA contributes to the generation of epithelial polarity and junction assembly and func- tion but also affects epithelial disruption during tumor progression [25]. Recently, clinical studies have revealed the correlation of increased expression of RhoA and invasion, metastasis and progression of sev- eral solid tumors including liver, bladder, esophageal, head and neck, ovary, gastric, testicular, lung and breast carcinomas [18]. As an upstream regulator, the loss of function of GRAF might prevent the physiologic down-regulation of RhoA and lead to the repression of p21. Then, the GRAF-defective cell will be driven into the S phase [9]. Several mechanisms, including translo- cations, allelic loss, insertions and promoter methyla- tion observed in AML and MDS, can lead to the inactivation of GRAF [9,10]. The mechanisms responsible for the disease progres- sion of CML remained poorly understood. Recent stu- dies have suggested that several alterations promote this progress, including differentiation arrest caused by the suppression of translation of the transcription factor CEBPa induced by the BCR-ABL oncoprotein in CML cell, increasing genomic instability in CML cell resulting from the reduced capability of genome surveillance sys- tem, telomere shortening and loss of tumor suppressor gene (TSG) such as TP53, retinoblastoma 1, CDKN2A, DAPK1 and others [16,26,27]. Interestingly, we found that GRAF transcript was further down-regulated during CML progression. p210 Bcr-Abl, containing a centrally located Rho-specific guanine nucleotide exchange fac- tors (RhoGEF) domain, affects the actin cytoskeleton assembly and thereby the cellular adhesion and migra- tion by RhoA signaling pathway [28]. Further studies are required to elucidate the function of GRAF and RhoA in the pathogenesis and progression of CML. Our preliminary results showed that MDS with 5q deletion might have lower expression of GRAF than those without 5q deletion. Deleted 5q is a one of com- mon chromosomal abnormalities in AML and MDS. Although GRAF maps telomeric to the previously deli- neated commonly deleted 5(q31) region, Borkhardt et al found that one allele of GRAF was consistently lost in all studied 10 patients with 5q deletion and with either MDS or AML [9]. Besides GRAF deletion, abnormal methylation of GRAF promoter was also observed in AML and MDS [10]. These results suggested that hap- loinsufficiency (i.e., decreased GRAF mRNA expression) caused by deletion of GRAF allele or promoter methyla- tion might be instrumental in the development and pro- gression of hematopoietic malignancies. In conclusion, GRAF mRNA is decreased in myeloid malignancies. Whether the GRAF expression level could improve the stratification or prognostication of patients with myeloid diseases should be further addressed in future studies. Acknowledgements This study was supported by Jiangsu Province’s Key Medical Talent Program (RC2007035) and Social Development Foundation of Zhenjiang (SH2006032).