OBJECTIVETo investigate the expression of apoptotic protein inhibitors, survivin and XIAP, in patients with myelodysplastic syndromes (MDS) and in the cell line MUTZ-1, as well as to explore the possible mechanisms of homoharringtonine (HHT) in the treatment of MDS.

METHODSBone marrow samples from 47 patients with de novo MDS at diagnosis were examined and bone marrow samples from 15 normal donors were used as control. A MDS-RAEB cell line MUTZ-1 was used as in vitro model. Detection of apoptotic cells and cell cycle analysis were performed with flow cytometry (FACS). The expression of apoptotic protein inhibitor survivin and XIAP in the MDS cells were detected by RT-PCR technique. MUTZ-1 were treated with antisense oligodeoxynucleotide (AS-ODNs) of survivin and or HHT, the effects were evaluated by cell viability and cell apoptosis.

RESULTSSurvivin mRNA positive rate in MDS were significantly higher than that in normal controls (38.3% and 0, respectively, P < 0.01), and the positive rate in high risk group (RAEB, RAEBT and CMML) was significantly higher than that in RA/RAS group (53.6% and 16.7%, respectively, P < 0.05). XIAP was expressed in all untreated MDS and healthy controls. XIAP mRNA expression in high risk group was significantly higher than that in RA/RAS subtypes and healthy controls (1.55 +/- 0.34, 0.74 +/- 0.24, and 1.01 +/- 0.28, respectively, P < 0.01). However, XIAP mRNA expression was significantly lower in RA/RAS subtypes than in healthy control (0.74 +/- 0.24 and 1.01 +/- 0.28, P < 0.054). Apoptosis peak detected by FACS analysis and positive Annexin V FITC staining on cell membrane indicated that HHT could induce MUTZ-1 cell undergoing apoptosis in dose- and time-dependent manners. Treatment of MUTZ-1 cells with HHT revealed that HHT could significantly down-regulate survivinexpression but had no significant effect on XIAP expression in the cells. AS-ODNs of survivin could inhibit MUTZ-1 cells growth, induce them to apoptosis and sensitize them to HHT.

CONCLUSIONThe expression levels of survivin; Institute of Hematology, Oncology and Tumor Immunology, Robert Roessle Clinic, Humboldt University, Berlin, Germany (Wolf Dieter Ludwig, Christian Wuchter) and XIAP vary in different subtypes of MDS patients, suggesting that the proteins may play an important role in the pathogenesis of the disease. Down-regulation of survivin in MUTZ-1 cells may be one of the mechanisms that HHT induces apoptosis of MDS cells.