Simultaneous suppression of multidrug resistance and antiapoptotic cellular defense induces apoptosis in chemoresistant human acute myeloid leukemia cells.

The emergence of acquired drug resistance is a major hurdle in the successful treatment of leukemia. Researches indicated that the main mechanisms of most cancers included so-called "pump" and "nonpump" resistance. We studied the mechanisms involved in the drug resistance of HL-60/ADR and found that its drug resistance was associated with the simultaneous overexpression of XIAP and MRP. We compared the reversal effects of XIAP and MRP ASO used in combination and separately. Reverse transcription-PCR and Western blot were applied to examine the changes of mRNA and protein levels, respectively. The results showed that XIAP and MRP ASO used separately could down-regulate the expression of XIAP and MRP in HL-60/ADR cells, respectively. XIAP and MRP ASO used in combination did not enhance the inhibition expression of XIAP and MRP of HL-60/ADR cells. The apoptosis of co-transfection group was significantly higher than XIAP ASO (P<0.05). The cytotoxicity was determined by MTT cell viability/proliferation assay. When used in combination the sensitivity of HL-60/ADR cells to DNR was increased significantly compared with XIAP or MRP ASO used separately (P<0.05). The results indicated that both XIAP and MRP were involved in the drug resistance mechanisms of HL-60/ADR cells. The sensitivity to DNR could be enhanced significantly when XIAP and MRP ASO used in combination.

[A modified cytogenetic study for multiple myeloma].

OBJECTIVE: To evaluate the effect of modified culture method used to cytogenetic analysis and the clinically significance of chromosomal abnormalities to multiple myeloma (MM). METHODS: Mononuclear cells were isolated from bone marrow aspirate of 20 MM patients; and then cultured for 3 days without any cytokines, and 6 days in the presence of IL-6 (10 ng/mL) and GM-CSF (30 ng/mL) before RHG banding analysis; the remained part of aspirates were treated directly. Eight cases of iron deficiency anemia were taken as control. RESULTS: The experiment was failure in 2 cases because of blood clot, and another 2 cases could be analyzed only by direct method due to inadequate cells. The karyotype abnormalities were found from 4 cases of 16 available patients. Of them, three cases had complex karyotypes. The abnormalities were detected after 6 days culture with addition of cytokines. No abnormalities were detected from those groups of directly analysis and 3 day culture. Meantime, the clinical data showed that the patients with cytogenetic abnormalities were in stage III, and had a high percentage of MM cells (25%-56%) in their bone marrow, and also poor responses to prior chemotherapy. No cytogenetic abnormalities were found from control individuals in all groups. CONCLUSION: Extended culture in the presence of cytokines could improve the efficiency of cytogenetic analysis to MM. Complex karyotype was common cytogenetic abnormalities in MM patients with poor response to chemotherapy.

[Partial deletion of chromosome 13 long arm in multiple myeloma and its clinical significance].

OBJECTIVE: To explore the specific locus deletion of the long arm of chromosome 13 and its relationship with the clinical behavior and prognosis of multiple myeloma (MM). METHODS: FISH analysis was performed on bone marrow smears from 68 patients with MM to study the deletion of Rb-1 gene and locus 13q14.3 on chromosome 13. The statistic value of its effect on clinical features were determined. RESULTS: 35 out of the 68 (51%) cases were found with deletion of chromosome 13; deletion of Rb-1 gene were found in 29 (43%) cases; deletion of locus 13q14.3 were found in 23 out of 44 (52%) cases; the analysis results were same in 66% of the cases (29/44) with the above two probes. Chi-square test showed that partial deletion of chromosome 13 was associated with clinical behavior, early chemotherapy response and 1 year survival. CONCLUSION: Deletion of Rb-1 gene and locus 13q14.3 were both common cytogenetic changes in MM patients with effect on the biological behavior of the disease.

[An analysis of leukocyte subsets chimerism following allogeneic peripheral blood stem cell transplantation].

OBJECTIVE: To analyse the relationship of T lymphocyte and granulocyte chimerism following allogeneic peripheral blood cell transplantation and the occurrence of relapse, graft failure and graft versus host disease. METHODS: 21 patients underwent allogeneic peripheral blood stem cell transplantation (allo-PBSCT). Fluorescence-activated cell sorter (FACS) sorted CD3+ T lymphocytes and CD15+ granulocyte from peripheral blood of all the patients were analyzed for short tandem repeats in 7 days interval for 1 month starting from the day of PBSCT, then 1 month interval for 6 months, and then 3 months interval to the end of one year. RESULTS: Chimerism of granulocyte was higher than T lymphocyte on day 7 posttransplant in 4 patients given myeloablative conditioning. The median donor chimerism of granulocyte and T lymphocyte was 95% and 55% respectively. The other 17 patients had higher chimerism of T lymphocyte than granulocyte on day 7, which was 60% (15%-76%) and 0% (0%-40%) respectively. 20 patients reached complete donor chimerism (CDC) on day 21 (14-102 days) for T lymphocyte and on day 14 for granulocyte, except one relapsed on day 28. Seven patients had decreasing mixed chimerism when disease relapsed or graft failure occurred. T cell donor chimerism decreased earlier than myeloid cells, however, bone marrow sample and granulocyte still remained in complete donor chimerism or stable mixed chimerism, bone marrow smear showed normal at the same time. CONCLUSION: Blood leukocyte subset chimerism analysis, especially T cell chimerism analysis may provide earlier information of engraftment, relapse and graft failure than blood and bone marrow samples, therefore immunomodulatory therapies may be given to recipients earlier and overall survival may be improved.

Chronic myelogenous leukemia-like hematological malignancy with t(8;22) in a 26-year-old pregnant woman: A case report.

t(8;22)(p11;q11) is a rare but recurrent genetic alteration in various hematological disorders. Patients with t(8;22)(p11;q11) may be misdiagnosed with chronic myelogenous leukemia (CML), due to the similar clinical features. Thus, the current study presents a patient with t(8;22)(p11;q11) who was previously misdiagnosed with CML in the chronic phase. The current patient was a 26-year-old woman who was 4-weeks pregnant and in whom an increased white blood cell count (4.0×1010/l) was found upon physical examination. The patient had no history of hematological disease. Although cytogenetics showed a normal karyotype and no breakpoint cluster region/Abelson murine leukemia viral oncogene homolog 1 (BCR/ABL) fusion gene was detected by reverse transcription-polymerase chain reaction, a diagnosis of chronic myelogenous leukemia (CML) was initially made according to the clinical and morphological features. Another 6 weeks later, t(8;22)(p11;q11) rearrangement was present in 9 out of 10 analyzed metaphases. Fluorescence in situ hybridization and reverse transcription-polymerase chain reaction indicated a negative result for the BCR/ABL fusion, but gave a positive result for the BCR-fibroblast growth factor receptor 1 fusion. A hematological diagnosis of atypical CML was again formed.

[Value of a Panel Fluorescence in Situ Hybridization in Three Kinds of Hematological Malignancies].

OBJECTIVE: To evaluate the role of a panel fluorescence in situ hybridization (Panel-FISH) for the detection of common cytogenetic abnormalities in patients with chronic lymphoblastic leukemia (CLL), multiplemyeloma (MM) and myelodysplastic syndrome (MDS). METHODS: Three panels of probes were used to perform FISH assays in 46 patients with CLL, 53 with MM and 93 with MDS. Their results were compared with that obtain by conventional cytogenetic examination. RESULTS: The panel FISH detection in CLL and MM groups showed significantly higher sensitivity in revealing chromosomal abnormalities than that in conventional cytogenetics (73.8% vs 9.5%, 70.8% vs 22.9%, respectively). There were significant differences between these 2 technologies(P<0.001, P<0.001, respectively). However, there was no difference between Panel-FISH and conventional cytogenetics in MDS group (30.4 vs 27.2%, P=0.625). CONCLUSION: Panel-FISH can increase the detection rate in CLL and MM patients while it did not in MDS patients. However, it can increase the detection rate of aberration clones in MDS cases with normal karyotypes or without enough karyotypes to be analysis.

Is there a role for B lymphocyte chimerism in the monitoring of B-acute lymphoblastic leukemia patients receiving allogeneic stem cell transplantation?

OBJECTIVE: To determine the sensitivity and significance of B-cell chimerism for the detection of early engraftment, transplant rejection, and disease relapse. METHODS: The dynamic monitoring of lineage-specific cell subtypes (B, T, and NK cells) was made in 20 B-cell acute lymphoblastic leukemia (B-ALL) patients following allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the early period after allo-HSCT, the latest establishment of B-cell complete chimerism (CC) was observed in a majority of patients. RESULTS: The percentage of donor cells of B-cell lineage was lower than the percent of T-cell lineage in most of the mixed chimerism (MC) patients. During graft rejection, the frequency of patients with decreasing MC of B-, T- and NK-cell lineage were 5/5, 2/5, and 2/5. When disease relapsed, five patients showed a faster decrease of the donor percent of B-cells than of T- or NK-cells. Only one patient displayed a more rapid decrease in NK-cells than in T- or B-cells. CONCLUSION: Monitoring of B-cell chimerism after HSCT seems to be valuable for insuring complete engraftment, anticipating graft rejection, and relapse in B-ALL patients.

JAK2 V617F detected in two B-cell chronic lymphocytic leukemia patients without coexisting Philadelphia chromosome-negative myeloproliferative neoplasms: A report of two cases.

The JAK2 V617F mutation has been observed in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-MPNs), including polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis. This mutation has also been observed in a small number of other myeloid malignancies, such as acute myeloid leukemia, chronic myeloid leukemia and myelodysplastic syndrome. The JAK2 V617F allele has rarely been evaluated in lymphoproliferative disorders. In total, 28 JAK2 V617F-positive B-cell lymphocytic leukemia (B-CLL) patients have previously been reported and all presented with Ph-MPN concomitantly. However, following investigation of the JAK2 V617F mutation in 63 B-CLL patients at the Shanghai First People's Hospital (Shanghai, China) between January 2008 and December 2012 via allele-specific polymerase chain reaction, two B-CLL patients without a history of Ph-MPN were identified to carry the JAK2 V617F allele.

Coexistence of JAK2V617F Mutation and BCR-ABL Translocation in a Pregnant Woman with Essential Thrombocythemia.

In 2012, a 25-years-old pregnant woman presented with thromocytosis for 4 months, blood counts showed platelets 701 × 10(9)/L. Bone marrow examination disclosed a feature of hypercellular marrow in erythrocytic,granulocytic and megakaryocytic series. Cytogenetic analysis showed t(9;22)(q34;q11) in 100 % of metaphase. The percentage of BCR-ABL-positive FISH signals was 37 % in the peripheral blood. Molecular analysis showed the presence of the JAK2V617F mutation and BCR-ABL mRNA b3a2 transcript. A diagnosis of concomitant presence of essential thrombocythemia and chronic myelocytic leukemia was made. Based on this case and literatures reported before, it might be necessary to detect JAK2-V617F mutation and BCR-ABL fusion gene concomitantly in myeloproliferative neoplasms patients.

Chimerism status is correlated to acute graft-versus-host disease after allogeneic stem cell transplantation.

To evaluate the correlation between chimerism status and acute graft-versus-host disease (aGVHD) following allogeneic hematopoietic stem cell transplantation. Chimerism of peripheral blood of 124 patients was monitored at regular intervals post-transplant. The chimerism of 124 post-transplant cases of CD3(+)T lymphocytes, 107 cases of CD3(-)CD56(+)CD16(+)NK lymphocytes, 49 cases of CD15(+) granulocytes, and 27 cases of CD19(+)B lymphocytes sorted by fluorescence-activated cell sorter were analyzed by polymerase chain reaction amplification of short tandem repeats. Differences were found in the time between establishment of full donor T-cell chimerism and the occurrence of aGVHD (P = 0.035, two related samples test). Patients with ≥69 % donor chimerism on day +7 in T-cells had higher rates of aGVHD. This study may provide a rational basis for treatment with adoptive immunotherapy at an earlier time, such as day 7 after SCT, than at present to prevent aGVHD.

JAK2 V617F positive essential thrombocythemia developing in a patient with CD5⁻ chronic lymphocytic leukemia.

Coexistence of chronic lymphocytic leukemia (CLL) and essential thrombocythemia (ET) in a patient is extremely rare, with only 10 cases reported thus far in literature. This paper describes a 94-year-old male having atypical B-CLL with CD5⁻ (CD5⁻) phenotype and ET. In this patient, we performed interphase fluorescence in situ hybridization (FISH) analysis which revealed 13q14.3 deletion in 31% of B-lymphocyte nuclei and RB1 deletion in 27% of B-lymphocyte nuclei, but not in neutrophils and T-lymphocytes. Furthermore, we identified JAK2 V617F mutation in the peripheral blood nucleated cells and neutrophils, but not in the B- and T-lymphocyte populations. Therefore, it was concluded that the occurrence of CD5− B-CLL and ET in this patient was pathogenically independent.

[Comparison of STR-PCR and FISH value for monitoring chimerism after sex-mismatched allogeneic hematopoietic stem cell transplantation].

This study was purposed to compare the significance of multiplex short tandem repeat polymerase chain reaction (STR-PCR) and fluorescent in situ hybridization (FISH) for monitoring chimerism after sex-mismatched allogeneic hematopoietic stem cell transplantation (allo-HSCT). The chimerism of bone marrow or peripheral blood cells from 38 patients was analyzed by STR-PCR and FISH on days 14, 28 and at 3 months after allo-HSCT. The results indicated that on day 14, the complete chimerism (CC) was detected in 14 of 30 cases by STR-PCR and in 8 of 30 cases by FISH (p > 0.05). On day 28, the CC was detected in 26 of 31 cases by STR-PCR and in 15 of 31 cases by FISH (p < 0.01). At 3 months, the CC was observed in 22 of 24 cases by STR-PCR and 17 of 24 cases by FISH (p > 0.05). 14 cases were found to have a graft rejection or relapse among 28 cases which were continuously monitored more than 3 months post the transplants. Donor cell decrease in 9 of 14 cases was proved by FISH alone. It is concluded that FISH is more sensitive than STR-PCR in early monitoring chimerism status of post-transplant and in predicting graft rejection or disease relapse.

[Allogeneic hematopoietic stem cell transplantation following reduced intensity conditioning regimen for treatment of refractory leukemia].

OBJECTIVE: To evaluate the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) following reduced intensity conditioning (RIC) regimen for treatment of refractory leukemia. METHODS: Twenty patients with refractory leukemia received allo-HSCT following RIC regimen consisting of fludarabine plus small or moderate dose total body irradiation (TBI). Graft versus host disease (GVHD) prophylaxis was CsA plus mycophenolate mofetil (MMF) or short-term MTX, or these three drugs combination; CD25 monoclone antibody(McAb) and ATG were also used in some of the patients. RESULTS: Seventeen patients engrafted successfully, the median time for ANC > 0.5 x 10(9)/L was 13 (11 - 17) days, and for BPC > 50 x 10(9)/L 19 (12 -42) days. Detected by short tandem repeat (STR)-PCR, complete donor chimerism was confirmed in 16 patients with a median of 14 (7 -35) days. The incidence of acute and chronic GVHD was 47.1% (8/17) and 38.5% (5/13) respectively. The transplant related mortality (TRM) was 25.0% (5/20), mainly from graft failure, intracranial hemorrhage and severe infection. Up to now, 7 patients relapsed and 9 were alive with leukemia free. The overall survival (OS) at 2 year was (35. 3 +/- 14.2)% for all patients and (52.5 +/- 18.6)% for acute non-lymphocytic leukemia (ANLL) patients. CONCLUSION: Allo-HSCT following fludarabine and TBI based RIC regimen can be used for treatment of refractory leukemia with well tolerance and low TRM and there is a better prognosis for ANLL patients than that for acute lymphocytic leukemia patients.

The association of up-regulation of X-linked inhibitor of apoptosis protein with cell adhesion-mediated drug resistance in U937 cells.

An increasing body of evidence indicates that environmental factors may contribute to the drug resistance of acute myeloid leukaemia (AML). CAM-DR (cell adhesion-mediated drug resistance) is a reversible, de novo drug resistance induced by adhesion of tumour cell lines to fibronectin (FN). Adhesion was demonstrated to directly regulate the apoptotic machinery. And it was observed in previous studies that high levels of X-linked inhibitor of apoptosis protein (XIAP) were related to resistance to chemotherapeutics in many cancer cell lines. However, whether XIAP is relevant to CAM-DR of AML cells is unknown. In this report, we demonstrated that the mRNA and protein levels of XIAP were increased by 96.15% and 120.92%, respectively in U937 cells cocultured with FN as compared with controls. Antisense oligonucleotides targeting XIAP down-regulated the expression of XIAP and sensitized U937 cells to daunorubicin. In addition, we investigated the signalling pathway involved in the upregulation of XIAP. The levels of phosphorylated Akt (Ser473) were elevated in U937/FN cells and the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 suppressed XIAP expression and restored the chemosensitivity to daunorubicin. Our findings suggested that adhesion-dependent activation of the PI3K/Akt/XIAP pathway may be one of the factors involved in the CAM-DR of U937 cells. Targeting this pathway may be a useful approach to improve the therapeutic responsiveness of leukaemia cells.

[Inhibitory effect of Rnai on AML1 -ETO fusion gene expression in leukemia cells].

OBJECTIVE: By inhibiting AML1 -ETO fusion gene expression in Kasumi-1 cells with RNAi, to investigate the changes in cell proliferation and cell cycle. METHODS: The small interference RNAs (siRNAs) specifically targeting the AML1 -ETO fusion gene were synthesized in vitro and transfected into Kasumi-1 cells by electroporation, the non-specific siRNAs transfected cells were taken as control. EGFP plasmid was transfected into Kasumi-1 cell and the transfection efficiency was detected by FCM. Inhibitory effect of siRNAs were detected by real-time RT-PCR and Western blots. Cell proliferation was measured by CCK-8 assay. DNA content was detected by PI assay. RESULTS: The transfection efficiency was 44.5%. The AML1 -ETO specific siRNAs inhibited AML1 -ETO expression at both mRNA and protein levels. The cell proliferation rate in siRNAs treated group was lower than that in control group 72 h after transfection [(47.90 +/- 0.02)% vs (66.90 +/- 0.08)% , P < 0.05]. The cell cycle was blocked at G1 phase 72 h after siRNAs treatment, the cell proportion in G1 phase being 38.3% and 31.6% in control group, while in G2/M phase being 1.8% and 2.4% respectively. CONCLUSIONS: The synthesized siRNAs can inhibit AML1 -ETO fusion gene expression. AML1 -ETO specific siRNA induced the decline of AML1 -ETO fusion protein in Kasumi-1 cell, and then caused the cell cycle blocked in G1 stage and eventually inhibited the cell proliferation.

[Distribution of abnormal cell clone with deletion of chromosome 20q in marrow cell lineages and apoptosis cells in myelodysplastic syndrome].

This study was aimed to investigate the distribution of abnormal clone in marrow cell lineages and apoptosis cells in myelodysplastic syndrome (MDS) with deletion of chromosome 20q. Monoclonal antibodies recognizing myeloid precursors (CD15), erythroid precursors (GPA), T cells (CD3(+)CD56(-)CD16(-)), B cells (CD19), NK cells (CD3(-)CD56(+)CD16(+)) were used to sort bone marrow cells in a MDS patient with del (20q) by fluorescence activated cell sorting (FACS). Annexin V-FITC and PI were used to sort bone marrow Annexin V(+)PI(-) and Annexin V(-)PI(-) cells by FACS. The sorted positive cells were detected by interphase dual-color fluorescence in situ hybridization (D-FISH) using a LSI D20S108 probe (Spectrum Orange) and a Telvysion TM 20p probe (Spectrum Green). FACS and FISH analysis were also performed on the samples from 4 cases with normal karyotype. The results showed that the proportions of MDS clone in the myeloid and erythroid precursors were 70.50% and 93.33% respectively, in the RAEB-1 patient with del (20q) and were obviously higher than that in control group (5.39% and 6.17%). The proportions of abnormal clone in T, B and NK cells were 3.23%, 4.32% and 5.77% respectively and were less than that in control group (5.76%, 4.85%, 6.36%). The percentage of apoptotic cells in the bone marrow nucleated cells was 16.09%. The proportions of MDS clone in Annexin V(+)PI(-) and Annexin V(-)PI(-) cells were 32.48% and 70.11%, respectively. It is concluded that most myeloid and erythroid precursors are originated from the abnormal clone in MDS with del (20q). A little part of apoptotic cells are derived from the abnormal clone.

[Detection of cytogenetic abnormalities involving chromosomes 5,7 and 8 in myelodysplastic syndromes with fluorescence in situ hybridization and its clinical significance].

OBJECTIVE: To identify the abnormal karyotypes by fluorescence in situ hybridization (FISH) and explore prognostic implications in patients with myelodysplastic syndromes (MDS). METHODS: FISH was used to detect the frequently occurring chromosome abnormalities (-5/5q, +8, -7/7q-) in 37 MDS cases. SPSS 11.5 software and correlation analysis were used to analyze the relativity among the abnormal chromosomes, the prognosis and the disease conversion in 37 MDS patients. RESULTS: Karyotype abnormalities were found in 21 (56.8%) of 37 cases, among which 6 (16.2%) were complex karyotypes, 9 (24.3%) +8, 2(5.4%) -5/5q-, 2(5.4%) -7/7q-. In the median time of follow-up of 12 months, 12 cases transformed into acute leukemia. Complex karyotypes were significantly associated with the poor prognosis and leukemia transformation. + 8 and -7/7q- abnormalities were correlated with the death. CONCLUSIONS: FISH was more sensitive than conventional cytogenetics for detecting mini-clonal abnormality. There are some differences in abnormal karyotypes between patients in China and the western countries. Multi-probes used in cytogenetic detections may predict the patient' s prognosis more accurately. The higher proportion of abnormal karyotypes the poorer prognosis.

[Drug resistance reversal of HL-60/ADR cells by simultaneous suppression of XIAP and MRP].

This study was purposed to explore the mechanisms of drug resistance of HL-60/ADR cells and to compare the reversal drug-resistance effects of antisense oligonucleotides (AS ODN) of XIAP (X-linked inhibitor of apoptosis protein) and AS ODNs of MRP (multidrug resistance-associated protein) by use alone or in combination. Reverse transcription-PCR and Western blot were applied to detect the expression of XIAP, BCL-2, MRP and MDR1 in mRNA and protein levels of HL-60 cells and HL-60/ADR cells, respectively. Fully phosphorothioated AS ODN of XIAP and MRP was delivered into HL-60/ADR cells with Lipofectamine 2000 in the form of liposome-ODN complexes alone or in combination. CCK-8 cell viability assay was used to determine the effect of AS ODN of XIAP and MRP used alone or in combination on the chemotherapy sensitivity of HL-60/ADR cells to daunorubicin (DNR). Reverse transcription-PCR and Western blot were applied to examine the changes of XIAP, MRP in mRNA and protein levels respectively. The results showed that MRP and XIAP were both significantly higher in HL-60/ADR cells than those in HL-60 cells. AS ODN of XIAP and MRP down-regulated the expression of XIAP and MRP in HL-60/ADR cells and increased the sensitivity of HL-60/ADR cells to DNR, respectively. AS ODN of XIAP + MRP did not enhance the inhibition expression of XIAP in HL-60/ADR cells but increased the sensitivity of HL-60/ADR cells to DNR significantly as compared with AS ODN of XIAP (P < 0.05). AS ODN of XIAP + MRP did not increase the concentration of DNR nor enhanced the inhibition expression of MRP in HL-60/ADR cells but increased the sensitivity of HL-60/ADR cells to DNR significantly (P < 0.05), as compared with AS ODN of MRP. It is concluded that both XIAP and MRP may be involved in the drug resistance mechanisms of HL-60/ADR cells. Drug-resistance of HL-60/ADR cells can be reversed significantly when antisense oligonucleotides of XIAP and MRP were used in combination.

[Role of XIAP in the drug resistance of HL-60 cells].

OBJECTIVE: To explore the role of X-linked inhibitor of apoptosis protein (XIAP) in the fibronectin (Fn)-adhesion mediated drug resistance of HL-60 cells. METHODS: Culture plates were coated with Fn and bovine serum albumin (BSA) (as control), respectively. Colorimetric CCK-8 assay was used to determine the effects of Fn on the cytotoxicity of DNR to HL-60 cells. Intracellular DNR accumulation was assayed with flow cytometry. Reverse transcription-PCR and Western blot were used to examine the mRNA expression and XIAP, bcl-2, MRP and mdr1 proteins, respectively. HL-60 cells were added to Fn coated Culture plates. The fully phosphorothioate antisense oligonucleotide (AS-ODNs) and the control ODNs of XIAP were delivered into HL-60 cells in the form of liposome-ODN complexes. IC(50) was calculated by linear regression of survival percent versus drug concentration. RESULTS: HL-60 cells adhered to Fn-coated plates had a significant survival advantage over those grown on BSA coated plates and in suspension when exposed to DNR, the IC(50) of Fn group being significantly higher than that of BSA group and suspension group (0.526 micromol/L vs 0.132 micromol/L, 0.123 micromol/L, respectively, P < 0.05). XIAP was up-regulated significantly in Fn group compared with BSA group and suspension group (P < 0.05), whereas there was no difference in the expressions of bcl-2, MRP and mdr1 among the three groups (P > 0.05). The intracellular concentration of DNR in Fn-adhered HL-60 cells was similar to that in BSA group and suspension group (P < 0.05). AS-ODNs of XIAP down-regulated the XIAP expression in Fn-adhered HL-60 cells. In addition, AS-ODNs sensitized HL-60 cells to the cytotoxic effects of DNR. CONCLUSION: The increased XIAP protein level contributes to the drug resistance induced by adhesion to Fn. AS-ODNs of XIAP might reverse the drug resistance.