non-DS Acute Myeloid Leukemia Research Articles

Treatment strategy for myeloid leukemia with Down syndrome

Myeloid leukemia with Down syndrome (ML-DS) demonstrates unique characteristics such as the predominance of FAB M7, an age predilection during the first 4 years of life, and higher sensitivity to chemotherapeutic agents, which translate into a good treatment response as well as increased treatment-related toxicities. Consequently, patients with ML-DS have traditionally been treated separately from non-DS acute myeloid leukemia (AML) children. The 3-year event-free survival rates in recent clinical studies in the Western countries and Japan are all more than 85%. In Japan, two studies (AML-D05 and AML-D11) were conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group. The efficacy of risk-oriented therapy according to morphological response was evaluated in the AML-D05 study. Despite that a dose reduction of chemotherapeutic agents could be performed in many cases, the overall outcome was comparable with those of previous Japanese studies. In the subsequent AML-D11 study, the role of minimal residual disease (MRD) was evaluated. MRD by flow cytometry (FCM) and targeted deep sequencing of GATA1 following the initial induction therapy were significant prognostic factors for predicting relapse. Dose modification according to the end-of-induction FCM-MRD is being attempted in the ongoing JCCG AML-D16 study.

Monitoring minimal residual disease in pediatric acute myeloid leukemia

The event-free survival rate for childhood acute myeloid leukemia (AML) is approaching 60%, owing to the use of intensive chemotherapy, optimal indication of hematopoietic stem cell transplantation, and advances in supportive care. For further improvement, the development of more definitive risk stratification system and introduction of more effective treatment options are necessary. Recently, much attention has been drawn on minimal residual disease (MRD) that is considered a strong prognostic factor for children with AML. Recent studies from the United States and Europe have shown the prognostic impact of FCM-based MRD detection and it is already used for risk stratification in modern AML protocols. Myeloid leukemia in Down's syndrome (ML-DS) has unique characteristics, and ML-DS children are recently being treated separately from non-DS AML children with less intensive treatment. It has been shown that relapsed and refractory cases of ML-DS are difficult to treat; however, no universal prognostic factor has been found yet. In order to determine accurate methods for identifying a subgroup with poor prognosis, an attempt to analyze the role of MRD had been examined in the JPLSG AML-D11 study. In this study, the MRD by FCM and targeted deep sequencing for GATA1 after initial induction therapy were significant prognosis factors for predicting relapse.

Infections in children with down syndrome and acute myeloid leukemia: a report from the Canadian infections in AML research group

BackgroundChildren with Down syndrome (DS) are at high risk of infectious toxicity when treated with acute lymphoblastic leukemia chemotherapy protocols optimized in children without DS. Our objective was to determine if children with DS and acute myeloid leukemia (AML) have a different risk of infection when treated with chemotherapy protocols developed for children with DS compared to AML treatment protocols developed for children without DS.MethodsWe conducted a retrospective, population-based cohort study that included DS children ≤ 18 years of age with de novo, non-M3 AML diagnosed between January 1995 and December 2004, and treated at 15 Canadian centers. Patients were monitored for infection from initiation of AML treatment until recovery from the last cycle of chemotherapy, conditioning for hematopoietic stem cell transplantation, relapse, persistent disease or death (whichever occurred first). Trained research associates abstracted all information from each site.ResultsThere were 31 children with DS included; median age was 1.7 (range 0.1-11.1) years. Eleven were treated according to a DS-specific protocol while 20 were treated with non-DS specific protocols. A total of 157 courses of chemotherapy were delivered. Microbiologically documented sterile site infection occurred in 11.9% and 14.3% of DS-specific and non-DS specific AML treatment courses respectively. Sepsis was rare and there were no infection-related deaths. In multiple regression, treatment with a DS-specific protocol was independently associated with a reduction in microbiologically documented sterile site infection (adjusted odds ratio (OR) 0.65, 95% confidence interval (CI) 0.42-0.99; P = 0.044), and clinically documented infection (adjusted OR 0.36, 95% CI 0.14-0.91; P = 0.031) but not bacteremia (adjusted OR 0.73, 95% CI 0.44-1.22; P = 0.231).ConclusionsOur study suggests that children with DS do not experience excessive infectious toxicity during treatment for AML compared to children without DS. Incorporation of DS-specific AML treatment protocols is associated with a more favorable infection profile for children with DS-AML.

Targeting The Wee1 Kinase With MK-1775 For Treatment Of Acute Myeloid Leukemia In The Down Syndrome Population

Approximately one seventh of pediatric acute myeloid leukemia (AML) patients also have Down Syndrome (DS), or constitutional trisomy 21. DS AML is considered to be a unique disease from non-DS AML, due in part to a high prevalence of somatic GATA1 mutations and a megakaryocytic phenotype (AMKL). In contrast to the non-DS population, DS AML is generally associated with a very favorable prognosis. However, treatment of this disease is not without complications. Adverse drug effects are significant within this population, especially with up to half of patients possessing congenital heart abnormalities. Furthermore, for those patients who suffer either an induction failure or relapse, prognoses are dismal (Taga T. et al., Blood, 120: 1810-1815, 2012) including the outcomes after stem cell transplant (Hitzler JK. et al., Biol Blood Marrow Transplant, 19:893-897, 2013). Therefore, less toxic and more efficacious therapies are needed for this population.Recently, chemotherapeutic targeting of cell cycle checkpoints has emerged as an exciting possibility, with many clinical trials underway. The wee1 kinase has been identified as a potential target in many malignancies, including leukemia. It is responsible for inhibiting CDK1 and CDK2 by adding phosphate groups at amino acid residue tyrosine 15 (Y15), which is necessary for subsequent checkpoint activation by checkpoint proteins (e.g. CHK1). The development of a wee1-specific inhibitor, MK-1775, has allowed investigations into its use alone or in combination with classical chemotherapeutics as treatment for many types of cancer, with favorable results thus far. However, there is some controversy with regards to the mechanism by which it enhances cell death.In this preclinical work we used DS AML cell lines to investigate the potential use of MK-1775, both alone and in combination with cytarabine, to improve outcomes in DS AML patients. The two cell lines, CMK and CMY, were derived from DS AMKL patients and both harbor GATA1 mutations. CMK was derived from a patient who relapsed after initial treatment and CMY was derived from a patient who experienced an induction failure. The CMY line displays significant resistance to multiple different classes of chemotherapy drugs including nucleoside agents (e.g. cytarabine) and anthracyclines. We found that MK-1775 alone was able to cause growth inhibition and apoptosis at clinically relevant doses in both cell lines, independent of sensitivity to cytarabine or other agents. This effect was greatly enhanced by the addition of cytarabine. Addition of 250nM MK-1775 was able to reduce the cytarabine IC50 9- and 45-fold in CMK and CMY cells, respectively. Combination indices (CI) for this combination ranged from 0.66-0.95 and 0.50-0.94 in CMK and CMY, respectively.The combination of MK-1775 and cytarabine was able to synergistically induce apoptosis as measured by annexinV/propidium iodide (PI) staining. Addition of MK-1775 was able to decrease inhibitory CDK1 and CDK2 Y15 phosphorylation induced by cytarabine treatment. Interestingly, treatment with MK-1775 increased DNA damage induced by cytarabine as measured by γH2AX signal on western blots. Furthermore, this damage was induced primarily in S-phase, as measured by γH2AX/PI dual-staining and flow-cytometry. Finally, to aid with the clinical translation of this work, the dose- and time-dependency of MK-1775 treatment on CDK1 and CDK2 Y15 phosphorylation was determined. Briefly, even low doses (100nM) of MK-1775 were able to reduce CDK1 and CDK2 Y15 phosphorylation after only four hours. However, this inhibitory phosphorylation was able to return after only 1 hour, suggesting that treatment with MK-1775 must be continued during cytarabine therapy.In conclusion, these data support the combination of MK-1775 and cytarabine for the treatment of DS AML, including possible relapsed/refractory cases which have a very poor prognosis. Combining MK-1775 with cytarabine was able to synergistically induce apoptosis in both cell lines, possibly by increasing DNA damage and decreasing inhibition of CDK1 and CDK2. Disclosures:No relevant conflicts of interest to declare.

Blast cell deficiency of CD11a as a marker of acute megakaryoblastic leukemia and transient myeloproliferative disease in children with and without Down syndrome

The classification of acute myeloid leukemia (AML) FAB subtype M7 relies on immunophenotypic assessment. CD41 is expressed throughout all stages of maturation of megakaryocytes and has therefore been described as a specific blast cell marker in AML M7 as well as in transient myeloproliferative disease (TMD) of patients with Down syndrome (DS). However, technical difficulties underlie the need for new markers for these entities. We evaluated the expression of human lymphocyte function-associated antigen 1 (CD11a) in a large cohort of pediatric AML and TMD patients (n = 91) of the Austrian AML-BFM 98 and 2004 studies. We found a consistent deficiency of CD11a as assessed by mean fluorescence intensity in all patients with non-DS AML M7 (n = 8) and M6 (n = 1), all cases of classical DS-AML (n = 12) as well as TMD (n = 15) that was statistically significant in comparison to non-DS AML M0-M5 patients (n = 55; P < 0.001, sensitivity 100%). Only three of 55 Non-DS M0-5 patients were CD11a deficient (specificity 95%). Monocytic leukemias (M4/5) and normal monocytes typically showed a high CD11a expression, FAB types M1/2 and normal neutrophils an intermediate expression level, while all M3 leukemias were rather low in CD11a expression. We conclude, that deficiency of CD11a expression should be added to the diagnostic criteria of AML-M7, classical DS-AML and TMD.

Outcome of Transplantation for Acute Leukemia in Down Syndrome

AbstractAbstract 1991Children with Down syndrome (DS) have a 10-to 20-fold increased incidence of acute lymphoblastic (ALL) and acute myeloid leukemia (AML) compared to the overall pediatric population. Available data on HCT in children with DS are scarce, suggest unsatisfactory outcomes and are conflicting as far as causes of treatment failure are concerned. All but one case series identified treatment-related mortality (TRM) as the major barrier to success. To better understand factors associated with HCT-outcomes we studied 28 patients with DS-AML and 27 patients with DS-ALL, the largest cohort of DS patients with acute leukemia to date. All transplants occurred in 2000–2009. Transplantations occurred in second remission for 43% of patients with DS-AML and 52%, with DS-ALL. With a median follow-up of 3-years disease-free survival (DFS) was 14% for DS-AML and 24% for DS-ALL. Leukemia recurrence was the predominant cause of treatment failure in the current analysis, 61% for DS-AML and 54% for DS-ALL, both substantially higher than expected for pediatric non-DS AML or ALL. In the subset of patients with DS-AML, we conducted a matched pair analysis. Cases (DS-AML) were matched to non-DS AML controls for age, disease status, cytogenetic risk group, donor-source, donor-recipient HLA match and graft source. The results of multivariate analysis, adjusted for interval from diagnosis to transplantation are shown below. Relapse risk was significantly higher in DS-AML than non DS-AML (62% vs. 37%; p<0.001). TRM was also higher in patients with DS-AML compared to non DS-AML (24% vs. 15%, p=0.04). Consequently, 3-year DFS was significantly lower for DS-AML compared to non DS-AML (14% vs. 48%, p<0.001). The corresponding probabilities of overall survival (OS) were 21% and 52% (p<0.001). Interval from diagnosis to transplant was significantly associated with OS; transplantation that occurred within 12 months from diagnosis was associated with higher mortality (hazard ratio 1.90, p=0.03). Interval between diagnosis and transplantation was not significantly associated with relapse (hazard ratio 1.42, p=0.27) or TRM (hazard ratio 2.17, p=0.15). In conclusion, after adjusting for known risk factors, leukemic relapse and TRM contribute to treatment failure after HCT in the recent treatment era. Cooperative group trials appear warranted that improve the selection of HCT candidates, optimize transplant-conditioning regimen and explore novel therapeutic approaches to improve the depth of remission prior to HCT in these children.TableHazard Ratio 95% confidence intervalP-valueTransplant-related mortalityDS-AML vs. non DS-AML2.52 (1.06–6.00)0.04Leukemia recurrenceDS-AML vs. non DS-AML2.84 (1.75–4.59)<0.001Treatment failure (death or relapse; inverse of DFS)DS-AML vs. non DS-AML2.75 (1.75–4.31)<0.001Overall mortalityDS-AML vs. non DS-AML2.86 (1.77–4.64)<0.001 Disclosures:No relevant conflicts of interest to declare.

High Frequency of Copy Number Variations in Myeloid Leukemia of Down Syndrome.

Abstract 3242Poster Board III-179Pediatric acute myeloid leukemia (AML) is a heterogenous disease, with current therapy resulting in cure rates of approximately 60%. The prognosis depends on cytogenetics and early response to therapy. Recently, Radtke et al. (PNAS 2009) reported that (by using single-nucleotide-polymorphism microarrays and candidate resequencing) de novo AML is characterized by a low frequency of copy number variations (CNVs), with a mean of 2.38 somatic CNVs per case. This is in contrast to pediatric acute lymphoblastic leukemia (ALL), with an average of 6 per case (Mullighan et al, Leukemia 2009). The only exception in AML was acute megakaryocytic leukaemia (AMKL, n=9 cases), which is characterized by a high number of CNVs (average of 9.33). Of these 9 AMKL cases, only one patient had a GATA1-mutation, typical of Myeloid Leukemia in Down syndrome (ML-DS). Most ML-DS cases are classified as AMKL, and can be preceded by a pre-leukemic clone in newborns (transient leukaemia- TL), which in approximately 80% resolves spontaneously. Treatment outcome for non Down syndrome AMKL is poor, whereas Down AMKL has a good prognosis.We performed array-based comparative genomic hybridization (Array-CGH) to detect copy number variations (CNV) in Down syndrome related leukemias, with the aim to study whether progression from TL to ML-DS is associated with clonal evolution. We also compared the data obtained with array-CGH from DS patients with two other subgroups of non-DS pediatric AML, i.e. MLL-rearranged AML, and cytogenetically normal AML (CN-AML). This may provide insight in differences in genomic stability between these subgroups. For this analysis, 66 MLL-rearranged AML, 41 CN-AML, 7 TL and 14 ML-DS samples taken at initial diagnosis were available. TL and ML-DS samples were unpaired. Genomic aberrations were scored as a minimum of three (44K arrays, Agilent) and as a minimum of five (105K arrays, Agilent) adjacent probes deviating beyond the threshold of ∼0.5. Results are given in table 1 and 2 below.Copy number variations in different subgroups of pediatric AML in percentages of the total number of samplesSubgroupAmplificationDeletionTotal CNVMLL-rearranged AML n = 6638%55%71%CN-AML n =417%34%37%TL n = 729%57%57%ML-DS n =1464%93%100%Copy number variations in different subgroups of pediatric AML, expressed per caseSubgroupAmplificationDeletionTotal CNVMLL-rearranged AML n = 660.670.641.36CN-AML n =410.070.460.54TL n = 70.432.002.43ML-DS n =141.862.934.79ML-DS patients had a significantly higher frequency of samples with CNVs compared to TL-patients (100% vs. 57%; p=0.026). Most amplifications were (sub)chromosomal (e.g. extra copies of chromosome 8, 11 and 21), whereas the deletions were mostly focal. Except for the (sub)chromosomal amplifications, the other aberrations were mostly found in single cases. Overall, deletions were more common than amplifications. When we analyzed the number of CNVs per case, ML-DS patients had a trend to have a higher number of CNVs per patient (p=0.06) than TL-patients. When the TL and ML-DS patients were taken together and compared to the other non-DS AML-subgroups taken together, there was a significantly higher number of patients with copy variations (86% vs. 58%; p=0.013) in the Down leukemia group. Also, the number of CNV per case was significantly higher in the Down syndrome patients compared to the non-DS AML subgroups (p=< 0.001).In conclusion, we observed significantly less patients with CNVs and less CNVs per patient in MLL- rearranged and CN-AML compared to Down syndrome related leukemia. This suggests that the Down syndrome related leukemias are more genetically unstable when compared with their non-DS controls. Our data are consistent with the findings in AMKL in non-Down syndrome patients as reported by Radtke et al, and may suggest that genomic instability is a general phenomenon of AMKL. This is noteworthy because ML-DS and non-DS AMKL differ in various other aspects. The mechanisms behind the genetically more instable character of the AMKL subgroup is still unclear, and requires further study. Within the Down syndrome patients, there was a statistically significant increase in patients with CNVs in ML-DS compared to TL, and a trend for more CNVs per patient, suggestive of clonal evolution. DisclosuresNo relevant conflicts of interest to declare.

Cardiomyopathy in Children With Down Syndrome Treated for Acute Myeloid Leukemia: A Report From the Children's Oncology Group Study POG 9421

To determine the outcomes, with particular attention to toxicity, of children with Down syndrome (DS) and acute myeloid leukemia (AML) treated on Pediatric Oncology Group (POG) protocol 9421. Children with DS and newly diagnosed AML (n = 57) were prospectively enrolled onto the standard-therapy arm of POG 9421 and were administered five cycles of chemotherapy, which included daunorubicin 135 mg/m(2) and mitoxantrone 80 mg/m(2). Outcomes and toxicity were evaluated prospectively and were compared with the non-DS-AML cohort (n = 565). A retrospective chart review was performed to identify adverse cardiac events. In the DS-AML group, 54 patients (94.7%) entered remission. One experienced induction failure and two died. Of the 54 who entered remission, three relapsed and six died as a result of other causes. The remission induction rate was similar in the non-DS-French-American-British (FAB) M7 (91.7%) and non-DS-non-M7 (89.3%) groups. The 5-year overall survival was significantly better in the DS-AML group (78.6%) than in the non-DS-M7 (36.3%) or the non-DS-non-M7 (51.8%) groups (P < .001). No age-related difference in 5-year, event-free survival was seen between patients younger than 2 years (75.8%) and those aged 2 to 4 years (78.3%). Symptomatic cardiomyopathy developed in 10 patients (17.5%) with DS-AML during or soon after completion of treatment; three died as a result of congestive heart failure. The POG 9421 treatment regimen was highly effective in both remission induction and disease-free survival for patients with DS-AML. However, there was a high incidence of cardiomyopathy, which supports current strategies for dose reduction of anthracyclines in this patient population.

Excessive Cardiotoxicity Despite Excellent Leukemia-Free Survival for Pediatric Patients with Down Syndrome (DS) and Acute Myeloid Leukemia (AML): Results from POG (Pediatric Oncology Group) Protocol 9421.

INTRODUCTION: Children with DS and AML have a superior response to chemotherapy and improved survival compared to non-DS AML patients. However, DS patients have been shown to have excessive treatment-related mortality. We report the outcomes of DS-AML patients treated on POG protocol 9421 with particular attention to cardiotoxicity.RESULTS: Fifty-seven DS-AML patients were enrolled. Median age was 20 months (range 1–40 months) including 8 (14%) infants < 12 months, 30 (52.6%) children ≥12months and ≤ 24 months, 16 (28.1%) children >24months and ≤ 36 months, and 3 (5.3%) children > 36 months. 45 patients (78.9%) had FAB-M7 morphology. There was one induction failure and 2 early deaths with the remainder of the patients (54/57 = 94.7%) achieving first remission (CR1). Early deaths included one patient who presented with meningococcemia at the time of diagnosis of AML and was in critical condition prior to induction. The second patient had unrepaired tetralogy of Fallot (TOF) and died during induction of presumed sepsis precipitating a fatal TOF cyanotic event. CR1 rate was 8 of 8 (100%) for age ≤ 12 months, 29 of 30 (97%) for age > 12 mos and ≤ 24mos, 15 of 16 (93.8%) for age >24 mos and ≤ 36 mos, and 2 of 3 (66%) for age > 36months.Of the 54 patients achieving CR1, 3 relapsed. Two died of disease and one patient underwent allogeneic bone marrow transplant and died of complications. There have been no other relapses with follow-up ranging from 2–10 years. One patient with partially repaired AV canal was removed from study after induction 1 due to congestive heart failure (CHF) and pulmonary hemorrhage and remains alive in CR1 9 years later. There were 6 additional deaths unrelated to leukemia. Two patients died following consolidation 2, one with RSV pneumonia and the other with CHF. Four patients died following completion of treatment: two of unknown causes, one due to CHF, and one due to “respiratory illness."Review of the data reveals a concerning incidence of cardiotoxicity. Nineteen (33%) patients had documented structural cardiac disease. The majority had either repaired cardiac disease or isolated ASD or VSD which was thought to be clinically insignificant. All patients had documentation of adequate cardiac function by echocardiography prior to the start of treatment. Cumulative anthracycline exposure on this protocol was high, including 135mg/m2 of daunorubicin and 80mg/m2 of mitoxantrone. Twelve of 57 patients (21%) had documented CHF requiring chronic diuretics and/or inotropes with diminished fractional shortening on echocardiogram; four patients died. Eight of these 12 patients had prior cardiac disease although 4 had either functionally insignificant ASD or repaired VSD. Dilated cardiomyopathy developed during or soon after completion of treatment in all patients.CONCLUSION: In summary, this treatment regimen for DS-AML was highly effective in both remission induction and long-term leukemia-free survival. However, there was a high incidence of dilated cardiomyopathy, which lends support to current strategies for dose reduction of anthracyclines in this patient population. Additional follow-up data on these children is currently being collected to further delineate the burden of long-term cardiac dysfunction among survivors.

The role of cytidine deaminase and GATA1 mutations in the increased cytosine arabinoside sensitivity of Down syndrome myeloblasts and leukemia cell lines.

Myeloblasts from Down syndrome (DS) children with acute myeloid leukemia (AML) are significantly more sensitive in vitro to 1-beta-D-arabinofuranosylcytosine (ara-C) and generate higher 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP) than non-DS AML myeloblasts. Semiquantitative reverse transcription-PCR analyses demonstrated that transcripts for cytidine deaminase (CDA) were 2.7-fold lower in DS than for non-DS myeloblasts. In contrast, transcripts of cystathionine-beta-synthase and deoxycytidine kinase were a median 12.5- and 2.6-fold higher in DS compared with non-DS myeloblasts. The ratio of deoxycytidine kinase/CDA transcripts significantly correlated with ara-C sensitivities and ara-CTP generation. In clinically relevant AML cell line models, high cystathionine-beta-synthase transcripts in DS CMK cells were accompanied by 10-fold greater ara-C sensitivity and 2.4-fold higher levels of ara-CTP compared with non-DS CMS cells. Overexpression of CDA in non-DS THP-1 cells was associated with a 100-fold decreased ara-C sensitivity and 40-fold decreased ara-CTP generation. THP-1 cells secreted CDA into the incubation media and converted extracellular ara-C completely to 1-beta-D-arabinofuranosyluracil within 30 min. Rapid amplification of 5'-cDNA ends (5'-RACE) and reverse transcription-PCR assays identified short- (sf) and long-form (lf) CDA transcripts in THP-1 cells with different 5' untranslated regions and translational start sites; however, only the latter resulted in the active CDA. Although 5' flanking sequences for both CDA transcripts exhibited promoter activity in reporter gene assays, activity for the CDAlf was low. The presence of several GATA1 binding sites in the CDAsf promoter and the uniform detection of GATA1 mutations in DS megakaryocytic leukemia suggested the potential role of GATA1 in regulating CDA transcription and the CDAsf promoter acting as an enhancer. Transfection of GATA1 into Drosophila Mel-2 cells stimulated the CDAlf promoter in a dose-dependent fashion. Additional identification of the mechanisms of differential expression of genes encoding enzymes involved in ara-C metabolism between DS and non-DS myeloblasts may lead to improvements in AML therapy.

Transcriptional regulation of the cystathionine-β-synthase gene in Down syndrome and non–Down syndrome megakaryocytic leukemia cell lines

Children with Down syndrome (DS) with acute myeloid leukemia (AML) have significantly higher event-free survival rates compared to those with non-DS AML, linked to greater cytosine arabinoside (ara-C) sensitivity and higher transcript levels of the chromosome 21-localized gene, cystathionine-beta-synthase (CBS), in DS myeloblasts. In this study, we examined the transcriptional regulation of the CBS gene in the DS megakaryocytic leukemia (AMkL) cell line, CMK, characterized by significantly higher CBS transcripts compared with the non-DS AMkL cell line, CMS. Rapid amplification of 5'-cDNA ends (5'-RACE) analysis demonstrated exclusive use of the CBS -1b promoter in the cell lines, and transient transfections with the full-length CBS -1b luciferase reporter gene construct showed 40-fold greater promoter activity in the CMK than CMS cells. Electrophoretic mobility shift assays showed enhanced binding of the transcription factors Sp1/Sp3 to 2 GC/GT-box elements (GC-f and GT-d) in the upstream regions of the CBS -1b promoter in CMK nuclear extracts and undetectable binding in CMS cells. Mutation of the GC-f- or GT-d-binding site resulted in an approximately 90% decrease of the CBS -1b promoter activity in transient transfections of CMK cells. Chromatin immunoprecipitation assays confirmed in vivo binding of Sp3, USF-1, and nuclear factor YA (NF-YA) to the CBS -1b promoter region in chromatin extracts of CMK and CMS cells. Decreased binding of Sp1/Sp3 in CMK nuclear extracts following treatment with calf alkaline phosphatase suggested a role for phosphorylation of Sp1/Sp3 in regulating CBS promoter activity and in the differential CBS expression between CMK and CMS cells. The results of this study with clinically relevant cell line models suggest potential mechanisms for disparate patterns of CBS gene expression in DS and non-DS myeloblasts and may, in part, explain the greater sensitivity to chemotherapy shown by patients with DS AML.

Different drug sensitivity profiles of acute myeloid and lymphoblastic leukemia and normal peripheral blood mononuclear cells in children with and without Down syndrome

Children with Down syndrome (DS) have an increased risk for leukemia. The prognosis for DS acute myeloid leukemia (AML) is better than for non-DS AML, but the clinical outcome of DS acute lymphoblastic leukemia (ALL) is equal to that of non-DS ALL. Differences in prognosis may reflect differences in cellular drug resistance. In vitro drug resistance profiles were successfully investigated on leukemic cells from 13 patients with DS AML and 9 patients with DS ALL and were compared with reference data from 151 non-DS AML and 430 non-DS B-cell precursor (BCP) ALL. DS AML cells were significantly more sensitive to cytarabine (median, 12-fold), the anthracyclines (2-7-fold), mitoxantrone (9-fold), amsacrine (16-fold), etoposide (20-fold), 6-thioguanine (3-fold), busulfan (5-fold), vincristine (23-fold), and prednisolone (more than 1.1-fold), than non-DS AML cells. Compared with DS ALL, DS AML cells were significantly more sensitive to cytarabine only (21-fold). After short-term exposure to methotrexate, DS AML cells were 21-fold more resistant than non-DS AML cells, but no difference was observed after continuous exposure. DS ALL cells and non-DS BCP-ALL cells were equally sensitive to all drugs, including methotrexate. Normal peripheral blood mononuclear cells from DS and non-DS children without leukemia showed highly resistant drug profiles. It was concluded that the better prognosis of DS AML might, at least partially, be explained by a specific, relatively sensitive drug-resistance profile, reflecting the unique biology of this disease. (Blood. 2002;99:245-251)