Disturbed CXCR4/CXCL12 axis in paediatric precursor B-cell acute lymphoblastic leukaemia

Malignant cells infiltrating the bone marrow (BM) interfere with normal cellular behaviour of supporting cells, thereby creating a malignant niche. We found that CXCR4-receptor expression was increased in paediatric precursor B-cell acute lymphoblastic leukaemia (BCP-ALL) cells compared with normal mononuclear haematopoietic cells (P < 0·0001). Furthermore, high CXCR4-expression correlated with an unfavourable outcome in BCP-ALL (5-year cumulative incidence of relapse ± standard error: 38·4% ± 6·9% in CXCR4-high versus 12% ± 4·6% in CXCR4-low expressing cases, P < 0·0001). Interestingly, BM levels of the CXCR4-ligand (CXCL12) were 2·7-fold lower (P = 0·005) in diagnostic BCP-ALL samples compared with non-leukaemic controls. Induction chemotherapy restored CXCL12 levels to normal. Blocking the CXCR4-receptor with Plerixafor showed that the lower CXCL12 serum levels at diagnosis could not be explained by consumption by the leukaemic cells, nor did we observe an altered CXCL12-production capacity of BM-mesenchymal stromal cells (BM-MSC) at this time-point. We rather observed that a very high density of leukaemic cells negatively affected CXCL12-production by the BM-MSC while stimulating the secretion levels of granulocyte colony-stimulating factor (G-CSF). These results suggest that highly proliferative leukaemic cells are able to down-regulate secretion of cytokines involved in homing (CXCL12), while simultaneously up-regulating those involved in haematopoietic mobilization (G-CSF). Therefore, interference with the CXCR4/CXCL12 axis may be an effective way to mobilize BCP-ALL cells.

Glucocorticoid sensitisation in Mixed Lineage Leukaemia-rearranged acute lymphoblastic leukaemia by the pan-BCL-2 family inhibitors gossypol and AT-101

AIM OF THE STUDY

Resistance to glucocorticoids (GCs) remains a major problem in the treatment of infants with acute lymphoblastic leukaemia (ALL) carrying Mixed Lineage Leukaemia (MLL) translocations. Despite intensive research, the mechanism(s) underlying GC resistance remain poorly understood. Recent studies suggested an important role for the pro-survival BCL-2 family member MCL1 in GC resistance in MLL-rearranged ALL.

METHODS

We exposed GC-resistant MLL-rearranged SEMK2 cells to potent MCL1-inhibiting agents, including gossypol, AT-101, rapamycin, SU9516 and obatoclax (GX15-070) and determined GC sensitisation using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assays. Using Western blotting we analysed the protein expression of most BCL-2 family members in MLL-rearranged SEMK2 cells after treatment with potent MCL-1 inhibiting agents.

RESULTS

Only gossypol and its synthetic analogue AT-101 induced GC sensitivity in MLL-rearranged ALL cells. Remarkably, the GC-sensitising effects of gossypol and AT-101 appeared not to be mediated by down-regulation MCL1 or other anti-apoptotic BCL-2 family members, but rather involved up-regulation of multiple pro-apoptotic BCL-2 family members, in particular that of BIM and BID.

CONCLUDING REMARKS

In conclusion, gossypol and AT-101 induce GC sensitivity in MLL-rearranged ALL cells, most likely mediated by the activation of BID and BIM without the necessity to down-regulate anti-apoptotic BCL-2 family members like MCL1. Hence, co-administration of either gossypol or AT-101 during GC treatment of GC-resistant MLL-rearranged ALL patients may overcome GC resistance and improve prognosis in this high-risk childhood leukaemia.

Folates provoke cellular efflux and drug resistance of substrates of the multidrug resistance protein 1 (MRP1)

Cellular folate concentration was earlier reported to be a critical factor in the activity and expression of the multidrug resistance protein MRP1 (ABCC1). Since MRP1 mediates resistance to a variety of therapeutic drugs, we investigated whether the cellular folate concentration influences the MRP1-mediated cellular resistance against drugs. As a model system, we used the human ovarian carcinoma cell line 2008wt, and its stably MRP1/ABCC1-transfected subline 2008/MRP1. These cell types have a moderate and high expression of MRP1, respectively. In folate-deprived 2008/MRP1 cells, the MRP1-mediated efflux of its model substrate calcein decreased to ~55 % of the initial efflux rate under folate-rich conditions. In 2008wt cells, only a small decrease in efflux was observed. Folate depletion for 5-10 days markedly increased (~500 %) cellular steady-state accumulation of calcein in 2008/MRP1 cells and moderately in 2008wt cells. A subsequent short (24 h) exposure to 2.3 μM L-leucovorin decreased calcein levels again in MRP1-overexpressing cells. Folate deprivation markedly increased growth inhibitory effects of the established MRP1 substrates daunorubicin (~twofold), doxorubicin (~fivefold), and methotrexate (~83-fold) in MRP1-overexpressing cells, proportional to MRP1 expression. In conclusion, this study demonstrates that increased cellular folate concentrations induce MRP1/ABCC1-related drug efflux and drug resistance. These results have important implications in the understanding of the role of MRP1 and its homologs in clinical drug resistance.

Bone mineral density at diagnosis determines fracture rate in children with acute lymphoblastic leukemia treated according to the DCOG-ALL9 protocol

PURPOSE

To elucidate incidence and risk factors of bone mineral density and fracture risk in children with Acute Lymphoblastic Leukemia (ALL).

METHODS

Prospectively, cumulative fracture incidence, calculated from diagnosis until one year after cessation of treatment, was assessed in 672 patients. This fracture incidence was compared between subgroups of treatment stratification and age subgroups (Log-Rank test). Serial measurements of bone mineral density of the lumbar spine (BMDLS) were performed in 399 ALL patients using dual energy X-ray absorptiometry. We evaluated risk factors for a low BMD (multivariate regression analysis). Osteoporosis was defined as a BMDLS≤-2 SDS combined with clinical significant fractures.

RESULTS

The 3-year cumulative fracture incidence was 17.8%. At diagnosis, mean BMDLS of ALL patients was lower than of healthy peers (mean BMDLS=-1.10 SDS, P<0.001), and remained lower during/after treatment (8months: BMDLS=-1.10 SDS, P<0.001; 24months: BMDLS=-1.27 SDS, P<0.001; 36months: BMDLS=-0.95 SDS, P<0.001). Younger age, lower weight and B-cell-immunophenotype were associated with a lower BMDLS at diagnosis. After correction for weight, height, gender and immunophenotype, stratification to the high risk (HR)-protocol arm and older age lead to a larger decline of BMDLS (HR group: β=-0.52, P<0.01; age: β=-0.16, P<0.001). Cumulative fracture incidences were not different between ALL risk groups and age groups. Patients with fractures had a lower BMDLS during treatment than those without fractures. Treatment-related bone loss was similar in patients with and without fractures (respectively: ΔBMDLS=-0.36 SDS and ΔBMDLS=-0.12 SDS; interaction group time, P=0.30). Twenty of the 399 patients (5%) met the criteria of osteoporosis.

CONCLUSION

Low values of BMDLS at diagnosis and during treatment, rather than the treatment-related decline of BMDLS, determine the increased fracture risk of 17.8% in children with ALL.

[Chronic renal insufficiency following childhood cancer]

Modern intensive treatment modalities have led to an increasing number of survivors of childhood cancer, who are at risk for developing long-term sequelae. Since decline of renal function can develop subclinically, adequate surveillance is required for survivors previously treated with nephrotoxic treatment modalities. We describe a 34-year-old man, who had been treated for nephroblastoma (stage I) at the age of 5 years and who regularly visited the adult late-effects clinic for survivors of childhood cancer. Twenty years after his treatment for nephroblastoma glomerular function started to decline and progressive chronic kidney disease (CKD) stage 3 developed. It is important to recognise that survivors of childhood cancer can be at risk of developing long-term effects, including impaired renal function. Apart from regular surveillance by expert medical specialists dedicated to childhood cancer survivor care, more intensive communication with primary health care physicians is necessary to improve awareness of these issues in the growing cohort of childhood cancer survivors.

The synergism of MCL1 and glycolysis on pediatric acute lymphoblastic leukemia cell survival and prednisolone resistance

In vitro and in vivo resistance to prednisolone are predictive for an adverse prognosis in pediatric precursor B-acute lymphoblastic leukemia. Causes of resistance are still poorly understood. In this study, we observed that prednisolone exposure of prednisolone-sensitive patients' leukemic cells decreased anti-apoptotic MCL1 protein levels by 2.9-fold, while MCL1 protein expression in prednisolone-resistant leukemic patients' cells was unaffected (P<0.01). Locked nucleic acid oligonucleotides directed against MCL1 reduced MCL1 protein levels by 82±16% (P<0.05) in leukemic cells, decreased proliferation by 9-fold and sensitized to prednisolone up to 80.8-fold, compared to a non-silencing-control locked nucleic acid (P<0.05). Remarkably, we discovered that MCL1-silencing up-regulated the glucose consumption of leukemic cells by 2.5-fold (P<0.05), suggesting a potential rescue mechanism mediated by glycolysis. Targeting glycolysis by 2-deoxyglucose synergistically inhibited leukemic survival by 23.2-fold in MCL1-silenced cells (P<0.05). Moreover, 2-deoxyglucose and MCL1 locked nucleic acid concomitantly sensitized leukemic cells to prednisolone compared to MCL1 locked nucleic acid or 2-deoxyglucose alone (P<0.05). In conclusion, these results indicate the need to target both MCL1 and glycolysis simultaneously to inhibit leukemic survival and sensitize acute leukemia patients towards prednisolone.

Final height and IGF1 in adult survivors of Wilms tumour

OBJECTIVE

One-sided nephrectomy is followed by increased levels of IGF1, associated with linear growth during childhood. The aim was to evaluate final height and IGF1 levels in nephrectomized Wilms tumour survivors when compared with healthy Dutch references and survivors of other cancer types.

DESIGN

Cross-sectional retrospective study.

METHODS

Data of 575 adult childhood cancer survivors were analysed. median follow-up time was 17.8 (range 5.048.8) years. Analysis of (co)variance was performed to evaluate differences between subgroups: nephrectomized Wilms survivors treated with or without abdominal irradiation (n=41 and n=36) and survivors of other cancer types treated with or without irradiation involving the cranium, abdomen or total body (n=149 and n=349). Main outcome measures were IGF1 and height, expressed as SDS.

RESULTS

After adjustment for age at diagnosis, former corticosteroid treatment and renal impairment, height SDS in non-irradiated nephrectomized Wilms survivors was significantly higher than that in non-irradiated survivors of other cancer types (estimated mean SDS -0.09 vs -0.49, P=0.044), abdominal irradiated survivors (SDS -0.70, P=0.015) and other irradiated survivors (SDS -1.47, P<0.001). Non-irradiated nephrectomized Wilms tumour survivors had significantly higher IGF1 SDS than other irradiated survivors (estimated mean SDS -0.05 vs -1.36, P<0.001 and 0.11 vs 1.37, P<0.001), while there was no significant difference with the other two subgroups.

CONCLUSIONS

Adult survivors of Wilms tumour showed better attainment of final height and relatively higher IGF1 levels than those of other cancer types who had significantly shorter stature and lower IGF1 levels than Dutch references.

Inhibiting Polo-like kinase 1 causes growth reduction and apoptosis in pediatric acute lymphoblastic leukemia cells

This study investigated Polo-like kinase 1, a mitotic regulator often over-expressed in solid tumors and adult hematopoietic malignancies, as a potential new target in the treatment of pediatric acute lymphoblastic leukemia. Polo-like kinase 1 protein and Thr210 phosphorylation levels were higher in pediatric acute lymphoblastic leukemia (n=172) than in normal bone marrow mononuclear cells (n=10) (P<0.0001). High Polo-like kinase 1 protein phosphorylation, but not expression, was associated with a lower probability of event-free survival (P=0.042) and was a borderline significant prognostic factor (P=0.065) in a multivariate analysis including age and initial white blood cell count. Polo-like kinase 1 was necessary for leukemic cell survival, since short hairpin-mediated Polo-like kinase 1 knockdown in acute lymphoblastic leukemia cell lines inhibited cell proliferation by G2/M cell cycle arrest and induced apoptosis through caspase-3 and poly (ADP-ribose) polymerase cleavage. Primary patient cells with a high Polo-like kinase 1 protein expression were sensitive to the Polo-like kinase 1-specific inhibitor NMS-P937 in vitro, whereas cells with a low expression and normal bone marrow cells were resistant. This sensitivity was likely not caused by Polo-like kinase 1 mutations, since only one new mutation (Ser335Arg) was found by 454-sequencing of 38 pediatric acute lymphoblastic leukemia cases. This mutation did not affect Polo-like kinase 1 expression or NMS-P937 sensitivity. Together, these results indicate a pivotal role for Polo-like kinase 1 in pediatric acute lymphoblastic leukemia and show potential for Polo-like kinase 1-inhibiting drugs as an addition to current treatment strategies for cases expressing high Polo-like kinase 1 levels.

Gain of 1q is a marker of poor prognosis in Wilms' tumors

Wilms' tumor (WT) trials aim to better tailor treatment intensity to the risk of relapse and death. Currently, stage, histology, age (< or > 24 months), and combined loss of heterozygosity at 1p and 16q in chemotherapy-naïve WTs are the only risk factors used for treatment stratification. However, they predict only less than one-third of all relapsing patients, implying that other factors are involved in treatment failure. Previous studies have associated 1q gain with adverse outcome. Therefore, in this study, the role of 1q gain and other common cytogenetic aberrations (CAs) in WTs was investigated and related to follow-up data from patients with WT treated in the United Kingdom; 19% (64/331) had 1q gain. Gain of 1q was significantly associated with 16q loss (P < 0.001) and 1p loss (P < 0.001). In multivariate analysis taking account of age, tumor stage, anaplasia, and common CA (e.g., 1p loss and 16q loss), 1q gain was independently associated with adverse event-free survival [EFS; hazard ratio (HR) = 2.45, P = 0.02] and overall survival (HR = 4.28, P = 0.004). Loss of 14q was independently associated with an adverse EFS (HR = 4.0, P = 0.04). Gain of 1q is a marker of poor prognosis in WTs, independent of high tumor stage and anaplasia which remain the overarching adverse prognostic factors. Confirmation in other studies is necessary before future therapeutic studies can incorporate 1q gain into new risk stratification schema.

Immature MEF2C-dysregulated T-cell leukemia patients have an early T-cell precursor acute lymphoblastic leukemia gene signature and typically have non-rearranged T-cell receptors

Three distinct immature T-cell acute lymphoblastic leukemia entities have been described including cases that express an early T-cell precursor immunophenotype or expression profile, immature MEF2C-dysregulated T-cell acute lymphoblastic leukemia cluster cases based on gene expression analysis (immature cluster) and cases that retain non-rearranged TRG@ loci. Early T-cell precursor acute lymphoblastic leukemia cases exclusively overlap with immature cluster samples based on the expression of early T-cell precursor acute lymphoblastic leukemia signature genes, indicating that both are featuring a single disease entity. Patients lacking TRG@ rearrangements represent only 40% of immature cluster cases, but no further evidence was found to suggest that cases with absence of bi-allelic TRG@ deletions reflect a distinct and even more immature disease entity. Immature cluster/early T-cell precursor acute lymphoblastic leukemia cases are strongly enriched for genes expressed in hematopoietic stem cells as well as genes expressed in normal early thymocyte progenitor or double negative-2A T-cell subsets. Identification of early T-cell precursor acute lymphoblastic leukemia cases solely by defined immunophenotypic criteria strongly underestimates the number of cases that have a corresponding gene signature. However, early T-cell precursor acute lymphoblastic leukemia samples correlate best with a CD1 negative, CD4 and CD8 double negative immunophenotype with expression of CD34 and/or myeloid markers CD13 or CD33. Unlike various other studies, immature cluster/early T-cell precursor acute lymphoblastic leukemia patients treated on the COALL-97 protocol did not have an overall inferior outcome, and demonstrated equal sensitivity levels to most conventional therapeutic drugs compared to other pediatric T-cell acute lymphoblastic leukemia patients.

Normal karyotype is a poor prognostic factor in myeloid leukemia of Down syndrome: a retrospective, international study

Myeloid leukemia of Down syndrome has a better prognosis than sporadic pediatric acute myeloid leukemia. Most cases of myeloid leukemia of Down syndrome are characterized by additional cytogenetic changes besides the constitutional trisomy 21, but their potential prognostic impact is not known. We, therefore, conducted an international retrospective study of clinical characteristics, cytogenetics, treatment, and outcome of 451 children with myeloid leukemia of Down syndrome. All karyotypes were centrally reviewed before assigning patients to subgroups. The overall 7-year event-free survival for the entire cohort was 78% (± 2%), with the overall survival rate being 79% (± 2%), the cumulative incidence of relapse 12% (± 2%), and the cumulative incidence of toxic death 7% (± 1%). Outcome estimates showed large differences across the different cytogenetic subgroups. Based on the cumulative incidence of relapse, we could risk-stratify patients into two groups: cases with a normal karyotype (n=103) with a higher cumulative incidence of relapse (21%± 4%) than cases with an aberrant karyotype (n=255) with a cumulative incidence of relapse of 9% (± 2%) (P=0.004). Multivariate analyses revealed that white blood cell count ≥ 20 × 10(9)/L and age >3 years were independent predictors for poor event-free survival, while normal karyotype independently predicted inferior overall survival, event-free survival, and relapse-free survival. In conclusion, this study showed large differences in outcome within patients with myeloid leukemia of Down syndrome and identified novel prognostic groups that predicted clinical outcome and hence may be used for stratification in future treatment protocols.

MiR-125b, miR-100 and miR-99a co-regulate vincristine resistance in childhood acute lymphoblastic leukemia

MicroRNA-125b (miR-125b), miR-99a and miR-100 are overexpressed in vincristine-resistant acute lymphoblastic leukemia (ALL). Cellular viability of ETV6-RUNX1-positive Reh cells significantly increased in presence of 9 ng/mL vincristine upon co-expression of miR-125b/miR-99a (91 ± 4%), miR-125b/miR-100 (93 ± 5%) or miR-125b/miR-99a/miR-100 (82 ± 17%) compared with miR-125b-transduced cells (38 ± 13%, P<0.05). Co-expression of these miRNAs resulted in downregulation of DNTT, NUCKS1, MALAT1, SNRPE, PNO1, SET, KIF5B, PRPS2, RPS11, RPL38 and RPL23A (fold-change 1.3-1.9, p<0.05). Similarly, 7 out of these genes are lower expressed in vincristine-resistant ALL cells of children (p<0.05). The concerted function of miR-125b in combination with miR-99a and/or miR-100 illustrates the complexity of vincristine-resistant pediatric ALL.

Dasatinib in Children and Adolescents With Relapsed or Refractory Leukemia: Results of the CA180-018 Phase I Dose-Escalation Study of the Innovative Therapies for Children With Cancer Consortium

Purpose

Dasatinib is a potent BCR-ABL inhibitor with proven efficacy in adults with newly diagnosed chronic myeloid leukemia (CML) in chronic phase (CP) and in imatinib-resistant/intolerant disease. This phase I study of the Innovative Therapies for Children with Cancer Consortium assessed dasatinib safety and efficacy in pediatric patients.

Patients and Methods

Escalating once-daily dasatinib doses (60 to 120 mg/m2) were administered to children (n = 58) with (i) imatinib-pretreated CML or Philadelphia chromosome (Ph)–positive acute lymhoblastic leukemia (ALL) and (ii) treatment-refractory Ph-negative ALL or acute myeloid leukemia (AML).

Results

Dasatinib safety and efficacy profiles compared favorably with those in adults. The most common drug-related nonhematologic adverse events were nausea (31%, all grades; 2%, grade 3 to 4), headache (22%, 3%), diarrhea (21%, 0%), and vomiting (17%, 2%). Of 17 patients with CML-CP, 14 (82%) achieved complete cytogenetic response (CCyR) and eight (47%) achieved major molecular response. After ≥ 24 months of follow-up, median complete hematologic response (CHR) and major cytogenetic response (MCyR) durations were not reached. Of 17 patients with advanced-phase CML or Ph-positive ALL, six (35%) achieved confirmed CHR and 11 (65%) achieved CCyR. Median MCyR duration was 4.6 months (95% CI, 2.1 to 17.4 months). No patient with Ph-negative ALL or AML responded. Dasatinib pediatric pharmacokinetic parameters were comparable with those in adult studies, showing rapid absorption (time to reach maximum concentration, 0.5 to 6.0 hours) and elimination (mean half-life, 3.0 to 4.4 hours).

Conclusion

Dasatinib 60 mg/m2 and 80 mg/m2 once-daily dosing were selected for phase II studies in children with Ph-positive leukemias.