FLT3 mutations in childhood acute lymphoblastic leukemia

Activating mutations of the FLT3 receptor tyrosine kinase are common in acute myelogenous leukemia (AML) but are rare in adult acute lymphoblastic leukemia (ALL). We have recently shown that FLT3 is highly expressed and often mutated in ALLs with rearrangement of the mixed lineage leukemia (MLL) gene on chromosome 11q23. Because hyperdiploid ALL samples also show high-level expression of FLT3, we searched for the presence of FLT3 mutations in leukemic blasts from 71 patients with ALL. The data show that approximately 25% (6 of 25) of hyperdiploid ALL samples possess FLT3 mutations, whereas only 1 of 29 TEL/AML1-rearranged samples harbored mutations (P =.04, Fisher exact test). Three mutations are novel in-frame deletions within a 7-amino acid region of the receptor juxtamembrane domain. Finally, 3 samples from patients whose disease would relapse harbored FLT3 mutations. These data suggest that patients with hyperdiploid or relapsed ALL might be considered candidates for therapy with newly described small-molecule FLT3 inhibitors.     

Haploidentical transplantation for acute lymphoblastic leukemia in childhood

Haploidentical transplantation in childhood acute lymphoblastic leukemia (ALL) is a promising option for children lacking a suitable donor. We have updated our series of patients with ALL and report the results. Additionally, we reviewed the literature and try to embed our own experiences in the published results. We performed HLA-mismatched stem cell transplantations with megadoses of purified positively selected mobilized peripheral blood CD34+ progenitor cells (PBPC) from adult donors in 27 children with acute lymphoblastic leukemia (ALL) in first (CR1 n = 7), second (CR2 n = 10), or third (CR3 n = 4) complete remission, and in refractory state (NR n = 6). The patients received a mean number of 19.1+/-11.3 x 10(6)/kg purified CD34+ and a mean number of 15.5+/-24.2 x 10(3)/kg CD3+ T-cells. No additional graft-versus-host disease (GVHD) prophylaxis was used, except as short-term CSA in the first 3 patients. The myeloablative treatment was based on busulfan in 12 and on TBI in 14 patients. One patient was grafted with a non-myeloablative approach. Engraftment was rapid in 26 patients, with two patients suffering from a rejection. These two and one patient with initial non-engraftment had been successfully regrafted. The probability of survival of the total group is 0.34+/-0.09; the 12 patients transplanted in remission showed a probability of survival of 0.44+/-0.11. None of the patients transplanted in non-remission survived. There was no statistical difference in survival for patients with a 1, 2 or 3 antigen mismatched donor (out of 6 HLA antigens) or for patients in 1st, 2nd or 3rd remission. Causes of death were relapses in 10 patients, veno-occlusive disease (VOD) in 1, multi-organ failure (MOF) in 2 and infections in 4 patients. 3/24 evaluable patients without any additional GVHD-prophylaxis developed grade 1 or 2 GVHD. Ten patients were treated with additional donor lymphocyte infusion (DLI), from which 4 developed a maximum grade 3 GVHD. We conclude that the HLA barrier can be overcome by transplantation of megadoses of highly purified CD34+ PBPC and GVHD can effectively be prevented. This approach offers a promising treatment option for patients with acute lymphoblastic leukemia needing urgently transplantation but lacking a suitable donor.     

Philadelphia chromosome positive childhood acute lymphoblastic leukemia

In a 3-yr period, the Philadelphia chromosome (Ph1) was found in 4 of 43 children with acute lymphoblastic leukemia (ALL) in whom chromosomes were studied at diagnosis. The clinical, morphological, cytochemical, and immunologic findings in the Ph1-positive (PH1+) CASES WERE CONsistent with typical childhood ALL, indicating that identification of cases requires chromosome studies. A review of all reported cases of Ph1 + childhood ALL shows that Ph1 + patients are older and have higher initial platelet and white blood cell counts (WBC) than most children with ALL. However, a life table comparison between the reported cases of Ph1 + ALL in children and randomly selected age-, sex-, and WBC- matched controls with ALL shows the duration of first marrow remission to be significantly shorter (p less than 0.02) for the Ph1 + cases Ph1 + ALL is a distinct subtype of childhood ALL that is not rare and can be identified only by cytogenetic studies. The prognosis is poor. Cytogenetic studies should be done prospectively in a large group of children with ALL to define further the subgroup of patients and to confirm the findings of this retrospective analysis.     

Outcome heterogeneity in childhood high-hyperdiploid acute lymphoblastic leukemia

High hyperdiploidy (HeH) (51 to 65 chromosomes) is found in one third of children with acute lymphoblastic leukemia and is associated with a good prognosis. Cytogenetic features may further refine this prognosis and identify patients with a poor outcome. We examined the effect of sex, age, individual trisomies, modal number, and structural abnormalities on survival among 700 children with HeH. Univariate analysis showed that age. sex, +4, +10, +18, and a high modal number were associated with survival. Multivariate analysis however, revealed that only age, sex, +4, and +18 were independent indicators. Hazard scores for predicting relapse and mortality were constructed. Three risk groups with 5-year event-free survival (EFS) rates of 86%, 75%, and 50% (P <.0001) were identified. The high-risk group comprised boys older than 9 years, boys aged 1 through 9 years without +18, and girls older than 9 years without +18, while girls aged 1 through 9 years with +18 had the best EFS. In terms of mortality, those younger than age 10 years with both +4 and +18 had an improved survival (96% vs 84% at 5 years, P <.0001). These findings confirm that the outcome of children with HeH is heterogeneous and that specific trisomies can identify patients with the greatest and least risk of treatment failure.     

Outcome after relapse in childhood acute lymphoblastic leukemia

Among 157 children with acute lymphoblastic leukemia (ALL) who experienced relapse at 54 institutes participating in the Japan Association of Childhood Leukemia Study, we analyzed the outcomes after relapse in 103 and 30 eligible cases with bone marrow (BM) and central nervous system (CNS) relapse, respectively. Reinduction rates in BM and CNS relapse cases were 72.3% and 83.3%, respectively. High reinduction rates were observed in B-precursor (B-pre) phenotype ALL in both relapse groups and in late (more than 24 months from onset) BM-relapse patients. After BM relapse, the overall 5-year survival rate was superior in the allogeneic stem cell transplantation (SCT) group compared to the non-SCT group (41.9%+/-8.2% versus 13.6%+/-6.5%, P < .0001). In contrast, the 4-year overall survival rate was not significantly different between the SCT (allogeneic plus autologous) and non-SCT groups after CNS relapse (26.8%+/-14.2% versus 61.9%+/-12.3%, P = .252). The late BM-relapse patients showed a significantly higher survival rate than did early-relapse patients, and survival rates were similar between the allogeneic and autologous group when the patients underwent SCT during a second complete remission. Moreover, B-pre ALL patients classified in the standard-risk group according to National Cancer Institute/Rome's criteria at onset had a good prognosis after allogeneic SCT. Improving the cure rate in relapsed ALL patients requires more intensive reinduction therapy and efforts to succeed with SCT in early BM-relapse patients as well as the establishment of a treatment strategy including indications of SCT for CNS-relapse patients.     

Lung function in survivors of childhood acute lymphoblastic leukemia

STUDY OBJECTIVES: To evaluate lung function in patients cured from childhood acute lymphoblastic leukemia (ALL) with chemotherapy alone or plus bone marrow transplantation (BMT). Pulmonary toxicity is a well-recognized side effect of many ALL treatments. DESIGN: Cross-sectional study conducted at least 3 years after cessation of therapy. SETTING: Outpatient pneumology department of the University Hospital. PATIENTS: Forty-four subjects (age range at observation, 6 to 23 years): 21 treated only with intensive Berlin-Frankfurt-Munster (BFM)-type chemotherapy for newly diagnosed ALL (group A), and 23 treated with chemotherapy plus BMT (group B). MEASUREMENTS: A detailed history of smoking habit, respiratory symptoms, and diseases was recorded directly from the patients with the aid of their parents. A complete physical examination and lung function testing (lung volumes and diffusion capacity for carbon monoxide [DLCO]) were performed in all subjects. RESULTS: No patient reported acute or chronic respiratory symptoms or diseases. In group A patients, lung function was in the normal range, except for three subjects in whom there was an isolated impairment of DLCO. In group B patients, lung function was markedly impaired, with more than half the patients having an abnormal DLCO. A statistically significant difference was found between the two groups for FVC (p = 0.022) and DLCO (p = 0.004). CONCLUSIONS: Intensive, BFM-type frontline chemotherapy is not associated with late pulmonary dysfunction; however, retreatment including BMT can frequently injure the lung. Thus, in patients who undergo BMT and whose life expectancy is long, careful monitoring of lung function and counseling about avoiding additional lung risk factors is recommended.     

New recurring chromosomal translocations in childhood acute lymphoblastic leukemia

We identified seven new recurring translocations among 483 cases of acute lymphoblastic leukemia (ALL) with adequate chromosome banding studies. Four were apparently balanced [t(1;3)(p34;p21), t(7;9)(p15;p23-p24), t(12;13)(p13;q14), t(17;19)(q22;p13)], while three were unbalanced with the formation of a dicentric chromosome [dic(7;9)(p13;p11), dic(7;12)(p11;p12), and dic(12;17)(p11;p11-p12)]. One translocation was observed in five cases, two in four cases, and the remaining four in two cases each. The modal chromosome numbers in these 21 cases were 45 (n = 11), 46 (n = 8), and 47 (n = 2). Eight of the 11 cases with a dicentric chromosome had a modal number of 45. Only a single translocation was found in 14 cases (67%), representing the sole structural abnormality in six cases. In three of the seven translocation subgroups, the blast cells were consistently of B lineage (pre-B, early pre-B, or both); in all others, they represented both the B and T lineages. The small size of these subgroups prevented definitive clinical correlations, although it may be important that two of the four cases with a t(17;19) and an early pre-B-cell immunophenotype had disseminated intravascular coagulation, an event usually observed in acute promyelocytic leukemia or T-cell ALL. These findings add substantially to the existing list of nonrandom chromosomal translocations in childhood ALL and may help to explain the genetic alterations leading to the loss of normal growth control mechanisms in this disease.     

Near-triploid and near-tetraploid acute lymphoblastic leukemia of childhood

Cytogenetic and DNA flow cytometric analyses of leukemic cells from 1,971 children with newly diagnosed acute lymphoblastic leukemia (ALL) identified stem lines with modal chromosome numbers greater than 65 in 26 patients (1.3%). Near-triploidy (66 to 73 chromosomes) was found in six cases and near-tetraploidy (82 to 94 chromosomes) in 20. A striking morphologic finding was the presence of clumped chromatin with grooved nuclei or Rieder cell formation in 20 cases. Other than a slight excess of the pre-B immunophenotype, the near-triploid cases did not appear to differ substantially from the general ALL population in clinical features. In contrast, near-tetraploid cases were more often associated with a T-cell immunophenotype (47% v 14%, P less than .001) and L2 morphology (30% v 22%, P less than .01), and were older at diagnosis (median age, 8.6 v 4.8 years, P = .01) than cases with other ploidies. Moreover, an unusually high proportion of near-tetraploid cases tested (6 of 15) expressed one or more of the myeloid-associated antigens CD13, CD15, and CD33. Despite the use of contemporary intensive chemotherapy and short follow-up for most patients, 6 of the 20 near- tetraploid cases have relapsed or died. This study suggests that the near-tetraploid subtype differs from other cases of hyperdiploid greater than 50 ALL, which have been associated with a favorable prognosis.     

Rapamycin stimulates apoptosis of childhood acute lymphoblastic leukemia cells

The phosphatidyl-inositol 3 kinase (PI3k)/Akt pathway has been implicated in childhood acute lymphoblastic leukemia (ALL). Because rapamycin suppresses the oncogenic processes sustained by PI3k/Akt, we investigated whether rapamycin affects blast survival. We found that rapamycin induces apoptosis of blasts in 56% of the bone marrow samples analyzed. Using the PI3k inhibitor wortmannin, we show that the PI3k/Akt pathway is involved in blast survival. Moreover, rapamycin increased doxorubicin-induced apoptosis even in nonresponder samples. Anthracyclines activate nuclear factor kappaB (NF-kappaB), and disruption of this signaling pathway increases the efficacy of apoptogenic stimuli. Rapamycin inhibited doxorubicin-induced NF-kappaB in ALL samples. Using a short interfering (si) RNA approach, we demonstrate that FKBP51, a large immunophilin inhibited by rapamycin, is essential for drug-induced NF-kappaB activation in human leukemia. Furthermore, rapamycin did not increase doxorubicin-induced apoptosis when NF-kappaB was overexpressed. In conclusion, rapamycin targets 2 pathways that are crucial for cell survival and chemoresistance of malignant lymphoblasts--PI3k/Akt through the mammalian target of rapamycin and NF-kappaB through FKBP51--suggesting that the drug could be beneficial in the treatment of childhood ALL.     

Serum interleukin 2 receptor levels in childhood acute lymphoblastic leukemia

The clinical significance of interleukin 2 receptor (IL2R) concentrations in serum was determined for 344 children with newly diagnosed acute lymphoblastic leukemia (ALL). Serum levels of IL2R in patients (267 to 80,000 U/mL, median 2,007 U/mL) were significantly higher than normal control values (170 to 738 U/mL, median 347 U/mL) (P less than .0001). Measurements in cases of T cell ALL were lower than in the non-T, non-B cases (P = .02). Among the 264 patients with non-T, non-B ALL, but not in those with T cell disease, higher serum IL2R levels (greater than 2,000 U/mL) were associated with a poorer treatment outcome (P = .04). In a multivariate analysis, serum IL2R level contributed independent prognostic information beyond that conveyed by leukocyte count, race, and age (P = .04). One explanation for these results is that soluble IL2R competes with normal lymphocyte- integrated IL2R for the ligand and thus could suppress host antitumor immunity.