Impact of FLT3 Receptor (CD135) Detection by Flow Cytometry on Clinical Outcome of Adult Acute Myeloid Leukemia Patients.

BACKGROUND: The significance of FMS-like tyrosine kinase 3 (FLT3)-ITD mutation in acute myeloid leukemia (AML) prognosis has been well established. The aims of this study were to investigate the prognostic impact of the FLT3 protein (CD135) expression and its association with FLT3-ITD mutation, and to identify its role in minimal residual disease. PATIENTS AND METHODS: CD135 was measured by flow cytometry on leukemic blasts of 257 adults with de novo AML. High expression of CD135 ≥ 20% was correlated with clinical, laboratory, and other prognostic factors that influenced treatment outcome. FLT3-ITD mutation was tested by PCR. RESULTS: The frequency of CD135 expression was 138 (53.7%) of 257. FLT3-ITD was detected in (21.4%). Positive CD135 expression was associated with high total leukocyte count (P = .006), platelet count (P = .003), monocytic leukemia (P < .001), and CD34 (P = .008) and CD117 (P = .006) expression. CD135 expression ≥ 25% was a predictor of FLT3-ITD mutation (P = .03). CD135 overexpression was a negative predictor of complete remission and of postinduction minimal residual disease at days 14 and 28 (P < .001). CD135 had an adverse impact on overall and disease-free survival (68.5% vs. 15%, P = .002). Multivariate analysis indicated CD135 was the sole independent prognostic factor for overall survival (hazard ratio = 2.49; 95% confidence interval, 1.855-3.345; P < .001). CONCLUSION: CD135 is emerging as a prognostic factor, a new marker for minimal residual disease, and a potential novel therapeutic target of AML.

SLC29A1 single nucleotide polymorphisms as independent prognostic predictors for survival of patients with acute myeloid leukemia: an in vitro study.

BACKGROUND: The mechanism behind poor survival of acute myeloid leukemia (AML) patients with 1-barabinofuranosylcytosine (Ara-C) based treatment remains unclear. This study aimed to assess the pharmacogenomic effects of Ara-C metabolic pathway in patients with AML. METHODS: The genotypes of 19 single nucleotide polymorphisms (SNPs) of DCK, CDA and SLC29A1from 100 AML patients treated with Ara-C were examined. All the SNPs were screened with ligase detection reaction assay. The transcription analysis of genes was examined by quantitative real time polymerase chain reaction. The association between clinical outcome and gene variants was evaluated by Kaplan-Meier method. RESULTS: Genotypes of rs9394992 and rs324148 for SLC29A1 in remission patients were significantly different from those in relapsed ones. Post-induction overall survival (OS) significantly decreased in patients with the CC genotype of rs324148 compared with CT and TT genotypes (hazard ratio [HR] = 2.997 [95% confidence interval (CI): 1.71-5.27]). As compared with CT and TT genotype, patients with the CC genotype of rs9394992 had longer survival time (HR = 0.25 [95% CI: 0.075-0.81]; HR = 0.43 [95% CI: 0.24-0.78]) and longer disease-free survival (DFS) (HR = 0.52 [95% CI: 0.29-0.93]; HR = 0.15 [95% CI: 0.05-0.47]) as well As compared with CT and TT genotype, patients with the CC genotype of rs324148 had shorter DFS (HR = 3.18 [95% CI: 1.76-5.76]). Additionally, patients with adverse karyotypes had shorter DFS (HR = 0.17 [95% CI: 0.05-0.54]) and OS (HR = 0.18 [95% CI: 0.05-0.68]). CONCLUSIONS: AML patients with low activity of SLC29A1 genotype have shorter DFS and OS in Ara-C based therapy. Genotypes of rs9394992 and rs324148 may be independent prognostic predictors for the survival of AML patients.

Lineage switch in childhood acute leukemia: an unusual event with poor outcome.

Although rarely, switches between lymphoid and myeloid lineages may occur during treatment of acute leukemias (AL). Correct diagnosis relies upon confirmation by immunophenotyping of the lineage conversion and certification that the same cytogenetic/molecular alterations remain despite the phenotypic changes. From a total of 1,482 AL pediatric patients, we report nine cases of lineage conversion (0.6%), seven from lymphoid (four Pro-B, two Pre-B, one Common) to myelo-monocytic, and two from myeloid (bilineal, with myeloid predominance) to Pro-B. Eight patients were infants. Switches were suggested by morphology and confirmed with a median of 15 days (range: 8 days-6 months) from initiation of therapy. Of note, in five cases switches occurred before day 15. Stability of the clonal abnormalities was assessed by cytogenetic, RT-PCR/Ig-TCR rearrangement studies in all patients. Abnormalities in 11q23/MLL gene were detected in seven cases. Treatment schedules were ALL (two pts), Interfant-99 (five pts) and AML (two pts) protocols. Despite changing chemotherapy according to the new lineage, all patients died. Our findings support the association of lineage switches with MLL gene alterations and the involvement of a common lymphoid B-myeloid precursor. New therapies should be designed to address these rare cases. Possible mechanisms implicated are discussed.

Dexamethasone in patients with acute lung injury from acute monocytic leukaemia.

The use of steroids is not required in myeloid malignancies and remains controversial in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). We sought to evaluate dexamethasone in patients with ALI/ARDS caused by acute monocytic leukaemia (AML FAB-M5) via either leukostasis or leukaemic infiltration. Dexamethasone (10 mg every 6 h until neutropenia) was added to chemotherapy and intensive care unit (ICU) management in 20 consecutive patients between 2005 and 2008, whose data were compared with those from 20 historical controls (1994-2002). ICU mortality was the primary criterion. We also compared respiratory deterioration rates, need for ventilation and nosocomial infections. 17 (85%) patients had hyperleukocytosis, 19 (95%) had leukaemic masses, and all 20 had severe pancytopenia. All patients presented with respiratory symptoms and pulmonary infiltrates prior to AML FAB-M5 diagnosis. Compared with historical controls, dexamethasone-treated patients had a significantly lower ICU mortality rate (20% versus 50%; p = 0.04) and a trend for less respiratory deterioration (50% versus 80%; p = 0.07). There were no significant increases in the rates of infections with dexamethasone. In conclusion, in patients with ALI/ARDS related to AML FAB-M5, adding dexamethasone to conventional chemotherapy seemed effective and safe. These results warrant a controlled trial of dexamethasone versus placebo in AML FAB-M5 patients with noninfectious pulmonary infiltrates.

Different clinical importance of FLT3 internal tandem duplications in AML according to FAB classification: possible existence of distinct leukemogenesis involving monocyte differentiation pathway.

Impact of FLT3 receptor tyrosine kinase activation via internal tandem duplication (ITD) of the juxtamembrane region on outcome of acute myeloid leukemia (AML) is still controversial. Recent researches reveal a role of FLT3 in monocyte differentiation in hematopoiesis. We analyzed the clinical impact of FLT3 alterations in adult AML patients excluding acute promyelocytic leukemia (APL) who received induction chemotherapy according to morphologic classification. Retrospective review of medical records from three centers in Korea between 1997 and 2007 was performed. Polymerase chain reaction was performed on genomic DNA derived from blood samples of patients before induction chemotherapy for FLT3-ITD detection. We assessed overall survival (OS), first disease-free survival (1-DFS), and response to induction chemotherapy. One hundred eighty-four patients (median age 49.1 years, range 16.0-76.5) with AML excluding APL received induction chemotherapy from three centers. FLT3-ITD was detected in 22 patients. One hundred forty-one patients were below age 60. One hundred seventy-nine patients received induction chemotherapy with cytarabine and idarubicin (AId) regimen. One hundred nineteen patients achieved complete remission (CR) after first induction chemotherapy. FLT3-ITD was not related to achievement of CR. 1-DFS was longer in patients without FLT3-ITD (median 1-DFS 16.5 vs. 8.5 months, p = 0.025). 1-DFS was not different according to FLT3-ITD status in nonmonocyte lineage leukemia (p = 0.355), while 1-DFS was shorter in monocyte lineage leukemia for FLT3-ITD positive patients (20.9 vs. 2.4 months, p < 0.001). FLT3-ITD had no impact on OS except for monocyte lineage, where OS was significantly shorter in FLT3-ITD positive group (39.4 vs. 6.0 months, p = 0.026). Moreover FLT3-ITD was stronger prognostic factors in monocyte lineage AML than risk stratification based on cytogenetics. Status of FLT3-ITD should be analyzed differently in AML patients according to morphologic profile. FLT3-ITD is a predictive and prognostic marker only in monocyte lineage patients. This result suggests an existence of distinct subset of monocyte lineage AML with leukemogenesis involving FLT3 activating pathway.

Continuous drip infusion of low dose cytarabine and etoposide with granulocyte colony-stimulating factor for elderly patients with acute myeloid leukaemia ineligible for intensive chemotherapy.

BACKGROUNDS AND OBJECTIVES: The optimal strategy for the management of elderly patients with acute myeloid leukaemia (AML) is still controversial. We previously reported the effectiveness of low dose cytarabine (Ara-C) and etoposide (VP-16) (AV therapy) for those elderly AML patients ineligible for intensive chemotherapy. We initiated the present feasibility study to improve the efficacy by using glanulocyte-colony stimulating factor (G-CSF) with AV therapy (AVG therapy). PATIENTS AND METHODS: The eligibility for enrolment was AML patients according to the World Health Organization (WHO) criteria who were over 60 years of age and who had difficulty in tolerating intensive chemotherapy due to their poor performance status (PS) or some comorbidities. They were given continuous drip infusion of Ara-C (20 mg/body) and VP-16 (50 mg/body) for 7-14 days, and were also simultaneously administered G-CSF (150 microg/m2) once daily. RESULTS: The median age of consecutively enrolled 25 patients was 73 years. Eighteen (72%) patients achieved complete remission (CR). The 1-year overall survival (OS) and the 3-year OS rates were 69% and 22%, respectively. The 1-year disease free survival (DFS) rate in CR patients was 44%. The major regimen related toxicities of grade 3 or 4 were only febrile neutropenia in 15 patients (60%). No regimen-related mortality was observed. CONCLUSION: AVG therapy was therefore found to be an effective and well-tolerated regimen for remission induction in elderly AML patients with poor PS or comorbidity.

Comparison of cytogenetics and clinical manifestations between M5a and M5b of acute monocytic leukemia.

To compare the cytogenetic difference between M5a and M5b of acute monocytic leukemia and to study the correlation between karyotypes and clinical manifestations, a total of 58 cases of de novo adult AML M5 have been investigated. Chromosome metaphases of bone marrow cells were prepared by using direct method and 24 hours short-term culture. The karyotypes were analyzed by G-banding. Meanwhile, clinical information of these cases were studied retrospectively. The results showed that there were 28 with normal karyotype and 30 with aberrant karyotype in 58 cases. The frequency of normal karyotype in patients with M5b was significantly higher than that in patients with M5a (P = 0.0001). The 11q23 aberrations and trisomy 8 were more common in patients with M5a in comparison with patients with M5b (P < 0.01). The patients with AML M5 with aberrant karyotype had a higher incidence of hyperleukocytosis, extramedullary central nerve system infiltration, lower complete remission (CR) rate and shorter overall survival. It is concluded that acute monocytic leukemia is a series of heterogeneous diseases, a distinctive cytogenetic features can be observed between patients with AML M5a and M5b, these results will provide insights into the classification and pathogenesis mechanism of AML M5 at molecular level.

Expression of beta-catenin by acute myeloid leukemia cells predicts enhanced clonogenic capacities and poor prognosis.

Activation of the Wnt/beta-catenin pathway has recently been shown to be crucial to the establishment of leukemic stem cells in chronic myeloid leukemia. We sought to determine whether beta-catenin was correlated to clonogenic capacity also in the acute myeloid leukemia (AML) setting. Eighty-two patients were retrospectively evaluated for beta-catenin expression by Western blot. beta-Catenin was expressed (although at various protein levels) in 61% of patients, and was undetectable in the remaining cases. In our cohort, beta-catenin expression was correlated with the clonogenic proliferation of AML-colony forming cells (AML-CFC or CFU-L) in methylcellulose in the presence of 5637-conditioned medium, and more strikingly with self-renewing of leukemic cells, as assessed in vitro by a re-plating assay. In survival analyses, beta-catenin appeared as a new independent prognostic factor predicting poor event-free survival and shortened overall survival (both with P<0.05). Furthermore, variations in beta-catenin protein levels were dependent on post-transcriptional mechanisms involving the Wnt/beta-catenin pathway only in leukemic cells. Indeed, beta-catenin negative leukemic cells were found to increase beta-catenin in response to Wnt3a agonist in contrast to normal counterparts. Altogether, our data pave the way to the evaluation of Wnt pathway inhibition as a new rationale for eradicating the clonogenic pool of AML cells.

Acute monocytic leukemia (French-American-British classification M5) does not have a worse prognosis than other subtypes of acute myeloid leukemia: a report from the Eastern Cooperative Oncology Group.

PURPOSE: Acute monocytic leukemia is a distinct subtype of acute myeloid leukemia (AML) with characteristic biologic and clinical features. This study was designed to compare the outcome of patients with M5 to that of other subtypes of AML, and to identify differences in M5a and M5b. PATIENTS AND METHODS: We reviewed all patients with AML M5 entered in three clinical trials for newly diagnosed AML conducted by the Eastern Cooperative Oncology Group between 1989 and 1998. Eighty-one patients, 21 with M5a and 60 with M5b, were identified. RESULTS: The complete remission rate was 62% for all patients with M5; 52% for patients with M5a and 65% for patients with M5b (P =.3), and 60% for the 1122 patients with non-M5 AML entered on the same clinical trials (P =.8 for M5 v non-M5). The 3-year disease-free survival was 26% for all M5 patients; 18% for M5a and 28% for M5b (P =.31), and 33% for non-M5 patients (P =.13 for M5 v non-M5). The 3-year overall survival was 31% for all M5 patients; 33% for M5a and 30% for M5b (P =.65), and 30% for non-M5 (P =.74 for M5 v non-M5). The karyotypes of patients with AML M5 were heterogeneous. CD11b was the only leukemic cell antigen expressed differently in M5a (53%) compared to M5b (77%) to a significant degree (P =.02). CONCLUSION: AML M5 represents an immunologically heterogeneous population similar to non-M5 AML with a prognosis that is not dependent on morphology. The disease-free survival and overall survival of patients with M5a, M5b, and non-M5 appear not to differ with currently available therapy.

AML with 11q23/MLL abnormalities as defined by the WHO classification: incidence, partner chromosomes, FAB subtype, age distribution, and prognostic impact in an unselected series of 1897 cytogenetically analyzed AML cases.

Acute myeloid leukemia (AML) cases with 11q23 abnormalities involving the MLL gene comprise one category of recurring genetic abnormalities in the WHO classification. In an unselected series of 1897 AML cases, 54 patients with an 11q23/MLL rearrangement were identified, resulting in an incidence of 2.8%. The incidence of AML with MLL rearrangement was significantly higher in therapy-related AML (t-AML) than in de novo AML (9.4% vs 2.6%, P <.0001). The frequency of MLL rearrangements was significantly higher in patients younger than 60 years (5.3% vs 0.8%, P <.0001). While the incidence of MLL rearrangements in AML M4, M5a, and M5b was 4.7%, 33.3%, and 15.9%, respectively, it was found in only 0.9% of all other French-American-British (FAB) subtypes (P <.0001). Compared with AML with intermediate karyotype, AML with 11q23/MLL rearrangement had a worse outcome, which was rather comparable with AML with unfavorable karyotype. Compared with t-AML, the median overall survival (OS) of de novo AML with MLL rearrangement was significantly better (2.5 vs 10 months, P =.0143). No significant differences in median OS were observed between cases with t(9;11) compared with all other MLL rearrangements (10.0 vs 8.9 months, P =.36). In conclusion, the category AML with 11q23/MLL abnormalities accounts for 2.8% of unselected AML, is closely associated with monocytic differentiation, and has a dismal prognosis. (

Acute monocytic leukemia presenting as acute respiratory failure.

Acute respiratory failure revealing acute monocytic leukemia is rare. We report 20 patients admitted to the intensive care unit (ICU) with three remarkable features: (1) rapidly progressive respiratory distress revealing acute leukemia, (2) monocytic leukemia, and (3) respiratory status deterioration after chemotherapy initiation. The median age was 50 years (17-72 years), and respiratory symptoms started 2 days (0-15 days) before ICU admission. The median leukocyte count was 98,250/mm3 (800-529,000), with circulating monocytic cells in all of the patients but one. Bone marrow examination was diagnostic of monocytic leukemia in all patients. At presentation, respiratory rate was 33 (18-50) per minute, and PaO2 on room air was 44.5 mm Hg (30-60). Chest radiographs revealed unilateral alveolar infiltrates (n = 1), bilateral alveolar infiltrates with (n = 3) or without (n = 11) pleural effusion, or diffuse interstitial infiltrates (n = 5). Alveolar hemorrhage was the main bronchoalveolar lavage finding, with monocytic cells retrieved from four patients. Respiratory function deteriorated after cancer chemotherapy initiation in all patients. Of the 15 patients who required mechanical ventilation, 10 died. Leukemic pulmonary infiltration as the first manifestation of acute monocytic leukemia should be recognized, and intensive management should be provided in anticipation of the respiratory function deterioration seen consistently after chemotherapy initiation.

[Childhood acute myeloblastic leukemias. Report of 21 cases]. / Leucémies aiguës myéloblastiques de l'enfant. A propos de 21 cas.

Between 1989 and 1996, 21 cases with acute non lymphoblastic leukemia (11 males and 10 females) were diagnosed in our institution. Median age was 9 years (range, 2-15 years). Leukocyte count was more than 50,109/l in 47% of cases. According to the French-American-British (FAB) criteria, 7 cases were classified M1, 10 cases were classified M2, 1 classified M4Eo and 3 classified M5. All patients were treated with "7 + 3" protocol and complete remission was achieved in 17 cases (80%), 2 cases (10%) failed to respond and 2 (10%) died during induction. Relapse was observed in 15 cases. The 3-year survival rate was 20% and the relapse-free-survival rate was 12% confirming the worse prognosis of this leukemia when treated with standard chemotherapy.

Prognostic factors in infants with acute myeloid leukemia.

Little is known about the factors that affect treatment outcome in very young children with acute myeloid leukemia (AML). We therefore analyzed the prognostic impact of various presenting clinical and laboratory features by discrete age group in 299 children with AML treated in four consecutive clinical trials between 1980 and 1997. Differences in presenting features, as well as treatment outcome, were compared between children aged 12 months or less (n = 28) or 13 to 24 months (n = 28) and those more than 24 months of age (n = 243). Children in the two youngest groups (24 months of age or less) had similar presenting features and treatment outcome. Collectively, these 56 children were significantly more likely than the 243 older patients to have M4 or M5 leukemia (70% vs 30%), CNS leukemia (33% vs 22%), the t(9;11) (p22;q23) (18% vs 6%) or other 11q23 translocations (23% vs 3%), and less likely to have Auer rods (2% vs 54%) or the t(8;21) (q22;q22) (0% vs 17%). Among patients aged 24 months or less, two factors independently predicted a favorable prognosis: FAB M4 or M5 leukemia (relative risk of relapse, 0.4; 95% confidence interval, 0.2-0.9) and the t(9;11) (relative risk, 0.3; 95% confidence interval, 0.1-1.0). Leukocyte count and 11q23 translocations other than the t(9;11) lacked prognostic significance. Among older patients, a leukocyte count <50 x 10(9)/l and the presence of the t(9;11) conferred a favorable prognosis.

[Study on clinical and molecular biological characteristics of infant acute leukemia].

OBJECTIVE: To study the clinical and molecular biological characteristics of infant acute leukemia (IAL). METHODS: R and/or G banding technique was used for analysis of karyotype. DNA blotting for HRX gene rearrangement, and polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR) for fusion gene detection. RESULTS: Twenty cases of IAL were detected. HRX gene rearrangement was found in 10 cases, including HRX/AF-4 fusion gene in 5, HRX/AF-9 fusion in 2, and HRX/ENL fusion in 1, HRX self-fusion mediated by alu-repeat homologous recombination and HRX/EEN fusion each in one (HRX/EEN is a novel fusion gene reported for the first time). CONCLUSION: High frequency of HRX gene rearrangement occurred in IAL, which is characterised by a massive leukemia cell burden and 11q23 translocation, forming fusion genes, especially HRX/AF-4 (about 50%). The results are of important significance in guiding clinical treatment and approaching the etiology of IAL.

[244 patients with hyperleukocytic acute leukemia. Shanghai Leukemia Cooperation Group].

To know the clinical characteristics and the prognostic factors of hyperleukocytic acute leukemia, we reviewed 244 patients with acute leukemia associated with hyperleukocytosis. Restrospective analysis and control study were used. Hyperleukocytosis occured in 8.5% of patients with acute leukemia. Hyperleukocytosis in ALL was more common than that in AML. Among AML with hyperleukocytosis, M5 subtype was the most. Hepatomegaly, splenomegaly, lymphadenopathy, DIC and CNSL were more frequent in hyperleukocytosis group. The complete remission rate was 41.4% for patients with hyperleukocytosis versus 54.2% for patients with non-hyperleukocytosis. The early mortality rate was significantly increased in hyperleukocytic patients (23.8%) as compared to the nonhyperleukocytic group (11.1%). Intracranial hemorrhage was the main cause of early death. The high risk factors of early death were: hemoglobin < or = 40 g/L, blood platelet < or = 30 x 10(9)/L, DIC, infection, CNSL at presentation. Acute leukemia with hyperleukocytosis has poor prognosis. Especially, acute myeloid leukemia with hyperleukocytosis must be taken seriously because of high early mortality rate.

Determination of leukemogenic benzene exposure concentrations: refined analyses of the Pliofilm cohort.

Biologic data on benzene metabolite doses, cytotoxicity, and genotoxicity often show that these effects do not vary directly with cumulative benzene exposure (i.e., concentration times time, or c x t). To examine the effect of an alternate exposure metric, we analyzed cell-type specific leukemia mortality in Pliofilm workers. The work history of each Pliofilm worker was used to define each worker's maximally exposed job/department combination over time and the associated long-term average concentration associated with the maximally exposed job (LTA-MEJ). Using this measure, in conjunction with four job exposure estimates, we calculated SMRs for groups of workers with increasing LTA-MEJs. The analyses suggest that a critical concentration of benzene exposure must be reached in order for the risk of leukemia or, more specifically, AMML to be expressed. The minimum concentration is between 20 and 60 ppm depending on the exposure estimate and endpoint (all leukemias or AMMLs only). We believe these analyses are a useful adjunct to previous analyses of the Pliofilm data. They suggests that (a) AMML risk is shown only above a critical concentration of benzene exposure, measured as a long-term average and experienced for years, (b) the critical concentration is between 50 and 60 ppm when using a median exposure estimate derived from three previous exposure assessments, and is between 20 and 25 ppm using the lowest exposure estimates, and (c) risks for total leukemia are driven by risks for AMML, suggesting that AMML is the cell type related to benzene exposure.

Risk of benzene-induced leukemia predicted from the Pliofilm cohort.

This report updates the risk assessment by Crump and Allen for benzene-induced leukemia that was based on a cohort exposed to benzene in the manufacture of Pliofilm. The present study derives new risk estimates using data from follow-up through 1987 (whereas the earlier assessment only had follow-up available through 1978) and uses new exposure information for this cohort developed by Paustenbach et al. that accounts for a number of factors that were unknown or not fully evaluated in earlier exposure assessments. There was a significant excess of acute myelocytic or acute monocytic leukemia (AMML) (8-10 observed, 1.61 expected) in this cohort, and this end point also exhibited a strong dose-response trend. No other types of lymphatic or hematopoietic cancer were clearly linked to benzene exposure. Quantitative risk estimates were robust with respect to whether AMML or all leukemia was being modeled. They were also robust with respect whether the Paustenbach et al. or Crump and Allen exposure estimates were used (differences in risk estimates of no greater than 2-fold) as long as linear dose-response models were applied. However, whereas the Crump and Allen exposures predicted a linear dose response, the Paustenbach et al. exposures predicted a quadratic dose response. This departure from linearity was borderline significant (p = 0.08). Estimates of additional lifetime from 45 years of occupational exposure (lifetime exposure) to 1 ppm derived using he Paustenbach et al. exposure matrix and best-fitting (quadratic) models ranged from 0.020 to 0.036 per thousand, whereas corresponding estimates based on a linear dose response ranged from 1.6 to 3.1 per thousand.

The human homologue of rat NG2, a chondroitin sulfate proteoglycan, is not expressed on the cell surface of normal hematopoietic cells but is expressed by acute myeloid leukemia blasts from poor-prognosis patients with abnormalities of chromosome band 11q23.

In our efforts to produce monoclonal antibodies that recognize cell-surface antigens expressed by hematopoietic precursor and stromal cells, we generated a monoclonal antibody, 7.1, which recognizes a 220- to 240-kD cell-surface protein whose N-terminal amino acid sequence is identical to the rat NG2 chondroitin sulfate proteoglycan molecule. This chondroitin sulfate proteoglycan, previously reported to be expressed by human melanoma cells, was not found to be expressed by normal hematopoietic cells, nor was it expressed on the cell surface of cell lines of hematopoietic origin including cell lines with 11q23 abnormalities. It was found on the cell surface of acute myeloid leukemia (AML) blasts and cell lines derived from nonhematopoietic tissues. Samples of leukemic marrow from 166 children with AML enrolled on Childrens Cancer Group protocol 213 were evaluated for cell-surface expression of this proteoglycan molecule. In 18 of 166 (11%) patient samples, greater than 25% of leukemic blasts expressed the NG2 molecule. These 18 patients had a poorer outcome with respect to survival (P = .002) and event-free survival (P = .035) with an actuarial survival at 4 years of 16.7%. Blast cell expression of the NG2 molecule was strongly associated with French-American-British M5 morphology (P < .0001) and abnormalities in chromosome band 11q23, site of the MLL gene. These results show that the NG2 molecule is expressed by malignant hematopoietic cells that have abnormalities in chromosome band 11q23, suggesting that antibody 7.1 may be useful in the rapid identification of this group of poor-prognosis patients.

Abnormalities of chromosome band 11q23 and the MLL gene in pediatric myelomonocytic and monoblastic leukemias. Identification of the t(9;11) as an indicator of long survival.

PURPOSE AND METHODS: We reviewed the cytogenetic pattern of the malignant cells in 36 patients who were < 20 years of age and who had M4 and M5 leukemias, excluding M4Eo cases with inv(16). We performed fluorescence in situ hybridization (FISH) and molecular studies to determine the actual incidence of 11q23/MLL abnormalities in these patients. RESULTS: Eighteen patients had 11q23 translocations or insertions detected by cytogenetic analysis (15 cases) or by FISH (3 cases); 10 patients had t(9;11), all of whom had M5a. Eight patients had other 11q23 translocations or insertions not involving chromosome 9[t(11q23)] (four each had M4 or M5 leukemias). Eighteen cases with M4/M5 did not have 11q23 abnormalities. MLL rearrangements were found in all patients with translocations or insertions of 11q23 who were studied. Clinically, children with t(9;11) were indistinguishable from other patients with M4-M5 leukemias. In contrast, the t(11q23) group was characterized by extreme hyperleukocytosis, CNS disease, and skin involvement. Patients with the t(9;11) had a better outcome when compared with patients in the t(11q23) group (EFS +/- SE at 3 years, 56 +/- 17% versus 10 +/- 10%, p = 0.04), and to all the remaining children with M4-M5 leukemias (p = 0.04). CONCLUSIONS: The combination of cytogenetic, FISH, and molecular analysis provides a highly sensitive strategy for detection of 11q23/MLL gene rearrangements in childhood M4-M5 leukemias. Our more precise classification of these patients allows a more accurate correlation with outcome. The favorable prognostic significance of the t(9;11) should be confirmed in prospective studies including a larger number of children as well as adults.