Reciprocal translocation (3;5)(q26;q22) and possible BCHE gene involvement in an unusual myelogenous disorder with both myeloproliferative and dysplastic features

We report on a 77-year-old male patient who presented with an unusual myelogenous disorder exhibiting both myeloproliferative and dysplastic features. The patient suffered from leukocytosis, eosinophilia, basophilia, transfusion dependent anemia, and rapidly progressing thrombocytopenia. Classical chromosome analysis and fluorescence in situ hybridization (FISH) revealed a reciprocal t(3;5)(q26;q22). Using yeast artificial chromosome (YAC) probes, the breakpoint on chromosome 3 was localized to the butyrylcholinesterase (BCHE) gene (3q26.1-q26.2). This gene has recently been implicated in the regulation of myeloid cells. Whether the BCHE gene was also involved in the deregulation of myelopoiesis, causing the unusual clinical picture in this case, remains unknown.

Double induction strategy including high dose cytarabine in combination with all-trans retinoic acid: effects in patients with newly diagnosed acute promyelocytic leukemia. German AML Cooperative Group

A prospective multicenter study was performed to investigate the clinical and molecular results of intensified double induction therapy including high-dose cytarabine (ara-C) in combination with ATRA in newly diagnosed acute promyelocytic leukemia (APL), followed by consolidation and 3 years maintenance therapy. Fifty-one patients, diagnosed and monitored from December 1994 to June 1999, were evaluated. The median age was 43 (16-60) years. The morphologic diagnosis was M3 in 40 (78%) and M3v in 11 (22%) patients. In 15 (30%) patients the initial white blood cell counts were > or =5 x 10(9)/l. The cytogenetic or molecular proof of the translocation t(15;17) was a mandatory prerequisite for eligibility. The diagnosis was confirmed by karyotyping in 46 and by RT-PCR of the PML/RARalpha transcript in 45 cases. The rate of complete hematological remission was 92% and the early death rate 8%. Monitoring of minimal residual disease by RT-PCR of PML/RARalpha (sensitivity 10(-4)) showed negativity in 29 of 32 (91%) evaluable cases after induction, in 23 of 25 (92%) after consolidation, and in 27 of 30 (90%) during maintenance, after a median time of 2, 4 and of 18 months after diagnosis, respectively. After a median follow-up of 27 months, the estimated actuarial 2 years overall and event-free survival were both 88% (79, 97), and the 2 years relapse-free survival 96% (90, 100). The high antileukemic efficacy of this treatment strategy is demonstrated by a rapid and extensive reduction of the malignant clone and by a low relapse rate. The results suggest that the intensity of the induction chemotherapy combined with ATRA is one of the factors which may have a critical influence on the outcome of APL. A randomized trial should assess the value of an induction therapy including ATRA and high-dose ara-C in comparison to standard-dose ara-C.

Mapping of leukaemia-associated breakpoints in chromosome band 3q21 using a newly established PAC contig

Chromosome aberrations affecting band 3q21 are associated with a particularly poor prognosis in patients with acute myeloid leukaemia. To facilitate the molecular characterization of such rearrangements, we established a PAC contig covering the relevant genomic region. Using these PACs as probes in fluorescence in situ hybridization (FISH) experiments, we showed that a number of 3q21 breakpoints in patient samples map to a previously defined 'breakpoint cluster region'. Others, however, are located at varying distances centromeric of it. These results have important implications in the search for genes affected by 3q21 rearrangements.

Low curative potential of bone marrow transplantation for highly aggressive acute myelogenous leukemia with inversioin inv (3)(q21q26) or homologous translocation t(3;3) (q21;q26)

Structural rearrangements of the long arm of chromosome 3 involving bands 3q21 and 3q26 and leading either to a paracentric inversion inv (3)(q21q26) or a translocation between both homologous chromosomes--t(3;3)(q21q26)-- have been reported in patients with acute myelogenous leukemia (AML), myelodysplastic syndromes, myeloproliferative disorders, and chronic myelogenous leukemia in blast crisis. We describe three patients with de novo AML with these structural abnormalities who received multiple courses of conventional chemotherapy followed by unrelated donor (n=2) and autologous (n = 1) bone marrow transplantation (BMT). All three patients had early relapse: patients 1 and 2 had relapse 69 days and 306 days after BMT, respectively, and patient 3 immediately after autologous BMT. Despite further chemotherapy, they died without achieving another remission. These findings, together with other recorded similar cases, show that AML with structural abnormalities of the long arm of chromosome 3 as described has an extremely poor prognosis even with the most potent anti-leukemic treatment modalities.

Three different premature stop codons lead to skipping of exon 7 in neurofibromatosis type I patients

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder affecting one in 3,500 individuals. The mutation rate in the NF1 gene is one of the highest known for human genes. Compared to other methods, the protein truncation test (PTT) provides improved efficiency in detecting NF1 mutations which are dispersed throughout the gene which spans 350 kilobases of genomic DNA. We have applied the PTT and subsequent sequence analysis of cloned cDNA to identify mutations in NF1 patients. We report here the identification of two novel (W336X and Q315X), and one recurrent (R304X) mutation located in exon 7 and show that all three premature termination codons lead to skipping of exon 7 in a proportion of the transcripts derived from the mutated allele. Possible mutation-induced alterations of the RNA secondary structure and their impact on skipping of exon 7 of the NF1 gene are explored and discussed.

Transcription factor GATA-2 gene is located near 3q21 breakpoints in myeloid leukemia

Rearrangements affecting chromosome band 3q21 are observed in a subgroup of patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). However, little is known about the molecular consequences of such aberrations. We therefore established a PAC contig in the 3q21 breakpoint region and identified potential protein coding sequences by exon trapping. One of the exons isolated was from the human GATA-2 gene, which we showed to be transcribed from telomere to centromere. The majority of 3q21 breakpoints are located telomeric to the transcribed portion of this gene in a region that in mice appears to be necessary for proper promoter function. Results of GATA-2 expression analyses in leukemic cell lines as well as primary patient samples are compatible with the hypothesis that 3q21 aberrations contribute to leukemogenesis through deregulation of the hematopoietic transcription factor GATA-2.

Amplification of the MLL gene on double minutes, a homogeneously staining region, and ring chromosomes in five patients with acute myeloid leukemia or myelodysplastic syndrome

Gene amplification is one of the mechanisms for activating proto-oncogenes resulting in an enhanced expression of the corresponding gene product. By fluorescence in situ hybridization (FISH), amplification of the proto-oncogene MLL has been described only in seven patients with acute myeloid leukemia (AML). We report five new patients (four had de novo AML, one had a de novo myelodysplastic syndrome) displaying different mechanisms of MLL amplification, suspected by G-banding and confirmed by FISH analysis. In two patients, MLL was amplified on double-minute chromosomes (dmins). In both cases, an interstitial deletion in 11q23 including the MLL gene was associated with the occurrence of the dmins containing MLL. As a rarely described mechanism, MLL amplification in the form of size-variable ring chromosomes was observed in two patients. Remodeling of the ring chromosomes leads to multiple copies of MLL and obviously provided a selective growth advantage. In one of the two cases with ring chromosomes, the centromeric alpha-satellite DNA of the ring chromosome was not detectable. Our fifth patient showed the unique finding of MLL amplification within a uniformly (homogeneously?) stained region in interaction with amplified ribosomal DNA sequences. Also, one of the patients with ring chromosomes exhibited the amplification of ribosomal DNA on the ring chromosomes. The transcriptionally active genes for ribosomal RNA could probably enhance the expression of MLL. In one of our five patients, we found the new combination of concomitant amplification of the proto-oncogenes MLL and MYC.

Excellent disease eradication by myeloablative therapy and stem-cell transplantation in patients with acute myelogenous leukemia

Between February 1982 and 1999, 118 consecutive patients (65 male, 53 female) with acute myelogenous leukemia (AML), with a median age of 35 years (range 17-56 years), received stem-cell grafts from a human leukocyte antigen-identical sibling (n = 71), one-antigen-mismatched family member (n=2), matched unrelated donor (n=15), one-antigen-mismatched unrelated donor (n = 4) or an autologous (n = 26) graft. At the time of transplant, 56 patients were in the first complete remission (CR), 27 in the second CR, 6 in untreated relapse, 17 in primary refractory, and 12 in refractory relapse. The French-American-British classification (FAB) subtypes were as follows: M1 (n=25), M2 (n=28), M3 (n=11), M4 (n =32), M5 (n=16), M6 (n = 6). For conditioning, most patients underwent total body irradiation-containing regimens. As of 28 February, 1999, probability of leukemia-free survival (LFS) is 58% for patients after related and 45% after unrelated stem-cell transplantation (SCT). The probability of LFS is 70% for patients given allogeneic transplants in the first CR compared with 33% for those beyond the first CR at SCT. In autologous stem-cell graft recipients, the probability of LFS is 37%. Transplant-related mortality was 28% after related, 20% after unrelated, and 4% after autologous SCT. Probability of relapse for patients given related-donor stem-cell grafts in the first CR and beyond the first CR is 30% and 67%, 55% after unrelated and 63% after autologous stem-cell grafting. Thus, myeloablative therapy followed by allogeneic stem-cell infusion has a high curative potential for patients with AML in remission and offers substantial benefits to patients in advanced disease.

Illegitimate splicing of the NF1 gene in healthy individuals mimics mutation-induced splicing alterations in NF1 patients

Neurofibromatosis type 1 (NF1) is a common inherited disease affecting one in 3,500 individuals. The mutation rate in the NF1 gene is one of the highest known for human genes. Compared to other methods, the protein truncation test (PTT) and subsequent sequence analysis of cloned cDNA provides improved efficiency in detecting NF1 mutations that are dispersed throughout the gene spanning 350 kb of genomic DNA. Sequencing of cDNA of patients affected with NF1 mutations revealed multiple splicing errors. Since similar missplicings were also found in "aged" blood of healthy individuals, they are most likely attributable to a general decrease in splice site selection in aged blood. We show that restoring viability of lymphocytes before RNA extraction by cultivation and PHA stimulation diminishes aberrant splicing in aged blood and is thus useful to circumvent splicing alterations which are frequently compromising mutation detection in patient samples and mimic mutation-induced alterations of mRNA.

High concordance of karyotype analysis and RT-PCR for CBF beta/MYH11 in unselected patients with acute myeloid leukemia. A single center study

Identification of the inversion 16 in patients with acute myeloid leukemia (AML) is of great practical value since these patients have a relatively favorable prognosis, especially when treated with high-dose cytarabine. We compared the results of cytogenetic analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) for core binding factor (CBF) beta/myosin heavy chain (MYH11) in 241 unselected cases of AML. In contrast with other studies, we found a high concordance between these 2 methods. Eighteen of 241 patients showed a cytogenetic anomaly of the chromosome 16. We detected the fusion transcript by RT-PCR in all 18 cases and in 2 additional patients with AML without any cytogenetic anomaly of chromosome 16. One patient had a normal diploid karyotype, and the second patient showed a trisomy 22 in karyotype analysis, which often is associated with inv(16). Only 8 of 20 CBF beta/MYH11-positive patients had M4Eo morphologic features. The much higher discrepancy between cytogenetic analysis and RT-PCR in other studies, especially in AMLs other than M4Eo, possibly indicates the necessity for PCR screening regardless of the French-American-British classification.

Molecular analysis of the CALM/AF10 fusion: identical rearrangements in acute myeloid leukemia, acute lymphoblastic leukemia and malignant lymphoma patients

The recurring translocation t(10;11)(p13;q14) which is found in acute myeloid leukemia (AML) and in acute lymphoblastic leukemia (ALL) results in the fusion of the putative transcription factor AF10 to CALM encoding a clathrin assembly protein. Previous studies using mainly fluorescence in situ hybridization (FISH) analysis have shown that the CALM/AF10 rearrangement is found in immature acute myeloid leukemia (AML) of subtype M0 and M1 and in T cell ALL. In this study we analyzed the CALM/AF10 and AF10/CALM fusion mRNAs in a series of three patients with AML, one patient with T-ALL and two patients with precusor T lymphoblastic lymphoma. In all six patients the breakpoint in CALM is at the 3' end of the coding region (nt1926/1927 or nt 2091/2092). Three breakpoints could be identified in AF10 (nt 588/589, nt 882/883 and nt 978/979). These data demonstrate that the CALM/AF10 fusions found in patients differ only slightly with respect to the portion of AF10 present and that there is no obvious difference between the fusions found in AML patients compared to those found in patients with lymphoid malignancies. Leukemia (2000) 14, 93-99.

Drug resistance factors in acute myeloid leukemia: a comparative analysis

To compare the clinical relevance of drug resistance factors in de novo acute myeloid leukemia (AML), we determined their relationship to both response to induction chemotherapy and survival of the patients in univariate as well as multivariate analyses. The drug resistance factors immunocytochemically studied in 111 patients at the time of diagnosis included the lung resistance protein (LRP), P-glycoprotein (P-gp), multidrug resistance protein (MRP1) and bcl-2. In the univariate analyses, age (P = 0.005), karyotype (P = 0.03), LRP (P = 0.003), P-gp (P = 0.02) and bcl-2 (P = 0.03) predicted for response to induction chemotherapy, whereas MRP1 had no predictive value. Age (P = 0.05), karyotype (P = 0.05) and LRP (P = 0.03) retained their predictive value in the multivariate logistic regression analyses. With regard to overall survival, age (P = 0. 008), karyotype (P = 0.006), LRP (P = 0.001) and P-gp (P = 0.01) were of prognostic value in the univariate Cox regression analyses but only age (P = 0.01), karyotype (P = 0.02) and LRP (P = 0.01) retained their prognostic significance in the multivariate analyses. A risk score based on the number of independent prognostic factors allowed division of patients into four groups with different outcome. In these groups, the complete remission rates were 93%, 75%, 47% and 33%, respectively, and median overall survival was 2.4, 1.2, 0.6 and 0.2 years, respectively. Thus, several drug resistance factors did predict outcome in the univariate analyses but LRP was the only drug resistance factor with independent predictive and prognostic significance. The proposed risk score might be useful for risk-adapted treatment in the future. Leukemia (2000) 14, 68-76.

Somatic mosaicism of a greater than 1.7-Mb deletion of genomic DNA involving the entire NF1 gene as verified by FISH: further evidence for a contiguous gene syndrome in 17q11.2

We report on a third case with neurofibromatosis type 1 (NF1) due to mosaicism for a gross deletion in 17q11.2 covering the entire NF1 gene. The deletion was suspected in Giemsa banded chromosomes and was confirmed by fluorescence in situ hybridization using the cosmids CO919 from the 5' region, GO2121 from the central, H10410 from the 3' region of the NF1 gene, and the 1.7-Mb YAC 947G11 spanning the entire 350-kb genomic DNA of the NF1 gene. The deletion was present in 33% of peripheral blood lymphocytes and 58% of fibroblasts. The clinical manifestations in this 6-year-old male patient were especially severe and extended beyond the typical features of NF1. The patient also displayed facial anomalies, severe and early-onset psychomotor retardation, seizures, spasticity, and microcephaly. These features differ from other large-deletion NF1 patients, even nonmosaic cases. The complex phenotype could be explained by the involvement of coding sequences flanking the NF1 gene, thus supporting the existence of a contiguous gene syndrome in 17q11.2.

Management of acute myeloid leukemia in elderly patients

Acute myeloid leukemia (AML) at older age is associated with several biologic and clinical characteristics. Hence, it may arise from an early level of hematopoietic stem cells and has a high frequency of blast cells with multidrug resistance glycoprotein MDR1 expression and particularly a high incidence of poor prognostic karyotypes. These factors, rather than age per se, underlie the poorer outcome as compared with younger cases. Prospective randomized studies clearly demonstrate, however, that elderly patients benefit from more intensive induction therapy and particularly from full-dose application of anthracyclines and possibly also cytarabine. Hematopoietic growth factors accelerate the recovery from treatment-induced neutropenia and may improve the remission rate, remission duration, and even overall survival. New treatment strategies need to be developed, however, for poor-prognosis AML subtypes in order to further improve the therapeutic perspectives for elderly patients with AML.

Monitoring of minimal residual leukemia in patients with MLL-AF9 positive acute myeloid leukemia by RT-PCR

Twenty-seven patients with AML and MLL gene rearrangement were analyzed by a reverse transcriptase polymerase chain reaction (RT-PCR) for the MLL-AF9 translocation. The MLL-AF9 fusion transcript was detected in six patients. In five patients, the breakpoint of the AF9 gene was located within the recently described site A; in one patient, a novel breakpoint (AF9 site D) mapped to a position 377 bp 3' of site A. Five patients could be serially monitored for a period of 4-23 months. Two patients became two-step PCR negative in bone marrow and peripheral blood. Molecular remission was achieved rapidly after one cycle of induction chemotherapy. Both patients are in continuous complete remission (CR) at 22 and 15 months, respectively. Two patients who had achieved hematological CR did not become PCR negative and MLL-AF9 fusion transcripts were detectable in all samples after induction and consolidation chemotherapy. One patient relapsed 5 months after achieving CR. The other patient received allogeneic bone marrow transplantation from an HLA-identical sibling 2 months after achieving hematological CR and became PCR negative 4 weeks after transplantation. In the fifth patient, hematological CR could not be achieved with two cycles of intensive induction chemotherapy, and MLL-AF9 transcripts were present in all samples tested. Our data indicate that MLL-AF9 RT-PCR is specific for the t(9;11) translocation. PCR negativity can be achieved in responding patients already 1 month after induction chemotherapy. The fast reduction of MLL-AF9 positive blast cells below the detection limit of RT-PCR seems to be a prerequisite for long-term CR. The results of RT-PCR may be useful for treatment decisions (eg BMT).

Massive disseminated intravascular coagulation and hyperfibrinolysis in alveolar rhabdomyosarcoma: case report and review of the literature

A 68-year-old woman presented with profuse hemorrhage and other signs suggesting an acute leukemia. Histologic and cytogenetic evaluation of her bone marrow revealed alveolar rhabdomyosarcoma as the underlying cause of massive disseminated intravascular coagulation and hyperfibrinolysis. A review of the literature reveals that coagulopathy appears to be a common feature of alveolar rhabdomyosarcoma.

Successful treatment with arsenic trioxide of a patient with ATRA-resistant relapse of acute promyelocytic leukemia

Arsenic trioxide has recently been introduced as a promising new agent to treat refractory acute promyelocytic leukemia (APL). In the present study, arsenic trioxide was given intravenously for 42 days to a 56-year-old female patient suffering from chemotherapy/ATRA-resistant APL, with 43% APL blasts in the bone marrow and elevated D-dimers. During the first days of arsenic trioxide treatment a rapid decrease in the D-dimers was seen (normal values reached until day 7), together with a slight decrease in peripheral blood leukocytes. This initial coagulation response was followed by a second phase of hematological response (starting on days 15-20) characterized by leukocytosis, occurrence of myeloid progenitor cells in the peripheral blood, and a decrease in bone marrow blasts (<1% on days 28 and 36). Finally, the patient entered complete hematological and cytogenetic remission, although the PML-RAR alpha fusion product was still detectable by PCR. These data confirm the therapeutic value of arsenic trioxide in relapsed/resistant APL.

Myeloid- and lymphoid-specific breakpoint cluster regions in chromosome band 13q14 in acute leukemia

Abnormalities of chromosome band 13q14 occur in hematologic malignancies of all lineages and at all stages of differentiation. Unlike other chromosomal translocations, which are usually specific for a given lineage, the chromosomal translocation t(12;13)(p12;q14) has been observed in both B-cell and T-cell precursor acute lymphoblastic leukemia (BCP-, TCP-ALL), in differentiated and undifferentiated acute myeloblastic leukemia (AML), and in chronic myeloid leukemia (CML) at progression to blast crisis. The nature of these translocations and their pathologic consequences remain unknown. To begin to define the gene(s) involved on chromosome 13, we have performed fluorescence in situ hybridization (FISH) using a panel of YACs from the region, on a series of 10 cases of acute leukemia with t(12;13)(p12;q14) and 1 case each with "variant" translocations including t(12;13)(q21;q14), t(10;13)(q24;q14) and t(9;13)(p21;q14). In 8/13 cases/cell lines, the 13q14 break fell within a single 1.4 Mb CEPH MegaYAC. This YAC fell immediately telomeric of the forkhead (FKHR) gene, which is disrupted in the t(2;13)(q35;q14) seen in pediatric alveolar rhabdomyosarcoma. Seven of the 8 cases with breaks in this YAC were AML. In 4/13 cases, the 13q14 break fell within a 1.7-Mb YAC located about 3 Mb telomeric of the retinoblastoma (RB1) gene: all 4 cases were ALL. One case of myelodysplastic syndrome exhibited a break within 13q12, adjacent to the BRCA2 gene. These data indicate the presence of myeloid- and lymphoid-specific breakpoint cluster regions within chromosome band 13q14 in acute leukemia.

Double induction strategy for acute myeloid leukemia: the effect of high-dose cytarabine with mitoxantrone instead of standard-dose cytarabine with daunorubicin and 6-thioguanine: a randomized trial by the German AML Cooperative Group

Early intensification of chemotherapy with high-dose cytarabine either in the postremission or remission induction phase has recently been shown to improve long-term relapse-free survival (RFS) in patients with acute myeloid leukemia (AML). Comparable results have been produced with the double induction strategy. The present trial evaluated the contribution of high-dose versus standard-dose cytarabine to this strategy. Between March 1985 and November 1992, 725 eligible patients 16 to 60 years of age with newly diagnosed primary AML entered the trial. Before treatment started, patients were randomized between two versions of double induction: 2 courses of standard-dose cytarabine (ara-C) with daunorubicin and 6-thioguanine (TAD) were compared with 1 course of TAD followed by high-dose cytarabine (3 g/m2 every 12 hours for 6 times) with mitoxantrone (HAM). Second courses started on day 21 before remission criteria were reached, regardless of the presence or absence of blast cells in the bone marrow. Patients in remission received consolidation by TAD and monthly maintenance with reduced TAD courses for 3 years. The complete remission (CR) rate in the TAD-TAD compared with the TAD-HAM arm was 65% versus 71% (not significant [NS]), and the early and hypoplastic death rate was 18% versus 14% (NS). The corresponding RFS after 5 years was 29% versus 35% (NS). An explorative analysis identified a subgroup of 286 patients with a poor prognosis representing 39% of the entire population; they included patients with more than 40% residual blasts in the day-16 bone marrow, patients with unfavorable karyotype, and those with high levels of serum lactate dehydrogenase. Their CR rate was 65% versus 49% (p =.004) in favor of TAD-HAM and was associated with a superior event-free survival (median, 7 v 3 months; 5 years, 17% v 12%; P =.012) and overall survival (median, 13 v 8 months; 5 years, 24% v 18%; P =.009). This suggests that the incorporation of high-dose cytarabine with mitoxantrone may contribute a specific benefit to poor-risk patients that, however, requires further substantiation. Double induction, followed by consolidation and maintenance, proved a safe and effective strategy and a new way of delivering early intensification treatment for AML.

Results of a randomized double-blind placebo-controlled trial evaluating sequential high-dose cytosine arabinoside/mitoxantrone chemotherapy with or without granulocyte/macrophage-colony-stimulating factor in high-risk myelodysplastic syndromes

A prospective, randomized, double-blind placebo-controlled trial was designed to evaluate the impact of granulocyte/macrophage-colony-stimulating factor (GM-CSF) on the efficacy of sequential high-dose cytosine arabinoside/mitoxantrone chemotherapy (S-HAM) in adult patients with high-risk myelodysplastic syndromes (MDS). GM-CSF or placebo was given subcutaneously once daily at a dose of 250 microg/m2, starting 48 h prior to chemotherapy, and continued until neutrophil recovery. Owing to high toxicity and slow patient recruitement the study was closed and unblinded after 31 patients had been enrolled; 15 were randomized to receive placebo and 16 to receive GM-CSF. A total of 29 patients were evaluable for response; their median age was 57 years. Ten patients achieved a complete remission (34.5%), 9 patients had persistent MDS (31%), 10 patients died within 6 weeks after the onset of treatment (early death) (34.5%). The median remission duration was 190 days (range: 2.5-45 months). Among the 29 evaluable patients no significant differences could be found between the two study arms regarding complete remission rate [GM-CSF: 31% (5/16) versus placebo: 38% (5/13) P = 0.45], rate of persistent MDS [GM-CSF: 25% (4/16) versus 38% (5/13) P = 0.35), early death rate [44% (7/16) versus 23% (3/13) P = 0.22] and remission duration (GM-CSF: 87 days versus placebo 221 days). Duration of granulocytopenia (median: 33 days with GM-CSF) versus 35 days with placebo) and frequency of infectious episodes were not significantly influenced by GM-CSF. The small number of patients finally analyzed means that no definite conclusions about the effect of GM-CSF can be reached.

Expression of the C-kit receptor (CD117) is a feature of almost all subtypes of de novo acute myeloblastic leukemia (AML), including cytogenetically good-risk AML, and lacks prognostic significance

Because of conflicting reports on the prognosis of patients with c-kit receptor positive AML and lacking correlations with cytogenetic analyses, we prospectively evaluated the c-kit receptor expression in 917 AML patients (750 adult patients; 167 children) using flow cytometry and compared the results to the immunophenotype, morphological and cytogenetic findings as well as clinical outcome. Expression of the c-kit receptor was present in 63% of all AML investigated. Among these an immature immunophenotype was more frequent and 30% had a CD34+/CD15- and 37% a CD34+/CD14- phenotype, whereas only 9% and 10% showed these phenotypes in the c-kit receptor negative group, respectively. C-kit receptor expression ranged average in M0 and M1 subtypes (69% versus 70%) but was less pronounced among M5 subtypes (21%). Results of karyotyping were available in 280 patients. C-kit receptor expression occurred in 37 of 42 (88%) patients with favorable cytogenetic abnormalities such as t(8;21), t(15;17) or inv(16) which exceeded the expression rate in patients with intermediate risk, poor risk or other abnormalities. Information about the clinical outcome was available in 228 patients treated according to the protocols of two German multicenter trials (AML-BFM, AMLCG). We found no difference of CR-rate or event-free survival (EFS) in adults with or without c-kit receptor expression. Children with c-kit receptor negative AML had a lower CR-rate and EFS, but also a lower median age and a higher frequency of M5 subtype as compared to children with c-kit receptor expression. In conclusion, analysis of c-kit receptor expression may help to identify phenotypically immature AML but fails to identify myeloid differentiation of leukemic blasts in approximately one third of patients. We found no evidence of an adverse prognosis in AML patients with c-kit receptor expression. Analysis for c-kit receptor expression does not appear to add information to established prognostic parameters in AML.