ALBERT

Description: Abstract 3468 Poster Board III-356 Background Transcription factor RUNX1 is essential for normal hematopoiesis. RUNX1 mutations, mainly at Runt homology domain (RHD), have been described in patients with AML-M0 and were rarely found in non-M0 AML. Aim We aimed to analyze the RUNX1 mutations in AML patients with partial tandem duplication of MLL (MLL-PTD) and to investigate the biological functions of the mutants detected. Patients and methods Bone marrow samples from 93 patients with MLL-PTD were analyzed for RUNX1 mutations. MLL-PTD was screened by Southern-blot analysis followed by RT-PCR or detected by real-time quantitative PCR. Mutational analysis of RUNX1 gene was performed by sequencing of all RT-PCR products amplified from exon 3 through exon 8. Each mutation was reconfirmed with alternative primers. The wild-type, all mutants of RUNX1 (except those truncated at RHD or silent) and pcDNA3.1 were transiently transfected into Cos-7 cells. Immunoblot analysis after immunoprecipitation with anti-FLAG RUNX1 antibody and electrophoretic mobility shift assay were used to determine the interaction with CBFβ and DNA-binding ability of the RUNX1 mutants. Dual luciferase assay system was used to analyze the transactivation potential of RUNX1 mutants in K562 cells. Results RUNX1 mutations were detected in 23 patients (24.7%) at diagnosis, with 3 patients carrying double mutations; 14 mutations were located in RHD (exons 3-5) and 12 at C-terminal region (exons 6-8). In addition, one patient acquired a C-terminal mutation at relapse. The patterns of 27 mutations consisted of 6 missense mutations, 3 nonsense mutations, 17 frame-shift mutations, and 1 silent mutation; all were heterozygous. Of the 3 patients with double mutations, clonal analysis showed that one patient had combined missense and frame-shift mutations on the same allele, the other patient had two missense mutations on different alleles, and another patient had a missense mutation and a silent mutation on the same allele. Functional analyses revealed significant difference among mutants. Two missense RUNX1 mutants at RHD (G108D and R174L) and all of the frame-shift mutants in the transactivation domain (TAD) ( S287fsX571, S295fsX571, L300fsX570, V333fsX574, I339fsX569 and P355fsX572) exhibited lack of DNA-binding ability and inhibited transactivation activity of wild-type RUNX1 in a dominant-negative effect. All frame-shift mutants distal to the TAD generated termination codons within the 3'-untranslated region (H377fsX565, Q388fsX572, L414fsX569, L414fsX567 and V425fsX576), they all retained the normal transactivation activity as the wild-type. R177X and R205W retained the ability of heterodimerization with CBFβ but they had markedly reduced DNA-binding and no transactivation potential without inhibitory effect on wild-type RUNX1. L183fsX185 could bind DNA but lacked transactivation activity. S114P and Q370R had normal transactivation activity. Conclusions Our results showed that patients with de novo AML with MLL-PTD had a high frequency of frame-shift mutations at C-terminal region of RUNX1; those within TAD had dominant-negative effects whereas those distal to TAD retained the normal transactivation potential. Supported by grants NHRI-EX96-9434SI, NSC97-2314-B-182 -011-MY3 and MMH-E-96009. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4019 Background. The molecular pathogenesis of myelodysplastic syndrome (MDS) and its role in the progression to secondary acute myeloid leukemia (sAML) remain to be further explored. Somatic TET2 and C-CBL mutations have recently been described in myeloid neoplasms including MDS and sAML. Most studies of TET2 or C-CBL mutations were carried out separately either at MDS or at sAML phases. There was also a discrepancy in the results of the impact of TET2 and C-CBL mutations on outcome of MDS patients. Aims. We aimed (1) to correlate the TET2 and C-CBL mutations with clinicohematological features and outcome, and (2) to determine the role of TET2 or C-CBL gene mutations in sAML derived from MDS. Materials and Methods. Bone marrow (BM) samples from 161 MDS patients (3 RCUD, 1 RARS, 36 RCMD, 118 RAEB, 1 MDS5q-, 2 MDS-U) at initial diagnosis were analyzed for both TET2 and C-CBL mutations; 49 of them had matched paired sAML BM samples available for comparative analysis. Mutational analysis was performed by DHPLC and/or direct sequencing of all RT-PCR or DNA-PCR products amplified with different primer pairs covering the whole coding sequences of TET2 and exons 7 to 9 of C-CBL. Results. The frequency of TET2 and C-CBL mutations in 161 MDS patients was 17.9 % and 1.9 %, respectively. Seven patients with polymorphism/germ line mutations or missense mutations outside of BOX 1 or 2 of TET2 gene were excluded. Of the 26 patients with 38 TET2 mutations, 14 had nonsense, 11 missense, 11 frameshift, 1 deletion, and 1 splice site mutations; 12 of them had double mutations. Three patients had C-CBL mutations (Y371S, F418S and G415S) at MDS phase. No patient had coexistence of TET2 and C-CBL mutations. TET2 mutations were significantly associated with increased risk of AML transformation (P= 0.037), whereas C-CBL mutations did not influence the risk of AML transformation (P=0.335). Patients carrying TET2 mutations had a trend of shorter time to sAML compared with those without TET2 mutations (estimated median time to sAML 8.7 months vs 15.0 months, P=0.067). Except for lower platelet count in patients with TET2 mutations (P=0.038), there were no significant differences in clinicohematological features including age, sex, hemoglobin level, white blood cell count, percentage of blasts in BM or peripheral blood, cytogenetics or IPSS (≤1.5 vs ≥2.0) between patients with and without TET2 or C-CBL mutations. No significant differences were found in overall survival with respect to mutation status of TET2 (P= 0.244) or C-CBL (P= 0.646). Of the 49 paired BM samples, 3 patients harboring C-CBL mutations at MDS phase retained the identical mutations and another 3 acquired C-CBL mutations (L370_Y371 ins L, L399V and C416W) during sAML evolution. There was an increased risk of acquiring C-CBL mutations during AML transformation (odds ratio=4.16, P=0.041), whereas TET2 mutation patterns remained unchanged and none acquired or lost TET2 mutations in sAML progression. Conclusions. Our results showed an increased risk of acquiring C-CBL mutations during sAML transformation. TET2 mutations played a role as an initial event in the development of MDS in a subset of patients and were associated with more frequent and rapid sAML evolution. Supported by grants NHRI-EX99-9711SI, NSC97-2314-B-182-011-MY3 and DOH99-TD-C-111-006. Disclosures: No relevant conflicts of interest to declare.

Description: Two-hit model of leukemogenesis has been proposed for AML. In AML with MLL rearrangements (MLL-R), MLL gene is fused to a variety of partner genes through reciprocal chromosomal translocations (MLL/t11q23), or is rearranged to generate a partial tandem duplication (MLL-PTD). The cooperating mutations of AML with MLL-R have not been systematically analyzed. We aimed to determine the cooperating mutations, including receptor tyrosine kinase (RTK) /Ras signaling pathway, NPM1 and myeloid transcription factors in de novo AML with MLL-R. MLL-R was screened by Southern blot analysis. RT-PCR was used to detect common MLL fusion transcripts. cDNA panhandle PCR was used to identify the infrequent or unknown MLL partner genes. Mutational analysis was peformed by DNA/cDNA PCR-GeneScan analysis for FLT3/ITD, by PCR-RFLP followed by direct sequencing for FLT3/TKD, by DNA/cDNA PCR and direct sequencing for N-Ras, K-Ras, c-KIT, c-FMS, PTPN11, NPM1, AML1 and CEBPα. Of the 131 patients with MLL-R, 77 had MLL-PTD and 54 had MLL/t11q23. None of the 131 patients with MLL-R had c-FMS mutations and c-KIT mutation was present in only one patient with MLL/t11q23. NPM1 mutations occurred in one with MLL-PTD and 2 with MLL/t11q23. The frequencies of other cooperating mutations are shown in Table 1. Taken together, cooperating mutations involving RTK/Ras pathway, NPM1, and/or myeloid transcription factors occurred in 71.4% (55/77) of patients with MLL-PTD and 59.3% (32/54) of patients with MLL/t11q23. In MLL-PTD group, coexistence of two mutations occurred in 23 patients. In MLL/t11q23 group, 6 patients had two mutations. Of the 18 patients with MLL-PTD and AML1 mutations, 8 mutations were located in the Runt homology domain (RHD) and 10 in the non-RHD, 15 were frameshift or nonsense mutations and 3 were missense mutations. Fourteen patients with MLL-PTD and AML1 mutations also had mutations of RTK/Ras singling pathway. Three patients with MLL/t11q23 and AML1 mutations, one in the RHD and 2 in the non-RHD, all were missense mutations. Of the 5 patients with MLL-PTD and CEBPα mutations, 3 harbored FLT3/ITD. Patients with MLL-PTD had a significantly higher frequency of cooperating mutations with myeloid transcription factors than patients with MLL/t11q23 (20/77 vs. 3/54, P=0.002), whereas there was no difference in the frequency of mutations involving RTK/Ras pathway between MLL-PTD and MLL/t11q23 groups (51/77 vs. 29/54, P=0.202). Our results showed that patients with de novo AML and MLL-R had a high frequency of cooperating mutations with RTK/Ras signaling pathway, NPM1 or myeloid transcription factors, and the mutation patterns were different between MLL-PTD and MLL/t11q23 groups. Table 1. Comparison of cooperating mutations between MLL-PTD and MLL/t11q23 groups FLT3/ITD FLT3/TKD N-Ras K-Ras PTPN11 AML1 CEBPα MLL-PTD 35/77 11/77 5/77 0/77 3/77 18/77 5/77 MLL/t11q23 2/54 7/54 9/54 13/54 1/53 3/54 0/54 P value

Description: C-KIT is a member of the type III receptor tyrosine kinase family and plays a crucial role in normal hematopoiesis and acute myeloid leukemia (AML). C-KIT mutations have been described in core-binding factor (CBF) AML at initial diagnosis. The role of C-KIT mutations in the relapse of CBF AML is not clear. In the present study, we analyzed C-KIT mutations on paired diagnosis and relapse samples in CBF AML. Among 1014 adults and 162 children with AML, CBF AML was detected in 11.4% of adults and 25.3% of children. Mutational analysis of C-KIT was performed by direct sequencing for all cDNA PCR products amplified with 5 overlapping primer pairs, which cover the whole coding sequences of C-KIT gene from exon 1 through exon 21. In AML with t(8;21)/AML1-ETO, 33.0 % (29/88) of adults and 44.4 % (12/27) of children had C-KIT mutations. In AML with inv(16)/CBFβ-MYH11, 22.2 % (6/27) of adults and 38.5 %(5/13) of children had C-KIT mutations. Taken together, C-KIT mutations were present in 30.4 % (35/115) of adults and 42.5 % (17/40) of children with CBF AML. Forty-two patients with CBF AML relapsed. Twenty-two(18 adults and 4 children) of the 23 patients with CBF AML and C-KIT(+) at diagnosis had relapse samples available for comparative analysis. All the 22 patients relapsed with C-KIT mutations, 21 of them showed the identical C-KIT mutation patterns as those at diagnosis. Of the 20 relapsed patients with t(8;21)/AML1-ETO and C-KIT(+), 3 had mutations in exon 8: T417_D419delinsY, Y418_D419delinsA, and [Y418N;Y418_D419insFF], respectively; one had mutation in exon 9: I478V; another one had mutation in exon 11: [D572_P573insL; E561_D572dup]; 14 had mutations in exon 17: 5 D816V, 3 N822K, 3 D816Y, and one each with D816H, D820G, and D820Y; the remaining one patient relapsed twice, the patterns of C-KIT mutations changed but remained in exon 17: D816A at diagnosis, D816V at the first relapse, and N822K at the second relapse. Genotyping analysis with 15 loci of short tandem repeats at 13 different chromosomes showed identity for the diagnosis and the two relapse samples. Of the 2 adults with inv(16)/CBFβ-MYH11 and C-KIT(+) who relapsed, both had mutations in exon 17: N822K and D816Y, respectively. C-KIT mutations were absent in all of the 35 complete remission samples examined. In those with CBF AML and C-KIT(−) at diagnosis, 19 patients including 16 adults and 3 children relapsed; C-KIT mutations were not present in all the relapse samples except one who acquired D816H mutation. The present study showed that all patients with de novo CBF AML harboring C-KIT mutations at diagnosis retained the mutations at relapse, indicating that C-KIT mutations play a crucial role in the leukemogenesis in a substantial proportion of patients with CBF AML.

Description: The MLL gene, located at chromosome 11q23, is fused to a variety of partner genes through chromosomal translocations in 5–10% of acute leukemias. Partial tandem duplication (PTD) of MLL gene (MLL-PTD) has been described in 10% of AML with normal karyotype. Recently, 2-hit model of leukemogenesis has been proposed for AML. However, the cooperating mutations with MLL translocations (MLL-T) or MLL-PTD have not been systematically analyzed. In the present study, we aimed to identify the fusion partners of MLL and to analyze the cooperating mutations, including FLT3 activation mutations, N-ras and CEBPα mutations in de novo AML with MLL rearrangements. The correlation between MLL fusion transcripts and clinicohematological features was also analyzed. Southern blot analysis identified 92 patients with MLL rearrangements. Their ages ranged from one day to 84 years; 44 were male. The distribution of FAB subtypes was 4 M0, 19 M1, 19 M2, 22 M4, 25 M5, 1 M6, and 2 M7. Standard RT-PCR or multiplex RT-PCR followed by Genescan analysis and/or direct sequencing, was used to detect the common MLL fusion transcripts. MLL-PTD was detected in 46 (50.0%), MLL-AF9 in 13, MLL-AF10 in 9, MLL-AF6 in 8, MLL-ELL in 7, MLL-ENL in 2, and MLL-AF1 and MLL-AF4 in one patient each. In addition, 5 rare MLL fusion transcripts, including MLL-LCX, MLL-SEPT6, MLL-CBL, MLL-MSF and MLL-LARG in one patient each, were characterized by cDNA panhandle PCR and/or long distance inverse PCR. Cytogenetic findings were available in 76 patients with MLL rearrangements, 11q23 abnormalities were detected in 27 patients. By PCR-Genescan analysis and direct sequencing, FLT3-ITD mutations were detected in 21 patients with MLL rearrangements. By PCR-RFLP and sequencing, FLT3-TKD mutations were detected in 12 patients. By DNA PCR and direct sequencing, CEBPα and N-ras mutations were found in 1 and 9 patients, respectively. Coexistence of FLT3-ITD and FLT3-TKD mutations was observed in 2 patients, FLT3-ITD and CEBPα mutations in one patient, and FLT3-TKD and N-ras mutations in another one patient. Taken together, cooperating mutations of FLT3 and/or N-ras mutations occurred in 42% (39/92) of AML with MLL rearrangements. The frequency of FLT3-ITD was significantly higher in patients with MLL-PTD than those with MLL-T (P

Description: Abstract 1002 Poster Board I-24 Background and purpose: Overexpression of BAALC, MN1, or ERG gene has been described to have adverse impact on the outcome of acute myeloid leukemia (AML) with normal karyotype. The majority of patients with partial tandem duplication of MLL gene (MLL-PTD) had normal karyotypes. The prognostic relevance of overexpression of these genes in MLL-PTD AML was not clear. Aims: We aimed to (1) measure the mRNA expression levels of FLT3, BAALC, FHIT, MN1, and ERG genes in AML patients with MLL-PTD (2) compare the expression levels of these genes with normal controls, and (3) determine their prognostic significance. Patients and methods: Bone marrow samples from 93 de novo AML patients with MLL-PTD at diagnosis were analyzed. MLL-PTD was screened by Southern blot analysis or reverse transcriptase polymerase chain reaction (RT-PCR) then confirmed by real-time quantitative PCR (RQ-PCR). RQ-PCR assay with TaqMan probe was performed to measure the expression of FLT3, BAALC, FHIT, MN1, and ERG genes in MLL-PTD AML as well as in 34 normal controls for comparison. The expression levels of target genes were calculated as the copy number of each gene normalized to the copy number of ABL control gene (NCN). Positive and negative controls as well as standard curve constructs were included in each assay. Mutational analysis was performed by DNA/cDNA PCR followed by GeneScan analysis for detection of internal tandem duplication of FLT3 gene (FLT3/ITD). The expression levels of each target genes were dichotomized at the median value to low and high expression groups. The event-free and overall survivals (EFS and OS) were compared between the 2 groups. Results: The expression levels of mRNAs for FLT3, BAALC, FHIT, MN1, and ERG genes at diagnosis in MLL-PTD AML and 34 normal controls are shown in Table. MLL-PTD patients had significantly higher expression levels of FLT3, BAALC, MN1, and ERG compared to normal controls. The expression of FHIT was also higher than that of controls, but did not reach statistic significance. FLT3/ITD was present in 26 of 52 patients (50%). The expression levels of the above genes were not different between patients with FLT3/ITD and those without. The median age of the entire cohort was 56 years. The median EFS and OS of the 52 patients who received standard induction chemotherapy were 5.8 and 11.4 months, respectively. The complete remission (CR) rate was higher in the low expression group than that of high expression group for BAALC (P = 0.011). The CR rate was not significantly different between low and high expression groups for FLT3, FHIT, MN1, or ERG, and between FLT3/ITD(+) and (-) groups. There were no significant difference in EFS or OS between patients with FLT3/ITD and those without. Patients with high expression of BAALC had a significantly shorter survival than those with low expression group; the median EFS was 10.3 mons (95% CI: 5.9-14.7 mons) vs. 0 mon, P = 0.044 and the median OS was 16.4 mons (95% CI: 8.3-25.5 mons) vs. 10.9 mons (95% CI: 6.5-15.3 mons), P = 0.031. Patients with high expression of MN1 also had a poor outcome compared with low expression group; the median EFS was 10.9 mons (95% CI: 0-28.3 mons) vs. 4.1 mons (95% CI: 0-11.7mons), P = 0.002 and the median OS was 29.7 mons (95% CI: 0-70.7mons) vs.11.0 mons (95% CI: 10.7-11.3 mons), P = 0.024. The EFS and OS were not significantly different between low and high expression groups for FLT3, BAALC, FHIT, and ERG. Conclusions: Our results showed that MLL-PTD was associated with overexpression of FLT3, BAALC, MN1, and ERG. The patients with lower expression level of BAALC had a higher CR rate and patients with overexpression of BAALC or MN1 had poor EFS and OS. FLT3/ITD had no prognostic impact. Supported by grants NSC97-2314-B-182 -011-MY3, NSC96-2314-B-195-006-MY3, and MMH-E-96009. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2713 Background. The cooperation of gene mutations, especially their impacts on survivals of childhood acute myeloid leukemia (AML) has not been well known. Aims. Our aims were (1) to study the frequency of each gene mutation in childhood AML, (2) to study the impact of each gene mutation on the treatment outcome, and (3) to examine the cooperativity of gene mutations. Materials and Methods. From Feb. 1996 to Jan. 2010, bone marrow samples at diagnosis from 198 children with AML at Chang Gung Children's Hospital, Taoyuan and Mackay Memorial Hospital, Taipei, were analyzed for gene mutations including FLT3-ITD, FLT3-TKD (D835), c-KIT, cFMS, JAK 2V617F, NRAS, KRAS, PTPN11 (Class I mutations), RUNX1, CEBPα, NPM1 (Class II mutations), WT1 and P53 (tumor suppressor genes). The subtypes included: t(8;21) 19.9%, inv(16) 8.9%, t(15;17) 8.4%, t(9;11) 5.2%, t(10;11) 2.6%, trisomy 21 4.2%, intermediate-risk group 40.3% (including 13 patients with other MLL translocations), and poor-risk group 11.0% (including 7 patients with complex chromosomal abnormalities and 4 patients with MLL-PTD). Results. FLT3-ITD occurred in 15.0% of patients, FLT3-TKD 7.2%, c-KIT 11.5%, c-FMS 2.9%, JAK2V617F 3.3%, NRAS 9.1%, KRAS 7.7%, PTPN11 3.3%, RUNX1 2.7%, CEBPα 7.9%, NPM1 4.1%, WT1 3.9% and P53 1.7%. Taken together, 52.5% of patients had Class I gene mutations, 13.1% had Class II gene mutations, and 5.1% had WT1 or P53 mutations. In all, 59.1% of patients had Class I, Class II or tumor suppressor gene mutations. Only one patient (0.5 %) had gene mutations involving all Class I, Class II and tumor suppressor genes. Ninety-eight patients, who were treated with Taiwan Pediatric Oncology Group (TPOG) APL protocols (for acute promyelocytic leukemia) and TPOG 97A protocol (for other AML) (Liang et al, Leukemia 2006), were analyzed for survivals. In patients with t(8;21), the 5-year event-free survival (EFS) was 66±12%; 71±17% for patients with c-KIT mutations and 50±35% for the 2 patients with JAK2V617F. In patients with inv(16), the EFS of 70±15% seemed to be compromised (60±22%) for those with c-KIT mutations. In patients with t(15;17), the EFS of 78±11% was not compromised by FLT3-ITD or FLT3-TKD mutations. In patients with t(9;11), the EFS of 64% seemed to be compromised (50±35%) in the 2 patients with FLT3-TKD mutations. In 3 patients with t(10;11), no gene mutations were found. In trisomy 21, the EFS of 75±22% seemed to be compromised (50±35%) in the 2 patients with CEBPα mutations. Of the 5 patients with complex chromosomal abnormalities, the only one patient carrying RUNX1 survived. Of the 3 patients with MLL-PTD having an EFS of 33±27%, one each patient with c-FMS or WT1 mutation died. The only one patient who had all Class I, Class II and tumor suppressor gene mutations (FLT3-TKD+ CEBPα+ WT1) died in induction therapy. Two of the other 4 patients who had 3 mutations acrossing 2 classes had EFS of 6 and 10 months, respectively. Conclusions. Our study on a large cohort of pediatric AML patients revealed that 59.1% patients had at least one gene mutation. That 3 of 5 patients who had 3 gene mutations soon failed suggested that gene mutations, especially in 3 combinations, might compromise the survival. Further study on more patients is warranted to explore more of the prognostic significance of cooperating gene mutations in pediatric AML. (Supported by grants MMH-E-98009, NSC 96–2314-B-195-006-MY3, NHRI-EX-96-9434SI and DOH99-TD-C-111-006.) Disclosures: No relevant conflicts of interest to declare.

Description: Essential thrombocythemia (ET) is a heterogeneous disorder in which the clonality of hematopoiesis varies. The clinical significance of clonality status in ET remains to be determined. We used the human androgen receptor gene (HUMARA)–polymerase chain reaction assay to investigate X-chromosome inactivation patterns (XCIPs) and their value in predicting vascular complications in 89 female patients with ET. Fifty-four (68.4%) patients had a clonal pattern of XCIP, and 15 (19.0%) had a polyclonal pattern. The remaining 20 patients had either an ambiguous or a homozygous pattern of XCIP and were therefore excluded from further analysis. Patients with clonal XCIPs were older (P = .029) and were at greater risk for thrombosis (P = .007) than were those with polyclonal XCIPs. We did not find a correlation between the occurrence of hemorrhage and XCIP (P = .492). Advanced age was predictive of thrombosis and hemorrhage. Platelet count did not influence the risk for vascular complications. Hypertension was significantly correlated with thrombotic events (P = .002), whereas diabetes mellitus and hypercholesterolemia were of no predictive value. In a multivariate analysis, age was the significant predictor of thrombosis (P = .030); however, XCIPs (P = .083) and hypertension (P = .073) tended to predict thrombosis. Our results suggest that older patients who have clonal XCIPs or hypertension are at increased risk for thrombosis and should be monitored closely for this complication.

Description: Background. Two-hit model of leukemogenesis has been proposed for AML; class I mutations that drive proliferation and survival, and class II mutations that block differentiation. Core-binding factor (CBF) AML consists of AML with AML1-ETO and AML with CBFβ-MYH11, that are class II mutations. Aim. We sought to determine the frequencies of cooperating mutations of class I including receptor tyrosine kinases (RTK)/Ras/JAK2 signaling pathways in CBF-AML, and to compare the patterns of cooperating mutations between AML with AML1-ETO and AML with CBFβ-MYH11. Patients and methods. By RT-PCR analysis, 130 adult and 45 children were identified to have CBF-AML, 129 with AML1-ETO and 46 with CBFβ-MYH11. Bone marrow samples at diagnosis were analyzed for FLT3-LM, FLT3-TKD, c-KIT, c-FMS, N-ras, K-ras and JAK2 mutations. Results. Sixty-six of 129 patients (51.2%) with AML1-ETO had RTK/Ras/JAK2 mutations compared with 30 of 46 patients (65.2%) with CBFβ-MYH11 (p=0.121). The frequencies of RTK/Ras/JAK2 mutations in 129 AML1-ETO AML were 3.9% (n=5) for FLT3-LM, 6.2% (n=8) for FLT3-TKD, 2.3% (n=3) for N-ras, 3.9% (n=5) for K-ras, 35.7% (n=46) for c-KIT, and1.6% (n=2) for JAK2 mutation. The frequencies of RTK/Ras/JAK2 mutations in 46 CBFβ-MYH11 AML were 2.2% (n=1) for FLT3-LM, 19.6% (n=9) for FLT3-TKD, 21.7% (n=10) for N-ras, 23.9% (n=11) for c-KIT, and none for K-ras or JAK2 mutations. No c-FMS mutations were detected in both subtypes of CBF-AML. All RTK/Ras/JAK2 mutations were mutually exclusive except three, one each with N-ras and K-ras mutations, FLT3-TKD and c-KIT mutations, c-KIT and JAK2 mutations, respectively. Patients with CBFβ-MYH11 had a significantly higher frequency of FLT3-TKD and N-ras mutations than patients with AML1-ETO (p=0.017 for FLT3-TKD, and p

Description: Analysis of internal tandem duplications of FLT3(FLT3/ITD) was performed on bone marrow samples obtained at diagnosis and relapse from 108 adult patients with de novo acute myeloid leukemia (AML) to determine the role of this mutation in leukemic relapse. Eighty-three patients had wild-type FLT3at both diagnosis and relapse, 16 had FLT3/ITD at both stages, whereas 8 had acquired the mutation and 1 had lost it at relapse. Using Genescan analysis, we found that FLT3/ITD levels at first relapse were significantly higher than those at diagnosis (mean ± SE, 40.5% ± 4.8% versus 17.9% ± 3.6%,P