Internal tandem duplication and Asp835 mutations of the FMS-like tyrosine kinase 3 (FLT3) gene in acute promyelocytic leukemia.
BACKGROUND
The clinical relevance of mutations of the FMS-like tyrosine kinase 3 (FLT3) gene in specific cytogenetic subgroups is not clear. The authors examined internal tandem duplication (ITD) and Asp835 mutations of FLT3 in patients with acute promyelocytic leukemia (APL) to determine the incidence of these mutations and to analyze the results for correlations with clinicohematologic features and outcome.


METHODS
Bone marrow samples from 107 patients with APL were analyzed. Isoforms of PML-RAR alpha were identified using a reverse transcription-polymerase chain reaction assay. A standard polymerase chain reaction (PCR) assay was used to detect FLT3/ITD mutations. Asp835 mutations were analyzed by PCR amplification of exon 20 followed by EcoRV digestion. All aberrant PCR products subsequently were sequenced.


RESULTS
Twenty-two patients had FLT3/ITD mutations: 9 of 63 patients with L-type PML/RAR alpha, 13 of 34 patients with S-type PML/RAR alpha, and 0 of 10 patients with V-type PML/RAR alpha (P = 0.005). The incidence of FLT3/ITD mutations was significantly higher in patients with S-type PML/RAR alpha than in patients with L-type PML/RAR alpha or V-type PML/RAR alpha. Twenty patients had Asp835 mutations (L-type PML/RAR alpha: n = 11; S-type PML/RAR alpha: n = 8; V-type PML/RAR alpha: n = 1). The frequency of Asp835 mutations was not significantly different among patients with different PML/RAR alpha isoforms (P = 0.582). Three patients had both ITD and Asp835 mutations. The microgranular variant (M3v) form of leukemia was found to be associated with a higher frequency of ITD (P = 0.002) but not with a higher frequency of Asp835 mutations (P = 1.000); analysis of clinicohematologic variables revealed no significant differences in FLT3 mutation incidence among other patient subgroups. There was no significant difference in complete remission rate, overall survival, or event-free survival between patients with ITDs and those without ITDs or between patients with Asp835 mutations and those without Asp835 mutations.


CONCLUSIONS
The current study found that ITD or Asp835 mutations of the FLT3 gene were present in 36.4% of patients with APL; however, these mutations had no prognostic impact. FLT3/ITD frequently was associated with S-type PML/RAR alpha and with the M3v form of leukemia.
Shih
Lee-Yung
LY
Department of Internal Medicine, Chang Gung Memorial Hospital, Taipei, Taiwan. sly7012@adm.cgmh.org.tw
Kuo
Ming-Chung
MC
Liang
Der-Cherng
DC
Huang
Chein-Fuang
CF
Lin
Tung-Liang
TL
Wu
Jin-Hou
JH
Wang
Po-Nan
PN
Dunn
Po
P
Lai
Chang-Liang
CL
D000328:Adult; D001224:Aspartic Acid / Q000235:genetics; D002648:Child; D005260:Female; D020440:Gene Duplication; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D012008:Recurrence; D016896:Treatment Outcome; D051941:fms-Like Tyrosine Kinase 3
D011518:Proto-Oncogene Proteins; D001224:Aspartic Acid; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3