FLT3 mutations in acute myeloid leukemia cell lines

• Published in: Leukemia 2003-01, Vol.17 (1), p.120-124
• Main Authors: Quentmeier, H, Reinhardt, J, Zaborski, M, Drexler, H G
• Format: Article
• Language: English
• Subjects: Acute Disease; Base Sequence; Biological and medical sciences; Blotting, Western; Cancer Research; Cell Transformation, Neoplastic - genetics; Critical Care Medicine; DNA-Binding Proteins - metabolism; fms-Like Tyrosine Kinase 3; Gene Expression Regulation, Leukemic; Hematologic and hematopoietic diseases; Hematology; Humans; Intensive; Internal Medicine; Leukemia, Myeloid - genetics; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Medical sciences; Medicine; Medicine & Public Health; Milk Proteins; Molecular Sequence Data; Oncology; original-manuscript; Phosphorylation; Phosphotyrosine - immunology; Phosphotyrosine - metabolism; Point Mutation - genetics; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Receptor Protein-Tyrosine Kinases - genetics; Receptor Protein-Tyrosine Kinases - metabolism; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Signal Transduction; STAT5 Transcription Factor; Tandem Repeat Sequences - genetics; Thymidine - metabolism; Trans-Activators - metabolism; Tumor Cells, Cultured
• ISSN: 0887-6924; 1476-5381; 1476-5551
• DOI: 10.1038/sj.leu.2402740

Internal tandem duplications (ITD) and D835 point mutations of the receptor tyrosine kinase (RTK) FLT3 are found in a high proportion of cases with acute myeloid leukemia (AML). These genetic aberrations may lead to the constitutive activation of the receptor, thus providing the molecular basis for a persisting growth stimulus. We have screened 69 AML-derived cell lines for FLT3 mutations. Four of these cell lines showed ITD of the FLT3 gene, none carried a D835 point mutation. Two cell lines (MUTZ-11 and MV4-11) expressed exclusively the mutated allele, the other two cell lines (MOLM-13 and PL-21) displayed a mutated and the wild-type version of the gene. Although mutationally activated FLT3 is supposed to substitute for the stimulatory signal of a growth factor, one of these cell lines (MUTZ-11) was strictly cytokine-dependent. FLT3 transcripts were found in all four cell lines, but the constitutively phosphorylated receptor protein was clearly detectable only in cell line MV4-11, possibly explaining why MUTZ-11 cells were growth-factor dependent. Thus, not all FLT3 ITD-positive cells express high levels of the active receptor protein, a finding that might be of relevance for a possible future application of a kinase inhibitor as therapeutic agent. It had been described that STAT-5 phosphorylation was part of the FLT3 signalling chain and that STAT-5 molecules were constitutively phosphorylated in FLT3 ITD-positive cells. Although we observed the constitutive phosphorylation of STAT-5 molecules in FLT3-mutant cells, FLT3 ligand (FL) did not induce STAT-5 phosphorylation in FLT3 wild-type cells. These results suggest that the signalling mechanisms of the mutated FL receptor differ at least to some extent from those conferred by wild-type FLT3. In conclusion, (1) not all cells with FLT3 ITD express significant amounts of the mutated receptor protein; (2) signals downstream from wild-type and mutant FLT3 receptors are not 100% idential; and (3) MV4-11 represents a model cell line for FLT3 ITD signalling.