Rare point mutation at codon 301 and 969 of FMS/M-CSF receptor in acute myelomonocytic and monocytic leukemia

Cooperating mutations of receptor tyrosine kinases and Ras genes in childhood core-binding factor acute myeloid leukemia and a comparative analysis on paired diagnosis and relapse samples

c-KIT mutations have been described in core-binding factor (CBF) acute myeloid leukemia (AML) at diagnosis. The role of c-KIT mutations in the relapse of CBF-AML is not clear. The role of CSF1R mutation in the pathogenesis of AML remains to be determined. We analyzed receptor tyrosine kinases (RTKs) and Ras mutations on 154 children with AML. Also, we examined the paired diagnosis and relapse samples in CBF-AML. CBF-AML accounted for 27% (41/154). c-KIT mutations were detected in 41.5% of CBF-AML at diagnosis (6 in exon 8, 10 in exon 17 and 1 in both exons 8 and 17) , FLT3-TKD 2.7%, N-Ras mutations 7.3% and K-Ras mutations 4.9%. FLT3-LM and CSF1R mutations were not found in CBF-AML. The mutations of RTKs and Ras were mutually exclusive except for one patient who had both c-KIT and N-Ras mutations. Eight of the 41 CBF-AML patients relapsed; four patients retained the identical c-KIT mutation patterns as those at diagnosis, the remaining four without c-KIT mutations at diagnosis did not acquire c-KIT mutations at relapse. Our study showed that 54% of childhood CBF-AML had RTKs and/or Ras mutations; c-KIT but not CSF1R mutations play a role in the leukemogenesis of childhood CBF-AML.

Regulatory roles of the ligand for Flk2/Flt3 tyrosine kinase receptor on human hematopoiesis

The biological activities of the ligand for the Flk2/Flt3 receptor tyrosine kinase (FL) on human hematopoietic cells are reviewed. In in vitro studies, FL shows relatively few effects by itself on the proliferation and differentiation of hematopoietic cells, but exhibits a potent costimulatory activity in enhancing the proliferation of progenitor cells of multiple lineages. FL promotes the growth of clonogenic myeloid progenitor cells in the presence of other cytokines known to be active on myeloid progenitors, including GM-CSF, interleukin 3 (IL-3), kit ligand (KL), M-CSF and G-CSF. In addition, FL synergizes with IL-7 in inducing the proliferation of pro-B cells, whereas FL has little effect on the growth of clonogenic erythroid progenitors. Furthermore, FL induces the in vitro expansion of the high proliferative potential colony-forming cells (HPP-CFC) and stimulates the proliferation of long-term culture-initiating cells (LTC-IC), suggesting an activity on the proliferation of putative stem cells. Thus, FL plays important roles in regulating the proliferation of hematopoietic progenitor cells and, therefore, may have therapeutic applications.

FMS mutations in patients following cytotoxic therapy for lymphoma

Point mutations at codons 301 and 969 of the FMS proto-oncogene have been reported in both myelodysplasia (MDS) and acute myeloid leukaemia (AML). We report here the incidence of such mutations in patients at risk of developing secondary MDS and AML. Peripheral blood DNA from 70 patients in remission from lymphoma was screened for mutations by oligonucleotide (ONH) using mutant specific probes. Codon 969 mutations were detected in 11 of the 70 (15.7%) cases. No codon 301 mutations were detected. Five of these mutations were confirmed using an independent technique (single nucleotide primer extension analysis, SNPE) and a further mutation was detected in a single patient using single-stranded conformational polymorphism analysis (SSCP). No codon 969 mutations were detected in 62 lymphoma biopsy specimens from these patients or from three patients with detectable FMS mutations where pre-therapy marrow was investigated by ONH. No mutations at either codons 301 or 969 were detected by ONH in 61 normal controls. Somatic mutations at codon 969 of the FMS gene occur commonly following cytotoxic therapy for lymphoma and their detection indicates the presence of a clonally expanded population of abnormal cells.