MUTATIONS IN THE GENE FOR THE GRANULOCYTE COLONY-STIMULATING – FACTOR RECEPTOR IN PATIENTS WITH ACUTE MYELOID LEUKEMIA PRECEDED BY SEVERE CONGENITAL NEUTROPENIA

Background. In severe congenital neutropenia the maturation of myeloid progenitor cells is arrested. The myelodysplastic syndrome and acute myeloid leukemia develop in some patients with severe congenital neutropenia. Abnormalities in the signal-transduction pathways for granulocyte colony-stimulating factor (G-CSF) may play a part in the progression to acute myeloid leukemia. Methods. We isolated genomic DNA and RNA from hematopoietic cells obtained from two patients with acute myeloid leukemia and histories of severe congenital neutropenia. The nucleotide sequences encoding the cytoplasmic domain of the G-CSF receptor were amplified by means of the polymerase chain reaction and sequenced. Murine myeloid 32D.C10 cells were transfected with complementary DNA encoding the wild-type or mutant G-CSF receptors and tested for their responses to G-CSF. Results. Point mutations in the gene for the G-CSF receptor were identified in both patients. The mutations, a substitution of thymine for cytosine at the codon for glutamine at position 718 (Gln718) in one patient and at the codon for glutamine at position 731 (Gln731) in the other, caused a truncation of the C-terminal cytoplasmic region of the receptor. Both mutant and wild-type genes for the G-CSF receptor were present in leukemic cells from the two patients. In one patient, the mutation was also found in the neutropenic stage, before the progression to acute myeloid leukemia. The 32D.C10 cells expressing mutant receptors had abnormally high proliferative responses but failed to mature when cultured in G-CSF. The mutant G-CSF receptors also interfered with terminal maturation mediated by the wild-type G-CSF receptor in the 32D.C10 cells that coexpressed the wildtype and mutant receptors. Conclusions. Mutations in the gene for the G-CSF receptor that interrupt signals required for the maturation of myeloid cells are involved in the pathogenesis of severe congenital neutropenia and associated with the progression to acute myeloid leukemia. (N Engl J Med 1995;333: 487-93.) From the Department of Hematology, Dr. Daniel den Hoed Cancer Center and Institute of Hematology, Erasmus University, Rotterdam, the Netherlands (F.D., B.L., I.P.T.); the Department of Clinical Pathology, City of Hope National Medical Center, Duarte, Calif. (R.K.B.); and the Department of Pediatric Hematology and Oncology, Hannover Medical School, Hannover, Germany (N.T., K.W.). Address reprint requests to Dr. Touw at the Dr. Daniel den Hoed Cancer Center, P.O. Box 5201, 3008 AE Rotterdam, the Netherlands. Supported by the Dutch Cancer Society. S EVERE congenital neutropenia (Kostmann’s syndrome) comprises a heterogeneous group of disorders with variable inheritance whose main features are recurrent bacterial infections and severe neutropenia (fewer than 200 neutrophils per cubic millimeter). The bone marrow almost invariably shows an arrest of granulocytic maturation at the promyelocytic or myelocytic stage. 1-6 Patients with severe congenital neutropenia have an increased susceptibility to acute myeloid leukemia. 7-10 An abnormal response of granulocytic progenitor cells to granulocyte colony-stimulating factor (G-CSF) may play a part in the pathogenesis of severe congenital neutropenia. The in vitro response to G-CSF of myeloid progenitor cells from patients with this disorder is often reduced. 11,12 Pharmacologic doses of G-CSF increase the neutrophil count in the majority of patients with severe congenital neutropenia. 12-14 The G-CSF receptor, a single polypeptide containing 813 amino acids, 15,16 transduces signals that regulate the proliferation, maturation, and survival of myeloid progenitor cells. 17 The cytoplasmic region proximal to the membrane of the receptor transduces proliferative and survival signals, whereas the distal C-terminal region transduces maturation signals and suppresses the receptor’s proliferative signals. 18-20 A truncated G-CSF receptor, lacking the C-terminal maturation domain as a consequence of a point mutation, has recently been reported in a patient with severe congenital neutropenia. 21 We report here on point mutations in the gene for the G-CSF receptor in two patients with acute myeloid leukemia and histories of severe congenital neutropenia. These mutations also truncate the C-terminal cytoplasmic region of the G-CSF receptor. The mutation in one of the patients was already present in the neutropenic phase that preceded the development of acute myeloid leukemia. Our results suggest that the development of acute myeloid leukemia in patients with severe congenital neutropenia may involve a disruption of the maturation-signaling function of the G-CSF receptor.