The prognostic significance of bone marrow levels of neurofibromatosis-1 protein and ras oncogene mutations in patients with acute myeloid leukemia and myelodysplastic syndrome

BACKGROUND It has been reported that point mutations of the ras gene occur frequently in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). However, the prognostic significance of ras gene mutations in patients with these disorders has been a controversial issue. Although abnormalities in the neurofibromatosis 1 (NF1) gene, which is a gene involved in the ras pathway, have been observed frequently in patients with juvenile chronic myelogenous leukemia, the role of these abnormalities in adult patients with AML or MDS is not clear. METHODS In this study, bone marrow specimens that were obtained from previously untreated patients with AML and MDS were examined for ras mutations, and the levels of NF1 protein expression were measured. RESULTS Ras point mutations were detected in 16 of 83 patients with AML (19%) and in 21 of 90 patients with MDS (23%). Fourteen of 28 patients with chronic myelomonocytic leukemia (50%) had ras gene mutations. Decreased bone marrow levels of NF1 protein (< 70% of the median level detected in control bone marrow specimens) were observed in 20 of 66 patients with AML (30.3%) and in 8 of 29 patients with MDS (27.6%); none of the patients with ras gene mutations had decreased bone marrow levels of NF1 protein. The presence of a mutant ras gene was associated with a shorter complete remission duration (CRD) in patients with MDS (P = 0.05) but had no effect on survival in patients with AML or MDS. Patients with AML who had decreased NF1 protein levels had a slightly longer CRD compared with patients who had normal NF1 levels (P = 0.07). However, the NF1 level had no significant impact on survival among patients with AML or MDS. When patients with low NF1 levels were grouped with patients who had ras mutations, the patients who had AML had a significantly longer CRD compared with the patients who had MDS (P = 0.02). CONCLUSIONS The current results suggest that a reduction in NF1 protein expression and the presence of ras point mutations may complement each other and that they both play a complex role in the biology of AML and MDS. Cancer 2003;97:441–9. © 2003 American Cancer Society. DOI 10.1002/cncr.11036