CBL mutation in chronic myelomonocytic leukemia secondary to familial platelet disorder with propensity to develop acute myeloid leukemia (FPD/AML)

Abstract

IntroductionFamilial platelet disorder with a propensity to develop acute myeloid leukemia (FPD/AML) is a rare autosomal dominant disease characterized by thrombocytopenia, abnormal platelet function, and a propensity to develop myelodysplastic syndrome (MDS) and AML. 1,2 Since Song et al reported haploinsufficiency of the RUNX1/CBFA2 gene, 3 more than 20 affected families have been reported. [4][5][6][7][8] Notably, various types of mono-allelic mutations of the RUNX1 gene have been found in patients with AML secondary to FPD. 3,7-9 RUNX1, which is a key regulator of definitive hematopoiesis and myeloid differentiation, is also commonly involved in sporadic cases of MDS and AML, by translocations in AML 10 and by point mutations in AML 11,12 and MDS. 13 Recently, a second RUNX1 alteration has been reported 8 ; however, no additional molecular abnormalities have been found so far.In this regard, recent reports of somatic mutations of the CBL proto-oncogene in myeloid neoplasms are intriguing because these CBL mutations have been shown to result in aberrant tyrosine kinase signaling, which would also lead to the activation of RAS signaling pathways. So far, we and others have reported that CBL mutations occurred in a variety of myeloid neoplasms, including de novo AML, 14,15 MDS,16,17 and myeloproliferative neoplasm, 16,17 especially in chronic myelomonocytic leukemia (CMML) 16,17 and juvenile myelomonocytic leukemia. 18 The importance of CBL mutations for leukemogenesis has substantially increased, which prompted us to search for possible CBL mutations in this pedigree.Here, we reported that CBL mutation developed at the time of diagnosis of CMML, but not during refractory cytopenia, in a Japanese patient with FPD/AML harboring a RUNX1 mutation. Methods RUNX1 mutation analysisDNA and RNA were extracted from peripheral blood (PB) of the proband, her sister, and their mother after obtaining informed consent. We performed mutation analysis of the RUNX1 gene by PCR followed by direct sequencing with the use of an ABI PRISM 310 Genetic Analyzer (Applied Biosystems). For further confirmation of deletion mutations, the PCR products were subcloned with the use of a TOPO TA Cloning Kit (Invitrogen) and then sequenced. Mutations were screened from exons 1-8 of the RUNX1 gene. CBL mutation analysisBecause CBL mutations thus far reported almost exclusively involved exons 8-9 that encode Linker/RING finger domains, we confined our mutation analysis to these exons, which were subjected to direct sequencing. Because the frequency of 11q-acquired uniparental disomy (11q-aUPD) was reported as ϳ 85%-90% in CBL mutations, we also analyzed the sample with Affymetrix GeneChip 250K NspI. [17][18][19] Genome-wide detection of copy number abnormalities or allelic imbalances was performed with CNAG/AsCNAR Version 3.0 software (http:// www.genome.umin.jp), which enabled sensitive detection of copy number neutral loss of heterozygosity (or aUPD). 19 In addition, we examined mutations of the following genes in the proband as previously rep...

Role of RUNX1 in hematological malignancies

“…151,152 In addition, FPD/AML patients may develop other types of leukemias, such as T-ALL, Hairy cell leukemia (HCL), and CMML. 151,[153][154][155] Interestingly, higher incidence of MDS and AML have been observed in families with certain types of mutations. 148,151 The exact mechanism of thrombocytopenia and leukemia in FPD/AML patients is not clear.…”

“…160 In addition, cooperating somatic mutations in more than 20 genes and copy number changes are observed in MDS and leukemic samples from FPD/AML patients. 154,155,162,164-169 ASXL1, CBL, CDC25C, FLT3, PHF6, SRSF2, and WT1 were identified as recurrently mutated genes. Additional studies using unbiased genomic approaches are required to identify recurrently mutated genes that cooperate with RUNX1.…”

Preleukemia: one name, many meanings

“…62 However, this mutation could not be detected by other investigators. 60, 63 This could represent ethnic differences. The number of mutations in the blast cells found at the time of AML varies between 8 and 18.…”

Myeloid neoplasms with germ line RUNX1 mutation

“…CBL mutations have also been identified in the patients with FPD/AML. Shiba et al reported that CBL mutation and 11q-acquired uniparental disomy (11q-aUPD) cooperate with RUNX1 mutation to develop CMML [36].…”