IDH1 and IDH2 mutations confer an adverse effect in patients with acute myeloid leukemia lacking the NPM1 mutation.

We examined the incidence and prognostic effect of IDH1 and IDH2 mutations in 233 Japanese adults with acute myeloid leukemia (AML). IDH1 R132 mutations were detected in 20 (8.6%) patients with AML. IDH2 mutations were found in 19 (8.2%, 17 R140 and two R172) patients. IDH1 and IDH2 mutations were mutually exclusive and were associated with normal karyotype AML, cytogenetic intermediate-risk group, and NPM1 mutations. Five-year overall survival (OS) rates were significantly lower (15.6%) in patients harboring the IDH mutations than in patients lacking the IDH mutation (32.0%) in the entire cohort of AML (P = 0.005). Among patients aged 59 yr or younger with IDH mutations, 5-yr OS in patients who underwent allogeneic stem cell transplantation (SCT) was significantly higher than that in those not receiving allogeneic SCT (50% vs. 10.6%, P = 0.020). Of 51 patients with NPM1 mutations, there was no significant difference in 5-yr OS rates between patients with and those without the IDH mutations. In contrast, among 175 patients lacking the NPM1 mutations, 5-yr OS rate in patients with IDH mutations was significantly lower than that in those without IDH mutations (0% vs. 34.7%, P = <0.001). These data suggest that IDH mutations have an unfavorable effect in AML, especially AML with the NPM1 wild type and younger AML patients with IDH mutations may benefit from allogeneic SCT.

High frequency of IKZF1 genetic alterations in adult patients with B-cell acute lymphoblastic leukemia.

Alterations in the IKZF1 gene are associated with poor prognosis in pediatric B-cell acute lymphoblastic leukemia (B-ALL). We examined the relationship between IKZF1 alterations and clinical findings in 78 adult patients with B-ALL. Aberrant isoforms of IKZF1 were detected using RT-PCR. The copy numbers of IKZF1 exons and fusion genes caused by exon deletions were determined using RQ-PCR and genomic PCR, respectively. We detected aberrant IKZF1 isoforms in 20 of the 78 patients (13 Ik6 and seven Ik10) and deletions of the entire or parts of the IKZF1 gene in 40 of 70 patients. No IKZF1 point mutations were detected by direct sequencing. Nineteen Ik6 and Ik10 isoforms had been generated through genomic exon deletions, but one through aberrant splicing. In total, 41 of the 78 (52.6%) patients harbored IKZF1 alterations, which were identified in 20 of 24 (83.3%) patients with Philadelphia chromosome (Ph)-positive B-ALL compared with 21 of 54 (38.9%) Ph-negative B-ALL (P = 0.0004). IKZF1 alterations are highly involved even in adults with B-ALL. To fully detect IKZF1 alterations, several methods with alternative approaches are required. To elucidate the clinical significance of IKZF1 alterations in adult B-ALL, our study warrants prospective clinical studies with a full analysis of IKZF1 alterations.

A family harboring a germ-line N-terminal C/EBPalpha mutation and development of acute myeloid leukemia with an additional somatic C-terminal C/EBPalpha mutation.

C/EBPalpha plays an essential role as a transcription factor in myeloid cell differentiation. Here, we describe a Japanese family in which two individuals with acute myeloid leukemia (AML) and one healthy individual had an identical 4-base pair insertion in the N-terminal region of CEBPA (350_351insCTAC), resulting in the termination at codon 107 (I68fsX107). The father and a son at diagnosis of AML had different in-frame insertion mutations in the C-terminal region of C/EBPalpha. These C-terminal mutations disappeared upon remission in both patients. Interestingly, the father showed different in-frame insertion mutations in the C-terminal CEBPA at the time of diagnosis and relapse. These data strongly suggest that the N-terminal C/EBPalpha mutation predisposes to the occurrence of a C-terminal C/EBPalpha mutation as a secondary genetic hit, causing AML.

p15 mRNA expression detected by real-time quantitative reverse transcriptase-polymerase chain reaction correlates with the methylation density of the gene in adult acute leukemia.

Cyclin-dependent kinase inhibitor p15 is frequently inactivated by either methylation or deletion in patients with acute leukemia. To examine pathologic and clinical significance of the p15 gene inactivation, we established a quantitative assay of p15 mRNA expression in the bone marrow cells by real-time quantitative reverse transcriptase-polymerase chain reaction. p15 mRNA expression in 14 patients with precursor B-cell acute lymphoblastic leukemia (PBC-ALL) well correlated with status of deletion and methylation in the p15 gene analyzed by Southern blotting. Furthermore, two patients with PBC-ALL and 11 acute myeloblastic leukemia (AML) were quantitatively examined for p15 gene methylation using bisulfite genomic sequencing. The data showed that p15 mRNA expression significantly correlated with the CpG island methylation density. Among 108 AML patients, p15 mRNA expression was significantly lower in the myeloid lineage (M1, M2, M3) than the monocytic lineage (M4, M5) (P = 0.0019). Above all, the majority of M3 patients showed low p15 expression compared with M1 and M2 patients (P = 0.029). These observations suggest that quantitative analysis of p15 mRNA will be useful to evaluate transcriptional repression of the p15 gene caused by various degrees of methylation.

Mutation in the RNA binding protein TIS11D/ZFP36L2 is associated with the pathogenesis of acute leukemia.

TIS11D is an AU-rich element binding protein that is involved in RNA metabolism and definitive hematopoiesis. Although disruption of genes related to hematopoiesis often leads to the development of leukemia and lymphoma, the involvement of TIS11D in hematological malignancies remains to be determined. In the present study, we identified a heterozygous frameshift mutation (I373fsX91) in the carboxy-terminus of the TIS11D gene in leukemic cells from a patient with acute myeloid leukemia. Moreover, biallelic inactivation of the TIS11D gene resulting from a hemizygous frameshift mutation (G107fsX80) was identified in the Burkitt's lymphoma cell line DG75. In HeLa cells, overexpression of wild-type TIS11D protein (TIS11D(WT)) induced growth inhibition and an S phase checkpoint response, while the mutant protein (TIS11D(I373fsX91)) showed a diminished effect. Interestingly, this response was accompanied by p21 downregulation, which is frequently seen in the cellular response to ultraviolet irradiation. These data suggest that the dysregulation of TIS11D function is associated with the pathogenesis of certain types of leukemia.

Micafungin-induced immune hemolysis attacks.

The echinocandins provide an attractive new option for prophylactic and empirical treatment of invasive fungal infections in patients with neutropenia after intensive cytotoxic chemotherapy or hematopoietic stem cell transplantation. We present two patients with hematological diseases who experienced massive intravascular hemolysis followed by renal failure after administration of micafungin. In indirect antiglobulin test, significant agglutination was observed when red blood cells were exposed to the mixture of micafungin and either of the patients' plasma samples, indicating that production of antibodies directed against both micafungin and red blood cell membrane induced hemolysis attack. Micafungin-mediated immune hemolysis represents an uncommon but life-threatening adverse reaction leading to renal failure.