Risk Factors For Acute Myeloid Leukemia Research Articles

Constitutional Loss-of-Function Mutations in Telomerase Are Genetic Risk Factors for Acute Myeloid Leukemia.

Telomeres protect chromosome ends from end-to-end fusion and recombination but are gradually eroded with proliferation. Critically short telomeres are repaired by the telomerase complex and mutations in telomerase complex genes (TERT and TERC) are associated with dyskeratosis congenita and acquired aplastic anemia. Telomere shortening eventually results in cell proliferation arrest, apoptosis, or genomic instability, and patients with dyskeratosis congenita and acquired aplastic anemia are at risk for developing leukemia and other malignancies. We therefore investigated whether TERT and TERC gene mutations were associated with acute myeloid leukemia (AML) by screening 100 consecutive Brazilian patients diagnosed with AML (excluding acute promyelocytic leukemia) at the same institution and 198 ethnic-, age-, and sex-matched healthy volunteers. Eight patients carried a non-synonymous TERT gene variant; one was homozygous and five heterozygous for A1062T, one was heterozygous for H412Y, and another was heterozygous for a novel R522K TERT mutation. None of these gene variants was present in matched controls (Fisher's exact test, P=0.0001). We validated our results by screening an additional 89 AML patients from the MD Anderson Cancer Center, selected based on cytogenetic status and 528 healthy controls. Four of these 89 patients had a non-synonymous TERT gene variant (one homozygous, three heterozygous), an incidence higher than in controls (P=0.028). To further address the higher prevalence of the A1062T gene variant in AML, we screened a total of 1,111 controls, and found a 3.8 times higher A1062T allele frequency in AML than in controls (P=0.002). The germ-line origin of mutations was established by mutation detection in non-hematopoietic tissues and in relatives. Cytogenetics were available for four TERT-mutant patients in the Brazilian cohort: two had inv(16), one had t(5;11)(q35;q13) and del(10)(p15), and another had complex karyotype (including trisomy 8). In the MD Anderson cohort, 2 patients had inv(16) and two had trisomy 8. The incidence of TERT mutations was higher in patients with trisomy 8 (2/10) or inv (16) (2/22) than in other patients (0/57; P =0.02 for trisomy 8 and 0.08 for inv(16) vs. other). Telomere lengths of blast cells were extremely short (median length, 3.1 kb; range, 2.4-5.9 kb). Vectors containing TERT mutants were transfected into VA13 cells and telomerase activity of transfected cell lysates, measured by the fluorescent telomere repeat amplification protocol (TRAP) assay, demonstrated that AML-associated TERT gene variants resulted in significantly reduced telomerase function in comparison to wild-type TERT by haploinsufficiency. Our results indicate that constitutional TERT gene mutations are risk factors for AML. Abnormal telomerase function of hematopoietic stem cells may result in short and dysfunctional telomeres, facilitating genomic instability, aneuploidy, and probably contributing to an early stage of leukemogenesis.

MN1 Expression Predicts Prognosis of Acute Myeloid Leukemia with Normal Cytogenetics.

Cytogenetic aberrations are important prognostic factors in acute myeloid leukemia (AML). However, approximately half of adult AML patients lack cytogenetic abnormalities and identification of predictive molecular markers might improve therapy. Fusion of meningioma-1 (MN1) to TEL (ETV6) has been found in AML and MDS with t(12;22)(p13;q11). However, expression levels of MN1 have not been reported previously in AML. We evaluated MN1 expression as a prognostic marker in 142 AML patients aged 18–60 years with normal cytogenetics, who were uniformely treated according to the AML-SHG 1/99 trial. Patients received intensive, cytarabine-based induction and consolidation treatment including allogeneic progenitor cell transplantation if an HLA-compatible sibling was available, or in case of relapse. Specimens were obtained at diagnosis, and routine cytogenetic, FLT3-mutation, and MLL-PTD analyses were performed. MN1 expression was quantified by real-time RT-PCR on a LightCycler using QuantiTect SYBR Green. AML samples were dichotomized at the median value resulting in two groups: a low MN1 group and a high MN1 group. Baseline characteristics and outcome parameters were compared between these two groups. In addition, CD34+ cells were immunomagnetically enriched from mobilized blood of a healthy donor using MACS CD34 isolation kit. Cells were cultured in IMDM medium with various cytokines including either G-CSF, M-CSF or EPO. At various time points, cells were harvested and analyzed for MN1 expression. There were no significant differences between low MN1 and high MN1 expressing patients with respect to age, gender, ECOG performance status, diagnosis of de novo or secondary AML, FAB morphology, white blood cell count, percentage of blasts in blood or bone marrow, FLT3 mutations, or MLL-PTD. Low MN1 expressing patients significantly more often achieved a good response to the first course of induction treatment defined as blasts in bone marrow below 5%, no blasts in peripheral blood, and no extramedullary manifestation at day 15 compared to high MN1 expressing patients (87.3% vs. 71.8%, p=.02). There was no significant difference for remission status between the two groups. High MN1 expression predicted significantly shorter event-free survival (19% vs. 45.8% at 3 years, log-rank p=.0009), shorter relapse-free survival (23% vs. 52.8% at 3 years, log-rank p=.001), and shorter overall survival (38.2% vs. 58.8% at 3-years, log-rank p=.03). The high MN1 group relapsed significantly more often compared to the low MN1 group (56.7% vs. 35%, p=.02), and thus received an allogeneic transplant significantly more often (50.7% vs. 33.8%, p=.04). In multivariate analysis including known risk factors only MN1 expression, age (above the median compared to below the median age), and ECOG performance status (0 or 1 compared to 2) remained significant (hazard ratio: 2 (p=.01), 2.1 (p=.005) and 2.8 (p=.005), respectively). MN1 expression in CD34+ cells was 37-fold higher compared to the CD34− cell fraction. However, by in vitro differentiation of CD34+ cells using various cytokines including either G-CSF, M-CSF or EPO, MN1 expression dropped to levels found in the CD34− fraction within 7 days of culture. In conclusion, high MN1 expression predicts adverse prognosis and may define an important risk factor in AML with normal cytogenetics. Its upregulation in hematopoietic progenitor cells hints at a functional role of MN1 in blocking differentiation.

BAALC expression predicts clinical outcome of de novo acute myeloid leukemia patients with normal cytogenetics: a Cancer and Leukemia Group B Study

AbstractCytogenetic aberrations are important prognostic factors in acute myeloid leukemia (AML). Of adults with de novo AML, 45% lack cytogenetic abnormalities, and identification of predictive molecular markers might improve therapy. We studied the prognostic impact of BAALC (Brain And Acute Leukemia, Cytoplasmic), a novel gene involved in leukemia, in 86 de novo AML patients with normal cytogenetics who were uniformly treated on Cancer and Leukemia Group B 9621. BAALC expression was determined by comparative real-time reverse transcriptase–polymerase chain reaction in pretreatment blood samples, and patients were dichotomized at BAALC's median expression into low and high expressers. Low expressers had higher white counts (P = .03) and more frequent French-American-British M5 morphology (P = .007). Compared to low expressers, high BAALC expressers showed significantly inferior overall survival (OS; median, 1.7 vs 5.8 years, P = .02), event-free survival (EFS; median, 0.8 vs 4.9 years, P = .03), and disease-free survival (DFS; median, 1.4 vs 7.3 years, P = .03). Multivariable analysis confirmed high BAALC expression as an independent risk factor. For high BAALC expressers the hazard ratio of an event for OS, EFS, and DFS was respectively 2.7, 2.6, and 2.2. We conclude that high BAALC expression predicts an adverse prognosis and may define an important risk factor in AML with normal cytogenetics.