Kerstin Willander

NOTCH1 mutations influence survival in chronic lymphocytic leukemia patients

BackgroundNOTCH1 PEST domain mutations in chronic lymphocytic leukemia have recently been shown to be of prognostic relevance. Both NOTCH1 and NOTCH2 are constitutively activated in B-cell CLL but not expressed in normal B cells and may be involved in survival and resistance to apoptosis in CLL. We screened for mutations in different parts of both NOTCH1 and NOTCH2 genes and related the changes to survival and other known risk factors.MethodsIn a cohort of 209 CLL patients, we used single strand conformation analysis to determine which of the samples carrying the NOTCH mutations and direct dideoxy sequencing was used to determine the exact nucleotide changes. Kaplan-Meier curves and log rank test were used to determine overall survival for NOTCH1 mutated cases and Cox regression analysis was used to calculate hazardous ratios.ResultsIn the present study, we found NOTCH1 PEST domain mutations in 6.7% of the cases. A shorter overall survival was found in patients with NOTCH1 mutations compared to wildtype (p = 0.049). Further, we also examined the extracellular and the heterodimerisation domains of the NOTCH1 gene and the PEST domain and heterodimerisation domain of the NOTCH2 gene, but no mutations were found in these regions. NOTCH1 mutations were most commonly observed in patients with unmutated IGHV gene (10/14), and associated with a more aggressive disease course. In addition, NOTCH1 mutations were almost mutually exclusive with TP53 mutations. In the combined group of NOTCH1 (6.7%) or TP53 (6.2%) mutations, a significant difference in overall survival compared to the wildtype NOTCH1 and TP53 was found (p = 0.002).ConclusionsBoth NOTCH1 and TP53 mutations seem to be independent predictive markers for worse outcome in CLL-patients and this study emphasizes the contention that NOTCH1 mutations is a novel risk marker.

MDM2 SNP309 promoter polymorphism, an independent prognostic factor in chronic lymphocytic leukemia

Background:  The single nucleotide polymorphism SNP309 with a change from T to G in the promoter region of the MDM2 gene is shown to increase the MDM2 protein levels and attenuate the p53 levels and associates with disease progression in several tumors.

Association between TERT promoter polymorphisms and acute myeloid leukemia risk and prognosis

Telomerase reverse transcriptase gene (TERT) promoter mutations are identified in many malignancies but not in hematological malignancies. Here we analyzed TERT and protection of telomeres 1 gene (POT1) mutations, and four different TERT SNVs in 226 acute myeloid leukemia (AML) patients and 806 healthy individuals in a case referent design, where also overall survival was assessed. A significant association for increased risk of AML was found for TERT SNVs, rs2853669 (OR = 2.45, p = 0.00015) and rs2736100 (OR = 1.5, p = 0.03). The overall survival for patients with CC genotype of rs2853669 was significantly shorter compared to those with TT or TC genotypes (p = 0.036 and 0.029 respectively). The influence of TERT rs2853669 CC on survival was confirmed in multivariable Cox regression analysis as an independent risk biomarker in addition to high risk group, higher age and treatment. No hot spot TERT promoter mutations at −228C > T or −250C > T or POT1 mutations could be identified in this AML cohort. We show that rs2853669 CC may be a risk factor for the development of AML that may also be used as a prognostic marker to identify high risk normal karyotype -AML (NK-AML) patients, for treatment guidance.

Mutations in the isocitrate dehydrogenase 2 gene and IDH1 SNP 105C > T have a prognostic value in acute myeloid leukemia

BackgroundThe isocitrate dehydrogenase (IDH1/IDH2) genes are metabolic enzymes, which are frequently mutated in acute myeloid leukemia (AML). The enzymes acquire neomorphic enzymatic activity when they mutated.MethodsWe have investigated the frequency and outcome of the acquired IDH1/IDH2 mutations and the IDH1 SNP 105C > T (rs11554137) in 189 unselected de novo AML patients by polymerase chain reaction amplification followed by direct sequencing. The survival are presented in Kaplan Meier curves with log rank test. Multivariable survival analysis was conducted using Cox regression method, taking age, risk group, treatment, IDH1/2 mutations and IDH1 SNP105 genotype into account.ResultsOverall, IDH1/2 mutations were found in 41/187 (21.7%) of the AML patients. IDH1 codon 132 mutations were present in 7.9%, whereas IDH2 mutations were more frequent and mutations were identified in codon 140 and 172 in a frequency of 11.1% and 2.6%, respectively. The SNP 105C > T was present in 10.5% of the patients, similar to the normal population. A significantly reduced overall survival (OS) for patients carrying IDH2 codon 140 mutation compared with patients carrying wild-type IDH2 gene (p < 0.001) was observed in the intermediate risk patient group. Neither in the entire patient group nor subdivided in different risk groups, IDH1 mutations had any significance on OS compared to the wild-type IDH1 patients. A significant difference in OS between the heterozygous SNP variant and the homozygous wild-type was observed in the intermediate risk FLT3 negative AML patients (p = 0.004).ConclusionsOur results indicate that AML-patients with IDH2 mutations or the IDH1 SNP 105C > T variant can represent a new subgroup for risk stratification and may indicate new treatment options.

Absence of hot spot mutations of the PIK3CA gene in acute myeloid leukaemia.

To the Editor: The most common genetic alteration in acute myeloid leukaemia (AML) is one or more internal tandem duplications in the juxtamembrane domain of the FMS-like tyrosine kinase 3 (FLT3/ITD), which results in constitutive activation of the kinase domain and downstream signalling events (1, 2). However, in the majority of patients, the genetic lesions are more undefined. Several studies have shown that FLT3 signalling activates both the RAS pathway and the phosphatidylinositol-3 kinase (PI3K) pathway (3,4). Downstream of PI3-kinase, Akt appears to be constitutively activated even in AML blasts without constitutive FLT3 signalling (5), suggesting that in AML patients lacking genetic alterations in the FLT3 receptor, downstream effector molecules such as PI3-kinase are involved and have tumourigenic effects. Somatic mutations in the PI3-kinase catalytic subunit p110a (PIK3CA) has been demonstrated within several human cancers, including breast, colon, brain and gastric cancer (6–9). The majority of all mutations were clustered at specific hot spots within the helical (exon 9) and kinase (exon 20) domains. In AML, less is known regarding the role of PI3-kinase, but constitutive activation of PI3-kinase/Akt pathway has been demonstrated (5). In addition, mutations in p110a could lead to an alternative way of survival of AML blasts. To evaluate the possible involvement of the PIK3CA gene in leukaemogenesis, we investigated the mutational frequency in exon 9 and 20 of PIK3CA in genomic DNA from bone marrow or peripheral blood samples from 68 AML patients [age (median, range) 65 yr, 19–80], using polymerase chain reaction (PCR)-based single-stranded conformation analysis (10). However, we did not find any mutations in either exon 9 or exon 20. To further confirm our results, we randomly sequenced some AML samples but were not able to demonstrate any mutations. In addition to our study, a recent report examining the frequency of PIK3CA mutations in solid tumours included different acute leukaemias in the analysis (8). Only one mutation (E545A) in exon 9 of a total of 88 samples of acute leukaemias was found and no mutations were identified in exon 20. Unfortunately, it was not specified whether the mutation was present in a patient with acute lymphoid leukemia (ALL) or AML, but nevertheless, the results together indicate the absence of PIK3CA mutations in AML. It is very unlikely that mutations occur in other exons of the PIK3CA gene. Nearly all mutations in the PIK3CA gene described cluster in exon 9 and exon 20 and more than 75% of the PIK3CA mutations are found in hot spots located in these two exons, where E542K, E545K and H1047R are the most frequent (6). Our finding highlights previous assumptions that the oncogenesis of leukaemia has different mechanisms than solid tumours. Although activating mutations in receptor tyrosine kinases (e.g. FLT3 and c-kit) and their downstream targets (e.g. Ras) are common in AML (11), it remains to elucidate which other genetic alterations besides these are responsible for the increased survival of AML blasts.

TP53 mutations and MDM2(SNP309) identify subgroups of AML patients with impaired outcome

TP53 is commonly mutated in several cancers and confers treatment resistance and poor prognosis. Altered expression of mouse double minute 2 (MDM2), a negative regulator of p53, may also attenuate normal p53 signaling, thereby enhancing tumor transformation and resistance to apoptosis. The single nucleotide polymorphism (SNP) 309 has been reported to increase MDM2 expression and impair normal p53 response.

MDM2 promotor polymorphism and disease characteristics in chronic lymphocytic leukemia: results of an individual patient data-based meta-analysis

A number of single nucleotide polymorphisms have been associated with disease predisposition in chronic lymphocytic leukemia. A single nucleotide polymorphism in the MDM2 promotor region, MDM2SNP309, was shown to soothe the p53 pathway. In the current study, we aimed to clarify the effect of the MDM2SNP309 on chronic lymphocytic leukemia characteristics and outcome. We performed a meta-analysis of data from 2598 individual patients from 10 different cohorts. Patients’ data and genetic analysis for MDM2SNP309 genotype, immunoglobulin heavy chain variable region mutation status and fluorescence in situ hybridization results were collected. There were no differences in overall survival based on the polymorphism (log rank test, stratified by study cohort; P=0.76; GG genotype: cohort-adjusted median overall survival of 151 months; TG: 153 months; TT: 149 months). In a multivariable Cox proportional hazards regression analysis, advanced age, male sex and unmutated immunoglobulin heavy chain variable region genes were associated with inferior survival, but not the MDM2 genotype. The MDM2SNP309 is unlikely to influence disease characteristics and prognosis in chronic lymphocytic leukemia. Studies investigating the impact of individual single nucleotide polymorphisms on prognosis are often controversial. This may be due to selection bias and small sample size. A meta-analysis based on individual patient data provides a reasonable strategy for prognostic factor analyses in the case of small individual studies. Individual patient data-based meta-analysis can, therefore, be a powerful tool to assess genetic risk factors in the absence of large studies.

TP53 mutations and MDM2 single nucleotide polymorphism 309T-G predicts outcome and treatment resistance in acute myeloid leukemia

TP53 mutations and MDM2 single nucleotide polymorphism 309T-G predicts outcome and treatment resistance in acute myeloid leukemia