ATM mutations are rare in familial chronic lymphocytic leukemia

Familial chronic lymphocytic leukemia in Israel: A disproportionate distribution among Ashkenazi Jews

BACKGROUND

Relatives of patients with chronic lymphocytic leukemia (CLL) are at increased risk of developing CLL. Familial CLL is defined as more than one case of CLL among blood relatives, a phenomenon reported in approximately 5%-10% of all CLL patients.

OBJECTIVE

Given the known predisposition of CLL among Ashkenazi Jews, we studied the features of familial CLL in an Israeli population.

METHODS

This is a retrospective study, in which we reviewed the demographics, clinical characteristics, and outcomes of a total of 332 patients with CLL/small lymphocytic lymphoma.

RESULTS

Familial CLL was recorded in 41 cases (12.3%) of the patients. The age at diagnosis was younger in patients with familial CLL (by almost 3.5 years). Familial CLL was strongly associated with Ashkenazi Jewish origin. Patients with familial CLL more commonly presented with higher hemoglobin and lower serum β-2-microglobulin levels. No significant differences were detected between sporadic and familial CLL in disease stage, time to treatment, second cancers, or overall survival.

CONCLUSION

Familial cases of CLL in an Israeli population show a disproportionate ethnic distribution toward Jews of Ashkenazi origin. The clinical characteristics and the overall outcome are not substantially different from sporadic cases.

The role of ATM mutations and 11q deletions in disease progression in chronic lymphocytic leukemia

Abstract ATM gene alteration is a frequent event in pathogenesis of chronic lymphocytic leukemia (CLL) and occurs as monoallelic loss in the form of 11q23 deletion, with and without mutation in the remaining ATM allele. ATM is a principal DNA damage response gene and biallelic ATM alterations lead to ATM functional loss and chemoresistance. The introduction of new therapies, such as intensive chemoimmunotherapy and inhibition of B-cell receptor (BCR) signaling, has changed clinical responses for the majority of CLL tumors including those with 11q deletion, but it remains to be determined whether these strategies can prevent clonal evolution of tumors with biallelic ATM alterations. In this review we discuss ATM function and the consequences of its loss during CLL pathogenesis, differences in clinical behavior of tumors with monoallelic and biallelic ATM alterations, and we outline possible approaches for targeting the ATM null CLL phenotype.

Incidence and clinical implications of ATM aberrations in chronic lymphocytic leukemia

A subset of chronic lymphocytic leukemia (CLL) carries mutations in ataxia telangiectasia mutated (ATM). Such ATM mutations may be particularly relevant in the setting of del11q, which invariably results in the deletion of one ATM allele. To improve our understanding of the frequency and type of ATM mutations that exist in CLL, we resequenced all ATM coding exons in 24 CLL with del11q using direct sequencing. We detected two missense mutations, resulting in an ATM mutation frequency of 8%; nonsense and frameshift mutations were not identified. Given the low ATM mutation frequency detected in this cohort, we proceeded with measurements of nonmutational ATM aberrations in CLL through analysis of the activation state of ATM in response to external irradiation. The phosphorylation state of ATM at Ser-1981 was measured using quantitative immunoblotting in purified CLL cells isolated from 251 CLL patients; data were normalized to simultaneous measurements of total ATM protein and actin. Resulting p-ATM/ATM and p-ATM/actin ratios were subsequently analyzed for prognostic significance inclusive and exclusive of TP53 exons 2-10 mutations. From these analyses, conducted in a large prospectively enrolled CLL patient cohort, neither the p-ATM/ATM nor the p-ATM/actin ratios were found to be prognostic for short survival. These data in aggregate demonstrate a low frequency of ATM aberrations in an unselected CLL cohort and do not support a major prognostic role for ATM aberrations in CLL, thus motivating renewed research efforts aimed at understanding the pathobiology of 11q deletions in CLL. © 2012 Wiley Periodicals, Inc.

Variations of the ataxia telangiectasia mutated gene in patients with chronic lymphocytic leukemia lack substantial impact on progression-free survival and overall survival: a Cancer and Leukemia Group B study

The impact of mutation of the ATM (ataxia telangiectasia mutated) gene in chronic lymphocytic leukemia (CLL) treatment outcome has not been examined. We studied ATM mutations in 73 patients treated with fludarabine and rituximab. ATM gene mutation analysis was performed using temperature gradient capillary electrophoresis. The impact of detected variants on overall survival (OS) and progression-free survival (PFS) was tested with proportional hazards models. None of the 73 patients demonstrated truncating ATM mutations; 17 (23%, 95% confidence interval 14-35%) had non-silent variants (ATM-NSVs), including 13 known ATM polymorphisms and four missense variants. ATM-NSVs were not significantly associated with any baseline characteristics including immunoglobulin heavy chain variable gene (IGVH) status. In multivariable models, no significant differences in complete response (p =0.70), PFS (p =0.59) or OS (p =0.13) were observed. Our data indicate that truncating ATM mutations are rare in patients with CLL. Furthermore, in this dataset, these non-silent variants had limited impact on PFS and OS.

ATM germline heterozygosity does not play a role in chronic lymphocytic leukemia initiation but influences rapid disease progression through loss of the remaining ATM allele

Ataxia telangiectasia patients, with constitutional bi-allelic ATM mutations, have a marked risk of lymphoid tumors and ATM mutation carriers have a smaller risk of cancer. Sporadic ATM mutations occur in 10-20% of chronic lymphocytic leukemia and are often associated with chromosome 11q deletions which cause loss of an ATM allele. The role of constitutional ATM mutations in the pathogenesis of chronic lymphocytic leukemia is unknown. Here we investigated the frequency of constitutional ATM mutations in either of two chronic lymphocytic leukemia cohorts, those with and without a chromosome 11q deletion. We found that in comparison to controls, constitutional pathogenic ATM mutations were increased in patients with chromosome 11q deletions (6 of 140 vs. 0 of 281, P = 0.001) but not in those without 11q deletions (2 of 178 vs. 0 of 281, P = 0.15). These results suggest that ATM germline heterozygosity does not play a role in chronic lymphocytic leukemia initiation but rather influences rapid disease progression through ATM loss.

Inherited predisposition to chronic lymphocytic leukemia

Inherited susceptibility to chronic lymphocytic leukemia (CLL) has been recognized for decades. Approximately 10% of individuals with CLL report a family history of CLL or a related lymphoproliferative disorder, and genetic predisposition is the best understood risk factor for CLL. Studies of familial CLL have suggested that the disease features are largely similar to sporadic CLL, although recent data suggest that familial CLL may more commonly show somatic hypermutation of the immunoglobulin heavy-chain variable region, suggesting a more indolent disease course. Monoclonal B-cell lymphocytosis (MBL) has been identified recently as a likely precursor to CLL; it is found in the general population with increasing age and enriched in unaffected relatives of individuals with familial CLL. Studies of MBL as well as mouse models of CLL may lead to better understanding of early CLL pathogenesis that is relevant to familial predisposition. To date, the identification of genes that predispose to familial CLL has been slow, primarily due to the relatively few families available for study, the small size of those families and disease causation most likely by multiple genes that each confer smaller risks. In the coming years, the application of systematic genomics approaches to familial CLL should, hopefully, lead to the identification of novel loci involved in the disease.

Genetic alteration associated with chronic lymphocytic leukemia

The genetics of B-cell chronic lymphocytic leukemia (B-CLL) differ considerably from most other forms of hematologic malignancy which are usually characterized by chromosome translocations. B-CLL typically contains chromosomal deletions and chromosomes 13q14 and 11q22-->q23 are the most common. These two regions appear to share a common ancestral origin (Auer et al., 2007b). Overall, chromosomal abnormalities can be found in the majority of patients with B-CLL when using sensitive techniques (Dohneret al., 2000) and possibly reflects an underlying predisposition, with a small but significant number of familial cases. Although single and consistent abnormalities are most common, multiple rearrangements can occur, often with disease progression (Feganetal., 1995; Dohner et al., 2000). Regions of recurrent deletion suggest the presence of tumor suppressor genes if following Knudson's theoretical 2-hit model. However, despite extensive sequencing analysis over the last decade and lack of pathogenic mutations identified, there has been a move away from this suggested hypothesis and alternative mechanisms of gene inactivation involving epigenetic silencing or haploinsufficiency may be considered as more likely in this disease. This review focuses on the common genetic abnormalities in B-CLL and relates them to some of the more recent hypotheses on inactivation of genes within these regions of deletion.

Familiäre Leukämien

Im Gefolge einer Vielzahl von genetisch bedingten Erkrankungen, wie den DNA-Reparatur-Defizienz-Syndromen, Tumordispositions-, Immundefizienz-, Cancer-Family- und Bone-Marrow-Failure-Syndromen sowie bei einigen angeborenen Chromosomenanomalien werden oft Leukämien und andere hämatologische Neoplasien beobachtet. In letzter Zeit konnten darüber hinaus in Familien mit erhöhter Leukämieinzidenz konstitutionelle Mutationen spezifischer Gene identifiziert werden, die auch bei sporadischen Leukämien in Form von somatischen Mutationen involviert sind. Neben diesen Mutationen mit hoher Penetranz scheinen Genveränderungen mit niedriger Penetranz oder auch Polymorphismen von Genen, die bei der Zellproliferation, der DNA-Reparatur, der Apoptose, der Detoxifizierung u. a. m. eine Rolle spielen, die Disposition zur Leukämieentwicklung bzw. den Krankheitsverlauf zu beeinflussen. Diese neuen Erkenntnisse über konstitutionelle, zu Leukämien disponierende genetische Veränderungen könnten die Kluft zwischen angeborenen und erworbenen genetischen Erkrankungen allmählich überbrücken.

The spectrum of ATM missense variants and their contribution to contralateral breast cancer

Heterozygous carriers of ATM mutations are at increased risk of breast cancer. In this case-control study, we evaluated the significance of germline ATM missense variants to the risk of contralateral breast cancer (CBC). We have determined the spectrum and frequency of ATM missense variants in 443 breast cancer patients diagnosed before age 50, including 247 patients who subsequently developed CBC. Twenty-one per cent of the women with unilateral breast cancer and 17% of the women with CBC had at least one ATM germline missense variant, indicating no significant difference in variant frequency between these two groups. We have found that carriers of an ATM missense mutation, who were treated with radiotherapy for the first breast tumour, developed their second tumour on average in a 92-month interval compared to a 136-month mean interval for those CBC patients who neither received RT nor carried a germline variant, (p = 0.029). Our results indicate that the presence of ATM variants does not have a major impact on the overall risk of CBC. However, the combination of RT and (certain) ATM missense variants seems to accelerate tumour development.

ATM alterations in childhood non-Hodgkin lymphoma

ATM gene alterations and impaired ATM protein expression have been described in various adult lymphoproliferative malignancies, suggesting that ATM contributes to lymphomagenesis. The present study investigated the prevalence of ATM gene and ATM protein expression alterations in sporadic childhood non-Hodgkin lymphoma (NHL). Twenty-seven cases of NHL were screened for ATM mutations by denaturing high-performance liquid chromatography (DHPLC). Direct and indirect criteria, including in silico tools, were used to classify the gene alterations. The methylation status of the ATM promoter CpG island was determined in 25 samples; ATM protein expression was assessed by Western blot in 9 lymphomas. ATM alterations were detected in 12 NHLs (44%). Ten different heterozygous base substitutions were identified in 10 NHLs (37%). Five samples (19%) were found to harbor a gene alteration considered to be a mutation or a rare variant potentially pathogenic. In one case, an ATM mutation was found in the germline. Four NHLs (44%) showed reduced or absent ATM protein expression. Except for one sample, no definite genetic or epigenetic alteration was identified to account for impaired ATM protein expression. These observations document a high prevalence of ATM gene and protein expression alterations, suggesting that ATM is involved in childhood NHL.

Clinical and laboratory parameters that define clinically relevant B-CLL subgroups

B cell-type chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease. This is reflected by the very wide-ranging clinical courses that B-CLL patients experience and by the marked variation in laboratory findings between patients. In this chapter, we will review the various clinical and laboratory parameters that divide B-CLL patients into "subgroups," and correlate the parameters that define them. When feasible, we will also link clinical features to the cellular and genetic characteristics recently defined for these leukemic cells. The discussion is limited to parameters that define phenotypes or subgroups that may relate to disease activity and clinical outcome.

A high-density SNP genomewide linkage scan for chronic lymphocytic leukemia-susceptibility loci

Chronic lymphocytic leukemia (CLL) and other B-cell lymphoproliferative disorders (LPDs) show clear evidence of familial aggregation, but the inherited basis is largely unknown. To identify a susceptibility gene for CLL, we conducted a genomewide linkage analysis of 115 pedigrees, using a high-density single-nucleotide polymorphism (SNP) array containing 11,560 markers. Multipoint linkage analyses were undertaken using both nonparametric (model-free) and parametric (model-based) methods. Our results confirm that the presence of high linkage disequilibrium (LD) between SNP markers can lead to inflated nonparametric linkage (NPL) and LOD scores. After the removal of high-LD SNPs, we obtained a maximum NPL of 3.14 (P=.0008) on chromosome 11p11. The same genomic position also yielded the highest multipoint heterogeneity LOD (HLOD) score under both dominant (HLOD 1.95) and recessive (HLOD 2.78) models. In addition, four other chromosomal positions (5q22-23, 6p22, 10q25, and 14q32) displayed HLOD scores >1.15 (which corresponds to a nominal P value <.01). None of the regions coincided with areas of common chromosomal abnormalities frequently observed for CLL. These findings strengthen the argument for an inherited predisposition to CLL and related B-cell LPDs.

CLL family ‘Pedigree 14’ revisited: 1947–2004

The notion that inherited predisposition contributes to the development of haematological malignancies is generally thought of as being a relatively new idea. However, Videbaek made a clear enunciation of such a hypothesis in 1947, from a study of tumour incidence in relatives of patients with different leukaemias. To gain further insight into inherited susceptibility to chronic lymphocytic leukaemia (CLL), we followed up the descendants of Videbaek's 'Pedigree 14' series of families. Using the Danish medical and pedigree databases, complete tracing of 222 descendants of the original 57 family members was achieved. To date, 10 family members have been diagnosed with CLL, one with T-cell lymphoma and 17 with nonhaematological cancers, including five with breast cancer. The detailed follow up of this family provides further support for inherited predisposition to CLL and illustrates the value of follow-up studies of previously published family material for genetic analyses.

Perspectives on familial chronic lymphocytic leukemia: genes and the environment

Chronic lymphocytic leukemia (CLL) comprises a substantial proportion of leukemias in adults in the western hemisphere. Male gender, increasing age, ethnicity (high in Caucasians, lowest in Asians), and family history are risk factors. Although no specific extrinsic etiologic factors have been established, farming and pesticide exposure are associated with increased risk. Migration studies confirm that ethnic groups retain the risk associated with their origin rather than their new location, favoring a role for heredity. Kindreds with multiple cases of CLL have been well described in the literature and studies in large populations confirm that lymphoproliferative malignancies and especially CLL occur together at a rate that cannot be attributed to chance. Since environmental factors cannot readily explain the familial aggregations, a hereditary factor that affects susceptibility to CLL is likely. The identification of clones that are immunophenotypically identical to CLL in healthy individuals from CLL kindreds (14% to 18%) as well as in the general population (3.5% in age bracket >65 years) suggests a possible precursor condition, but longitudinal studies will be necessary to establish significance in the general population. Family (linkage) and population (candidate gene) studies to date have been too small to identify the specific genes that account for increased susceptibility; larger studies including planned consortia to identify additional high-risk kindreds for genetic studies, as well as the application of advanced technologies such as genomics, cytogenetic, expression, and proteomics, are widely expected to advance understanding over the next few years.

Overlapping deletion regions at 11q23 in myelodysplastic syndrome and chronic lymphocytic leukemia, characterized by a novel BAC probe set

Translocations or deletions involving the 11q23 region have been observed in acute lymphoblastic leukemia (ALL), acute myelocytic leukemia (AML), myelodysplastic syndrome (MDS), and chronic lymphocytic leukemia (CLL). BAC probes encompassing the D11S29 and D11S924 markers and flanking the MLL gene were used in dual color fluorescence in situ hybridization. Fifteen patients with hematologic malignancies and cytogenetic abnormalities of 11q23 were analyzed. The BAC and MLL probes demonstrated split signals in five of 7 ALL or AML cases with translocations of 11q23. Of the remaining 2 cases, one had normal signals for both probe sets and the other had a submicroscopic deletion of the MLL 3' region. In one case of AML with del(11)(q23), deletion of the MLL 3' region and the region telomeric to the MLL gene was seen. Three CLL cases with deletion of part or the entire 11q23 region showed deletion of one copy of MLL, but retention of the region telomeric to MLL. However, in four MDS cases with deletions involving the 11q23 region, deletions of both the MLL gene and the flanking regions of the MLL gene were observed. Hence, the deletions on 11q23 are different but overlapping for CLL and MDS, implicating different genes involved for these diseases.

Familial risk of lymphoproliferative tumors in families of patients with chronic lymphocytic leukemia: results from the Swedish Family-Cancer Database

The importance of genetic factors in etiology of chronic lymphocytic leukemia (CLL) is suggested by family and population studies. However, the spectrum of malignancies sharing common genetic factors with CLL and the effects of sex and age on familial risk are unknown. We used the Swedish Family-Cancer Database to test for increased familial risks of CLL and other lymphoproliferative tumors. Cancer diagnoses from 1958 to 1998 were assessed in 14 336 first-degree relatives of 5918 CLL cases and in 28 876 first-degree relatives of 11 778 controls. Cancer risks in relatives of cases were compared with those in relatives of controls using marginal survival models. Relatives of cases were at significantly increased risk for CLL (relative risk [RR] = 7.52; 95% confidence interval [CI], 3.63-15.56), for non-Hodgkin lymphoma (RR = 1.45; 95% CI, 0.98-2.16), and for Hodgkin lymphoma (RR = 2.35; 95% CI, 1.08-5.08). CLL risks were similar in parents, siblings, and offspring of cases, in male and female relatives, and were not affected by the case's age at diagnosis. Anticipation was not significant when analyzed using life table methods. We conclude that the familial component of CLL is shared with other lymphoproliferative malignances, suggesting common genetic pathways. However, because clinically diagnosed CLL is uncommon, absolute excess risk to relatives is small.

Dendritic cell-based immunotherapy in multiple myeloma

Most patients with multiple myeloma (MM) cannot be cured with currently available therapies. Although complete remission could be achieved in about 50% of newly diagnosed patients with high-dose chemotherapy and tandem transplantation, relapses of the underlying disease occur frequently. To realize long-term disease-free survival, it will be necessary to develop complementary therapies that are non-cross-resistant with chemotherapy. To this end, immunotherapy aimed at inducing or enhancing tumor-specific immunity that may control or eradicate remaining tumor cells may be an appealing method. Dendritic cells (DCs) are professional antigen-presenting cells and considered the best natural adjuvants for immunotherapy in malignancies. Vaccination with tumor antigen-pulsed DCs has been shown to be protective and therapeutic in animal tumor models, and induced a strong tumor-specific immunity and durable tumor regression in human solid tumors and B-cell lymphoma. As a result, clinical trials in various human malignancies have been initiated. This review will focus on DC-based immunotherapy in MM. I will discuss myeloma antigens and antigen-specific immune responses, the capacity of DCs to present myeloma antigens and induce cytotoxic T-cell responses, and clinical experience of DC vaccination in myeloma patients.

DNA variants in the ATM gene are not associated with sporadic rectal cancer in a Norwegian population-based study

BACKGROUND AND AIMS

A large number of DNA single-nucleotide polymorphisms (SNPs) have been discovered following the Human Genome Project. Several projects have been launched to find associations between SNPs and various disease cohorts. This study examined the possible association between the reported SNPs and sporadic rectal cancer. It has been proposed that SNPs in the ataxi-telangiectasia mutated (ATM) gene modulate the penetrance of some cancers. The investigated target sequence harbors three polymorphisms (IVS38-8 T/C in intron 38, 5557 G/A and 5558 A/T in exon 39), resulting in eight possible microhaplotypes at the DNA level. Furthermore, the two exonic SNPs are sited next to each other, allowing four possible amino acids in the same codon.

METHODS

We report on a new method analyzing SNPs and microhaplotypes based on theoretical thermodynamics and migration of variant fragments by cycling temperature capillary electrophoresis. Fluorophore-labeled PCR products were analyzed without any post-PCR steps on a standard 96 capillary-sequencing instrument under denaturing conditions.

RESULTS

More than 7000 alleles were microhaplotyped based on peak migration patterns of individual samples and sequencing results. The ATM polymorphisms and microhaplotypes examined did not significantly differ between sporadic rectal cancer and normal population.

CONCLUSION

No associations were found between the IVS38-8 T/C, 5557 G/A and 5558 A/T polymorphisms and microhaplotypes in the ATM gene with respect to sporadic rectal cancer.

ATM gene and lymphoid malignancies

Inherited biallelic mutations of the ATM (ataxia-telangiectasia mutated) gene cause ataxia-telangiectasia, a rare autosomal recessive disorder associated with a high incidence of childhood leukaemias and lymphomas, suggesting that ATM gene alterations may be involved in lymphomagenesis. Loss of heterozygosity at 11q22-23 (location of the ATM gene) is a frequent event in sporadic lymphoid tumours, and several studies have reported a high prevalence of ATM gene alterations in diverse sporadic lymphoproliferative disorders, adding evidence to the postulated contribution of ATM in the pathogenesis of these tumours. This mini-review will summarize the recently published data concerning the ATM gene in sporadic lymphoid malignancies and will discuss the apparent paradox between the predominance of nonsense mutations observed in patient with ataxia-telangiectasia and the high proportion of missense alterations found in sporadic lymphoid tumours.

Causation of chronic lymphocytic leukemia--insights from familial disease

In Western countries B-cell chronic lymphocytic leukemia (CLL) is the most common form of leukemia. Evidence from epidemiological studies and family studies strongly supports the notion that a subset of CLL involves inherited susceptibility. Identification of genes predisposing to CLL should be useful for diagnosis and treatment, as well as serving as a model for B-cell tumorigenesis in general. Here, we review the current status of knowledge about inherited susceptibility to CLL.

A genome scan of 18 families with chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) accounts for about 30% of all leukaemias and is most prevalent in older individuals. Significant familial aggregation has been demonstrated but the mode of inheritance is unknown. Recurrent cytogenetic abnormalities are frequently found in CLL tumour cells but no susceptibility genes have been confirmed. We have collected clinical data and biospecimens on families ascertained for having at least two living patients with CLL. The current study included DNA samples from 94 individuals (38 affected patients) in 18 families. We have carried out a genome scan using the ABI 28-panel medium density linkage mapping set (average spacing of 10 cM and average heterozygosity of 80%). Genotypes for 359 markers were scored. Multipoint limit of detection (lod) scores were calculated, assuming both dominant and recessive inheritance and allowing for increased penetrance with age and genetic heterogeneity. Non-parametric linkage scores were also calculated. Lod scores of 1.0 or greater were found on regions of chromosomes 1, 3, 6, 12, 13 and 17, but none of these loci achieved statistical significance. Four of these six regions (6q, 13q, 12 and 17p) coincide with areas where cytogenetic abnormalities are frequently observed in CLL tumour cells and are, therefore, strong candidate regions for containing germ line changes.