Mutational analysis of apoptotic genes in familial aggregation of hematological malignancies.

INTRODUCTION: Apoptosis deregulation have been associated to tumorigenesis process and was highlighted as a prominent hallmark of cancer. Several mutations have been reported in several forms of Blood cancer. However, it has never been investigated in familial aggregations of hematological malignancies. METHODS: In this study, we performed a mutational analysis by sequencing the entire coding regions in four key apoptotic genes FAS, FASLG, CASP8 and CASP10 in 92 independent families belonging to French and Tunisian populations and diagnosed with several forms of familial hematological malignancies. RESULTS: We report 15 genetic variations among which 7 were previously reported in several form of cancers and have a potential effect on gene expression. Particularly, the CASP8 variants p.Asp302His and p.Lys337Lys were detected in 15% and 10% of our group of patients respectively and were previously reported in association to breast cancer and to breast cancer susceptibility. DISCUSSION: In this study, we do not report the underlining deleterious mutations in familial hematological malignancies, but we describe some variants with potential risk of developing blood cancer. To gain further insights on the association between apoptosis pathway deregulation and familial hematological malignancies, more apoptotic genes should be investigated.

An overview of genetic predisposition to familial hematological malignancies.

Genetic predisposition has been always noted in the context of familial hematological malignancies. Epidemiological studies have provided evidence consisting of an increased risk to develop blood cancer in relatives diagnosed with the same pathology and characterized by early age at diagnosis and higher severity compared to sporadic forms. With the emergence of new genomic testing approaches, the prevalence of familial aggregations of hematological malignancies seems to be under estimated. The heterogeneity of clinical features explains the wide number of genes' mutations reported to date and the variable penetrance of variants. Nevertheless, the genetic basis of familial hematological malignancies is still not well understood. Identifying the genetic background in familial aggregations provides a valuable tool for prognostic evaluation, personalized treatment and better genetic counseling in high-risk families. Herein, we provide an overview of genes reported in the last few years in association to hematological malignancies including familial form of Hodgkin Lymphoma, Non-Hodgkin Lymphoma, Chronic Lymphocytic Leukemia, acute Myeloid Leukemia and acute Lymphoblastic Leukemia.

GATA2 gene analysis in several forms of hematological malignancies including familial aggregations.

The genetic predisposition to familial hematological malignancies has been previously reported highlighting inherited gene mutations. Several genes have been reported but genetic basis remains not well defined. In this study, we extended our investigation to a potential candidate GATA2 gene which was analyzed by direct sequencing in 119 cases including familial aggregations with a variety of hematological malignancies and sporadic acute leukemia belonging to Tunisian and French populations. We reported a deleterious p.Arg396Gln GATA2 mutation in one patient diagnosed with both sporadic acute myeloid leukemia (AML) and breast cancer. We also reported several GATA2 variations in familial cases. The absence of deleterious mutations in this large cohort of familial aggregations of hematological malignancies may strengthen the hypothesis that GATA2 mutations are an important predisposing factor, although as a secondary genetic event, required for the development of overt malignant disease.

ARLTS1, potential candidate gene in familial aggregation of hematological malignancies.

INTRODUCTION: Genetic predisposition to familial hematological malignancies was previously described through several epidemiological analyses, but the genetic basis remains unclear. The tumor-suppressor ARLTS1 gene was previously described in sporadic hematological malignancies and familial cancer context. METHODS: In this study, we sequence the ARLTS1 gene in 100 patients belonging to 88 independent Tunisian and French families. RESULTS: After gene sequencing, we report 8 genetic variations, most of which were previously reported in several cancer forms. The most common variants were W149X and C148R and were previously associated to B-cell chronic lymphocytic leukemia and to high-risk of familial breast cancer. CONCLUSIONS: These results emphasize the fact that ARLTS1 gene mutations can be considered as a potential predisposing factor in familial hematological malignancies and other several cancer forms.

Mutational analysis of TP53 gene in Tunisian familial hematological malignancies and sporadic acute leukemia cases.

Mutations are responsible for familial cancer syndromes which account for approximately 5-10 % of all types of cancers. Familial cancers are often caused by genetic alterations occurring either in tumor suppressor or genomic stability genes such as TP53. In this study, we have analyzed the TP53 gene by direct sequencing approach, in a panel of 18 Tunisian familial hematological malignancies cases including several forms of leukemia, lymphoma and myeloid syndrome and 22 cases of sporadic acute leukemia. In one familial case diagnosed with acute lymphoblastic leukemia, we reported an intronic substitution 559+1 G>A which may disrupt the splice site and impact the normal protein function. Most of the deleterious mutations (Arg158His; Pro282Trp; Thr312Ser) as classified by IARC data base, were commonly reported in ALL cases studied here. The cosegregation of the two variants rs1042522 and rs1642785 was observed in most patients which may be in favor of the presence of linkage disequilibrium. The most defined TP53 mutations found here were identified in acute lymphoblastic leukemia context whereas only 3 % of mutations have been in previous studies. The cosegregation of the two recurrent variant rs1042522 and rs1642785 should be further confirmed.

Combined IKZF1 and IG markers as new tools for diagnosis and minimal residual disease assessment in Tunisian B-ALL.

INTRODUCTION: The monitoring of minimal residual disease (MRD) approach in patients diagnosed with B-acute lymphoblastic leukemia (B-ALL) allows an early detection of residual clones inducing relapses and therefore appropriate therapy strategy. The molecular markers may identify and quantify the residual blasts in B-ALL with normal cytology. In this study, we aimed to use combined IKZF1, IGH and IGK immunoglobulin genes for diagnosis and MRD monitoring in B-ALL sample using MLPA, multiplex PCR and real-time quantitative PCR. MATERIAL: We showed that multiplex PCR and MLPA are necessary and complementary to detect IKZF1 deletions. RESULTS: We have identified at the diagnosis clonal IGH rearrangement (VH3-JH5) and IKZF1 deletion (Δ4-7), which we have used it for MRD evaluation after induction chemotherapy. Despite the absence of chromosome abnormality, the patient may be classified in high-risk group with a relapse rate of residual blasts>10-4 and sensitivity up to 10-5. This molecular approach enabled the patient's stratification, which was overlooked by classical methods. CONCLUSION: The combined IKZF1 and immunoglobulin genes will be used as appropriate molecular tools for diagnosis and MRD assessment of B-lineage leukemias and introduced as a routine tests in Tunisian clinical laboratories. They will be useful to stratify patients into risk groups leading to better treatment strategy.

Familial hematological malignancies: new IDH2 mutation.

Isocitrate dehydrogenase IDH 1 and IDH 2 mutations were reported in several cancer forms, especially in hematological malignancies, but were never been investigated in familial aggregation. The aim of this study is to determine whether germline isocitrate dehydrogenase genes mutations are involved.We targeted IDH1 and IDH2 genes in 104 familial cases belonging to Tunisian and French populations, including several forms of hematological malignancies and cosegregated solid tumors.We report one IDH1 variant: c.315 G>T, p.Gly105Gly in 15 % of cases, which was assigned to the worst outcome in several studies. Three IDH2 variants were found, among them, one intronic substitution c.543+45 G>A (rs142033117) and two new variants not previously described: c.389 A>T, p.Lys130Met and c.414 T>C, p.Thr138Thr. The p.Lys130Met was found in one case diagnosed with Waldenstrom's disease with familial history of cancer. The enrolled in silico analysis, the functional study, and the absence of this variant in control population strengthen the hypothesis of its deleterious effect.From an extended number of candidate genes analyzed in familial hematological malignancies, IDH2 might be considerably involved since we reported a potential damaging effect.

Minimal Residual Disease assessment of IDH1/2 mutations in Acute Myeloid Leukemia by LNA-RQ-PCR.

BACKGROUND: With the growing importance of minimal residual disease (MRD) monitoring and the recent discover of IDH mutations in acute myeloid leukemia (AML), the quantification of this molecular marker provides the possibility to monitor the disease progression and the therapy efficacy. OBJECTIVE: The aim of this study is to assess the MRD in AML for the first time with IDH1 and IDH2 gene mutations in 15 AML patients. METHODS: We have screened R132 IDH1, R140 IDH2 and R172 IDH2 mutations by PCR amplification and direct sequencing and we have quantified them for the first time by RQ-PCR using reverse primers modified by an LNA. A good sensitivity has been obtained. MRD rates obtained by LNA-RQ-PCR were used to draw kinetics of the disease evolution during the follow-up. RESULTS: IDH1/2 Results were compared to NPM1 mutation and WT1 over expression and have showed coherent kinetic between MRD rates in 7/11 cases. For the rest, the direct sequencing and the high resolution melting (HRM) assay have confirmed the quantification Results in diagnosis but not in residual samples. CONCLUSION: Some optimization will be necessary to improve the mutated allele amplification. The LNA-RQ-PCR might be an easy and less cost method used in a small laboratory for myeloid leukemia MRD assessment using IDH1/2 mutations.

Mutational analysis of JAK2, CBL, RUNX1, and NPM1 genes in familial aggregation of hematological malignancies.

Familial aggregation of hematological malignancies has been reported highlighting inherited genetic predisposition. In this study, we targeted four candidate genes: JAK2 and RUNX1 genes assuring a prominent function in hematological process and CBL and NPM1 as proto-oncogenes. Their disruption was described in several sporadic hematological malignancies. The aim of this study is to determine whether JAK2, CBL, RUNX1, and NPM1 germline genes mutations are involved in familial hematological malignancies. Using direct sequencing, we analyzed JAK2 (exons 12 and 14); CBL (exons 7, 8 and 9); NPM1 (exon 12) and the entire RUNX1 in 88 independent families belonging to Tunisian and French populations. Twenty-one sporadic acute leukemias were included in this study. We reported a heterozygous intronic c.1641 + 6 T > C JAK2 variant (rs182123615) found in two independent familial cases diagnosed with gastric lymphoma and Hodgkin lymphoma. The in silico analysis suggested a potential impact on splicing, but the functional splicing minigene reporter assay on rs182123615 variant showed no aberrant transcripts. In one sporadic acute myeloblastic leukemia, we reported an insertion 846 in. TGTT in exon 12 of NPM1 gene that may impact the normal reading frame. The rs182123615 JAK2 variant was described in several contexts including myeloproliferative neoplasms and congenital erythrocytosis and was supposed to be pathogenic. Through this current study, we established the assessment of pathogenicity of rs182123615 and we classified it rather as rare polymorphism.