Pregnancy outcomes in prenatally diagnosed 47, XXX and 47, XYY syndromes: a 30-year French, retrospective, multicentre study.

OBJECTIVE: Sex chromosome aneuploidies are frequently detected fortuitously in a prenatal diagnosis. Most cases of 47, XXX and 47, XYY syndromes are diagnosed in this context, and parents are thus faced with an unexpected situation. The objective of the present study was to characterize a French cohort of prenatally diagnosed cases of 47, XXX and 47, XYY and to evaluate the termination of pregnancy (TOP) rate before and after France's implementation of multidisciplinary centres for prenatal diagnosis in 1997. METHODS: This retrospective study identified respectively 291 and 175 cases of prenatally diagnosed 47, XXX and 47, XYY between 1976 and 2012. For each case, the indication, maternal age, karyotype and outcome were recorded. RESULTS: Most diagnoses of the two conditions were fortuitous. The occurrence of 47, XXX was associated with advanced maternal age. The overall TOP rate was higher for 47, XXX (22.9%) than for 47, XYY (14.6%), although this difference was not statistically significant. However, the TOP rates fell significantly after 1997 (from 41.1% to 11.8% for 47, XXX and from 25.8% to 6.7% for 47, XYY). CONCLUSION: The TOP rates after prenatal diagnoses of 47, XXX and 47, XYY fell significantly after 1997, following France's implementation of multidisciplinary centres for prenatal diagnosis. © 2016 John Wiley & Sons, Ltd.

Genetic differences between paediatric and adult Burkitt lymphomas.

Dysregulation of MYC is the genetic hallmark of Burkitt lymphoma (BL) but it is encountered in other aggressive mature B-cell lymphomas. MYC dysregulation needs other cooperating events for BL development. We aimed to characterize these events and assess the differences between adult and paediatric BLs that may explain the different outcomes in these two populations. We analysed patterns of genetic aberrations in a series of 24 BLs: 11 adults and 13 children. We looked for genomic imbalances (copy number variations), copy-neutral loss of heterozygosity (CN-LOH) and mutations in TP53, CDKN2A, ID3 (exon 1), TCF3 (exon17) and CCND3 (exon 6). Young patients displayed more frequent 13q31.3q32.1 amplification, 7q32q36 gain and 5q23.3 CN-LOH, while 17p13 and 18q21.3 CN-LOH were only detected in adult BLs. ID3 mutations were present in all adult samples, but only in 42% of childhood cases. CCND3 and ID3 double-hit mutations, as well as 18q21 CN-LOH, seemed to be associated with poorer outcome. For the first time, we report different genetic anomalies between adult and paediatric BLs, suggesting age-related heterogeneity in Burkitt lymphomagenesis. This may explain the poorer prognosis of adult BLs. Additional studies are needed to confirm these results in the setting of clinical trials.

14q deletions are associated with trisomy 12, NOTCH1 mutations and unmutated IGHV genes in chronic lymphocytic leukemia and small lymphocytic lymphoma.

Deletions of the long arm of chromosome 14 [del(14q)] are rare but recurrently observed in mature B-cell neoplasms, particularly in chronic lymphocytic leukemia (CLL). To further characterize this aberration, we studied 81 cases with del(14q): 54 of CLL and 27 of small lymphocytic lymphoma (SLL), the largest reported series to date. Using karyotype and fluorescence in situ hybridization (FISH), the most frequent additional abnormality was trisomy 12 (tri12), observed in 28/79 (35%) cases, followed by del13q14 (12/79, 15%), delTP53 (11/80, 14%) delATM (5/79, 6%), and del6q21 (3/76, 4%). IGHV genes were unmutated in 41/53 (77%) patients, with a high frequency of IGHV1-69 (21/52, 40%). NOTCH1 gene was mutated in 14/45 (31%) patients. There was no significant difference in cytogenetic and molecular abnormalities between CLL and SLL. Investigations using FISH and SNP-array demonstrated the heterogeneous size of the 14q deletions. However, a group with the same del(14)(q24.1q32.33) was identified in 48% of cases. In this group, tri12 (P = 0.004) and NOTCH1 mutations (P = 0.02) were significantly more frequent than in the other patients. In CLL patients with del(14q), median treatment-free survival (TFS) was 27 months. In conclusion, del(14q) is associated with tri12 and with pejorative prognostic factors: unmutated IGHV genes (with over-representation of the IGHV1-69 repertoire), NOTCH1 mutations, and a short TFS.

Development of primary early-onset colorectal cancers due to biallelic mutations of the FANCD1/BRCA2 gene.

Fanconi anaemia (FA) is characterized by progressive bone marrow failure, congenital anomalies, and predisposition to malignancy. In a minority of cases, FA results from biallelic FANCD1/BRCA2 mutations that are associated with early-onset leukaemia and solid tumours. Here, we describe the clinical and molecular features of a remarkable family presenting with multiple primary colorectal cancers (CRCs) without detectable mutations in genes involved in the Mendelian predisposition to CRCs. We unexpectedly identified, despite the absence of clinical cardinal features of FA, a biallelic mutation of the FANCD1/BRCA2 corresponding to a frameshift alteration (c.1845_1846delCT, p.Asn615Lysfs*6) and a missense mutation (c.7802A>G, p.Tyr2601Cys). The diagnosis of FA was confirmed by the chromosomal analysis of lymphocytes. Reverse transcriptase (RT)-PCR analysis revealed that the c.7802A>G BRCA2 variation was in fact a splicing mutation that creates an aberrant splicing donor site and results partly into an aberrant transcript encoding a truncated protein (p.Tyr2601Trpfs*46). The atypical FA phenotype observed within this family was probably explained by the residual amount of BRCA2 with the point mutation c.7802A>G in the patients harbouring the biallelic FANCD1/BRCA2 mutations. Although this report is based in a single family, it suggests that CRCs may be part of the tumour spectrum associated with FANCD1/BRCA2 biallelic mutations and that the presence of such mutations should be considered in families with CRCs, even in the absence of cardinal features of FA.

Chromosomal translocations involving the IGH@ locus in B-cell precursor acute lymphoblastic leukemia: 29 new cases and a review of the literature.

Chromosomal translocations involving the immunoglobulin heavy chain locus (IGH@) are recurrent but rare in B-cell precursor acute lymphoblastic leukemia (BCP-ALL), and various partner genes have been described. Here, we report a new series of 29 cases of BCP-ALL with IGH@ translocations. The partner gene was identified by fluorescence in situ hybridization and/or molecular cloning in 20 patients. Members of the CEBP gene family (n = 11), BCL2 (n = 3), ID4 (n = 3), EPOR (n = 2), and TRA/D@ (n = 1) were identified and demonstrated by quantitative real-time reverse transcriptase-polymerase chain reaction to be markedly up-regulated. The present cases, added to those already reported, confirm the diversity of the partner genes, which, apart from BCL2, are specific to BCP-ALL. Collectively, patients with IGH@ translocations may represent a novel sub-group of BCP-ALL occurring in adolescents and young adults.

Patterns of genomic aberrations suggest that Burkitt lymphomas with complex karyotype are distinct from other aggressive B-cell lymphomas with MYC rearrangement.

We previously showed that complex karyotypes (CK) and chromosome 13q abnormalities have an adverse prognostic impact in childhood Burkitt lymphomas/leukemias (BL) and diffuse large B-cell lymphomas (DLBCL). The aim of our study was to identify recurrent alterations associated with MYC rearrangements in aggressive B-cell lymphomas with CK. Multicolor fluorescence in situ hybridization (M-FISH) was performed in 84 patient samples (59 adults and 25 children), including 37 BL (13 lymphomas and 24 acute leukemias), 12 DLBCL, 28 B-cell lymphomas with intermediate features (DLBCL/BL), 4 B-cell precursor acute lymphoblastic leukemias (BCP-ALL), and 3 unclassifiable B-cell lymphomas. New (cytogenetically undetected) abnormalities were identified in 80% of patients. We also refined one-third of the chromosomal aberrations detected by karyotyping. M-FISH proved to be more useful in identifying chromosomal partners involved in unbalanced translocations and in revealing greater complexity of 13q rearrangements. Most of the newly identified or refined recurrent alterations involved 1q, 13q and 3q (gains/losses), 7q and 18q (gains), or 6q (losses), suggesting that these secondary aberrations may play a role in lymphomagenesis. Several patterns of genomic aberrations were identified: 1q gains in BL, trisomies 7 in DLBCL, and 18q-translocations in adult non-BL. BCP-ALL usually displayed an 18q21 rearrangement. BL karyotypes were less complex and aneuploid than those of other MYC-rearranged lymphomas. BCP-ALL and DLBCL/BL were associated with a higher rate of early death than BL and DLBCL. These findings support the categorization of DLBCL/BL as a distinct entity and suggest that BL with CK are indeed different from other aggressive MYC-rearranged lymphomas, which usually show greater genetic complexity. © 2012 Wiley Periodicals, Inc.

The 2q37-deletion syndrome: an update of the clinical spectrum including overweight, brachydactyly and behavioural features in 14 new patients.

The 2q37 locus is one of the most commonly deleted subtelomeric regions. Such a deletion has been identified in >100 patients by telomeric fluorescence in situ hybridization (FISH) analysis and, less frequently, by array-based comparative genomic hybridization (array-CGH). A recognizable '2q37-deletion syndrome' or Albright's hereditary osteodystrophy-like syndrome has been previously described. To better map the deletion and further refine this deletional syndrome, we formed a collaboration with the Association of French Language Cytogeneticists to collect 14 new intellectually deficient patients with a distal or interstitial 2q37 deletion characterized by FISH and array-CGH. Patients exhibited facial dysmorphism (13/14) and brachydactyly (10/14), associated with behavioural problems, autism or autism spectrum disorders of varying severity and overweight or obesity. The deletions in these 14 new patients measured from 2.6 to 8.8 Mb. Although the major role of HDAC4 has been demonstrated, the phenotypic involvement of several other genes in the deleted regions is unknown. We further refined the genotype-phenotype correlation for the 2q37 deletion. To do this, we examined the smallest overlapping deleted region for candidate genes for skeletal malformations (facial dysmorphism and brachydactyly), overweight, behavioural problems and seizures, using clinical data, a review of the literature, and the Manteia database. Among the candidate genes identified, we focus on the roles of PRLH, PER2, TWIST2, CAPN10, KIF1A, FARP2, D2HGDH and PDCD1.

Chromosomal aberrations and their prognostic value in a series of 174 untreated patients with Waldenström's macroglobulinemia.

Waldenström's macroglobulinemia is a disease of mature B cells, the genetic basis of which is poorly understood. Few recurrent chromosomal abnormalities have been reported, and their prognostic value is not known. We conducted a prospective cytogenetic study of Waldenström's macroglobulinemia and examined the prognostic value of chromosomal aberrations in an international randomized trial. The main aberrations were 6q deletions (30%), trisomy 18 (15%), 13q deletions (13%), 17p (TP53) deletions (8%), trisomy 4 (8%), and 11q (ATM) deletions (7%). There was a significant association between trisomy of chromosome 4 and trisomy of chromosome 18. Translocations involving the IGH genes were rare (<5%). Deletion of 6q and 11q, and trisomy 4, were significantly associated with adverse clinical and biological parameters. Patients with TP53 deletion had short progression-free survival and short disease-free survival. Although rare (<5%), trisomy 12 was associated with short progression-free survival. In conclusion, the cytogenetic profile of Waldenström's macroglobulinemia appears to differ from that of other B-cell lymphomas. Chromosomal abnormalities may help with diagnosis and prognostication, in conjunction with other clinical and biological characteristics.

Specific skin lesions in chronic myelomonocytic leukemia: a spectrum of myelomonocytic and dendritic cell proliferations: a study of 42 cases.

Chronic myelomonocytic leukemia (CMML) is a rare clonal hematopoietic disorder that can also involve the skin. The histopathology of these skin lesions is not clearly defined, and few data are available in the literature. To better understand tumoral skin involvements in CMML we carried out an extensive, retrospective clinicopathologic study of 42 cases selected from the database of the French Study Group of Cutaneous Lymphomas. On the basis of clinical data, morphology, and phenotype we identified 4 clinicopathologic profiles representing 4 distinct groups. The first group comprised myelomonocytic cell tumors (n=18), exhibiting a proliferation of granulocytic or monocytic blast cells, which were CD68 and/or MPO positive but negative for dendritic cell markers. The second group comprised mature plasmacytoid dendritic cell tumors (n=16), denoted by a proliferation of mature plasmacytoid dendritic cells, which were CD123, TCL1, and CD303 positive but CD56, CD1a, and S100 negative. The third group comprised blastic plasmacytoid dendritic cell tumors (n=4), characterized by a proliferation of monomorphous medium-sized blast cells, which were CD4, CD56, CD123, TCL1 positive but CD1a and S100 negative. The fourth group consisted of a putatively novel category of tumor that we named blastic indeterminate dendritic cell tumors (n=4), distinguished by a proliferation of large blast cells that not only exhibited monocytic markers but also the dendritic markers CD1a and S100. These 4 groups showed distinctive outcomes. Finally, we showed, by fluorescence in situ hybridization analysis, a clonal link between bone marrow disease and skin lesions in 4 patients. Herein, we have described a novel scheme for pathologists and physicians to handle specific lesions in CMML, which correspond to a spectrum of myelomonocytic and dendritic cell proliferations with different outcomes. A minimal panel of immunohistochemical markers including CD68, CD1a, S100, Langerin, and CD123 is necessary to make the correct classification in this spectrum of cutaneous CMML tumors, in which dendritic cell lineage plays an important role.

PICALM-MLLT10 acute myeloid leukemia: a French cohort of 18 patients.

The PICALM-MLLT10 fusion gene, generated by the t(10;11)(p12-13;q14-21) translocation, is a rare but recurrent event in acute leukemias. In this study, we assessed the characteristics and outcome of 18 PICALM-MLLT10 AML patients. As compared with non PICALM-MLLT10 patients (n=72), PICALM-MLLT10 AML were characterized by more frequent extramedullary diseases, CD7 expression and higher platelet counts. Three out of four therapy-related PICALM-MLLT10 AMLs had been previously treated for diffuse large B-cell lymphoma. The complete response rate was 71% after intensive chemotherapy. PICALM-MLLT10 patients had a shorter median overall survival than patients with favorable cytogenetics (12 months vs. not reached, p=0.07) but not significantly different from those of intermediate (26 months, p=0.32) or unfavorable cytogenetic groups (8 months, p=0.13). Long term responses were achieved in a subset of patients after allogeneic stem-cell transplantation but also after high-dose cytarabine.

Alpha-interferon secreting blastic plasmacytoid dendritic cells neoplasm: a case report with histological, molecular genetics and long-term tumor cells culture studies.

We report a new case of blastic plasmacytoid dendritic cell neoplasm (BPDCN) with extensive immunophenoptyping, genotyping (karyotype, array-comparative genomic hybridization, and fluorescent in situ hybridization), and long-term tumor cells culture. BPDCN is a very rare and aggressive disease clinically characterized by a skin revealing localization more or less rapidly disseminating to the bone marrow and other organs with or without and leukemia. The disease was initially phenotypically characterized by the expression of both CD4 and CD56 antigens, whereas lymphoid and myeloid lineage antigens were negative. A phenotypic link with alpha-interferon (IFN-I)-producing plasmacytoid dendritic cells was demonstrated. The data collected in this case report provide additional biological and genotypical data on tumor cells of BPDCN. This study confirms the capability of tumor cells to secrete IFN-I, demonstrated by biological IFN-I activity of cultured cells and immunohistochemical expression of Mx-1 protein. Although a common genetic profile involving chromosomes 5, 6, 9, 12, 13, and 15 has been identified, no specific genetic marker has been demonstrated that is specific to BPDCN. The demonstration of ETV6 gene deletion in this case deserves further investigations as a putative BPDCN marker.

PRDM16 (1p36) translocations define a distinct entity of myeloid malignancies with poor prognosis but may also occur in lymphoid malignancies.

The PRDM16 (1p36) gene is rearranged in acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) with t(1;3)(p36;q21), sharing characteristics with AML and MDS with MECOM (3q26.2) translocations. We used fluorescence in situ hybridization to study 39 haematological malignancies with translocations involving PRDM16 to assess the precise breakpoint on 1p36 and the identity of the partner locus. Reverse-transcription polymerase chain reaction (PCR) was performed in selected cases in order to confirm the partner locus. PRDM16 expression studies were performed on bone marrow samples of patients, normal controls and CD34(+) cells using TaqMan real-time quantitative PCR. PRDM16 was rearranged with the RPN1 (3q21) locus in 30 cases and with other loci in nine cases. The diagnosis was AML or MDS in most cases, except for two cases of lymphoid proliferation. We identified novel translocation partners of PRDM16, including the transcription factors ETV6 and IKZF1. Translocations involving PRDM16 lead to its overexpression irrespective of the consequence of the rearrangement (fusion gene or promoter swap). Survival data suggest that patients with AML/MDS and PRDM16 translocations have a poor prognosis despite a simple karyotype and a median age of 65 years. There seems to be an over-representation of late-onset therapy-related myeloid malignancies.

Refinement of 1p36 alterations not involving PRDM16 in myeloid and lymphoid malignancies.

Fluorescence in situ hybridization was performed to characterize 81 cases of myeloid and lymphoid malignancies with cytogenetic 1p36 alterations not affecting the PRDM16 locus. In total, three subgroups were identified: balanced translocations (N = 27) and telomeric rearrangements (N = 15), both mainly observed in myeloid disorders; and unbalanced non-telomeric rearrangements (N = 39), mainly observed in lymphoid proliferations and frequently associated with a highly complex karyotype. The 1p36 rearrangement was isolated in 12 cases, mainly myeloid disorders. The breakpoints on 1p36 were more widely distributed than previously reported, but with identifiable rare breakpoint cluster regions, such as the TP73 locus. We also found novel partner loci on 1p36 for the known multi-partner genes HMGA2 and RUNX1. We precised the common terminal 1p36 deletion, which has been suggested to have an adverse prognosis, in B-cell lymphomas [follicular lymphomas and diffuse large B-cell lymphomas with t(14;18)(q32;q21) as well as follicular lymphomas without t(14;18)]. Intrachromosomal telomeric repetitive sequences were detected in at least half the cases of telomeric rearrangements. It is unclear how the latter rearrangements occurred and whether they represent oncogenic events or result from chromosomal instability during oncogenesis.

Dismal prognostic value of monosomal karyotype in elderly patients with acute myeloid leukemia: a GOELAMS study of 186 patients with unfavorable cytogenetic abnormalities.

The prognosis of acute myeloid leukemia (AML) is very poor in elderly patients, especially in those classically defined as having unfavorable cytogenetics. The recent monosomal karyotype (MK) entity, defined as 2 or more autosomal monosomies or combination of 1 monosomy with structural abnormalities, has been reported to be associated with a worse outcome than the traditional complex karyotype (CK). In this retrospective study of 186 AML patients older than 60 years, the prognostic influence of MK was used to further stratify elderly patients with unfavorable cytogenetics. CK was observed in 129 patients (69%), and 110 exhibited abnormalities according to the definition of MK (59%). MK(+) patients had a complete response rate significantly lower than MK(-) patients: 37% vs 64% (P = .0008), and their 2-year overall survival was also decreased at 7% vs 22% (P < .0001). In multivariate analysis, MK appeared as the major independent prognostic factor related to complete remission achievement (odds ratio = 2.3; 95% confidence interval, 1-5.4, P = .05) and survival (hazard ratio = 1.7; 95% confidence interval, 1.1-2.5, P = .008). In the subgroup of 129 CK(+) patients, survival was dramatically decreased for MK(+) patients (8% vs 28% at P = .03). These results demonstrate that MK is a major independent factor of very poor prognosis in elderly AML.

Twenty-five years of epidemiological recording on myeloid malignancies: data from the specialized registry of hematologic malignancies of Cote d'Or (Burgundy, France).

BACKGROUND: Epidemiological data on myeloid malignancies are very rare in the literature due to a lack of registration by cancer registries until 2000. The Registry of Hematologic Malignancies of the Côte d'Or Department in France has, however, steadfastly registered data on cases occurring in the Department since 1980, resulting, to date, in a database of over 5,000 cases classified according to the ICD-O-3 classification, following the most recent World Health Organization classification criteria. DESIGN AND METHODS: Twenty-five years of data on myeloid malignancies, including acute myeloid leukemia, myeloproliferative neoplasms, myelodysplastic syndromes and myelodysplastic/myeloproliferative syndromes were analyzed. World population standardized incidence rates were calculated as were as observed and relative survival. RESULTS: Incidence rates per 100,000 inhabitants/year were 2.5 for acute myeloid leukemia, 1.3 for myelodysplastic syndromes, 3.2 for myeloproliferative neoplasms and 0.6 for myelodysplastic/myeloproliferative syndromes. It was found that the incidence rate of myelodysplastic syndromes increased significantly over the period. The median overall survival is 8.9 months for patients with acute myeloid leukemia, 33.8 months for patients with myelodysplastic syndromes, 91.7 months for those with myeloproliferative neoplasms and 26.6 months for patients with myelodysplastic/myeloproliferative syndromes. Observed and relative 20-year survival rates are, respectively, 12% and 13% in acute myeloid leukemia, 2% and 6% in myelodysplastic syndromes and 20% and 34% in myeloproliferative neoplasms. CONCLUSIONS: These population-based data on myeloid malignancies are the first data collected over such a long period and provide interesting information for clinicians and public health authorities, particularly given the paucity of other long-term, population-based data from cancer registries.

Specific chromosomal IG translocations have different prognoses in chronic lymphocytic leukemia.

BACKGROUND: Chromosomal translocations are usually analyzed as a single entity, and are associated with a poor outcome in chronic lymphocytic leukemia. Translocations involving immunoglobulin genes are recurrent, but uncommon (<5%), and their individual prognosis is not clear. The two most frequent partners are BCL2 (18q21) and BCL3 (19q13). DESIGNS AND METHODS: Herein, 75 cases are reported of chronic lymphocytic leukemia and t(14;18) (BCL2-CLLs). Our series benefits from morphological, immunological and cytogenetical reviews. The IGHV status analyses were performed by referring laboratories. Comparison was made with our previously published series of chronic lymphocytic leukemia patients with t(14;19) (BCL3-CLLs, n=29). RESULTS: Compared with BCL3-CLLs, lymphocytosis was lower in BCL2-CLLs (p<0.008), and splenomegaly was less frequent (p<0.0001). There were more "typical" morphologies (p<0.005) and Matutes scores >4 (p<0.001) in the BCL2-CLLs group, and less CD38 expression (p<0.04). More variant BCL2-translocations were observed (t(18;22), n=11; 2t(2;18), n=2; p<0.02), and BCL2-translocation was frequently single (p<0.002). Complex karyotypes (p<0.02), trisomy 12 (p<0.03), 6q deletion (p<0.002) and TP53 deletion (p<0.02) were less frequent in BCL2-CLLs, whereas 13q deletion was more frequent (p<0.005). The IGHV gene was frequently mutated in BCL2-CLLs (p<0.0001). Treatment-free survival was longer in BCL2-CLLs (p<0.0001). CONCLUSIONS: BCL2-CLL.S express CD5 and lack expression of CD38, and have a Matutes score ≥4, frequent trisomy 12, no ATM and 6q deletions, and a mutated IGHV status. Compared to BCL3-CLLs, BCL2-CLLs are much less aggressive; indicating that identifying individual translocations and cytogenetic partners would allow improved patient stratification.

Chromosomal abnormalities in transformed Ph-negative myeloproliferative neoplasms are associated to the transformation subtype and independent of JAK2 and the TET2 mutations.

Evolution to myelofibrosis (MF), acute myeloid leukemia or myelodysplastic syndrome (AML/MDS) may occur over time in myeloproliferative neoplasms (MPN) patients most likely due to the acquisition of additional mutations. The Groupe Francophone de cytogenetique hematologique (GFCH) has collected and reviewed 82 patients with transformation of MPN (66 AML/MDS and 16 MF). JAK2V617F and TET2 mutations were searched for in 40 and 32 patients, respectively. Significantly more -7/del(7q) (P = 0.004) and -5/del(5q) (P = 0.03) were found in AML/MDS with a higher incidence of dup1q (P = 0.01) in MF. Some specific chromosomal abnormalities occurred together, for example -5/del(5q) and -17/del(17p) (P = 0.0007). In multivariate analysis, two factors were independently associated with an inferior overall survival (OS); AML/MDS transformation (P < 0.0001) and -5/del(5q) abnormality (P = 0.02). Although both giving rise to loss of 7q, der(1;7) differed from other 7q deletions in terms of distribution (lower frequency of AML/MDS, P = 0.02), association with chromosomal abnormalities (absence of -5/del(5q), P = 0.003; increased del(20q), P = 0.05), and longer OS (P = 0.0007). We detected 24/40 (60%) JAK2V617F and 8/25 (32%) TET2 mutations in samples following transformation, ranging from wild-type to mutated forms of both genes. The mutated and wild-type forms of the genes were not found to be associated with a specific chromosomal abnormality. There was no evidence that JAK2 or TET2 mutations were associated with the type of MPN transformation, whereas the type of cytogenetic abnormalities were strongly linked, perhaps indicating that they play a specific role in the transformation process.

Wide diversity of PAX5 alterations in B-ALL: a Groupe Francophone de Cytogenetique Hematologique study.

PAX5 is the main target of somatic mutations in acute B lymphoblastic leukemia (B-ALL). We analyzed 153 adult and child B-ALL harboring karyotypic abnormalities at chromosome 9p, to determine the frequency and the nature of PAX5 alterations. We found PAX5 internal rearrangements in 21% of the cases. To isolate fusion partners, we used classic and innovative techniques (rolling circle amplification-rapid amplification of cDNA ends) and single nucleotide polymorphism-comparative genomic hybridization arrays. Recurrent and novel fusion partners were identified, including NCoR1, DACH2, GOLGA6, and TAOK1 genes showing the high variability of the partners. We noted that half the fusion genes can give rise to truncated PAX5 proteins. Furthermore, malignant cells carrying PAX5 fusion genes displayed a simple karyotype. These data strongly suggest that PAX5 fusion genes are early players in leukemogenesis. In addition, PAX5 deletion was observed in 60% of B-ALL with 9p alterations. Contrary to cases with PAX5 fusions, deletions were associated with complex karyotypes and common recurrent translocations. This supports the hypothesis of the secondary nature of the deletion. Our data shed more light on the high variability of PAX5 alterations in B-ALL. Therefore, it is probable that gene fusions occur early, whereas deletions should be regarded as a late/secondary event.