MYC translocation in chronic lymphocytic leukaemia is associated with increased prolymphocytes and a poor prognosis

Plasmablastic transformation of chronic lymphocytic leukemia: a review of literature and report on 2 cases

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is the most common leukemia in adults in Western countries. Transformation of CLL/SLL to plasmablastic lymphoma (PBL) is exceedingly rare and often has an extremely poor response to treatment. A thorough molecular workup may help in determining clonality-relatedness and prognosis. We describe two cases of CLL/SLL that transformed into PBL, with an extensive molecular workup in one case, and a review of the literature.

Dysregulation of PRMT5 in chronic lymphocytic leukemia promotes progression with high risk of Richter's transformation

Richter's Transformation (RT) is a poorly understood and fatal progression of chronic lymphocytic leukemia (CLL) manifesting histologically as diffuse large B-cell lymphoma. Protein arginine methyltransferase 5 (PRMT5) is implicated in lymphomagenesis, but its role in CLL or RT progression is unknown. We demonstrate herein that tumors uniformly overexpress PRMT5 in patients with progression to RT. Furthermore, mice with B-specific overexpression of hPRMT5 develop a B-lymphoid expansion with increased risk of death, and Eµ-PRMT5/TCL1 double transgenic mice develop a highly aggressive disease with transformation that histologically resembles RT; where large-scale transcriptional profiling identifies oncogenic pathways mediating PRMT5-driven disease progression. Lastly, we report the development of a SAM-competitive PRMT5 inhibitor, PRT382, with exclusive selectivity and optimal in vitro and in vivo activity compared to available PRMT5 inhibitors. Taken together, the discovery that PRMT5 drives oncogenic pathways promoting RT provides a compelling rationale for clinical investigation of PRMT5 inhibitors such as PRT382 in aggressive CLL/RT cases.

Chronic lymphocytic leukaemia/small lymphocytic lymphoma and mantle cell lymphoma: from early lesions to transformation

The International Clinical Advisory Committee reviewed advances in our understanding of the clinicopathologic and biologic features of chronic lymphocytic leukaemia/small lymphocytic lymphoma, B-cell prolymphocytic leukaemia, and mantle cell lymphoma since the revised 4th edition of the WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues. Discussions amongst pathologists, clinicians, and molecular geneticists around these diseases focussed on incorporating new knowledge into the next classification system. In this manuscript, we review these disease entities and incorporate results of these deliberations, including advances in our understanding of early lesions and transformation.

A new case of trisomy 5 with complex karyotype abnormalities in B-cell prolymphocytic leukemia: a case study

Background

The B-cell prolymphocytic leukemia (B-PLL) diagnosis is challenging due to the superposition with mature B-cell leukemia and/or lymphoma.

Objective

An insight case study of trisomy 5 with complex karyotype abnormalities in B-cell prolymphocytic leukemia.

Subject and methods

A 72-year-old man was referred to the Hematology Department, Qilu Hospital, Shandong University, because of persistent fever (10 days) and lymphocytosis. A detailed diagnostic methods including complete blood count, bone marrow aspiration, flow cytometry, conventional karyotype analysis, fluorescence in situ hybridization (FISH), quantitative real-time polymerase chain reaction (qRT-PCR), next-generation sequencing technology (NGS) used to detect 41 kinds of mutant genes related to hematological malignancies were conducted and reasonable therapeutic regimens including emergent leukapheresis accompanied by basification of urine and hydrotherapy, followed by a regimen of cyclophosphamide and dexamethasone.

Results

Subject white blood cell count was 143.43 × 109/L, and 56% prolymphocytes. He did not show lymphadenopathy but splenomegaly. Immunophenotyping of prolymphocytes was CD5(+low), CD10(−), CD11c(−), CD19(+), CD20(+), cCD22(+), CD23(−), cCD79a(+), CD79b(+), FMC7(±), CD43(−), CD3(−), CD56(−), CD103(−), HLA-DR(+), and Lambda(+). R-banding and FISH revealed that leukemia cells carried extra chromosome 5. Considering the rare occurrence of trisomy 5 found in prolymphocytic leukemia, especially in Asians, with rapid disease progression. We know that median survival of B-PLL is three years after diagnosis, while survival time of this patient was only 1 month.

Conclusion

This study could provide the firsthand materials for precision, medicine and mechanism research in cytogenetics and molecular biology. It inferred that trisomy 5 might be a poor prognosis indicator, providing directions for clinical practice in the foreseeable future.

Normal and Neoplastic Growth Suppression by the Extended Myc Network

Among the first discovered and most prominent cellular oncogenes is MYC, which encodes a bHLH-ZIP transcription factor (Myc) that both activates and suppresses numerous genes involved in proliferation, energy production, metabolism and translation. Myc belongs to a small group of bHLH-ZIP transcriptional regulators (the Myc Network) that includes its obligate heterodimerization partner Max and six "Mxd proteins" (Mxd1-4, Mnt and Mga), each of which heterodimerizes with Max and largely opposes Myc's functions. More recently, a second group of bHLH-ZIP proteins (the Mlx Network) has emerged that bears many parallels with the Myc Network. It is comprised of the Myc-like factors ChREBP and MondoA, which, in association with the Max-like member Mlx, regulate smaller and more functionally restricted repertoires of target genes, some of which are shared with Myc. Opposing ChREBP and MondoA are heterodimers comprised of Mlx and Mxd1, Mxd4 and Mnt, which also structurally and operationally link the two Networks. We discuss here the functions of these "Extended Myc Network" members, with particular emphasis on their roles in suppressing normal and neoplastic growth. These roles are complex due to the temporal- and tissue-restricted expression of Extended Myc Network proteins in normal cells, their regulation of both common and unique target genes and, in some cases, their functional redundancy.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

TRIB3 promotes MYC-associated lymphoma development through suppression of UBE3B-mediated MYC degradation

The transcription factor MYC is deregulated in almost all human cancers, especially in aggressive lymphomas, through chromosomal translocation, amplification, and transcription hyperactivation. Here, we report that high expression of tribbles homologue 3 (TRIB3) positively correlates with elevated MYC expression in lymphoma specimens; TRIB3 deletion attenuates the initiation and progression of MYC-driven lymphoma by reducing MYC expression. Mechanistically, TRIB3 interacts with MYC to suppress E3 ubiquitin ligase UBE3B-mediated MYC ubiquitination and degradation, which enhances MYC transcriptional activity, causing high proliferation and self-renewal of lymphoma cells. Use of a peptide to disturb the TRIB3-MYC interaction together with doxorubicin reduces the tumor burden in Myc^Eμ mice and patient-derived xenografts. The pathophysiological relevance of UBE3B, TRIB3 and MYC is further demonstrated in human lymphoma. Our study highlights a key mechanism for controlling MYC expression and a potential therapeutic option for treating lymphomas with high TRIB3-MYC expression.

c-MYC is often deregulated in human cancers including lymphomas. Here, the authors show that a member of the pseudokinase family, tribbles homologue 3 (TRIB3), interacts with c-MYC to suppress c-MYC ubiquitination and degradation, leading to increased proliferation and self-renewal of lymphoma cells.

MYC in Germinal Center-derived lymphomas: Mechanisms and therapeutic opportunities

The rearrangement of immunoglobulin loci during the germinal center reaction is associated with an increased risk of chromosomal translocations that activate oncogenes such as MYC, BCL2 or BCL6, thus contributing to the development of B-cell lymphomas. MYC and BCL2 activation are initiating events in Burkitt's (BL) and Follicular Lymphoma (FL), respectively, but can occur at later stages in other subtypes such as Diffuse Large-B Cell Lymphoma (DLBCL). MYC can also be activated during the progression of FL to the transformed stage. Thus, either DLBCL or FL can give rise to aggressive double-hit lymphomas (DHL) with concurrent activation of MYC and BCL2. Research over the last three decades has improved our understanding of the functions of these oncogenes and the basis for their cooperative action in lymphomagenesis. MYC, in particular, is a transcription factor that contributes to cell activation, growth and proliferation, while concomitantly sensitizing cells to apoptosis, the latter being blocked by BCL2. Here, we review our current knowledge about the role of MYC in germinal center B-cells and lymphomas, discuss MYC-induced dependencies that can sensitize cancer cells to select pharmacological inhibitors, and illustrate their therapeutic potential in aggressive lymphomas-and in particular in DHL, in combination with BCL2 inhibitors.

Molecular Genetics in the Diagnosis and Biology of Lymphoid Neoplasms

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of molecular genetics in the diagnosis and biology of lymphoid neoplasms.

METHODS

The Workshop Panel reviewed 82 cases.

RESULTS

Molecular genetic testing reveals alterations that expand the spectrum of diseases such as DUSP22 rearrangement in ALK-negative anaplastic large cell lymphoma, large B-cell lymphoma with IRF4 rearrangement, MYD88 mutations in B-cell lymphomas, Burkitt-like lymphoma with 11q aberrations, and diagnostic criteria for high-grade B-cell lymphomas. Therapeutic agents and natural tumor progression may be associated with transcriptional reprogramming that lead to transdifferentiation and lineage switch.

CONCLUSIONS

Application of emerging technical advances has revealed the complexity of genetic events in lymphomagenesis, progression, and acquired resistance to therapies. They also contribute to enhanced understanding of the biology of indolent vs aggressive behavior, clonal evolution, tumor progression, and transcriptional reprogramming associated with transdifferentiation events that may occur subsequent to therapy.

[The role of translocations involving c-MYC/8q24, BCL2/18q21 and/or BCL6/3q27 genes in patients with follicular lymphoma. Retrospective analysis of single - centre data]

Aim of the issue was to compare clinical characteristics and treatment results of patients with follicular lymphoma (FL) with translocations involving loci of c-MYC/8q24, BCL2/18q21 and/or BCL6/3q27 genes and patients with high - grade B-cell lymphoma [High - grade B-cell lymphoma (HGBL), double - hit (DH)]. Materials and methods. Since 2004 to 2017 years in National Research Center for Hematology 12 patients with high - grade B-cell lymphoma double - hit (HGBL DH) and 6 FL patients with translocations involving c-MYC and BCL2 and/or BCL6 had been treated. We performed a comparative analysis of clinical characterisctics in both groups. As primary endpoints was assessed frequency of complete remission (CR) or progressive disease (PD); as secondary endpoints - overall (OS) and event - free survival (EFS). Results. 5 patients with HGBL DH had c-MYC/BCL6, 7 - c-MYC/BCL2 rearrangements; 2 patients with FL had c-MYC/BCL2, 3 - c-MYC/BCL6, 1 - c-MYC/BCL2/BCL6 rearrangements. FL was represented by grade 3A in 2, grade 3B - in 4 cases, 3 of them had large - cell transformation. In HGBL DH and FL patients had no significant differences in clinical characteristics. The majority of patients had a widespread tumour, increased LDH activity, high frequency of extranodal and bone marrow involvement. Ki-67 expression level was lower in patients with FL (p.

The HDAC6-selective inhibitor is effective against non-Hodgkin lymphoma and synergizes with ibrutinib in follicular lymphoma

Follicular lymphoma (FL) is the most common indolent B-cell non-Hodgkin lymphoma (NHL) with genetic alterations of BCL-2, KMT2B, and KMT6. FL is refractory to conventional chemotherapy and is still incurable in most patients. Thus, new drugs and/or novel combination treatment strategies are needed to further improve FL patient outcome. We investigated the efficacy of the histone deacetylase 6 (HDAC6) inhibitor A452 combined with a Bruton's tyrosine kinase (BTK) inhibitor ibrutinib on NHL and the underlying mechanisms compared with the current clinically tested HDAC6 inhibitor ACY-1215. We first showed that FL is the most sensitive to HDAC6 inhibitor. We showed that combining A452 with ibrutinib led to the synergistic inhibition of cell growth and decreased viability of FL cells, as well as increased levels of apoptosis. Similar synergistic interactions occur in chronic lymphocytic leukemia (CLL) and germinal center diffuse large B-cell lymphoma cells (DLBCL). Enhanced cell death is associated with AKT and ERK1/2 inactivation and increased DNA damage (induction of γH2A.X and reduction of pChk1/2). In addition, A452 downregulates c-Myc, an effect significantly enhanced by ibruninib. Although ACY-1215 is less potent than A452, it displays synergism with ibrutinib. Overall, our results suggest that A452 is more effective as an anticancer agent than ACY-1215 in FL. These findings suggest that a combination of HDAC6-selective inhibitor and ibrutinib is a potent therapeutic strategy for NHL including FL.

Increased MYC copy number is an independent prognostic factor in patients with diffuse large B-cell lymphoma

Patients with double-hit or triple-hit lymphoma have a significantly worse prognosis compared to patients with diffuse large B-cell lymphoma without MYC rearrangement. However, the prognostic importance of extra copies of MYC, BCL2, or BCL6 has not been fully explored. We studied 663 patients with de novo diffuse large B-cell lymphoma in whom the status of MYC/8q24, BCL2/18q21, and BCL6/3q27 were assessed by fluorescence in situ hybridization. Cases of double or triple extra copy lymphoma were defined by the presence of increased MYC copies and increased BCL2 and/or BCL6 copies or rearrangement. In total, 76 patients with diffuse large B-cell lymphoma had MYC extra copies including 43 cases of double or triple extra copy lymphoma; 105 patients had diffuse large B-cell lymphoma with MYC-R including 56 double- or triple-hit lymphoma; and 482 diffuse large B-cell lymphoma patients had no MYC abnormality (MYC normal). Patients with MYC extra copies, similar to MYC-R, had a worse overall survival compared with MYC normal patients (both P<0.01). The prognosis between patients with MYC extra copies and MYC-R was not statistically significantly different (P=0.086). Cell-of-origin classification failed to correlate with survival in the MYC extra copies group, similar to the MYC-R patient group. Compared with patients with double- or triple-hit lymphoma, patients with double or triple extra copy lymphoma had a higher complete remission rate (P=0.02), but there was no significant statistical difference in overall survival (P=0.089). Intensive induction chemotherapy regimens improved the overall survival of patients with double or triple extra copy lymphoma, but there was no significant improvement of overall survival in patients with MYC-R tumors. Multivariate analysis showed that MYC extra copy in diffuse large B-cell lymphoma is an independent poor prognostic factor, similar to MYC rearrangement.

Clinical utility of recently identified diagnostic, prognostic, and predictive molecular biomarkers in mature B-cell neoplasms

Genomic profiling studies have provided new insights into the pathogenesis of mature B-cell neoplasms and have identified markers with prognostic impact. Recurrent mutations in tumor-suppressor genes (TP53, BIRC3, ATM), and common signaling pathways, such as the B-cell receptor (CD79A, CD79B, CARD11, TCF3, ID3), Toll-like receptor (MYD88), NOTCH (NOTCH1/2), nuclear factor-κB, and mitogen activated kinase signaling, have been identified in B-cell neoplasms. Chronic lymphocytic leukemia/small lymphocytic lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, Burkitt lymphoma, Waldenström macroglobulinemia, hairy cell leukemia, and marginal zone lymphomas of splenic, nodal, and extranodal types represent examples of B-cell neoplasms in which novel molecular biomarkers have been discovered in recent years. In addition, ongoing retrospective correlative and prospective outcome studies have resulted in an enhanced understanding of the clinical utility of novel biomarkers. This progress is reflected in the 2016 update of the World Health Organization classification of lymphoid neoplasms, which lists as many as 41 mature B-cell neoplasms (including provisional categories). Consequently, molecular genetic studies are increasingly being applied for the clinical workup of many of these neoplasms. In this review, we focus on the diagnostic, prognostic, and/or therapeutic utility of molecular biomarkers in mature B-cell neoplasms.

The Role of c-MYC in B-Cell Lymphomas: Diagnostic and Molecular Aspects

c-MYC is one of the most essential transcriptional factors, regulating a diverse array of cellular functions, including proliferation, growth, and apoptosis. Dysregulation of c-MYC is essential in the pathogenesis of a number of B-cell lymphomas, but is rarely reported in T-cell lymphomas. c-MYC dysregulation induces lymphomagenesis by loss of the tight control of c-MYC expression, leading to overexpression of intact c-MYC protein, in contrast to the somatic mutations or fusion proteins seen in many other oncogenes. Dysregulation of c-MYC in B-cell lymphomas occurs either as a primary event in Burkitt lymphoma, or secondarily in aggressive lymphomas such as diffuse large B-cell lymphoma, plasmablastic lymphoma, mantle cell lymphoma, or double-hit lymphoma. Secondary c-MYC changes include gene translocation and gene amplification, occurring against a background of complex karyotype, and most often confer aggressive clinical behavior, as evidenced in the double-hit lymphomas. In low-grade B-cell lymphomas, acquisition of c-MYC rearrangement usually results in transformation into highly aggressive lymphomas, with some exceptions. In this review, we discuss the role that c-MYC plays in the pathogenesis of B-cell lymphomas, the molecular alterations that lead to c-MYC dysregulation, and their effect on prognosis and diagnosis in specific types of B-cell lymphoma.

Myc enhances B-cell receptor signaling in precancerous B cells and confers resistance to Btk inhibition

Dysregulation of the oncogenic transcription factor MYC induces B cell transformation and is a driver for B cell non-Hodgkin lymphoma (B-NHL). MYC overexpression in B-NHL is associated with more aggressive phenotypes and poor prognosis. Although genomic studies suggest a link between MYC overexpression and B cell receptor (BCR) signaling molecules in B-NHL, signaling pathways essential to Myc-mediated B-cell transformation have not been fully elucidated. We utilized intracellular phospho-flow cytometry to investigate the relationship between Myc and BCR signaling in pre-malignant B cells. Utilizing the Eμ-myc mouse model, where Myc is overexpressed specifically in B cells, both basal and stimulated BCR signaling were increased in precancerous B lymphocytes from Eμ-myc mice compared to wild-type littermates. B cells overexpressing Myc displayed constitutively higher levels of activated CD79α, Btk, Plcγ2, and Erk1/2. Notably, Myc overexpressing B cells maintained elevated BCR signaling despite treatment with ibrutinib, a Bruton’s tyrosine kinase inhibitor. Furthermore, PI3K/Akt pathway signaling was also increased in Eμ-myc B cells, and this increase was partially suppressed with ibrutinib. Additionally, experiments with Btk-null B cells revealed off-target effects of ibrutinib on BCR signaling. Our data show that in pre-malignant B cells, Myc overexpression is sufficient to activate BCR and PI3K/Akt signaling pathways and further enhances signaling following BCR ligation. Therefore, our results indicate precancerous B cells have already acquired enhanced survival and growth capabilities prior to transformation, and that elevated MYC levels confer resistance to pharmacologic inhibitors of BCR signaling, which has significant implications for B-NHL treatment.

MYC rearranged B-cell neoplasms: Impact of genetics on classification

A cohort comprising 156 patients with B-cell neoplasms harboring an MYC rearrangement was analyzed with respect to phenotypic presentation, molecular markers (TP53, MYC and ID3) and additional cytogenetic abnormalities (concomitantly occurring BCL2, BCL6 and/or CCND1 rearrangements; double, triple or quadruple hit lymphomas = multiple hit lymphomas). MYC translocations occurred as single hit (only MYC rearranged, 63%) or multiple hit lymphoma (37%) and presented as acute leukemia (AL) (14%), Burkitt lymphoma (30%), chronic lymphocytic leukemia (CLL) (21%) or other mature B-cell neoplasms (35%). Multiple hit lymphomas more frequently showed a complex karyotype compared to single hit lymphomas (62% vs. 28%, p < 0.001). Single hit Burkitt lymphomas presented with specific characteristics, by translocation of MYC to an immunoglobulin locus, predominantly a non-complex karyotype (23% vs. 67%, p = 0.012) and a significantly higher ID3 and TP53 mutation frequency (ID3mut: 49% vs. 0%, p = 0.002; TP53mut: 69% vs. 33%, p = 0.045). Additionally, MYC rearranged CLL presented as outstanding group by often showing a non-complex karyotype (85%), absence of ID3 mutations, a high frequency of SF3B1 mutations, and a frequent involvement of non-immunoglobulin loci as MYC-partner genes (61%). Consequently, genetic characteristics distinguish different subgroups of MYC rearranged B-cell neoplasms and therefore may contribute to a new classification system.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

The morphology of CLL revisited: the clinical significance of prolymphocytes and correlations with prognostic/molecular markers in the LRF CLL4 trial

Historically, an increase in the percentage and number of circulating prolymphocytes in chronic lymphocytic leukaemia (CLL) has been associated with strong expression of surface immunoglobulin, trisomy 12 and a poor outcome. This study re‐examines the biological and clinical significance of increased peripheral blood prolymphocytes in 508 patients at entry into the randomized UK Leukaemia Research Fund CLL4 trial. It also investigates the associations between increased prolymphocytes and a comprehensive array of biomarkers. 270 patients (53%) had <5% prolymphocytes, 167 (33%) had 5–9%, 60 (12%) had 10–14% and 11 (2%) had ≥15% prolymphocytes. We show that a higher proportion of prolymphocytes (≥10%) was independently associated with NOTCH1 mutations (P = 0·006), absence of 13q deletion (P = 0·001), high CD38 expression (P = 0·02) and unmutated IGHV genes (P = 0·01). Deaths due to Richter syndrome were significantly more common amongst patients who had ≥10% vs <10% prolymphocytes (13% vs 2%) respectively (P < 0·0001). ≥10% prolymphocytes was also associated with a shorter progression‐free survival (Hazard ratio [HR] 1·50 [95% confidence interval [CI]: 1·16–1·93], P = 0·002) and overall survival (HR 1·99 [95% CI: 1·53–2·59], P < 0·0001). Our data support the routine examination of blood films in CLL and suggest that a finding of an increased proportion of prolymphocytes may be a trigger for further evaluation of clinical and laboratory features of progressive disease.

Immunoglobulin gene translocations in chronic lymphocytic leukemia: A report of 35 patients and review of the literature

Chronic lymphocytic leukemia (CLL) represents the most common hematological malignancy in Western countries, with a highly heterogeneous clinical course and prognosis. Translocations involving the immunoglobulin (IG) genes are regularly identified. From 2000 to 2014, we identified an IG gene translocation in 18 of the 396 patients investigated at diagnosis (4.6%) and in 17 of the 275 analyzed during follow-up (6.2%). A total of 4 patients in whom the IG translocation was identified at follow-up did not carry the translocation at diagnosis. The IG heavy locus (IGH) was involved in 27 translocations (77.1%), the IG κ locus (IGK) in 1 (2.9%) and the IG λ locus (IGL) in 7 (20.0%). The chromosome band partners of the IG translocations were 18q21 in 16 cases (45.7%), 11q13 and 19q13 in 4 cases each (11.4% each), 8q24 in 3 cases (8.6%), 7q21 in 2 cases (5.7%), whereas 6 other bands were involved once (2.9% each). At present, 35 partner chromosomal bands have been described, but the partner gene has solely been identified in 10 translocations. CLL associated with IG gene translocations is characterized by atypical cell morphology, including plasmacytoid characteristics, and the propensity of being enriched in prolymphocytes. The IG heavy chain variable region (IGHV) mutational status varies between translocations, those with unmutated IGHV presumably involving cells at an earlier stage of B-cell lineage. All the partner genes thus far identified are involved in the control of cell proliferation and/or apoptosis. The translocated partner gene becomes transcriptionally deregulated as a consequence of its transposition into the IG locus. With the exception of t(14;18)(q32;q21) and its variants, prognosis appears to be poor for the other translocations. Therefore, searching for translocations involving not only IGH, but also IGL and IGK, by banding and molecular cytogenetics is required. Furthermore, it is important to identify the partner gene to ensure the patients receive the optimal treatment.

The clinical significance of 8q24/MYC rearrangement in chronic lymphocytic leukemia

Chromosome 8q24/MYC rearrangement is associated with Burkitt lymphoma and some aggressive B-cell lymphomas, but is rare in chronic lymphocytic leukemia. We here report a cohort of 20 chronic lymphocytic leukemia patients with 8q24/MYC rearrangement, 3 detected at time of initial diagnosis and 17 acquired after a median interval of 48 months. At the time when 8q24/MYC arrangement was detected, 18 patients had B-symptoms, 17 had lymphadenopathy, and 17 had splenomegaly. Histologically, typical chronic lymphocytic leukemia morphology was seen in six patients, increased prolymphocytes in nine and Richter's transformation in five patients. Eighteen patients had karyotypic information available that showed t(8;v) in a complex karyotype in 12 patients and in a non-complex karyotype in 6 patients. Fluorescence in situ hybridization confirmed MYC rearrangement in 17/17 patients. All patients required therapy after 8q24/MYC rearrangement was detected. At last follow-up, five of six patients with a non-complex karyotype were alive after a median of 74 months (10~143 months) from the detection of 8q24/MYC rearrangement. In contrast, 10 of 12 patients with a complex karyotype died with a median survival of 5.5 months. We conclude that 8q24/MYC rearrangement in chronic lymphocytic leukemia is rare and often acquired during the course of disease. If it is presented in a complex karyotype, it is often associated with Richter's transformation, refractory to therapy and an aggressive clinical course; on the other hand, if it is present in a non-complex karyotype, patients often respond to risk-adapted therapies and achieve remission.

Advances in the molecular functions of syndecan-1 (SDC1/CD138) in the pathogenesis of malignancies

Syndecan-1 (SDC1, synd, CD138) is the most widely studied member of four structurally related cell surface heparan sulfate proteoglycans (HSPG). Although SDC1 has been implicated in a wide range of biological functions, its altered expression often produces malignant phenotypes, which arise from increased cell proliferation and cell growth, cell survival, cell invasion and metastasis, and angiogenesis. Recent studies revealed much about the underlying molecular roles of SDC1 in these processes. The changes in SDC1 expression also have a direct impact on the clinical course of cancers, as evident by its prognostic significance. Accumulating evidence suggest that SDC1 is involved in stimulation of cancer stem cells (CSC) or tumor initiating cells (TIC) and this may affect disease relapse, and resistance to therapy. This review discusses the progress on the pro-tumorigenic role(s) of SDC1 and how these roles may impact the clinical aspect of the disease. Also discussed, are the current strategies for targeting SDC1 or its related signaling.

Aberrations of MYC are a common event in B-cell prolymphocytic leukemia

OBJECTIVES

B-cell prolymphocytic leukemia (B-PLL) remains a controversial entity, and its molecular pathogenesis is largely unknown. Patients are older, typically having marked lymphocytosis and splenomegaly in the absence of lymphadenopathy. It is defined as a mature B-cell leukemia with more than 55% circulating prolymphocytes. Leukemic mantle cell lymphoma and chronic lymphocytic leukemia in prolymphocytic transformation must be excluded.

METHODS

Case archives were retrospectively reviewed for B-PLL in patients without a previous diagnosis of chronic lymphocytic leukemia or other B-cell neoplasm.

RESULTS

We identified six cases of B-PLL with available cytogenetic data, five of which showed evidence of aberrations in MYC. Three cases showed additional signals for the MYC gene by fluorescence in situ hybridization (FISH), and two cases demonstrated t(8;14)MYC/IGH by karyotyping or FISH. High levels of MYC protein expression were detected in all cases tested with MYC aberrations.

CONCLUSIONS

These results suggest that deregulation of MYC plays an important role in the pathogenesis of B-PLL and expands the spectrum of B-cell neoplasms associated with aberrations of MYC.

High p27 protein levels in chronic lymphocytic leukemia are associated to low Myc and Skp2 expression, confer resistance to apoptosis and antagonize Myc effects on cell cycle

Myc (c-Myc) counteracts p27 effects, and low p27 usually correlates with high Myc expression in human cancer. However there is no information on the co-expression of both genes in chronic lymphocytic leukemia (CLL). We found a lack of correlation between RNA and protein levels of p27 and Myc in CLL cells, so we determined the protein levels by immunoblot in 107 cases of CLL. We observed a high p27 protein expression in CLL compared to normal B cells. Ectopic p27 expression in a CLL-derived cell line resulted in cell death resistance. Surprisingly, Myc expression was very low or undetectable in most CLL cases analyzed, with a clear correlation between high p27 and low Myc protein levels. This was associated with low Skp2 expression, which is consistent with the Skp2 role in p27 degradation and with SKP2 being a Myc target gene. High Myc expression did not correlate with leukemia progression, despite that cell cycle-related Myc target genes were upregulated. However, biochemical analysis showed that the high p27 levels inhibited cyclin-Cdk complexes even in Myc expressing CLL cells. Our data suggest that the combination of high p27 and low Myc is a marker of CLL cells which is mediated by Skp2.

Genetic abnormalities in chronic lymphocytic leukemia: where we are and where we go

Chromosomal abnormalities in chronic lymphocytic leukemia (CLL) are detected in up to 80% of patients. Among them, deletions of 11q, 13q, 17p, and trisomy 12 have a known prognostic value and play an important role in CLL pathogenesis and evolution, determining patients outcome and therapeutic strategies. Standard methods used to identify these genomic aberrations include both conventional G-banding cytogenetics (CGC) and fluorescence in situ hybridization (FISH). Although FISH analyses have been implemented as the gold standard, CGC allows the identification of chromosomal translocations and complex karyotypes, the latest associated with poor outcome. Genomic arrays have a higher resolution that allows the detection of cryptic abnormalities, although these have not been fully implemented in routine laboratories. In the last years, next generation sequencing (NGS) methods have identified a wide range of gene mutations (e.g., TP53, NOTCH1, SF3B1, and BIRC3) which have improved our knowledge about CLL development, allowing us to refine both the prognostic subgroups and better therapeutic strategies. Clonal evolution has also recently arisen as a key point in CLL, integrating cytogenetic alterations and mutations in a dynamic model that improve our understanding about its clinical course and relapse.

Atypical rearrangement involving 3'-IGH@ and a breakpoint at least 400 Kb upstream of an intact MYC in a CLL patient with an apparently balanced t(8;14)(q24.1;q32) and negative MYC expression

The t(8;14)(q24.1;q32), the cytogenetic hallmark of Burkitt's lymphoma, is also found, but rarely, in cases of chronic lymphocytic leukemia (CLL). Such translocation typically results in a MYC-IGH@ fusion subsequently deregulating and overexpressing MYC on der 14q32. In CLL, atypical rearrangements resulting in its gain or loss, within or outside of IGH@ or MYC locus, have been reported, but their clinical significance remains uncertain. Herein, we report a 67 year-old male with complex cytogenetic findings of apparently balanced t(8;14) and unreported complex rearrangements of IGH@ and MYC loci. His clinical, morphological and immunophenotypic features were consistent with the diagnosis of CLL.Interphase FISH studies revealed deletions of 11q22.3 and 13q14.3, and an extra copy of IGH@, indicative of rearrangement. Karyotype analysis showed an apparently balanced t(8;14)(q24.1;q32). Sequential GPG-metaphase FISH studies revealed abnormal signal patterns: rearrangement of IGH break apart probe with the 5'-IGH@ on derivative 8q24.1 and the 3'-IGH@ retained on der 14q; absence of MYC break apart-specific signal on der 8q; and, the presence of unsplit 5'-MYC-3' break apart probe signals on der 14q. The breakpoint on 8q24.1 was found to be at least 400 Kb upstream of 5' of MYC. In addition, FISH studies revealed two abnormal clones; one with 13q14.3 deletion, and the other, with concurrent 11q deletion and atypical rearrangements. Chromosome microarray analysis (CMA) detected a 7.1 Mb deletion on 11q22.3-q23.3 including ATM, a finding consistent with FISH results. While no significant copy number gain or loss observed on chromosomes 8, 12 and 13, a 455 Kb microdeletion of uncertain clinical significance was detected on 14q32.33. Immunohistochemistry showed co-expression of CD19, CD5, and CD23, positive ZAP-70 expression and absence of MYC expression. Overall findings reveal an apparently balanced t(8;14) and atypical complex rearrangements involving 3'-IGH@ and a breakpoint at least 400 Kb upstream of MYC, resulting in the relocation of the intact 5'-MYC-3' from der 8q, and apposition to 3'-IGH@ at der 14q. This case report provides unique and additional cytogenetic data that may be of clinical significance in such a rare finding in CLL. It also highlights the utility of conventional and sequential metaphase FISH in understanding complex chromosome anomalies and their association with other clinical findings in patients with CLL. To the best of our knowledge, this is the first CLL reported case with such an atypical rearrangement in a patient with a negative MYC expression.

High-resolution genomic profiling of chronic lymphocytic leukemia reveals new recurrent genomic alterations

To identify genomic alterations in chronic lymphocytic leukemia (CLL), we performed single-nucleotide polymorphism–array analysis using Affymetrix Version 6.0 on 353 samples from untreated patients entered in the CLL8 treatment trial. Based on paired-sample analysis (n = 144), a mean of 1.8 copy number alterations per patient were identified; approximately 60% of patients carried no copy number alterations other than those detected by fluorescence in situ hybridization analysis. Copy-neutral loss-of-heterozygosity was detected in 6% of CLL patients and was found most frequently on 13q, 17p, and 11q. Minimally deleted regions were refined on 13q14 (deleted in 61% of patients) to the DLEU1 and DLEU2 genes, on 11q22.3 (27% of patients) to ATM, on 2p16.1-2p15 (gained in 7% of patients) to a 1.9-Mb fragment containing 9 genes, and on 8q24.21 (5% of patients) to a segment 486 kb proximal to the MYC locus. 13q deletions exhibited proximal and distal breakpoint cluster regions. Among the most common novel lesions were deletions at 15q15.1 (4% of patients), with the smallest deletion (70.48 kb) found in the MGA locus. Sequence analysis of MGA in 59 samples revealed a truncating mutation in one CLL patient lacking a 15q deletion. MNT at 17p13.3, which in addition to MGA and MYC encodes for the network of MAX-interacting proteins, was also deleted recurrently.

Chronic lymphocytic leukemia and prolymphocytic leukemia with MYC translocations: a subgroup with an aggressive disease course

Translocations involving MYC are rare in chronic lymphocytic leukemia (CLL), and up to now, their prognostic significance remains unclear. We report the characteristics of 21 patients with CLL and nine patients with prolymphocytic leukemia (PLL), diagnosed in multiple centers (n = 13), which showed an MYC translocation demonstrated by fluorescence in situ hybridization. The prevalence was estimated to be <1%. Advanced age and male predominance were observed. Morphological analysis frequently revealed the presence of prolymphocytes. A typical "CLL-immunophenotype" was found in four of nine cases with PLL. Moreover, CD5 and CD23 were frequently expressed in PLL. The latter findings are atypical for PLL and may suggest transformation or progression of an underlying CLL. MYC translocations were frequently observed with concomitant adverse cytogenetic markers, such as del(11q) (n = 8/30) and/or del(17p)/monosomy 17 (n = 7/30). In addition, the presence of unbalanced translocations (n = 24 in 13/30 cases) and complex karyotype (n = 16/30) were frequent in cases with MYC translocations. Altogether, del(17p)/monosomy 17, del(11q), and/or complex karyotype were observed in 22 of 30 patients. Survival outcome was poor: the median time to treatment was only 5 months, and overall survival (OS) from clinical diagnosis and from genetic detection was 71 and 19 months, respectively. In conclusion, CLL/PLL with MYC translocations is a rare entity, which seems to be associated with adverse prognostic features and unfavorable outcome.

Myc roles in hematopoiesis and leukemia

Hematopoiesis is a process capable of generating millions of cells every second, as distributed in many cell types. The process is regulated by a number of transcription factors that regulate the differentiation along the distinct lineages and dictate the genetic program that defines each mature phenotype. Myc was first discovered as the oncogene of avian leukemogenic retroviruses; it was later found translocated in human lymphoma. From then on, evidence accumulated showing that c-Myc is one of the transcription factors playing a major role in hematopoiesis. The study of genetically modified mice with overexpression or deletion of Myc has shown that c-Myc is required for the correct balance between self-renewal and differentiation of hematopoietic stem cells (HSCs). Enforced Myc expression in mice leads to reduced HSC pools owing to loss of self-renewal activity at the expense of increased proliferation of progenitor cells and differentiation. c-Myc deficiency consistently results in the accumulation of HSCs. Other models with conditional Myc deletion have demonstrated that different lineages of hematopoietic cells differ in their requirement for c-Myc to regulate their proliferation and differentiation. When transgenic mice overexpress c-Myc or N-Myc in mature cells from the lymphoid or myeloid lineages, the result is lymphoma or leukemia. In agreement, enforced expression of c-Myc blocks the differentiation in several leukemia-derived cell lines capable of differentiating in culture. Not surprising, MYC deregulation is recurrently found in many types of human lymphoma and leukemia. Whereas MYC is deregulated by translocation in Burkitt lymphoma and, less frequently, other types of lymphoma, MYC is frequently overexpressed in acute lymphoblastic and myeloid leukemia, through mechanisms unrelated to chromosomal translocation, and is often associated with disease progression.

Analysis of the chronic lymphocytic leukemia coding genome: role of NOTCH1 mutational activation

Next generation sequencing and copy number analysis provide insights into the complexity of the CLL coding genome, and reveal an association between NOTCH1 mutational activation and poor prognosis.

The pathogenesis of chronic lymphocytic leukemia (CLL), the most common leukemia in adults, is still largely unknown. The full spectrum of genetic lesions that are present in the CLL genome, and therefore the number and identity of dysregulated cellular pathways, have not been identified. By combining next-generation sequencing and copy number analysis, we show here that the typical CLL coding genome contains <20 clonally represented gene alterations/case, including predominantly nonsilent mutations, and fewer copy number aberrations. These analyses led to the discovery of several genes not previously known to be altered in CLL. Although most of these genes were affected at low frequency in an expanded CLL screening cohort, mutational activation of NOTCH1, observed in 8.3% of CLL at diagnosis, was detected at significantly higher frequency during disease progression toward Richter transformation (31.0%), as well as in chemorefractory CLL (20.8%). Consistent with the association of NOTCH1 mutations with clinically aggressive forms of the disease, NOTCH1 activation at CLL diagnosis emerged as an independent predictor of poor survival. These results provide initial data on the complexity of the CLL coding genome and identify a dysregulated pathway of diagnostic and therapeutic relevance.

Diagnostic issues in chronic lymphocytic leukaemia (CLL)

The diagnosis of chronic lymphocytic leukaemia (CLL) is based on clinical and laboratory features. Morphology and immunophenotype are the initial diagnostic investigations. In atypical cases, these tests should be complemented with molecular genetics and/or histology to exclude other B-cell disorders of small lymphocytes. Morphologically, CLL can be classified into typical and atypical. Immunophenotyping is the only method that can establish or confirm the diagnosis as CLL lymphocytes have a distinct immunophenotypic signature. A scoring system compounding the results with a set of markers allows firming up the diagnosis. Other immunological markers such as CD38 and ZAP-70 have an important prognostic impact. Fluorescence in situ hybridization (FISH) analysis, chiefly by detecting 17p (TP53 locus) and 11q (ATM) deletions and mutational status of the IgVH gene, also provides prognostic information and may determine the type of therapy. In atypical CLL, histology and/or molecular genetics may be required to exclude other B-cell disorders.

B-cell activating factor and v-Myc myelocytomatosis viral oncogene homolog (c-Myc) influence progression of chronic lymphocytic leukemia

Mice bearing a v-Myc myelocytomatosis viral oncogene homolog (c-Myc) transgene controlled by an Ig-alpha heavy-chain enhancer (iMyc(Cα) mice) rarely develop lymphomas but instead have increased rates of memory B-cell turnover and impaired antibody responses to antigen. We found that male progeny of iMyc(Cα) mice mated with mice transgenic (Tg) for CD257 (B-cell activating factor, BAFF) developed CD5(+) B-cell leukemia resembling human chronic lymphocytic leukemia (CLL), which also displays a male gender bias. Surprisingly, leukemic cells of Myc/Baff Tg mice expressed higher levels of c-Myc than did B cells of iMyc(Cα) mice. We found that CLL cells of many patients with progressive disease also expressed high amounts of c-MYC, particularly CLL cells whose survival depends on nurse-like cells (NLC), which express high-levels of BAFF. We find that BAFF could enhance CLL-cell expression of c-MYC via activation the canonical IκB kinase (IKK)/NF-κB pathway. Inhibition of the IKK/NF-κB pathway in mouse or human leukemia cells blocked the capacity of BAFF to induce c-MYC or promote leukemia-cell survival and significantly impaired disease progression in Myc/Baff Tg mice. This study reveals an important relationship between BAFF and c-MYC in CLL which may affect disease development and progression, and suggests that inhibitors of the canonical NF-κB pathway may be effective in treatment of patients with this disease.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.

Inflammation and survival pathways: chronic lymphocytic leukemia as a model system

A primary response to inflammation is an increased survival of the target cell. Several pathways have been identified that promote maintenance of the cell. The principal mechanism for the extended survival is through induction of anti-apoptotic Bcl-2 family proteins. Bcl-2 was the founding member of this family with five additional members, Bcl-X(L), Bcl-W, Bcl-B, Bfl-1, and Mcl-1, discovered mostly in hematological malignancies. Another mechanism that could add to cell survival is the Pim kinase pathway. This family of enzymes is associated with Myc-driven transcription, cell cycle regulation, degradation of pro-apoptotic proteins, and protein translation. Chronic lymphocytic leukemia serves as an optimal model to understand the mechanism by which these two protein families provide survival advantage to cells. In addition, since this malignancy is known to be maintained by microenvironment milieu, this further adds advantage to investigate mechanisms by which these pro-survival proteins are induced in the presence of stromal support. Multiple mechanisms exists that result in increase in transcript and protein level of anti-apoptotic Bcl-2 family members. Following these inductions, post-translational modifications occur resulting in increased stability of pro-survival proteins, while Pim-mediated phosphorylation inhibits pro-apoptotic protein activity. Furthermore, there is a cross-talk between these two (Bcl-2 family proteins and Pim family proteins) pathways that co-operate with each other for CLL cell survival and maintenance. Vigorous efforts are being made to create small molecules that affect these proteins directly or indirectly. Several of these pharmacological inhibitors are in early clinical trials for patients with hematological malignancies.

Determination of genes and microRNAs involved in the resistance to fludarabine in vivo in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) cells are often affected by genomic aberrations targeting key regulatory genes. Although fludarabine is the standard first line therapy to treat CLL, only few data are available about the resistance of B cells to this purine nucleoside analog in vivo. Here we sought to increase our understanding of fludarabine action and describe the mechanisms leading to resistance in vivo. We performed an analysis of genomic aberrations, gene expression profiles, and microRNAs expression in CLL blood B lymphocytes isolated during the course of patients' treatment with fludarabine.

RESULTS

In sensitive patients, the differentially expressed genes we identified were mainly involved in p53 signaling, DNA damage response, cell cycle and cell death. In resistant patients, uncommon genomic abnormalities were observed and the resistance toward fludarabine could be characterized based on the expression profiles of genes implicated in lymphocyte proliferation, DNA repair, and cell growth and survival. Of particular interest in some patients was the amplification of MYC (8q) observed both at the gene and transcript levels, together with alterations of myc-transcriptional targets, including genes and miRNAs involved in the regulation of cell cycle and proliferation. Differential expression of the sulfatase SULF2 and of miR-29a, -181a, and -221 was also observed between resistant and sensitive patients before treatment. These observations were further confirmed on a validation cohort of CLL patients treated with fludarabine in vitro.

CONCLUSION

In the present study we identified genes and miRNAs that may predict clinical resistance of CLL to fludarabine, and describe an interesting oncogenic mechanism in CLL patients resistant to fludarabine by which the complete MYC-specific regulatory network was altered (DNA and RNA levels, and transcriptional targets). These results should prove useful for understanding and overcoming refractoriness to fludarabine and also for predicting the clinical outcome of CLL patients before or early during their treatment.

Deletion 15q as the sole abnormality in acute myeloid leukemia: report of three cases and review of the literature

Deletions within the long arm of chromosome 15, a recurrent abnormality in myeloid malignancies, have been reported previously as a sole abnormality in only eight cases of acute myeloid leukemia (AML). We describe three new cases of AML with this abnormality, all adult women (age, 41-66 years). Two cases were acute myelomonocytic leukemia (FAB AML-M4), and one was acute myeloblastic leukemia with maturation (FAB AML-M2). The deletion was identified at initial diagnosis in one patient and at relapse in the other two. Although all received aggressive therapy, their survival was short. Taken together with the eight previously reported cases, we conclude that deletions in chromosome 15 are associated with AML, both in cases that arise de novo or in the setting of a myeloproliferative disorder or myelodysplastic syndrome. These cases often show features of myelomonocytic or monocytic differentiation. The prognosis is poor, with survival similar to other AML cases with unfavorable cytogenetic changes.