Presence of three recurrent chromosomal reaarrangements, t(2;3)(p12;q37), del(8)(q24), and t(14;18), in an acute lymphoblastic leukemia

Histone H3K27 demethylase KDM6A is an epigenetic gatekeeper of mTORC1 signalling in cancer

OBJECTIVE

Large-scale genome sequencing efforts of human tumours identified epigenetic modifiers as one of the most frequently mutated gene class in human cancer. However, how these mutations drive tumour development and tumour progression are largely unknown. Here, we investigated the function of the histone demethylase KDM6A in gastrointestinal cancers, such as liver cancer and pancreatic cancer.

DESIGN

Genetic alterations as well as expression analyses of KDM6A were performed in patients with liver cancer. Genetic mouse models of liver and pancreatic cancer coupled with Kdm6a-deficiency were investigated, transcriptomic and epigenetic profiling was performed, and in vivo and in vitro drug treatments were conducted.

RESULTS

KDM6A expression was lost in 30% of patients with liver cancer. Kdm6a deletion significantly accelerated tumour development in murine liver and pancreatic cancer models. Kdm6a-deficient tumours showed hyperactivation of mTORC1 signalling, whereas endogenous Kdm6a re-expression by inducible RNA-interference in established Kdm6a-deficient tumours diminished mTORC1 activity resulting in attenuated tumour progression. Genome-wide transcriptional and epigenetic profiling revealed direct binding of Kdm6a to crucial negative regulators of mTORC1, such as Deptor, and subsequent transcriptional activation by epigenetic remodelling. Moreover, in vitro and in vivo genetic epistasis experiments illustrated a crucial function of Deptor and mTORC1 in Kdm6a-dependent tumour suppression. Importantly, KDM6A expression in human tumours correlates with mTORC1 activity and KDM6A-deficient tumours exhibit increased sensitivity to mTORC1 inhibition.

CONCLUSION

KDM6A is an important tumour suppressor in gastrointestinal cancers and acts as an epigenetic toggle for mTORC1 signalling. Patients with KDM6A-deficient tumours could benefit of targeted therapy focusing on mTORC1 inhibition.

Co-Operativity between MYC and BCL-2 Pro-Survival Proteins in Cancer

B-Cell Lymphoma 2 (BCL-2), c-MYC and related proteins are arguably amongst the most widely studied in all of biology. Every year there are thousands of papers reporting on different aspects of their biochemistry, cellular and physiological mechanisms and functions. This plethora of literature can be attributed to both proteins playing essential roles in the normal functioning of a cell, and by extension a whole organism, but also due to their central role in disease, most notably, cancer. Many cancers arise due to genetic lesions resulting in deregulation of both proteins, and indeed the development and survival of tumours is often dependent on co-operativity between these protein families. In this review we will discuss the individual roles of both proteins in cancer, describe cancers where co-operativity between them has been well-characterised and finally, some strategies to target these proteins therapeutically.

Circular RNA PVT1 expression and its roles in acute lymphoblastic leukemia

AIM

The roles of circular RNA PVT1 (circPVT1) are explored in the patients with acute lymphoblastic leukemia (ALL).

METHODS

The circPVT1 level was detected by qRT-PCR and western blot. The apoptotic cells were examined by the annexin V assay in lentiviral shRNA knockdown cells.

RESULTS

circPVT1 was highly expressed in ALL compared with normal bone marrow samples. circPVT1 expression was also significantly higher in ALL cell lines. circPVT1 knockdown inhibited cell proliferation and induced cell apoptosis through suppression of its neighbor gene c-Myc, and antiapoptotic Bcl-2 protein expression.

CONCLUSION

circPVT1 is upregulated in ALL. Silencing circPVT1 results in cell growth arrest and apoptosis of the cells. Our results also suggested a therapeutic potential of targeting circPVT1 in ALL.

De novo acute lymphoblastic leukemia-like disease of high grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements: a case report and literature review

Background

B-cell lymphomas harboring the 8q24/MYC plus 18q21/BCL2 translocations are now referred to as high grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements (HGBL-MBR). Although HGBL-MBR is frequently found in cases with diffuse large B-cell lymphoma or Burkitt lymphoma-like B-cell lymphoma, acute lymphoblastic leukemia (ALL)-like disease of HGBL-MBR (AL-HGBL-MBR) has been reported incidentally.

Case presentation

A 69-year-old Japanese woman developed remittent fever and increasing systemic bone pain. The bone marrow examination revealed that more than 90% of nuclear cells were blastoid cells, which were positive for CD10, CD19, CD20, and surface IgMκ and negative for terminal deoxynucleotidyl transferase (TdT). Cytogenetic studies confirmed that the patient had de novo AL-HGBL-MBR with the extra copies of MYC and loss of chromosome 17p. She showed resistance to chemoimmunotherapy and died seven months after the diagnosis. The literature review identified further 47 de novo AL-HGBL-MBR cases within the last 32 years. The median age was 61 years (range, 27 − 86); the male/female ratio was 2.0. Thirty-eight cases (79%) presented a clinical picture of ALL at diagnosis; 14 (36%) of 39 available cases showed central nervous system involvement. Loss of 17p and translocations at 2p12–13, 3q27, 9p13 were frequently observed as additional cytogenetic abnormalities. Although the median survival of 46 available cases was only five months (range, 0.1–18), rituximab use significantly improved the survival of AL-HGBL-MBR (log-rank test, P = 0.0294).

Conclusion

Our patient and most reported de novo AL-HGBL-MBR cases showed resistance to conventional chemoimmunotherapy and disastrous consequences. AL-HGBL-MBL is a rare, but should be considered a distinct clinical condition in HGBL-MBR. Other therapeutic strategies, such as using inhibitors of MYC and BCL2, are needed to overcome the chemoresistance of AL-HGBL-MBR.

MYC and the control of apoptosis

MYC expression is tightly correlated with cell-cycle progression in normal tissues, whereas unchecked MYC expression is among the most prominent hallmarks of the hyperproliferation associated with most forms of cancer. At first glance it might seem counterintuitive that MYC is also among the most robust agents of programmed cell death (apoptosis) in mammalian cells. However it is clearly beneficial for a multicellular organism to have a mechanism for triggering death in cells that express potentially oncogenic levels of MYC. Decades of intense study have begun to provide an understanding of the mechanisms that regulate MYC's seemingly split personality. Key features of MYC-induced apoptosis will be discussed here along with examples of how our understanding of this pathway might be exploited for the therapeutic benefit of cancer patients.

Immunoglobulin light chain gene translocations in non-Hodgkin's lymphoma as assessed by fluorescence in situ hybridisation

In non-Hodgkin's lymphoma (NHL), the majority of translocations involve the immunoglobulin heavy chain gene (IGH) locus, while a few involve the immunoglobulin light chain gene (IGL) locus, consisting of the kappa light chain gene (IGkappa) and the lambda light chain gene (IGlambda). Although many reports have dealt with the translocation and/or amplification of IGH in NHL, only a few have identified IGL translocations. To identify cytogenetic abnormalities and the partner chromosomes of IGL translocations in NHL, we performed dual-colour fluorescence in situ hybridisation (DC-FISH) and spectral karyotyping (SKY) in seven NHL cell lines and 40 patients with NHL. We detected IGL translocations in two cell lines and nine patients: four patients with diffuse large B-cell lymphoma, three with follicular lymphoma, one with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue and one with mantle cell lymphoma. Five distinct partners of IGlambda translocation were identified by SKY analysis: 3q27 in three patients, and 1p13, 6p25, 17p11.2 and 17q21 in one patient each. Three cases featured double translocations of IGH and IGL. These findings warrant the identification of novel genes 1p13, 6p25, 17p11.2 and 17q21.

Transformed follicular lymphoma with concurrent t(2;3), t(8;14) and t(14;18)

An elderly Chinese man who had an 8-year history of follicular lymphoma presented with large B-cell lymphoma. The disease ran a rapidly fatal course with a terminal leukemic phase. Cytogenetic analysis of the transformed follicular lymphoma showed a complex karyotype of 48,Y,t(X;19)(q26;p13.3),t(2;3)(p12;q27),t(8;14)(q24.1;q32),+12,t(14;18)(q32;q21),+21. To my knowledge, this is the first reported case of simultaneous occurrence of t(2;3), t(8;14), and t(14;18) in transformed follicular lymphoma.

Translocation (14;18)(q32;q21) in acute lymphoblastic leukemia: a study of 12 cases and review of the literature

We present a series of 12 cases of de novo acute lymphoblastic leukemia (ALL) with translocation t(14;18)(q32;q21). The median age of patients at presentation was 65.5 years, and no patient presented with a past history or any clinical evidence of lymphoma. A Burkitt translocation was identified in 4 of the 12 cases by conventional cytogenetics but fluorescence in situ hybridization using a MYC probe identified a further three cases of MYC rearrangement: one with a cryptic t(8;14) involving the der(14)t(14;18), one showing MYC translocated onto a marker chromosome, and one associated with a t(8;9)(q24;p13) translocation. A review of the literature identified an extremely close association between the t(14;18) and the t(8;9), with the latter translocation found only in the presence of t(14;18). The present study confirms the previously reported dismal prognosis of t(14;18)-associated ALL.

BCL2 is a downstream effector of MIZ-1 essential for blocking c-MYC-induced apoptosis

The c-MYC oncoprotein is among the most potent transforming agents in human cells. Ironically, c-MYC is also capable of inducing massive apoptosis under certain conditions. A clear understanding of the distinct pathways activated by c-MYC during apoptosis induction and transformation is crucial to the design of therapeutic strategies aimed at selectively reactivating the apoptotic potential of c-MYC in cancer cells. We recently demonstrated that apoptosis induction in primary human cells strictly requires that c-MYC bind and inactivate the transcription factor MIZ-1. This presumably blocked the ability of MIZ-1 to activate the transcription of an unidentified pro-survival gene. Here we report that MIZ-1 activates the transcription of BCL2. More importantly, inhibition of the MIZ-1/BCL2 signal is an essential event during the apoptotic response. Furthermore, targeting BCL2 with short hairpin RNA or small molecule inhibitors restores the apoptotic potential of a c-MYC mutant that is defective for MIZ-1 inhibition. These observations suggest that repression of BCL2 transcription is the single essential consequence of targeting the MIZ-1 pathway during apoptosis induction. These data define a genetic pathway that helps to explain historical observations documenting cooperation between c-MYC and BCL2 overexpression in human cancer.

Concurrent translocation of BCL2 and MYC with a single immunoglobulin locus in high-grade B-cell lymphomas

B-cell leukaemia or lymphoma with a combination of t(8;14)(q24;q32) of Burkitt leukaemia/lymphoma and t(14;18)(q32;q21) of follicular lymphoma may present clinically as de novo acute lymphoblastic leukaemia or transformation of follicular lymphoma to aggressive histology diffuse lymphoma. A number of cell lines have been reported with a complex t(8;14;18) with fusion of MYC, IGH and BCL2 on the same derivative 8 chromosome. The objective of this study was to determine the frequency and chromosomal features of this der(8)t(8;14;18) in a series of acute leukaemias and malignant lymphomas. A database of 1350 leukaemia and lymphoma karyotypes was searched for cases with structural alterations affecting both 8q24 and 18q21. A total of 55 cases were identified, of which eight revealed a complex der(8)t(8;14;18) with an MYC-IGH-BCL2 rearrangement resulting from translocation of BCL2 and MYC with a single disrupted IGH allele. Molecular cytogenetic investigation is essential to identify cases of high-grade leukaemia/lymphoma with concurrent translocations affecting the BCL2 and MYC loci.

Presence of somatic hypermutation and activation-induced cytidine deaminase in acute lymphoblastic leukemia L2 with t(14;18)(q32;q21)

AIM

Acute lymphoblastic leukemia (ALL) with L2 (FAB) morphology has rarely been reported to show t(14;18)(q32;q21). We aimed to delineate the stage at which this type of ALL is derived in B-lineage differentiation.

METHODS

The somatic hypermutation (SHM) of the variable region of immunoglobulin heavy chain (IgV(H)) gene and the expression of terminal deoxynucleotidyl transferase (TdT), recombination-activating gene 1 and 2 (RAG-1 and -2), and activation-induced cytidine deaminase (AID) were investigated in three cell lines and two fresh samples, including a pair of matched fresh and cell line cells.

RESULTS

TdT, RAG-1, and RAG-2 were variably expressed. AID was expressed in four of five samples. SHM of the IgV(H) gene was found in all samples with high average frequency (11.84%) comparable with that in follicular lymphoma. Ongoing mutation was seen in two fresh samples.

CONCLUSION

As AID and SHM are generally regarded as properties exhibited by mature B cells, the presence of AID and SHM in this study seems to be incompatible with the general understanding of the early stage derivation of ALL in B-lineage differentiation. The results here give some insight into the relationship between disease type (ALL or lymphoma) and derivation stage, the overlapping of the early stage phenotype and the mature genomic characteristics, and the probable relationship between the mechanism of the occurrence of t(14;18)(q32;q21) and the machinery causing SHM.

Mature B-cell acute lymphoblastic leukemia with associated translocations (14;18)(q32;q21) and (8;9)(q24;p13). A Burkitt variant?

The translocation t(14;18)(q32;q21) is most commonly associated with follicular lymphoma but has also been described in acute lymphoblastic leukemia (ALL) of B-cell origin. Although these ALL cases have had a pre-pre-B, pre-B, or mature B-cell immunophenotype and L2 or L3 morphology, all have been associated with an abnormality of 8q24. In fact, 91% (10 of 11) have been associated with t(8;22) or t(8;14), marker chromosomes for Burkitt-type ALL. The other case was associated with del(8)(q24). Thus, Burkitt-type ALL may have various immunophenotypes and morphology when associated with t(14;18). We describe a case of mature B-cell ALL associated with t(14;18) and t(8;9)(q24;p13). The morphology was suggestive but not entirely characteristic of the L3 subtype. However, on the basis of the cytogenetic findings and the review of the literature, perhaps this case represents a variant of Burkitt-type ALL, which would be important to recognize for prognostic and therapeutic purposes. We describe our findings and review the literature to heighten awareness of this group of ALLs associated with t(14;18). Additional cases need to be accrued and documented to determine the significance of an associated abnormality of 8q24 in this setting.

De novo acute B cell leukemia/lymphoma with t(14;18)

The t(14;18)(q32;q21) translocation is the most common translocation in B cell malignancies being found in 80% of follicular lymphomas and about 20% of diffuse large B cell lymphomas. Only rare cases of de novo acute B cell lymphoblastic leukemia with t(14;18) have been described. We describe five cases of this entity which appears to have very homogeneous clinical, phenotypic and genotypic features. None of these patients had prior history of follicular lymphoma. The disease was characterized by acute clinical features with nodal and/or extranodal disease, massive bone marrow infiltration and rapid increase of circulating blast cells of mature B cell phenotype. All patients disclosed complex chromosomal and molecular abnormalities involving at least the BCL-2 and c-MYC genes. Furthermore, three patients had evidence of BCL-6 involvement and one patient had a p53 mutation. Despite intensive chemotherapy, including for two patients allogeneic bone marrow transplantation in first complete remission, all patients died within a few months. Neuro-meningeal relapse occurred in three of the five patients in spite of neuro-meningeal prophylaxis. De novo leukemia/lymphoma with t(14;18) is a rare entity with a very poor prognosis. Whether early bone marrow transplant could modify the natural history of the disease remains to be determined. An intensive neuro-meningeal prophylaxis appears to be mandatory in these patients.