Sofie Peirs

ABT-199 mediated inhibition of BCL-2 as a novel therapeutic strategy in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a high-risk subtype of acute lymphoblastic leukemia (ALL) with gradually improved survival through introduction of intensified chemotherapy. However, therapy-resistant or refractory T-ALL remains a major clinical challenge. Here, we evaluated B-cell lymphoma (BCL)-2 inhibition by the BH3 mimetic ABT-199 as a new therapeutic strategy in human T-ALL. The T-ALL cell line LOUCY, which shows a transcriptional program related to immature T-ALL, exhibited high in vitro and in vivo sensitivity for ABT-199 in correspondence with high levels of BCL-2. In addition, ABT-199 showed synergistic therapeutic effects with different chemotherapeutic agents including doxorubicin, l-asparaginase, and dexamethasone. Furthermore, in vitro analysis of primary patient samples indicated that some immature, TLX3- or HOXA-positive primary T-ALLs are highly sensitive to BCL-2 inhibition, whereas TAL1 driven tumors mostly showed poor ABT-199 responses. Because BCL-2 shows high expression in early T-cell precursors and gradually decreases during normal T-cell differentiation, differences in ABT-199 sensitivity could partially be mediated by distinct stages of differentiation arrest between different molecular genetic subtypes of human T-ALL. In conclusion, our study highlights BCL-2 as an attractive molecular target in specific subtypes of human T-ALL that could be exploited by ABT-199.

Novel biological insights in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive type of blood cancer that accounts for about 15% of pediatric and 25% of adult acute lymphoblastic leukemia (ALL) cases. It is considered as a paradigm for the multistep nature of cancer initiation and progression. Genetic and epigenetic reprogramming events, which transform T-cell precursors into malignant T-ALL lymphoblasts, have been extensively characterized over the past decade. Despite our comprehensive understanding of the genomic landscape of human T-ALL, leukemia patients are still treated by high-dose multiagent chemotherapy, potentially followed by hematopoietic stem cell transplantation. Even with such aggressive treatment regimens, which are often associated with considerable acute and long-term side effects, about 15% of pediatric and 40% of adult T-ALL patients still relapse, owing to acquired therapy resistance, and present with very dismal survival perspectives. Unfortunately, the molecular mechanisms by which residual T-ALL tumor cells survive chemotherapy and act as a reservoir for leukemic progression and hematologic relapse remain poorly understood. Nevertheless, it is expected that enhanced molecular understanding of T-ALL disease biology will ultimately facilitate a targeted therapy driven approach that can reduce chemotherapy-associated toxicities and improve survival of refractory T-ALL patients through personalized salvage therapy. In this review, we summarize recent biological insights into the molecular pathogenesis of T-ALL and speculate how the genetic landscape of T-ALL could trigger the development of novel therapeutic strategies for the treatment of human T-ALL.

ZEB2 drives immature T-cell lymphoblastic leukaemia development via enhanced tumour-initiating potential and IL-7 receptor signalling

Early T-cell precursor leukaemia (ETP-ALL) is a high-risk subtype of human leukaemia that is poorly understood at the molecular level. Here we report translocations targeting the zinc finger E-box-binding transcription factor ZEB2 as a recurrent genetic lesion in immature/ETP-ALL. Using a conditional gain-of-function mouse model, we demonstrate that sustained Zeb2 expression initiates T-cell leukaemia. Moreover, Zeb2-driven mouse leukaemia exhibit some features of the human immature/ETP-ALL gene expression signature, as well as an enhanced leukaemia-initiation potential and activated Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signalling through transcriptional activation of IL7R. This study reveals ZEB2 as an oncogene in the biology of immature/ETP-ALL and paves the way towards pre-clinical studies of novel compounds for the treatment of this aggressive subtype of human T-ALL using our Zeb2-driven mouse model.

Epigenetics in T‐cell acute lymphoblastic leukemia

Normal T‐cell development is a strictly regulated process in which hematopoietic progenitor cells migrate from the bone marrow to the thymus and differentiate from early T‐cell progenitors toward mature and functional T cells. During this maturation process, cooperation between a variety of oncogenes and tumor suppressors can drive immature thymocytes into uncontrolled clonal expansion and cause T‐cell acute lymphoblastic leukemia (T‐ALL). Despite improved insights in T‐ALL disease biology and comprehensive characterization of its genetic landscape, clinical care remained largely similar over the past decades and still consists of high‐dose multi‐agent chemotherapy potentially followed by hematopoietic stem cell transplantation. Even with such aggressive treatment regimens, which are often associated with considerable side effects, clinical outcome is still extremely poor in a significant subset of T‐ALL patients as a result of therapy resistance or hematological relapses. Recent genetic studies have identified recurrent somatic alterations in genes involved in DNA methylation and post‐translational histone modifications in T‐ALL, suggesting that epigenetic homeostasis is critically required in restraining tumor development in the T‐cell lineage. In this review, we provide an overview of the epigenetic regulators that could be implicated in T‐ALL disease biology and speculate how the epigenetic landscape of T‐ALL could trigger the development of epigenetic‐based therapies to further improve the treatment of human T‐ALL.

Targeting BET proteins improves the therapeutic efficacy of BCL-2 inhibition in T-cell acute lymphoblastic leukemia.

Inhibition of anti-apoptotic BCL-2 (B-cell lymphoma 2) has recently emerged as a promising new therapeutic strategy for the treatment of a variety of human cancers, including leukemia. Here, we used T-cell acute lymphoblastic leukemia (T-ALL) as a model system to identify novel synergistic drug combinations with the BH3 mimetic venetoclax (ABT-199). In vitro drug screening in primary leukemia specimens that were derived from patients with high risk of relapse or relapse and cell lines revealed synergistic activity between venetoclax and the BET (bromodomain and extraterminal) bromodomain inhibitor JQ1. Notably, this drug synergism was confirmed in vivo using T-ALL cell line and patient-derived xenograft models. Moreover, the therapeutic benefit of this drug combination might, at least in part, be mediated by an acute induction of the pro-apoptotic factor BCL2L11 and concomitant reduction of BCL-2 upon BET bromodomain inhibition, ultimately resulting in an enhanced binding of BIM (encoded by BCL2L11) to BCL-2. Altogether, our work provides a rationale to develop a new type of targeted combination therapy for selected subgroups of high-risk leukemia patients.

Oncogenic ZEB2 activation drives sensitivity toward KDM1A inhibition in T-cell acute lymphoblastic leukemia

Elevated expression of the Zinc finger E-box binding homeobox transcription factor-2 (ZEB2) is correlated with poor prognosis and patient outcome in a variety of human cancer subtypes. Using a conditional gain-of-function mouse model, we recently demonstrated that ZEB2 is an oncogenic driver of immature T-cell acute lymphoblastic leukemia (T-ALL), a heterogenic subgroup of human leukemia characterized by a high incidence of remission failure or hematological relapse after conventional chemotherapy. Here, we identified the lysine-specific demethylase KDM1A as a novel interaction partner of ZEB2 and demonstrated that mouse and human T-ALLs with increased ZEB2 levels critically depend on KDM1A activity for survival. Therefore, targeting the ZEB2 protein complex through direct disruption of the ZEB2-KDM1A interaction or pharmacological inhibition of the KDM1A demethylase activity itself could serve as a novel therapeutic strategy for this aggressive subtype of human leukemia and possibly other ZEB2-driven malignancies.

A quantitative proteomics approach identifies ETV6 and IKZF1 as new regulators of an ERG-driven transcriptional network

Aberrant stem cell-like gene regulatory networks are a feature of leukaemogenesis. The ETS-related gene (ERG), an important regulator of normal haematopoiesis, is also highly expressed in T-ALL and acute myeloid leukaemia (AML). However, the transcriptional regulation of ERG in leukaemic cells remains poorly understood. In order to discover transcriptional regulators of ERG, we employed a quantitative mass spectrometry-based method to identify factors binding the 321 bp ERG +85 stem cell enhancer region in MOLT-4 T-ALL and KG-1 AML cells. Using this approach, we identified a number of known binders of the +85 enhancer in leukaemic cells along with previously unknown binders, including ETV6 and IKZF1. We confirmed that ETV6 and IKZF1 were also bound at the +85 enhancer in both leukaemic cells and in healthy human CD34+ haematopoietic stem and progenitor cells. Knockdown experiments confirmed that ETV6 and IKZF1 are transcriptional regulators not just of ERG, but also of a number of genes regulated by a densely interconnected network of seven transcription factors. At last, we show that ETV6 and IKZF1 expression levels are positively correlated with expression of a number of heptad genes in AML and high expression of all nine genes confers poorer overall prognosis.

A novel L-asparaginase with low L-glutaminase coactivity is highly efficacious against both T and B cell acute lymphoblastic leukemias in vivo

Acute lymphoblastic leukemia (ALL) is the most common type of pediatric cancer, although about 4 of every 10 cases occur in adults. The enzyme drug l-asparaginase serves as a cornerstone of ALL therapy and exploits the asparagine dependency of ALL cells. In addition to hydrolyzing the amino acid l-asparagine, all FDA-approved l-asparaginases also have significant l-glutaminase coactivity. Since several reports suggest that l-glutamine depletion correlates with many of the side effects of these drugs, enzyme variants with reduced l-glutaminase coactivity might be clinically beneficial if their antileukemic activity would be preserved. Here we show that novel low l-glutaminase variants developed on the backbone of the FDA-approved Erwinia chrysanthemi l-asparaginase were highly efficacious against both T- and B-cell ALL, while displaying reduced acute toxicity features. These results support the development of a new generation of safer l-asparaginases without l-glutaminase activity for the treatment of human ALL.Significance: A new l-asparaginase-based therapy is less toxic compared with FDA-approved high l-glutaminase enzymes Cancer Res; 78(6); 1549-60. ©2018 AACR.

Genetic characterization and therapeutic targeting of MYC‐rearranged T cell acute lymphoblastic leukaemia

Author(s): Milani, Gloria; Matthijssens, Filip; Van Loocke, Wouter; Durinck, Kaat; Roels, Juliette; Peirs, Sofie; Thenoz, Morgan; Pieters, Tim; Reunes, Lindy; Lintermans, Beatrice; Vandamme, Niels; Lammens, Tim; Van Roy, Nadine; Van Nieuwerburgh, Filip; Deforce, Dieter; Schwab, Claire; Raimondi, Susana; Dalla Pozza, Luciano; Carroll, Andrew J; De Moerloose, Barbara; Benoit, Yves; Goossens, Steven; Berx, Geert; Harrison, Christine J; Basso, Giuseppe; Cave, Helene; Sutton, Rosemary; Asnafi, Vahid; Meijerink, Jules; Mullighan, Charles; Loh, Mignon; Van Vlierberghe, Pieter

Preclinical evaluation of second generation PIM inhibitors for the treatment of T-cell acute lymphoblastic leukemia and lymphoma

T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) are aggressive hematologic malignancies that are currently still treated by highdose chemotherapy possibly followed by hematopoietic stem cell transplantation. Despite important progress in deciphering the genomic landscape of these diseases, the transition of novel targeted therapies towards clinical practice has remained largely unsuccessful. T-ALL and TLBL, which the World Health Organization regards as one single disease entity, can be classified into different molecular genetic subtypes based on the aberrant expression of specific transcription factor oncogenes, such as LYL1, TLX1, TLX3, HOXA, NKX2-1, TAL1 or LMO2. Within these genetic subclasses, a variety of co-operative lesions converge towards activation of specific pathways, such as JAK-STAT or PI3K-AKT signaling. Interestingly, JAK-STAT pathway mutations seem to be more prevalent in LYL1, TLX1, TLX3 and HOXA tumors, whereas mature TAL1 leukemias/lymphomas more often display PI3K/AKT alterations. PIM1 is a highly conserved serine/threonine kinase involved in cell-cycle progression, transcription, apoptosis, drug resistance and cellular metabolism through phosphorylation of a myriad of known downstream targets. Formal proof of its oncogenic activity emerged from the analysis of Pim1 transgenic mice, which spontaneously developed T-cell lymphomas with a latency of several months. At the transcriptional level, PIM1 is a canonical JAK-STAT target gene that can be activated downstream of cytokine signaling. Recently, a number of studies have all shown that PIM1 might act as an attractive molecular target in human T-ALL. Indeed, recent work identified a case of adult T-ALL in which aberrant activation of PIM1 was driven by the T-cell receptor (TCR) translocation t(6;7)(p21;q34) (TCRβ-PIM1). In addition, PIM1 activation was also found to be more broadly implicated in T-ALL disease biology downstream of mutational activation of the JAK-STAT signaling pathway. Although these studies clearly point towards PIM1 as a novel therapeutic target for the treatment of T-ALL, initial drug evaluation experiments have largely been focused on human T-ALL and T-LBL cell lines, which often fail to provide an accurate representation of the primary disease. Therefore, additional in-depth pre-clinical in vivo evaluation of PIM inhibitors using patient-derived xenograft models of human T-ALL and T-LBL will be required to further facilitate the translation of these findings into clinical practice in the near future. Here, we report the identification of a similar TCRβPIM1 translocation, t(6;7)(p21;q34), as previously described, in a case of pediatric T-LBL, suggesting that these PIM1 rearrangements are a rare but recurrent genetic abnormality in both pediatric and adult T-ALL and T-LBL. For this particular T-LBL case (see the Online Supplementary Methods for clinical information), initial FISH analysis revealed the presence of a TCRβ translocation in the major leukemic clone at diagnosis. Using Targeted Locus Amplification (TLA), with the TCRβ