Koorosh Korfi

Dual targeting of p53 and c-MYC selectively eliminates leukaemic stem cells.

Summary Chronic myeloid leukaemia (CML) arises following transformation of a haemopoietic stem cell (HSC) by protein-tyrosine kinase BCR-ABL1. Direct inhibition of BCR-ABL1 kinase has revolutionized disease management, but fails to eradicate leukaemic stem cells (LSC), which maintain CML. LSC are independent of BCR-ABL1 for survival, providing a rationale to identify and target kinase-independent pathways. Here we show using proteomics, transcriptomics and network analyses, that in human LSC aberrantly expressed proteins, in both imatinib-responder and non-responder patients are modulated in concert with p53 and c-Myc regulation. Perturbation of both p53 and c-Myc, not BCR-ABL1 itself, leads to synergistic kill, differentiation and near elimination of transplantable human LSC in mice, whilst sparing normal HSC. This unbiased systems approach targeting connected nodes exemplifies a novel precision medicine strategy providing evidence that LSC can be eradicated.

Epigenetic Reprogramming Sensitizes CML Stem Cells to Combined EZH2 and Tyrosine Kinase Inhibition

A major obstacle to curing chronic myeloid leukemia (CML) is residual disease maintained by tyrosine kinase inhibitor (TKI)-persistent leukemic stem cells (LSC). These are BCR-ABL1 kinase independent, refractory to apoptosis, and serve as a reservoir to drive relapse or TKI resistance. We demonstrate that Polycomb Repressive Complex 2 is misregulated in chronic phase CML LSCs. This is associated with extensive reprogramming of H3K27me3 targets in LSCs, thus sensitizing them to apoptosis upon treatment with an EZH2-specific inhibitor (EZH2i). EZH2i does not impair normal hematopoietic stem cell survival. Strikingly, treatment of primary CML cells with either EZH2i or TKI alone caused significant upregulation of H3K27me3 targets, and combined treatment further potentiated these effects and resulted in significant loss of LSCs compared to TKI alone, in vitro, and in long-term bone marrow murine xenografts. Our findings point to a promising epigenetic-based therapeutic strategy to more effectively target LSCs in patients with CML receiving TKIs. SIGNIFICANCE In CML, TKI-persistent LSCs remain an obstacle to cure, and approaches to eradicate them remain a significant unmet clinical need. We demonstrate that EZH2 and H3K27me3 reprogramming is important for LSC survival, but renders LSCs sensitive to the combined effects of EZH2i and TKI. This represents a novel approach to more effectively target LSCs in patients receiving TKI treatment. Cancer Discov; 6(11); 1248-57. ©2016 AACR.See related article by Xie et al., p. 1237This article is highlighted in the In This Issue feature, p. 1197.

BIM mediates synergistic killing of B-cell acute lymphoblastic leukemia cells by BCL-2 and MEK inhibitors.

B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive hematological disease that kills ~50% of adult patients. With the exception of some BCR-ABL1+ patients who benefit from tyrosine kinase inhibitors, there are no effective targeted therapies for adult B-ALL patients and chemotherapy remains first-line therapy despite adverse side effects and poor efficacy. We show that, although the MEK/ERK pathway is activated in B-ALL cells driven by different oncogenes, MEK inhibition does not suppress B-ALL cell growth. However, MEK inhibition synergized with BCL-2/BCL-XL family inhibitors to suppress proliferation and induce apoptosis in B-ALL cells. We show that this synergism is mediated by the pro-apoptotic factor BIM, which is dephosphorylated as a result of MEK inhibition, allowing it to bind to and neutralize MCL-1, thereby enhancing BCL-2/BCL-XL inhibitor-induced cell death. This cooperative effect is observed in B-ALL cells driven by a range of genetic abnormalities and therefore has significant therapeutic potential.

CML cells actively evade host immune surveillance through cytokine-mediated downregulation of MHC-II expression.

Targeting the fusion oncoprotein BCR-ABL with tyrosine kinase inhibitors has significantly affected chronic myeloid leukemia (CML) treatment, transforming the life expectancy of patients; however the risk for relapse remains, due to persistence of leukemic stem cells (LSCs). Therefore it is imperative to explore the mechanisms that result in LSC survival and develop new therapeutic approaches. We now show that major histocompatibility complex (MHC)-II and its master regulator class II transactivator (CIITA) are downregulated in CML compared with non-CML stem/progenitor cells in a BCR-ABL kinase-independent manner. Interferon γ (IFN-γ) stimulation resulted in an upregulation of CIITA and MHC-II in CML stem/progenitor cells; however, the extent of IFN-γ-induced MHC-II upregulation was significantly lower than when compared with non-CML CD34+ cells. Interestingly, the expression levels of CIITA and MHC-II significantly increased when CML stem/progenitor cells were treated with the JAK1/2 inhibitor ruxolitinib (RUX). Moreover, mixed lymphocyte reactions revealed that exposure of CD34+ CML cells to IFN-γ or RUX significantly enhanced proliferation of the responder CD4+CD69+ T cells. Taken together, these data suggest that cytokine-driven JAK-mediated signals, provided by CML cells and/or the microenvironment, antagonize MHC-II expression, highlighting the potential for developing novel immunomodulatory-based therapies to enable host-mediated immunity to assist in the detection and eradication of CML stem/progenitor cells.

A personalised medicine approach for ponatinib-resistant chronic myeloid leukaemia

BACKGROUND Chronic myeloid leukaemia (CML) is characterised by the presence of a fusion driver oncogene, BCR-ABL1, which is a constitutive tyrosine kinase. Tyrosine kinase inhibitors (TKIs) are the central treatment strategy for CML patients and have significantly improved survival rates, but the T315I mutation in the kinase domain of BCR-ABL1 confers resistance to all clinically approved TKIs, except ponatinib. However, compound mutations can mediate resistance even to ponatinib and remain a clinical challenge in CML therapy. Here, we investigated a ponatinib-resistant CML patient through whole-genome sequencing (WGS) to identify the cause of resistance and to find alternative therapeutic targets. PATIENTS AND METHODS We carried out WGS on a ponatinib-resistant CML patient and demonstrated an effective combination therapy against the primary CML cells derived from this patient in vitro. RESULTS Our findings demonstrate the emergence of compound mutations in the BCR-ABL1 kinase domain following ponatinib treatment, and chromosomal structural variation data predicted amplification of BCL2. The primary CD34+ CML cells from this patient showed increased sensitivity to the combination of ponatinib and ABT-263, a BCL2 inhibitor with a negligible effect against the normal CD34+ cells. CONCLUSION Our results show the potential of personalised medicine approaches in TKI-resistant CML patients and provide a strategy that could improve clinical outcomes for these patients.We used personalised medicine approaches for the first time in a tyrosine kinase inhibitor-resistant chronic myeloid leukaemia (CML) patient. Our whole genome sequencing data revealed the emergence of compound mutations in the BCR-ABL1 kinase domain and BCL2 amplification. Patients CML cells showed increased sensitivity to the ponatinib/ABT-263 combination in vitro.

Follicular Lymphoma, a B cell malignancy addicted to epigenetic mutations.

ABSTRACT While follicular lymphoma (FL) is exquisitely responsive to immuno-chemotherapy, many patients follow a relapsing remitting clinical course driven in part by a common precursor cell (CPC) population. Advances in next generation sequencing have provided valuable insights into the genetic landscape of FL and its clonal evolution in response to therapy, implicating perturbations of epigenetic regulators as a hallmark of the disease. Recurrent mutations of histone modifiers KMT2D, CREBBP, EP300, EZH2, ARIDIA, and linker histones are likely early events arising in the CPC pool, rendering epigenetic based therapies conceptually attractive for treatment of indolent and transformed FL. This review provides a synopsis of the main epigenetic aberrations and the current efforts in development and testing of epigenetic therapies in this B cell malignancy.

Genomic profiling reveals spatial intra-tumor heterogeneity in follicular lymphoma.

We are indebted to the patients for donating tumor specimens as part of this study. The authors thank the Centre de Ressources Biologiques (CRB)-Sante of Rennes (BB-0033-00056) for patient samples, Queen Mary University of London Genome Centre for Illumina Miseq sequencing, and the support by the National Institute for Health Research (NIHR) Biomedical Research Centre at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London for Illumina Hiseq sequencing. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health. This work was supported by grants from the Kay Kendall Leukaemia Fund (KKL 757 awarded to J.O.), Cancer Research UK (22742 awarded to J.O., 15968 awarded to J.F., Clinical Research Fellowship awarded to S.A.), Bloodwise through funding of the Precision Medicine for Aggressive Lymphoma (PMAL) consortium, Centre for Genomic Health, Queen Mary University of London, Carte d’Identite des Tumeurs (CIT), Ligue National contre le Cancer, Pole de biologie hospital universitaire de Rennes, CRB-Sante of Rennes (BB-0033-00056), and CeVi/Carnot program.

Advances in the molecular diagnosis of diffuse large B-cell lymphoma in the era of precision medicine

ABSTRACT Introduction: The adoption of high-throughput technologies has led to a transformation in our ability to classify diffuse large B-cell lymphoma (DLBCL) into unique molecular subtypes. In parallel, the expansion of agents targeting key genetic and gene expression signatures has led to an unprecedented opportunity to personalize cancer therapies, paving the way for precision medicine. Areas covered: This review summarizes the key molecular subtypes of DLBCL and outlines the novel technology platforms in development to discriminate clinically relevant subtypes. Expert commentary: The application of emerging diagnostic tests into routine clinical practise is gaining momentum following the demonstration of subtype specific activity by novel agents. Co-ordinated efforts are required to ensure that these state of the art technologies provide reliable and clinically meaningful results accessible to the wider haematology community.

Transmission of diffuse large B cell lymphoma by an allogeneic stem-cell transplant

Cancer development is an evolutionary process driven by the acquisition of stochastic mutations, some of which increase cellular fitness in a co-evolving microenvironment.[1][1] Evidence across multiple cancer types demonstrates that this process is highly protracted, likely beginning years or even