Dysregulation of the histone methyltransferase EZH2 plays a critical role in the development of a variety of malignancies including B-cell lymphomas. As a result, a series of small molecule ...inhibitors of EZH2 have been developed and studied in the pre-clinical setting. Three EZH2 inhibitors: tazemetostat (EPZ-6438), GSK2816126 and CPI-1205 have moved into phase I/phase II clinical trials in patients with non-Hodgkin lymphoma and genetically defined solid tumors. Early data from the tazemetostat trials indicate an acceptable safety profile and early signs of activity in diffuse large B-cell lymphoma and follicular lymphoma, including patients with EZH2 wild-type and mutant tumors. In this review, we present the rationale, key pre-clinical and early clinical findings of small molecule EZH2 inhibitors for use in lymphoma as well as future challenges and potential opportunities for combination therapies.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Intravital confocal microscopy and two-photon microscopy are powerful tools to explore the dynamic behavior of immune cells in mouse lymph nodes (LNs), with penetration depth of ~100 and ~300 μm, ...respectively. Here, we used intravital three-photon microscopy to visualize the popliteal LN through its entire depth (600-900 μm). We determined the laser average power and pulse energy that caused measurable perturbation in lymphocyte migration. Long-wavelength three-photon imaging within permissible parameters was able to image the entire LN vasculature in vivo and measure CD8
T cells and CD4
T cell motility in the T cell zone over the entire depth of the LN. We observed that the motility of naive CD4
T cells in the T cell zone during lipopolysaccharide-induced inflammation was dependent on depth. As such, intravital three-photon microscopy had the potential to examine immune cell behavior in the deeper regions of the LN in vivo.
Although we are just beginning to understand the mechanisms that regulate the epigenome, aberrant epigenetic programming has already emerged as a hallmark of hematologic malignancies including acute ...myeloid leukemia (AML) and B-cell lymphomas. Although these diseases arise from the hematopoietic system, the epigenetic mechanisms that drive these malignancies are quite different. Yet, in all of these tumors, somatic mutations in transcription factors and epigenetic modifiers are the most commonly mutated set of genes and result in multilayered disruption of the epigenome. Myeloid and lymphoid neoplasms generally manifest epigenetic allele diversity, which contributes to tumor cell population fitness regardless of the underlying genetics. Epigenetic therapies are emerging as one of the most promising new approaches for these patients. However, effective targeting of the epigenome must consider the need to restore the various layers of epigenetic marks, appropriate biological end points, and specificity of therapeutic agents to truly realize the potential of this modality.
Most antigen discovery and vaccine development aimed at driving functional B cell responses rely on mouse immunizations studies. To date, there is no 3D ex vivo immune tissues, which are capable of ...driving antigen-specific B cell responses to rapidly determine the humoral immunogenicity of antigens, understand the role of extracellular matrix in humoral immunity, and generate high affinity antibody responses. This can be attributed to the complexity of B cell differentiation and affinity maturation process in the germinal center (GC) reaction, which makes these highly specialized cells susceptible to rapid apoptosis ex vivo. We have previously reported immune tissues that show ex vivo GC-like response, however in a non-antigen specific manner. Here, we report a maleimide (MAL)-functionalized polyethylene glycol (PEG)-based designer immune tissues that modulate B cell differentiation and enriches antigen-specific GC B cells in the presence of T-cell like signals. With the 3D synthetic immune tissue platform, we assessed various hydrogel design parameters to control ex vivo GC reaction. Using an Ezh2fl/fl Cγ1-cre transgenic mouse model, we demonstrated ex vivo IgG1 antibody class switching. Using immune tissues developed from a B1-8hi mutant mouse that represents a recombined antibody variable region derived from a 4-hydroxy-3-nitrophenylacetyl (NP) hapten binding antibody (B1-8), we demonstrate antigen specificity and selective enrichment of antigen-specific B cells with high affinity at both cell surface and secreted levels in integrin ligand-dependent manner. The ex vivo antigen-specific platform technology offers use in scientific understanding of immunobiology, matrix immunology, and in biotechnology applications, ranging from the antigen testing, vaccine development, and generation of antibodies against diseases.
B-cell non-Hodgkin lymphomas (B-NHLs) are highly heterogenous by genetic, phenotypic, and clinical appearance. Next-generation sequencing technologies and multi-dimensional data analyses have further ...refined the way these diseases can be more precisely classified by specific genomic, epigenomic, and transcriptomic characteristics. The molecular and genetic heterogeneity of B-NHLs may contribute to the poor outcome of some of these diseases, suggesting that more personalized precision-medicine approaches are needed for improved therapeutic efficacy. The germinal center (GC) B-cell like diffuse large B-cell lymphomas (GCB-DLBCLs) and follicular lymphomas (FLs) share specific epigenetic programs. These diseases often remain difficult to treat and surprisingly do not respond advanced immunotherapies, despite arising in secondary lymphoid organs at sites of antigen recognition. Epigenetic dysregulation is a hallmark of GCB-DLBCLs and FLs, with gain-of-function (GOF) mutations in the histone methyltransferase
, loss-of-function (LOF) mutations in histone acetyl transferases
and
, and the histone methyltransferase
representing the most prevalent genetic lesions driving these diseases. These mutations have the common effect to disrupt the interactions between lymphoma cells and the immune microenvironment, via decreased antigen presentation and responsiveness to IFN-γ and CD40 signaling pathways. This indicates that immune evasion is a key step in GC B-cell lymphomagenesis. EZH2 inhibitors are now approved for the treatment of FL and selective HDAC3 inhibitors counteracting the effects of
LOF mutations are under development. These treatments can help restore the immune control of GCB lymphomas, and may represent optimal candidate agents for more effective combination with immunotherapies. Here, we review recent progress in understanding the impact of mutant chromatin modifiers on immune evasion in GCB lymphomas. We provide new insights on how the epigenetic program of these diseases may be regulated at the level of metabolism, discussing the role of metabolic intermediates as cofactors of epigenetic enzymes. In addition, lymphoma metabolic adaptation can negatively influence the immune microenvironment, further contributing to the development of immune cold tumors, poorly infiltrated by effector immune cells. Based on these findings, we discuss relevant candidate epigenetic/metabolic/immune targets for rational combination therapies to investigate as more effective precision-medicine approaches for GCB lymphomas.
BCOR is a component of a variant Polycomb repressive complex 1 (PRC1.1). PRC1 and PRC2 complexes together constitute a major gene regulatory system critical for appropriate cellular differentiation. ...The gene is upregulated in germinal center (GC) B cells and mutated in a number of hematologic malignancies. We report BCOR inactivating alterations in 4/7 classic Hodgkin lymphoma (cHL) cell lines, subclonal somatic mutations in Hodgkin and Reed-Sternberg (HRS) cells of 4/10 cHL cases, and deletions in HRS cells of 7/17 primary cHL cases. In mice, conditional loss of Bcor driven by AID-Cre in GC B cells resulted in gene expression changes of 46 genes (>2-fold) including upregulated Lef1 that encodes a transcription factor responsible for establishing T-cell identity and Il9r (interleukin-9 receptor), an important member of the cytokine network in cHL. Our findings suggest a role for BCOR loss in cHL pathogenesis and GC-B cell homeostasis.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The EZH2 histone methyltransferase is required for B cells to form germinal centers (GC). Here we show that EZH2 mediates GC formation through repression of cyclin-dependent kinase inhibitor CDKN1A ...(p21
). Deletion of Cdkn1a rescues the GC reaction in Ezh2
mice. Using a 3D B cell follicular organoid system that mimics the GC reaction, we show that depletion of EZH2 suppresses G1 to S phase transition of GC B cells in a Cdkn1a-dependent manner. GC B cells of Cdkn1a
Ezh2
mice have high levels of phospho-Rb, indicating that loss of Cdkn1a enables progression of cell cycle. Moreover, the transcription factor E2F1 induces EZH2 during the GC reaction. E2f1
mice manifest impaired GC responses, which is rescued by restoring EZH2 expression, thus defining a positive feedback loop in which EZH2 controls GC B cell proliferation by suppressing CDKN1A, enabling cell cycle progression with a concomitant phosphorylation of Rb and release of E2F1.The histone methyltransferase EZH2 silences genes by generating H3K27me3 marks. Here the authors use a 3D GC organoid and show EZH2 mediates germinal centre (GC) formation through epigenetic silencing of CDKN1A and release of cell cycle checkpoints.
We performed a genomic, transcriptomic, and immunophenotypic study of 347 patients with diffuse large B-cell lymphoma (DLBCL) to uncover the molecular basis underlying acquired deficiency of MHC ...expression. Low MHC-II expression defines tumors originating from the centroblast-rich dark zone of the germinal center (GC) that was associated with inferior prognosis. MHC-II-deficient tumors were characterized by somatically acquired gene mutations reducing MHC-II expression and a lower amount of tumor-infiltrating lymphocytes. In particular, we demonstrated a strong enrichment of
mutations in both MHC-I- and MHC-II-negative primary lymphomas, and observed reduced MHC expression and T-cell infiltrates in murine lymphoma models expressing mutant
. Of clinical relevance, EZH2 inhibitors significantly restored MHC expression in
-mutated human DLBCL cell lines. Hence, our findings suggest a tumor progression model of acquired immune escape in GC-derived lymphomas and pave the way for development of complementary therapeutic approaches combining immunotherapy with epigenetic reprogramming. SIGNIFICANCE: We demonstrate how MHC-deficient lymphoid tumors evolve in a cell-of-origin-specific context. Specifically,
mutations were identified as a genetic mechanism underlying acquired MHC deficiency. The paradigmatic restoration of MHC expression by EZH2 inhibitors provides the rationale for synergistic therapies combining immunotherapies with epigenetic reprogramming to enhance tumor recognition and elimination.
.
.
Cancer evolution is fueled by epigenetic as well as genetic diversity. In chronic lymphocytic leukemia (CLL), intra-tumoral DNA methylation (DNAme) heterogeneity empowers evolution. Here, to ...comprehensively study the epigenetic dimension of cancer evolution, we integrate DNAme analysis with histone modification mapping and single cell analyses of RNA expression and DNAme in 22 primary CLL and 13 healthy donor B lymphocyte samples. Our data reveal corrupted coherence across different layers of the CLL epigenome. This manifests in decreased mutual information across epigenetic modifications and gene expression attributed to cell-to-cell heterogeneity. Disrupted epigenetic-transcriptional coordination in CLL is also reflected in the dysregulation of the transcriptional output as a function of the combinatorial chromatin states, including incomplete Polycomb-mediated gene silencing. Notably, we observe unexpected co-mapping of typically mutually exclusive activating and repressing histone modifications, suggestive of intra-tumoral epigenetic diversity. Thus, CLL epigenetic diversification leads to decreased coordination across layers of epigenetic information, likely reflecting an admixture of cells with diverging cellular identities.
PDF
