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Background: Mantle cell lymphoma (MCL) is a rare, highly heterogeneous type of B-cell non-Hodgkin's lymphoma. The sumoylation pathway is known to be upregulated in many cancers including lymphoid malignancies. However, little is known about its oncogenic role in MCL. Methods: Levels of sumoylation enzymes and sumoylated proteins were quantified in MCL cell lines and primary MCL patient samples by scRNA sequencing and immunoblotting. The sumoylation enzyme SAE2 was genetically and pharmacologically targeted with shRNA and TAK-981 (subasumstat). The effects of SAE2 inhibition on MCL proliferation and cell cycle were evaluated using confocal microscopy, live-cell microscopy, and flow cytometry. Immunoprecipitation and orbitrap mass spectrometry were used to identify proteins targeted by sumoylation in MCL cells. Results: MCL cells have significant upregulation of the sumoylation pathway at the level of the enzymes SAE1 and SAE2 which correlated with poor prognosis and induction of mitosis associated genes. Selective inhibition of SAE2 with TAK-981 results in significant MCL cell death in vitro and in vivo with mitotic dysregulation being an important mechanism of action. We uncovered a sumoylation program in mitotic MCL cells comprised of multiple pathways which could be directly targeted with TAK-981. Centromeric localization of topoisomerase 2A, a gene highly upregulated in SAE1 and SAE2 overexpressing MCL cells, was lost with TAK-981 treatment likely contributing to the mitotic dysregulation seen in MCL cells. Conclusions: This study not only validates SAE2 as a therapeutic target in MCL but also opens the door to further mechanistic work to uncover how to best use desumoylation therapy to treat MCL and other lymphoid malignancies. [ABSTRACT FROM AUTHOR]

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy for which novel therapeutics with improved efficacy are greatly needed. To provide support for clinical immune checkpoint blockade, we comprehensively evaluated the expression of therapeutically targetable immune checkpoint molecules on primary MCL cells. MCL cells showed constitutive expression of Programmed Death 1 (PD-1) and Programmed Death Ligand 1 (PD-L1), variable CD200, absent PD-L2, Lymphocyte Activation Gene 3 (LAG-3), and Cytotoxic T-cell Associated Protein 4 (CTLA-4). Effector cells from MCL patients expressed PD-1. Co-culture of MCL cells with T-cells induced PD-L1 surface expression, a phenomenon regulated by IFNγ and CD40:CD40L interaction. Induction of PD-L1 was attenuated by concurrent treatment with ibrutinib or duvelisib, suggesting BTK and PI3K are important mediators of PD-L1 expression. Overall, our data provide further insight into the expression of checkpoint molecules in MCL and support the use of PD-L1 blocking antibodies in MCL patients. [ABSTRACT FROM AUTHOR]

Histone deacetylase inhibitors (HDACi) have proven activity in hematologic malignancies, and their FDA approval in multiple myeloma (MM) and T-cell lymphoma highlights the need for further development of this drug class. We investigated AR-42, an oral pan-HDACi, in a first-in-man phase 1 dose escalation clinical trial. Overall, treatment was well tolerated, no DLTs were evident, and the MTD was defined as 40 mg dosed three times weekly for three weeks of a 28-day cycle. One patient each with MM and mantle cell lymphoma demonstrated disease control for 19 and 27 months (ongoing), respectively. Treatment was associated with reduction of serum CD44, a transmembrane glycoprotein associated with steroid and immunomodulatory drug resistance in MM. Our findings indicate that AR-42 is safe and that further investigation of AR-42 in combination regimens for the treatment of patients with lymphoma and MM is warranted. Trial registration:http://clinicaltrials.gov/ct2/show/NCT01129193 [ABSTRACT FROM PUBLISHER]

BACKGROUND: In vitro studies in mantle cell lymphoma (MCL) cell lines and patient-derived cells have demonstrated synergistic apoptosis with combined rituximab and bortezomib (R-bortezomib) compared with single-agent bortezomib. Therefore, the authors of this report evaluated R-bortezomib in a preclinical model and in a phase 2 clinical trial. METHODS: A Hu-MCL-severe combined immunodeficiency (SCID) model engrafted with the Jeko cell line was treated with R-bortezomib, bortezomib, or rituximab. Twenty-five patients with relapsed follicular lymphoma (n = 11) and MCL (n = 14) received 375 mg/m² rituximab on Days 1 and 8 and 1.3 to 1.5 mg/m² bortezomib on Days 1, 4, 8, and 11 every 21 days for a median of 3 cycles (range, 1-5 cycles). RESULTS: R-bortezomib resulted in a statistically significant improvement in overall survival in Hu-MCL-SCID mice. In the clinical trial, the overall response rate was 40% in all 25 patients, 55% in patients with follicular lymphoma, and 29% in patients with MCL. The estimated 2-year progressionfree survival (PFS) rate was 24% (95% confidence interval [CI], 10%-53%) in all patients and 60% (95% CI, 20%-85%) in responding patients. Thirteen patients (52%) developed grade 3 neurotoxicity, which consisted of constipation/ ileus, sensory or motor neuropathy, or orthostatic hypotension. Patients who were heterozygous for the CD32a (Fcc receptor IIa) 131 histidine (H) to arginine (R) polymorphism had a significantly decreased PFS (P = .009) after R-bortezomib compared with HH and RR homozygotes. CONCLUSIONS: R-bortezomib had significant activity in patients with relapsed or refractory follicular lymphoma and MCL, although an unexpectedly high incidence of grade 3 neurologic toxicity was a potential limiting factor with this combination. [ABSTRACT FROM AUTHOR]

We evaluated the safety and efficacy of the purine nucleoside analogue, clofarabine, in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL). Six patients with DLBCL (n = 5) or MCL (n = 1) and a median age of 68 years were treated with 40 mg/m2 clofarabine IV over 2 h for 5 days, repeated every 28 days, for 1-2 cycles. The overall response rate was 50% (complete response = 1, complete response unconfirmed = 1, partial response = 1). Median progression-free survival was 3.5 months (range 1.5-10 months) and the median overall survival was 7.8 months (range 3-31 months). Grade 3-4 neutropenia and thrombocytopenia was universal, with a median of 34 (range 19-55) and 77 (range 0-275) days required for neutrophil and platelet recovery. Grade 3 non-hematologic toxicities included transaminitis, febrile neutropenia, non-neutropenic infections and orthostatic hypotension. Further accrual to the study was terminated due to prolonged Grade 3-4 myelosuppression and orthostatic hypotension in five of six patients. Clofarabine exhibits evidence of single agent activity in relapsed or refractory DLBCL. However, further study with novel administration schedules that maintain this efficacy and limit toxicity is warranted. [ABSTRACT FROM AUTHOR]

Protein arginine methyltransferase PRMT5 interacts with human SWI/SNF complexes and methylates histones H3R8 and H4R3. To elucidate the role of PRMT5 in human cancer, we analyzed PRMT5 expression in normal human B lymphocytes and a panel of lymphoid cancer cell lines as well as mantle cell lymphoma (MCL) clinical samples. We show that PRMT5 protein levels are elevated in all cancer cells, including clinical samples examined despite its low rate of transcription and messenger RNA stability. Remarkably, polysome profiling revealed that PRMT5 mRNA is translated more efficiently in Mino and JeKo MCL cells than in normal B cells, and that decreased miR-92b and miR-96 expression augments PRMT5 translation. Consequently, global methylation of H3R8 and H4R3 is increased and is accompanied by repression of suppressor of tumorigenecity 7 (ST7) in lymphoid cancer cells. Furthermore, knockdown of PRMT5 expression reduces proliferation of transformed JeKo and Raji cells. Thus, our studies indicate that aberrant expression of PRMT5 leads to altered epigenetic modification of chromatin, which in turn impacts transcriptional performance of anti-cancer genes and growth of transformed lymphoid cells. [ABSTRACT FROM AUTHOR]

Targeting lineage-defined transcriptional dependencies has emerged as an effective therapeutic strategy in cancer treatment. Through screening for molecular vulnerabilities of mantle cell lymphoma (MCL), we identified a set of transcription factors (TFs) including FOXO1, EBF1, PAX5, and IRF4 that are essential for MCL propagation. Integrated chromatin immunoprecipitation and sequencing (ChIP-Seq) with transcriptional network reconstruction analysis revealed FOXO1 as a master regulator that acts upstream in the regulatory TF hierarchy. FOXO1 is both necessary and sufficient to drive MCL lineage commitment through supporting the lineage-specific transcription programs. We further show that FOXO1, but not its close paralog FOXO3, can reprogram myeloid leukemia cells and induce B-lineage gene expression. Finally, we demonstrate that cpd10, a small molecule identified from an enriched FOXO1 inhibitor library, induces a robust cytotoxic response in MCL cells in vitro and suppresses MCL progression in vivo. Our findings establish FOXO1 inhibition as a therapeutic strategy targeting lineage-driven transcriptional addiction in MCL. [ABSTRACT FROM AUTHOR]

Protein arginine methyltransferase-5 (PRMT5) is overexpressed in aggressive B-cell non-Hodgkin's lymphomas, including mantle cell lymphoma and diffuse large B-cell lymphoma, and supports constitutive expression of CYCLIN D1 and c-MYC. Here, we combined ChIP analysis with next-generation sequencing to identify microRNA (miRNA) genes that are targeted by PRMT5 in aggressive lymphoma cell lines. We identified enrichment of histone 3 dimethylation at Arg-8 (H3(Me2)R8) in the promoter regions of miR33b, miR96, and miR503. PRMT5 knockdown de-repressed transcription of all three miRNAs, accompanied by loss of recruitment of epigenetic repressor complexes containing PRMT5 and either histone deacetylase 2 (HDAC2) or HDAC3, enhanced binding of co-activator complexes containing p300 or CREB-binding protein (CBP), and increased acetylation of specific histones, including H2BK12, H3K9, H3K14, and H4K8 at the miRNA promoters. Re-expression of individual miRNAs in B-cell lymphoma cells down-regulated expression of PRMT5, CYCLIN D1, and c-MYC, which are all predicted targets of these miRNAs, and reduced lymphoma cell survival. Luciferase reporter assays with WT and mutant 3'UTRs of CYCLIN D1 and c-MYC mRNAs revealed that binding sites for miR33b, miR96, and miR503 are critical for translational regulation of the transcripts of these two genes. Our findings link altered PRMT5 expression to transcriptional silencing of tumor-suppressing miRNAs in lymphoma cells and reinforce PRMT5's relevance for promoting lymphoma cell growth and survival. [ABSTRACT FROM AUTHOR]

Mantle-cell lymphoma (MCL) remains incurable despite numerous therapeutic advances. OSU-2S, a novel nonimmunosuppressive FTY720 (Fingolimod) derivative, exhibits potent cytotoxicity in MCL cell lines and primary cells. OSU-2S increased the surface expression of CD74, a therapeutic antibody target in MCL cells. OSU-2S, in combination with anti-CD74 antibody milatuzumab, enhanced cytotoxicity in MCL. Moreover, MCL tumor antigen receptor tyrosine kinase-like orphan receptor 1 (ROR1) targeted immunonanoparticle-carrying OSU-2S (2A2-OSU-2S-ILP)-mediated selective cytotoxicity of MCL in vitro, as well as activity in a xenografted mouse model of MCL in vivo. The newly developed OSU-2S delivery using ROR1-directed immunonanoparticles provide selective targeting of OSU-2S to MCL and other ROR1 + malignancies, sparing normal B cells. [ABSTRACT FROM AUTHOR]