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Non-Hodgkin lymphoma (NHL) is a heterogeneous group of blood cancers arising in lymphoid tissues that commonly effects both humans and dogs. Protein arginine methyltransferase 5 (PRMT5), an enzyme that catalyzes the symmetric di-methylation of arginine residues, is frequently overexpressed and dysregulated in both human solid and hematologic malignancies. In human lymphoma, PRMT5 is a known driver of malignant transformation and oncogenesis, however, the expression and role of PRMT5 in canine lymphoma has not been explored. To explore canine lymphoma as a useful comparison to human lymphoma while validating PRMT5 as a rational therapeutic target in both, we characterized expression patterns of PRMT5 in canine lymphoma tissue microarrays, primary lymphoid biopsies, and canine lymphoma-derived cell lines. The inhibition of PRMT5 led to growth suppression and induction of apoptosis, while selectively decreasing global marks of symmetric dimethylarginine (SDMA) and histone H4 arginine 3 symmetric dimethylation. We performed ATAC-sequencing and gene expression microarrays with pathway enrichment analysis to characterize genome-wide changes in chromatin accessibility and whole-transcriptome changes in canine lymphoma cells lines upon PRMT5 inhibition. This work validates PRMT5 as a promising therapeutic target for canine lymphoma and supports the continued use of the spontaneously occurring canine lymphoma model for the preclinical development of PRMT5 inhibitors for the treatment of human NHL. [ABSTRACT FROM AUTHOR]

Human immunodeficiency virus type 1 (HIV-1) latency is a major barrier to a cure of AIDS. Latently infected cells harbor an integrated HIV-1 genome but are not actively producing HIV-1. Histone deacetylase (HDAC) inhibitors, such as vorinostat (SAHA), have been shown to reactivate latent HIV-1. AR-42, a modified HDAC inhibitor, has demonstrated efficacy against malignant melanoma, meningioma, and acute myeloid leukemia and is currently used in clinical trials for non-Hodgkin's lymphoma and multiple myeloma. In this study, we evaluated the ability of AR-42 to reactivate HIV-1 in the two established CD4+ T-cell line models of HIV-1 latency. In HIV-1 chronically infected ACH-2 cells, AR-42-induced histone acetylation was more potent and robust than that of vorinostat. Although AR-42 and vorinostat were equipotent in their ability to reactivate HIV-1, AR-42-induced maximal HIV-1 reactivation was twofold greater than vorinostat in ACH-2 and J-Lat (clone 9.2) cells. These data provide rationale for assessing the efficacy of AR-42-mediated HIV-1 reactivation within primary CD4+ T-cells. [ABSTRACT FROM AUTHOR]

Protein arginine methyltransferase-5 (PRMT5) is a Type II arginine methyltransferase that regulates various cellular functions. We hypothesized that PRMT5 plays a role in regulating the growth of human melanoma cells. Immunohistochemical analysis indicated significant upregulation of PRMT5 in human melanocytic nevi, malignant melanomas and metastatic melanomas as compared to normal epidermis. Furthermore, nuclear PRMT5 was significantly decreased in metastatic melanomas as compared to primary cutaneous melanomas. In human metastatic melanoma cell lines, PRMT5 was predominantly cytoplasmic, and associated with its enzymatic cofactor Mep50, but not STAT3 or cyclin D1. However, histologic examination of tumor xenografts from athymic mice revealed heterogeneous nuclear and cytoplasmic PRMT5 expression. Depletion of PRMT5 via siRNA inhibited proliferation in a subset of melanoma cell lines, while it accelerated growth of others. Loss of PRMT5 also led to reduced expression of MITF (microphthalmia-associated transcription factor), a melanocyte-lineage specific oncogene, and increased expression of the cell cycle regulator p27Kip1. These results are the first to report elevated PRMT5 expression in human melanoma specimens and indicate this protein may regulate MITF and p27Kip1 expression in human melanoma cells. [ABSTRACT FROM AUTHOR]

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]

Mutation of BRG1, hBRM, and their associated factors, INI1 and BAF57, in primary human tumors has suggested that inactivation of human SWI/SNF (hSW1/SNF) complexes may be involved in neoplastic transformation. BT549 is an invasive human breast carcinoma cell line that lacks expression of BAF57, a key hSWI/SNF subunit that mediates interaction with transcriptional activators and corepressors. In this study we investigated the role of BAF57 in suppressing tumorigenesis by establishing BT549 stable cell lines that expresses full-length BAF57 protein. BT549 clones expressing BAF57 demonstrated marked phenotypic changes, slow growth kinetics, and restoration of contact inhibition. Altered growth was found to be due in part to cell cycle arrest and induction of apoptosis. Furthermore, microarray analysis revealed that BAF57-mediated cell death was associated with up-regulation of proapoptotic genes including the tumor suppressor familial cylindromatosis (CYLD), which was found to be a direct target of BAF57 as determined by chromatin immunoprecipitation analysis. Increased expression of CYLD in BT549 cells induced apoptosis, while its suppression by small interfering RNA inhibited cell death in BAF57 expressing BT549 cells. These findings demonstrate the importance of BAF57 in cell growth regulation and provide a novel link between hSWI/SNF chromatin remodelers and apoptosis. [ABSTRACT FROM AUTHOR]

Background: Immune-compromised individuals are at increased risk for developing aggressive Epstein-Barr virus (EBV)-associated lymphoproliferative disorders after primary EBV infection or for reactivation of a preexisting latent EBV infection. We evaluated the effect of depsipeptide, a histone deacetylase inhibitor, on EBV-positive lymphoblastoid cell lines (LCLs) and Burkitt lymphoma cell lines in a mouse model and explored its mechanism of action in vitro. Methods: We studied EBV-transformed LCLs, which express a latent III (Lat-III) viral gene profile, as do some EBV-positive lymphoproliferative malignancies, and Burkitt lymphoma cell lines, which express a Lat-I viral gene profile. Cell lines were used to characterize depsipeptide-induced apoptosis, which was evaluated by flow cytometry. Flow cytometry, western blot analyses, and histone deacetylase inhibitors were used to investigate components of prodeath and survival pathways in vitro. We studied depsipeptide's effects on survival with a mouse xenograft model of EBV-positive human B-cell tumors (groups of 10 mice). All statistical tests were two-sided. Results: Depsipeptide (5 mg/m² of body surface area) treatment was associated with statistically significantly improved survival of mice carrying Lat-III EBV-positive LCL tumors, compared with that of control-treated mice (day 30: for depsipeptide-treated mice, 90% survival, 95% confidence interval [CI] = 73.2% to 100%; for control-treated mice, 20% survival, 95% CI = 5.79% to 69.1%; P<.001), but it was not associated with survival of mice carrying Lat-I EBV-positive Burkitt lymphoma tumors. Depsipeptide induced apoptosis in 64% of LCLs and in 14 % of EBV-positive Burkitt lymphoma cells in vitro. Depsipeptide-treated LCL cultures had two distinct cell populations—one sensitive and one resistant to depsipeptide. Depsipeptide-mediated apoptosis was associated with a 12-fold increased level of active caspase 3, but some apoptosis persisted despite z-VAD-fmk treatment to inhibit caspase activity. Depsipeptide-resistant LCLs expressed higher levels of latent membrane protein 1 (LMP1; P = .017), BCL2 (P = .032), and nuclear factor κB (NF-κB) (P<.001) than depsipeptide-sensitive LCLs; this resistance was circumvented by treatment with PS-1145, an inhibitor of NF-κB activation (P<.001). Conclusions: Apoptosis is induced by depsipeptide via caspase-dependent and -independent pathways in Lat-III EBV-positive LCLs and is enhanced by inhibiting NF-κB activity. Depsipeptide as a treatment for Lat-III EBV-associated lymphoproliferative disorders should be explored further in clinical trials. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we present a workflow to understand the modulator of ibrutinib resistance in ABC diffuse large B cell lymphoma by integrating Metabolomics and Gene expression profiling as shown in the graphical abstract. We performed an untargeted metabolomics analysis using a Q-Exactive high-resolution mass spectrometer to dissect the metabolic reprogramming associated with acquired ibrutinib resistance in paired ibrutinib-sensitive and ibrutinib-resistant DLBCL cell lines. Further, we identified common denominators, integrating metabolome and transcriptome data, confirming clinical significance, integrating pathways, and identifying the candidate gene driving ibrutinib resistance and metabolic reprogramming. Our work demonstrates that a multi-omics approach can be a robust and impartial strategy to uncover genes and pathways that cause metabolic deregulation in cancer cells. Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma (NHL). B-cell NHLs rely on Bruton's tyrosine kinase (BTK) mediated B-cell receptor signaling for survival and disease progression. However, they are often resistant to BTK inhibitors or soon acquire resistance after drug exposure resulting in the drug-tolerant form. The drug-tolerant clones proliferate faster, have increased metabolic activity, and shift to oxidative phosphorylation; however, how this metabolic programming occurs in the drug-resistant tumor is poorly understood. In this study, we explored for the first time the metabolic regulators of ibrutinib-resistant activated B-cell (ABC) DLBCL using a multi-omics analysis that integrated metabolomics (using high-resolution mass spectrometry) and transcriptomic (gene expression analysis). Overlay of the unbiased statistical analyses, genetic perturbation, and pharmaceutical inhibition was further used to identify the key players contributing to the metabolic reprogramming of the drug-resistant clone. Gene-metabolite integration revealed interleukin four induced 1 (IL4I1) at the crosstalk of two significantly altered metabolic pathways involved in producing various amino acids. We showed for the first time that drug-resistant clones undergo metabolic reprogramming towards oxidative phosphorylation and are modulated via the BTK-PI3K-AKT-IL4I1 axis. Our report shows how these cells become dependent on PI3K/AKT signaling for survival after acquiring ibrutinib resistance and shift to sustained oxidative phosphorylation; additionally, we outline the compensatory pathway that might regulate this metabolic reprogramming in the drug-resistant cells. These findings from our unbiased analyses highlight the role of metabolic reprogramming during drug resistance development. Our work demonstrates that a multi-omics approach can be a robust and impartial strategy to uncover genes and pathways that drive metabolic deregulation in cancer cells. [ABSTRACT FROM AUTHOR]

Protein arginine methyltransferase-5 (PRMT5) is a Type II arginine methyltransferase that regulates various cellular functions. We hypothesized that PRMT5 plays a role in regulating the growth of human melanoma cells. Immunohistochemical analysis indicated significant upregulation of PRMT5 in human melanocytic nevi, malignant melanomas and metastatic melanomas as compared to normal epidermis. Furthermore, nuclear PRMT5 was significantly decreased in metastatic melanomas as compared to primary cutaneous melanomas. In human metastatic melanoma cell lines, PRMT5 was predominantly cytoplasmic, and associated with its enzymatic cofactor Mep50, but not STAT3 or cyclin D1. However, histologic examination of tumor xenografts from athymic mice revealed heterogeneous nuclear and cytoplasmic PRMT5 expression. Depletion of PRMT5 via siRNA inhibited proliferation in a subset of melanoma cell lines, while it accelerated growth of others. Loss of PRMT5 also led to reduced expression of MITF (microphthalmia-associated transcription factor), a melanocyte-lineage specific oncogene, and increased expression of the cell cycle regulator p27Kip1. These results are the first to report elevated PRMT5 expression in human melanoma specimens and indicate this protein may regulate MITF and p27Kip1 expression in human melanoma cells. [ABSTRACT FROM AUTHOR]