Human Burkitt Lymphoma Cell Line Research Articles

PICH deficiency limits the progression of MYC-induced B-cell lymphoma

Plk1-interacting checkpoint helicase (PICH) is a DNA translocase involved in resolving ultrafine anaphase DNA bridges and, therefore, is important to safeguard chromosome segregation and stability. PICH is overexpressed in various human cancers, particularly in lymphomas such as Burkitt lymphoma, which is caused by MYC translocations. To investigate the relevance of PICH in cancer development and progression, we have combined novel PICH-deficient mouse models with the Eμ-Myc transgenic mouse model, which recapitulates B-cell lymphoma development. We have observed that PICH deficiency delays the onset of MYC-induced lymphomas in Pich heterozygous females. Moreover, using a Pich conditional knockout mouse model, we have found that Pich deletion in adult mice improves the survival of Eμ-Myc transgenic mice. Notably, we show that Pich deletion in healthy adult mice is well tolerated, supporting PICH as a suitable target for anticancer therapies. Finally, we have corroborated these findings in two human Burkitt lymphoma cell lines and we have found that the death of cancer cells was accompanied by chromosomal instability. Based on these findings, we propose PICH as a potential therapeutic target for Burkitt lymphoma and for other cancers where PICH is overexpressed.

DIAGNOSTIC YIELD OF IN VITRO VITREOUS BIOPSY FOR INTRAOCULAR LYMPHOMA AT VARIABLE VITREOUS CUTTER SPEEDS USING 25-GAUGE VITRECTOMY.

Primary vitreoretinal lymphoma is the most common intraocular lymphoproliferative disorder. We evaluated the diagnostic yield of pars plana vitrectomy, specifically using modern high cut rate dual-cycle cutters, on in vitro cell viability and diagnostic yield. Human Burkitt lymphoma cell line Namalwa at 2 x 10^5 cells/mL was aspirated by 25-gauge dual-blade guillotine-type vitrectomy at five speeds (500, 1,000, 4,000, 7,500, or 15,000 cuts per minute). Cell viability and diagnostic yield in each subtype group were determined using hemocytometry, viable cell count using Cell Counting Kit-8, and pathologist-guided manual count. No significant deviation in cell count was identified in any cut rate by ANOVA ( P = 0.61), and no trends in the number of viable cells were identified across cut rates (R 2 = 0.188, P = 0.47). Among histologic cell counts per cut-rate, neither linear regression (R = 0.531, P = 0.16) nor ANOVA ( P = 0.096) were statistically significant. There was no significant degradation in the number of viable cells with increasing cut speed. These results suggest that in contrast to previous findings using 20g or 23g vitrectomy for diagnostic vitrectomy, modern vitrectomy systems may be used at up to 15,000 cpm without compromising the viability of lymphoma cells.

Efficacy of Antibodies Targeting TfR1 in Xenograft Mouse Models of AIDS-Related Non-Hodgkin Lymphoma.

Transferrin receptor 1 (TfR1), also known as CD71, is a transmembrane protein involved in the cellular uptake of iron and the regulation of cell growth. This receptor is expressed at low levels on a variety of normal cells, but is upregulated on cells with a high rate of proliferation, including malignant cells and activated immune cells. Infection with the human immunodeficiency virus (HIV) leads to the chronic activation of B cells, resulting in high expression of TfR1, B-cell dysfunction, and ultimately the development of acquired immunodeficiency syndrome-related B-cell non-Hodgkin lymphoma (AIDS-NHL). Importantly, TfR1 expression is correlated with the stage and prognosis of NHL. Thus, it is a meaningful target for antibody-based NHL therapy. We previously developed a mouse/human chimeric IgG3 specific for TfR1 (ch128.1/IgG3) and showed that this antibody exhibits antitumor activity in an in vivo model of AIDS-NHL using NOD-SCID mice challenged intraperitoneally with 2F7 human Burkitt lymphoma (BL) cells that harbor the Epstein-Barr virus (EBV). We have also developed an IgG1 version of ch128.1 that shows significant antitumor activity in SCID-Beige mouse models of disseminated multiple myeloma, another B-cell malignancy. Here, we aim to explore the utility of ch128.1/IgG1 and its humanized version (hu128.1) in mouse models of AIDS-NHL. To accomplish this goal, we used the 2F7 cell line variant 2F7-BR44, which is more aggressive than the parental cell line and forms metastases in the brain of mice after systemic (intravenous) administration. We also used the human BL cell line JB, which in contrast to 2F7, is EBV-negative, allowing us to study both EBV-infected and non-infected NHL tumors. Treatment with ch128.1/IgG1 or hu128.1 of SCID-Beige mice challenged locally (subcutaneously) with 2F7-BR44 or JB cells results in significant antitumor activity against different stages of disease. Treatment of mice challenged systemically (intravenously) with either 2F7-BR44 or JB cells also showed significant antitumor activity, including long-term survival. Taken together, our results suggest that targeting TfR1 with antibodies, such as ch128.1/IgG1 or hu128.1, has potential as an effective therapy for AIDS-NHL.

Evaluation of potential cytotoxic and apoptotic effects of paclitaxel and docetaxel in human Burkitt lymphoma cell lines

Purpose: To study the cytotoxicity of paclitaxel and docetaxel on cell viability and apoptosis in Burkitt lymphoma cell lines.
 Methods: The cytotoxic activity of Paclitaxel and Docetaxel against Burkitt lymphoma cells was evaluated using the XTT cell viability test. The cells were exposed to increasing concentrations of paclitaxel and docetaxel ranging from 0.0001 to 10 μM for 48 h. Cell cycle analysis and apoptosis were also assessed using flow cytometry-based experiments.
 Results: Both paclitaxel and docetaxel exhibited a concentration-dependent cytotoxic effect with IC50 of 5.32 and 6.58 μM, respectively. Furthermore, paclitaxel and docetaxel were shown to have a significant apoptotic effect on Burkitt lymphoma cells (p < 0.01). Furthermore, paclitaxel and docetaxel arrested Burkitt lymphoma cells at the G2/M phase.
 Conclusion: Paclitaxel and docetaxel are potential candidates for the treatment of Burkitt lymphoma. Since both drugs are already licensed for many indications, the addition of Burkitt lymphoma to the list of indications of these drugs would be a much easier and faster process. However, there is a need for further in vitro and in vivo research to fully elucidate their mechanisms of action.

Phosphoglycerate Dehydrogenase Is Required for Germinal Center Formation and Is a Therapeutic Target in MYC-driven Lymphoma

The fields of cancer- and immuno-metabolism have re-emerged as areas of significant translational potential. Even though the upregulation of glycolysis by proliferating lymphocytes is the basis for widely used clinical tests such as FDG-PET, little is known about which metabolic pathways are involved in the utilization of glucose to support B-cell proliferation. The synthesis of serine from glucose has been demonstrated to be a key metabolic pathway supporting cellular proliferation in some healthy and malignant cell types. Importantly, this pathway is regulated by MYC, which is known to be essential for germinal centre formation and is commonly dysregulated in lymphoma. Despite this, the role that the serine synthesis pathway (SSP) plays in germinal center biology and pathology has not been previously investigated. We performed a comprehensive characterization of the role of the SSP in germinal center B cells and lymphomas derived from these cells.We demonstrate that upregulation of a functional SSP is a metabolic hallmark of B-cell activation and the germinal center reaction. We show that both human and murine resting naïve B cells lack expression of the first two enzymes in this pathway, phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase (PSAT1) enzymes. However, B-cell activation, predominantly through the B-cell receptor, robustly induces the expression of these enzymes in vitro, resulting in an acquired ability to synthesize serine, glycine and the purine nucleotides adenosine and guanosine from glucose. This is reflected in striking expression of PHGDH and PSAT1 within germinal centers but not in marginal zones confirming that this upregulation is occurring in germinal B cells activated in vivo. We then proceeded to investigate the impact of inhibiting PHGDH on germinal center formation and high-affinity antibody production in vivo. This was done both genetically, using a conditional B-cell knockout mouse model, and pharmacologically using a specific inhibitor of PHGDH, PH-755. Importantly, we show that PHGDH inhibition impairs germinal center formation with a resultant reduction in high-affinity antibody production. Mechanistic experiments demonstrate that PHGDH inhibition effectively blocks cells from synthesising serine and glycine from glucose, making them unable to proliferate in environments that lack these amino acids.We then investigated role of PHDGH and PSAT1 in Burkitt Lymphoma (BL), Diffuse Large B Cell Lymphoma (DLBCL) and Chronic Lymphocytic Leukemia (CLL). Notably, very high expression of these two proteins was observed in BL, with intermediate-to-high expression in DLBCL and relatively low expression in CLL, where expression was restricted to proliferation centers. Given the heterogeneity of expression in DLBCL patients, we next interrogated a published GSE database (Lenz et al. NEJM 2008) to investigate the impact on outcome. Notably high expression of PSAT1 was significantly associated with a poorer overall survival rate in DLBCL.We then investigated whether the SSP could be a therapeutic target in lymphoma. We demonstrate that PHGDH inhibition effectively inhibits de novo serine, glycine and purine nucleotide synthesis from glucose, resulting in impaired proliferation and increased apoptosis in a panel of human BL cell lines in vitro. We then analyzed the impact of PHGDH inhibition on lymphoma development in vivo using Eµ-myc mice, which harbour Myc coupled to the IgH enhancer characteristic of BL. Importantly we confirm the role of MYC by demonstrating that Eµ-Myc B-cells show significantly higher expression of PHGDH and PSAT1 expression resulting in increased serine and glycine synthesis when compared to control cells. We demonstrate that pharmacological inhibition of PHGDH using PH-755 impairs lymphoma progression in this model. We confirm the importance of PHGDH by showing that genetic ablation of Phgdh in Eµ-myc cells in a tamoxifen inducible system (using Eµ-myc/+;Rosa26-CreER T2/+;Phgdh fl/fl mice) also results in a significant reduction in lymphoma progression.Taken together, this work represents the first report of the role of the SSP in the biology of the germinal centre response and lymphomas derived from these cells. These findings establish PHGDH as a critical player in humoral immunity and a clinically relevant target in MYC-driven lymphoma, which is an area of significant unmet need. DisclosuresGribben: Abbvie: Honoraria; AZ: Honoraria, Research Funding; BMS: Honoraria; Gilead/Kite: Honoraria; Janssen: Honoraria, Research Funding; Morphosys: Honoraria; Novartis: Honoraria; Takeda: Honoraria; TG Therapeutis: Honoraria. Calado: Myricx Pharma: Consultancy, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Patents & Royalties: Cancer Treatments. WO patent WO 2020/128475 A1 (2020).

Frequent mutations of FBXO11 highlight BCL6 as a therapeutic target in Burkitt lymphoma

AbstractThe expression of BCL6 in B-cell lymphoma can be deregulated by chromosomal translocations, somatic mutations in the promoter regulatory regions, or reduced proteasome-mediated degradation. FBXO11 was recently identified as a ubiquitin ligase that is involved in the degradation of BCL6, and it is frequently inactivated in lymphoma or other tumors. Here, we show that FBXO11 mutations are found in 23% of patients with Burkitt lymphoma (BL). FBXO11 mutations impaired BCL6 degradation, and the deletion of FBXO11 protein completely stabilized BCL6 levels in human BL cell lines. Conditional deletion of 1 or 2 copies of the FBXO11 gene in mice cooperated with oncogenic MYC and accelerated B-cell lymphoma onset, providing experimental evidence that FBXO11 is a haploinsufficient oncosuppressor in B-cell lymphoma. In wild-type and FBXO11-deficient BL mouse and human cell lines, targeting BCL6 via specific degraders or inhibitors partially impaired lymphoma growth in vitro and in vivo. Inhibition of MYC by the Omomyc mini-protein blocked cell proliferation and increased apoptosis, effects further increased by combined BCL6 targeting. Thus, by validating the functional role of FBXO11 mutations in BL, we further highlight the key role of BCL6 in BL biology and provide evidence that innovative therapeutic approaches, such as BCL6 degraders and direct MYC inhibition, could be exploited as a targeted therapy for BL.

Nanoencapsulated rituximab mediates superior cellular immunity against metastatic B-cell lymphoma in a complement competent humanized mouse model

BackgroundDespite the numerous applications of monoclonal antibodies (mAbs) in cancer therapeutics, animal models available to test the therapeutic efficacy of new mAbs are limited. NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice are one...

BI6727, a polo-like kinase 1 inhibitor with promising efficacy on Burkitt lymphoma cells

ObjectiveBI6727, an ATP-competitive PLK1 inhibitor, has been shown to cause cell death in multi-tumors. This study aimed to investigate the anti-tumor effect and potential molecular mechanism of BI6727 in human Burkitt lymphoma (BL) cell lines.MethodsWe assessed polo-like kinase 1 (PLK1) expression in BL patient tissues and cells, also investigated the cytotoxic effect using CCK8 assay and flow cytometry. In addition, western blotting and real-time polymerase chain reaction (RT-PCR) assays were used to explore the molecular mechanisms of BI6727 in human BL cell lines.ResultsPLK1 was overexpressed in BL cells compared with normal cells. The PLK1 inhibitor BI6727 reduced activated PLK1 expression and caused mitotic arrest in BL cells. Additionally, BI6727 suppressed cellular proliferation and induced apoptosis in BL cell lines. BI6727 treatment also decreased C-MYC protein and mRNA expression, blocked the PI3K/AKT/mTOR signaling pathway, and stabilized the FBXW7 protein.ConclusionsOur findings explained a potential molecular mechanism of BI6727 in BL cells and suggested that BI6727 might be a new therapeutic agent for BL in the future.

Histone deacetylase inhibition enhances the therapeutic effects of methotrexate on primary central nervous system lymphoma.

BackgroundPolyglutamylation is a reversible protein modification that commonly occurs in tumor cells. Methotrexate (MTX) in tumor cells is polyglutamylated and strongly binds to dihydrofolate reductase (DHFR) without competitive inhibition by leucovorin. Therefore, tumor cells with high polyglutamylation levels are supposed to be selectively killed, whereas normal cells with lower polyglutamylation are rescued by leucovorin. This study investigated the combined effects of MTX plus histone deacetylase inhibitors (HDACIs), which upregulate MTX polyglutamylation, in primary central nervous system lymphoma (PCNSL).MethodsWe evaluated cell viability after MTX treatment and leucovorin rescue and compared the expression of folylpolyglutamate synthetase (FPGS), γ-glutamyl hydrolase (GGH), and DHFR in 2 human PCNSL-derived cell lines (HKBML and TK) and a human Burkitt lymphoma cell line (TL-1). Combination treatments were created using 4 HDACIs: panobinostat, vorinostat, sodium butyrate, and valproic acid. The expression of DHFR was examined as well as ratios of FPGS/GGH expression. The combined effects of MTX plus HDACIs were evaluated using a cell viability assay, mass spectroscopy imaging, and subcutaneous and intracranial xenograft models.ResultsHDACIs upregulated the ratio of FPGS/GGH expression resulting in increased polyglutamylation of MTX, but also downregulated expression of the target molecule of MTX: DHFR. The combination of MTX and vorinostat decreased cell viability in vitro (P < .05) and tumor volumes in a subcutaneous model (P < .0001), and prolonged survival in an intracranial model (P < .01), relative to controls.ConclusionHDACIs enhanced the therapeutic effect of MTX through increased polyglutamylation of MTX and concomitant downregulation of DHFR expression.

GCN5 HAT inhibition reduces human Burkitt lymphoma cell survival through reduction of MYC target gene expression and impeding BCR signaling pathways.

GCN5, the catalytic subunit in the acetyltransferase modules of SAGA and ATAC, functions as a coactivator of gene transcription. The SAGA complex is recruited to chromatin by transcription factors such as MYC and E2F1 to facilitate acetylation of histones, especially H3 at lysine 9 (H3K9). Burkitt lymphoma is an aggressive subtype of Non-Hodgkin lymphoma driven by the overexpression of MYC. Comparison of GCN5 expression in normal human B cells versus human Burkitt Lymphoma cell lines indicates overexpression of GCN5 in lymphoma. Treatment of Burkitt lymphoma cell lines with a specific inhibitor indicates that decreased GCN5 HAT activity reduces viability and proliferation of these cells. Inhibition of GCN5 HAT activity also induces apoptosis in lymphoma cells. Expression of MYC target genes as well as genes associated with B cell receptor signaling are significantly downregulated upon inhibition of GCN5 enzymatic activity. This downregulation leads to diminished PI3K signaling, a critical pathway in lymphomagenesis. Our data indicate that inhibition of GCN5 HAT activity reduces the tumorigenic properties of human Burkitt lymphoma cells by attenuating BCR signaling and that GCN5 may be a viable target for lymphoma drug therapy.

Effect of Baicalin Derivative 02-036 on Burkitt Lymphoma Cell Line CA46 and Its Related Mechanisms

To investigate the effect of baicalin derivative 02-036 on proliferation and apoptosis human Burkitt lymphoma cell line CA46 and its related mechanisms. The MTT assay and cell colony formation assay were used to measure the growth inhibition of CA46 cells after 02-036 treatment. The flow cytometry with AnnexinV-FITC/PI double staining was employed to detect the apoptosis induction effect of 02-036 on CA46 cells. Cell cycle distribution of CA46 cells was estimeted by using DNA ploid analysis. Western blot was used to determine the changes of apoptosis-related proteins, including C-MYC, BCL-2, Procaspase-9, Procaspase-3, PARP and Cleaved-PARP. Baicalin derivative 02-036 obviously inhibited the proliferation of CA46 cells, with dose- and time-dependent manner (r=0.963, r=0.992). The averaged IC50 value of CA46 cells was (6.04±0.11) μmol/L after 48-hour treatment. Low concentration of 02-036 could significantly inhibit the colony formation of CA46 cells. Flow cytometry analysis confirmed that 02-036 could effectively induce CA46 cell apoptosis. The apoptosis rate correlated with drug concentrations (r=0.959). Also, DNA ploid analysis showed that the cell cycle of CA46 was arrested in the S phase. The expression levels of BCL-2, Pro-caspase-9, Pro-caspase-3, PARP and C-MYC proteins decreased with a 02-036-dose dependent manner (r values were -0.990, -0.939, -0.971 and -0.967, respectively). In contrast, the expression level of cleaved-PARP increased with the same manner (r=0.920). Baicalin derivative 02-036 can effectively inhibit the proliferation and induce apoptosis of CA46 cells, and its related mechanisms may be correlated with the down-regulation of apoptosis-related molecule expression levels, such as BCL-2, Pro-caspase-9, Pro-caspase-3, PARP and C-MYC.

FOXO1 Confers Maintenance of the Dark Zone Proliferation and Survival Program and Can Be Pharmacologically Targeted in Burkitt Lymphoma.

The FOXO1 transcription factor plays a central role in the proliferation and survival of B cells at several stages of differentiation. B cell malignancies, with exception of classical Hodgkin lymphoma, maintain expression of FOXO1 at levels characteristic for their non-malignant counterparts. Extensive expression profiling had revealed that Burkitt lymphoma (BL) show many characteristics of the dark zone (DZ) germinal center (GC) B cell program. Here we show that FOXO1 knockdown inhibits proliferation of human BL cell lines. The anti-proliferative effect of the FOXO1 knockdown is associated with the repression of the DZ B cell program including expression of MYB, CCND3, RAG2, BACH2, and CXCR4. In addition, the induction of signaling pathways of the light zone (LZ) program like NF-κB and PI3K-AKT was observed. Using a rescue experiment we identified downregulation of the proto-oncogene MYB as a critical factor contributing to the antiproliferative effect of FOXO1 knockdown. In an attempt to estimate the feasibility of pharmacological FOXO1 repression, we found that the small molecular weight FOXO1 inhibitor AS1842856 induces cell death and growth arrest in BL cell lines at low concentrations. Interestingly, we found that overactivation of FOXO1 also induces growth inhibition in BL cell lines, indicating the importance of a tight regulation of FOXO1 activity in BL.

CD38-Specific Biparatopic Heavy Chain Antibodies Display Potent Complement-Dependent Cytotoxicity Against Multiple Myeloma Cells.

CD38 is overexpressed by multiple myeloma cells and has emerged as a target for therapeutic antibodies. Nanobodies are soluble single domain antibody fragments derived from the VHH variable domain of heavy chain antibodies naturally occurring in camelids. We previously identified distinct llama nanobodies that recognize three non-overlapping epitopes of the extracellular domain of CD38. Here, we fused these VHH domains to the hinge, CH2, and CH3 domains of human IgG1, yielding highly soluble chimeric llama/human heavy chain antibodies (hcAbs). We analyzed the capacity of these hcAbs to mediate complement-dependent cytotoxicity (CDC) to CD38-expressing human multiple myeloma and Burkitt lymphoma cell lines. Combinations of two hcAbs that recognize distinct, non-overlapping epitopes of CD38 mediated potent CDC, in contrast to the hcAb monotherapy with only weak CDC capacity. Similarly, combining daratumumab with a hcAb that recognizes a non-overlapping epitope resulted in dramatically enhanced CDC. Further, introducing the E345R HexaBody mutation into the CH3 domain strongly enhanced the CDC potency of hcAbs to CD38-expressing cells. Exploiting their high solubility, we genetically fused two distinct nanobodies into heteromeric dimers via a flexible peptide linker and then fused these nanobody dimers to the hinge, CH2 and CH3 domains of human IgG1, yielding highly soluble, biparatopic hcAbs. These biparatopic hcAbs elicited CDC toward CD38-expressing myeloma cells more effectively than daratumumab. Our results underscore the advantage of nanobodies vs. pairs of VH and VL domains for constructing bispecific antibodies. Moreover, the CD38-specific biparatopic heavy chain antibodies described here represent potential new powerful therapeutics for treatment of multiple myeloma.

Continuous signaling of CD79b and CD19 is required for the fitness of Burkitt lymphoma B cells

Expression of the B‐cell antigen receptor (BCR) is essential not only for the development but also for the maintenance of mature B cells. Similarly, many B‐cell lymphomas, including Burkitt lymphoma (BL), require continuous BCR signaling for their tumor growth. This growth is driven by immunoreceptor tyrosine‐based activation motif (ITAM) and PI3 kinase (PI3K) signaling. Here, we employ CRISPR/Cas9 to delete BCR and B‐cell co‐receptor genes in the human BL cell line Ramos. We find that Ramos B cells require the expression of the BCR signaling component Igβ (CD79b), and the co‐receptor CD19, for their fitness and competitive growth in culture. Furthermore, we show that in the absence of any other BCR component, Igβ can be expressed on the B‐cell surface, where it is found in close proximity to CD19 and signals in an ITAM‐dependent manner. These data suggest that Igβ and CD19 are part of an alternative B‐cell signaling module that use continuous ITAM/PI3K signaling to promote the survival of B lymphoma and normal B cells.

Effect of mitochondrially targeted carboxy proxyl nitroxide on Akt-mediated survival in Daudi cells: Significance of a dual mode of action.

Vicious cycles of mutations and reactive oxygen species (ROS) generation contribute to cancer progression. The use of antioxidants to inhibit ROS generation promotes cytostasis by affecting the mutation cycle and ROS-dependent survival signaling. However, cancer cells select mutations to elevate ROS albeit maintaining mitochondrial hyperpolarization (Δψm), even under hypoxia. From this perspective, the use of drugs that disrupt both ROS generation and Δψm is a viable anticancer strategy. Hence, we studied the effects of mitochondrially targeted carboxy proxyl nitroxide (Mito-CP) and a control ten carbon TPP moiety (Dec-TPP+) in the human Burkitt lymphoma cell line (Daudi) and normal peripheral blood mononuclear cells under hypoxia and normoxia. We found preferential localization, Δψm and adenosine triphosphate loss, and significant cytotoxicity by Mito-CP in Daudi cells alone. Interestingly, ROS levels were decreased and maintained in hypoxic and normoxic cancer cells, respectively, by Mito-CP but not Dec-TPP+, therefore preventing any adaptive signaling. Moreover, dual effects on mitochondrial bioenergetics and ROS by Mito-CP curtailed the cancer survival via Akt inhibition, AMPK-HIF-1α activation and promoted apoptosis via increased BCL2-associated X protein and poly (ADP-ribose) polymerase expression. This dual mode of action by Mito-CP provides a better explanation of the application of antioxidants with specific relevance to cancerous transformation and adaptations in the Daudi cell line.

Antibody-Interferon-Alpha Fusion Protein Therapy for the Treatment of B-Cell Non-Hodgkin Lymphoma: Enhanced ADCC, Inhibition of Proliferation, and In Vivo Eradication of CD20+ Human Lymphomas

Background: Interferon-alpha (IFNα) is a pleiotrophic cytokine with direct anti-tumor and immunostimulatory effects. Currently IFNα is approved for the treatment of multiple hematologic malignancies, including non-Hodgkin lymphoma (NHL). However, its clinical utility has been hindered by dose-limiting toxicitiy due to systemic activation of the interferon receptor. To overcome this limitation, we engineered anti-tumor antibody-IFNα fusion proteins to selectively increase delivery of IFN to the tumor site and reduce systemic toxicity. We previously reported that IGN002, an anti-CD20-IFNα fusion protein, exhibits enhanced complement-dependent cytotoxicity (CDC) compared to rituximab, and inhibits proliferation and induces apoptosis of human B-cell NHL (Yamada et al, ASCO 2013). We now extend these previous findings and show that IGN002 possesses enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) effector function and superior in vivo anti-tumor activity against B-cell NHL, compared to rituximab.Methods: IGN002 was evaluated against a panel of human Burkitt and diffuse large B-cell lymphoma (DLBCL) cell lines. Proliferation was measured by [3 H]-thymidine incorporation, STAT1 activation by flow cytometry, ADCC by lactate dehydrogenase release using human PBMC effectors, and IFN bioactivity by encephalomyocarditis (EMC) viral protection assay. NHL xenografts were grown in SCID mice.Results: IGN002 more potently inhibited the growth of NHL cell lines expressing CD20 than rituximab or unfused IFNα. Intrinsic IFNα activity of IGN002 was reduced in viral protection and anti-proliferation assays using cells lacking CD20 expression. STAT1 activation by IGN002 was enhanced on cells expressing the target antigen, whereas a control antibody-IFNα fusion protein showed reduced STAT activation activity compared to unfused IFNα. Together, these results indicate that fusion of IFNα to the antibody results in reduced IFN effects on cells not bearing the tumor antigen target. IGN002 exhibited enhanced ADCC activity compared to rituximab against Daudi, Ramos, and Raji NHL cells in long-term (overnight incubation) assays, demonstrating both higher potency and higher maximal cytotoxicity. This result is possibly due to activation of the effector cell populations by the fused IFNα moiety, as IFN is known to activate both NK cells and monocytes. The in vivo anti-tumor efficacy of IGN002 was compared to rituximab and a control antibody-IFNα fusion protein against 10-day established Raji NHL xenografts. IGN002 was superior to both rituximab and the control fusion protein, achieving a longer median survival and higher long-term survival rate (p = 0.0015 and < 0.0001 vs. rituximab and control fusion protein, respectively). The in vivo anti-tumor efficacy of IGN002 was also compared to rituximab at three equimolar dose levels (5 mg/kg, 1 mg/kg, and 0.2 mg/kg antibody) against 10-day established Daudi NHL xenografts. IGN002 showed superior efficacy compared to rituximab at all doses (p < 0.001), achieving tumor eradication (100% long-term survival) in all mice treated at all three dose levels, whereas rituximab only delayed tumor progression.Conclusions: IGN002 demonstrated more robust direct anti-proliferative and antibody effector functions than rituximab against human NHL cells in vitro, and also showed the ability to eradicate established NHL xenografts in vivo. Against cells expressing the CD20 target antigen, IGN002 exhibited greater anti-proliferative potency than unfused IFNα. In contrast, the anti-proliferative and anti-viral potency of IGN002 was reduced against cells lacking CD20, compared to unfused IFNα. These findings support the hypothesis that tumor antigen-targeted IFN therapeutics may possess a broader therapeutic index than unfused IFNα, inhibiting tumor growth by multiple mechanisms while reducing systemic toxicity. These results support the further development of IGN002 for the treatment of B-cell NHL, and a first-in-human phase I clinical study will begin later this year in the United States. DisclosuresTimmerman:Janssen: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Valor Biotherapeutics: Research Funding. Steward:ImmunGene, Inc.: Employment. Minning:Valor Biotherapeutics, LLC: Consultancy. Sachdev:ImmunGene, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Gresser:ImmunGene, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Valor Biotherapeutics: Membership on an entity's Board of Directors or advisory committees. Khare:Valor Biotherapeutics: Membership on an entity's Board of Directors or advisory committees; ImmunGene, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Morrison:ImmunGene, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Dimeric peroxiredoxins are druggable targets in human Burkitt lymphoma.

Burkitt lymphoma is a fast-growing tumor derived from germinal center B cells. It is mainly treated with aggressive chemotherapy, therefore novel therapeutic approaches are needed due to treatment toxicity and developing resistance. Disturbance of red-ox homeostasis has recently emerged as an efficient antitumor strategy. Peroxiredoxins (PRDXs) are thioredoxin-family antioxidant enzymes that scavenge cellular peroxides and contribute to red-ox homeostasis. PRDXs are robustly expressed in various malignancies and critically involved in cell proliferation, differentiation and apoptosis. To elucidate potential role of PRDXs in lymphoma, we studied their expression level in B cell-derived primary lymphoma cells as well as in cell lines. We found that PRDX1 and PRDX2 are upregulated in tumor B cells as compared with normal counterparts. Concomitant knockdown of PRDX1 and PRDX2 significantly attenuated the growth rate of lymphoma cells. Furthermore, in human Burkitt lymphoma cell lines, we isolated dimeric 2-cysteine peroxiredoxins as targets for SK053, a novel thiol-specific small-molecule peptidomimetic with antitumor activity. We observed that treatment of lymphoma cells with SK053 triggers formation of covalent PRDX dimers, accumulation of intracellular reactive oxygen species, phosphorylation of ERK1/2 and AKT and leads to cell cycle arrest and apoptosis. Based on site-directed mutagenesis and modeling studies, we propose a mechanism of SK053-mediated PRDX crosslinking, involving double thioalkylation of active site cysteine residues. Altogether, our results suggest that peroxiredoxins are novel therapeutic targets in Burkitt lymphoma and provide the basis for new approaches to the treatment of this disease.

Efficacy of an Anti-transferrin Receptor 1 Antibody Against AIDS-related Non-Hodgkin Lymphoma: A Brief Communication.

The transferrin receptor 1 (TfR1), also known as CD71, is a target for antibody-based cancer immunotherapy due to its high expression on the surface of cancer cells and its ability to internalize. We have previously developed a mouse/human chimeric IgG3 specific for human TfR1 genetically fused to avidin, as a vector to deliver biotinylated anticancer agents into malignant cells. However, we found that this fusion protein (ch128.1Av), and to a lesser extent the same antibody without avidin (ch128.1), exhibits direct cytotoxic activity in vitro against certain malignant hematopoietic cells through the induction of TfR1 degradation and lethal iron starvation. Importantly, both ch128.1 and ch128.1Av have also shown significant anticancer activity in 2 xenograft models of the B-cell malignancy multiple myeloma. It is interesting to note that ch128.1 exhibited superior anticancer activity in both models compared with ch128.1Av, even against malignant cells that show no sensitivity to ch128.1 in vitro. In the present study, we evaluated the efficacy of ch128.1 against an AIDS-related human Burkitt lymphoma cell line (2F7) to determine if ch128.1 can eliminate these cells in vitro and in an in vivo model of AIDS-related non-Hodgkin lymphoma (AIDS-NHL). Even though 2F7 cells expressed high TfR1 levels, these cells lacked sensitivity to the cytotoxicity induced by ch128.1 in vitro. However, ch128.1 showed significant anticancer activity against these AIDS-NHL cells in vivo by significantly prolonging the survival of immunodeficient mice bearing 2F7 tumors. Therefore, ch128.1 warrants further study as a candidate for the treatment of AIDS-NHL and other B-cell malignancies.

The dual PI3K/mTOR inhibitor NVP-BEZ235 inhibits proliferation and induces apoptosis of burkitt lymphoma cells.

BackgroundPhosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is a therapy target of cancer. We aimed to confirm the effect of dual PI3K/mTOR inhibitor NVP-BEZ235 on cell proliferation and apoptosis in Burkitt lymphoma (BL) cells.MethodsTwo human BL cell lines, CA46 and RAJI were used in this study. The proliferation of BL cells was detected by manganese tricarbonyl transfer (MTT) assay. Cell cycle and apoptosis assay were examined by flow cytometric analysis. The phosphorylation levels of AKT (Thr308), AKT (Ser473), and RPS6 were evaluated by western blot analysis.ResultsNVP-BEZ235 significantly inhibited the proliferation of BL cells (CA46 and RAJI) and the inhibition effect was time and dose-dependent. Cell cycle analysis indicated that the cells (CA46 and RAJI) were mostly arrested in G1/G0 phase. Cell apoptosis assay showed that the late apoptotic cells were significantly increased after 72 h treatment by 100 nmol/L of NVP-BEZ235. In addition, results also found that NVP-BEZ235 reduced the phosphorylation levels of AKT (Thr308), AKT (Ser473), and PRS6 in BL cells (CA46 and RAJI). Moreover, this inhibition effect on phosphorylation was dose-dependent.ConclusionsNVP-BEZ235 effectively inhibited cell proliferation by G0/G1 cell-cycle arrest and induced apoptosis through deregulating PI3K/Akt/mTOR pathway in BL cells.

An inducible lentiviral guide RNA platform enables the identification of tumor-essential genes and tumor-promoting mutations invivo.

The CRISPR/Cas9 technology enables the introduction of genomic alterations into almost any organism; however, systems for efficient and inducible gene modification have been lacking, especially for deletion of essential genes. Here, we describe a drug-inducible small guide RNA (sgRNA) vector system allowing for ubiquitous and efficient gene deletion in murine and human cells. This system mediates the efficient, temporally controlled deletion of MCL-1, both invitro and invivo, in human Burkitt lymphoma cell lines that require this anti-apoptotic BCL-2 protein for sustained survival and growth. Unexpectedly, repeated induction of the same sgRNA generated similar inactivating mutations in the human Mcl-1 gene due to low mutation variability exerted by the accompanying non-homologous end-joining (NHEJ) process. Finally, we were able to generate hematopoietic cell compartment-restricted Trp53-knockout mice, leading to the identification of cancer-promoting mutants of this critical tumor suppressor.