Killing Of Lymphoma Cells Research Articles

Silencing GNAS enhances HDAC3i efficacy in CREBBP wild type B cell lymphoma.

The genetic era has opened the opportunity of using personalized therapeutic approaches, in part based on targeting genes with somatic mutations. For example, lymphomas harboring the highly recurrent CREBBP mutation show dependency on HDAC3, thus selective inhibition of HDAC3 reversed the epigenetic effects of CREBBP mutation, halted lymphoma growth, and induced MHC class II expression, enabling the T-cells to recognize and kill lymphoma cells. However, CREBBP wild type (WT) cells are less sensitive to this approach. In this issue of Leukemia, He et al. have executed a genome-wide CRISPR screening that identified GNAS as a target to maximize the therapeutic activity of HDAC3 inhibition in CREBBP WT lymphoma.

High yield killing of lymphoma cells by anti-CD22 CAR-NK cell therapy.

Chimeric antigen receptors (CARs) offer a promising new approach for targeting B cell malignancies through the immune system. Despite the proven effectiveness of CAR T cells targeting CD19 and CD22 in hematological malignancies, it is imperative to note that their production remains a highly complex process. Unlike T cells, NK cells eliminate targets in a non-antigen-specific manner while avoiding graft vs. host disease (GvHD). CAR-NK cells are considered safer than CAR-T cells because they have a shorter lifespan and produce less toxic cytokines. Due to their unlimited ability to proliferate in vitro, NK-92 cells can be used as a source for CAR-engineered NK cells. We found that CARs created from the m971 anti-CD22 mAb, which specifically targets a proximal CD22 epitope, were more effective at anti-leukemic activity compared to those made with other binding domains. To further enhance the anti-leukemic capacity of NK cells, we used lentiviral transduction to generate the m971-CD28-CD3ζ NK-92. CD22 is highly expressed in B cell lymphoma. To evaluate the potential of targeting CD22, Raji cells were selected as CD22-positive cells. Our study aimed to investigate CD22 as a potential target for CAR-NK-92 therapy in the treatment of B cell lymphoma. We first generated m971-CD28-CD3ζ NK-92 that expressed a CAR for binding CD22 in vitro. Flow cytometric analysis was used to evaluate the expression of CAR. The 7AAD determined the cytotoxicity of the m971-CD28-CD3ζ NK-92 towards target lymphoma cell lines by flow cytometry assay. The ELISA assay evaluated cytokine production in CAR NK-92 cells in response to target cells. The m971-CD28-CD3ζ NK-92 cells have successfully expressed the CD22-specific CAR. m971-CD28-CD3ζ NK-92 cells efficiently lysed CD22-expressing lymphoma cell lines and produced large amounts of cytokines such as IFN-γ and GM-CSF but a lower level of IL-6 after coculturing with target cells. Based on our results, it is evident that transferring m971-CD28-CD3ζ NK-92 cells could be a promising immunotherapy for B cell lymphoma.

Abstract 3841: Tumor-derived microRNA125a induces CART cell apoptosis and failure in B cell malignancies

Abstract Despite the remarkable efficacy of chimeric antigen receptor T -cell therapy (CART) for the treatment of B-cell malignancies, durable remission remains limited often due to tumor relapse. We have previously demonstrated that tumor-derived extracellular vesicles (EVs) induced CART cell failure in preclinical models. To characterize the impact of tumor EV induced CART cell dysfunction, we assessed microRNA (miRNA) profiles contained within tumor EVs from two independent patient cohorts and studied how they contributed to CART dysfunction. Our first cohort included patients with chronic lymphocytic leukemia (n=50). We previously showed that CLL patient derived EVs induce a state of CART cell dysfunction. To understand this dysfunction, we interrogated the miRNA cargo significantly enriched in CLL EVs and how their coculture impacts CART signaling by RNAseq. Here, we found a significant enrichment in miR-125a within CLL EVs as compared to healthy donor controls (p=.0001). CART cocultured with CLL EVs showed alterations in T cell activation pathways, where miR-125a targets TNFAIP3 and NFkB pathways were activated. These findings implicate miR-125a from CLL EVs in CART dysfunction. Next, we aimed to validate the impact of miRNA on CART cell outcomes in the clinic. We interrogated miRNA profiles from patients with diffuse large B cell lymphoma (DLBCL) treated with CART cell therapy (CART19-28ζ, axicabtagene ciloleucel). EV miRNA cargo was compared between responders (complete remission at 6 months, n=10) and non-responders (no response 1 month post CART19, n=10) to identify differentially enriched miRNAs across groups. miR-125a was again significantly upregulated in EVs of non-responders as compared to responders to CART19 treatment (fold change=3.28, padj=.018). To study the direct effect of miR-125a on CART cell functions, we generated and studied the effector functions of CART19-28z following transfection with miR-125a or negative miR control. CART19 cells transfected with miR-125a showed a dose dependent decrease in killing of lymphoma cells as compared to miR-control (p=.0001). miR-125a also significantly increased the rate of apoptosis in CART19 cells (fold change=1.95, p=.024) and decreased the level of CART proliferation (fold change=.71, p=.013) as compared to controls. Notably, miR-125a did not impact tumor cell growth, further verifying a direct CART effect. In summary, our studies demonstrate the impact of tumor derived miRNAs on CART cell outcomes. They identify that miR-125a is 1) associated with CLL EV induced CART dysfunction, 2) significantly elevated in non-responders to CART therapy in the clinic, and 3) able to decrease CART19 efficacy through reduced CART killing/proliferation and increased apoptosis. These results highlight a novel mechanism of CART19 failure induced through miRNA cargo delivery by tumor-derived EVs and the role of miR-125a in inducing CART19 dysfunction. Citation Format: Olivia Sirpilla, R. Leo Sakemura, Ismail Can, Truc N. Huynh, James H. GIrsch, Claudia Manriquez Roman, Carli M. Stewart, Kun Yun, Ekene J. Ogbodo, Long Mai, Omar Gutierrez Ruiz, Makena Rodriguez, Brooke Kimball, Hong Xia, Jose C. Villasboas, Stephen Ansell, Nora Bennani, Patrick B. Johnston, Jonas Paludo, Januario Castro, Mohamed Kharfandabaja, Sameer Parikh, Neil Kay, Yi Lin, Elizabeth Siegler, Saad Kenderian. Tumor-derived microRNA125a induces CART cell apoptosis and failure in B cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3841.

Abstract 3732: Peripheral pharmacodynamic activity of epcoritamab as monotherapy and in combination with rituximab + lenalidomide in patients with follicular lymphoma

Abstract Introduction: Epcoritamab (DuoBody®-CD3xCD20) is a subcutaneous IgG1 bispecific antibody that simultaneously binds to CD3 on T cells and CD20 on malignant B cells, inducing activation and cytotoxic activity of T cells to mediate killing of target lymphoma cells. Epcoritamab is approved in the US for the treatment of adults with relapsed/refractory (R/R) diffuse and high-grade large B-cell lymphoma after ≥2 lines of systemic therapy (also approved in Europe, the UK, Japan, and Canada). Here we present the pharmacodynamic effects of epcoritamab as monotherapy (EPCORE NHL-1: NCT03625037) or in combination with rituximab + lenalidomide (R2) (EPCORE NHL-2: NCT04663347) in peripheral blood of patients with follicular lymphoma (FL), a heterogeneous disease for which many patients have an unmet medical need for efficacious, well-tolerated, off-the-shelf therapies. Methods: In EPCORE NHL-1 expansion phase, adults with R/R FL received epcoritamab monotherapy; in EPCORE NHL-2, adults with R/R (arm 2) or newly diagnosed (ND) (arm 6) FL received epcoritamab combined with R2. B-cell markers and T-cell proliferation and activation markers in whole blood were assessed using validated flow cytometry assays. Cytokines in plasma were measured using a validated multiplex immunoassay. Results: Epcoritamab as monotherapy and in combination with R2 induced rapid depletion of circulating peripheral B cells (CD19+) in patients with detectable peripheral B cells at baseline. Additionally, within the first 2 cycles, epcoritamab monotherapy induced a transient elevation of peripheral CD8+ and CD4+ T cells expressing proliferation (Ki67+%) and activation (HLA-DR+% and PD-1+%) markers. R/R and ND patient groups treated with epcoritamab + R2 showed a trend for greater induction of proliferating and activated peripheral T cells. Likewise, elevation in T-cell absolute counts was observed from cycle 2 onward, with a trend of higher levels with epcoritamab + R2 vs epcoritamab monotherapy. In addition, a moderate but transient elevation of circulating cytokines including IFNγ, IL-6, and IL-10 during cycle 1 was observed with epcoritamab monotherapy and epcoritamab + R2. Importantly, IL-6 and IL-10 returned to approximate baseline levels prior to the subsequent dose. Compared with epcoritamab monotherapy, patients treated with epcoritamab + R2 showed a trend for lower median levels of IL-6 peaks 24 hours after the first full dose. Conclusion: The pharmacodynamic activity of epcoritamab combined with R2 in R/R and ND FL was consistent with epcoritamab’s mechanism of action as monotherapy. Epcoritamab + R2 showed a favorable pharmacodynamic profile with a trend toward increased T-cell activation and T-cell elevation, and lower IL-6 levels. These data support the ongoing phase 3 trial of epcoritamab + R2 compared with R2 alone in patients with R/R FL (EPCORE FL-1: NCT05409066). Citation Format: Han Si, Jimin Zhang, Monica Wielgos-Bonvallet, Lorenzo Falchi, Kim Linton, Wojciech Jurczak, David Belada, Işıl Altıntaş, Mariana Sacchi, Elena Favaro, Ali Rana, Daniela Hoehn, David Soong, Christopher W. Chiu, Maria Jure-Kunkel. Peripheral pharmacodynamic activity of epcoritamab as monotherapy and in combination with rituximab + lenalidomide in patients with follicular lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3732.

Derepressing of STAT3 and USP7 contributes to resistance of DLBCL to EZH2 inhibition

Diffuse large B-cell lymphoma is the most common subtype of lymphoma, representing ∼25 % of non-Hodgkin lymphoid malignancies. EZH2 is highly expressed in Diffuse large B-cell lymphoma and ∼22 % of patients contain EZH2 mutations. EZH2 have been studied as a potential therapeutic target for a decade, but efficient inhibition of EZH2 did not robustly kill lymphoma cells. Here, we found that EZH2 mediates repression of oncogenic genes STAT3 and USP7 in Diffuse large B-cell lymphoma cells. Inhibition of EZH2 leads to upregulation of STAT3 and USP7 at both RNA and protein levels. Along with USP7 upregulation, MDM2 is upregulated and its ubiquitylation substrate, Tumor suppressor P53, is downregulated. Upregulation of STAT3 and downregulation of p53 can strength cell proliferation and prevent cells from apoptosis, which suggests resistance mechanisms by which cells survive EZH2 inhibition-induced cell death. Short-course co-inhibition of USP7 and EZH2 showed increased apoptosis and cell proliferation prevention with the concentration as low as 0.08 μM. In STAT3 and USP7 depleted cells, EZH2 inhibition shows superior efficacy of apoptosis, and in EZH2 depleted cells, USP7 inhibition also shows superior efficacy of apoptosis. Thus, our findings suggest a new precision therapy by combinational inhibition of EZH2 with STAT3 or USP7 for Diffuse large B-cell lymphoma.

GPCR signaling contributes to immune characteristics of microenvironment and process of EBV-induced lymphomagenesis

Epstein-Barr virus (EBV) is the oncogenic driver of multiple cancers. However, the underlying mechanism of virus-cancer immunological interaction during disease pathogenesis remains largely elusive. Here we reported the first comprehensive proteogenomic characterization of natural killer/T-cell lymphoma (NKTCL), a representative disease model to study EBV-induced lymphomagenesis, incorporating genomic, transcriptomic, and in-depth proteomic data. Our multi-omics analysis of NKTCL revealed that EBV gene pattern correlated with immune-related oncogenic signaling. Single-cell transcriptome further delineated the tumor microenvironment as immune-inflamed, -deficient, and -desert phenotypes, in association with different setpoints of cancer-immunity cycle. EBV interacted with transcriptional factors to provoke GPCR interactome (GPCRome) reprogramming. Enhanced expression of chemokine receptor-1 (CCR1) on malignant and immunosuppressive cells modulated virus-cancer interaction on microenvironment. Therapeutic targeting CCR1 showed promising efficacy with EBV eradication, T-cell activation, and lymphoma cell killing in NKTCL organoid. Collectively, our study identified a previously unknown GPCR-mediated malignant progression and translated sensors of viral molecules into EBV-specific anti-cancer therapeutics.

PROTEOMIC PROFILING IDENTIFIES GRANZYME B INHIBITOR SERPIN B9 AS MEDIATOR OF RESISTANCE TO CAR T‐CELL AND BISPECIFIC ANTIBODY TREATMENT IN NODAL B‐CELL LYMPHOMA

Introduction: Treatment options for relapsed or refractory (r/r) B-cell non-Hodgkin lymphomas (B-NHL) have broadened towards T-cell engaging therapies, including CD19-targeting chimeric antigen receptor T-cells (CD19-CAR) and bispecific antibodies (CD19-BsAb). Although CD19-CAR and CD19-BsAb induce durable responses in some r/r B-NHL patients, response remains heterogenous and a significant proportion of patients experience insufficient responses or relapse. A thorough understanding of tumor-intrinsic mechanisms of resistance is crucial for the clinical improvement of T-cell immunotherapy. Methods: Aiming to identify lymphoma cell-inherent mechanisms that impair response to T-cell engaging therapy, we quantified the in-vitro response of 46 B-NHL cell lines to 3rd generation CD19-CAR and CD19-BsAb. Response was measured using a high-throughput flow cytometry-based assay. In parallel, cell lines were subjected to proteomic profiling and protein abundance was regressed on in-vitro response in order to identify proteomic determinants of response. We further combined CD19-CAR treatment with clinically relevant drugs and assessed how killing of lymphoma cells and expansion of T-cells was altered. Results: Response to CD19-CAR and CD19-BsAb was highly heterogeneous across cell lines and B-NHL entities, but not significantly linked to their proliferation rate or CD19 expression. Integration of the proteomic profiles revealed that abundance of Serpin B9, endogenous inhibitor of T-cell effector molecule granzyme B, was associated with poor response to CD19-CAR and CD19-BsAb. This finding was validated in overexpression and knock-out models. Overexpression of SERPINB9 indeed attenuated response to CD19-CAR and CD19-BsAb, while its knock-out rendered cell lines more sensitive. The observed changes in susceptibility to T-cell-mediated cytotoxicity upon modulation of SERPINB9 expression were independent of T-cell donor and expression of T-cell activation and proliferation markers. We sought to improve T-cell-mediated cytotoxicity specifically in samples with high SERPINB9 expression and found that immune checkpoint inhibitors and lenalidomide enhanced expansion of CAR T-cells and increased killing of lymphoma cells. In addition, vorinostat and antibody-drug-conjugate polatuzumab vedotin specifically killed lymphoma cells without affecting T-cell expansion. However, the observed improvement in T-cell-mediated cytotoxicity was independent of SERPINB9 expression. Keywords: aggressive B-cell non-Hodgkin lymphoma, immunotherapy, indolent non-Hodgkin lymphoma No conflicts of interests pertinent to the abstract.

SAR442257, a CD38/CD28/CD3 trispecific antibody, potentiates CAR T‐cell activity against large B‐cell lymphoma

CART cell therapy has significantly improved outcomes of patients with relapsed/refractory large B cell lymphoma (rrLBCL), but many do not experience long term benefit. The mechanisms of failure are multifaceted including CAR T exhaustion. Understanding these mechanisms are likely to identify therapeutic avenues for improving outcomes. 13 rrLBCL tumors (7 CART naïve, 6 CART refractory), were subjected to scRNA-seq. Clustering was performed and frequency, clonal dominance, and expression of major cells and subclusters were compared. The effect of SAR442257, a CD38/CD28xCD3 trispecific antibody, was assessed in cytotoxicity assays and compared to control antibodies without CD38 or CD38/CD3/CD28 targeting regions. RL and HT cell lines were CRISPR modified to knock-out CD19 and isogenic WT used as target cells. CD19 CAR T were constructed from PBMCs of rrLBCL patients obtained at time of apheresis using a construct like axicabtagene ciloleucel. For cytotoxicity assays, cell lines were co-cultured at E:T ratios of 1:1 for 24 h or 48 h. scRNA-seq revealed that CART refractory rrLBCL tumors possessed higher fractions of terminally exhausted LAG3+TIM3+CD38+ CD8 T-cells (CD8TEX) with high expression of T-cell dysfunction and TEX signatures compared to CAR T naïve tumors. CD8TEX were most frequent in CART refractory tumors and enriched within CAR+CD8 T-cells detected. TCR clonotype analysis revealed highly expanded T-cell clones within the CD8TEX cluster, significantly increased clonal dominance, and reduced clonal diversity of CD8TEX cells in CAR T refractory compared to CART naïve tumors. Single cell differential gene expression revealed significantly increased expression of LAG3, TIM3, and CD38 in CD8 T-cells from CART refractory compared to CART naïve tumors. We hypothesized that SAR442257 could boost the activity of CD19 CART-cells from rrLBCL patients through dual antigen targeting of CD19 and CD38 on lymphoma cells and by fratricide of CD38-expressing CD8TEX cells. Cytotoxicity assays showed that SAR442257 significantly increased the killing of CAR T-cells against HT and RL WT (CD19+/CD38+) cells (24-h HT P-value = 3e-4, 24-h RL P-value = 1e-2) that persisted at 48 h. Addition of SAR442257 to CART-cells allowed killing of HT and RL CD19KO (CD19-/CD38+) (24-h HT P-value = 8e-7, 24-h RL P-value = 2e-8) at a level similar to the combination in WT. Addition of antibodies lacking CD38 or CD38/CD3/CD28-targeting regions did not boost cytotoxicity or rescue killing of CD19KO targets. We observed significant T-cell fratricide, which was beneficial or non-detrimental in light of increased lymphoma cell killing. The tumor microenvironment of CART refractory rrLBCL is enriched in clonally expanded and terminally exhausted CD8 T-cells expressing CD38. The CD38/CD28xCD3 trispecific antibody SAR442257 boosted CART-cell activity through recognition of CD38 on the tumor, costimulation of CART-cells, and induced fratricide of CD38+ T-cells. In addition, SAR442257 allowed CD19 CART-cells to kill CD19-/CD38+ LBCL cells. Encore Abstract - previously submitted to EHA 2023 The research was funded by: Sanofi Keywords: Aggressive B-cell non-Hodgkin lymphoma, Bioinformatics, Cellular therapies, Computational and Systems Biology Conflicts of interests pertinent to the abstract. P. Kim Employment or leadership position: Sanofi K. Bisht Employment or leadership position: Sanofi H. Van De Velde Employment or leadership position: Sanofi H. Wang Employment or leadership position: Sanofi

An Update on Recent Advances of Photodynamic Therapy for Primary Cutaneous Lymphomas.

Primary cutaneous lymphomas are rare non-Hodgkin lymphomas consisting of heterogeneous disease entities. Photodynamic therapy (PDT) utilizing photosensitizers irradiated with a specific wavelength of light in the presence of oxygen exerts promising anti-tumor effects on non-melanoma skin cancer, yet its application in primary cutaneous lymphomas remains less recognized. Despite many in vitro data showing PDT could effectively kill lymphoma cells, clinical evidence of PDT against primary cutaneous lymphomas is limited. Recently, a phase 3 "FLASH" randomized clinical trial demonstrated the efficacy of topical hypericin PDT for early-stage cutaneous T-cell lymphoma. An update on recent advances of photodynamic therapy in primary cutaneous lymphomas is provided.

Abstract 6208: Targeting DNA polymerase theta and ATM leads to synergistic killing of mantle cell lymphoma cells

Abstract Introduction: Rapid cell proliferation requires intact and faithful DNA damage repair mechanisms. DNA polymerase theta (POLQ) plays a key role in repairing DNA double-strand breaks through the microhomology-mediated end-joining (MMEJ), which is one of the three main pathways involved in repairing replication-induced double-strand breaks. Limited data have suggested that concurrent depletion of POLQ and ataxia-telangiectasia mutated (ATM) could be embryonic lethal. Hence, this phenomenon has the potential to be exploited for therapeutic benefit in cancers where ATM mutations are commonly seen. Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma marked by (11;14) translocation with ATM alterations seen in 40-50% of patients. There is an unmet need to find novel therapeutic strategies, especially in relapsed and/or refractory (R/R) MCL. Here, we investigated whether targeting POLQ and ATM could be a potential therapeutic strategy in MCL. Methods: In vitro studies were conducted by using MCL cell lines. CRISPR-Cas9 system was used to genetically deplete POLQ and ATM genes and sgRNAs co-expressing fluorescence markers were used to track the cell population with respective genotypes over time. Cell viability was assessed by CellTiter-Glo assay and flow cytometry. All cell lines were profiled for ATM expression and activity. A p-value of < 0.05 was considered statistically significant. The combination index of <1 was defined as synergistic. Results: CRISPR-Cas9-mediated depletion of POLQ significantly decreased cell proliferation in multiple MCL cell lines. In particular, Granta-519, which possesses a single copy of kinase-dead ATM that is reduced in expression, was most sensitive to POLQ depletion. Concurrent genetic depletion of ATM and POLQ resulted in a synergistic antiproliferative effect in ATM-proficient MCL cell lines. Subsequently, this cellular phenotype caused by the genetic intervention was recapitulated by using two POLQ inhibitors (novobiocin and ART558) and an ATM inhibitor (AZD0156). In vitro, single-agent treatment with novobiocin or ART558 caused a significant cytotoxic effect at physiologically relevant concentrations in ATM-deficient cells and co-treatment of novobiocin or ART558 with AZD0156 was synergistic in killing ATM-proficient MCL cells. Importantly, POLQ inhibitors significantly decreased the cell viability of MCIR1, which is an ibrutinib-resistant MCL cell line. Mechanistically, novobiocin or ART558 treatment induced gH2AX and cleaved PARP upregulation, which was further enhanced by ATM depletion, suggesting that co-inhibition of POLQ and ATM caused apoptosis due to the accumulation of unrepaired DNA damage. Conclusion: POLQ is a promising target in MCL, especially in ATM-deficient setting. In ATM-proficient MCL, targeting ATM and POLQ is synergistic. Our data has the potential to uncover novel biomarker-driven drug therapy of POLQ inhibitors in R/R MCL. Citation Format: Jithma Prasad Abeykoon, Shuhei Asada, Kalindi Parmar, Xiaosheng Wu, Thomas Witzig, Geoffrey Shapiro, Alan D. D'Andrea. Targeting DNA polymerase theta and ATM leads to synergistic killing of mantle cell lymphoma cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6208.

Mesenchymal stem cell suppresses the efficacy of CAR-T toward killing lymphoma cells by modulating the microenvironment through stanniocalcin-1.

Stem cells play critical roles both in the development of cancer and therapy resistance. Although mesenchymal stem cells (MSCs) can actively migrate to tumor sites, their impact on CAR-T immunotherapy has been little addressed. Using an in vitro cell co-culture model including lymphoma cells and macrophages, here we report that CAR-T cell-mediated cytotoxicity was significantly inhibited in the presence of MSCs. MSCs caused an increase of CD4+ T cells and Treg cells but a decrease of CD8+ T cells. In addition, MSCs stimulated the expression of indoleamine 2,3-dioxygenase (IDO) and programmed cell death-ligand 1 (PD-L1) which contributes to the immune-suppressive function of tumors. Moreover, MSCs suppressed key components of the NLRP3 inflammasome by modulating mitochondrial ROS release. Interestingly, all these suppressive events hindering CAR-T efficacy could be abrogated if the STC1 gene, which encodes the glycoprotein hormone staniocalcin-1, was knockdown in MSC. Using xenograft mice, we confirmed that CAR-T function could also be inhibited by MSC in vivo and STC1 played a critical role. These data revealed a novel function of MSC and staniocalcin-1 in suppressing CAR-T efficacy, which should be considered in cancer therapy and may also have potential applications in controlling the toxicity arising from the excessive immune response.

The Flavonoid Brusatol Induces Apoptosis in Aggressive Lymphoma Cells and Exhibits Synergistic Effect with Venetoclax

The most common lymphoid malignancies in adults are aggressive lymphomas, including Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL). Despite the available chemoimmunotherapy R-CHOP, one third of DLBCL patients still have primary refractory disease or relapse, and the incidence of these lymphomas continuously increases. Together, there is the great need for further development of new treatment strategies for aggressive lymphoma. One step forward seems to be Venetoclax (an FDA-approved Bcl-2 inhibitor), which showed an overall response rate of 44% in a phase 1 trial. Here, we evaluated a flavonoid - Brusatol, which showed anti-tumour activity in various preclinical cancer models, to improve anti-lymphoma therapies. We investigated the potential of Brusatol in the treatment of aggressive lymphoma cells as a single agent or in combination with other drugs, including Venetoclax. Seven cell lines representing different types of lymphoma (BL2, Raji (Burkitt lymphoma), SuDHL4, Karpas422 (GCB-DLBCL), RI-1, U2932 (ABC-DLBCL) and Jurkat (T-cell leukemia)) were treated with increasing concentrations of Brusatol (up to 10µM) for 72h to determine the IC50 values. Based on these results, 50nM and 250nM Brusatol were selected for further experiments. Cells were treated with Brusatol for 24h and 48h and apoptosis induction (Annexin V staining, Caspase-3- and PARP-cleavage) and changes in cell cycle (PI staining) were assessed. Moreover, samples from untreated and Brusatol-treated cells were collected for Western blot analysis. To investigate potential effects of Brusatol on protein synthesis in lymphoma cells, four cell lines (BL2, SuDHL4, RI-1 and U2932) were treated for 4h, and then the nascent protein synthesis was evaluated by detection of an incorporated methionine analogue using click-chemistry. Furthermore, co-treatment of Brusatol with inhibitors of Bcl-2 (Venetoclax), Bcl-XL (A-1331852), Mcl-1 (S63845), BTK (Ibrutinib), PI3K (Idealisib), Myc (EN4, JQ1), respectively, was performed in the same four cell lines and Annexin V levels were measured after 24h. Finally, the effect of combining Brusatol with Venetoclax was determined using the Bliss independence model for SuDHL4 and U2932 after 24h treatment via TMRE staining. In all investigated cell lines, Brusatol caused cell growth inhibition in a concentration-dependent manner. However, based on the results of the apoptosis assays, they could be grouped into cell lines more (BL2, Jurkat, Raji, SuDHL4) and less (Karpas422, RI-1, U2932) sensitive to Brusatol. Moreover, cell cycle analysis revealed an increase of cells in the sub-G1 phase in the more sensitive cell lines, indicating the induction of cell death. Western blot analysis of more sensitive cell lines showed decreased levels of the prosurvival proteins Bcl-2, Bcl-XL and Mcl-1. Additionally, we detected reduced p53 and Myc protein expression in cell lines more sensitive to Brusatol after 24h treatment. Notably, the protein expression profile of untreated cells indicates that cell lines with higher Myc levels are more sensitive to Brusatol treatment. Furthermore, mRNA expression analysis revealed that the reduction of affected proteins mainly occurred on protein level. Therefore, we investigated the effect of Brusatol on protein biosynthesis and observed protein translation inhibition in all tested cell lines. Interestingly, increased induction of apoptosis was apparent in all cell lines upon co-treatment with Brusatol and Bcl-XL inhibitor, in three of the four cell lines treated with the combination of Brusatol and Bcl-2 inhibitor, and in two cell lines when Brusatol was combined with Mcl-1 inhibitor. In contrast, combining Brusatol had no beneficial effect in combination with all other drugs tested. Finally, analysis of the Bliss independent model showed that the combination of Brusatol and Venetoclax synergistically enhanced the killing of lymphoma cells. Our data indicate that Brusatol efficiently induces cell death in aggressive lymphoma cells by reducing the expression of prosurvival proteins. Interestingly, cells with higher Myc levels were especially sensitive to Brusatol. Additionally, the combination of Brusatol with Venetoclax results in enhanced induction of apoptosis. Thus, our study suggests that Brusatol, alone or in combination with Venetoclax, represents a very interesting agent for further development of novel anti-lymphoma therapies.

Loss of Nr4a1 Causes an Elevated Expression of Co-Inhibitory Receptor:Ligand Axes and Results in a Diminished T Cell-Mediated Lymphoma Cell Killing in Aggressive Lymphoma

Loss of Nr4a1 Causes an Elevated Expression of Co-Inhibitory Receptor:Ligand Axes and Results in a Diminished T Cell-Mediated Lymphoma Cell Killing in Aggressive Lymphoma

Acute exercise mobilizes NKT-like cells with a cytotoxic transcriptomic profile but does not augment the potency of cytokine-induced killer (CIK) cells.

CD3+/CD56+ Natural killer (NK) cell-like T-cells (NKT-like cells) represent <5% of blood lymphocytes, display a cytotoxic phenotype, and can kill various cancers. NKT-like cells can be expanded ex vivo into cytokine-induced killer (CIK) cells, however this therapeutic cell product has had mixed results against hematological malignancies in clinical trials. The aim of this study was to determine if NKT-like cells mobilized during acute cycling exercise could be used to generate more potent anti-tumor CIK cells from healthy donors. An acute exercise bout increased NKT-like cell numbers in blood 2-fold. Single cell RNA sequencing revealed that exercise mobilized NKT-like cells have an upregulation of genes and transcriptomic programs associated with enhanced anti-tumor activity, including cytotoxicity, cytokine responsiveness, and migration. Exercise, however, did not augment the ex vivo expansion of CIK cells or alter their surface phenotypes after 21-days of culture. CIK cells expanded at rest, during exercise (at 60% and 80% VO2max) or after (1h post) were equally capable of killing leukemia, lymphoma, and multiple myeloma target cells with and without cytokine (IL-2) and antibody (OKT3) priming in vitro. We conclude that acute exercise in healthy donors mobilizes NKT-like cells with an upregulation of transcriptomic programs involved in anti-tumor activity, but does not augment the ex vivo expansion of CIK cells.

Cure of Micrometastatic B-Cell Lymphoma in a SCID Mouse Model Using 213Bi-Anti-CD20 Monoclonal Antibody.

We studied the feasibility of using the α-emitting 213Bi-anti-CD20 therapy with direct bioluminescent tracking of micrometastatic human B-cell lymphoma in a SCID mouse model. Methods: A highly lethal SCID mouse model of minimal-tumor-burden disseminated non-Hodgkin lymphoma (NHL) was established using human Raji lymphoma cells transfected to express the luciferase reporter. In vitro and invivo radioimmunotherapy experiments were conducted. Single- and multiple-dose regimens were explored, and results with 213Bi-rituximab were compared with various controls, including no treatment, free 213Bi radiometal, unlabeled rituximab, and 213Bi-labeled anti-HER2/neu (non-CD20-specific antibody). 213Bi-rituximab was also compared invivo with the low-energy β-emitter 131I-tositumomab and the high-energy β-emitter 90Y-rituximab. Results: In vitro studies showed dose-dependent target-specific killing of lymphoma cells with 213Bi-rituximab. Multiple invivo studies showed significant and specific tumor growth delays with 213Bi-rituximab versus free 213Bi, 213Bi-labeled control antibody, or unlabeled rituximab. Redosing of 213Bi-rituximab was more effective than single dosing. With a single dose of therapy given 4 d after intravenous tumor inoculation, disease in all untreated controls, and in all mice in the 925-kBq 90Y-rituximab group, progressed. With 3,700 kBq of 213Bi-rituximab, 75% of the mice survived and all but 1 survivor was cured. With 2,035 kBq of 131I-tositumomab, 75% of the mice were tumor-free by bioluminescent imaging and 62.5% survived. Conclusion: Cure of micrometastatic NHL is achieved in most animals treated 4 d after intravenous tumor inoculation using either 213Bi-rituximab or 131I-tositumomab, in contrast to the lack of cures with unlabeled rituximab or 90Y-rituximab or if there was a high tumor burden before radioimmunotherapy. α-emitter-labeled anti-CD20 antibodies are promising therapeutics for NHL, although a longer-lived α-emitter may be of greater efficacy.

Abstract 4179: High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing

Abstract Rituximab-containing treatment regimens are the standard of care for patients with non-Hodgkin’s lymphoma (NHL). However, the majority of patients ultimately experience disease relapse or progression indicating resistance to rituximab therapy. IGM-2323 is an engineered high-affinity, high-avidity anti-CD20 pentameric IgM antibody with an anti-CD3 scFv fused to the joining chain. IGM-2323 offers a novel treatment strategy in NHL through two mechanisms: 1) the recruitment of T cells to kill CD20-expressing tumor cells through T cell dependent cellular cytotoxicity (TDCC) and, 2) complement-dependent cytotoxicity (CDC). We evaluated the activity of IGM-2323 in the presence of rituximab since rituximab can persist in patients after treatment discontinuation, and it can bind to an overlapping epitope on CD20 as IGM-2323. We hypothesized that the high valency of IGM-2323 could displace rituximab, thus enabling potent B cell killing by IGM-2323 even in the presence of high concentrations of rituximab. The affinity of IGM-2323 and its corresponding bivalent anti-CD20 IgG antibody to recombinant human CD20 protein were measured by surface plasmon resonance. IGM-2323 bound to human CD20 with an apparent 300-fold higher binding affinity (KD) and ~100-fold slower off-rate (kdis) than the bivalent anti-CD20 IgG. Human B cell lines with a range of CD20 expression levels, including a CD20-low rituximab-resistant Ramos cell variant, were pre-treated with escalating concentrations of rituximab, and subsequently evaluated in vitro for cell binding, TDCC, and CDC by IGM-2323. At high concentrations of rituximab, which correspond to reported peak serum concentrations (Cmax) found in rituximab-treated patients, IGM-2323 displaced the binding of rituximab on human B cell lines. In contrast, binding of a bispecific CD20xCD3 IgG was severely inhibited by the Cmax of rituximab. In TDCC assays with healthy donor effector T cells, pre-treatment with high concentrations of rituximab only modestly inhibited IGM-2323 activity. Furthermore, only a minor impact to the maximum killing activity (Emax) of IGM-2323 was observed at the Cmax of rituximab. In contrast, rituximab pre-treatment resulted in a distinctly lower Emax of a bispecific CD20xCD3 IgG. Live cell imaging of CDC kinetics was utilized to quantify the extent of CDC by IGM-2323 with or without rituximab. Pre-treatment with rituximab enhanced CDC of IGM-2323 compared to single agent activity. Our preclinical data indicate that IGM-2323 maintains activity in the presence of rituximab. IGM-2323 is currently being studied in a phase 1 clinical trial in relapsed/refractory NHL, where it has been generally well tolerated, with both complete and partial responses observed (NCT04082936). Clinical studies will continue to evaluate these findings, including the treatment of patients with circulating serum levels of rituximab. Citation Format: Kevin C. Hart, Kathryn Logronio, Mandy Li, Poonam Yakkundi, Marigold Manlusoc, Keyu Li, Paul R. Hinton, Dean Ng, Maya K. Leabman, Genevive Hernandez, Thomas Manley, Angus M. Sinclair, Stephen F. Carroll, Bruce A. Keyt, Maya F. Kotturi. High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4179.

Elotuzumab, a potential therapeutic humanized anti-SLAMF7 monoclonal antibody, enhances natural killer cell-mediated killing of primary effusion lymphoma cells.

Primary effusion lymphoma (PEL) is a rare aggressive B-cell non-Hodgkin's lymphoma with no optimal treatment. Signaling lymphocytic activation molecule-F7 (SLAMF7, CD319), a type I transmembrane glycoprotein highly expressed in multiple myeloma (MM), represents a promising target for mAb-based immunotherapy. SLAMF7 also expresses on several hematopoietic lineages including NK cells. Elotuzumab (Elo), a humanized antibody targeting SLAMF7, is approved by FDA for MM treatment. In this study, we analyzed the expression of SLAMF7 on seven PEL cell lines. All PEL cells and NK cells showed high expression of SLAMF7. NK cells were enriched from PBMCs of healthy donors by MACS and expanded by co-culturing with MHC-class I negative K562 cells in the presence of IL-2 and IL-15. Expanded NK cells showed direct killing, and Elo demonstrated potent ADCC against PEL in an Effector:Target (E:T) dependent manner. Surface expression of CD107a on NK cells also increased in the process of ADCC. We also examined SLAMF7 expression of NK subpopulations and found that the CD56+CD16+ NK subpopulation demonstrated the highest SLAMF7 expression. Full-length-Elo but not F(ab')2-Elo exerts direct engagement to the expressing SLAMF7 on NK cells, promotes CD107a expression, and further augments NK cytotoxicity toward PEL. Elo enhanced survival of PEL-bearing immunodeficient mice with adoptive transfer of human NK cells. Taken together, our results show that NK cells play roles in PEL killing, and Elo causes ADCC/SLAMF7 ligation to boost NK cytotoxicity against PEL, offering promising preclinical evidence of Elo as a therapeutic monoclonal antibody treatment for PEL.

Sodium stibogluconate and CD47-SIRPα blockade overcome resistance of anti-CD20–opsonized B cells to neutrophil killing

AbstractAnti-CD20 antibodies such as rituximab are broadly used to treat B-cell malignancies. These antibodies can induce various effector functions, including immune cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Neutrophils can induce ADCC toward solid cancer cells by trogoptosis, a cytotoxic mechanism known to be dependent on trogocytosis. However, neutrophils seem to be incapable of killing rituximab-opsonized B-cell lymphoma cells. Nevertheless, neutrophils do trogocytose rituximab-opsonized B-cell lymphoma cells, but this only reduces CD20 surface expression and is thought to render tumor cells therapeutically resistant to further rituximab-dependent destruction. Here, we demonstrate that resistance of B-cell lymphoma cells toward neutrophil killing can be overcome by a combination of CD47-SIRPα checkpoint blockade and sodium stibogluconate (SSG), an anti-leishmaniasis drug and documented inhibitor of the tyrosine phosphatase SHP-1. SSG enhanced neutrophil-mediated ADCC of solid tumor cells but enabled trogoptotic killing of B-cell lymphoma cells by turning trogocytosis from a mechanism that contributes to resistance into a cytotoxic anti-cancer mechanism. Tumor cell killing in the presence of SSG required both antibody opsonization of the target cells and disruption of CD47-SIRPα interactions. These results provide a more detailed understanding of the role of neutrophil trogocytosis in antibody-mediated destruction of B cells and clues on how to further optimize antibody therapy of B-cell malignancies.

An autologous culture model of nodal B-cell lymphoma identifies ex vivo determinants of response to bispecific antibodies

AbstractBispecific antibodies (BsAbs) can induce long-term responses in patients with refractory and relapsed B-cell lymphoma. Nevertheless, response rates across patients are heterogeneous, and the factors determining quality and duration of responses are poorly understood. To identify key determinants of response to BsAbs, we established a primary, autologous culture model allowing us to mimic treatment with CD3xCD19 and CD3xCD20 BsAbs within the lymph node microenvironment ex vivo. T cell–mediated killing of lymphoma cells and proliferation of T cells varied significantly among patients but highly correlated between BsAbs targeting CD20 or CD19. Ex vivo response to BsAbs was significantly associated with expansion of T cells and secretion of effector molecules (eg, granzyme B, perforin) but not with expression of T-cell exhaustion (eg, PD1, TIM3) or activation markers (eg, CD25, CD69) or formation of intercellular contacts. In addition, we identified a distinct phenotype of regulatory T cells that was linked to ex vivo response independently from T-cell frequency at baseline. High expression levels of Aiolos (IKZF1), ICOS, and CXCR5 were positively associated with ex vivo response, whereas strong expression of Helios (IKZF2) had an unfavorable impact on ex vivo response to BsAbs. We further showed that lenalidomide, nivolumab, and atezolizumab improved ex vivo response to BsAbs by potentiating T-cell effector functions. In summary, our ex vivo study identified a distinct regulatory T-cell phenotype as a potential contributor to treatment failure of BsAbs and suggests drug combinations of high clinical relevance that could improve the efficacy of BsAbs.

The selection of variable regions affects effector mechanisms of IgA antibodies against CD20

AbstractBlockade of the CD47-SIRPα axis improves lymphoma cell killing by myeloid effector cells, which is an important effector mechanism for CD20 antibodies in vivo. The approved CD20 antibodies rituximab, ofatumumab, and obinutuzumab are of human immunoglobulin G1 (IgG1) isotype. We investigated the impact of the variable regions of these 3 CD20 antibodies when expressed as human IgA2 isotype variants. All 3 IgA2 antibodies mediated antibody-dependent cellular phagocytosis (ADCP) by macrophages and antibody-dependent cellular cytotoxicity (ADCC) by polymorphonuclear cells. Both effector mechanisms were significantly enhanced in the presence of a CD47-blocking antibody or by glutaminyl cyclase inhibition to interfere with CD47-SIRPα interactions. Interestingly, an IgA2 variant of obinutuzumab (OBI-IgA2) was consistently more potent than an IgA2 variant of rituximab (RTX-IgA2) or an IgA2 variant of ofatumumab (OFA-IgA2) in triggering ADCC. Furthermore, we observed more effective direct tumor cell killing by OBI-IgA2 compared with RTX-IgA2 and OFA-IgA2, which was caspase independent and required a functional cytoskeleton. IgA2 variants of all 3 antibodies triggered complement-dependent cytotoxicity, with OBI-IgA2 being less effective than RTX-IgA2 and OFA-IgA2. When we investigated the therapeutic efficacy of the CD20 IgA2 antibodies in different in vivo models, OBI-IgA2 was therapeutically more effective than RTX-IgA2 or OFA-IgA2. In vivo efficacy required the presence of a functional IgA receptor on effector cells and was independent of complement activation or direct lymphoma cell killing. These data characterize the functional activities of human IgA2 antibodies against CD20, which were affected by the selection of the respective variable regions. OBI-IgA2 proved particularly effective in vitro and in vivo, which may be relevant in the context of CD47-SIRPα blockade.