T-cell Lymphoma Cell Lines Research Articles

PI3Kδ activation, IL-6 overexpression, and CD37 loss cause resistance to naratuximab emtansine in lymphomas

AbstractCD37-directed antibody and cellular-based approaches have shown preclinical and promising early clinical activity. Naratuximab emtansine (Debio 1562; IMGN529) is an antibody-drug conjugate (ADC) incorporating an anti-CD37 monoclonal antibody conjugated to the maytansinoid DM1 as payload, with activity as a single agent and in combination with rituximab in patients with lymphoma. We studied naratuximab emtansine and its free payload in 54 lymphoma models, correlated its activity with CD37 expression, characterized 2 resistance mechanisms, and identified combination partners providing synergy. The activity, primarily cytotoxic, was more potent in B- than T-cell lymphoma cell lines. After prolonged exposure to the ADC, 1 diffuse large B-cell lymphoma (DLBCL) cell line developed resistance to the ADC due to the CD37 gene biallelic loss. After CD37 loss, we also observed upregulation of interleukin-6 (IL-6) and related transcripts. Recombinant IL-6 led to resistance. Anti-IL-6 antibody tocilizumab improved the ADC’s cytotoxic activity in CD37+ cells. In a second model, resistance was sustained by a PIK3CD activating mutation, with increased sensitivity to PI3Kδ inhibition and a functional dependence switch from MCL1 to BCL2. Adding idelalisib or venetoclax overcame resistance in the resistant derivative and improved cytotoxic activity in the parental cells. In conclusion, targeting B-cell lymphoma with the naratuximab emtansine showed vigorous antitumor activity as a single agent, which was also observed in models bearing genetic lesions associated with inferior outcomes, such as Myc Proto-Oncogene (MYC) translocations and TP53 inactivation or R-CHOP (rituximab, cyclophosphamide, doxorubicin, Oncovin [vincristine], and prednisone) resistance. Resistant DLBCL models identified active combinations of naratuximab emtansine with drugs targeting IL-6, PI3Kδ, and BCL2.

248 (PB236): Identification of inhibitors of BCL2 family members and glucose metabolism as effective combination partners of belinostat in T-cell lymphoma (TCL) cell lines

248 (PB236): Identification of inhibitors of BCL2 family members and glucose metabolism as effective combination partners of belinostat in T-cell lymphoma (TCL) cell lines

Effect of a supramolecular delivery system based on hyaluronic acid with cyclodextrin on the antitumor properties of oxaliplatin in vitro

One of the modern approaches to the treatment of cancer is the creation of targeted delivery systems for anticancer drugs, which allows increasing the concentration of the delivered substance in the right place and preventing its accumulation in healthy organs and tissues. At the same time, one can also expect an increase in the duration and effectiveness of the drugs, as well as a reduction in side effects during therapy. The hyaluronic acid receptor CD44, which, according to the literature, is highly expressed in many types of tumors and regulates metastasis, is a promising target for targeted delivery of anticancer drugs. The purpose of this study was to evaluate the effect of a supramolecular delivery system based on hyaluronic acid with nanosized cavitand cyclodextrin on the antitumor properties of oxaliplatin in vitro. Cell lines 1301, SK-MEL-28 and B16 were used as tumor cells. Cells were cultured in the presence of a delivery system based on hyaluronic acid (HACD), oxaliplatin (OX), and their complex (HACD-OX) at various concentrations in complete culture medium RPMI-1640 containing 0.3% L-glutamine, 4% gentamicin and 10% inactivated FBS serum for 48 hours in a humidified atmosphere of 5% CO2 at 37°C. The effect of the studied compounds on the viability of cell cultures was assessed using the WST test. It was shown that in the case of the T-cell lymphoma cell line 1301, the HACD delivery system did not affect the ability of OX to reduce the viability of tumor cells of this line; the effect of free oxaliplatin and the complex was comparable. However, in the case of melanoma cells (B16 and SK-MEL-28), the HACD-DOX complex has a more pronounced antitumor effect, causing a statistically significant decrease in the viability of B16 and SK-MEL-28 cells compared to free oxaliplatin.

A novel murine syngeneic CD8 peripheral T-cell lymphoma model with preclinical applications

Peripheral T-cell Lymphoma (PTCL) represents a heterogenous group of aggressive non-Hodgkin Lymphomas with poor prognostic outcomes and limited treatment options. The development and refinement of therapeutic strategies for PTCL are impeded by a paucity of reliable preclinical models that accurately mimic the disease’s pathophysiology. There is a dire need for more physiologically relevant models for PTCL. Here we describe a spontaneousCD8+ peripheral T-cell lymphoma cell line (LM-23) derived from a 12-week-old female Balb/cJ mouse. Both intravenous and subcutaneous administration of this cell line to syngeneic Balb/cJ mice resulted in rapid establishment of tumor growth. CHOP and anti-PD1 treatment both displayed no benefit to mice in regulating tumor growth. Such results along with its phenotypic characteristics, rapid growth, and metastatic behavior in syngeneic mice highlight its value in studying the elusive disease and discovery of novel therapeutics.

EBV + B cell-derived exosomes promote EBV-associated T/NK-cell lymphoproliferative disease immune evasion by STAT3/IL-10/PD-L1 pathway.

EBV-associated T/NK-cell lymphoproliferative diseases (EBV-T/NK-LPDs) are characterized by the clonal proliferation of EBV-positive ( +) T/NK cells. EBV is typically latent in B cells and the mechanism by which the EBV genome invades T/NK cells remains unknown. Recent studies have demonstrated that exosomes derived from EBV + B cells play a pivotal role in immunosuppressive microenvironment remodeling. Moreover, the existence of an immunosuppressive microenvironment is known to be critical in the development of EBV-T/NK-LPDs. Hence, we hypothesized that exosomes derived from EBV + B cells might promote the development of EBV-T/NK-LPDs by stimulating immune evasion. In this study, we utilized paraffin sections to clarify the STAT3/IL-10/PD-L1-associated immunosuppressive microenvironment in EBV-T/NK-LPDs. Further, we extracted exosomes from BL2009 (EBV + B cell lymphoma) and CA46 (EBV- B cell lymphoma) cell lines to co-culture with cutaneous T-cell lymphoma (CTCL) cell lines, to verify the changes in the above immune evasion pathway. The paraffin sections of EBV-T/NK-LPDs showed high-expression levels of IL-10/PD-L1, which might be related to the phosphorylation of STAT3. Exosomes derived from EBV + B cells could significantly activate the STAT3/IL-10/PD-L1 pathway. After being treated with C188-9, EBV + B cell-derived exosomes were no longer able to stimulate the expression of IL-10/PD-L1 in CTCL cells. EBV-T/NK-LPDs have a STAT3/IL-10/PD-L1 overactivation-associated immunosuppressive microenvironment. Our study elucidated part of this mechanism. Exosomes derived from EBV + B could induce phosphorylation of STAT3 in CTCL cells, leading to the overexpression of IL-10/PD-L1. Our findings might shed light on new directions for understanding immune evasion in EBV-T/NK-LPDs.

Ultrasensitive Response Explains the Benefit of Combination Chemotherapy Despite Drug Antagonism.

Most aggressive lymphomas are treated with combination chemotherapy, commonly as multiple cycles of concurrent drug administration. Concurrent administration is in theory optimal when combination therapies have synergistic (more than additive) drug interactions. We investigated pharmacodynamic interactions in the standard 4-drug "CHOP" regimen in peripheral T-cell lymphoma (PTCL) cell lines and found that CHOP consistently exhibits antagonism and not synergy. We tested whether staggered treatment schedules could improve tumor cell kill by avoiding antagonism, using in vitro models of concurrent or staggered treatments. Surprisingly, we observed that tumor cell kill is maximized by concurrent drug administration despite antagonistic drug-drug interactions. We propose that an ultrasensitive dose response, as described in radiology by the linear-quadratic (LQ) model, can reconcile these seemingly contradictory experimental observations. The LQ model describes the relationship between cell survival and dose, and in radiology has identified scenarios favoring hypofractionated radiotherapy-the administration of fewer large doses rather than multiple smaller doses. Specifically, hypofractionated treatment can be favored when cells require an accumulation of DNA damage, rather than a "single hit," to die. By adapting the LQ model to combination chemotherapy and accounting for tumor heterogeneity, we find that tumor cell kill is maximized by concurrent administration of multiple drugs, even when chemotherapies have antagonistic interactions. Thus, our study identifies a new mechanism by which combination chemotherapy can be clinically beneficial that is not contingent on positive drug-drug interactions.

Abstract 3207: Chemical fabrication and characterization of a novel nanoparticle of the histone deacetylase (HDACi) romidepsin

Abstract Introduction: Histone Deacetylase inhibitors (HDACi) are important drugs for the treatment of patients with PTCL (peripheral T-cell lymphoma). Romidepsin (R), a potent Class I HDACi, is given intravenously, weekly for three to four consecutive weeks. R has a half-life of three hours and is extensively protein bound. The indication for R in PTCL was recently withdrawn due to a failed Phase 4 study. Given the need for new drugs in PTCL, and the importance of epigenetically targeted drugs for the disease, we developed a first-in-class nanoparticle of R (NR) deploying a proprietary nanochemistry platform. Methods: We modified the bulk nanoprecipitation method with FDA approved and Generally Recognized as Safe (GRAS) materials, specifically including PEGylated amphiphilic diblock copolymers, to develop NR combinatorially. By combining a drug and polymer solution with an anti-solvent, we produced core-shell structured NR particles with “stealth” properties. To achieve high R loading, stability, purity, scalability, and reproducibility, we devised a multi-pronged optimization system by modulating parameter sets in tandem. We determined the optimal parameters for the "lockdown" formulation. We purified NR by using centrifugal filters and determined stability by storing at 4°C. We used Cryo-electron microscopy (cryo-EM), Dynamic Light Scattering (DLS), and Liquid Chromatography-Mass Spectrometry (LC-MS) to determine the morphology, size, PDI, and drug concentration of NR. We developed fluorescent-NR with DiO dye to test bioavailability. We tested NR in T-cell lymphoma cell lines for histone acetylation and apoptosis induction. Furthermore, we investigated the in vivo pharmacokinetics and toxicity of NR in PTCL xenograft mouse model and quantified the drug by LC-MS. Results: The physiochemical analysis of NR demonstrated that the particles were spherical, with a hydrodynamic diameter of 46 ±5 nm and PDI of 0.15 - 0.2. NR had a negative zeta potential and an exceptional drug encapsulation efficiency of over 50% (>500 µg/mL). NR exhibited high stability with respect to size, PDI and drug concentration for over two years. Flow cytometry and western blot analyses indicate NR induces apoptosis and histone acetylation in a time and dose-dependent manner, equivalent to or better than that observed for R. NR’s AUC increased 25-fold when administered intravenously. NR had superior tolerability, and DiO-NR confirmed superior biodistribution in tumor in a PTCL xenograft mouse model. Conclusion: We developed a cutting-edge approach with minimum excipients, which enabled NR scale up with batch-to-batch reproducibility and high quality co-packaging of fluorescent dye and drug. NR improved R’s pharmacokinetic profile and efficacy in pre-clinical xenograft mice models. Our versatile technology enables Chemistry Materials and Controls products, an essential step in clinical product development. Citation Format: Samir Zuberi, Deepthi P. Damera, Ipsita Pal, Susan Walker, Ramesh Katla, Colin Haws, Akhil Gajjala, Andrea Joyner, Kallesh D. Jayappa, David J. Feith, Todd E. Fox, Thomas P. Loughran, Owen A. O'Connor, Anuradha Illendula. Chemical fabrication and characterization of a novel nanoparticle of the histone deacetylase (HDACi) romidepsin [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 3207.

Antibody targeting of surface P-selectin glycoprotein ligand 1 leads to lymphoma apoptosis and tumorigenesis inhibition.

Lymphomas are a heterogeneous group of diseases that originate from T, B or natural killer cells. Lymphoma treatment is based on chemotherapy, radiotherapy, and monoclonal antibody (mAb) or other immunotherapies. The P-selectin glycoprotein ligand 1 (PSGL-1) is expressed at the surface of hematological malignant cells and has been shown to have a pro-oncogenic role in multiple myeloma and lymphoma. Here, we investigated the expression and therapeutic potential of PSGL-1 in T and B cell lymphomas. By flow cytometry analysis, we found that PSGL-1 was expressed in both T and B cell-derived lymphoma cell lines but generally at higher levels in T cell lymphoma cell lines. For most T and B cell-derived lymphoma cell lines, in vitro targeting with the PL1 mAb, which recognizes the PSGL-1 N-terminal extracellular region and blocks functional interactions with selectins, resulted in reduced cell viability. The PL1 mAb pro-apoptotic activity was shown to be dose-dependent, to be linked to increased ERK kinase phosphorylation, and to be dependent on the MAP kinase signaling pathway. Importantly, anti-PSGL-1 treatment of mice xenografted with the HUT-78 cutaneous T-cell lymphoma cell line resulted in decreased tumor growth, had no effect on in vivo proliferation, but increased the levels of apoptosis in tumors. Anti-PSGL-1 treatment of mice xenografted with a Burkitt lymphoma cell line that was resistant to anti-PSGL-1 treatment in vitro, had no impact on tumorigenesis. These findings show that PSGL-1 antibody targeting triggers lymphoma cell apoptosis and substantiates PSGL-1 as a potential target for lymphoma therapy.

The inhibitory and transcriptional effects of the epigenetic repurposed drugs hydralazine and valproate in lymphoma cells.

Lymphoma is a disease that affects countless lives each year. In order to combat this disease, researchers have been exploring the potential of DNMTi and HDACi drugs. These drugs target the cellular processes that contribute to lymphomagenesis and treatment resistance. Our research evaluated the effectiveness of a combination of two such drugs, hydralazine (DNMTi) and valproate (HDACi), in B-cell and T-cell lymphoma cell lines. Here we show that the combination of hydralazine and valproate decreased the viability of cells over time, leading to the arrest of cell-cycle and apoptosis in both B and T-cells. This combination of drugs proved to be synergistic, with each drug showing significant growth inhibition individually. Microarray analyses of HuT 78 and Raji cells showed that the combination of hydralazine and valproate resulted in the up-regulation of 562 and 850 genes, respectively, while down-regulating 152 and 650 genes. Several proapoptotic and cell cycle-related genes were found to be up-regulated. Notably, three and five of the ten most up-regulated genes in HuT 78 and Raji cells, respectively, were related to immune function. In summary, our study suggests that the combination of hydralazine and valproate is an effective treatment option for both B- and T-lymphomas. These findings are highly encouraging, and we urge further clinical evaluation to validate our research and potentially improve lymphoma treatment.

Development and Characterization of a Novel Murine Peripheral T-Cell Lymphoma Cell Line Which Closely Mimics Human Disease

Peripheral T-cell lymphoma (PTCL) represents a heterogenous group of aggressive non-Hodgkin lymphomas with poor prognostic outcomes and limited treatment options. Despite the advances in genomic sequencing and molecular characterization, the complex and elusive nature of PTCL's underlying biology has proven difficult to fully understand and manage effectively. The development and refinement of therapeutic strategies for PTCL are impeded by a paucity of reliable preclinical models that accurately mimic the disease's pathophysiology. There is a dire need for more physiologically relevant models for PTCL. Improved models allow for a better understanding of the disease's molecular and cellular mechanisms, facilitate the development of innovative therapeutic strategies, and ultimately improve patient outcomes. Here we described a new T-cell lymphoma cell line (LM-23) derived from a 12-week-old female Balb/cJ mouse which developed diffuse adenopathy and splenomegaly. Tumors from this mouse were cultured in cRPMI + 10% fetal bovine serum for 4 weeks without supplementation of additional cytokines and passaged 3-4 times per week where we found the cells to be non-adherent. Immunophenotyping of LM-23 demonstrated positivity for CD90, CD3, TCR-beta, CD4(partial/subset), CD8, PD1 (positive), ICOS (positive) and negative for B-cell and myeloid lineage markers (Fig. 1B). This immunophenotype most closely resembles PTCL-NOS in humans at an immunophenotypic characterization level. Whole exome sequencing is in progress and will be presented. Intravenous administration of this cell line to syngeneic Balb/cJ mice resulted in rapid establishment of diffuse adenopathy, splenomegaly, and liver metastases. Bulky adenopathy was observable within 14 days of administration. Histologically, these tumors consisted of sheets of medium to large sized lymphocytes with clumped chromatin and prominent nucleoli, similar to human T-cell lymphomas (Fig. 1A). Subcutaneous administration demonstrated rapid tumor growth with mice reaching terminal endpoints (>2,000mm 3) within 21 days following administration. As CHOP-based (cyclophosphamide, doxorubicin, vincristine, and prednisone) therapies are the primary backbone for treatment of PTCL, we tested whether CHOP therapy alone had anti-tumor activity to LM-23. Tumor bearing mice (~150mm 3) were treated with CHOP and monitored for tumor growth. All mice treated were non-responsive to CHOP therapy with no difference in tumor growth compared to untreated mice. Additionally, LM-23 bearing mice treated with anti-PD1 showed signs of hyperprogression, which has been observed in human patients in clinical trials (Gao Y et al. JCI Insight 2023, Bennani NN et al. Blood Supplement 2019). Additional therapeutic target testing is underway and will be presented. In conclusion, the newly established LM-23 T-cell lymphoma cell line provides a novel, physiologically relevant preclinical model for the study of PTCL. Its phenotypic characteristics, rapid growth, and metastatic behavior in syngeneic mice, along with its resistance to CHOP therapy and hyperprogression upon anti-PD1 treatment, mimicking the clinical scenarios observed in some human PTCL patients. These features highlight LM-23's potential as a valuable tool for understanding the biological mechanisms underlying PTCL and for the development and testing of innovative therapeutic strategies. We hope that the LM-23 cell line will contribute significantly to these efforts, ultimately improving outcomes for patients afflicted with PTCL.

Xpo-1 Antagonism Impairs CSF-1R Expression and Depletes Lymphoma-Associated Macrophages in T-Cell Lymphomas

Background: Lymphoma-associated macrophages (LAM) provide ligands for antigen, costimulatory, and cytokine receptors expressed by malignant T cells and directly promote T-cell lymphomagenesis. LAM also play an important role in suppressing host anti-tumor immunity and indirectly promote T-cell lymphomagenesis. Therefore, LAM are a therapeutic vulnerability in T-cell lymphomas (TCL), and their depletion from the tumor microenvironment (TME) is a rational therapeutic goal. Methods: XPO1 and CD163 expression were examined by immunohistochemical staining. In order to determine the extent to which XPO1 antagonism depletes LAM, a pharmacologic strategy was adopted using selinexor. Viability of human monocyte-derived and TCL conditioned macrophages upon selinexor treatment was examined in vitro using standard methods. RNA binding to eIF4e was determined by RNA immunoprecipitation (RIP) using eIF4e and IgG antibodies and quantification performed by qPCR. Nuclear export of eIF4e client mRNA upon XPO1 antagonism with selinexor was examined by qRT-PCR in nuclear and cytoplasmic pools of RNA. LAM depletion upon selinexor treatment was examined in vivo using a previously described GEM ( Smarcb1-deficient) model and CD68-GFP reporter mice. Results: As we had previously demonstrated that CD163 identifies LAM that are alternatively polarized and proliferative, co-staining was performed with CD163 and XPO1, and CD163+XPO-1+ LAM identified in 69% of PTCL cases (n=26) examined. We previously demonstrated that LAM within a PTCL context are resistant to inhibition by selective CSF-1R antagonists. Therefore, we performed an unbiased, high-throughput screen using monocytes cultured in the presence of cell-free conditioned media (CFCM) obtained from T-cell lymphoma cell lines and primary specimens. This screen identified selinexor as a potential therapeutic vulnerability. Therefore, we cultured normal-donor monocytes in RPMI media alone, or in media supplemented with cell free conditioned media (CFCM) obtained from PTCL/CTCL cell lines (n=2) or primary specimens (n=5) and determined cell viability. Consistent with our prior findings, CFCM from PTCL/CTCL cells promoted the growth and survival of monocyte-derived macrophages (MDM), but this effect was abrogated upon selinexor treatment. These findings converged with the observation that CSF-1R transcripts are eIF4e clients in ALCL cells. Therefore, the extent to which transcripts required for macrophage survival (i.e. CSF-1R), proliferation (i.e. PU.1), and polarization (i.e. STAT3) are eIF4e clients was examined by eIF4e-RIP in MDM. These experiments demonstrated that CSF-1R, PU.1 and STAT3 are eIF4e clients, and selinexor treatment significantly decreased their nuclear export in MDM. Given the obvious clinical relevance of CSF-1R as a therapeutic target, CSF-1R expression in MDM following selinexor treatment was examined, and compatible with these results, a significant decrease in CSF-1R expression observed upon selinexor treatment. We previously employed CD68-GFP reporter mice in a Smarcb1-deficient GEM model, demonstrating that GFP+ macrophages in this TCL model are transcriptionally reprogrammed and proliferative. Selective CSF-1R antagonists minimally impair LAM survival in this model. In contrast, selinexor significantly depleted LAM ex vivo in this model and impaired the viability of bone marrow derived macrophages. In order to extend these findings, lymphoma-bearing GEM mice were treated with selinexor and the abundance of CD11b+Ly6G- LAM determined by flow cytometry, whereby a significant reduction in LAM abundance and TCL progression were observed, compatible with our in vitro/ex vivo findings. Conclusions: Therefore, we concluded that XPO1 inhibition indirectly impairs T-cell lymphoma growth and survival by depleting LAM, which are a dependency in these lymphomas.

Pre-Clinical Activity of Navitoclax in TCR-Driven and Non-ALCL Mature T-Cell Lymphomas

Background: In contrast to many B-cell lymphomas that highly express BCL-2, BCL-2 expression is observed in <50% of most mature T-cell lymphoma (MTCL) subtypes, although a clinical trial investigating venetoclax in BCL-2 positive relapsed/refractory PTCL is ongoing (NCT03552692). In contrast, BCL-xL and/or MCL-1 are expressed in the majority of MTCL. Consistent with these findings, MCL-1 expressing anaplastic large cell lymphomas (ALCL) and typical (non-ETP) T-ALL, which highly express BCL-xL, have been shown by BH3 profiling to be dependent upon MCL-1 or BCL-xL, respectively. Among the more common MTCL subtypes, including cutaneous T-cell lymphomas (CTCL), the extent to which BCL-2 family members are a therapeutic vulnerability is uncertain. However, we have previously demonstrated that antigen- and costimulatory receptor signaling promote the growth and survival of these lymphomas and confers resistance to chemotherapy, and in conventional (non-malignant) T cells, these same signals upregulate BCL-xL, which is required for their clonal expansion and escape from cell death following T-cell activation. Therefore, given the increasing availability of selective BH3 mimetics and the need for improved therapeutic strategies, we were motivated to examine BCL-2 family member dependencies in these lymphomas. Methods: Peptides generated from BH3-only proteins and selective BH3 mimetics were utilized to perform “BH3 profilng” in MTCL. Cell viability upon exposure to BH3 mimetics was determined using standard approaches. Results: To pre-clinically assess BCL-2 family member dependencies and the mitochondrial apoptotic pathway in T-cell lymphoproliferative neoplasms, we performed BH3 profiling in 17 cell lines. Peptides derived from BIM and PUMA, which are promiscuous, were utilized to assess the extent to which cells are “primed” for apoptosis. Differences in apoptotic priming were not observed across subtypes, and most cell lines examined were highly primed. We next examined the dependence on specific antiapoptotic proteins by BH3 profiling using BAD (antagonizes BCL-2, BCL-xL, and BCL-w), HRK (antagonizes BCL-xL), MS1 (antagonizes MCL-1), and FS1 (antagonizes A1/BFL-1) peptides. BCL-2 dependence was not observed in the T-cell lymphoma cell lines we examined. However, and in stark contrast, most non-ALCL cell lines were BCL-xL dependent, whereas ALCL cell lines were largely MCL-1 dependent. In an effort to further confirm these results, and examine the extent to which peptide-based BH3 profiling predicts sensitivity to selective BH3 mimetics in MTCL, cell lines were treated with venetoclax, A1155463 (a BCL-xL selective antagonist), navitoclax (a BCL-2/BCL-xL antagonist), or S63845 (MCL-1 antagonist), and cell viability determined. Consistent with peptide-based BH3 profiling, all cell lines examined were resistant to venetoclax. ALCL cell lines were largely MCL-1 dependent, whereas the non-ALCL cell lines examined were largely BCL-xL dependent. Therefore, we examined BCL-xL and MCL-1 expression in these cells and observed a strong association between BCL-xL expression and both cytochrome c release in response to HRK peptide and cell viability in the presence of A1155463. A similar association was observed between MCL-1 expression and sensitivity to MS1 and S63845. Transcriptionally profiled MTCL specimens were stratified by MTCL classification (ALCL vs. non-ALCL) and in keeping with the data obtained using cell lines increased BCL-xL expression was observed in non-ALCL MTCL subtypes. Given the observed association between BCL-xL expression and vulnerability to BCL-xL antagonists, we sought to examined mechanisms that promote its expression. Both TCR signaling and CD28 costimulation are exploited by non-ALCL subtypes. We examined the extent to which TCR/CD28 stimulation regulates BCL-xL transcription. In MTCL specimens, a significant increase in BCL-xL transcription and sensitization to Bcl-xL antagonism were observed upon TCR/CD28 stimulation. A TCR-dependent GEM model was utilized, demonstrating that these MTCL are Bcl-xL dependent and sensitive to navitoclax. Conclusions: These findings suggest that BCL-xL is a therapeutic vulnerability for MTCL subsets, particularly non-ALCL subtypes that are TCR dependent, and provide a robust pre-clinical rationale for future studies investigating navitoclax in these lymphomas.

Xpo-1 Antagonism Transcriptionally Reprograms and Is a Therapeutic Vulnerability in GATA-3 Driven T-Cell Lymphomas

Background: The transcription factor GATA-3, via the oncogenic transcriptional program it directs, is a bona fide proto-oncogene, and thus therapeutic target, in a subset of T-cell lymphomas (TCL). The eukaryotic translation initiation factor eIF4E, in complex with helicase and scaffolding factors, facilitates 40S ribosome and Met-tRNA recruitment, both of which are rate-limiting steps in the initiation of translation. Pathways that converge on eIF4E, including PI3K/AKT/mTOR-dependent phosphorylation of 4E-BP1, are frequently activated in GATA-3 PTCL. Within the nucleus, eIF4E specifically binds oncogenic mRNAs, and then forms a complex with a co-factor (LRPPRC) and the nuclear export receptor XPO1. In contrast to bulk mRNA, these eIF4E-bound mRNA are dependent upon XPO1 for nuclear export. Therefore, as we have shown that GATA-3 is oncogenic in T-cell lymphomas (TCL), we hypothesized that selective XPO1 inhibition may transcriptionally reprogram these TCL and is a novel therapeutic vulnerability. Methods: XPO1 expression was examined by immunohistochemistry or flow cytometry in TCL specimens and in TCL that emerge in multiple genetically engineered mouse (GEM) models. Transcripts that are eIF4e clients and dependent upon XPO-1 for nuclear export were identified in an unbiased manner by eIF4e RNA immunoprecipitation (eIF4e-RIP) and RNA-seq. The extent to which XPO1 antagonism transcriptionally reprograms TCL cells, and its value as a therapeutic strategy, was examined pharmacologically with selinexor in ex vivo and in vivo studies using primary TCL specimens and GEM/PDX models, respectively. Results: Among the PTCL cases (n=53) examined, XPO1 expression was observed in 62%, and was highly expressed in CTCL, particularly in patients with large cell transformation. We sought to further understand the extent to which XPO1 expression is associated with T-cell lymphomagenesis. We utilized multiple GEM TCL models in which Smarcb1 (SNF5) or PTEN were conditionally deleted in CD4 + T cells. In both GEM models, a significant increase in XPO-1 expression was associated with the emergence of a malignant clone. A significant reduction in cell viability and increased apoptosis was observed in TCL cell lines and primary specimens treated in vitro/ex vivo with selinexor. In both GEM models, and a PDX model, selinexor treatment similarly decreased TCL progression in vivo. Given these findings, we elected to examine XPO1's potential role in transporting oncogenic, and eIF4e client, transcripts. We performed eIF4e-RIP and RNA-seq in two representative cell lines. Gene set enrichment analysis utilizing the eIF4e client RNA identified demonstrated enrichment for pathways with an established role in TCL (e.g. TCR), including GATA-3. We subsequently performed eIF4e-RIP and quantified GATA-3 transcripts by qRT-PCR in cell lines (n=4), a PDX, and in primary SS specimens (n=2). Compatible with the RNA-seq data, significant enrichment in GATA-3 transcripts was observed. These findings imply that GATA-3 transcripts are dependent upon XPO1 for nuclear export. To directly examine this, the ratio of cytoplasmic to nuclear (C:N) GATA-3 transcripts were examined by qRT-PCR in cell lines treated with selinexor. A significant decrease in the C:N ratio was observed upon XPO1 inhibition, confirming that nuclear export of GATA-3 transcripts is XPO1 dependent. We similarly examined the extent to which GATA-3 target genes are eIF4e clients and XPO1 dependent for nuclear export. We had previously described GATA-3 target genes by integrated ChIP-seq/RNA-seq. Integration of this prior dataset with our eIF4e-RIP sequencing data demonstrated that ≈21-30% of previously described GATA-3 target genes were also eIF4e clients. We selected a few such targets, including ITK, for further validation. These GATA-3 targets were eIF4e clients and dependent upon XPO1 for nuclear export. Finally, we examined expression of these proteins in a diverse panel of T-cell lymphoma/leukemia cell lines and a primary SS specimen after brief exposure to selinexor, and compatible with our findings, a significant decrease in protein expression was observed. Conclusions: Collectively then, our findings demonstrate that XPO1 antagonism, by impairing the nuclear export of both GATA-3 and many of its target gene mRNA, is a novel strategy to transcriptionally reprogram and therapeutically target GATA-3 driven TCL.

C17ORF58 Is Upregulated in Peripheral T-Cell Lymphomas and Encodes a Protein Critical for Survival of PTCL Cells

Peripheral T-cell lymphomas (PTCL) constitute a group of heterogeneous T- and NK-cell malignancies, accounting for about 15% of Non-Hodgkin lymphomas (NHL). Most PTCL subtypes exhibit an aggressive disease presentation, carrying a worse prognosis than B-cell lymphomas. PTCL - Not Otherwise Specified (PTCL-NOS), the largest subgroup, is categorized by exclusion, with a diagnosis given if the patient does not meet the diagnostic criteria of other PTCL subtypes. PTCL-NOS is a heterogeneous group with diverse cells of origin, varied cytogenic, molecular, and morphological phenotypes, and antigen variability. Despite the increase in specific T-cell lymphoma treatment options, such as belinostat, romidepsin, pralatrexate, and brentuximab vedotin, alongside conventional non-targeted chemotherapy like CHOP and R-CHOP, the overall 5 year survival remains only at 20-30%. A deeper understanding of the pathways and genes critical for PTCL-NOS survival is urgently needed. In our quest to better understand the molecular landscape, we performed a gene expression analysis of ten PTCL-NOS lymphomas and five normal samples using RNAseq analysis. Our study identified ~400 genes consistently upregulated in lymphoma samples, indicating potential involvement in tumor maintenance. Following the exclusion of common essential genes, we performed a shRNA-mediated knockdown screen of the remaining candidates in the human PTCL-NOS cell line T8ML-1. This approach unveiled several lethal genes, including MYBL2, TRIP13, KIF18B, C17ORF58, and others. Cell cycle analysis demonstrated that while knockdown of MYBL2, TRIP13, and KIF18B induced G2-M arrest, downregulation of C17ORF58 primarily induced apoptosis. Notably, downregulation of C17ORF58 did not impact the proliferation of human embryonic kidney fibroblasts HEK 293T, suggesting that normal cells might not require this protein for growth. However, its downregulation in additional hematologic cell lines, such as Cutaneous T-cell lymphoma cell lines (HH, Hut78) and T-cell lymphoblastic leukemia (Jurkat), also induced apoptosis, which suggests a key role for C17ORF58 in T-cell malignancies. Analysis of publicly available RNAseq data revealed overexpression of C17ORF58 in the majority of PTCL-NOS, Anaplastic Large Cell, Hepatosplenic T-cell, and malignant NK/T-cell lymphomas, relative to normal T-cells, thus highlighting its possible role in tumor development and maintenance. C17ORF58 encodes a predicted protein of 339 amino acids, with an estimated molecular weight of 37 kDa. This protein features two putative domains: the PRK07764 domain, which is homologous to DNA polymerase III subunits gamma and tau, and the netrin module, a 130 amino acid residue domain found within the C-terminal sections of various proteins, including netrins, complement proteins C3-C5, secreted frizzled-related proteins, and type I procollagen C-proteinase enhancer proteins. The predicted promoter has binding sites for Oct-B1-3, Pax-2, POU2F1-2, 2B, and 2C, suggesting that the C17ORF58-encoded protein may participate in normal development. In conclusion, our data indicate that upregulation of C17ORF58 may contribute to the progression and maintenance of PTCL and could serve as a potential target for treating T-cell malignancies. Investigations into its physiological role in normal T-cells and pathways deregulated upon its inactivation are ongoing.

Successful anti-tumor effects with two novel bifunctional chemotherapeutic compounds that combine a LAT1 substrate with cytotoxic moieties in aggressive T-cell lymphomas

T-cell lymphomas are aggressive neoplasms characterized by poor responses to current chemotherapeutic agents. Expression of the l-type amino acid transporter 1 (LAT 1, SLC7A5) allows for the expansion of healthy T-cell counterparts, and upregulation of LAT1 has been reported in precursor T-cell acute leukemia. Therefore, the expression of LAT1 was evaluated in a cohort of cutaneous and peripheral T-cell lymphomas. The findings demonstrated that LAT1 is upregulated in aggressive variants and absent in low-grade or indolent disease such as mycosis fungoides. In addition, upregulated LAT1 expression was seen in a large proportion of aggressive peripheral T-cell lymphomas, including peripheral T-cell lymphoma not otherwise specific (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL). The anti-tumor effects of two novel non-cleavable and bifunctional compounds, QBS10072S and QBS10096S, that combine a potent cytotoxic chemotherapeutic domain (tertiary N-bis(2-chloroethyl)amine) with the structural features of a selective LAT1 substrate (aromatic β-amino acid) were tested in vitro and in vivo in T-cell lymphoma cell lines. The findings demonstrated decreased survival of T-cell lymphoma lines with both compounds. Overall, the results demonstrate that LAT1 is a valuable biomarker for aggressive T-cell lymphoma counterparts and QBS10072S and QBS10096S are successful therapeutic options for these aggressive diseases.

Targeting T-Cell Lymphoma Using CD70-Directed Cord Blood-Derived CAR-NK Cells

T-cell lymphomas (TCL) are a heterogenous group of non-Hodgkin lymphoma characterized by resistance to conventional therapies posing an urgent need for safe and effective therapies. CAR-NK cells have emerged as a promising “off-the-shelf” cancer immunotherapy and are especially attractive for the treatment of T-cell malignancies. This is especially the case given the challenge of targeting T cell malignancies with CAR T cells due to shared antigens across the therapeutic, normal and malignant T cells posing the risk of CAR T cell fratricide, T-cell aplasia, and contamination of the CAR T products with malignant T cells. We have developed an FDA-approved system for ex vivo NK cell expansion, which reliably generates clinically relevant doses of GMP-grade NK cells from a cord blood (CB) unit. We have used this platform to engineer NK cells to express a CAR targeting CD19 using GMP-grade retroviral vectors and demonstrated the safety and efficacy of this platform in the clinic. We now propose to expand this approach to target TCL. CD70, a surface ligand of CD27, is overexpressed in a variety of cancers, including TCL. Signaling mediated by CD70-CD27 is thought to induce proliferation of TCL cells via activation of the NF-κB pathway. Thus, CD70 is an attractive target for CAR NK-cell therapy against TCL. We analyzed the publicly available primary TCL dataset (GSE19069) including anaplastic large cell lymphoma (30 samples), angioimmunoblastic TCL (37 samples), peripheral TCL (PTCL; 50 samples), and adult T cell leukemia/lymphoma (13 samples) for CD70 expression. The majority of the samples expressed CD70 transcript with a variable level of expression ( Figure 1). Using flow cytometry, we screened a panel of TCL cell lines with diverse histologic, cytogenetic and molecular properties for the expression of CD70. We demonstrated positive CD70 expression on most of the TCL cell lines profiled encompassing anaplastic large cell lymphoma (ALK+: KAR299; ALK-: MAC2A; fusion gene NPM-ALK+: SU-DHL1 and SUP-M2), hepatosplenic gamma-delta TCL (DERL-7), Sezary syndrome (SS; H9 and HuT78), and PTCL NOS (OCI-LY12). The CD70 intensity was highest on MAC2A, HuT78, KAR299 and SUP-M2, intermediate to low on DERL-7 and H9, and negative on SU-DHL1 and OCI-LY12. We designed a novel retroviral vector targeting CD70 that: 1) encodes the CD70-targeting CAR gene based on the CD27 extracellular domain; 2) ectopically produces interleukin (IL)-15 to support NK cell proliferation; and 3) expresses the suicide gene inducible caspase 9 ( iC9) that can be pharmacologically activated to eliminate transduced cells in the event of toxicity. The construct will be referred to as CAR.70/IL-15. Non-transduced (NT) NK cells and NK cells transduced with a construct that leads to IL-15 production without a CAR (IL-15 NK cells) were used as controls. We demonstrated that CAR.70/IL-15 NK cells had a significantly enhanced cytotoxicity compared to NT- and IL-15 NK cells against the CD70+ cell lines while there was no difference in cytotoxicity between the NK cell conditions in the negative cell lines pointing to a CD70-targeted fashion of anti-TCL NK cell cytotoxicity. Moreover, CAR.70/IL-15 NK cells exhibited greater cytotoxicity against CD70+ cell lines in long-term cytotoxicity assays ( Figure 2). In a tumor rechallenge assay against KAR299 where fresh tumor cells were added every 3-4 days, CAR.70/IL-15 NK cells showed superior potency in continuous tumor control. In addition, CAR.70/IL-15 NK cells exhibited higher levels of degranulation (CD107a) and cytokine production (TNFα and INF-γ) when cocultured with CD70+ TCL cell lines, compared to NT and IL-15 NK cells. Furthermore, these CAR NK cells targeting CD70 outperformed CAR NK cells engineered to target CD19, which is an irrelevant target for TCL, further confirming the specific CD70-targeted activity of CAR.70/IL-15 NK cells. CyTOF immunophenotyping revealed that CAR.70/IL-15 NK cells are characterized by the increased expression of markers of cytotoxicity such as granzyme-b, perforin, TRAIL; and activating coreceptors/proliferation markers such as DNAM, CD25 and Ki67. Taken together, our findings validate CD70 as a promising target for TCL treatment using CAR NK cells. Our approach provides a solid foundation for the clinical translation of CD70-targeting CAR NK-cell therapy for patients with TCL.

P-156 - Sensitivity to brentuximab vedotin depends on CD30-expression levels in different subtypes of cutaneous T-cell lymphoma cell lines

P-156 - Sensitivity to brentuximab vedotin depends on CD30-expression levels in different subtypes of cutaneous T-cell lymphoma cell lines

Development of a Novel CD26-Targeted Chimeric Antigen Receptor T-Cell Therapy for CD26-Expressing T-Cell Malignancies.

Chimeric-antigen-receptor (CAR) T-cell therapy for CD19-expressing B-cell malignancies is already widely adopted in clinical practice. On the other hand, the development of CAR-T-cell therapy for T-cell malignancies is in its nascent stage. One of the potential targets is CD26, to which we have developed and evaluated the efficacy and safety of the humanized monoclonal antibody YS110. We generated second (CD28) and third (CD28/4-1BB) generation CD26-targeted CAR-T-cells (CD26-2G/3G) using YS110 as the single-chain variable fragment. When co-cultured with CD26-overexpressing target cells, CD26-2G/3G strongly expressed the activation marker CD69 and secreted IFNgamma. In vitro studies targeting the T-cell leukemia cell line HSB2 showed that CD26-2G/3G exhibited significant anti-leukemia effects with the secretion of granzymeB, TNFα, and IL-8, with 3G being superior to 2G. CD26-2G/3G was also highly effective against T-cell lymphoma cells derived from patients. In an in vivo mouse model in which a T-cell lymphoma cell line, KARPAS299, was transplanted subcutaneously, CD26-3G inhibited tumor growth, whereas 2G had no effect. Furthermore, in a systemic dissemination model in which HSB2 was administered intravenously, CD26-3G inhibited tumor growth more potently than 2G, resulting in greater survival benefit. The third-generation CD26-targeted CAR-T-cell therapy may be a promising treatment modality for T-cell malignancies.

The RHOA Mutation G17V Does Not Lead to Increased Migration of Human Malignant T Cells but Is Associated with Matrix Remodelling

Nodal T-follicular helper cell lymphoma, angioimmunoblastic-type (AITL), is characterized by constitutional symptoms, advanced-stage disease, and generalized lymphadenopathy. A genetic hallmark of this lymphoma is the frequent occurrence of the RHOA mutation G17V in neoplastic cells, which is observed in around 60% of patients. Because RHOA is involved in both T-cell receptor downstream signalling and cell migration, we hypothesized that the characteristic presentation of AITL could be the result of enhanced tumor cell migration. Therefore, this study aimed to elucidate the impact of the RHOA variant G17V on the migration of neoplastic T cells. We transfected the T-cell lymphoma cell lines HH and HuT78 to stably express the RHOA-G17V variant. RHOA-G17V-expressing T cells did not exhibit enhanced motility compared to empty-vector-transfected cells in microchannels, a 3D collagen gel, or primary human lymphatic tissue. Cells of the HH cell line expressing RHOA-G17V had an increased number of cells with cleaved collagen compared with the empty-vector-transfected cells. Therefore, we hypothesized that the early spread of AITL tumor cells may be related to remodelling of the extracellular matrix. Accordingly, we observed a significant negative correlation between the relative area of collagen in histological sections from 18 primary AITL and the allele frequency of the RHOA-G17V mutation. In conclusion, our results suggest that the characteristic presentation of AITL with early, widespread dissemination of lymphoma cells is not the result of an enhanced migration capacity due to the RHOA-G17V mutation; instead, this feature may rather be related to extracellular matrix remodelling.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Introduction: Peripheral T-cell lymphomas (PTCL) are a rare and heterogeneous group of malignancies that share a unifying feature of epigenetic dysregulation. Recent evidence suggests that PTCL, unlike other forms of cancer or even lymphoma, exhibits a marked vulnerability to hypomethylating agents (HMAs) alone and especially in combination with HDAC inhibitors. HMAs like azacitidine (AZA) and decitabine (DAC) have been shown to reverse transcriptional repression secondary to hypermethylation. Cladribine (CLAD) is FDA-approved for the treatment of hairy cell leukemia and is postulated to inhibit both DNA and histone methylation. Here, we sought to define the mechanistic differences between different DNA HMAs in order to inform a rationale on the optimal combinations that might exploit the epigenetic vulnerabilities of PTCL. Methods: Cell viability, caspase activity assay, and western blotting (WB) were performed on a panel of T-cell lymphoma cell lines to identify the effects of AZA/DAC/CLAD on cell survival, apoptosis, and DNA methyltransferase (DNMT) levels. Liquid chromatography-based mass spectrometry (LC-MS) was done to quantify 5-methyl cytosine (5-mC) levels. Results: Cell viability analysis confirmed that the dose and time-dependent sensitivity of the six PTCL cell lines differed following exposure to AZA/DAC/CLAD, where CLAD showed the lowest IC50 value (0.1–1 µM) across all cell lines, followed by AZA (IC50: 1–10 µM), and DAC had the least effect on cell viability (IC50: >100 µM, except T-ALL). A differential threshold of caspase activation was observed across the PTCL cell lines where CLAD showed the most superior caspase activity leading to the highest apoptotic potential. However, WB analysis showed that after 24 hours of treatment, DNMT1 and DNMT3A protein levels were significantly depleted at low concentrations of DAC (<0.01 µM) compared to AZA whereas CLAD did not affect the DNMT1 and DNMT3A levels. LC-MS-based quantification of 5-mC showed a similar relationship in methylation, with initial changes observed at doses >0.01 μM of DAC and >0.1 μM of AZA/CLAD. Taking the short half-life of AZA/DAC into account, cell viability assays with daily addition of AZA/DAC showed increased cell cytotoxicity for AZA/DAC treated samples, which was comparable to CLAD. Ongoing analyses of gene expression and metabolism of the universal methyl donor S-adenosylmethionine (SAM) will help to understand the mechanistic difference between these HMAs. Conclusions: These data suggest that the HMAs have a distinct mechanism of action for hypomethylation. While AZA/DAC induces hypomethylation by depletion of DNMTs, CLAD acts in a DNMT depletion-independent pathway. A mechanistic understanding of AZA/DAC/CLAD will inform how best to use them in clinic as well as assist in the strategic development of biological correlates to further support their therapeutic application. The research was funded by: Translational Orphan Blood Cancer Research Initiative Fund and RO1 # FD-R-006814-01. Keywords: Genomics, Epigenomics, and Other -Omics, Molecular Targeted Therapies No conflicts of interests pertinent to the abstract.