Donor Peripheral Blood Mononuclear Cells Research Articles

Effects of coagulation factors on bone cells and consequences of their absence in haemophilia a patients

Haemophilia is associated with reduced bone mass and mineral density. Due to the rarity of the disease and the heterogeneity among the studies, the pathogenesis of bone loss is still under investigation. We studied the effects of coagulation factors on bone cells and characterized in a pilot study the osteoclastogenic potential of patients’ osteoclast precursors. To evaluate the effect of coagulation factors on osteoclasts, we treated Healthy Donor-Peripheral Blood Mononuclear Cells (HD-PBMC) with Factor VIII (FVIII), von Willebrand Factor (VWF), FVIII/VWF complex, activated Factor IX (FIXa), activated Factor X (FXa) and Thrombin (THB). FVIII, VWF, FVIII/VWF, FXa and THB treatments reduced osteoclast differentiation of HD-PBMC and VWF affected also bone resorption. Interestingly, PBMC isolated from patients with moderate/severe haemophilia showed an increased osteoclastogenic potential due to the alteration of osteoclast precursors. Moreover, increased expression of genes involved in osteoclast differentiation/activity was revealed in osteoclasts of an adult patient with moderate haemophilia. Control osteoblasts treated with the coagulation factors showed that FVIII and VWF reduced ALP positivity; the opposite effect was observed following THB treatment. Moreover, FVIII, VWF and FVIII/VWF reduced mineralization ability. These results could be important to understand how coagulation factors deficiency influences bone remodeling activity in haemophilia.

TLR7/8 Activation in Immune Cells and Muscle by RNA-Containing Immune Complexes: Role in Inflammation and the Pathogenesis of Myositis.

Activation of endosomal toll-like receptors (TLRs) is one possible driver of inflammation in idiopathic inflammatory myopathies (IIM). We investigated the potential contribution of TLR7 and TLR8 to IIM pathogenesis. Activation of TLR7/8 in healthy donor peripheral blood mononuclear cells (PBMCs) by immune complexes from patients with IIM and lupus was tested. Autoantibody profiling of patient IgG samples was performed using a 1581-antigen array. TLR7 and/or TLR8 activation by RNA molecules associated with autoantibodies was assessed. Gene expression in human myoblasts and satellite cells following treatment with supernatants from TLR7/8-activated PBMCs was evaluated by NanoString. C57BL/6 mice were dosed intramuscularly with the TLR7/8 agonist R848 and single-cell RNA-sequencing was performed on the muscle to ascertain the cell types responding to TLR7/8 activation and the downstream effects. Overall, 69 patients with IIM were included with representation of dermatomyositis (DM), polymyositis (PM), and inclusion body myositis (IBM) subsets. Immune complexes from patients with IIM, as well as autoantibody-associated RNAs His-tRNA, Y1, Y4 and U1, activated PBMCs to produce IFN-α and IL-6 via TLR7/8. Several canonical (Ro60, Ro52, HIST1H4A) and novel (IL-36RN) autoreactivities correlated highly with TLR7/8 activation. Supernatants from TLR7/8-activated PBMCs had a negative impact on human myoblasts and satellite cells. Endothelial cells were activated by R848 in mouse muscle in vivo, in addition to immune cells such as monocytes and macrophages. Our results suggest that patients with IIM have autoantibodies in their blood causing TLR7/8 activation, which leads to inflammation in muscles with potential deleterious effects.

Development of anex vivo patient-derived tumor model (PDTM) to assess the tumor microenvironment in renal cell carcinoma (RCC)

Abstract Background With the rise of immune checkpoint inhibitors (ICIs) as the primary treatment option for metastatic RCC, investigating the role of T cells within the tumor microenvironment (TME) is a critical component of understanding both treatment response and resistance. Prior efforts, including single-cell transcriptomic approaches, have provided an important landscape of T cell transcriptional phenotypes. However, these immuno-profiling efforts require validation through functional interrogation of the TME to facilitate the development of novel immunomodulatory therapies. Thus, we established a patient derived tumor model (PDTM) system to directly assess the effect of inhibitory immune interactions on T cell function and anti-tumor activity in the RCC TME. In this initial proof-of-concept study, we evaluated T cell activation in the RCC TME using the PDTM system. Methods Fresh tumor samples were obtained from surgical resections of RCC at Yale-New Haven Hospital. The tumor was minced to ~1-3 mm³ pieces and suspended in an air-liquid interface system, consisting of tumor fragments embedded in a collagen matrix on an insert with a semi-permeable membrane, exposed to culture media. The tumor fragment and matrix suspension were carefully pipetted onto the Millicell insert, which served as the top layer. The PDTM setup includes an inner dish containing the bottom gel layer and the tissue-containing top layer. To complete the assembly, 1.5 ml of DMEM media with or without an anti-CD3 monoclonal antibody (aCD3mAb) and 500 nM of anti-PD-1 monoclonal antibody (aPD1mAb) was added to the outer dish surrounding the insert. Results We successfully optimized PDTM experimental workflows for culture, dissociation, and analysis using immunohistochemistry (IHC), flow cytometry (FCM), and enzyme-linked immunosorbent assays (ELISA). Hematoxylin and eosin (H&E) staining and IHC showed that the TME cellular architecture and immune cell composition was broadly preserved during the three day experimental period. Using FCM to analyze the dissociated tumor samples, we identified well-preserved CA9+ tumor cells, CD4+ and CD8+ T cell populations, CD4+CD25+ regulatory T cells, CD56+ natural killer cells, CD20+ B cells, and CD14+CD11b+ myeloid subsets including monocytes and CD163-/+macrophages. Among the T cells, we detected PD1+, LAG3+, TIM3+, and TIGIT+ cells. For dose-response analysis of aCD3mAb, we observed that stimulation with 0.025 ng/mL aCD3mAb for T cells from healthy donor peripheral blood mononuclear cells (PBMCs) yielded significant but non-saturating levels of interferon gamma (IFN-γ) production as quantified by ELISA. We tested the effect of the anti-PD-1 antibody on PDTM under the low-dose of aCD3mAb, and importantly, found that treatment of the PDTM with aPD1mAb resulted in more activated CD8 T cells and higher IFN-γ production than the control samples. Conclusions Through optimization of assays evaluating T cell cytokine production, we were able to assess multiple axes of T-cell function in the RCC TME. This study revealed that our PDTM system preserves the RCC TME for functional interrogation. Furthermore, our system for assessing T cell phenotype and cytokine production successfully demonstrated the activity of PD-1 blockade ex vivo. Taken together, this novel ex vivo PDTM system has extensive applications in the study of RCC, including assessing the impact of ICIs on T cell function. DOD CDMRP Funding: yes

Pharmaceutical targeting of the cannabinoid type 1 receptor impacts the crosstalk between immune cells and islets to reduce insulitis in humans

Aims/hypothesisInsulitis, a hallmark of inflammation preceding autoimmune type 1 diabetes, leads to the eventual loss of functional beta cells. However, functional beta cells can persist even in the face of continuous insulitis. Despite advances in immunosuppressive treatments, maintaining functional beta cells to prevent insulitis progression and hyperglycaemia remains a challenge. The cannabinoid type 1 receptor (CB1R), present in immune cells and beta cells, regulates inflammation and beta cell function. Here, we pioneer an ex vivo model mirroring human insulitis to investigate the role of CB1R in this process.MethodsCD4+ T lymphocytes were isolated from peripheral blood mononuclear cells (PBMCs) from male and female individuals at the onset of type 1 diabetes and from non-diabetic individuals, RNA was extracted and mRNA expression was analysed by real-time PCR. Single beta cell expression from donors with type 1 diabetes was obtained from data mining. Patient-derived human islets from male and female cadaveric donors were 3D-cultured in solubilised extracellular matrix gel in co-culture with the same donor PBMCs, and incubated with cytokines (IL-1β, TNF-α, IFN-γ) for 24–48 h in the presence of vehicle or increasing concentrations of the CB1R blocker JD-5037. Expression of CNR1 (encoding for CB1R) was ablated using CRISPR/Cas9 technology. Viability, intracellular stress and signalling were assayed by live-cell probing and real-time PCR. The islet function measured as glucose-stimulated insulin secretion was determined in a perifusion system. Infiltration of immune cells into the islets was monitored by microscopy. Non-obese diabetic mice aged 7 weeks were treated for 1 week with JD-5037, then euthanised. Profiling of immune cells infiltrated in the islets was performed by flow cytometry.ResultsCNR1 expression was upregulated in circulating CD4+ T cells from individuals at type 1 diabetes onset (6.9-fold higher vs healthy individuals) and in sorted islet beta cells from donors with type 1 diabetes (3.6-fold higher vs healthy counterparts). The peripherally restricted CB1R inverse agonist JD-5037 arrested the initiation of insulitis in humans and mice. Mechanistically, CB1R blockade prevented islet NO production and ameliorated the ATF6 arm of the unfolded protein response. Consequently, cyto/chemokine expression decreased in human islets, leading to sustained islet cell viability and function.Conclusions/interpretationThese results suggest that CB1R could be an interesting target for type 1 diabetes while highlighting the regulatory mechanisms of insulitis. Moreover, these findings may apply to type 2 diabetes where islet inflammation is also a pathophysiological factor.Data availabilityTranscriptomic analysis of sorted human beta cells are from Gene Expression Omnibus database, accession no. GSE121863, available at https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSM3448161.Graphical

Generation of a human iPSC cell line (MUSIi017-A) from a donor with O negative blood type

The Rh-negative type O blood group (O Rh-) is considered a universal donor for emergency blood transfusions. Due to the constant shortage of this rare blood group, the production of blood cells from iPSCs derived from the O Rh- donor could potentially serve as a limitless blood source for transfusions. In this report, we establish a MUSIi017-A iPSC line from peripheral blood mononuclear cells of a healthy donor with the O Rh- blood group. The established iPSC line exhibited a normal karyotype, showed identical STR compared to donor peripheral blood mononuclear cells, and could differentiate to all three germ layers.

Abstract LB074: Preclinical development of API-192: An engineered CAR-NKT allogeneic cell therapy targeting CD19 and CD20 for the treatment of B-cell malignancies

Abstract Autologous chimeric antigen receptor (CAR)-T therapies have elicited high rates of durable complete responses in B cell lymphomas. Unfortunately, disease progression, manufacturing failures, and prohibitive costs highlight the need for an alternative source of cells that would provide a consistent and readily available therapy for patients. The “Appia Cells Utilized for Allogeneic” (ACUA) platform is an innovative process that differentiates cord blood-derived CD34+ hematopoietic stem and progenitor cells into large numbers of natural killer T (NKT) cells to support off-the-shelf treatment. NKT cells express an invariant T cell receptor (iTCR) and are naturally non-alloreactive, making them an ideal cell type for an allogeneic product. The ACUA platform circumvents the challenge of expanding NKT cells from the periphery where the cells comprise less than 1% of T cells. API-192 is an ACUA-derived, NKT cell product engineered to express dual CARs targeting CD19 and CD20 to prevent tumor antigen escape. At research scale, API-192 is a highly pure product (>90% iTCR+ 19CAR+ 20CAR+) that secretes soluble interleukin-15 for improved expansion and persistence. The transgenic iTCR is not expressed above physiologic levels and upon engagement, API-192 proliferates in response to and is cytotoxic against CD1d+ tumor cells in a ligand-dependent manner. In response to Raji and Nalm6 tumor cells, API-192 secretes pro-inflammatory cytokines, proliferates, and is cytotoxic in a dose- and CAR-dependent manner. API-192 can also control multiple rounds of tumor cell rechallenge in vitro. Using human tumor xenograft mouse models, we show that API-192 expands, controls tumor growth, and prolongs survival. Furthermore, API-192 persists in the periphery, enabling control of a tumor rechallenge at 70 days after initial dosing of effector cells. Indicative of a favorable immunogenic profile, API-192 expresses lower levels of MHC I and MHC II molecules relative to conventional CAR-T cells and elicits less interferon (IFN)-γ release by NK and T cells in a mixed lymphocyte reaction (MLR) assay. To address a theoretical concern that endogenous TCRαβ rearrangement could occur during the ACUA process, we performed genomic DNA based TCR sequencing to quantify the level of TCRα or TCRβ rearrangement and preliminary data suggested negligible levels (<0.2%). Using a MLR assay, we demonstrate that compared to conventional CAR-T cells, API-192 secretes minimal levels of IFN-γ in response to co-culture with healthy donor peripheral blood mononuclear cells, consistent with a low graft vs host risk. In an autonomous growth assay, API-192 expands at a low level and subsequently contracts, suggesting a lack of dysregulated growth. Collectively, these results demonstrate the favorable manufacturability, potency, and safety of API-192 and its potential as a novel allogeneic therapy. Citation Format: Lanny Gov, Jiaji Yu, Maha Qubain, Saige L. Pompura, Sean D. Allen, Michael A. Christopher, Jeff Wiezorek. Preclinical development of API-192: An engineered CAR-NKT allogeneic cell therapy targeting CD19 and CD20 for the treatment of B-cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB074.

Urinary Mitochondrial DNA Induces an Inflammatory Response in Peripheral Blood Mononuclear Cells

Background: Mitochondria are semiautonomous cell organelles having its own nucleic acid. Mitochondrial DNA (Mt-DNA) remain in hypomethylated (CpG) state and impose an immunogenic response by binding to the toll-like receptor (TLR-9) through the NF-kB pathway. Innate immune cells recognize the hypomethylated pattern of mt-DNA and quickly trigger the innate immune response. The immunomodulatory effects of urinary mt-DNA derived from renal transplant recipients with COVID-19-associated acute kidney injury (AKI) have not been studied. Materials and Methods: Healthy donor peripheral blood mononuclear cell (PBMC) was cultured with the urinary Mt-DNA derived from the renal transplant recipients, who previously developed SARS-CoV-2 infection associated AKI. Cell activation was measured by the flow cytometry. In cell pellets, interleukin IL-6, IL-10, and Myd88, TLR-9 mRNA transcript expression was measured by the reverse transcription polymerase chain reaction. The IL-6 and IL-10 cytokine levels were measured by the enzyme-linked immunosorbent assay in culture supernatants. Results: The urinary mitochondrial DNA (umt-DNA) significantly induces the activation of > 75% of PBMCs. The m-RNA transcript expression of the inflammatory gene in control versus umt-DNA treated PBMCs was for IL-6 (0.99 ± 0.05 vs. 2.18 ± 1.15 au; P = 0.004), MYD88 was (1.00 ± 0.05 vs. 1.55 ± 0.31; P < 0.001), TLR-9 (1.00 ± 0.05 vs. 3.33 ± 1.37 au; P < 0.001) was upregulated, and the IL-10 (1.00 ± 0.13 vs. −1.73 ± 0.58; P < 0.001) level was downregulated. However, in PBMC culture supernatants, IL-6 level in control versus umt-DNA-treated groups were (37.50 ± 13.79 vs. 186.9 ± 15.50 pg/mL; P < 0.001), which was significantly higher in umt-DNA-treated groups and the IL-10 (8.80 ± 2.16 vs. 7.60 ± 3.12 pg/mL; P = 0.32) level was similar between the control- and umt-DNA-treated groups. Conclusions: Urinary Mt-DNA significantly induces the inflammatory cytokine IL-6 secretion from the PBMCs through the Myd88-dependent pathway.

Analysis and Development of Antigen-specific T Cells Derived from Peripheral Blood Mononuclear Cells of Healthy Donors.

Adoptive cell therapy using antigen-specific T cells is a promising treatment modality for cancer patients. Various methods to isolate specific T cells and identify corresponding T cell receptor (TCR) sequences are known. This study aimed to identify antigen-specific TCR from T cells isolated using carboxyfluorescein succinimidyl ester (CFSE), which marks proliferating activated T cells. CFSE stained healthy donor peripheral blood mononuclear cells (PBMCs) were treated with cytomegalovirus (CMV) or Epstein-Barr virus (EBV) peptides for seven days. Then, proliferating T cells with decreased CFSE staining were isolated and single cell VDJ sequencing was performed on isolated T cells to identify antigen-specific TCRs. As antigen-specific TCR candidates, ten TCR clones were selected for the CMV antigen and five for the EBV antigen. The reactivity of ten CMV TCR-transduced T cells and one EBV TCR-transduced T cell toward T2 cells pulsed with CMV or EBV peptide was confirmed via NFAT-luciferase, IFN-γ ELISA, and cytotoxicity assays. Identification of antigen-specific TCRs with CFSE staining is a valid method for the development of effective immunotherapy. The identified CMV- or EBV-specific TCRs can be used for adoptive cell therapy to treat cancer.

Abstract 7045: RNA sequencing approaches enable tissue specific B and T cell gene expression and immune repertoire profiling

Abstract The adaptive immune system defends the human body from pathogens through the recognition ability of antigen receptors from B and T cells. Different organs play various immune function roles, and therefore present varied B and T cell gene expression and immune repertoire profiles. Abnormality of these profiles may reflect immunological disorder, presence of neoplastic tissue, or response to infectious agent. High-throughput sequencing technology has facilitated the understanding of gene expression and related cell functions, but in-depth understanding of B and T cell phenotype and clonotype profiling is an emerging application that has yet to take full advantage of sequencing technology for diagnosis and prognosis of disease. Here, we share results of RNA sequencing of immune system tissues; including B cell and T cell specific gene expression and full-length immune repertoire profiling. Total RNA was extracted from various tissue samples including healthy donor peripheral blood mononuclear cells (PBMC), lymph nodes, bone marrow, spleen, thyroid, thymus and colon, as well as diseased PBMC and colon samples. RNA-seq and Immune-seq libraries were made from these samples and sequenced on Illumina NextSeq2000. Gene expression analysis and immune repertoire profiling from RNA-seq data were performed using edgeR and TRUST4. Immune repertoire sequencing data was processed using pRESTO and IgBlast. We correlated RNA-seq with Immune-seq results for B-cell receptor and T-cell receptor clonotypes. Differential expression and clonotype profiling comparisons were also performed between normal and diseased RNA samples. The effect of reference on immune repertoire detection sensitivity and accuracy was further investigated by comparing IMGT reference and AIRR-C Human IG Reference Sets. This study has identified tissue specific B/T cell phenotype and clonality patterns that relate to tissue functions and disease progression. RNA-seq enables highly multiplex immunophenotyping which is traditionally performed by flow cytometry. RNA-seq can detect high-abundant clones that correlate with Immune-seq, with the latter targeted approach providing more in depth clonality signatures. References comparison results show the importance of continued community effort to develop more representative and accurate immunorepertoire germ line references for clonotype annotation in diverse populations. Integrating both RNA sequencing and immune repertoire sequencing approaches allows accurate phenotype and clonotype determination for immune landscape in various tissues. Citation Format: Chen Song, Evan Janzen, Tessa Devoe, Ariel Erijman, Gautam Naishadham, Li Song, Bradley W. Langhorst. RNA sequencing approaches enable tissue specific B and T cell gene expression and immune repertoire profiling [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 7045.

Abstract 3613: Screening iPSC lines for optimal characteristics of differentiation into immune effector cells for clinical programs

Abstract Engineered Induced Pluripotent Stem Cells (iPSCs) are the core foundational technology for Century Therapeutics. In our constant effort to identify iPSC lines with diverse functional activity, we have derived a large panel of clinical-grade peripheral blood mononuclear cell (PBMC)-derived and gamma-delta T cell-derived IPSC lines (PiPSCs and TiPSCs, respectively) from multiple donors. These lines have been screened by multiple criteria to select the top lines for clinical development in our iPSC-derived NK (iNK) and T cell (iT) programs. Initial screening included in-depth genomic and transcriptomic analysis of PiPSC and TiPSC lines to eliminate those with any unwanted genetic abnormalities, as well as to build multi-omics datasets for correlating gene polymorphisms and transcript variation to function. Next, all lines were differentiated to iNK or iT effector cells, and phenotypically characterized throughout the differentiation process. In those studies, 86.5% of PiPSCs and 69.2% of TiPSCs lines were compatible with our protocols and able to be successfully differentiated and acquire NK cell and gamma delta T cell phenotypes respectively. Yield and lineage commitment (%CD56+ for NK cells and %CD3+ for T cells) variability was found to be higher across clones than donors in this initial analysis. Finally, we evaluated in vitro cytotoxicity, cytokine secretion, and persistence for all clones that met differentiation thresholds (>90% lineage commitment). As part of that evaluation, 39 PiPSCs lines were differentiated to iNK cells. Cytotoxicity against tumor lines was observed to be consistently between 85-100% at an effector to target ratio of 1:1. Although no trends in functionality were found to be associated with the PBMC donor, iPSC lines derived from CD34+ enriched PBMCs exhibited higher levels of innate killing as compared to those derived from bulk PBMCs. For this presentation, we will present genetic, transcriptomic, and phenotypic correlations with favorable differentiation and functional efficacy and illustrate how our screening process enables efficient selection of founder lines with the highest therapeutic potential for allogeneic cell therapies. Citation Format: Barry A. Morse, Amarin Cogburn, Alex Chialastri, Matthew S. Hall, Ohad Manor, Andriana Lebid, Dae Hwan Kim, Luis Cocka, Daniel J. Perry, Ciara Budd, Aarti Kolluri, Liam Campion, Toshinobu Nishimura, Michael Naso, Hyam Levitsky. Screening iPSC lines for optimal characteristics of differentiation into immune effector cells for clinical programs [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 3613.

Abstract 4996: Analysis of the effect of eribulin on tumor immunity against triple-negative breast cancer

Abstract Purpose: Chemotherapeutic agents may induce immunomodulatory effects on immune cells and cancer cells in patients with triple negative breast cancer (TNBC). Recent studies have demonstrated that absolute lymphocyte count in peripheral blood can predict response to eribulin in patients with breast cancer, suggesting that eribulin have some favorable effects on immune cells. However, there have been no reports demonstrating the mechanisms of how eribulin affects the immune cells of patients with breast cancer. This study aimed to analyze the effect of eribulin on T cells in vitro and in vivo. Materials & Methods: Using human peripheral blood mononuclear cells (PBMCs) from healthy donors and patients with TNBC, we investigated the effects of eribulin on proliferation of these cells, changes in the expression of surface markers, and antitumor effects on TNBC cells. Three TNBC cell lines (MDA-MB-231, Hs578T, MDA-MB-157) were used in this study. Human PBMCs were activated by CD3/CD28 stimulation in vitro for six days and analyzed for T-cell surface markers by flow cytometry. For three patients with TNBC who underwent eribulin treatment, blood was collected at baseline and on days 8, 22, and 64 after treatment, and PBMCs were isolated, and analyzed by flow cytometry. Results: The proliferation of activated CD8+ T cells from healthy donors and patients was facilitated when cultured with 1nM of eribulin compared to the control. Moreover, eribulin significantly decreased CD4/8 ratio in T cells (p< 0.05). In PBMCs from healthy donors, the frequency of CD45RA+ CD45RO- cells and CCR7+ cells in CD8+ T cells was significantly increased by eribulin treatment (p< 0.05). Furthermore, eribulin significantly increased CD127+ KLRG1- cells (memory precursor effector cells) and TCF1+ cells in CD8+ T cells (p< 0.01). Furthermore, the anti-tumor effect of activated T cells from PBMCs of healthy donors and patients with TNBC was enhanced when cultured with eribulin in all three TNBC cell lines compared to control, and IFNγ+ CD8+ T cells were significantly increased by eribulin treatment (p< 0.05). However, in TNBC patients treated with eribulin in clinical practice, there were no significant changes in the CD4/8 ratio, the frequency of CD45RA+ cells or CCR7+ cells in CD8+ T cells before and after treatment of eribulin. Conclusions: Our findings suggest that eribulin can facilitate the proliferation of CD8+ T cells and potentiates T cell-mediated anti-tumor activity against triple-negative breast cancer cells in vitro. Further analysis of the effects of eribulin on TNBC cells and immune cells in vivo is required, and we continue to analyze immunomodulation in patients treated with eribulin. Citation Format: Shimizu Tadafumi, Takaaki Oba, Ken-ichi Ito. Analysis of the effect of eribulin on tumor immunity against triple-negative breast cancer [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 4996.

Abstract 44: A novel, codon-based method to modulate off-tumor toxicity of chimeric antigen receptor (CAR) T cells

Abstract Chimeric antigen receptor (CAR) T cell therapies for hematologic malignancies, while promising and efficacious, can also result in a variety of adverse effects. Of note, on-target, off-tumor toxicity is one adverse effect that continues to limit the safety and efficacy of CAR-T cells and has even led to life-threatening or fatal outcomes in patients (Morgan et al. 2010.). To address this, we have developed a unique, codon-based approach by replacing strategically selected codons within CAR non-antigen binding domains with their rare synonymous isoforms. Hoekema et al. (1987) reported the ability of synonymous rare codons to alter gene and protein expression in other model systems. In CAR-T cells, we aim to use this novel, codon-based approach to fine tune and modulate CAR-T cell expression and function to elicit full on-tumor activity while lessening off-tumor toxicity. In our approach, we replaced specific endogenous codons within the non-antigen binding domains of Hu8F4-CAR, a TCR-like 2nd generation CAR developed by our group which targets the leukemia-associated antigen PR1/HLA-A2 (Ma et al. 2016.). Briefly, we created variants of Hu8F4-CAR containing rare codon substitutions in two subtypes: intracellular-based (type 1) and combined extracellular- and intracellular-based (type 2). Each variant subtype (type 1 or 2) had either between 6 and 30 or 27 and 57 rare codons introduced, respectively. Expression profiling and functional assessment of the Hu8F4-CAR variants was assessed in the Jurkat mutant cell line (J.RT3-T3.5) or human primary healthy peripheral blood mononuclear cells (PBMCs) that were enriched for T cells, respectively. Expression profiling results show that surface expression is reduced in J.RT3-T3.5 cells when assessed by flow cytometry by 1-1.5-fold compared to unmodified Hu8F4-CAR. When evaluated by immunoblotting, novel lower molecular weight bands emerge only in rare codon-modified variants, suggesting that rare codons may have altered translational or post-translational processing leading to truncated CAR protein isoforms (30, 45, or 60kDa vs 73kDa for unmodified Hu8F4-CAR), which may contribute to reduced cell surface CAR expression. Furthermore, we have conducted in vitro functional testing of the rare codon-modified variants and show reduced activity against non-malignant off-tumor targets that express PR1 and/or HLA-A2 including healthy donor PBMCs, mobilized hematopoietic cells, and bone marrow. Importantly, in addition to reduced off-tumor activity against healthy myeloid cells, rare codon-modified variants preserve their activity against on-tumor target cells, including the U937-A2+ cell line and primary acute myeloid leukemia. Altogether, these results suggest that our approach can modulate CAR expression and functionality creating a novel methodology to reduce the likelihood of off-tumor adverse effects typically associated with CAR therapies. Citation Format: Rolando A. Vedia, Sijie Lu, Anne V. Philips, Anna Sergeeva, Lisa S. St John, Karen Clise-Dwyer, Gheath Alatrash, Jeffrey J. Molldrem. A novel, codon-based method to modulate off-tumor toxicity of chimeric antigen receptor (CAR) T cells [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 44.

Abstract 111: Establishing orthotopic renal cell carcinoma xenograft in PBMC-humanized immunodeficient NSG-MHC I/II double knock-out mice

Abstract Clear cell renal cell carcinoma (ccRCC), the predominant histological subtype of RCC, is highly correlated with immune cells, an association that is linked to a worse prognosis. Our study aimed to establish an orthotopic ccRCC mouse model reconstituted with human peripheral blood mononuclear cells (PBMCs) and implanted with human ccRCC SKRC-59 cells under the kidney capsule in immunodeficient NSG-MHC I/II double knock-out (DKO) mice. The study was conducted using two experimental designs to optimize humanization and tumor formation. In the first experimental design, the mice were engrafted with SKRC-59 cells under the left kidney capsule 24 hours post-irradiation on study day 0. The PBMCs were then injected intravenously on study day 9. The second experimental design involved irradiating mice on study day -1, followed by engraftment with PBMCs either perfectly (6/6) or partially (3/6) matched human leukocyte antigens (HLA) with the tumors. Subsequently, SKRC-59 cells were placed under the kidney capsule on study day 0. Daily post-operative observations were conducted for six days following surgery to ensure the well-being of the mice. Tumor burden was assessed twice weekly using an in vivo imaging system, along with monitoring body weights and clinical signs. The humanization rates were evaluated 7, 14, and 21 days post-PBMC engraftment, as well as at the end of the study, using peripheral blood. Approximately 5 to 6 weeks post-tumor implantation, the mice were euthanized, and both left and right kidneys were collected and weighed for further analysis. The humanization rates were significantly higher when the PBMCs were engrafted on the same day as irradiation compared to 10 days post-irradiation. The PBMC humanization, and HLA-type PBMC donors did not affect tumor burden. Additionally, we found that distant metastasis in the lungs developed in several mice. Using flow cytometry and immunohistochemistry (IHC) to analyze tumor infiltrating leukocytes (TILs), a predominant number of CD3+ T cells were found in human CD45+ TILs, indicating that this model could be useful for evaluating T cell-mediated immunotherapies. Moreover, lympho-myeloid aggression (LMA) was observed in this peripheral blood leukocytes (PBL) mouse model, showing early stage tertiary lymphoid structures (TLS), which potentially provides a powerful tool to recapitulate TLS formation and study associated mechanisms and therapies. Our study demonstrated the growth of ccRCC SKRC-59 tumors under the renal capsule and observed TILs and metastatic patterns in PBMC humanized DKO mice. This PBMC-humanized orthotopic ccRCC xenograft model can recapitulate tumor microenvironment (TME), and be potentially used to assess the safety and efficacy of various immunotherapeutics. Citation Format: Wonyoung Kang, Yufei Wang, Yasmin N. Laimon, Oanh Pham, Ben Matran, Lauren Bottoms, Sheng Khang, Hsien-Chi Yuan, Nithyassree Murugan, Aseman B. Sheshdeh, Li-chin Yao, Jiwon Yang, Mingshan Cheng, Sabina Signoretti, Wayne A. Marasco, James G. Keck. Establishing orthotopic renal cell carcinoma xenograft in PBMC-humanized immunodeficient NSG-MHC I/II double knock-out mice [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 111.

Abstract 4191: Delayed onset of GvHD in PBMC humanized NCG-B2m KO mice provides an enhanced model for oncology studies

Abstract Humanized mice are specialized animal models incorporating components of the human immune system. These models are valuable tools for assessing the efficacy of human immunotherapies on tumors. Humanized mice are created by injecting human CD34+ hematopoietic stem cells (HSCs) or human peripheral blood mononuclear cells (PBMCs) into an immunodeficient mouse. PBMC humanized (HuPBMC) mice engraft within a few weeks and can recapitulate a robust human T cell population. One challenge when using HuPBMC mice is the onset of graft versus host disease (GvHD), limiting their lifespan compared to hCD34+ HSC humanized mice. The onset of GvHD varies in the HuPBMC model depending on the donor cells. The development of xenogeneic GvHD is dependent on the expression of major histocompatibility complex (MHC) on host cells and lowering MHC expression can delay the onset of GvHD.NCG-B2m KO mice lack beta-2 microglobulin, a component of MHC I, and have lower cell surface expression of MHC I molecules. This leads to a decrease in recognition of host cells by human immune cells. Here we compared the onset of GvHD between HuPBMC NCG-B2m KO mice and HuPBMC NCG mice. PBMC donor variability was also compared between the two PBMC humanized models by evaluating multiple donors and assessing additional collections from the same donor. After the PBMC engraftment was characterized, HuPBMC NCG mice and HuPBMC NCG-B2m KO mice were enrolled in tumor studies comparing outcomes and tumor growth kinetics in mice treated with human immune checkpoint blockade therapy.NCG and NCG-B2m KO mice were injected with 1x107 PBMCs from individual donors. Animals were weighed three times a week to monitor for changes in body weight and general health status. Peripheral blood was collected at day 10, 20, 30, 40, 60 and 90 post injection for flow cytometry screening of human immune cell engraftment (hCD45+, hCD3+, hCD4+ and hCD8+). Human PBMCs isolated from additional collections from the same donors were also injected into both NCG-B2m KO mice and NCG mice and flow cytometry was performed. HuPBMC NCG-B2m KO mice survived longer than HuPBMC NCG mice allowing for the potential use in longer term tumor studies before the results are confounded by GvHD. PBMC humanized mice are an important model for translational research using immunotherapies and the PBMC humanized NCG-B2m KO model provides an expanded study window ideal for oncology studies. Citation Format: Steven Bronson, David Harris, Anya Avrutskaya, Christoph Eberle, Jenny Rowe. Delayed onset of GvHD in PBMC humanized NCG-B2m KO mice provides an enhanced model for oncology studies [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 4191.

Disrupting pro-survival and inflammatory pathways with dimethyl fumarate sensitizes chronic lymphocytic leukemia to cell death

Microenvironmental signals strongly influence chronic lymphocytic leukemia (CLL) cells through the activation of distinct membrane receptors, such as B-cell receptors, and inflammatory receptors, such as Toll-like receptors (TLRs). Inflammatory pathways downstream of these receptors lead to NF-κB activation, thus protecting leukemic cells from apoptosis. Dimethyl fumarate (DMF) is an anti-inflammatory and immunoregulatory drug used to treat patients with multiple sclerosis and psoriasis in which it blocks aberrant NF-κB pathways and impacts the NRF2 antioxidant circuit. Our in vitro analysis demonstrated that increasing concentrations of DMF reduce ATP levels and lead to the apoptosis of CLL cells, including cell lines, splenocytes from Eµ-TCL1-transgenic mice, and primary leukemic cells isolated from the peripheral blood of patients. DMF showed a synergistic effect in association with BTK inhibitors in CLL cells. DMF reduced glutathione levels and activated the NRF2 pathway; gene expression analysis suggested that DMF downregulated pathways related to NFKB and inflammation. In primary leukemic cells, DMF disrupted the TLR signaling pathways induced by CpG by reducing the mRNA expression of NFKBIZ, IL6, IL10 and TNFα. Our data suggest that DMF targets a vulnerability of CLL cells linked to their inflammatory pathways, without impacting healthy donor peripheral blood mononuclear cells.

T-cell help in the tumor microenvironment enhances rituximab-mediated NK-cell ADCC

AbstractRituximab (RTX) and other monoclonal antibodies (mAbs) that bind directly to malignant cells are of great clinical value but are not effective for all patients. A major mechanism of action of RTX is antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells. Prior in vitro studies in our laboratory demonstrated that T cells contribute to maintaining the viability and cytotoxic potential of NK cells activated by anti-CD20–coated target B cells. Here, we conducted studies using a novel mouse model and clinical correlative analysis to assess whether T-cell help contribute to RTX-mediated NK-cell ADCC in the tumor microenvironment (TME) in vivo. A humanized mouse model was developed using Raji lymphoma cells and normal donor peripheral blood mononuclear cells that allows for control of T-cell numbers in the lymphoma TME. In this model, NK-cell viability and CD16 and CD25 expression dropped after RTX in the absence of T cells but increased in the presence of T cells. RTX therapy was more effective when T cells were present and was ineffective when NK cells were depleted. In patients with indolent lymphoma, fine needle aspirates were obtained before and ∼1 week after treatment with a RTX-containing regimen. There was a strong correlation between CD4+ T cells as well as total T cells in the pretherapy TME and an increase in NK-cell CD16 and CD25 expression after RTX. We conclude that T-cell help in the TME enhances RTX-mediated NK-cell viability and ADCC.

Stimulating T cell responses against patient-derived breast cancer cells with neoantigen peptide-loaded peripheral blood mononuclear cells

Breast cancer stands as a formidable global health challenge for women. While neoantigens exhibit efficacy in activating T cells specific to cancer and instigating anti-tumor immune responses, the accuracy of neoantigen prediction remains suboptimal. In this study, we identified neoantigens from the patient-derived breast cancer cells, PC-B-142CA and PC-B-148CA cells, utilizing whole-genome and RNA sequencing. The pVAC-Seq pipeline was employed, with minor modification incorporating criteria (1) binding affinity of mutant (MT) peptide with HLA (IC50 MT) ≤ 500 nm in 3 of 5 algorithms and (2) IC50 wild type (WT)/MT > 1. Sequencing results unveiled 2513 and 3490 somatic mutations, and 646 and 652 non-synonymous mutations in PC-B-142CA and PC-B-148CA, respectively. We selected the top 3 neoantigens to perform molecular dynamic simulation and synthesized 9–12 amino acid neoantigen peptides, which were then pulsed onto healthy donor peripheral blood mononuclear cells (PBMCs). Results demonstrated that T cells activated by ADGRL1E274K, PARP1E619K, and SEC14L2R43Q peptides identified from PC-B-142CA exhibited significantly increased production of interferon-gamma (IFN-γ), while PARP1E619K and SEC14L2R43Q peptides induced the expression of CD107a on T cells. The % tumor cell lysis was notably enhanced by T cells activated with MT peptides across all three healthy donors. Moreover, ALKBH6V83M and GAAI823T peptides from PC-B-148CA remarkably stimulated IFN-γ- and CD107a-positive T cells, displaying high cell-killing activity against target cancer cells. In summary, our findings underscore the successful identification of neoantigens with anti-tumor T cell functions and highlight the potential of personalized neoantigens as a promising avenue for breast cancer treatment.

Abstract C065: Hematopoietic Progenitor Kinase 1 (HPK1) inhibition enhances antibody secretion, pro-inflammatory cytokine production and proliferation of primary human B cells

Abstract Introduction Immune checkpoint blockade (ICB) therapies have revolutionized cancer treatment, although most approaches have focused solely on enhancing T cell responses. In recent years, it has become clear that augmentation of other immune cell subsets is critical to the overall success of cancer immunotherapy. Recent data show that tumors from patients responding to ICB are infiltrated by B cells and strongly correlated with the formation of tertiary lymphoid structures, highlighting the importance of B cells in promoting and coordinating immunotherapy responses [1,2]. Here, we demonstrate that NDI-101150, a potent and highly selective HPK1 small molecule inhibitor, can enhance B cell activation with the tumor. Experimental Procedures Biochemical and cell-based assays were used to characterize the potency and selectivity of NDI-101150, respectively. Mouse splenocytes and/or human blood collections were used to characterize the effects of NDI-101150 on antibody secretion, cytokine production, and proliferation in purified B cells. CT-26 and EMT-6 syngeneic tumor models were used to study tumor-associated B cell responses in vivo, as well as immunization response to Keyhole Limpet Hemocyanin (KLH) in mice receiving daily oral dosing of NDI-101150. Results In CD19+ human B cells and donor PBMCs (peripheral blood mononuclear cells), NDI-101150 treatment inhibited (>90%) phosphorylation of BLNK, a B cell adapter protein phosphorylated by HPK1 downstream of B cell receptor signaling. In vitro NDI-101150 treatment dose-dependently activated primary human and mouse B cells as evidenced by increased pro-inflammatory cytokine production, enhanced IgG antibody secretion, and increased proliferation. Once daily oral administration of NDI-101150 significantly increased KLH antigen-specific IgM and IgG antibody production upon KLH immunization, increased total circulating antibody levels, and induced significant tumor growth inhibition (TGI) in CT-26 and EMT-6 murine syngeneic models (50% and 85% TGI, respectively). Immunophenotyping of tumor bearing animals treated with NDI-101150 revealed an increase in infiltrating CD19+ B cells and an increased tumor B cell transcriptional signature. Conclusions Pharmacological inhibition of HPK1 with NDI-101150 represents a novel immunomodulatory approach for engaging and enhancing B cell activation within the tumor microenvironment. NDI-101150 is currently being tested in a Phase 1 trial in patients with advanced recurrent or metastatic solid tumors. References Helmink, B.A., et al., Nature 2020. v577: 549-55. Cabrita, R., et al., Nature 2020. v577: 561-5. Citation Format: David Ciccone. Hematopoietic Progenitor Kinase 1 (HPK1) inhibition enhances antibody secretion, pro-inflammatory cytokine production and proliferation of primary human B cells [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C065.

CAR-T Cells for Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by an abnormal inflammatory response against nuclear antigens with consequent tissue damage. Autoreactive B cells and auto-antibodies have a fundamental role in SLE pathogenesis. Lupus nephritis (LN) has a great impact on patients' survival and quality of life and still represents and unmet clinical need due to the lack of specific treatments and to the poor response to conventional immunosuppression. Regulatory T cells (Tregs) physiologically maintain the immune tolerance and are impaired in SLE. Polyclonal Treg transfer obtained unsatisfactory results due to the low number of disease-relevant antigen-specific cells. Chimeric Antigen Receptors (CARs) are molecules capable of redirecting T cell specificity. CAR-Tregs proved effective in pre-clinical mouse models of autoimmunity. We aimed at developing a CAR-Treg based product to be employed in SLE in particular in LN. We isolated Tregs from Healthy Donors Peripheral Blood Mononuclear Cells (PBMCs) and expanded them with IL-2 and rapamycin. We transduced Tregs with a Lentiviral Vector encoding for a second-generation anti-CD19 CAR, considering the relevant role of autoreactive B cells and autoantibodies in SLE. Engineered cells retained their immune suppressive capabilities upon polyclonal stimulation. Noticeably, they acquired new antigen-specific suppressive capacities, being able to block autologous B cell proliferation. We set up a humanized mouse model of SLE. In vivo, CAR-Tregs delayed the occurrence of B cell lymphopenia, producing immunomodulatory cytokines and without showing toxicity or reprogramming towards Th17 pro-inflammatory cells. In inflamed organs, CAR-Tregs restored the normal composition of the immune system. In conclusion, we efficiently generated anti-CD19 CAR-Tregs and proved their efficacy both in vitro and in an in vivo humanized mouse model of lupus.

Preclinical Characterization of the Anti-Leukemia Activity of the CD33/CD16/NKG2D Immune Modulating TriNKET ® BMS-986357 (CC-96191)

CD33 is widely expressed by myeloid cells and is a validated drug target in acute myeloid leukemia (AML), as shown by the benefit of some patients from the CD33 antibody-drug conjugate gemtuzumab ozogamicin (GO). However, GO is often ineffective and toxic, prompting interest in more potent CD33-directed therapies. Success of T cell-engaging bispecific antibodies in lymphoid malignancies has raised enthusiasm for similar agents targeting CD33, but toxicities from activated T cells cause significant challenges for their use and provide a strong rationale to explore drugs engaging natural killer (NK) cells. Here, we investigated BMS-986357, a TriNKET ® that activates NK cells via CD16 and NKG2D receptors while targeting CD33. This format was chosen because simultaneous engagement of multiple activating NK cell receptors yields greater cytotoxic activity against neoplastic cells than engagement via a single activating receptor. Surface plasmon resonance analyses showed BMS-986357 simultaneously binds CD33, NKG2D, and CD16a, and co-engagement of NKG2D and CD16a increases the avidity. In the presence of primary human NK cells from healthy donors or a human NK cell line, the TriNKET ® demonstrated broad cytolytic anti-leukemia activity in a strictly CD33-dependent manner using a panel of CD33-expressing or CD33-deficient/deleted acute leukemia cells. Consistent with this, removing the CD33 binding domain rendered BMS-986357 ineffective against CD33+ AML cells. Drug-induced cytotoxicity was greater with BMS-986357 than with monoclonal CD33 antibodies, including lintuzumab and an afucosylated antibody with enhanced NK function, demonstrating the benefit of the TriNKET ® format. Compared to BMS-986357, substantially less cytotoxicity was observed with an Fc-mutant variant of BMS-986357 that abrogates binding to CD16a or an NKG2D dead-arm TriNKET ®, and cytolytic effects were reduced with a CD16-deficient NK cell line vs. a CD16-expressing subline, indicating maximal efficacy of BMS-986357 required co-engagement of CD16a and NKG2D. Using sublines of OCI-AML3 and KG-1 cells (both cell lines with low endogenous CD33 expression) to overexpress wild-type CD33 at increasing levels, we found low abundance of CD33 curtailed BMS-986357-induced cytotoxicity. Flow cytometric binding studies identified BMS-986357 to recognize the membrane-distal V-set domain of CD33. Unlike GO, BMS-986357-mediated cytolysis was not affected by over-expression of ABC transporter proteins by AML cells. The potency but not maximal activity of BMS-986357 was reduced by super-physiologic concentrations of soluble CD33; in contrast, the soluble form of the NKG2D ligand MICA did not impact TriNKET ® activity. In the presence of CD33+ AML cells, BMS-986357 activated NK cells but not T cells from healthy donor peripheral blood mononuclear cells and produced similar levels of maximum cytolysis as a CD33/CD3 bispecific antibody. Despite this, BMS-986357 elicited 10 to >100-fold lower soluble cytokine levels including IFN-γ, TNF, IL-6, and GM-CSF than a CD33/CD3 bispecific antibody, suggesting BMS-986357 has the potential for CD33/CD3 bispecific-like efficacy without the associated risk of cytokine release syndrome. Finally, in bone marrow specimens from patients with AML, BMS-986357 killed AML cells but not normal monocytes, suggesting selectivity of drug-induced cytotoxicity toward neoplastic cells, consistent with the notion NK cells are capable to differentiate between healthy and leukemic CD33+ cells. This selectivity suggests BMS-986357 may produce less myelosuppressive toxicity than what has been observed with CD33 targeting antibody-drug conjugates. In summary, our findings demonstrate that BMS-986357 TriNKET ® has potent CD33-dependent cytolytic activity in vitro against human AML cells, supporting the drug's exploration in early phase clinical trials. One such trial (NCT04789655) has opened accrual for adults with relapsed/refractory AML.