C1498 Cells Research Articles

Abstract 4181: AXL-specific single domain antibodies show diagnostic potential and anti-tumor activity in acute myeloid leukemia

Abstract Rationale: AXL expression has been identified as a prognostic factor in acute myeloid leukemia (AML) and is detectable in approximately 50% of AML patients. In this study, we developed AXL-specific single domain antibodies (sdAbs), cross-reactive for both mouse and human AXL protein, to non-invasively image and treat AXL-expressing cancer cells. Methods: AXL-specific sdAbs were induced by immunizing an alpaca with mouse and human AXL proteins. SdAbs were characterized using ELISA, flow cytometry, surface plasmon resonance and the AlphaFold prediction software. A lead compound was selected and labeled with 99mTc for evaluation as a diagnostic tool in mouse models of human (THP-1 cells) or mouse (C1498 cells) AML using SPECT/CT imaging. For therapeutic purposes, the lead compound was fused to a mouse IgG2a-Fc tail and in vitro functionality tests were performed including viability, apoptosis and proliferation assays in human AML cell lines and primary patient samples. Using these in vitro models, its anti-tumor effect was evaluated as a single agent, and in combination with standard of care agents venetoclax or cytarabine. Results: Based on its cell binding potential, cross-reactivity, nanomolar affinity and GAS6/AXL blocking capacity, we selected sdAb20 for further evaluation. Using SPECT/CT imaging, we observed tumor uptake of 99mTc-sdAb20 in mice with AXL-positive THP-1 or C1498 tumors. In THP-1 xenografts, an optimized protocol using pre-injection of cold sdAb20-Fc was required to maximize the tumor-to-background signal. Besides its diagnostic value, we observed a significant reduction in tumor cell proliferation and viability using sdAb20-Fc in vitro. Moreover, combining sdAb20-Fc and cytarabine synergistically induced apoptosis in human AML cell lines, while these effects were less clear when combined with venetoclax. Conclusions: Because of their diagnostic potential, sdAbs could be used to screen patients eligible for AXL-targeted therapy and to follow-up AXL expression during treatment and disease progression. When fused to an Fc-domain, sdAbs acquire additional therapeutic properties that can lead to a multidrug approach for the treatment of AXL-positive cancer patients. Citation Format: Niels Vandewalle, Hatice Satilmis, Emma M. Verheye, Rong Fan, Yanmeng Wang, Timo W. De Groof, Tessa Kerre, Nathan De Beule, Ann De Becker, Elke De Bruyne, Eline Menu, Karin Vanderkerken, Karine Breckpot, Nick Devoogdt, Kim De Veirman. AXL-specific single domain antibodies show diagnostic potential and anti-tumor activity in acute myeloid leukemia [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 4181.

Histone Methyltranferase SETD8 Stimulates Proliferation and Anti-Apoptotic Effect in Acute Myeloid Leukemia through Epigenetically Upregulation of CXCR4

Acute myeloid leukemia (AML) is the most common type of leukemia., characterized by the rapid and uncontrolled growth of abnormal cells. Epigenetic modifications control gene expression without affecting its DNA sequence. H4K20me1 is the mono-methylation occurring on lysine 20 of histone H4, acting as an epigenetic mark that promotes gene expression. SETD8 is responsible for catalyzing the mono-methylation of lysine 20 on histone H4. While SETD8's role and mechanisms have been studied in various types of cancer, its function in AML remains unclear. This study is based on the screening of a small molecule compound library, which identified the inhibitor UNC0379 targeting the histone methyltransferase SETD8, showing clear inhibitory effects on three non-M3 AML cell lines. Bioinformatical analysis revealed elevated SETD8 expression in AML patients compared to normal individuals and higher SETD8 expression corresponded with lower overall survival rates (OS). Further investigations using AML cell lines and normal peripheral blood mononuclear cells (PBMCs) demonstrated that SETD8 knockdown or UNC0379 intervention inhibited cell proliferation and increased apoptosis in AML cells, while PBMC cells remained unaffected. In an AML model constructed with C1498 cell injection in C57BL/6J mice, we observed that SETD8 knockdown and treatment with UNC0379 inhibited tumor formation and infiltration. To elucidate the molecular mechanism of SETD8's impact on AML, we conducted transcriptome sequencing on SETD8 knockdown AML cells and found significantly decreased mRNA expression of CXCR4, which was further validated at the protein level. Also, BeatAML and TCGA datasets demonstrated a positive correlation between SETD8 and CXCR4 mRNA expression. These phenomena motivated us to clarify the regulation relationship between SETD8 and CXCR4. CXCR4 is a crucial membrane receptor. After stimulation, it promotes AML cell proliferation and survival. CHIP experiments in SETD8 knockdown cells revealed reduced H4K20me1 enrichment in the CXCR4 promoter region. Subsequent rescue experiments demonstrated that overexpressing CXCR4 or using its corresponding agonist SDF-1alpha in SETD8 knockdown cells moderately restored cell proliferation and reduced apoptosis. In summary, we discovered that SETD8 promotes CXCR4 transcriptional activation through catalyzing the H4K20me1 mark, thereby influencing AML cell proliferation and apoptosis. SETD8 presents a promising therapeutic target through genetic or pharmacological intervention.

Leukemic Cell-Intrinsic Innate Nucleic Acid Receptor Signaling Governs Efficacy of Hypomethylating Agents and Immunosurveillance in AML

Introduction: Hypomethylating agents (HMA), such as Azaciditine (AZA), are a long-established treatment option for acute myeloid leukemia (AML). Besides epigenetic reprogramming of malignant cell clones, HMAs are recognized to facilitate antineoplastic immunity. In vitro assessments in solid tumor models suggest that a major mechanism underlying AZA-triggered immune responses may be the activation of innate nucleic acid sensing pathways. As such, the RNA- and DNA-sensing receptor systems, RIG-I/MDA-5 and cGAS/STING - and subsequent type I interferon (IFN-I) signaling seem to be triggered by the transcriptional upregulation of otherwise DNA-hypermethylated and thus silenced endogenous retroviruses (ERVs). In AML, it is unknown whether similar processes are involved and/or by which molecular mechanisms, HMAs modulate anti-leukemic immunity against AML blasts, and how these processes are affected during acquired HMA resistance. Methods: Murine (c1498 and Wehi-3B) and human (MOLM-13) AML cell lines were exposed to AZA in vitro and analyzed for expression of ERVs. Nucleic acid receptor sensing pathways and IFN-I genes are not usually DNA methylated by AZA at promoter regions. However, the re-expression of endogenous nucleic acids or ERVs could trigger their activation. Protein and transcriptional expression of major components of nucleic acid receptor sensing pathways and IFN-I genes were, therefore, analysed. To understand the importance of AML cell-intrinsic nucleic acid receptor signaling in HMA-induced immunosurveillance, syngeneic c1498 and Wehi-3B AML models were employed. Mice received 2 cycles of 2.5mg/kg AZA (6 days on, 5 days off, 6 days on) intraperitoneally to mimic the principal treatment course used in patients. To address the contribution of the nucleic acid-sensing pathways to AZA treatment efficacy in vitroand in vivo, AML cells with acquired AZA resistance (AZA-R) or gene engineered AML cells deficient in RNA receptors (RIG-I/MDA-5), or the RNA- and DNA-sensing adapter proteins (MAVS and STING) were employed. Results: A targeted ERV screen revealed upregulation of various ERV transcripts in c1498 and Wehi-3B cells and was similarly observed in MOLM-13 AML cells following AZA exposure in vitro. Increased RNA transcript and protein expression of RIG-I/MAVS and (to a lesser degree) STING was observed, resulting in activation of downstream constituents including higher phosphorylation of the transcription factors IRF3/7 and NF-kB, IFN-I, and other ISGs. This was abrogated in RIG-I and MAVS, but not STING, deficient murine and human AML cells. Interestingly, expression of RIG-I/MDA-5, STING and all other downstream constituents, but not MAVS, were diminished in AZA-R AML cells. In mice harboring MAVS deficient AML (c1498), HMA treatment failed to show anti-leukemic activity resulting in rapid disease progress and death of recipient animals. Loss of STING in leukemic cells also impacted AZA treatment efficacy, although to a much less pronounced degree. These findings were similarly reproduced with Wehi-3B AML-engrafted mice. Following antibody-mediated depletion of T cells but not NK cells, mice rapidly succumbed to AML disease and demonstrated no anti-leukemic effect of AZA treatment. CyTOF and flow cytometric analysis also revealed increased bone marrow and spleen infiltration as well as activation of CD4 +/CD8 + T cells, NK cells, and MHC-II + APCs/Myeloid cells in AZA treated mice bearing wildtype AML, compared to untreated. This was not observed in AZA-treated mice bearing MAVS-deficient or AZA-R AML. Conclusion: Our findings indicate that nucleic acid receptor signaling (specifically RIG-I/MAVS) within leukemic cells is imperative for AZA efficacy and immunosurveillance in AML. Whether these RNA-sensing receptors are triggered by ERVs or alternate (endogenous) RNAs remains to be determined. Elucidating the molecular mechanisms of how nucleic acid sensors within leukemic blasts shape treatment efficacy of AZA may guide development of systematic immunotherapeutic strategies for AZA-R AML by targeted combinatorial approaches.

Reduced protein intake and aging affects the sustainment of hematopoiesis by impairing bone marrow mesenchymal stem cells

Protein malnourishment (PM) is common among the elderly, but how aging and PM impact hematopoiesis is not fully understood. This study aimed to assess how aging and PM affect the hematopoietic regulatory function of bone marrow (BM) mesenchymal stem cells (MSCs). Young and aged male C57BL/6J mice were fed with normoproteic or hypoproteic diets and had their nutritional, biochemical, and hematological parameters evaluated. BM MSCs were characterized and had their secretome, gene expression, autophagy, reactive oxygen species production (ROS), and DNA double-stranded breaks evaluated. The modulation of hematopoiesis by MSCs was assayed using in vitro and in vivo models. Lastly, BM invasiveness and mice survival were evaluated after being challenged with leukemic cells of the C1498 cell line. Aging and PM alter biochemical parameters, changing the peripheral blood and BM immunophenotype. MSC autophagy was affected by aging and the frequencies for ROS and DNA double-stranded breaks. Regarding the MSCs’ secretome, PM and aging affected CXCL12, IL-6, and IL-11 production. Aging and PM up-regulated Akt1 and PPAR-γ while down-regulating Cdh2 and Angpt-1 in MSCs. Aged MSCs increased C1498 cell proliferation while reducing their colony-forming potential. PM and aging lowered mice survival, and malnourishment accumulated C1498 cells at the BM. Finally, aged and/or PM MSCs up-regulated Sox2, Nanog, Pou5f1, and Akt1 expression while down-regulating Cdkn1a in C1498 cells. Together, aging and PM can induce cell-intrinsic shifts in BM MSCs, creating an environment that alters the regulation of hematopoietic populations and favoring the development of malignant cells.

Irradiated Extramedullary Acute Myeloid Leukemia Increases Survival in a Leukemic Mouse Model

The systemic nature of AML likely limits their immunogenicity because antigen presentation is primarily mediated by splenic dendritic cells, which induces immune tolerance. Since antigen presentation in tissue draining lymph nodes can induce anti-tumor immune responses, we hypothesized that local irradiation of cutaneous, extramedullary leukemias will increase immunogenic cell death, dendritic cell maturation and improved survival. A murine AML cell line C1498 was assessed for immunogenic markers calreticulin (CALR), HMGB1 and cGAS-STING pathway using fluorescence cytometry and qRT-PCR. Syngeneic mice were injected with C1498 subcutaneously to model extramedullary lesions and intravenously to model systemic leukemias. Cells and subcutaneous tumor were focally irradiated with 2 Gy or 8 Gy. Two-way ANOVA and Student's t-test were used for paired-wise comparisons. Survival was estimated by Kaplan-Meier plot and groups were compared using log-rank test. C1498 cells or tumors irradiated with 2 Gy or 8 Gy showed increased CALR and HMGB1 as well as (cGAS/Md21b1; 5-fold; p<0.001) and interferon alpha (Ifna; 3-fold; p<0.001) after 48h (18- and 4-fold, respectively; p<0.05) compared to not treated controls (NTC). Irradiated C1498 subcutaneous tumors displayed increased CD11b-positive cells (9-fold; p<0.001), CD11c (6-fold; p<0.001), and MHCII-positive CD11c cells (4-fold; p<0.01) in irradiated tumors compared to NTC. Irradiation of subcutaneous C1498 tumors increased median survival in mice also injected with C1498 cells intravenously compared to non-irradiated mice bearing systemic leukemias (46 vs. 25 days; p<0.01). Irradiation of C1498 tumors combined with anti-PDL1 treatment further increased median survival in our leukemia model compared to untreated controls (>50 vs. <30 days; p<0.001). Irradiated extramedullary AML increased immunogenic markers and activation of immune effector cells that correlated with increased survival in mice also bearing systemic leukemia. These results suggest focal irradiation of extramedullary AML may facilitate eradiation of systemic leukemias.

Combined inhibition of XIAP and autophagy induces apoptosis and differentiation in acute myeloid leukaemia.

Perturbations in autophagy, apoptosis and differentiation have greatly affected the progression and therapy of acute myeloid leukaemia (AML). The role of X-linked inhibitor of apoptosis (XIAP)-related autophagy remains unclear in AML therapeutics. Here, we found that XIAP was highly expressed and associated with poor overall survival in patients with AML. Furthermore, pharmacologic inhibition of XIAP using birinapant or XIAP knockdown via siRNA impaired the proliferation and clonogenic capacity by inducing autophagy and apoptosis in AML cells. Intriguingly, birinapant-induced cell death was aggravated in combination with ATG5 siRNA or an autophagy inhibitor spautin-1, suggesting that autophagy may be a pro-survival signalling. Spautin-1 further enhanced the ROS level and myeloid differentiation in THP-1 cells treated with birinapant. The mechanism analysis showed that XIAP interacted with MDM2 and p53, and XIAP inhibition notably downregulated p53, substantially increased the AMPKα1 phosphorylation and downregulated the mTOR phosphorylation. Combined treatment using birinapant and chloroquine significantly retarded AML progression in both a subcutaneous xenograft model injected with HEL cells and an orthotopic xenograft model injected intravenously with C1498 cells. Collectively, our data suggested that XIAP inhibition can induce autophagy, apoptosis and differentiation, and combined inhibition of XIAP and autophagy may be a promising therapeutic strategy for AML.

RNA-based Personalized Cancer Vaccine for AML immunotherapy

Abstract Acute Myeloid Leukemia (AML) is a rapidly progressing malignancy relying primarily on chemotherapy as the frontline treatment option. Success of personalized neoantigen vaccines in melanoma patients have garnered great attention in the field of immunotherapy. We hypothesize that personalized cancer vaccine, in the form of mRNA, can be a viable treatment strategy for AML patients. Next generation sequencing was performed on both C57BL6Jinv mouse’s and C1498 cell line’s nucleic acid materials. Three different neoepitope prediction pipelines were utilized to identify potential immunogenic neoepitopes. Candidate neoepitopes within intron polyadenlyation sites (iPAS), retained intron (RI) sites and somatic mutation (SM) sites were found. A total of 285 SM-derived neoepitopes were identified. Top 38 highly expressed genes were selected for further analysis. Using Sanger sequencing, we confirmed 37 out of the 38 mutations. A total of 5 iPAS-derived neoepitopes were identified. A total of 26 RI-derived neoepitopes were identified in our first RNAseq analysis and a separate 476 RI-derived neoepitopes were identified in our second RNAseq analysis. With these neoepitope candidates, we narrowed down our selection and did a preliminary screen for immunogenic epitopes using a total of 71 synthetic peptides in an ELISpot assay. 10 neoepitope candidates were short-listed for further in-vivoevaluation. mRNA vaccine was synthesized and evaluated in a murine AML model. T cell responses against the 10 neoepitopes were analyzed to provide pre-clinical evidence for patient studies. Neoepitope screening platform with human PBMCs has also been established to validate the prediction pipelines in AML patients. Supported by grant from NMRC (MOH-CIRG21jun-0008)

Abstract 3269: Reappraisal of immunologic mechanisms of hypomethylating agents in treatment of high-risk myelodysplastic syndrome and acute myeloid leukemia

Abstract Hypomethylating agents (HMA) have been used for the treatment of high-risk myelodysplastic syndrome (HR-MDS) and acute myeloid leukemia (AML) of the elderly. In addition to direct cytotoxic effect of HMA on MDS/AML, HMA upregulates effector T-cell function by demethylating T-cell exhaustion-associated genes (Hazem, Cell 2017) and promoting effector T-cells trafficking to tumor microenvironment by Th1-type chemokines reactivation (Peng, Nature 2019). To elucidate dynamic changes of immune cells profile and gene expression after HMA treatment in MDS/AML, we conducted single cell RNA sequencing of three sequential bone marrow (BM) samples from one HR-MDS patient treated with azacitidine. In BM samples at diagnosis (‘diagnosis’), after 2 cycles of azacitidine (BM blasts increased from 6 to 11%; ‘progression’), and after 3 additional cycles of azacitidine (BM blasts decreased to 3.5% with trilineage hematopoiesis; ‘response’), cell clusters were identified according to immune cell types. The relative proportion of the NK-cell cluster showed the most significant increase up to response (1.3% at ‘diagnosis’, 4.3% at ‘progression’, and 11.8% at ‘response’). By contrast, the CD8 T-cells cluster showed modest increase of proportion at the 3 timepoints (2.7%, 3.9%, and 7%, respectively). Differentially Expressed Gene (DEG) analysis showed CXCR4 was overexpressed in the BM NK-cell cluster at the ‘response’ time point. To determine whether the NK cells can be trafficked to BM by HMA treatment in mouse MDS/AML models, mouse myeloid leukemia cells (C1498 cells) were transplanted into the tail vein of 6-to-8-week aged syngeneic C57/BL6 mice. C1498 bearing mice were intraperitoneally treated with HMA (decitabine) or vehicle for 5 consecutive days. While HMA inhibited in vivo AML proliferation, the quantity of NK cells (NK1.1+) was significantly increased in BM of HMA-treated mice than vehicle controls. In addition, CXCR4 expression in NK1.1+ cells from BM of HMA-treated mice were significantly up-regulated, compared with vehicle controls. The NK depletion in HMA-treated AML mice decreased anti-leukemic effect, suggesting that NK cells may be one of immune cell subsets responsible for HMA induced anti-leukemia effect. Taken together, recruitment of NK cells into MDS/AML BM through CXCR4 overexpression and anti-leukemic cytotoxicity exerted by NK cells can be one of the important immunologic mechanisms of HMA in MDS/AML. Treatment strategy of recruiting more NK cells BM by HMA and maximizing cytotoxicity of NK cells should be further investigated. Citation Format: Junshik Hong, Suji Min, Jihyun Park, Carly M. Fielder, Qianni Hu, Sung-Soo Yoon, Tae Kon Kim. Reappraisal of immunologic mechanisms of hypomethylating agents in treatment of high-risk myelodysplastic syndrome and acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3269.

High Potency Vasoactive Intestinal Peptide Receptor Antagonists Induce Durable Antileukemia/Tumor T Cell Memory in Mice with Once Daily Dosing

Introduction: Allogeneic bone marrow transplantation (allo-BMT) is curative for patients with myeloid leukemia (AML) through the activity of cytotoxic effector donor T cells, but high morbidity and mortality of allo-BMT limits the use of this therapy. A long-standing goal is the development of strategies that induce an autologous immune response to leukemic blasts by the patient's T cells. Vasoactive intestinal peptide (VIP) is a neuropeptide with pleiotropic functions, including modulation of immune and inflammatory responses. Previous studies demonstrated that VIP hybrid (VIPhyb), a peptide antagonist of VIP-signaling, induced T cell-dependent anti-leukemic activity in murine allotransplant models and promoted activation of mouse and human T cells (Li et al., 2016, Cancer Res). We developed a series of novel peptide VIP antagonists (VIP-ANT) based upon predicted binding affinity in silico to human VIP receptors VPAC1 and VPAC2. We tested the anti-cancer potential of these new VIP-ANT peptides in murine models of myeloid leukemia and mastocytoma, investigating the optimal dose and schedule of administration, and explored mechanisms underlying anti-tumor memory induced by VIP-ANT peptides. Methods: B6 (CD45.1, or albino) mice were injected intravenously with 1 x 106 C1498 cells (AML), and DBA/2j mice were injected subcutaneously with 5 x 104 P815 cells (myeloid mastocytoma). Leukemia-bearing mice were treated with subcutaneous injections of VIP-ANT or control scrambled peptides. Treatment started six days after injection of cells when C1498 leukemia cells were detectable in the blood, and luciferase+ P815 cells as tumors were palpable. A range of VIP-ANT doses was administered s.c. at 10, 30, or 100 μg. Treatment schedules tested included twice daily for 14 doses, once daily, once every other day, once every three days, and once weekly for 7 doses. Some mice received a single dose at day +6 following leukemia cell injection. Lymphocyte kinetics and leukemia cell burden were analyzed weekly through submandibular peripheral blood collections. Mice without evidence of AML/mastocytoma >60 days post-inoculation received a second injection of a two-fold higher dose of C1498 (2 × 106 cells) or P815 (1 × 105 cells). Results: We tested over 13 new VIP-ANT peptides. Daily or every other day (qod) administration of the novel VIP-ANT peptides to leukemia/tumor-bearing mice led to clearance of C1498 cells from blood or complete regression of P815 in 40 % of mice, leading to significantly improved survival over 60 days. Daily administration of 10 μg of novel VIP-ANT peptides for 7 days to leukemic mice prolonged survival(p<0.0001 VIP-ANT vs scramble, Fig 1A), with the fraction of mice that remained leukemia-free proportional to the predicted binding affinity of the VIP-ANT to human VPAC1 and VPAC2. With increased dose intensity and dose-density of ANT308, the most potent peptide, 40%-80% of mice survived to 70 days (median survival days (MSD) of 60 days) after ANT308 treatment compared with the survival of <20% in mice receiving scrambled peptide (MSD 36 days). Increasing the dose and schedule of ANT308 administration to 100 μg twice-daily led to 65% survival (MSD not reached) versus 40% with daily dosing, 30% with every-other-day dosing, and 0% survival with scrambled-sequence control peptide (MSD 33 days) (p<0.001, Fig 1B). Notably, the affinity of different VIP-ANT peptides to VPAC1 and VPAC2 VIP receptors significantly correlated with the survival of C1498-leukemic mice following prior treatment with the corresponding peptide. Prior treatment of leukemic mice with VIP-ANT induced protective immunological memory, rendering mice resistant to re-challenge with C1498 acute myeloid leukemia (80% survival) and P815 mastocytoma (60% survival) cells, compared with 0% survival (MSD 21 days) among immunologically naïve mice. Conclusion: Blocking VIP-signaling with high-affinity VIP-R peptide antagonists represents a novel pharmacological approach to enhance adaptive T cell responses to leukemia/myeloid sarcoma-associated antigens in murine leukemia/tumor models. We are continuing PK and toxicology studies with the lead VIP-ANT peptides to support the development of phase 1 clinical trials for patients with relapsed AML. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Inhibition of the Receptor Interactive Protein Kinase 1 (RIP1) Pathway Prevents Acute Gvhd

Acute graft-versus-host disease (GVHD) causes apoptosis of intestinal stem cells (ISCs) that are key targets in the gastrointestinal (GI) tract (Zeiser and Blazar, NEJM 2917; 377:2167). The receptor interactive protein kinase 1 (RIP1) is an important mediator of apoptosis and we investigated the role of the (RIP1) pathway in GI tract and ISC damage in both human and mouse GVHD models. Immunohistochemical staining of human GI biopsies from GVHD patients showed strong phospho-RIP1 staining in biopsies with Lerner grades 2/3 compared to grades 0/1 (12/17 v 0/8, p < 0.01). We then established in vitro models of ISC apoptosis (at least 50% loss) by adding 10 ng/ml of both IFNg and TNFa to organoid cultures from both ileum and colon (organoids cultures with either IFNg or TNFa alone showed no change). Addition to cultures of 0.1 mcg/ml GNE684, a well-characterized small molecule RIP inhibitor (Patel et al, Cell Death Diff 2020; 27:161), dramatically reversed ISC loss in both human and mouse ileal organoids as measured by cross sectional area (Fig 1). WE observed an identical pattern in colon cultures where GNE684 reversed loss of human ISCs (70.0 + 7.7 % v 29.3 + 2.5 %, p < 0.001) and mouse ISCs (100 + 6.6 % v 41 + 6.6 % p < 0.001). In vivo, 14 daily ip injections of GNE684 prevented mortality in a GVHD mouse model (C3H.SW → B6) in a dose dependent fashion (Fig 2). Systemic GNE administration also improved survival in a second model (Balb/c → B6: day 30 survival 7/10 v 0/10, p < 0.001). In the C3H.SW → B6 model there were dramatic reductions in CD4+ lamina propria effector lymphocytes secreting either IFNg (56 + 11 v 9 + 2, p < 0.001) or IL-17 ( 22 + 10 v 7 + 4, p < 0.01) and in CD8+ effector cells secreting IFNg (39 + 11 v 8 + 3, p < 0.001) or IL-17 ( 19 + 8 v 7 + 2, p < 0.001) on day 10 after HCT. Importantly, GVHD was dramatically reduced when administration of GNE684 was used as treatment for GVHD beginning on day +7 after GVHD was established (day 40 survival: 8/12 v 2/12, p = 0.02). Additionally, survival dramatically improved in RIP1 kinase-dead recipients compared to wild-type B6 controls in both the C3H.SW → B6 model (13/16 v 4/16, p < 0.001) and in the Balb/c →B6 model (13/20 v 1/20, p < 0.001). IFNg secreting CD4+ and CD8+ effector lymphocytes that infiltrated the lamina propria were significantly reduced in RIP1 kinase-dead recipients compared to wild-type controls (58 + 13 v 11 + 7 and 39 + 11 v 14 + 4, respectively [p < 0.001 for both]). Infiltrating lymphocytes secreting IL-17 were also reduced four fold. Importantly, administration of GNE684 preserved beneficial GVL effects when lethal doses of myeloid tumor C1498 cells that caused 100% mortality by day 28 in syngeneic BMT recipients were added to the donor inoculum (day 42 survival: 7/10 v 4/13, p = 0.03). We conclude that RIP1 is a key mediator of GI damage during GVHD. In vitro RIP1 inhibition prevents ISC apoptosis in both mouse and human models of GI GVHD. RIP1 inhibition, either through genetic alteration of the RIP1 kinase domain in transplant recipients or through systemic administration of the RIP1 inhibitor GNE684, protects the GI tract from acute GVHD damage as measured both clinically and histologically in preclinical models while preserving beneficial GVL effects. These data suggest that GNE684 a clinical trial of GNE684 is warranted in patients with gastrointestinal GVHD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

P-081 Effect of chemotherapy (cytarabine) and acute myeloid leukemia on the development of spermatogenesis, spermatogonial microenvironment and inflammatory factors at the adult age of immature-treated mice

Abstract Study question How do AML and cytarabine affect the development of spermatogenesis, germ cell microenvironment and testicular inflammatory factors at the adult age of immature-treated mice? Summary answer AML and cytarabine significantly damaged the normal histology of the seminiferous tubules and impaired different stages of spermatogenesis, testicular growth/inflammatory factor in the adult age. What is known already The effect of different types of cancers on male fertility was reported. AML constitutes around 20% of the diagnosed childhood leukemia. Cytarabine is used as anti-AML treatment. Cytarabine is involved in reduction of testes growth and induces testicular atrophy in adults. In adult AML patients, it was shown that AML affects semen parameters even before chemotherapy treatment. Furthermore, a significant reduction in semen quality of thawed cryopreserved semen from leukemia patients compared to control patients was reported. However, the effect of AML and cytarabine before puberty on the development of spermatogenesis in adult age was not yet reported. Study design, size, duration Two-week-old males C57/BLACK mice were used. 1. Control group – injected with saline. 2. AML group – injected (intraperitoneal; i.p) with 3x104 AML cells/100 ml (murine C-1498 AML cell line). 3. Cytarabine group - three injections of cytarabine (140 mg/kg/100 ml) were performed every 12 hours. 4. AML+cytarabine group – cytarabine was i.p injected 24 hours after AML injection (injections were performed every 12 hours 3 times). Mice were sacrificed 1,2,3,4,5 weeks after AML injection. Participants/materials, setting, methods Testes were removed, weighted and fixed in Bouin’s solution for histological evaluation, or kept at -70°C for RNA extraction. The presence of premeiotic (SALL4, PLZF), meiotic (CREM-1) and postmeiotic (ACROSIN) cells were examined by immunofluorescence staining analysis and/or RNA expression by qPCR analysis. Main results and the role of chance We have successfully developed a system of AML in immature mice by i.p injection of C1498 cells. Cytarabine prolonged life of AML-treated mice from 2.5 weeks to 4 weeks. AML had no effect on both body and testicular weight. However, cytarabine significantly reduced testicular weight (around 50% of the control in the first 3 weeks after treatment, and around 30% of the control from 3-4.5 weeks after treatment; p &amp;lt; 0.001). One and/or 2 weeks after the treatment showed that both AML and cytarabine alone or in combination significantly decreased seminiferous tubules normal histology compared to control, (30%, 20%, 10% respectively) (p &amp;lt; 0.001). Cytarabine, but not AML significantly increased the expression of PLZF and SALL4 after 2 weeks compared to control (p &amp;lt; 0.001). However, each treatment significantly increased the percentages of seminiferous tubules with apoptotic cells compared to control (p &amp;lt; 0.05). AML or cytarabine significantly decreased the percentages of tubules with meiotic and postmeiotic markers compared to control (p &amp;lt; 0.05). Also, AML or cytarabine significantly decreased the testicular protein levels of GDNF, CSF-1 (p &amp;lt; 0.01) but did not affect LIF compared to control. Furthermore, AML or cytarabine significantly decreased the protein levels of IL-10. However, AML significantly increased IL-6 when cytarabine increased it compared to control (p &amp;lt; 0.01). Limitations, reasons for caution Animal model of leukemia may behave different from human model. Wider implications of the findings We successfully developed AML disease in immature mice, and demonstrated its impairment the normal histology of the seminiferous tubules and spermatogenesis in the adult age. We showed that AML and cytarabine affect testicular microenvironmental and inflammatory factors. Our results may assist in development future therapeutic strategies for male fertility preservation. Trial registration number NON

Abstract 5536: Selinexor inhibits lymphoma-leukemia tumor progression directly and through activation of anti-cancer immune response

Abstract Background: Selinexor is a Selective Inhibitor of Nuclear Export (SINE) compound that binds covalently to Exportin 1 (XPO1) and inhibits its nuclear export function, resulting in nuclear accumulation of tumor suppressor proteins (TSPs) including p53, pRB, and IκB-α. Selinexor was evaluated for improved survival in tumor-bearing mice with hematological malignancies using EL-4 (T cell lymphoma/leukemia) and C1498 (Acute myeloid leukemia) models. We hypothesized that selinexor increases survival by directly inducing tumor cell apoptosis and blocks immunosuppressive effects of myeloid derived suppressor cells (MDSCs). Methods: Mice were injected with 2×106 EL-4 or 1×106 C1498 cells intravenously followed by oral treatment with saline, vehicle, or different selinexor dosing schedules (5 mg/kg weekly (5), twice weekly on Wed and Fri (5 d1/3) or Mon and Fri (5 d1/5) or 10 mg/kg weekly (10). Selinexor was given by gavage. To examine the effect of selinexor on immune cells during tumor growth, Tumor bearing mice treated with vehicle or selinexor were euthanized at day 14 after tumor injection. Spleens were removed, single cell suspensions were isolated and the percentage of immune cells including MDSCs, regulatory T cells (Tregs) and the production of interferon gamma (IFN-γ) were analyzed by flow cytometry. Tumor bearing mice were monitored for survival in separate experiments. Results: Selinexor at the weekly 5 d1/3 and the 10 dosing significantly increased survival in mice injected with either tumor line. Whereas weekly 5 or 5 d1/5 dosing did not significant affect survival. Selinexor at weekly 10 dosing significantly reduced the population of polymorphonuclear MDSCs (PMN-MDSCs). Selinexor at 10, 5 d1/3 and 5/1/5 weekly dosing significantly increased IFN-γ production by CD8+ and CD4+ T cells when compared to vehicle. There were no differences in Tregs populations. Conclusions: These data demonstrate that different selinexor dosing and schedules have differential efficacy on survival in murine models of leukemia/lymphoma. Selinexor effects are dose and schedule dependent. We found that in contrast to the split dosing, the single weekly high dose of selinexor reduced splenic PMN-MDSC accumulation. While both dosing schedules increased the percentage of IFN-γ positive T cells in tumor bearing mice suggesting that selinexor’s anti-cancer activity is not limited only to direct cytotoxic or cytostatic tumor cells. These data support the concept that once weekly selinexor, at a higher dose (10 mg/kg (approximately 30 mg/m2) which is comparable to the clinical dose schedule (50-60 mg weekly) can modulate the immune system to target cancer cells and could be used alone or in combination with other immunotherapies to enhance the immune system. Citation Format: Hemn Mohammadpour, Yosef Landesman, Philip McCarthy. Selinexor inhibits lymphoma-leukemia tumor progression directly and through activation of anti-cancer immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5536.

Novel RNA-based Cancer Vaccine for AML immunotherapy

Abstract Acute Myeloid Leukemia is a rapidly progressing malignancy relying primarily on chemotherapy as the frontline treatment option. Success of personalized neoantigen vaccines in melanoma patients has garnered great attention in the field of immunotherapy. We hypothesize that personalized cancer vaccine, in the form of mRNA, can be a viable treatment strategy for AML patients. Next generation sequencing was performed on both C57BL6Jinv mouse’s and C1498 cell line’s nucleic acid materials. Three different neoepitope prediction pipelines were utilized to identify potential immunogenic neoepitopes. Candidate neoepitopes within intron polyadenlyation sites (iPAS), retained intron (RI) sites and somatic mutation (SM) sites were found. A total of 285 SM-derived neoepitopes were identified. Top 38 highly expressed genes were selected for further analysis. Using Sanger sequencing, we confirmed 37 out of the 38 mutations. A total of 5 iPAS-derived neoepitopes were identified. A total of 26 RI-derived neoepitopes were identified in our first RNAseq analysis and a separate 476 RI-derived neoepitopes were identified in our second RNAseq analysis. With these three categories of candidates, we narrowed down our selection and did a preliminary screen for immunogenic epitopes using a total of 71 synthetic peptides in an ELISpot assay. Conventional ELISpot assay’s results were however non-reproducible, thereby propelling us to adopt Culture ELISpot assay. Subsequently, 10 neoepitope candidates were short-listed for further in-vivo evaluation. mRNA vaccine was synthesized and evaluated in a murine AML model. T cell responses against the 10 neoepitopes were analyzed to provide pre-clinical evidence for patient studies. Supported by NMRC CS-IRG grant

Detection of residual and chemoresistant leukemic cells in an immune-competent mouse model of acute myeloid leukemia: Potential for unravelling their interactions with immunity.

Acute myeloid leukemia (AML) is characterized by blocked differentiation and extensive proliferation of hematopoietic progenitors/precursors. Relapse is often observed after chemotherapy due to the presence of residual leukemic cells, which is also called minimal residual disease (MRD). Subclonal heterogeneity at diagnosis was found to be responsible for MRD after treatment. Patient xenograft mouse models are valuable tools for studying MRD after chemotherapy; however, the contribution of the immune system in these models is usually missing. To evaluate its role in leukemic persistence, we generated an immune-competent AML mouse model of persistence after chemotherapy treatment. We used well-characterized (phenotypically and genetically) subclones of the murine C1498 cell line stably expressing the ZsGreen reporter gene and the WT1 protein, a valuable antigen. Accordingly, these subclones were also selected due to their in vitro aracytidine (Ara-c) sensitivity. A combination of 3 subclones (expressing or not expressing WT1) was found to lead to prolonged mouse survival after Ara-c treatment (as long as 150 days). The presence of residual leukemic cells in the blood and BM of surviving mice indicated their persistence. Thus, a new mouse model that may offer insights into immune contributions to leukemic persistence was developed.

PD-1H (VISTA) Induces Immune Evasion in Acute Myeloid Leukemia

Despite progress in understanding the molecular pathogenesis in acute myeloid leukemia (AML), the disease remains highly fatal with limited therapeutic options. There is a need for novel approaches for management of AML that can overcome resistant disease. Immune checkpoint inhibitor therapy has emerged as a successful treatment strategy in several solid tumors and refractory Hodgkin lymphoma. However, preliminary data from clinical trials to date indicate that anti-PD-1 antibodies have limited single-agent activity in AML. This suggests that co-inhibitory molecules other than PD-1 may induce immune evasion in AML. Programmed Death-1 Homolog (PD-1H, VISTA) is a novel co-inhibitory molecule that induces immune evasion in solid tumors. Interestingly, The Cancer Genome Atlas (TCGA) and the Cancer Cell Line Encyclopedia database both reveal that PD-1H is over-expressed in AML at the transcript level. While we found that myeloid subsets and T cells have the expression of PD-1H in bone marrow of healthy donors, we demonstrated that PD-1H protein is highly expressed in bone marrow of 8 (of 10) human AML donors using immunohistochemistry. To determine whether the high expression of PD-1H in AML bone marrow is associated with the expression of PD-1H in AML blasts, flow cytometric analyses were performed in bone marrow aspirate of human CD34+ AML donors. Mean Fluorescent Intensity (MFI) of CD34+ AML blasts was significantly higher when compared to normal CD34+ progenitor cells (MFI: 257±82 (AML CD34+ blasts) vs 10±4 (normal CD34+ progenitor cells), N=6, p<0.05). To test our hypothesis that PD-1H induces immune evasion in AML, we transplanted PD-1H-expressing murine myeloid leukemia cells (C1498) into syngeneic PD-1H knockout (KO) or wild type (WT) littermate mice. Whole body bioluminescence (unit: radiance) was used to determine the level of luciferase activity reflecting in vivo growth of luciferase expressing C1498 cells and survival of recipient PD-1H KO mice was compared to WT controls. We observed that murine AML cell growth in vivo was diminished in PD-1H KO mice (mean radiance in one representative experiment: 2.6x106 (KO) vs 4.2x107 (WT) on day 26, N=5, p<0.05) and survival of PD-1H KO mice was improved compared to WT controls (median survival: 35 days (KO) vs 28 days (WT), N=5, p<0.05). In addition, PD-1H antibody (Ab) decreased AML cell growth in vivo in KO mice (mean radiance in one representative experiment: 2.4x105 (KO + PD-1H Ab) vs 2.6x106 (KO + Isotype control) on day 26, N=5, p<0.05) and extended survival in C1498-bearing PD-1H KO mice (median survival: 45 days (KO + PD-1H Ab) vs 35 days (KO + Isotype), N=5, p<0.05). These data suggest that PD-1H on both host cells and AML cells induces immune evasion in AML. Based on prior preclinical models, we further hypothesized that immunogenicity of AML can be enhanced by epigenetic modulation, that can potentiate anti-leukemic effect of PD-1H blockade. We found that DNA methyltransferase inhibition (DNMTi) by 5-aza-2'-deoxycytidine (decitabine) increased T cell infiltration in subcutaneously injected murine AML (C1498) tumor (CD3+ cells/tumor cells: 33±5% (DNMTi) vs 10±3% (PBS control), N=3, p<0.05) using flow cytometry and immunohistochemistry. Importantly, DNMTi potentiated the anti-leukemic effect of the PD-1H blockade (mean radiance in one representative experiment: 9.9x108 (PBS + WT) vs 1.2x108 (PBS + KO) vs 3.6x105 (decitabine + WT) vs 6.9x104 (decitabine + KO) on day 21; 5.9x109 (PBS + WT) vs 3.5x108 (PBS + KO) vs 1.8x106 (decitabine + WT) vs 1.3x105 (decitabine + KO) on day 24, N=7, p<0.05) and significantly prolonged survival in PD-1H KO mice (median survival: 28 days (WT) vs 35 days (KO) vs 39 days (DNMTi + WT) vs 60 days (DNMTi + KO), p<0.05). Together, our data suggest that PD-1H is highly expressed in human AML and can induce immune evasion in a murine model of AML (C1498). DNMTi has potential synergistic effects on PD-1H blockade and combining these two can be an important immunotherapeutic approach in AML. DisclosuresZeidan:Otsuka: Consultancy; AbbVie, Otsuka, Pfizer, Gilead, Celgene, Ariad, Incyte: Consultancy, Honoraria; Takeda: Speakers Bureau. Chen:Boehringer Ingelheim, Pfizer, NextCure: Research Funding.

PD-L1 Is Expressed and Promotes the Expansion of Regulatory T Cells in Acute Myeloid Leukemia.

Intratumoral accumulation of CD4+CD25+Foxp3+ regulatory T (Treg) cells occurs in acute myeloid leukemia (AML), but little is known about the role of tumor cells themselves in this process. Here, we showed that an immune checkpoint PD-L1 expressed by AML cells promoted the conversion and expansion of Treg cells sustaining high expression of Foxp3 and PD-1 as well as a suppressive function. Furthermore, an AML cell line HEL overexpressed PD-L1 promoted the conversion and expansion of Treg cells and CD4+PD-1+Foxp3+ T (PD-1+Treg) cells from the conventional CD4+ T cells. CD4+CD25highPD-1+ T cells secreted more IL-10 production than CD4+CD25highPD-1− T cells. IL-35, another cytokine secreted by Treg cells, promoted the proliferation of HL-60 cells and enhanced chemoresistance to cytarabine. Blockade of PD-1 signaling using anti-PD-L1 antibody dramatically impaired the generation of Treg cells and sharply retarded the progression of a murine AML model injected with C1498 cells. The frequency of intratumoral PD-1+ Treg cells was capable of predicting patient survival in patients with AML. In conclusion, our data suggest that PD-L1 expression by AML cells may directly drive Treg cell expansion as a mechanism of immune evasion and the frequency of PD-1+ Treg cells is a potential prognostic predictor in patients with AML.

Migration arrest of chemoresistant leukemia cells mediated by MRTF-SRF pathway

BackgroundDormant chemotherapy-resistant leukemia cells can survive for an extended period before relapse. Nevertheless, the mechanisms underlying the development of chemoresistance in vivo remain unclear.MethodsUsing intravital bone imaging, we characterized the behavior of murine acute myeloid leukemia (AML) cells (C1498) in the bone marrow before and after chemotherapy with cytarabine.ResultsProliferative C1498 cells exhibited high motility in the bone marrow. Cytarabine treatment impaired the motility of residual C1498 cells. However, C1498 cells regained their migration potential after relapse. RNA sequencing revealed that cytarabine treatment promoted MRTF-SRF pathway activation. MRTF inhibition using CCG-203971 augmented the anti-tumor effects of chemotherapy in our AML mouse model, as well as suppressed the migration of chemoresistant C1498 cells.ConclusionsThese results provide novel insight into the role of cell migration arrest on the development of chemoresistance in AML, as well as provide a strong rationale for the modulation of cellular motility as a therapeutic target for refractory AML.

Green synthesis and chemical characterization of gold nanoparticle synthesized using Camellia sinensis leaf aqueous extract for the treatment of acute myeloid leukemia in comparison to daunorubicin in a leukemic mouse model

AbstractAccording to chemotherapeutic properties of medicinal plants, pharmacologists have always tried to synthesize and formulate the new chemotherapeutic supplements or drugs of metallic nanoparticles using plants. In this study, Camellia sinensis leaf aqueous extract‐based gold nanoparticles (AuNPs) are reported for the first time to exert a dietary therapeutic potential compared to Daunorubicin in an animal model of acute myeloid leukemia. The synthesized AuNPs were characterized using different techniques including UV‐Vis., FT‐IR spectroscopy, TEM, EDS, FE‐SEM, and XRD. DPPH free radical scavenging test was done to evaluate the antioxidant potentials of HAuCl4, C. sinensis, AuNPs, and daunorubicin. For the analyzing of cytotoxicity effects of HAuCl4, C. sinensis, AuNPs, and daunorubicin, MTT assay was used on HUVEC, Human HL‐60/vcr, 32D‐FLT3‐ITD, and Murine C1498 cell lines. In vivo design, induction of acute myeloid leukemia was done by 7,12‐Dimethylbenz[a]anthracene (DMBA) in 75 mice. Then, the animals were randomly divided into six subgroups, including control, untreated, HAuCl4, C. sinensis, AuNPs, and daunorubicin. FTIR findings suggested antioxidant compounds in the nanoparticles were the sources of reducing power, reducing gold ions to AuNPs. SEM and TEM images exhibited a uniform spherical morphology and diameters of ~20‐30 nm for the nanoparticles. DPPH test revealed similar antioxidant potentials for daunorubicin and AuNPs. These nanoparticles similar to daunorubicin had low cell viability dose‐dependently against Human HL‐60/vcr, 32D‐FLT3‐ITD, and Murine C1498 cell lines without any cytotoxicity on HUVEC cell line. AuNPs similar to daunorubicin, significantly (p≤0.05) increased the anti‐inflammatory cytokines and the lymphocyte, platelet, and RBC parameters and decreased the weight and volume of liver and spleen, the pro‐inflammatory cytokines, and the total WBC, blast, neutrophil, monocyte, eosinophil, and basophil counts, as compared to the untreated mice. According to the above results, it appears that AuNPs can be used as a chemotherapeutic drug for the treatment of acute myeloid leukemia in the clinical trial.

Green formulation and chemical characterization of Lens culinaris seed aqueous extract conjugated gold nanoparticles for the treatment of acute myeloid leukemia in comparison to mitoxantrone in a leukemic mouse model

The high prevalence of cancer has been increased the rate of studying about the new formulation of chemotherapeutic drugs. In this regards, one of the suitable options is the use of metal nanoparticles for formulating these drugs. In the recent study, Lens culinaris seed aqueous extract conjugated gold nanoparticles (AuNPs) are reported for the first time to exert a dietary therapeutic potential compared to mitoxantrone in an animal model of acute myeloid leukemia. The synthesized AuNPs were characterized using different techniques including UV–Vis., FT‐IR, XRD, FE‐SEM, and TEM. DPPH free radical scavenging test was done to evaluate the antioxidant potentials of HAuCl4, L. culinaris, AuNPs, and mitoxantrone. For the analyzing of cytotoxicity effects of HAuCl4, L. culinaris, AuNPs, and mitoxantrone, MTT assay was used on HUVEC, 32D‐FLT3‐ITD, Human HL‐60/vcr, and Murine C1498 cell lines. In vivo assay, induction of acute myeloid leukemia was done by 7,12‐Dimethylbenz[a]anthracene (DMBA) in 75 mice. Then, the animals were randomly divided into six subgroups, including control, untreated, HAuCl4, L. culinaris, AuNPs, and mitoxantrone. SEM and TEM images showed uniform spherical morphology and average diameters of 10–40 nm for the nanoparticles. DPPH test revealed similar antioxidant potentials for mitoxantrone and AuNPs. Similar to mitoxantrone, AuNPs had low cell viability dose‐dependently against 32D‐FLT3‐ITD, Human HL‐60/vcr, and Murine C1498 cell lines without any cytotoxicity on HUVEC cell line. AuNPs and mitoxantrone significantly (p ≤ 0.05) reduced the weight and volume of liver and spleen, the pro‐inflammatory cytokines, and the total WBC, blast, neutrophil, monocyte, eosinophil, and basophil counts and increased the mRNA expression of Sphingosine‐1‐phosphate receptor‐1 and Sphingosine‐1‐phosphate receptor‐5, the anti‐inflammatory cytokines, and the lymphocyte, platelet, and RBC parameters as compared to the untreated mice. It looks that AuNPs can be administrated as a chemotherapeutic supplement or drug for the treatment of acute myeloid leukemia in the clinical trial.

Effective Murine Model Induction for Niche Study in Immune Cells Against Leukemia.

Murine models have become powerful tools in leukemia research for investigating interactions between blast cells niche factors. In the tumor microenvironment, immune cells are one of the most important niche factors, capable of mounting dynamic innate or adoptive responses against leukemic cells. Acute myeloid leukemia (AML) is a systemic cancer accompanied by immune disruption. In order to exploit the enhanced activity of immune cells in AML treatment, the use of syngeneic mouse models is necessary. Studies of crosstalk between cancer blast cells and immune cells in syngeneic mouse models are beneficial, as the absence of immune functions in syngeneic models enables focus on cancer-associated immune reactions. Once AML is induced, innate and adoptive immune cells respond differently, ultimately resulting in suppression of the immune cells. Murine AML models are commonly induced by intravenous or subcutaneous injection of C1498 cells. Despite the popularity of murine models, they have not yet resulted in the elucidation of distinct differences in immune cells by the injection method. Here, we investigated the frequency of immune cells and survival rate of mice with AML induced using both injection methods.