Mouse Tumor Cell Lines Research Articles

The Wdr5-H3K4me3 Epigenetic Axis Regulates Pancreatic Tumor Immunogenicity and Immune Suppression.

The WDR5/MLL1-H3K4me3 epigenetic axis is often activated in both tumor cells and tumor-infiltrating immune cells to drive various cellular responses in the tumor microenvironment and has been extensively studied in hematopoietic cancer, but its respective functions in tumor cells and immune cells in the context of tumor growth regulation of solid tumor is still incompletely understood. We report here that WDR5 exhibits a higher expression level in human pancreatic tumor tissues compared with adjacent normal pancreas. Moreover, WDR5 expression is negatively correlated with patients' response to chemotherapy or immunotherapy in human colon cancer and melanoma. However, WDR5 expression is positively correlated with the HLA level in human cancer cells, and H3K4me3 enrichment is observed at the promoter region of the HLA-A, HLA-B, and HLA-C genes in pancreatic cancer cells. Using mouse tumor cell lines and in vivo tumor models, we determined that WDR5 deficiency or inhibition significantly represses MHC I expression in vitro and in vivo in pancreatic tumor cells. Mechanistically, we determine that WDR5 deficiency inhibits H3K4me3 deposition at the MHC I (H2K) promoter region to repress MHC I (H2K) transcription. On the other hand, WDR5 depletion leads to the effective downregulation of immune checkpoints and immunosuppressive cytokines, including TGFβ and IL6, in the pancreatic tumor microenvironments. Our data determine that WDR5 not only regulates tumor cell immunogenicity to suppress tumor growth but also activates immune suppressive pathways to promote tumor immune evasion. Selective activation of the WDR5-MHC I pathway and/or selective inhibition of the WDR5-immune checkpoint and WDR5-cytokine pathways should be considered in WDR5-based epigenetic cancer immunotherapy.

Abstract 4690: SC-2882, a novel QPCTL inhibitor, with anti-tumor activity in solid tumor models

Abstract Background: SC-2882 is an orally administered first-in-class small molecule inhibitor of glutaminyl-peptide cyclotransferase like (QPCTL). QPCTL is an intracellular enzyme that modifies several proteins containing an N-terminal glutamine or glutamate, resulting in pyroglutamylated amino acids. Pyroglutamylation can alter protein function in different ways and dependent on context. Key substrate proteins include the “don’t eat me” signal protein CD47 and several chemokines (CCL2 and CCL7) (Nat Med 2019, Nat Imm. 2022). Previously, we have shown activity of SC-2882 in a murine model of diffuse large B-cell lymphoma (Di Siervi, 2023). Here we report for the first time, the evaluation of SC-2882 in several preclinical mouse models for solid tumors. Methods: Potency of SC-2882 was evaluated in a cell-based assay in several human and mouse tumor cell lines: SIRPα binding to CD47 in response to increasing concentrations of SC-2882 was measured in a flowcytometry-based assay. Several syngeneic mouse tumor models were evaluated for their response towards SC-2882 as a single agent and in combination with either a murine anti-PD-L1 antibody or cisplatin. Animals were dosed orally with SC-2882 once daily for the duration of the experiment. Results: In all human and mouse cancer cell lines tested, SC-2882 was able to reduce SIRPα binding to CD47 significantly. This reduction was equivalent to the reduction observed in QPCTL genetic knockouts created in the same cell line. In the same experiments, no differences in CD47 expression were observed. From anti-tumor efficacy studies, we learned that SC-2882 was well tolerated in mice as a single agent and in combination with anti-PD-L1 or cisplatin for at least 4 weeks (this was the maximum period tested). No clinical signs or changes in body weight were observed, even over prolonged periods of treatment. Tumor growth inhibition and tumor shrinkage by SC-2882 was observed in 5 different syngeneic mouse tumor models. In two out of these five models, SC-2882 was able to reduce tumor growth as a single agent. In the other three models, tumor growth inhibition was observed in combination with either anti-PD-L1 or cisplatin. Conclusions: SC-2882 is an orally administered small molecule inhibitor with a favorable PK profile. Preclinical studies show that SC-2882 was well tolerated in mice. In several mouse tumor models, SC-2882 reduced tumor growth in either single agent treated animals or in combination with anti-PD-L1 or cisplatin. SC-2882 is currently in IND enabling studies and scheduled to enter the clinic in 2024. Citation Format: Jasper Mullenders, Marcel Scheepstra, Michel R. Faas, Annette B. Galler, Bastiaan Evers, Jens U. Wuerthner. SC-2882, a novel QPCTL inhibitor, with anti-tumor activity in solid tumor models [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 4690.

Abstract 4044: Potentiated antitumor activity of poly-γ-glutamic acid combined with anti PD-L1 blockade on murine models of colorectal cancer

Abstract Objective: Immune checkpoint inhibitors(ICIs) have been shown to be key role in cancer therapy. Especially, antibodies targeting programmed cell death ligand1(PD-L1) promoted T cells to activate immune response against cancer cells. However, the current ICIs still have insignificant to motivate effective antitumor immunity by blocking PD-1/PD-L1 pathway and the regulatory network of PD-L1 by cytokines in the tumor microenvironment remains to be uncovered. Previously, we have reported the anti-cancer effects of combination treatment with a natural product, poly-γ-glutamic acid(γ-PGA), and PD-1 blockade. Now, we show that combination therapy with anti PD-L1 and γ-PGA can overcome the limits of ICIs and enhance anticancer effect in murine colorectal cancer. Design: In vivo efficacy studies were performed by intraperitoneal injection of antibody targeting PD-L1 and oral administration of γ-PGA in C57BL/6 model transplanted with mouse tumor cell lines. Systemic changes in immunophenotype was measured by tumor volume size and body weight. The splenocyte was isolated from mice and the populations of myeloid-driven suppressor cells(MDSCs) and CD4/CD8 T cells were analyzed by FACS. Also, the significant cytokines activated by T- cell, IFN-γ and IL-2, were measured by ELISA. Results and Conclusions: In murine model of colorectal cancer, γ-PGA and anti PD-L1 blockade combination therapy significantly improved anti-tumor activity compared with single agents. In addition, tumoral infiltration of CD8+ T cells and IFN-γ productions were increased by γ-PGA, and its antitumoral activity was attenuated by antibody-mediated depletion of these cells, indicating that g-PGA suppressed tumor growth in a CD8 T cell-dependent manner. Therefore, our results suggest that γ-PGA promote ICI-mediated antitumor responses by the transformation of "cold tumors" into “hot tumors” Citation Format: Jae-Pyung Jang, Chan-Hee Yoo, Kyung-Soo Hahm, Do Young Lee, Young-Chul Park, Jae Chul Choi. Potentiated antitumor activity of poly-γ-glutamic acid combined with anti PD-L1 blockade on murine models of colorectal 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 4044.

Abstract 7213: Tumor targeted activation of an attenuated exatecan protodrug through Click Chemistry demonstrates efficacy in murine tumor studies

Abstract Shasqi is advancing the Click Activated Protodrugs Against Cancer (CAPAC®) platform based on click chemistry, a Nobel Prize winning technology. The platform is modular and comprises 1) an activator that target specific antigens, and 2) inert cancer drugs, protodrugs, which are selectively activated at tumors via click chemistry. The CAPAC technology separates the tumor targeting function from the payload and re-unites them at the tumor creating the flexibility to optimize activity while limiting toxicity during preclinical and clinical development. The modularity of the platform enables the rapid development of new therapies as well as unlocking unique treatment benefits such as tunable combinations and payload cycling. We envision that CAPAC will expand the scope of potential targets, widen the therapeutic window, and enhance the safety of locally activated cancer therapeutics. Here, we demonstrate the efficacy and safety of our exatecan protodrug (SQP07) used with intratumorally injected activators. The activators, tetrazine-modified sodium hyaluronate biopolymer(s), are injected at the tumor site and followed by a systemic dose of SQP07, a trans-cyclooctene (TCO)-modified protodrug of exatecan (Exa). An efficient covalent reaction between tetrazine and TCO moieties releases active Exa at the tumor. In vitro cytotoxicity studies showed that SQP07 activated with tetrazine was effective against mouse and human tumor cell lines (MC38, CT26, EMT6 and NCI-N87); SQP07 without activator had potency attenuated by 60-133 fold. In vivo tumor distribution and activity of SQP07 with the intratumoral biopolymer activators was evaluated in an NCI-N87 gastric cancer xenograft model. Female C.B-17 SCID mice received a single intravenous dose of vehicle (10% HPCD), Exa (50 mg/kg) or biopolymer (40 or 100 μL intratumorally) followed by SQP07 or SQP07 alone (50 mg/kg Exa mol equivalent). 1 hour after biopolymer + SQP07 treatment, activated Exa was highly concentrated in the tumor and stroma. This led to tumor regression in animals up to 40 days, performing significantly better than the free drug cytotoxic, Exa alone. Similarly, median survival with biopolymer + SQP07 was higher (>81 days) compared to Exa (68.5 days). Toxicity, measured as body weight loss, was comparable (~5%) and transient between Exa and biopolymer + SQP07. SQP07 alone treatment without the biopolymer was not differentiated from the vehicle control. These data show that the CAPAC platform, which separates the targeting agent from the payload, is an effective way to administer cytotoxic therapies systemically. Additional work with other tumor models, different biopolymers and the SQP07 protodrug is ongoing. Citation Format: Sangeetha Srinivasan, Stefanie Wagner, George Coricor, Tri-Hung Nguyen, Jesse M. McFarland, José M. Mejía Oneto. Tumor targeted activation of an attenuated exatecan protodrug through Click Chemistry demonstrates efficacy in murine tumor 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 7213.

Abstract 85: Immunomics of immune-deficient mouse models before and after CD34 humanization

Abstract Preclinical tumor oncology research relies historically on the analysis of mouse or human tumor cell lines implanted onto severely immune-deficient mouse models carrying nude, SCID or Rag mutations on different genetical background (C57Bl/6N, BalbC, NMRI, CB17 or NOD). These lines harbor defects in several leukocyte lineages among which Tc, Bc and NKc might be affected. Humanized mice are emerging models that have been transplanted with human cells or tissues (and/or equipped with human transgenes). Currently, the most advanced strains are the nonobese diabetic, severe combined immunodeficiency (NOD-SCID) mouse with complete disruptions in the interleukin-2 (IL-2) common γ-chain (IL2R γ null) receptor (NSG) and BALB/c Rag2−/− IL2R γ null SirpaNOD mice (BRGS).1 Neonate or juvenile chimera are reconstituted in NSG, BRGS or B6 RGS with CD34+ hematopoietic progenitor cell (HPCs) from human cord blood yielding robust engraftment of a human immune system (HIS).. We genetically modified the mouse genome introducing mutations involved in Tc, Bc and NKc development. We then immuno-phenotyped over 23 lines of mouse mutants produced from the same animal house to minimize the impact of microbiota on innate immune cell populations. High content cytometry analysis of several organs was performed in a standardized manner before and after humanization. The resource obtained of these immunotypes was used to highlight similarities and differences among these lines across several genetical background and will help in selecting the most appropriate model to use for tumor implantation and CD34 or PBMC humanization. Citation Format: Hervé Luche, Lilia Hadjem, Marielle Mello, Priscilla Canavese, Fabien Angelis, Anais Joachim, Sylvie Bouilly, Frédéric Guinut, Frederic Fiore, Bernard Malissen, Ana Zarubica, Erwan Corcuff. Immunomics of immune-deficient mouse models before and after CD34 humanization [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 85.

Trimethyltin(IV) Bearing 3-(4-Methyl-2-oxoquinolin-1(2H)-yl)propanoate Causes Lipid Peroxidation-Mediated Autophagic Cell Death in Human Melanoma A375 Cells.

A novel trimethyltin(IV) complex (Me3SnL), derived from 3-(4-methyl-2-oxoquinolin-1(2H)-yl)propanoate ligand, has been synthesized and characterized by elemental microanalysis, UV/Vis spectrophotometry, FT-IR and multinuclear (1H, 13C and 119Sn) NMR spectroscopies. Furthermore, the structure of the ligand precursor HL was solved using SC-XRD (single-crystal X-ray diffraction). The prediction of UV/Vis and NMR spectra by quantum-chemical methods was performed and compared to experimental findings. The protein binding affinity of Me3SnL towards BSA was determined by spectrofluorometric titration and subsequent molecular docking simulations. Me3SnL has been evaluated for its in vitro anticancer activity against three human cell lines, MCF-7 (breast adenocarcinoma), A375 (melanoma) and HCT116 (colorectal carcinoma), and three mouse tumor cell lines, 4T1 (breast carcinoma), B16 (melanoma) and CT26 (colon carcinoma), using MTT and CV assays. The strong inhibition of A375 cell proliferation, ROS/RNS upregulation and robust lipid peroxidation lead to autophagic cell death upon treatment with Me3SnL.

Aspartate β-hydroxylase Regulates Expression of Ly6 Genes.

Background: Overexpression of aspartate β-hydroxylase (ASPH) in human tumors contributes to their progression by stimulating cell proliferation, migration, and invasion. Several signaling pathways affected by ASPH have been identified, but the high number of potential targets of ASPH hydroxylation suggests that additional mechanisms may be involved. This study was performed to reveal new targets of ASPH signaling. Methods: The effect of ASPH on the oncogenicity of three mouse tumor cell lines was tested using proliferation assays, transwell assays, and spheroid invasion assays after inhibition of ASPH with the small molecule inhibitor MO-I-1151. ASPH was also deactivated with the CRISPR/Cas9 system. A transcriptomic analysis was then performed with bulk RNA sequencing and differential gene expression was evaluated. Expression data were verified by quantitative PCR and immunoblotting. Results: Inhibition or abrogation of ASPH reduced proliferation of the cell lines and their migration and invasiveness. Among the genes with differential expression in more than one cell line, two members of the lymphocyte antigen 6 (Ly6) family, Ly6a and Ly6c1, were found. Their downregulation was confirmed at the protein level by immunoblotting, which also showed their reduction after ASPH inhibition in other mouse cell lines. Reduced production of the Ly6D and Ly6K proteins was shown after ASPH inhibition in human tumor cell lines. Conclusions: Since increased expression of Ly6 genes is associated with the development and progression of both mouse and human tumors, these results suggest a novel mechanism of ASPH oncogenicity and support the utility of ASPH as a target for cancer therapy.

Characterization, modes of interactions with DNA/BSA biomolecules and anti-tumor activity of newly synthesized dinuclear platinum(II) complexes with pyridazine bridging ligand.

Platinum-based drugs are widely recognized efficient anti-tumor agents, but faced with multiple undesirable effects. Here, four dinuclear platinum(II) complexes, [{Pt(1,2-pn)Cl}2(μ-pydz)]Cl2 (C1), [{Pt(ibn)Cl}2(μ-pydz)]Cl2 (C2), [{Pt(1,3-pn)Cl}2(μ-pydz)]Cl2 (C3) and [{Pt(1,3-pnd)Cl}2(μ-pydz)]Cl2 (C4), were designed (pydz is pyridazine, 1,2-pn is ( ±)-1,2-propylenediamine, ibn is 1,2-diamino-2-methylpropane, 1,3-pn is 1,3-propylenediamine, and 1,3-pnd is 1,3-pentanediamine). Interactions and binding ability of C1-C4 complexes with calf thymus DNA (CT-DNA) has been monitored by viscosity measurements, UV-Vis, fluorescence emission spectroscopy and molecular docking. Binding affinities of C1-C4 complexes to the bovine serum albumin (BSA) has been monitored by fluorescence emission spectroscopy. The tested complexes exhibit variable cytotoxicity toward different mouse and human tumor cell lines. C2 shows the most potent cytotoxicity, especially against mouse (4T1) and human (MDA-MD468) breast cancer cells in the dose- and time-dependent manner. C2 induces 4T1 and MDA-MD468 cells apoptosis, further documented by the accumulation of cells at sub-G1 phase of cell cycle and increase of executive caspase 3 and caspase 9 levels in 4T1 cells. C2 exhibits anti-proliferative effect through the reduction of cyclin D3 and cyclin E expression and elevation of inhibitor p27 level. Also, C2 downregulates c-Myc and phosphorylated AKT, oncogenes involved in the control of tumor cell proliferation and death. In order to measure the amount of platinum(II) complexes taken up by the cells, the cellular platinum content were quantified. However, C2 failed to inhibit mouse breast cancer growth in vivo. Chemical modifications of tested platinum(II) complexes might be a valuable approach for the improvement of their anti-tumor activity, especially effects in vivo.

Novel diphenyltin(IV) complexes with carboxylato N-functionalized 2-quinolone ligands: Synthesis, characterization and in vitro anticancer studies

Three new diphenyltin(IV) complexes, bis(3-(4-methyl-2-oxoquinolinyl-1(2H)-yl)propanoato)diphenyltin(IV) (1), bis(2-(4-methyl-2-oxoquinolin-1(2H)-yl)ethanoato)diphenyltin(IV) (2), and bis(2-(4-hydroxy-2-oxoquinolin-1(2H)-yl)ethanoato)diphenyltin(IV) (3), were synthesized and characterized by elemental microanalysis, FT-IR spectroscopy, and multinuclear (1H, 13C and 119Sn) NMR spectroscopy. Crystal structure of ligand precursor, 2-(4-methyl-2-oxoquinolinyl-1-(2H)-yl)acetic acid (HL2), has been determined by X-ray diffraction studies. Asymmetric bidentate coordination of the carboxylato ligands and skew trapezoidal structures are assumed for the synthesized complexes. In vitro anticancer activity of the synthesized diphenyltin(IV) complexes was evaluated against three human: MCF-7 (breast adenocarcinoma), A375 (melanoma), HCT116 (colorectal carcinoma), and three mouse tumor cell lines: 4T1 (breast carcinoma), B16 (melanoma), CT26 (colon carcinoma) using MTT and CV assays. The IC50 values fall in the range from 0.1 to 3.7 μM. Flow cytometric analysis and fluorescent microscopy suggest that complex 1 induces caspase-dependent apoptosis followed with strong blockade of cell division in HCT116 cells. Since complex 1 showed ROS/RNS scavenging potential mentioned cytotoxicity was not connected with oxidative stress.

Xianlinglianxiafang Inhibited the growth and metastasis of triple-negative breast cancer via activating PPARγ/AMPK signaling pathway

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by high invasion and metastasis rates. Xian-Ling-Lian-Xia formula (XLLX) is a traditional Chinese medicine prescription widely used in China for treating TNBC. Clinical studies have shown that XLLX significantly reduces the recurrence and metastasis rate of TNBC and improves disease-free survival. However, the potential molecular mechanisms of XLLX on TNBC are not clear yet. Here, we investigated the effects of XLLX on TNBC using a mouse model and tumor cell lines. The results showed that XLLX significantly inhibited the proliferation, migration, and invasion abilities of TNBC cell lines MDA-MB-231 and 4T1 in vitro, induced apoptosis, and regulated the expression of proliferation, apoptosis, and EMT marker proteins in tumor cells. In in vivo experiments, XLLX treatment significantly reduced the progression of TNBC tumors and lung metastasis. Transcriptomics reveals that XLLX treatment significantly enriched differentially expressed genes in the peroxisome proliferator-activated receptor gamma (PPARγ) and AMP-dependent protein kinase (AMPK) signaling pathways. The western blot results confirmed that XLLX significantly upregulated the protein expression of PPARγ and p-AMPK in TNBC cells, tumors, and lung tissues. It is noteworthy that GW9662 (a PPARγ inhibitor) and Compound C (an AMPK inhibitor) partially reversed the anti-proliferation and anti-metastasis effects of XLLX in TNBC cells. Therefore, XLLX may effectively inhibit the growth and metastasis of TNBC by activating the PPARγ/AMPK signaling pathway.

Ursane-Type Triterpenes with a Phenylpropanoid Unit from Camellia ptilosperma and Evaluation of Their Cytotoxic Activities.

Six new ursane-type triterpenes with a phenylpropanoid unit and five known oleanane-type triterpenes were isolated from the leaves of Camellia ptilosperma. The undescribed compounds were identified by analysis of 1D and 2D NMR and HRESIMS spectroscopic data as ptilospermanols A-F. The cytotoxicity of new compounds against six human cancer cell lines and three mouse tumor cell lines was evaluated by MTT assay.

Targeting CD47 in lymphoid malignancies with CAR T cells.

2513 Background: Despite major therapeutic advances of chimeric antigen receptor (CAR) T cells directed against CD19 in relapsed and refractory non-Hodgkin lymphoma (NHL), two thirds of patients experience relapse within the first two years. Nearly one third of these relapses are associated with CD19 antigen-loss escape thus leveraging alternate CAR targets may improve outcomes. CD47, an anti-phagocytic “don’t eat me” receptor known to be overexpressed in NHL, is an ideal CAR target as it is potentially indispensable for tumor progression. Methods: CD47-CAR binding domains were engineered either as a camelid single variable heavy chain nanobody (CD47-VHH-CAR) or as the CD47 binding domain of cognate receptor SIRPα (SIRPα-CAR), each combined with a CD28 costimulatory domain and a CD3ζ activation domain with two mutated ITAMs (1XX). In vitro co-culture assays were performed with lymphoid mouse tumor cell lines BM185 and A20. For in vivo experiments, syngeneic BALB/c mice were sublethally irradiated for lymphodepletion then injected intravenously with 1x105 luciferase+ BM185 cells. Two days later, mice were injected with 2x106 CAR T cells, and bioluminescence imaging was performed to monitor tumor progression. For bio-localization experiments, CAR T cells were co-transduced with a separate vector encoding luciferase. Results: CD47-CAR T cell expansion in vitro was hindered due to fratricide, which can be rescued by CD47 CRISPR knockout. Both CD47-VHH-CAR and SIRPa-CAR T cells exhibited potent and specific in vitro lysis of BM185 and A20 cells. CD47-VHH-CAR T cells showed transient anti-leukemia activity, however, survival was not significantly prolonged. T cell bio-localization analysis revealed that, compared to CD19-CAR T cells, CD47-VHH-CAR T cells exhibited prolonged retention in the thorax with minimal bone marrow trafficking, suggesting CD47 antigen-specific pulmonary sequestration, and inferior expansion. SIRPα-CAR T cells engineered to secrete pro-inflammatory cytokine IL-18 significantly improved CAR T cell expansion, resulting in bone marrow trafficking and clearance of BM185 tumor. However, recipients of IL-18-secreting SIRPa-CAR T cells experienced lethal CAR T cell-related toxicity. To improve the safety of CD47-CAR T cells, we engineered an NFAT-responsive vector expressing the CD47-CAR modified with E. coli-derived dihydrofolate reductase drug destabilization domain to limit CD47-CAR expression to T cells exposed to the stabilizing antibiotic trimethoprim and receiving a licensing NFAT signal from a CD19-CAR. Conclusions: In vivo activity of CD47-targeting CAR T cells is limited by thoracic retention and limited expansion, which can be partially overcome by overexpression of IL-18, though enhanced toxicity precludes survival prolongation. Our findings suggest that strategies to spatiotemporally restrict CAR expression or activation will be necessary to achieve safe and efficacious CD47-CAR T cell activity.

Abstract IA01: Targeting KRAS: Light at the end of the tunnel

Abstract KRAS, an oncogene responsible for at least one fourth of all human cancers, was discovered four decades ago. Yet, the first KRAS selective inhibitor could not be approved until 2021. In spite of this long-awaited breakthrough, approved KRAS inhibitors only block one of the multiple oncogenic isoforms, KRASG12C, an isoform primarily present in lung adenocarcinomas. Moreover, tumor resistance to these KRAS inhibitors is becoming a significant issue in the clinic (Awad et al., N Engl J Med, 2021; Zhao et al., Nature 2021). To provide experimental information that might help to improve current KRAS targeting strategies, we have generated two experimental mouse tumor models of Kras-driven lung adenocarcinoma to compare the therapeutic consequences of eliminating, instead of inhibiting, KRAS oncoproteins. In addition, we have interrogated the molecular mechanisms responsible for the induction of resistance in sotorasib treated KrasG12C/p53 mouse lung adenocarcinomas. We have also investigated the potential role of tampering with KRAS signaling pathways to develop alternative therapeutic strategies against KRAS mutant lung and pancreatic cancers. Previous studies have shown that ablation of RAF1, either by itself, or in combination with the expression of a CDK4 kinase dead isoform, induce significant levels of tumor regression in Kras/p53 driven-lung adenocarcinomas without inducing significant toxicities (Sanclemente et al. Cancer Cell, 2018; Esteban-Burgos et al., PNAS 2020). However, Kras/p53 driven-pancreatic ductal adenocarcinomas (PDAC) are completely resistant to RAF1 ablation, unless RAF1 is deleted in combination with EGFR, an upstream KRAS effector (Blasco et al, Cancer Cell 2019). Yet, ablation of RAF1 and EGFR only resulted in the complete regression of a fraction of PDAC tumors. We have now identified activation of STAT3 as the main mechanism responsible for the resistance of PDAC tumors to RAF1/EGFR ablation. Indeed, combined ablation of RAF1/EGFR/STAT3 completely blocked proliferation of all tested mouse tumor cell lines and organoids. Moreover, all tumors tested in orthotopic allograft models regressed completely with no evidence of tumor regression for at least two months of TMX exposure. Finally, I will discuss potential strategies to pharmacologically validate this triple therapeutic strategy as well as plans to combine it with current KRAS inhibitors. Citation Format: Mariano Barbacid. Targeting KRAS: Light at the end of the tunnel [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr IA01.

Abstract 5190: Systematic immune-profiling of immune-deficient mouse models: A rational to select ideal host for tumor implantation

Abstract Preclinical tumor oncology research relies historically on the analysis of mouse or human tumor cell lines implanted onto severely immune-deficient mouse models carrying nude, SCID or Rag mutations on different genetical background (C57Bl/6N, BalbC, NMRI, CB17 or NOD). These lines harbor defects in several leukocyte lineages among which Tc, Bc and NKc might be affected. Humanized mice are emerging models that have been transplanted with human cells or tissues (and/or equipped with human transgenes). Currently, the most advanced strains are the nonobese diabetic, severe combined immunodeficiency (NOD-SCID) mouse with complete disruptions in the interleukin-2 (IL-2) common γ-chain (IL2R γ null) receptor (NSG) and BALB/c Rag2−/− IL2R γ null SirpaNOD mice (BRGS).1 Juvenile chimera NSG or BRGS are reconstituted with hematopoietic progenitor cell (HPCs) from human cord blood yielding robust engraftment of a human immune system (HIS).. Recent work showing the binding of human IgG4 to mouse FcgR receptor reducing clinical efficacy of therapeutic antibodies highlights the need to characterize extensively the residual immune system present in these models prior humanization in order to precisely evaluate immunotherapies. In other to fulfill this task, we genetically modified the mouse genome introducing mutations involved in Tc, Bc and NKc development. We then immuno-phenotyped over 20 lines of mouse mutants produced from the same animal house to minimize the impact of microbiota on innate immune cell populations. High content cytometry analysis of BM, spleen, thymus and peripheral blood was performed in a standardized manner. The resource obtained of these immunotypes was used to highlight similarities and differences among these lines across several genetical background. This work has shown instrumental in selecting the most appropriate model to use for humanization followed before tumor implantation. Citation Format: Hervé Luche, Lillia Hadjem, Marielle Mello, Priscilla Canavese, Fabien Angelis, Anais Joachim, Sylvie Bouilly, Frederic Guinut, Frederic Fiore, Bernard Malissen, Ana Zarubica, Erwan Corcuff. Systematic immune-profiling of immune-deficient mouse models: A rational to select ideal host for tumor implantation. [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 5190.

Epigenetically controlled tumor antigens derived from splice junctions between exons and transposable elements.

Oncogenesis often implicates epigenetic alterations, including derepression of transposable elements (TEs) and defects in alternative splicing. Here, we explore the possibility that noncanonical splice junctions between exons and TEs represent a source of tumor-specific antigens. We show that mouse normal tissues and tumor cell lines express wide but distinct ranges of mRNA junctions between exons and TEs, some of which are tumor specific. Immunopeptidome analyses in tumor cell lines identified peptides derived from exon-TE splicing junctions associated to MHC-I molecules. Exon-TE junction-derived peptides were immunogenic in tumor-bearing mice. Both prophylactic and therapeutic vaccinations with junction-derived peptides delayed tumor growth in vivo. Inactivation of the TE-silencing histone 3-lysine 9 methyltransferase Setdb1 caused overexpression of new immunogenic junctions in tumor cells. Our results identify exon-TE splicing junctions as epigenetically controlled, immunogenic, and protective tumor antigens in mice, opening possibilities for tumor targeting and vaccination in patients with cancer.

A pan-tumor-siRNA aptamer chimera to block nonsense-mediated mRNA decay inflames and suppresses tumor progression

Immune-checkpoint blockade (ICB) therapy has changed the clinical outcome of many types of aggressive tumors, but there still remain many cancer patients that do not respond to these treatments. There is an unmet need to develop a feasible clinical therapeutic platform to increase the rate of response to ICB. Here we use a previously described clinically tested aptamer (AS1411) conjugated with SMG1 RNAi (AS1411-SMG1 aptamer-linked siRNA chimeras [AsiCs]) to inhibit the nonsense-mediated RNA decay pathway inducing tumor inflammation and improving response to ICB. The aptamer AS1411 shows binding to numerous mouse and human tumor cell lines tested. AS1411 induces tumor cytotoxicity in long incubation times, which allows for the use of the aptamer as a carrier to target the RNAi inhibition to the tumor. The AS1411-SMG1 AsiCs induce a strong antitumor response in local and systemic treatment in different types of tumors. Finally, AS1411-SMG1 AsiCs are well tolerated with no detected side effects.

Overcoming resistance to αPD-1 of MMR-deficient tumors with high tumor-induced neutrophils levels by combination of αCTLA-4 and αPD-1 blockers

BackgroundClinical studies have highlighted the efficacy of anti-programmed death 1 (αPD-1) monoclonal antibodies in patients with DNA mismatch repair-deficient (MMRD) tumors. However, the responsiveness of MMRD cancers to αPD-1 therapy...

Abstract 5590: Inhibition of the autophagy protein Vps34 induces tumor cell secretion of proinflammatory chemokines

Abstract Autophagy is the cellular process by which cytoplasmic contents are degraded and recycled through a lysosomal pathway. In cancer, autophagy can contribute to both tumor promotion and tumor suppression, and emerging evidence supports a role in resistance to immunotherapy. We investigated whether inhibition of autophagy with a small molecule inhibitor of the class III phosphoinositide 3-kinase Vps34 could stimulate anti-tumor immune responses and potentiate the efficacy of immune checkpoint blockade (ICB). Treatment with the Vps34 inhibitor (Vps34i) inhibited autophagy and was weakly cytotoxic to B16F10, MC38, EMT6 and CT26 mouse syngeneic tumor cell lines. In certain cancers, autophagy has been linked to lysosomal degradation of MHC I proteins, thereby downregulating expression and contributing to immune evasion. Notably, we observed minimal upregulation of MHC I surface expression on a subset of mouse and human cell lines. We further explored whether autophagy inhibition would result in release of any soluble immune stimulatory factors from mouse tumor cell lines. Inhibition of Vps34 markedly increased the secretion of several proinflammatory chemokines, including CCL5 and CXCL10. Increased chemokine secretion was also observed in a panel of human cancer cell lines, including NCI-H2009 lung cancer and PC-3 prostate cancer, confirming that the response is observed in human cancer cell lines derived from different tissue origins. As the chemokines CCL5 and CXCL10 are critical to the development of robust anti-tumor immunity, we next tested whether Vps34i treatment could potentiate the anti-tumor efficacy of ICB. We explored the activity of Vps34i as a single agent and in combination with anti-PD-1 antibody in three different syngeneic tumor models, including EMT6, CT26 and MC38. No single agent activity was observed in these models, however, combination of anti-PD-1 and Vps34i significantly inhibited the growth of CT26 tumors compared to control. Anti-tumor efficacy of combination treatment was not significantly different compared to single agents, and no complete tumor regressions were observed. No significant increases in CCL5 and CXCL10 were observed in the serum of combination treated mice, potentially explaining the lack of robust efficacy. Our results suggest that inhibition of autophagy promotes the secretion of proinflammatory cytokines from mouse and human cancer cells in vitro. As the autophagy pathway exhibits cross talk with other major cell signaling pathways, the tumor contexture may be a critical determinant of the role of autophagy in anti-tumor immune responses. Future experiments will explore which tumor contexts are sensitive to combination of autophagy inhibition and ICB. Citation Format: Marie Bernardo, Yu-an Zhang, Martin Graf, Jane Cheng, Fangxian Sun, Virna Cortez-Retamozo, Sukhvinder Sidhu, Eladio Marquez, Donald Jackson, Jack Pollard, Timothy R. Wagenaar, Donald Shaffer. Inhibition of the autophagy protein Vps34 induces tumor cell secretion of proinflammatory chemokines [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 5590.

Abstract 6024: Developing a panel of orthotopic syngeneic tumor models for IO drug discovery

Abstract Immuno-oncology (IO) therapy is the focus of drug discovery in recent years. Unlike chemotherapy or targeted agents, the pharmacological efficacy of immune-oncology therapies needs to be evaluated in animal models with functional immune system. Syngeneic tumor models are established by inoculating mouse cancer cell lines to immunocompetent mice with the same genetic background. The host mice have complete immune activity and show histocompatibility with homograft tumor tissues, which can maximize the simulation of the real tumor microenvironment. Subcutaneous syngeneic models are easily established and have been widely used; however, the subcutaneous tumors lack organ-specific stromal-tumor interactions that are critical for disease progression in patients. Orthotopic tumor models are established in organ-specific sites, facilitating metastatic spread, supporting immune and stromal component interactions, and providing a more disease-relevant tumor microenvironment for IO therapy assessment. In order to facilitate the development of IO drug, we have established a panel of orthotopic syngeneic tumor models. We generated a series of luciferase-labeled bioluminescent mouse tumor cell lines, which were then engrafted into the organ of interest to establish orthotopic models. Bioluminescent imaging (BLI) enabled non-invasive in vivo imaging of orthotopic tumor burden, the real time tumor growth, and the response to therapies, monitored by quantitative bioluminescent signals. Overall, these established orthotopic syngeneic tumor models recapitulate the clinically relevant tumor microenvironment and serve as a useful tool in the pre-clinical evaluation of immunotherapies. Citation Format: Gaoxiang Liu, Quanhong Sun, Wenting Shi, Qingyang Gu, Qunsheng Ji. Developing a panel of orthotopic syngeneic tumor models for IO drug discovery [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 6024.

Impact of Boosting NAD on Immune Function: Results From NR Preclinical Studies

ObjectivesImmune responses to stress, inflammation, or infections utilize nicotinamide adenine dinucleotide (NAD) resources through upregulation of NAD-dependent cellular repair enzymes such as sirtuins and PARPs as well as other immune cell functions. Preclinical studies have demonstrated that disruptions in NAD metabolism are associated with impaired immune function and inflammation, while utilization of NAD precursors improves immune function and decreases expression of inflammatory markers. The objective of this analysis was to evaluate how supplementation with the NAD precursor, nicotinamide riboside (NR), influences immune cell function and markers of inflammation in preclinical models.MethodsA systematic evaluation of peer-reviewed preclinical publications was conducted to identify the influence of NR supplementation on indicators of inflammation or immune function. Following study reviews, an assessment of gaps in the literature were determined.ResultsThere were 7 primary studies that met the inclusion criteria of measuring NR supplementation alone with an outcome related to inflammatory markers or immune cell function. There was appreciable heterogeneity in the cell types and animal models evaluated, as well as the inflammatory or immune challenge. Of these studies, six measured TNF-α, three measured IL1ß, and four measured IL6; other markers were measured sporadically. NAD levels were shown to decline following an inflammatory or immune trigger in five studies. One study showed an increase in expression of NMRK1 which is integral in the utilization of NR and decreased viral infectivity with NR supplementation. A decrease in TNF-α, IL1ß, and IL6 was observed in most of the studies with one study showing no change. This study measured these markers in CD8 + tumor-infiltrating lymphocytes and mouse tumor cell lines as part of their overall outcome showing a beneficial effect of NR on tumor growth, unique among the studies included.ConclusionsNR supplementation in preclinical models has shown some potential for supporting immune health and reducing inflammation. Future studies that incorporate markers inflammatory status and immune support as primary endpoints, as well as measurements of NAD metabolism are needed to fully assess NR as a modulator of inflammation and identify the mechanisms of action.Funding SourcesNone.