Transplantable Tumors Research Articles

Abstract PO3-24-10: Losartan enhances the radiosensitivity of triple-negative breast cancer by reshaping the tumor immune microenvironment

Abstract Triple-negative breast cancer (TNBC) represents the most aggressive subtype of breast cancer, and the therapeutic options available for TNBC are limited. In addition to surgery and chemotherapy, radiotherapy (RT) is a primary treatment modality for TNBC. However, radio-resistance poses significant challenges to TNBC treatment. Prior research has shown that losartan, an angiotensin receptor blocker, can improve vessel perfusion and drug delivery, thereby enhancing the efficacy of chemotherapy or radiotherapy in cancer. However, in our study, we found that losartan could enhance the radiosensitivity of TNBC in immunocompetent mice model, but not in immunodeficient mice model and TNBC cells. It suggested that losartan might enhance the radiosensitivity of TNBC in an immune system dependent way. Previous studies had noted that tumor immune microenvironment (TIME) played an important role in radio-resistance. Therefore, we focused on the TIME in our further study. For immune cells, it had reported that the recruitment and activation of immunosuppressive cells such as M2 phenotype tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), could lead to the establishment of and immunosuppressive TIME and decreased the radiosensitivity. In this study, we found losartan facilitated the polarization of TAMs towards the M1 phenotype, and impeded the immunosuppressive function of MDSCs after RT in 4T1 TNBC mice model. Additionally, losartan also caused a significant increase of CD8+ T lymphocytes in the TIME, and also markedly enhanced the activity of infiltrated T cell. When the CD8+ T cells were eliminated by anti-CD8α antibody, the radiosensitization effect of losartan was significantly decreased. Therefore, T-cell mediated tumor suppression is essential for the radiosensitization caused by losartan in TNBC. For immune factors, we found that TNBC exhibited an increase in the expression of programmed death-ligand (PD-L1) and indoleamine-2,3-dioxygenase (IDO) upon exposure to irradiation, and the combination of losartan resulted in a significant reduction in their expression in vitro and in vivo. At the same time, the 4T1 TNBC transplantation tumors were significantly inhibited by losartan combined with PD-1 inhibitor after RT, which indicated that losartan might amplify the efficacy of radio-immunotherapy. Collectively, these findings suggest that losartan could reshape the TIME of TNBC through regulating immune cells (TAMs, MDCSs and CD8+ T cells) and immune factors (PD-L1 and IDO), which result in the enhancement of radiosensitivity of TNBC. In our investigation, losartan was innovatively found to increase the radiosensitivity of TNBC by reshaping the TIME rather than on the tumor stroma. As one of the most commonly prescribed drugs for hypertension, the safety and affordability of losartan have been extensively confirmed. In the future, losartan combined with radiotherapy might be a promising strategy for TNBC treatment. Citation Format: Cuiwei Liu, Xu Wang, Zihan Xia, Yuxi Ma, Yanxia Zhao. Losartan enhances the radiosensitivity of triple-negative breast cancer by reshaping the tumor immune microenvironment [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-24-10.

Generation of a novel agonist of the human CD137 costimulatory pathway for cancer immunotherapy

Abstract The use of immune checkpoint stimulators is an increasingly attractive therapeutic approach against cancer, and costimulatory pathway agonists are being developed for clinical use. Our laboratory has focused on the 4-1BB (CD137) pathway because of its critical role in CD8+ T cell expansion, survival, acquisition of effector function, and establishment of long-term memory. We previously reported the generation of a recombinant oligomeric form of the mouse ligand, muSA-4-1BBL, which, unlike the natural 4-1BB ligand, demonstrated robust costimulatory activity in soluble form. muSA-4-1BBL showed therapeutic efficacy as the immune adjuvant component of subunit vaccines in various mouse transplantable tumor models. In this study, we generated a human version of this ligand, huSA-4-1BBL, and characterized its structure and function. The molecule binds to 4-1BB on LPS-activated human THP-1 monocytes, but not ConA-stimulated mouse T cells expressing the 4-1BB receptor. Conversely, muSA-4-1BBL binds to ConA-stimulated mouse T cells, but not LPS-activated human THP-1 cells, demonstrating species-specific binding for both molecules. To assess the cancer immunotherapeutic efficacy of huSA-4-1BBL, we generated a transgenic mouse model where mouse 4-1BB was replaced with the human ortholog. The assessment of huSA-4-1BBL anti-tumor efficacy in this model will serve as a prelude for further development and translation of this novel agonist to the clinic for cancer immunotherapy.

The Application of 2d Mxene Nanosheet -Based Thermosensitive Gel Delivery System Loaded with Cisplatin and Imiquimod for Lung Cancer.

Lung cancer's high incidence and dismal prognosis with traditional treatments like surgery and radiotherapy necessitate innovative approaches. Despite advancements in nanotherapy, the limitations of single-treatment modalities and significant side effects persist. To tackle lung cancer effectively, we devised a temperature-sensitive hydrogel-based local injection system with near-infrared triggered drug release. Utilizing 2D MXene nanosheets as carriers loaded with R837 and cisplatin (DDP), encapsulated within a temperature-sensitive hydrogel-forming PEG-MXene@DDP@R837@SHDS (MDR@SHDS), we administered in situ injections of MDR@SHDS into tumor tissues combined with photothermal therapy (PTT). The immune adjuvant R837 enhances dendritic cell (DC) maturation and tumor cell phagocytosis, while PTT induces tumor cell apoptosis and necrosis by converting light energy into heat energy. Material characterization employed transmission electron microscopy, X-ray photoelectron spectroscopy, phase transition temperature, and near-infrared thermography. In vitro experiments assessed Lewis cell proliferation and apoptosis using CCK-8, Edu, and TUNEL assays. In vivo experiments on C57 mouse Lewis transplant tumors evaluated the photothermal effect via near-infrared thermography and assessed DC maturation and CD4+/CD8+ T cell ratios using flow cytometry. The in vivo anti-tumor efficacy of MDR@SHDS was confirmed by tumor growth curve recording and HE and TUNEL staining of tumor sections. The hydrogel exhibited excellent temperature sensitivity, controlled release properties, and high biocompatibility. In vitro experiments revealed that MDR@SHDS combined with PTT had a greater inhibitory effect on tumor cell proliferation compared to MDR@SHD alone. Combining local immunotherapy, chemotherapy, and PTT yielded superior anti-tumor effects than individual treatments. MDR@SHDS, with its simplicity, biocompatibility, and enhanced anti-tumor effects in combination with PTT, presents a promising therapeutic approach for lung cancer treatment, offering potential clinical utility.

QiDongNing induces lung cancer cell apoptosis via triggering P53/DRP1-mediated mitochondrial fission.

Non-small-cell lung cancer (NSCLC) is a major cause of worldwide cancer death, posing a challenge for effective treatment. Our previous findings showed that Chinese herbal medicine (CHM) QiDongNing (QDN) could upregulate the expression of p53 and trigger cell apoptosis in NSCLC. Here, our objective was to investigate the mechanisms of QDN-induced apoptosis enhancement. We chose A549 and NCI-H460 cells for validation invitro, and LLC cells were applied to form a subcutaneous transplantation tumour model for validation in more depth. Our findings indicated that QDN inhibited multiple biological behaviours, including cell proliferation, cloning, migration, invasion and induction of apoptosis. We further discovered that QDN increased the pro-apoptotic BAX while inhibiting the anti-apoptotic Bcl2. QDN therapy led to a decline in adenosine triphosphate (ATP) and a rise in reactive oxygen species (ROS). Furthermore, QDN elevated the levels of the tumour suppressor p53 and the mitochondrial division factor DRP1 and FIS1, and decreased the mitochondrial fusion molecules MFN1, MFN2, and OPA1. The results were further verified by rescue experiments, the p53 inhibitor Pifithrin-α and the mitochondrial division inhibitor Mdivi1 partially inhibited QDN-induced apoptosis and mitochondrial dysfunction, whereas overexpression of p53 rather increased the efficacy of the therapy. Additionally, QDN inhibited tumour growth with acceptable safety invivo. In conclusion, QDN induced apoptosis via triggering p53/DRP1-mediated mitochondrial fission in NSCLC cells.

Ginsenoside compound K induces ferroptosis via the FOXO pathway in liver cancer cells

Liver cancer is a common malignant tumor worldwide, traditional Chinese medicine is one of the treatment measures for liver cancer because of its good anti-tumor effects and fewer toxic side effects. Ginsenoside CK (CK) is an active component of ginseng. This study explored the mechanism by which CK induced ferroptosis in liver cancer cells. We found that CK inhibited the proliferation of HepG2 and SK-Hep-1 cells, induced ferroptosis of cells. Ferrostatin-1, an ferroptosis inhibitor, was used to verify the role of CK in inducing ferroptosis of liver cancer cells. Network pharmacological analysis identified the FOXO pathway as a potential mechanism of CK, and western blot showed that CK inhibited p-FOXO1. In cells treated with the FOXO1 inhibitor AS1842856, further verify the involvement of the FOXO pathway in regulating CK-induced ferroptosis in HepG2 and SK-Hep-1 cells. A HepG2 cell–transplanted tumor model was established in nude mice, and CK inhibited the growth of transplanted tumors in nude mice, p-FOXO1 was decreased in tumor tissues, and SLC7A11 and GPX4 expressions were also down-regulated after CK treatment. These findings suggested that CK induces ferroptosis in liver cancer cells by inhibiting FOXO1 phosphorylation and activating the FOXO signaling pathway, thus playing an antitumor role.

Characterization and validation of fatty acid metabolism-related genes predicting prognosis, immune infiltration, and drug sensitivity in endometrial cancer.

Endometrial cancer is considered to be the second most common tumor of the female reproductive system, and patients diagnosed with advanced endometrial cancer have a poor prognosis. The influence of fatty acid metabolism in the prognosis of patients with endometrial cancer remains unclear. We constructed a prognostic risk model using transcriptome sequencing data of endometrial cancer and clinical information of patients from The Cancer Genome Atlas (TCGA) database via least absolute shrinkage and selection operator regression analysis. The tumor immune microenvironment was analyzed using the CIBERSORT algorithm, followed by functional analysis and immunotherapy efficacy prediction by gene set variation analysis. The role of model genes in regulating endometrial cancer in vitro was verified by CCK-8, colony formation, wound healing, and transabdominal invasion assays, and verified in vivo by subcutaneous tumor transplantation in nude mice. A prognostic model containing 14 genes was constructed and validated in 3 cohorts and clinical samples. The results showed differences in the infiltration of immune cells between the high-risk and low-risk groups, and that the high-risk group may respond better to immunotherapy. Experiments in vitro confirmed that knockdown of epoxide hydrolase 2 (EPHX2) and acyl-CoA oxidase like (ACOXL) had an inhibitory effect on EC cells, as did overexpression of hematopoietic prostaglandin D synthase (HPGDS). The same results were obtained in experiments in vivo. Prognostic models related to fatty acid metabolism can be used for the risk assessment of endometrial cancer patients. Experiments in vitro and in vivo confirmed that the key genes HPGDS, EPHX2, and ACOXL in the prognostic model may affect the development of endometrial cancer.

Gut Microbial Dysbiosis Differs in Two Distinct Cachectic Tumor-Bearing Models Consuming the Same Diet.

The impact of cancer cachexia on the colonic microbiota is poorly characterized. This study assessed the effect of two cachectic-producing tumor types on the gut microbiota to determine if a similar dysbiosis could be found. In addition, it was determined if a diet containing an immunonutrient-rich food (walnuts) known to promote the growth of probiotic bacteria in the colon could alter the dysbiosis and slow cachexia. Male Fisher 344 rats were randomly assigned to a semi-purified diet with or without walnuts. Then, within each diet group, rats were further assigned randomly to a treatment group: tumor-bearing ad libitum fed (TB), non-tumor-bearing ad libitum fed (NTB-AL), and non-tumor-bearing group pair-fed to the TB (NTB-PF). The TB group was implanted either with the Ward colon carcinoma or MCA-induced sarcoma, both transplantable tumor lines. Fecal samples were collected after the development of cachexia, and bacteria species were identified using 16S rRNA gene analysis. Both TB groups developed cachexia but had a differently altered gut microbiome. Beta diversity was unaffected by treatment (NTB-AL, TB, and NTB-PF) regardless of tumor type but was affected by diet. Also, diet consistently changed the relative abundance of several bacteria taxa, while treatment and tumor type did not. The control diet increased the abundance of A. Anaeroplasma, while the walnut diet increased the genus Ruminococcus. There were no common fecal bacterial changes characteristic of cachexia found. Diet consistently changed the gut microbiota, but these changes were insufficient to slow the progression of cachexia, suggesting cancer cachexia is more complex than a few gut microbiota shifts.

Abstract LB272: Sequential inhibition of PARP and BET as a rational therapeutic strategy for glioblastoma multiforme

Abstract Glioblastoma multiforme (GBM), characterized as one of the most aggressive brain cancers, presents significant treatment challenges due to its rapid growth, heterogeneity, and robust defensive mechanisms. Despite advancements in neuro-oncology, GBM's prognosis remains grim, with the median survival of approximately 15 months, underscoring the urgent need for innovative therapeutic strategies. Facing these challenges, PARP inhibitors (PARPi) hold substantial promise in treating GBM, evidenced by over 20 ongoing clinical trials. However, their application has been limited by side effects such as nausea, fatigue, and particularly anemia, as well as a narrow therapeutic spectrum focusing mainly on patients with homologous recombination deficiency (HRDness). Through unbiased transcriptomic and proteomic sequencing, and employing Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA), and Transcriptome-Proteome Correlation Analysis, we discovered that the BET inhibitor (BETi) Birabresib profoundly alters the processes of DNA replication and cell cycle progression in GBM cells, extending beyond the previously known impact of BET inhibition on homologous recombination repair. In vitro experiments using GBM cell lines and patient-derived primary GBM cells demonstrated that concurrent administration of PARPi and BETi can synergistically inhibit GBM. Intriguingly, we observed that DNA damage persists after the discontinuation of PARPi monotherapy. Leveraging these residual effects of PARPi, subsequent BETi administration elevated replication stress levels, leading to the inactivation of GBM cell cycle checkpoints, with efficacy comparable to concurrent treatment. The treatment-induced prolonged stalling of replication forks resulted in their collapse and the formation of double-ended double-strand breaks (DSBs). In GBM cells with elevated baseline replication stress, the sequential regimen exhibits comparable efficacy to concurrent treatment, while protecting normal glial cells with lower baseline replication stress from DNA toxicity and subsequent death. In vivo orthotopic transplantation tumor experiments in zebrafish and nude mice demonstrated consistent effects, indicating that sequential administration of PARPi followed by BETi maintained anti-tumor efficacy, similar to concurrent treatment, while reducing toxicity, as evident by the reduced impact on hemoglobin levels. Our findings provide a broader and deeper understanding of the synergistic interaction between BETi and PARPi than previously recognized. This study offers compelling preclinical evidence supporting the development of innovative drug administration strategies focusing on PARPi for GBM therapy. Citation Format: Xin Peng, Xin Huang, Shaolu Zhang, Naixin Zhang, Shengfan Huang, Yingying Wang, Zhenxing Zhong, Shan Zhu, Haiwang Gao, Zixiang Yu, Xiaotong Yan, Zhennan Tao, Yuxiang Dai, Zhe Zhang, Xi Chen, Feng Wang, Francois X. Claret, Ning Ji, Yuxu Zhong, Dexin Kong. Sequential inhibition of PARP and BET as a rational therapeutic strategy for glioblastoma multiforme [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB272.

Abstract LB362: Systematic development and characterization of orthotopic animal tumor models: A proactive approach to mimic patients' tumor microenvironments for drug discovery

Abstract Preclinical in vivo tumor models are crucial in translational research and the pharmaceutical industry, particularly for evaluating novel anti-cancer agents. While animal tumor models are widely used in both drug development and academic research, the majority of investigations have relied on subcutaneous (SC) transplantable tumor models. These models often fail to consider the orthotopic organ origin or the unique microenvironmental differences, leading to significant limitations. Despite many publications highlighting the advantages of orthotopic tumor models (ORTH) over SC models, there is a lack of systematic analysis and comparative characterization of these formats. In this study, we have systematically developed a comprehensive ORTH tumor model platform comprising over 80 orthotopic tumor models and covering more than 25 tumor types. ORTH tumor models have been enhanced for non-invasive monitoring and increased sensitivity of tumor growth and metastasis detection through labeling with multimodality imaging markers such as GFP, RFP, and bioluminescence or imaging with micro-CT or ultrasound. We optimized and streamlined technical procedures, throughput, and reproducibility of ORTH model development, facilitating the use of these models to assess anticancer agents in a large-scale format. To mimic the clinical situation, our characterization of these models includes growth profiles, metastatic features, and survival status. Additionally, ORTH models were compared with SC models regarding the efficacy of standard-of-care (SOC) drugs through side-by-side comparison studies. As expected, inconsistent responses to SOC therapeutics were observed in some models when comparing ORTH versus SC tumors. For models yielding inconsistent results, molecular analysis and model selection recommendations will be discussed. To date, this is the first study describing the generation of a considerably large orthotopic tumor model collection and conducting a comprehensive side-by-side characterization of ORTH and SC models. This proactive approach aims to improve the mimicry of patients' tumor microenvironments and enhance the clinical relevance and potentially increase the efficiency of translational research processes. Citation Format: WenQing Yang, Xusheng Yuan, Guangliang Yang, Xiaojun Tong, Weiqun Ding, Qiuxia Zhang, Feng Lu, Zhijian Yang. Systematic development and characterization of orthotopic animal tumor models: A proactive approach to mimic patients' tumor microenvironments for drug discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB362.

Knockdown of PGBD5 inhibits the malignant progression of glioma through upregulation of the PPAR pathway.

Glioma is the most common type of primary intracranial malignant tumor, and because of its high invasiveness and recurrence, its prognosis remains poor. The present study investigated the biological function of piggyBac transportable element derived 5 (PGBD5) in glioma. Glioma and para-cancerous tissues were obtained from five patients. Reverse transcription-quantitative PCR and western blotting were used to detect the expression levels of PGBD5. Transwell assay and flow cytometry were used to evaluate cell migration, invasion, apoptosis and cell cycle distribution. In addition, a nude mouse tumor transplantation model was established to study the downstream pathways of PGBD5 and the molecular mechanism was analyzed using transcriptome sequencing. The mRNA and protein expression levels of PGBD5 were increased in glioma tissues and cells. Notably, knockdown of PGBD5 in vitro could inhibit the migration and invasion of glioma cells. In addition, the knockdown of PGBD5 expression promoted apoptosis and caused cell cycle arrest in the G2/M phase, thus inhibiting cell proliferation. Furthermore, in vivo experiments revealed that knockdown of PGBD5 expression could inhibit Ki67 expression and slow tumor growth. Changes in PGBD5 expression were also shown to be closely related to the peroxisome proliferator-activated receptor (PPAR) signaling pathway. In conclusion, interference with PGBD5 could inhibit the malignant progression of glioma through the PPAR pathway, suggesting that PGBD5 may be a potential molecular target of glioma.

Indications and outcomes of liver transplantation for liver tumors in the United States

BackgroundWhile hepatocellular carcinoma (HCC) remains the leading cause of liver transplant (LT) for liver tumors, indications have broadened over the years. Data regarding patient characteristics and outcomes of LT for liver tumors are limited. MethodsFrom Jan-2002 to March-2022, 14,406 LT recipients for various liver tumors were identified in United Network for Organ Sharing database. Overall post-transplant survival analysis was performed with Kaplan-Meier method and multivariable Cox proportional-hazards model. ResultsDuring the study period, indications for LT for various hepatic tumors were HCC (88.5 %), benign tumors (5.1 %), cholangiocarcinoma (3.9 %), angiosarcoma (0.7 %), bile duct cancer (0.7 %), secondary tumors (0.5 %) and others (0.7 %). Compared to non-HCC, LT recipients for HCC were older (median age 61 vs 54 years, P < 0.001), more often male (77% vs 48 %, P < 0.001), more often Hispanic (16% vs 8.0 %), had higher BMI (28.2 vs 25.3, P < 0.001) and higher prevalence of Hepatitis C (53% vs 3.9 %, P < 0.001). Donor characteristics across various groups were similar. One-year survival in LT recipients of HCC was higher (HCC: 91.7% vs. non-HCC: 90.3 %) with adjusted Hazard Ratio (aHR) of 0.87; 95 % CI 0.77–0.99, P = 0.033 in a multivariable Cox regression analysis. Compared to HCC, survival outcomes were worse in cholangiocarcinoma (aHR 1.70; 95 %CI 1.43–2.01, P < 0.001), bile duct cancer (aHR 3.03; 95 %CI 2.12–4.33, P < 0.001), secondary tumors including colon cancer and neuroendocrine tumors (aHR 1.88; 95 % CI 1.24–2.85, P = 0.003), with best survival in patients with benign tumors (aHR 0.57; 95 %CI 0.46–0.70, P < 0.001). ConclusionsLT is performed for various liver tumors with variable outcomes among these primary indications.

The trogocytosis of neutrophils on initial transplanted tumor in mice

The role of neutrophils in tumor initiation stage is rarely reported because of the lack of suitable models. We found that neutrophils recruited in early tumor nodules induced by subcutaneous inoculation of B16 melanoma cells were able to attack tumor cells by trogocytosis. The anti-tumor immunotherapy like peritoneal injection with TLR9 agonist CpG oligodeoxynucleotide combined with transforming growth factor β2 inhibitor TIO3 could increase the trogocytic neutrophils in the nodules, as well as CD8+ Tcells, natural killer (NK) cells, and their interferon-γ production. Local use of Cxcl2 small interfering RNA significantly reduced the number of neutrophils and trogocytic neutrophils in tumor nodules, as well as CD8+ T and NK cells, and also enlarged the nodules. These results suggest that neutrophils recruited early to the inoculation site of tumor cells are conducive to the establishment of anti-tumor immune microenvironment. Our findings provide a useful model system for studying the effect of neutrophils on tumors and anti-tumor immunotherapy.

MELK aggravates lung adenocarcinoma by regulating EZH2 ubiquitination and H3K27me3 histone methylation of LATS2.

We tried to elucidate the possible roles of maternal embryonic leucine pull chain kinase (MELK) in lung adenocarcinoma (LUAD) growth and metastasis. Differentially expressed genes in LUAD samples were analysed by the GEPIA database. Clinical tissue samples and cells were collected for MELK, EZH2 and LATS2 expression determination. Co-IP assay was used to verify the interaction between EZH2 and MELK; CHX tracking assay and ubiquitination assay detected the degradation of MELK on EZH2 ubiquitination. ChIP assay detected the enrichment of EZH2 and H3K27me3 on the LATS2 promoter region. LUAD cells were selected for invitro validation, and the tumorigenic ability of LUAD cells was also observed in a transplantation tumour model of LUAD nude mice. MELK and EZH2 were highly expressed in LUAD samples, while LATS2 was lowly expressed. MELK interacted with EZH2 to inhibit its ubiquitination degradation; EZH2 elevated H3K27me3 modification in the LATS2 promoter to lower LATS2 expression. Silencing MELK or EZH2 or overexpressing LATS2 restrained LUAD cell proliferation and invasion, and facilitated their apoptosis. Silencing MELK or EZH2 or overexpressing LATS2 suppressed tumour formation in nude mice. This study demonstrated that MELK aggravated LUAD by upregulating EZH2 and downregulating LATS2.

Oxaliplatin-Loaded Mil-100(Fe) for Chemotherapy-Ferroptosis Combined Therapy for Gastric Cancer.

Oxaliplatin (Oxa) is a commonly used chemotherapy drug in the treatment of gastric cancer, but its toxic side effects and drug resistance after long-term use have seriously limited its efficacy. Loading chemotherapy drugs with nanomaterials and delivering them to the tumor site are common ways to overcome the above problems. However, nanomaterials as carriers do not have therapeutic functions on their own, and the effect of single chemotherapy is relatively limited, so there is still room for progress in related research. Herein, we construct Oxa@Mil-100(Fe) nanocomposites by loading Oxa with a metal-organic framework (MOF) Mil-100(Fe) with high biocompatibility and a large specific surface area. The pore structure of Mil-100(Fe) is conducive to a large amount of Oxa loading with a drug-loading rate of up to 27.2%. Oxa@Mil-100(Fe) is responsive to the tumor microenvironment (TME) and can release Oxa and Fe3+ under external stimulation. On the one hand, Oxa can inhibit the synthesis of DNA and induce the apoptosis of gastric cancer cells. On the other hand, Fe3+ can clear overexpressed glutathione (GSH) in TME and be reduced to Fe2+, inhibiting the activity of glutathione peroxidase 4 (GPX4), leading to the accumulation of intracellular lipid peroxides (LPO), and at the same time releasing a large number of reactive oxygen species (ROS) through the Fenton reaction, inducing ferroptosis in gastric cancer cells. With the combination of apoptosis and ferroptosis, Oxa@Mil-100(Fe) shows a good therapeutic effect, and the killing effect on gastric cancer cells is obvious. In a nude mouse model of subcutaneous tumor transplantation, Oxa@Mil-100(Fe) shows a significant inhibitory effect on tumor growth, with an inhibition rate of nearly 60%. In addition to its excellent antitumor activity, Oxa@Mil-100(Fe) has no obvious toxic or side effects. This study provides a new idea and method for the combined treatment of gastric cancer.

METTL3 orchestrates glycolysis by stabilizing the c-Myc/WDR5 complex in triple-negative breast cancer

BackgroundThe carcinogenic transcription factor c-Myc is the most aggressive oncogene, which drive malignant transformation and dissemination of triple-negative breast cancer (TNBC). Recruitment of many cofactors, especially WDR5, a protein that nucleates H3K4me chromatin modifying complexes, play a pivotal role in regulating c-Myc-dependent gene transcription, a critical process for c-Myc signaling to function in a variety of biological and pathological contexts. For this reason, interrupting the interaction between c-Myc and the transcription cofactor WDR5 may become the most promising new strategy for treating c-Myc driven TNBC. MethodsImmunoprecipitation and mass spectrometry (IP-MS) is used to screen proteins that bind c-Myc/WDR5 interactions. The interaction of METTL3 with c-Myc/WDR5 in breast cancer tissues and TNBC cells was detected by Co-IP and immunofluorescence. Subsequently, we further analyzed the influence of METTL3 expression on c-Myc/WDR5 protein expression and its interaction stability by Western blot and Co-IP. The correlation between METTL3 and c-Myc pathway was analyzed by ChIP-seq sequencing and METTL3 knockdown transcriptome data. The effect of METTL3 expression on c-Myc transcriptional activity was detected by ChIP-qPCR and Dual Luciferase Reporter. At the same time, the overexpression vector METTL3-MUT (m6A) was constructed, which mutated the methyltransferase active site (Aa395–398, DPPW/APPA), and further explored whether the interaction between METTL3 and c-Myc/WDR5 was independent of methyltransferase activity. In addition, we also detected the changes of METTL3 expression on TNBC's sensitivity to small molecule inhibitors such as JQ1 and OICR9429 by CCK8, Transwell and clonal formation assays. Finally, we further verified our conclusions in spontaneous tumor formation mouse MMTV-PyMT and nude mouse orthotopic transplantation tumor models. ResultsMETTL3 was found to bind mainly to c-Myc/WDR5 protein in the nucleus. It enhances the stability of c-Myc/WDR5 interaction through its methyltransferase independent mechanism, thereby enhancing the transcriptional activity of c-Myc on downstream glucose metabolism genes. Notably, the study also confirmed that METTL3 can directly participate in the transcription of glucose metabolism genes as a transcription factor, and knockdown METTL3 enhances the drug sensitivity of breast cancer cells to small molecule inhibitors JQ1 and OICR9429. The study was further confirmed by spontaneous tumor formation mouse MMTV-PyMT and nude mouse orthotopic transplantation tumor models. ConclusionMETTL3 binds to the c-Myc/WDR5 protein complex and promotes glycolysis, which plays a powerful role in promoting TNBC progression. Our findings further broaden our understanding of the role and mechanism of action of METTL3, and may open up new therapeutic avenues for effective treatment of TNBC with high c-Myc expression.

Abstract 1416: Resolvins enhance immunotherapy to induce Fanconi anemia tumor regression via inflammation resolution

Abstract Fanconi anemia (FA) is a disorder characterized by early-onset solid tumors unresponsive to chemotherapy and radiation. Unresolved inflammation is a hallmark of FA, the mechanisms underlying the initiation and resolution of inflammation in FA are poorly characterized. We hypothesized that FA tumor progression is controlled by dysregulated resolution metabolomes and a systemic pro-inflammatory eicosanoid storm of inflammation-initiating mediators. Using a novel transplantable murine FA tumor model, we show that Fancc-/- HNSCC (head and neck squamous cell carcinoma) progression disrupts the resolution of inflammation via an imbalance between specialized pro-resolving lipid mediators (SPMs) and eicosanoids. Fancc-/- tumor-bearing mice exhibited an increase in eicosanoids, including leukotriene B4 (LTB4) and thromboxane B2 (TXB2) in the spleen and a 113% increase in prostaglandin E metabolite (PGEM), a marker of PGE2 production, in the plasma compared to non-tumor-bearing (NT) mice. Fancc-/- tumor-bearing mice exhibited a loss in the SPM/LTB4 ratio including RvD1/LTB4, RvD2/LTB4, and MaR1/LTB4, compared to NT mice. Given the activity of immune checkpoint blockade in mismatch repair deficient tumors including head and neck cancers, immunotherapy may be relevant to FA-induced cancers. Importantly, the number of absolute T cells and CD4+ T cell function is preserved in individuals with FA. We combined stimulation of the resolution of inflammation (i.e., treatment with RvDs) with immunotherapy in a new transplantable murine FA tumor model. While treatment with RvD4, RvD5, or anti-PD1 immunotherapy alone delayed tumor growth compared to control at treatment day 20, the tumors did escape monotherapy by treatment day 30. Remarkably, RvD4 or RvD5 combined with anti-PD1 immunotherapy induced sustained Fancc-/- tumor regression. Moreover, RvD4 and/or anti-PD1 immunotherapy inhibited orthotopic Fancc-/- tumor growth compared to control. Resolvins and immune checkpoint blockade synergistically induced Fancc-/- tumor regression via macrophage phagocytosis of apoptotic debris, counter-regulation of pro-angiogenic cytokines, and inhibition of angiogenesis. Triggering Receptor Expressed on Myeloid cells-2 (TREM2)-antagonism combined with resolvins and immunotherapy restored SPM/eicosanoid ratios in Fancc−/- tumor-bearing mice to pre-cancer levels. SPMs and eicosanoids provide potential early biomarkers and biological targets in FA-induced cancer progression. Stimulating the resolution of inflammation via pro-resolution lipid mediators to enhance immunotherapy is a novel host-centric therapeutic approach to prevent FA-induced cancer progression via debris clearance and cytokine suppression. These results provide evidence for targeting the resolution of inflammation via resolvins to enhance immunotherapy to prevent and/or reverse FA-induced cancer progression. Citation Format: Katherine Quinlivan, Haixia Yang, Diane R. Bielenberg, Susanne I. Wells, Charles N. Serhan, Dipak Panigrahy. Resolvins enhance immunotherapy to induce Fanconi anemia tumor regression via inflammation resolution [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 1416.

Abstract 6715: CLDN6: Biological insight into therapeutic potency of SAIL66, a next generation of T-cell engager targeting CLDN6

Abstract Background: Because of high recurrence rate, ovarian cancer continues to demand new treatments. Recently, we have developed a next-generation T-cell engager SAIL66, which is a tri-specific monoclonal antibody designed to bind to CLDN6 on cancer cells with one Fab arm and to both CD3 and CD137 with the other Fab arm. By boosting T cell activation through both CD3 and CD137 binding, SAIL66 shows potent anti tumor efficacy against CLDN6-positive cancers and are currently being evaluated in patients with CLDN6-positive solid cancers including ovarian cancer (NCT05735366). CLDN6 is upregulated in many solid tumors but shows minimal or no expression in healthy adult tissues. Due to its cancer specific expression profile, CLDN6 has been utilized as a target for cancer immune therapies. Here, we demonstrate that CLDN6 is an attractive therapeutic target from its biological perspective in ovarian cancer. Methods and Results: In a HuNOG tumor-bearing mouse model transplanted with CLDN6-positive ovarian cancer cells (OV90, OVCAR3), SAIL66 showed potent antitumor activity as a single agent. Surprisingly, CLDN6 expression in transplanted tumors was significantly lower compared to in vitro cultured cells, suggesting that CLDN6 expression is highly variable. In vitro, CLDN6 expression reversibly fluctuated depending on cell density, and its expression was consistent with the expression of epithelial-mesenchymal transition (EMT) and stemness-related genes. Furthermore, FACS and qPCR revealed that chemotherapeutic agents increased CLDN6-positive cells, and this fluctuation was accompanied by the expression of EMT and stemness-related genes. Based on this biology, we tested the combination effect of SAIL66 and chemotherapies in a non-clinical tumor-bearing mouse model. As a result, significant tumor regression was observed in mice treated with SAIL66 in combination with carboplatin. Conclusion and Discussion: Ovarian cancer is characterized by significant tumor heterogeneity. The presence of cancer stem/stem-like cells or EMT has been proposed to elucidate the underlying mechanisms of the heterogeneity. Our study potentially could offer valuable insights into the biology of CLDN6-positive cells and the causes of ovarian cancer heterogeneity. Furthermore, it could help in patient selection, the development of combination strategies, and future clinical validation of SAIL66. Citation Format: Naoki Kimura, Kenji Taniguchi, Takayuki Kamikawa, Moe Yoshimoto, Shinya Ishii, Masaru Muraoka, Mei Shimada, Mika Kamata-Sakurai, Takehisa Kitazawa, Tomoyuki Igawa. CLDN6: Biological insight into therapeutic potency of SAIL66, a next generation of T-cell engager targeting CLDN6 [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 6715.

Fatostatin promotes anti-tumor immunity by reducing SREBP2 mediated cholesterol metabolism in tumor-infiltrating T lymphocytes

Aberrant lipid metabolism impacts intratumoral T cell-mediated immune response and tumor growth. Fatostatin functions as an inhibitor of sterol regulatory element binding protein (SREBP) activation. However, the complex effects of fatostatin on cholesterol metabolism in the tumor microenvironment (TME) and its influence on T cell anti-tumor immunity remain unclear. In this study, fatostatin effectively suppressed B16 melanoma, MC38 colon cancer, and Lewis lung cancer (LLC) transplanted tumor growth in immunocompetent mice by reducing SREBPs-mediated lipid metabolism, especially cholesterol levels. Mechanistically, fatostatin decreased intracellular cholesterol accumulation and inhibited X-box binding protein 1 (XBP1)-mediated endoplasmic reticulum (ER) stress, reducing Treg cells and alleviating CD8+ T cell exhaustion in the TME, exerting anti-tumor activity. Nevertheless， this effect was impaired in immunodeficient nude mice, suggesting fatostatin's anti-tumor efficacy in transplanted tumors partly relies on T cell-mediated anti-tumor immunity. Our study highlights SREBP2-mediated cholesterol metabolism as a potential strategy for anti-tumor immunotherapy, and confirms fatostatin's promise in tumor immunotherapy.

Abstract 5002: Next-generation mRNA-LNP vaccine prototype achieves tumor clearance in a GBM mouse model

Abstract Glioblastoma (GBM) is the most prevalent and aggressive primary brain tumor type with an abysmal prognosis, featuring an immunologically dampened tumor microenvironment and limited neoantigen production. Novel therapeutic strategies are urgently needed. A well-characterized GBM-associated mutation that can elicit an anti-tumor immune response is EGFRvIII mutation. The cancer-driver mutation is detected in approximately 30% of patients at the time of diagnosis and plays a pivotal role in the emergence of GBM. EGFRvIII is an in-frame epidermal growth factor receptor (EGFR) deletion generating a constitutively active oncogenic protein. Its highly immunogenic nature represents an ideal focal point for cutting-edge mRNA-LNP candidate therapeutics. To evaluate proprietary lipid nanoparticle (LNP) compositions for their capacity to induce anti-GBM immunity, we developed a murine transplantable GBM tumor model by neonatal electroporation. The somatically engineered glioblastomas harbor two targeted CRISPR knockouts and stably overexpress EGFRvIII to yield transplantable cell lines for orthotopic tumor initiation. One week after intracranial tumor cell implantation of 6-8 week-old female mice (day 0; n=10), half the animals were administered either buffer (control cohort) or our novel anti-EGFRvIII mRNA-LNP vaccine (experimental cohort). The regimen involved four intramuscular injections before monitoring tumor progression by MRI on day 30. The imaging revealed a high tumor burden in all control group animals, compared to no detectable tumor cells in vaccine-protected mice. All control group animals were humanely euthanized by day 38 due to symptoms associated with the growing brain tumor mass. The asymptomatic experimental animals received a fifth anti-EGFRvIII vaccination before MRI-based examinations on day 43 and day 78 confirmed that no tumor cells could be detected in vaccine-protected mice. The results highlight the potency and potential of our proprietary anti-EGFRvIII mRNA-LNP vaccine as a novel anticancer therapeutic. In addition, the established tumor model represents a valuable tool to test future mRNA-LNP designs. Outstanding cellular and molecular investigations will reveal vaccine-mediated mechanistic insights, allowing for the co-advancement of the tumor model and next-generation multi-target mRNA-LNP vaccine candidates. Citation Format: Robert Nechanitzky, Shannon Snelling Snelling, Kristofor Ellestad, Xueqing Lun, Kirstin Olsen, Yu Wu, Yury Karpov, Jun Liu, Matthew Gold, Haritha Menon, Rajesh Krishnan, Robert Georgantas, Pamela S. Ohashi, Douglas J. Mahoney, Jennifer A. Chan, Natalia Martin-Orozco. Next-generation mRNA-LNP vaccine prototype achieves tumor clearance in a GBM mouse model [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 5002.

Abstract 6651: Compromised TGFβ signaling and DNA repair primes immune poor tumors response to immune checkpoint blockade by activating NK cells

Abstract We investigated the interplay between transforming growth factor beta (TGFβ) regulation of immunosuppressive signaling and immunogenic DNA repair. Loss of TGFβ signaling by cancer cells is accompanied by increased use of error-prone repair. We described a transcriptomic score, βAlt, that reports the TGFβ/DNA repair functional relationship. Pan-cancer analysis showed that high βAlt cancers (i.e., low TGFβ and high error-prone DNA repair) are sensitive to chemoradiation and have a greater fraction of genome altered compared to low βAlt cancers. Defective mismatch repair is associated with T cell infiltration and response to immune checkpoint blockade (ICB), hence we investigated the immune context of bAlt. Unsupervised clustering of RNAseq profiles 12 independent immunocompetent mouse tumor derived transplant (mTDT) tumors based on βAlt score indicated that high βAlt was associated with immune poor phenotype and lack of type I interferon signatures. A similar relationship was evident in the bladder, breast, and lung TCGA data. A high βAlt, immune poor mTDT in which T cells were only 20% of 10% CD45 were treated with monotherapy consisting of single fraction 10 Gy radiation, anti-PD-L1 or TGFβ inhibition, dual or triple treatment. Only monotherapy or combinations with radiation significantly increased survival. However, these ICB resistant tumors responded to triple treatment. Response was accompanied by increased tumor infiltrating CD45+ cells (P=0.02), circulating CD8 T cells (P&amp;lt;0.001) and natural killer (NK) cells (P&amp;lt;0.001). As NK cells tripled and TGFβ broadly impairs NK cell effector function, we depleted NK cells to test whether they were required for the response to triple treatment. NK depletion completely abrogated response (P&amp;lt;0.00001) indicating NK cells can provoke an ICB response in high βAlt immune poor tumors. Both mouse tumors and human cancers show that loss of TGFβ signaling resulting in error-prone DNA damage response is strongly associated with immune poor tumors and suggests that TGFβ inhibition can override NK cell dysfunction to create vulnerability to ICB. Citation Format: Jade T. Moore, Jim Gkantalis, Ines Guix, Mary Helen Barcellos-Hoff. Compromised TGFβ signaling and DNA repair primes immune poor tumors response to immune checkpoint blockade by activating NK cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6651.