Tumor Cell Types Research Articles

Mechanisms involved in the anti-tumor effects of Toosendanin in glioma cells

BackgroundToosendanin (TSN) is a triterpenoid compound mainly used as an ascaris repellant. Recent studies have shown that it possesses antitumor effects in many types of tumor cells. However, the effects of TSN on glioma cells have rarely been reported.MethodsDifferent assays were performed to investigate the effects of TSN on the different glioma cell lines including U87MG and LN18. The assays included colony formation, wound healing, and transwell assays. Furthermore, Hoechst 33342 staining, flow cytometry, and western blotting analysis were performed to investigate the apoptotic activities of TSN. Finally, the results were confirmed using a xenograft tumor model that comprised of nude mice.ResultsIn vitro, the CCK-8 and colony formation assays showed that TSN effectively inhibited glioma cell proliferation. Moreover, the inhibitory effects on glioma cell migration and invasion were demonstrated through the wound healing and transwell assays, respectively. Hoechst 33342 staining, flow cytometry, and western blotting assays demonstrated the significant effect of TSN in the apoptosis induction of glioma cells. Furthermore, the anti-glioma effect of TSN was exerted through the inhibition of the PI3K/Akt/mTOR signaling pathways as demonstrated by western blotting analysis. In addition, the effects of TSN on glioma cell viability, apoptosis, cell cycle arrest, migration, and invasion were reversed by 740Y-P, a PI3K activator. Finally, the mouse xenograft model confirmed the suppressive effect of TSN on tumor growth in vivo.ConclusionOur results suggest that TSN is a promising chemotherapeutic drug for patients with glioma.

Pan-Cancer Analysis of PIMREG as a Biomarker for the Prognostic and Immunological Role.

Phosphatidylinositol binding clathrin assembly protein interacting mitotic regulator (PIMREG) localizes to the nucleus and can significantly elevate the nuclear localization of clathrin assembly lymphomedullary leukocythemia gene. Although there is some evidence to support an important action for PIMREG in the occurrence and development of certain cancers, currently no pan-cancer analysis of PIMREG is available. Therefore, we intended to estimate the prognostic predictive value of PIMREG and to explore its potential immune function in 33 cancer types. By using a series of bioinformatics approaches, we extracted and analyzed datasets from Oncomine, The Cancer Genome Atlas, Cancer Cell Lineage Encyclopedia (CCLE) and the Human Protein Atlas (HPA), to explore the underlying carcinogenesis of PIMREG, including relevance of PIMREG to prognosis, microsatellite instability (MSI), tumor mutation burden (TMB), tumor microenvironment (TME) and infiltration of immune cells in various types of cancer. Our findings indicate that PIMREG is highly expressed in at least 24 types of cancer, and is negatively correlated with prognosis in major cancer types. In addition, PIMREG expression was correlated with TMB in 24 cancers and with MSI in 10 cancers. We revealed that PIMREG is co-expressed with genes encoding major histocompatibility complex, immune activation, immune suppression, chemokine and chemokine receptors. We also found that the different roles of PIMREG in the infiltration of different immune cell types in different tumors. PIMREG can potentially influence the etiology or pathogenesis of cancer by acting on immune-related pathways, chemokine signaling pathway, regulation of autophagy, RIG-I like receptor signaling pathway, antigen processing and presentation, FC epsilon RI pathway, complement and coagulation cascades, T cell receptor pathway, NK cell mediated cytotoxicity and other immune-related pathways. Our study suggests that PIMREG can be applied as a prognostic marker in a variety of malignancies because of its role in tumorigenesis and immune infiltration.

Evaluation of antimicrobial and antiproliferative activities of Actinobacteria isolated from the saline lagoons of northwestern Peru.

Extreme environments Morrope and Bayovar Salt lagoons, several ecosystems and microhabitats remain unexplored, and little is known about the diversity of Actinobacteria. We suggest that the endemic bacteria present in this extreme environment is a source of active molecules with anticancer, antimicrobial, and antiparasitic properties. Using phenotypic and genotypic characterization techniques, including 16S rRNA sequencing, we identified these bacteria as members of the genera Streptomyces, Pseudonocardia, Staphylococcus, Bacillus, and Pseudomonas. Actinobacteria strains were found predominantly. Phylogenetic analysis revealed 13 Actinobacteria clusters of Streptomyces, the main genus. Three Streptomycetes, strains MW562814, MW562805, and MW562807 showed antiproliferative activities against three tumor cell lines: U251 glioma, MCF7 breast, and NCI-H460 lung (non-small cell type); and antibacterial activity against Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 10536, and the multidrug resistant Acinetobacter baumannii AC-972. The antiproliferative activities (measured as total growth inhibition [TGI]) of Streptomyces sp. MW562807 were 0.57 μg/mL, for 0.61 μg/mL, and 0.80 μg/mL for glioma, lung non-small cell type, and breast cancer cell lines, respectively; the methanolic fraction of the crude extract showed a better antiproliferative activity and could inhibit the growth of (U251 (TGI = 38.3 μg/mL), OVCAR-03 (TGI = 62.1 μg/mL), and K562 (TGI = 81.5 μg/mL)) of nine tumor cells types and one nontumor cell type. Extreme enviroments, such as the Morrope and Bayovar Salt saloons are promising sources of new bacteria, whose compounds may be useful for treating various infectious diseases or even some types of cancer.

8-Formylophiopogonanone B induces ROS-mediated apoptosis in nasopharyngeal carcinoma CNE-1 cells.

Cancer is one of the leading causes of death in the world. It is very important to find drugs with high efficiency, low toxicity, and low side effects for the treatment of cancer. Flavonoids and their derivatives with broad biological functions have been recognized as anti-tumor chemicals. 8-Formylophiopogonanone B (8-FOB), a naturally existed homoisoflavonoids with rarely known biological functions, needs pharmacological evaluation. In order to explore the possible anti-tumor action of 8-FOB, we used six types of tumor cells to evaluate in vitro effects of this agent on cell viability and tested the effects on clone formation ability, scratching wound-healing, and apoptosis. In an attempt to elucidate the mechanism of pharmacological action, we examined 8-FOB-induced intracellular oxidative stress and -disrupted mitochondrial function. Results suggested that 8-FOB could suppress tumor cell viability, inhibit cell migration and invasion, induce apoptosis, and elicit intracellular ROS production. Among these six types of tumor cells, the nasopharyngeal carcinoma CNE-1 cells were the most sensitive cancer cells to 8-FOB treatment. Intracellular ROS production played a pivotal role in the anti-tumor action of 8-FOB. Our present study is the first to document that 8-FOB has anti-tumor activity in vitro and increases intracellular ROS production, which might be responsible for its anti-tumor action. The anti-tumor pharmacological effect of 8-FOB is worthy of further investigation.

DFF40-iRGD, a novel chimeric protein with efficient cytotoxic and apoptotic effects against triple-negative breast cancer cells.

DNA fragmenting factor (DFF40), an endonuclease inducing irreversible apoptosis protein, is down-regulated in many types of tumor cells. iRGD is a tumor-penetrating peptide with high affinity to cancer cells overexpressing αVβ3 receptor. The aim of this study was to produce the recombinant DFF40-iRGD protein as a new molecule to selectively induce cytotoxicity in cancer cells and evaluate its biological effects. The three-dimensional structure of DFF40-iRGD was predicted using Modeller software and its interaction with αVβ3 receptor was evaluated by HADDOCK web-server. Recombinant DFF40 and DFF40-iRGD proteins were produced using intein fusion system in Escherichia coli BL21 (DE3). To improve the soluble expression, the inducer concentration, temperature and incubation time were optimized. After purification of DFF40 and DFF40-iRGD using chitin column, the cytotoxic and apoptotic effects of the proteins against MDA-MB-231 (αVβ3 positive) and MCF-7 (αVβ3 negative) cell lines were evaluated using cell viability assay and flow cytometric analysis. The results of molecular docking indicated the proper interaction of DFF40-iRGD with the integrin receptor comparable to iRGD. The optimum conditions of soluble expression of proteins were the induction by 0.5mM and 0.1mM of IPTG for DFF40 and DFF40-iRGD, respectively, at 7°C for 24h. After 48h of incubation, DFF40-iRGD exhibited significantly higher cytotoxic effect against MDA-MB-231 cells than MCF-7 cells as IC50 values of 19.25 and 41nM were found for MDA-MB-231 and MCF-7 cells, respectively. However, DFF40 cytotoxicity was not significantly different in two cell lines. Furthermore, Flow cytometry results showed that the fusion protein can induce remarkably apoptotic cell death in cancer cells. In this study, DFF40-iRGD protein was produced in soluble form and its inhibitory effects on cancer cell survival and induction of apoptosis were established; therefore, it has the potential to be used as a drug candidate for targeted treatment of breast cancer, especially Triple Negative Breast Cancer Cells.

Basaloid squamous cell carcinoma.

Basaloid squamous cell carcinoma (BSCC) is a rare variant of squamous cell carcinoma characterized by a conglomerate of clinically aggressive course and disparate histopathological features. It is frequently seen in upper aerodigestive tract area. Histopathologically, it is biphasic and composed of two types of tumor cells, namely basaloid and squamous cells. Tumor markers, namely, BerEp4, epithelial membrane antigen and p53 are used in this case to differentiate from similar tumors which impersonate BSCC histologically but differ prognostically. We report a case of BSCC in a 48-year-old female patient, involving the lateral border of the tongue with an exhaustive picture of its histological and immunohistochemical appearance.

Classification of unlabeled cells using lensless digital holographic images and deep neural networks.

Image-based cell analytic methodologies offer a relatively simple and economical way to analyze and understand cell heterogeneities and developments. Owing to developments in high-resolution image sensors and high-performance computation processors, the emerging lensless digital holography technique enables a simple and cost-effective approach to obtain label-free cell images with a large field of view and microscopic spatial resolution. The holograms of three types of cells, including MCF-10A, EC-109, and MDA-MB-231 cells, were recorded using a lensless digital holography system composed of a laser diode, a sample stage, an image sensor, and a laptop computer. The amplitude images were reconstructed using the angular spectrum method, and the sample to sensor distance was determined using the autofocusing criteria based on the sparsity of image edges and corner points. Four convolutional neural networks (CNNs) were used to classify the cell types based on the recovered holographic images. Classification of two cell types and three cell types achieved an accuracy of higher than 91% by all the networks used. The ResNet and the DenseNet models had similar classification accuracy of 95% or greater, outperforming the GoogLeNet and the CNN-5 models. These experiments demonstrated that the CNNs were effective at classifying two or three types of tumor cells. The lensless holography combined with machine learning holds great promise in the application of stainless cell imaging and classification, such as in cancer diagnosis and cancer biology research, where distinguishing normal cells from cancer cells and recognizing different cancer cell types will be greatly beneficial.

987P A new therapeutic antibody against CD73 that ameliorates the tumor microenvironment and improves the efficacy of cancer immunotherapy

CD73 is expressed on certain types of leukocytes and tumor cells and is known as a poor prognostic factor in patients. CD73 catalyzes conversion of extracellular adenosine monophosphate (AMP) to adenosine (Ado) which accumulates in the tumor microenvironment (TME). Ado suppresses immune activation through Ado receptors, allowing tumors to escape from the host immune system. Suppressing CD73 activity provokes T-cell activation and reverses immune suppression exerted by Ado. Thus, the inhibition of CD73 by anti-CD73 antibodies may provide potent cancer immunotherapy options.

Pathophysiological Roles of Histamine Receptors in Cancer Progression: Implications and Perspectives as Potential Molecular Targets.

High levels of histamine and histamine receptors (HRs), including H1R~H4R, are found in many different types of tumor cells and cells in the tumor microenvironment, suggesting their involvement in tumor progression. This review summarizes the latest evidence demonstrating the pathophysiological roles of histamine and its cognate receptors in cancer biology. We also discuss the novel therapeutic approaches of selective HR ligands and their potential prognostic values in cancer treatment. Briefly, histamine is highly implicated in cancer development, growth, and metastasis through interactions with distinct HRs. It also regulates the infiltration of immune cells into the tumor sites, exerting an immunomodulatory function. Moreover, the effects of various HR ligands, including H1R antagonists, H2R antagonists, and H4R agonists, on tumor progression in many different cancer types are described. Interestingly, the expression levels of HR subtypes may serve as prognostic biomarkers in several cancers. Taken together, HRs are promising targets for cancer treatment, and HR ligands may offer novel therapeutic potential, alone or in combination with conventional therapy. However, due to the complexity of the pathophysiological roles of histamine and HRs in cancer biology, further studies are warranted before HR ligands can be introduced into clinical settings.

Sesamin promotes apoptosis and pyroptosis via autophagy to enhance antitumour effects on murine T-cell lymphoma

Sesamin is a lignan compound in plants that has various pharmacological effects, including reducing diabetes-associated injuries, regulating fatty acid and cholesterol metabolism, and exerting antiinflammatory and antitumour effects. Previous studies have reported that sesamin can inhibit the proliferation of several types of tumour cells and exert antitumour effects. However, the antitumour effect of sesamin on T-cell lymphoma is still unknown. In this study, we selected a T-cell lymphoma mouse model to investigate the mechanism of sesamin against T-cell lymphoma via programmed cell death in vivo and in vitro. We found that sesamin could significantly inhibit the growth of EL4 cells in a tumour-bearing mouse model. Sesamin markedly inhibited the proliferation of EL4 cells by inducing apoptosis, pyroptosis and autophagy. Autophagy occurred earlier than apoptosis and pyroptosis in EL4 cells after sesamin treatment. Blocking autophagy inhibited apoptosis and pyroptosis in EL4 cells after sesamin treatment. Taken together, these results suggested that sesamin promoted apoptosis and pyroptosis via autophagy to enhance antitumour effects on murine T-cell lymphoma. This study expands our knowledge of the pharmacological effects of sesamin on T-cell lymphoma, and provides a theoretical basis for the development of new antitumour drugs and treatments for T-cell lymphoma.

Tumor immunogenicity status in high-grade serous ovarian cancer

Tumor immunogenicity status in high-grade serous ovarian cancer

Pyrimethamine Modulates Interplay between Apoptosis and Autophagy in Chronic Myelogenous Leukemia Cells

Pyrimethamine (Pyri) is being used in combination with other medications to treat serious parasitic infections of the body, brain, or eye and to also reduce toxoplasmosis infection in the patients with HIV infection. Additionally, Pyri can display significant anti-cancer potential in different tumor models, but the possible mode of its actions remains unclear. Hence, in this study, the possible anti-tumoral impact of Pyri on human chronic myeloid leukemia (CML) was deciphered. Pyri inhibited cell growth in various types of tumor cells and exhibited a marked inhibitory action on CML cells. In addition to apoptosis, Pyri also triggered sustained autophagy. Targeted inhibition of autophagy sensitized the tumor cells to Pyri-induced apoptotic cell death. Moreover, the activation of signal transducer and activator of transcription 5 (STAT5) and its downstream target gene Bcl-2 was attenuated by Pyri. Accordingly, small interfering RNA (siRNA)-mediated STAT5 knockdown augmented Pyri-induced autophagy and apoptosis and promoted the suppressive action of Pyri on cell viability. Moreover, ectopic overexpression of Bcl-2 protected the cells from Pyri-mediated autophagy and apoptosis. Overall, the data indicated that the attenuation of STAT5-Bcl-2 cascade by Pyri can regulate its growth inhibitory properties by simultaneously targeting both apoptosis and autophagy cell death mechanism(s).

Targeting Cancer Metabolism Breaks Radioresistance by Impairing the Stress Response.

Simple SummaryIonizing radiation is a major pillar in the therapy of solid tumors. However, normal tissue toxicities and radioresistance of tumor cells can limit the therapeutic success of radiotherapy. In this study, we investigated the coregulation of the cancer metabolism and the heat shock response with respect to radioresistance. Our results indicate that an inhibition of lactate dehydrogenase, either pharmacologically or by gene knockout of LDHA and LDHB, significantly increases the radiosensitivity in tumor cells by global impairing of the stress response. Therefore, inhibition of the lactate metabolism might provide a promising strategy in the future to improve the clinical outcome of patients with highly aggressive, therapy-resistant tumors.The heightened energetic demand increases lactate dehydrogenase (LDH) activity, the corresponding oncometabolite lactate, expression of heat shock proteins (HSPs) and thereby promotes therapy resistance in many malignant tumor cell types. Therefore, we assessed the coregulation of LDH and the heat shock response with respect to radiation resistance in different tumor cells (B16F10 murine melanoma and LS174T human colorectal adenocarcinoma). The inhibition of LDH activity by oxamate or GNE-140, glucose deprivation and LDHA/B double knockout (LDH−/−) in B16F10 and LS174T cells significantly diminish tumor growth; ROS production and the cytosolic expression of different HSPs, including Hsp90, Hsp70 and Hsp27 concomitant with a reduction of heat shock factor 1 (HSF1)/pHSF1. An altered lipid metabolism mediated by a LDHA/B double knockout results in a decreased presence of the Hsp70-anchoring glycosphingolipid Gb3 on the cell surface of tumor cells, which, in turn, reduces the membrane Hsp70 density and increases the extracellular Hsp70 levels. Vice versa, elevated extracellular lactate/pyruvate concentrations increase the membrane Hsp70 expression in wildtype tumor cells. Functionally, an inhibition of LDH causes a generalized reduction of cytosolic and membrane-bound HSPs in tumor cells and significantly increases the radiosensitivity, which is associated with a G2/M arrest. We demonstrate that targeting of the lactate/pyruvate metabolism breaks the radioresistance by impairing the stress response.

LC-MS/MS method for the quantification of the anti-cancer agent infigratinib: Application for estimation of metabolic stability in human liver microsomes

Infigratinib (INF) is a novel small molecule, administered orally, which acts as a human fibroblast growth factor receptors (FGFRs) inhibitor. FGFRs are a family of receptor tyrosine kinases (RTK) reported to be upregulated in various tumor cell types. In 1 December 2020, BridgeBio Pharma Inc. announced FDA approval of INF as a New Drug Application, granting it Priority Review for the treatment of cholangiocarcinoma (CCA). Thus, the current study aimed to establish a validated LC-MS/MS method to estimate the INF concentration in the HLM matrix. In silico prediction of INF metabolism was done using the StarDrop® WhichP450™ module to verify its metabolic stability. An accurate and efficient LC-MS/MS analytical method was developed for INF metabolic stability evaluation. INF and duvelisib (DVB) (internal standard; IS) were eluted using an isocratic mobile phase with a C18 column as a stationary reversed phase. The established LC-MS/MS method showed a linear range over 5–500 ng/mL (r2 ≥ 0.9998) in human liver microsomes (HLMs). The sensitivity of the method was confirmed at its limit of quantification (4.71 ng/mL), and reproducibility was indicated by inter- and intra-day accuracy and precision (within 7.3%). The evaluation of INF metabolic stability was assessed, which reflected an intrinsic clearance of 23.6 µL/min/mg and in vitro half-life of 29.4 min. The developed approach in the current study is the first LC-MS/MS method for INF metabolic stability assessment. Application of the developed method in HLM in vitro studies suggests that INF has a moderate extraction ratio, indicating relatively good predicted oral bioavailability.

A novel mitochondrial Kv1.3-caveolin axis controls cell survival and apoptosis.

The voltage-gated potassium channel Kv1.3 plays an apparent dual physiological role by participating in activation and proliferation of leukocytes as well as promoting apoptosis in several types of tumor cells. Therefore, Kv1.3 is considered a potential pharmacological target for immunodeficiency and cancer. Different cellular locations of Kv1.3, at the plasma membrane or the mitochondria, could be responsible for such duality. While plasma membrane Kv1.3 facilitates proliferation, the mitochondrial channel modulates apoptotic signaling. Several molecular determinants of Kv1.3 drive the channel to the cell surface, but no information is available about its mitochondrial targeting. Caveolins, which are able to modulate cell survival, participate in the plasma membrane targeting of Kv1.3. The channel, via a caveolin-binding domain (CDB), associates with caveolin 1 (Cav1), which localizes Kv1.3 to lipid raft membrane microdomains. The aim of our study was to understand the role of such interactions not only for channel targeting but also for cell survival in mammalian cells. By using a caveolin association-deficient channel (Kv1.3 CDBless), we demonstrate here that while the Kv1.3-Cav1 interaction is responsible for the channel localization in the plasma membrane, a lack of such interaction accumulates Kv1.3 in the mitochondria. Kv1.3 CDBless severely affects mitochondrial physiology and cell survival, indicating that a functional link of Kv1.3 with Cav1 within the mitochondria modulates the pro-apoptotic effects of the channel. Therefore, the balance exerted by these two complementary mechanisms fine-tune the physiological role of Kv1.3 during cell survival or apoptosis. Our data highlight an unexpected role for the mitochondrial caveolin-Kv1.3 axis during cell survival and apoptosis.

Abstract 1789: Triggering anti-tumor immunity by overexpressing of MAVS in combination with PD-L1 ICB in immune insensitive colorectal cancers

Abstract While the use of immune checkpoint blockade (ICB) has gained significant traction as a viable therapy for cancers, many more cancers remain refractory to these immunotherapies due to their highly immunosuppressive tumor microenvironment (TME). From both the earlier published report and our analysis of clinical cohorts of colorectal cancer, we found that the expression of MAVS (Mitochondrial Antiviral Signaling Protein) was significantly reduced. Because MAVS are known to play a key role in the initiation of anti-viral innate immunity, we hypothesized that MAVS may be critical in anti-tumor immune response and tumor cells are under evolutionary pressure to reduce MAVS expression. As such, the stimulation of the MAVS pathway in tumor cells may be a necessary precursor to trigger anti-tumor immune response and reverse local immunosuppressive TME. To circumvent issues associated with intracellular double stranded RNA ligand stimulation, we exploited the ability of MAVS to constitutively polymerize and elicit broad downstream interferon signaling through an overexpression strategy. This approach provided a novel genetic mean to elicit ligand free innate immune signaling in the TME, which we found to elicit robust stimulation of multiple interferon genes. Overexpression of MAVS in colorectal cell lines stimulated significant anti-tumors responses in vivo, which we found to be primarily mediated through the induction of tumor antigen-specific adaptive immunity. Utilizing viral vectors overexpressing MAVS, we demonstrate significant induction of interferon responses among different types of tumor cells and different types of cells in the tumor microenvironment. Intra-lesional injection of tumors using these vectors elicited profound anti-tumor responses against primary tumors, as well as, an abscopal effect against syngeneic implanted tumors. Overexpression of MAVS also stimulated the expression of PD-L1 as an immunosuppressive feedback mechanism due to stimulation of the MAVS pathway. As such, we tested the combination of MAVS overexpression and PD-L1 ICB in colorectal cancers and found that this combination allowed for significantly improved anti-tumor immunity. In conclusion, our findings suggest that a combination of MAVS cancer gene therapy and ICB may offer an alternative approach to activate immunity in "immunologically cold" tumors. Citation Format: Bin-Jin Hwang. Triggering anti-tumor immunity by overexpressing of MAVS in combination with PD-L1 ICB in immune insensitive colorectal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1789.

Abstract 1202: ERG344: A novel IRG1 inhibitor for the treatment of colon cancer

Abstract Immune responsive gene 1 (Irg1) is an LPS-inducible gene within macrophages (MF) whose protein product is responsible for the synthesis of itaconate from aconitate through a break in the TCA cycle. Although primarily present in proinflammatory macrophages, IRG1 expression has been linked with certain cancers (glioblastoma, ovarian carcinoma) and its tumor-driven upregulation in peritoneal resident macrophages (pResMF) has been shown to contribute to peritoneal tumor growth. Here, we report Irg1 gene expression at the single cell level (scRNAseq) in samples obtained from colorectal cancer patients (n=7; ~11,000 single cells). Transcriptomic analysis showed that Irg1 was primarily expressed by cancer cells, although other tumoral cell types also showed substantial levels of the gene. To determine if IRG1 is a druggable target in cancer, we synthesized a series of small MW inhibitors and selected ERG344 for in vivo testing based on its ability to inhibit itaconate synthesis in a rat glioblastoma cell line (C6) engineered to stably express Irg1. The IC50 value of inhibition was ~150 μM. In vivo, ERG344 suppressed tumor growth and increased survival probability in a syngeneic colon cancer model (CT26). Drug administration was initiated when the tumors reached an average tumor volume of ~100 mm3 and involved daily ERG344 doses of 0.2 mg/kg ip or 0.3 mg/kg po. Complete tumor regressions (~17%) were observed in the same model when ERG344 was administered ip at 3 mg/kg. Immunophenotyping of CT26 tumors treated with either vehicle or 0.2 mg/kg ERG344 ip indicated that IRG1 inhibition renders the tumor microenvironment less immunosuppressive by decreasing the frequency of monocytic myeloid suppressor cells (m-MDSCs), increasing the frequency of cytotoxic CD8+ T cells, and decreasing the CD8+ expression of the negative co-stimulatory molecule PD-1. To determine if ERG344 is also able to reduce pResMF-driven peritoneal tumor growth, murine melanoma B16F15 cells were injected into the peritoneal cavity of C57BL/6 mice treated with vehicle or 1 mg/kg ERG344 (n=8/group). Seven days after tumor inoculation, mice treated with ERG344 showed reduced tumor growth in the peritoneal cavity, which led to increased survival probability of the animals. The studies collectively suggest that IRG1 is a novel target for the treatment of primary and metastatic tumor growth in colorectal cancer and highlight the therapeutic potential of ERG344. Citation Format: Adonia E. Papathanassiu, Francesca Lodi, Hong A. Vu, Diether Lambrechts. ERG344: A novel IRG1 inhibitor for the treatment of colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1202.

Abstract 178: Desmosome mutations in melanoma promote cellular proliferation and disease progression

Abstract Desmosomes are transmembrane protein complexes that contribute to cell-cell adhesion in the epithelia and other tissues under mechanical stress. Aberrant desmosome expression is often associated with developmental diseases leading to impaired tissue integrity. Recently, similar findings have been reported in cancer; Mutations in desmosomes genes have been observed in various cancer types including skin cancer, head and neck and lung cancer, however mostly epigenetic alterations have been used to associate desmosomes as suppressors of tumor metastasis. Here, we report that desmosomes are frequently mutated in seven cancer types. In melanoma, we find that over 70% of tumors have non-synonymous mutations in desmosomes, and that the desmosome mutational burden is associated with a strong decrease in mRNA expression levels in primary tumor samples (R = -0.23). Differential gene expression analysis and functional characterizations between mutant and wild-type tumors implicates the mutated cells in promoting cell proliferation at early stages of tumorigenesis. These results emerge uniquely from a systems-level analysis integrating multiple proteins in complexes and multiple cell types in heterogeneous tumors. Citation Format: Maayan Baron, Trey Ideker. Desmosome mutations in melanoma promote cellular proliferation and disease progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 178.

Abstract 2795: Estimation of cell lineage and inter-cell interactions from spatial transcriptomics data

Abstract The spatial transcriptomics (ST) technology has enabled geographical profiling of tumor gene expression. However, each ST spot may detect mixture signals from diverse immune or malignant cells of unknown lineages, and local tissue densities may vary significantly across regions. Therefore, the decomposition of ST cell lineages remains a challenge that cannot be resolved by previous decomposition methods for fixed cell types in bulk tumors. We developed the Spatial Cell Estimator (SpaCE) to infer the cell identities and intercellular interactions for tumor ST data. SpaCE first estimates the cancer cell clonal abundance through modeling the copy number segmental variations across ST spots. Then, we utilized a constrained regression to determine the hierarchy of immune cell lineages and local tissue densities. The prediction accuracy was validated through both simulation and double-blinded pathology annotations on hematoxylin and eosin images. Based on reliable cell lineage inference, SpaCE can further reveal how intercellular interactions affect the pathway and gene activities in distinct regions to modulate the cancer progression. Citation Format: Beibei Ru, Jinlin Huang, Yu Zhang, Kenneth Aldape, Peng Jiang. Estimation of cell lineage and inter-cell interactions from spatial transcriptomics data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2795.

Abstract 1636: CLEC-1 is a novel myeloid immune checkpoint for cancer immunotherapy limiting tumor cells phagocytosis and tumor antigen cross-presentation

Abstract Myeloid cells represent one of the most abundant immune cell types in solid tumors that impede myeloid phagocytosis by triggering “don't eat me” and “don't find me” signals. Recent literature demonstrates that C-type lectin receptors (CLRs) are powerful pattern recognition receptors shaping immune cell-mediated tissue damage by positively or negatively regulating myeloid cell functions and hence tumor elimination or evasion. We previously reported that the orphan CLR CLEC-1 expressed by dendritic cells (DCs) and macrophages (MPs) is enhanced by TGFβ and tempers downstream T cells responses. Furthermore, we observed that CLEC-1 is highly expressed by myeloid cells purified from the human tumor microenvironment, in particular, tumor-associated MPs. We evaluated whether CLEC-1 could also be a receptor for DAMPs and influences phagocytosis. We found that CLEC-1 fusion protein binds specifically to secondary necrotic healthy or tumor cells induced by chemotherapy, radiation (UV, X-ray), or culture stress conditions suggesting that ligands of CLEC-1 are generated upon stress and programmed cell death. Importantly, further to promising results in KO CLEC-1 mice, we observed in vivo that CLEC-1 deficient mice, in contrast to wild-type littermates, eradicate MC38 colorectal tumors in combination with cytotoxic and immunogenic chemotherapy. Importantly, disruption of CLEC-1 signaling by Fc-CLEC-1 fusion protein also promotes tumor eradication. We then generated and identified different anti-human CLEC-1 antagonist monoclonal antibodies (mAbs) with the capacity to block CLEC-1/CLEC-1L interaction. We developed innovative antagonist CLEC-1 mAbs which, in contrast to non-antagonist CLEC-1 control mAb, increase the phagocytosis of CLEC-1L-positive human tumor cells by human TGFβ-polarized DCs or MPs. Indeed, TGFβ-polarized DCs phagocytose more efficiently a NSCLC cell line (A549) as well as Rituximab (anti-CD20 mAb)-opsonized Burkitt lymphoma cells (Raji) when CLEC-1 is antagonized by Abs. Similarly, macrophages significantly more efficiently engulfed human tumors in the presence of CLEC-1 antagonist Abs, in particular when tumor cells were opsonized such as Rituximab-opsonized Raji cells, Cetuximab opsonized colon carcinoma cells (DLD-1; EGFR+) or Trastuzumab opsonized mammary carcinoma cells (SK-BR-3; Her2+). Importantly, we observed both in vitro and in vivo that DCs from Clec1a deficient mice cross-present more efficiently dead cell-associated antigens to CD8+ T cells (OT-1). We generated hCLEC-1 knock-in mice and in vivo preclinical evaluation of CLEC-1 blocking mAbs is ongoing. Altogether, these data illustrate that CLEC-1 broadly notably inhibits tumor-cell phagocytosis and synergized with tumor-targeted cytotoxic monoclonal antibodies in both solid and hematological tumors, and hampers DC antigen cross-presentation. Citation Format: Vanessa Gauttier, Sabrina Pengam, Marion Drouin, Javier Saenz, Bérangère Evrard, Kevin Biteau, Caroline Mary, Géraldine Teppaz, Ariane Desselle, Virginie Thépénier, Emmanuelle Wilhelm, Elise Chiffoleau, Nicolas Poirier. CLEC-1 is a novel myeloid immune checkpoint for cancer immunotherapy limiting tumor cells phagocytosis and tumor antigen cross-presentation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1636.