Osteosarcoma Model Research Articles

Osteosarcoma-Induced Pain Is Mediated by Glial Cell Activation in the Spinal Dorsal Horn, but Not Capsaicin-Sensitive Nociceptive Neurons: A Complex Functional and Morphological Characterization in Mice.

Bone cancer and its related chronic pain are huge clinical problems since the available drugs are often ineffective or cannot be used long term due to a broad range of side effects. The mechanisms, mediators and targets need to be identified to determine potential novel therapies. Here, we characterize a mouse bone cancer model induced by intratibial injection of K7M2 osteosarcoma cells using an integrative approach and investigate the role of capsaicin-sensitive peptidergic sensory nerves. The mechanical pain threshold was assessed by dynamic plantar aesthesiometry, limb loading by dynamic weight bearing, spontaneous pain-related behaviors via observation, knee diameter with a digital caliper, and structural changes by micro-CT and glia cell activation by immunohistochemistry in BALB/c mice of both sexes. Capsaicin-sensitive peptidergic sensory neurons were defunctionalized by systemic pretreatment with a high dose of the transient receptor potential vanilloid 1 (TRPV1) agonist resiniferatoxin (RTX). During the 14- and 28-day experiments, weight bearing on the affected limb and the paw mechanonociceptive thresholds significantly decreased, demonstrating secondary mechanical hyperalgesia. Signs of spontaneous pain and osteoplastic bone remodeling were detected both in male and female mice without any sex differences. Microglia activation was shown by the increased ionized calcium-binding adapter molecule 1 (Iba1) immunopositivity on day 14 and astrocyte activation by the enhanced glial fibrillary acidic protein (GFAP)-positive cell density on day 28 in the ipsilateral spinal dorsal horn. Interestingly, defunctionalization of the capsaicin-sensitive afferents representing approximately 2/3 of the nociceptive fibers did not alter any functional parameters. Here, we provide the first complex functional and morphological characterization of the K7M2 mouse osteosarcoma model. Bone-cancer-related chronic pain and hyperalgesia are likely to be mediated by central sensitization involving neuroinflammation via glial cell activation in the spinal dorsal horn, but not the capsaicin-sensitive sensory neuronal system.

Establishment of a prognostic risk model for osteosarcoma and mechanistic investigation.

Objective: To investigate the immune mechanism of osteosarcoma (OS)-specific markers to mitigate bone destruction in the aggressive OS, prone to recurrence and metastasis. Methods: Gene expression patterns from the Gene Expression Omnibus (GEO) database (GSE126209) were analyzed using weighted gene co-expression network analysis (WGCNA), protein-protein interaction (PPI) analysis, least absolute shrinkage and selection operator (LASSO) modeling, and survival analysis to identify charged multivesicular body protein 4C (CHMP4C). Subsequently, its role in regulating the immune system and immune cell infiltration was explored. CHMP4C expression and signaling molecules in OS were assessed in osteosarcoma cell lines (MG63, U2OS, HOS) and hFOB1.19 cells using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence staining. The impact of CHMP4C upregulation and interference on OS-related signaling molecules in MG63 cells was studied. Functional validation of CHMP4C in MG63 OS cells was confirmed through cell counting Kit-8 (CCK-8), transwell, and colony formation assays. In vivo experiments were conducted using Specific Pathogen Free (SPF)-grade male BALB/C nude mice for OS xenograft studies. Results: Based on the gene expression profiles analysis of six osteosarcoma samples and six normal tissue samples, we identified 1,511 upregulated DEGs and 5,678 downregulated DEGs in normal tissue samples. A significant positive correlation between the "yellow-green" module and OS was found through WGCNA analysis. Expression levels of CHMP4C, phosphorylated Glycogen Synthase Kinase 3β (p-GSK3β), and β-catenin were notably higher in U2OS, HOS, and MG63 OS cells than in hFOB1.19 human osteoblasts. Overexpressing CHMP4C in MG63 OS cells upregulated CHMP4C, p-GSK3β, and β-catenin while downregulating GSK3β, leading to increased proliferation and migration of MG63 cells. Conversely, interrupting CHMP4C had the opposite effect. High expression of CHMP4C significantly accelerated the growth of OS in nude mice, resulting in substantial upregulation of CHMP4C, p-GSK3β, and β-catenin expression and suppression of Glycogen Synthase Kinase 3β (GSK3β) expression in OS tissues. Conclusion: CHMP4C may serve as a specific immunomodulatory gene for OS. Its activation of the Wnt/β-catenin signaling pathway, mainly by increasing the phosphorylation echelon of GSK3β, promotes the invasion and spread of OS.

Stabilizing Tumor-Resident Mast Cells Restores T-Cell Infiltration and Sensitizes Sarcomas to PD-L1 Inhibition.

To explore the cellular cross-talk of tumor-resident mast cells (MC) in controlling the activity of cancer-associated fibroblasts (CAF) to overcome tumor microenvironment (TME) abnormalities, enhancing the efficacy of immune-checkpoint inhibitors in sarcoma. We used a coculture system followed by further validation in mouse models of fibrosarcoma and osteosarcoma with or without administration of the MC stabilizer and antihistamine ketotifen. To evaluate the contribution of ketotifen in sensitizing tumors to therapy, we performed combination studies with doxorubicin chemotherapy and anti-PD-L1 (B7-H1, clone 10F.9G2) treatment. We investigated the ability of ketotifen to modulate the TME in human sarcomas in the context of a repurposed phase II clinical trial. Inhibition of MC activation with ketotifen successfully suppressed CAF proliferation and stiffness of the extracellular matrix accompanied by an increase in vessel perfusion in fibrosarcoma and osteosarcoma as indicated by ultrasound shear wave elastography imaging. The improved tissue oxygenation increased the efficacy of chemoimmunotherapy, supported by enhanced T-cell infiltration and acquisition of tumor antigen-specific memory. Importantly, the effect of ketotifen in reducing tumor stiffness was further validated in sarcoma patients, highlighting its translational potential. Our study suggests the targeting of MCs with clinically administered drugs, such as antihistamines, as a promising approach to overcome resistance to immunotherapy in sarcomas.

CPPs-modified chitosan as permeability-enhancing chemotherapeutic combined with gene therapy nanosystem by thermosensitive hydrogel for the treatment of osteosarcoma

BackgroundChemotherapy resistance of osteosarcoma (OS) is still the crux of poor clinical curative effect.E3 ubiquitin-protein ligase Rad18 (Rad18) contributed to doxorubicin resistance in OS, which ultimately mediated DNA damage tolerance and led to a poor prognosis and chemotherapy response in patients. MethodsIn this study, doxorubicin was loaded in the process of Fe2+ and siRad18 forming nanoparticles(FSD) through coordination, chitosan modified with cell penetrating peptide (H6R6) was synthesized and coated on the surface of the NPs(FSD-CHR). FSD-CHR was then dispersed in thermosensitive hydrogel(PPP) for peritumoral injection of osteosarcoma in situ. Subsequently, the physicochemical properties and molecular biological characteristics of the drug delivery system were characterized. Finally, an osteosarcoma model was established to study the anti-tumor effects of multifunctional nanoparticles and the immunotherapy effect combined with αPD-L1. ResultsFSD-CHR has enhanced tumor tissue permeability, siRad18 can significantly reduce Dox-mediated DNA damage tolerance and enhance anti-tumor effects, and iron-based NPs show enhanced ROS upregulation. FSD-CHR@PPP showed significant inhibition of osteosarcoma growth in vivo and a reduced incidence of lung metastasis. In addition, siRad18 was unexpectedly found to enhance Dox-mediated immunogenic cell death (ICD).FSD-CHR@PPP combined with PD-L1 blocking significantly enhanced anti-tumor effects due to decreased PD-L1 enrichment. ConclusionHydrogel encapsulation of permeable nanoparticles provides an effective strategy for doxorubicin-resistant OS, showing that gene therapy blocking DNA damage tolerance can enhance treatment response to chemotherapy and appears to enhance the effect of ICD inducers to activate the immune system.

Paucatalinone A from Paulownia Catalpifolia Gong Tong Elicits mitochondrial-mediated cancer cell death to combat osteosarcoma.

As the global cancer burden escalates, the search for alternative therapies becomes increasingly vital. Natural products, particularly plant-derived compounds, have emerged as promising alternatives to conventional cancer treatments due to their diverse bioactivities and favorable biosafety profiles. Here, we investigate Paucatalinone A, a newly discovered geranylated flavanone derived from the fruit of Paulownia Catalpifolia Gong Tong, notable for its significant anti-cancer properties. We revealed the capability of Paucatalinone A to induce apoptosis in osteosarcoma cells and deciphered its underlying mechanisms. Our findings demonstrate that Paucatalinone A substantially augments apoptosis, inhibits cell proliferation, and demonstrates a pronounced anti-tumor effect in a murine model of osteosarcoma. Mechanistically, Paucatalinone A disrupts calcium homeostasis and exacerbates intracellular reactive oxygen species accumulation, leading to mitochondrial impairment, cytoskeletal collapse, and caspase-dependent apoptotic cell death. This study underscores the potential of Paucatalinone A in initiating apoptosis in cancer cells and highlights the therapeutic efficacy of plant-derived agents in treating osteosarcoma, offering a viable approach for managing other intractable cancers.

Establishment of humanised xenograft models as in vivo study for lung metastasis of osteosarcoma.

Humanised xenograft models and cancer cell lines are widely used for preclinical drug evaluation, biological studies, and targeted therapy strategies in cancer research. A humanised mouse model is a laboratory mouse that has been genetically modified to contain specific human genes, cells, or tissues. By introducing human-specific elements into rodents, researchers can create a more accurate representation of human physiological and pathological processes. Lacking an appropriate animal model for osteosarcoma (OS), hindered understanding of underlying mechanisms in OS metastasis progression. Markedly, metastasis influences the prognosis and treatment of osteosarcoma. Gaining insight into the mechanisms and occurrences of metastasis could potentially facilitate oncologists in improving therapies. Hence, it is important to develop a lung metastatic OS model to study the basic biology of its progression. This study has established a tumour-bearing mouse model using HOS-143B cell line which was injected into male NOD.SCID gamma (NSG) mice at two locations; intramuscularly (hind leg) and subcutaneously (back) respectively. The primary and metastatic tumour size was monitored by palpating the area of tumour induced and quantified using digital calliper. H&E staining was performed by pathologist to confirm metastasis. Our results showed that mice injected with 1 million cancer cells were unable to produce tumours. Meanwhile, mice injected with three million cancer cells showed tumour development and lung metastasis after 25 days of cancer cell inoculation. In conclusion, this study has successfully established a lung metastatic OS mouse model that could be useful for biological studies of OS. These findings imply that this model is essential for safety and efficacy before clinical trials, accelerate the translation from basic research to therapeutic applications.

Abstract 1084: Preclinical testing of a cell adhesion molecule 1 (CADM1) targeting antibody-drug conjugate in osteosarcoma and other pediatric solid tumor models

Abstract Introduction: Survival outcomes of osteosarcoma have remained stagnant for decades, emphasizing the urgent need to identify new cell surface targets and develop novel therapies. Antibody-drug conjugates (ADCs), known for their targeted delivery of cytotoxic agents to specific targets, present an attractive therapeutic class for potential use in osteosarcoma. Methods: We previously identified Cell Adhesion Molecule 1 (CADM1) is highly expressed on the cell surface in osteosarcoma using an integrated proteomic and transcriptomic surfaceome profiling approach. As a proof of concept, a humanized CADM1 antibody (clone PTA021-A1) was conjugated with Tesirine (SG3249), a pyrrolobenzodiazepine (PBD) dimer payload. The antitumor activity of this CADM1 ADC was validated in vivo in 8 osteosarcoma patient-derived xenografts (PDXs). CADM1 is also highly expressed in other pediatric solid malignancies such as neuroblastoma and Wilms tumor. The CADM1 ADC was tested in vitro in neuroblastoma and Wilms tumor models. Negative controls included a CD19 targeting ADC with the same payloads and CADM1 negative Ewing sarcoma models. Results: The expression of the CADM1 was validated by flow cytometry in osteosarcoma, neuroblastoma, and Wilms tumor cell lines, and by immunohistochemistry (IHC) in osteosarcoma patient samples and PDX models. In vivo testing of CADM1 ADC in 8 osteosarcoma PDX models showed that the ADC was well-tolerated and significantly prolonged progressive-free survival in all osteosarcoma models. Complete response (CR) and maintained CR was observed in 3 models. In vitro testing for neuroblastoma and Wilms tumor is ongoing, and preliminary data suggest promising antitumor activities. Conclusions: CADM1 is highly expressed in osteosarcoma and other pediatric solid tumors. CADM1 ADC demonstrated promising antitumor in vitro and in vivo activity in osteosarcoma, and initial in vitro studies in neuroblastoma and Wilms tumor show similarly promising responses. These data support the need for further studies assessing the potential of a CADM1 ADC as a novel agent for the treatment of pediatric solid cancers. Citation Format: Zhongting Zhang, Yifei Wang, Wendong Zhang, Xiangjun Tian, Qi Wang, Rossana N Lazcano Segura, Michael Roth, Jonathan Gill, Douglas Harrison, Zhaohui Xu, Yianhua Yi, Sylvester Jusu, Giuseppe Longo, Xin Zhou, Jing Wang, Richard Gorlick. Preclinical testing of a cell adhesion molecule 1 (CADM1) targeting antibody-drug conjugate in osteosarcoma and other pediatric 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 1084.

Abstract 3912: ATM and PARP combined inhibition demonstrate synergistic antitumor efficacy in osteosarcoma models

Abstract Signatures of BRCAness are found in many osteosarcoma (OS) tumors, driving an interest in PARP inhibition (PARPi) for OS treatment. Although PARPi have shown limited efficacy as OS monotherapy, rational combination strategies have not yet been explored for this disease. We performed a genome-scale loss-of-function CRISPR-Cas9 screen in two OS cell lines in the presence and absence of olaparib, a small molecule PARPi. ATM knockout (KO) scored highly as a potent synergizer of PARPi across both cell lines. Here we report this screen finding as well as in vitro validation of PARPi and ATM inhibition (ATMi) synergy in OS models. OS cell lines SAOS2 and CAL72 were infected with the Avana genome-scale lentiviral CRISPR library, targeting 20,000 genes with 4 uniquely barcoded guides (sgRNAs) per gene. After infection and antibiotic selection, cells were grown in an IC40 dose of olaparib or matched control for 18 days. Following DNA sequencing of barcodes and rigorous quality control, sgRNA dropout hits were calculated against the control arm. ATM KO sensitizing to PARPi was first validated utilizing a CRISPR-based genetic approach. ATM KO in CAL72 and SAOS2 was performed via lentiviral infection. After KO confirmation by western immunoblotting (WB), ATM KO and control KO cells were treated with PARPi in a dose range of 19.5 nM-10 µM. ATP-based and Incucyte assays were used to quantify differential cell viability. Secondly, the combination of a small molecule ATMi and a PARPi was studied in a panel of OS cell lines. Synergistic cytotoxicity was quantified using the Zero Interaction Potency (ZIP) model. DNA damage levels after PARPi and ATMi (by chemical inhibition and genetic KO) were assessed by WB for γH2AX, a marker of DNA double-stranded breaks (DSBs). In our genome-scale CRISPR screens, ATM arose as a top druggable hit across both lines. Reassuringly, PARP1 KO scored as a top resistance mediator to PARPi, confirming biologic relevance of the screen and supporting the known PARP-trapping mechanism of these drugs in OS. At low-throughput, ATM KO lines trended toward increased sensitivity to PARPi in short-term viability assays. Combined chemical inhibition yielded highly synergistic ZIP scores across OS cell lines; synergy was achieved with both drugs in the low nanomolar range. γH2AX levels were substantially increased in the setting of combined PARPi and ATMi (via chemical inhibition or genetic KO) as compared to inactivation of either PARP or ATM alone, indicating increased presence of DNA DSBs. In conclusion, these data demonstrate synergy of ATM and PARP inhibition, providing promise for their potential combined use in the treatment of OS. Accumulation of DNA DSBs in response to PARP and ATM inactivation suggests a shared role in DNA damage repair as the molecular basis of synergism. Ongoing studies are investigating anti-tumor potential in in vivo OS models and exploring the mechanistic impact of the combination in OS tumors. Citation Format: Sona N. Kocinsky, Janeala J. Morsby, William C. Wright, Monika Wierdl, Caroline S. Wechsler, Gabriela Alexe, Paul Geeleher, Kimberly Stegmaier, Lillian M. Guenther. ATM and PARP combined inhibition demonstrate synergistic antitumor efficacy in osteosarcoma 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 3912.

Abstract 4273: Genetically engineered mesenchymal stromal cells degrade hyaluronic acid to disrupt the ECM and enhance cancer therapy outcomes

Abstract The extracellular matrix (ECM) is a vital component of cancer pathophysiology. However, little is known about how to modulate the ECM for therapeutic benefit effectively. Hyaluronic acid (HA) is a polysaccharide component of the ECM with increased deposition during tissue injury or inflammation. HA in the tumor microenvironment (TME) has been linked to aggressive cancer progression. We have found enhanced ECM remodeling behavior linked to pre-metastatic niche formation and metastatic progression. To remodel this ECM-enriched microenvironment, we developed HA-targeting genetically engineered mesenchymal stromal cells (GEMesys) expressing hyaluronidase (Hyal), the enzyme responsible for HA degradation. We examined the impact of Hyal-GEMesys in osteosarcoma (F42010), rhabdomyosarcoma (M-3-9M), and pancreatic cancer (Panc02) syngeneic murine models. Hyal-GEMesys delivered to tumor-bearing mice homed to primary tumor sites and successfully degraded HA in the TME. The degradation of HA also resulted in a significant remodeling of collagen. T cells in Hyal-GEMesy treated tumors display an activated CD4+CD44+ phenotype with a reduction of LAG3+PD1+ exhaustion markers. Additionally, Hyal-GEMesy treatment results in a significant decrease in hypoxic regions within tumors and reorganization of the tumor vasculature to a more normalized phenotype, marked by diminished CD31 expression. Hyal-GEMesy treatment reduces tumor volumes in osteosarcoma, rhabdomyosarcoma, and pancreatic cancer models and enhances chemotherapeutic efficacy. These findings suggest that reorganizing the tumor ECM with Hyal-GEMesys holds the potential to dismantle the protective stroma of the tumor, which often shields malignant cells from therapeutic reach, and combining anti-cancer and anti-stroma agents can enhance anti-tumor efficacy and patient outcomes. Citation Format: Alice T. Browne, Miranda Clements, Wei Ju, Rosandra Kaplan. Genetically engineered mesenchymal stromal cells degrade hyaluronic acid to disrupt the ECM and enhance cancer therapy outcomes [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 4273.

Abstract 4069: IL12-expressing genetically engineered myeloid cells remodel the stromal dense and T cell poor tumor microenvironment and premetastatic niche of F42010 murine osteosarcoma

Abstract Treatment options for patients with metastatic and recurrent osteosarcoma are poor. The development of immunotherapies for osteosarcoma has been hindered by the lack of immunocompetent preclinical models that recapitulate the stromal dense, myeloid-rich, T cell poor, and overall immunosuppressive microenvironment of human osteosarcoma. We hypothesized that the syngeneic murine osteosarcoma model F42010 may serve as a useful immunocompetent preclinical model of osteosarcoma suitable for developing novel immunotherapies for osteosarcoma. To test this, we used flow cytommetry, bulk RNA sequencing, and immunohistochemistry to characterize the stromal and immune compartments of this model. We found that the F42010 osteosarcoma model recapitulates the ECM-rich and immunosuppressive nature of human osteosarcoma primary tumor and pre-metastatic microenvironments, characterized by increased myeloid infiltrate expressing suppressive markers and lymphocyte exhaustion. Finally, we used this model to test the utility of a myeloid immunotherapy for osteosarcoma, IL-12 secreting genetically engineered myeloid cells (IL12-GEMys) that can reverse immune suppression in the pre-metastatic niche and tumor microenvironment. IL12-GEMy treatment augmented immune activation and significantly extended survival by delaying tumor growth. Our findings highlight that the F42010 osteosarcoma model effectively replicates key features of the osteosarcoma tumor microenvironment and is a valuable model for developing novel tumor microenvironment and pre-metastatic niche modulating immunotherapies for osteosarcoma. Citation Format: Kailey Jackett, Alice Browne, Sabina Kaczanowska, Miranda Clements, Rosandra Kaplan, Kristin Wessel, Brendan Ball, James Cronk. IL12-expressing genetically engineered myeloid cells remodel the stromal dense and T cell poor tumor microenvironment and premetastatic niche of F42010 murine osteosarcoma [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 4069.

Abstract 7156: Targeting the β-catenin signaling axis in osteosarcoma

Abstract Osteosarcoma, an aggressive bone malignancy predominantly affecting children, poses a formidable challenge for therapeutic interventions. Here we evaluated a recently approved FDA drug, PCT, for potential anti-cancer effect in osteosarcoma model. Initial assessments of cytotoxicity encompassing various human and murine osteosarcoma cell lines—OS-17, OS-25, U2OS, SAOS2, MG63, and K7M3—revealed an IC50 ranging 1-3 µM. Subsequent investigations demonstrated significant anti-clonogenic activity and G2M phase cell cycle arrest. Annexin-PI assay showed a notable apoptotic effect of PCT, shedding light on the mode of cell death. Given the pivotal role of β-catenin signaling in human osteosarcoma pathogenesis and metastasis, targeting β-catenin components holds promise for therapeutic intervention. In silico docking studies suggested that PCT may have similar anti-cancer effect compared to β-catenin inhibitors (e.g., MSAB, ICG001). Our western blot analyses in multiple osteosarcoma cell lines demonstrated that PCT inhibits β-catenin pathway. Fluorescence microscopy and PCR analyses substantiated PCT's ability to hinder the nuclear translocation of β-catenin, providing mechanistic insights into its anti-tumor properties. Our preliminary data also suggests that AXL, an upstream regulator of β-catenin pathway, was modulated by PCT. In summary, our findings indicate that PCT exhibits therapeutic potential against osteosarcoma by targeting the β-catenin pathway. Further mechanistic studies are currently underway in our lab. Citation Format: Marina Curcic, Shreyas Gaikwad, Sanjay K Srivastava. Targeting the β-catenin signaling axis in osteosarcoma [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 7156.

Abstract 5457: Inflammatory paracrine loops established between metastasis-initiating cells and alveolar epithelium drive interactions between tumor cell subtypes that are essential for osteosarcoma lung colonization

Abstract Introduction: The development of lung metastasis drives the poor outcomes experienced by children and young adults with osteosarcoma. The mechanisms that facilitate metastatic colonization remain poorly understood. We previously determined that IL6 and CXCL8 are two osteosarcoma derived cytokines that are required for metastasis, though roles played by these cytokines have not been identified. Methods: To explore the interactions that drive cytokine expression, the role these factors play in tumor cell trafficking, and the mechanisms that facilitate metastatic niche development, we utilized transwell and co-culture systems together with a panel of metastatic osteosarcoma mouse models that allowed tumor cell manipulation via lentiviruses, CRISPR-based gene editing, and pre-clinical therapeutic evaluation approaches. Results: While metastatic osteosarcoma cells produced small amounts of IL6 and CXCL8 at baseline, lung epithelial cells markedly upregulated IL6/CXCL8 production. Ligand-receptor analysis utilizing single-cell transcriptomic data identified IL1 as an epithelial derived ligand that drives tumor IL6/CXCL8 production. Interestingly, IL6/CXCL8 production was limited to a small subset of hypo-proliferative osteosarcoma cells that have metastasis-initiating capacity. Utilizing CRISPR-mediated ablation of IL1R1 signaling within osteosarcoma cells and pharmacological inhibition with recombinant IL1R antagonist (anakinra), we elucidated that formation of pulmonary lesions in multiple mouse models of metastatic osteosarcoma required IL1 signaling. Recent work from our lab has demonstrated that osteosarcoma metastases are defined by marked phenotypic heterogeneity, though the mechanisms by which metastatic heterogeneity occurred were unclear. We hypothesized that hypo-proliferative metastasis-initiating cells may recruit circulating cells with higher proliferative capacity to establish phenotypic heterogeneity. Transwell migration assays showed that tumor cells induced the chemotactic recruitment of other tumor cells in an IL6/CXCL8-dependent manner. To test this hypothesis in vivo, we injected mice with GFP-tagged osteosarcoma cells, then injected the same mice 14 days later with RFP-labeled tumor cells from the same culture. Lungs harvested 14 days later exhibited RFP-dominant lesions surrounding a small core of GFP-labeled cells. Conclusions: Collectively, these data suggest that cytokines expressed by a subgroup of hypo-proliferative tumor cells upon interaction with lung epithelium drive the trafficking of highly proliferative circulating tumor cells into developing metastatic lesions and that disrupting these signaling networks can prevent metastatic colonization. Citation Format: Amy C. Gross, James B. Reinecke, Amanda Saraf, John Hinckley, Maren Cam, Matthew V. Cannon, Sophia Vatelle, Ryan D. Roberts. Inflammatory paracrine loops established between metastasis-initiating cells and alveolar epithelium drive interactions between tumor cell subtypes that are essential for osteosarcoma lung colonization [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 5457.

Abstract 1087: Synergistic mechanisms against pediatric bone sarcoma models: Trabectedin enhances oncolytic virotherapy intratumoral spread and antitumor immune activation

Abstract Osteosarcoma and Ewing sarcoma are the most common pediatric bone malignancies and, despite decades of research, efforts to treat patients with advanced disease remain dismal. To address this inadequacy, we leverage oncolytic herpes simplex virotherapy as a double-edged attack against tumors through 1) tumor cell-specific lysis and 2) antitumor immune stimulation. However, previous trials of oncolytic herpes simplex virotherapy in pediatric sarcomas displayed limited responses, likely due to the observed presence of immunosuppressive monocytes and macrophages. To improve efficacy, we combined oncolytic herpes simplex virotherapy with trabectedin, an FDA-approved DNA-binding agent known to disrupt gene expression and deplete monocytes and macrophages. Surprisingly, we found that the efficacy of this combination far surpassed our predictions, inducing complete and partial regressions in multiple models of Ewing sarcoma and osteosarcoma. To explore potential mechanisms driving this high degree of synergy, we performed single cell RNA sequencing on tumors of mice treated with monotherapy or combination therapy. Interestingly, trabectedin synergized with the oncolytic virotherapy through two unexpected mechanisms. Our analysis revealed that trabectedin increased intratumoral oncolytic virus spread by disrupting expression of the intrinsic antiviral response in human Ewing sarcoma cells. Additionally, trabectedin not only reduced immunosuppressive macrophages but also stimulated cytotoxic granzyme expression in infiltrating T and NK cells in immunocompetent osteosarcoma models. These effector NK and T cells were necessary for the regressions of osteosarcoma allografts treated with trabectedin and oncolytic virotherapy. Thus, trabectedin enhanced both the oncolytic effect of herpes simplex virotherapy and the effector function of cytotoxic lymphocytes that become activated in response to the virus. The combination of trabectedin and oncolytic herpes simplex virotherapy offers the potential to unite these mechanisms against bone tumors to achieve better outcomes for children. Citation Format: Emily Ringwalt, Mark Currier, Andrea Glaspell, Matthew V. Cannon, Chun-Yu Chen, Amy C. Gross, Maren Cam, Pin-Yi Wang, Ryan D. Roberts, Timothy P. Cripe. Synergistic mechanisms against pediatric bone sarcoma models: Trabectedin enhances oncolytic virotherapy intratumoral spread and antitumor immune activation [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 1087.

Abstract 5456: Identifying the role of tissue factor in osteosarcoma metastasis

Abstract Patients with osteosarcoma who develop metastasis face very poor prognoses. Even when treated with the most effective medical and surgical interventions available, about forty percent of osteosarcoma patients will eventually succumb to lung metastasis. Despite the relevance of metastasis to clinical outcomes, we understand little about the mechanisms that drive these tumor cells into the lung and facilitate their metastatic growth. Consequently, there are no approved antimetastatic agents for osteosarcoma and outcomes have not improved in more than 40 years. Tissue factor is a tightly regulated physiologic initiator of coagulation with functions in inflammation, cytokinesis, angiogenesis, apoptosis, and growth factor secretion. These functions are divided between two separate pathways: initiation of the coagulation cascade via activation of factors VII and X, and propagation of cell signaling pathways via PAR activation. It is aberrantly expressed in many cancers and has been associated with metastatic behavior and inferior outcomes by affecting metastatic vascularity, growth, and migration. Osteosarcoma has been shown to also aberrantly express tissue factor, with descriptive studies suggesting similar effects on metastatic behavior. We hypothesized that tissue factor expressed on the surface of disseminated osteosarcoma cells activates procoagulant pathways and PAR signaling, and that both facilitate pulmonary metastasis. To test this, we first established and quantified expression of tissue factor across six osteosarcoma cell lines using Western blot, flow cytometry, and confocal microscopy in both monoculture and in coculture with human bronchial epithelial cells. PAR1 and PAR2 were also discovered to be expressed in osteosarcoma cells. RNA sequencing performed suggests that both tissue factor and PAR1 expression in osteosarcoma increase over the metastatic period, as does FVII expression by alveolar macrophages; this implies that tissue factor activation during metastasis is dynamic and dependent on host interactions. Ongoing work includes functional assays of osteosarcoma tissue factor and PARs activity as well as preclinical testing of tissue factor inhibition in a murine xenograft model of osteosarcoma. To define how tissue factor propagates metastasis, we are separately inhibiting its coagulant and cell signaling pathways after murine tail vein injection using apixaban or pathway-specific antibodies. We will also use an inducible F3 knockout to alter tumor expression of tissue factor. If we find that manipulation of tissue factor expression changes metastatic behavior across cell lines, this will suggest that tissue factor plays a crucial, mechanistic role in osteosarcoma metastasis. Varying effectiveness of coagulation or signaling pathway inhibition on metastasis will implicate tissue factor’s mechanism of metastatic propagation. Citation Format: Charles C. Treinen, Amy Gross, Maren Cam, Bryce Kerlin, Ryan Roberts. Identifying the role of tissue factor in osteosarcoma metastasis [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 5456.

Abstract 5461: Antecedent STING agonist therapy improves tumor response to chemotherapy in murine models of osteosarcoma

Abstract Little improvement has been made in outcomes for pediatric patients with osteosarcoma in decades. Cytotoxic chemotherapy alone is insufficient for cure and upfront complete surgical resection is usually required to achieve long-term survival. Better systemic therapies are needed. Osteosarcoma is characterized by a high degree of genomic instability that would suggest these tumors have sufficient neoantigen burden to be immunogenic and responsive to immunotherapy, but trials of immune checkpoint inhibitors in osteosarcoma have shown poor effectiveness. Although immunotherapy drugs targeting the adaptive immune system have worked poorly, we hypothesize that an innate immune adjuvant - stimulator of interferon response cGAMP interactor 1 (STING) agonist - in combination with cytotoxic chemotherapy would improve chemotherapy effectiveness and immune-mediated tumor clearance, particularly given the abundance of innate immune cells in the microenvironment of these tumors. Using two different immune-competent in vivo murine models of osteosarcoma (K7M2 in BALB/c mice and F420 in C57BL/6 mice), we challenged mice with tumor cells via subcutaneous or intratibial injection. In all experimental replicates, we observed improved tumor regression in mice treated with intratumoral STING agonist followed by intraperitoneal treatment with carboplatin. Responses included complete tumor response in up to 40% of treated mice. Treatment with STING agonist alone or carboplatin alone only delayed tumor growth compared to untreated controls. Additionally, mice treated first with carboplatin and then with STING agonist demonstrated an initial modest response to treatment, but ultimately exhibited tumor progression, suggesting an importance to the sequence of STING agonist administration. In vitro treatment of K7M2 and F420 cells with STING agonist showed a tumor-intrinsic transient increase in expression of pro-inflammatory mediators Cxcl10, Ccl5, and Ifnb 4 hours after STING exposure. Flow cytometry analysis of K7M2 tumors demonstrated increased infiltration of STING/carboplatin-treated tumors with CD8+/IFNγ+ lymphocytes and CD11b+/MHCII+/F480+ tumor-associated macrophages. Interestingly, these tumors also demonstrated an increased quantity of CD11b+/MHCII-/F480-/Ly6Glo/Ly6C+ myeloid-derived suppressor cells despite their favorable clinical response. Our findings suggest that intratumoral STING agonist therapy stimulates tumor-intrinsic and tumor-extrinsic pro-inflammatory mediators that improve the tumor response to treatment with carboplatin. Ongoing studies are further investigating the tumor-intrinsic and extrinsic mediators that are driving this improved response to therapy. Citation Format: Erin E. Resch, Emily Kulp, Michele Doucet, Alice Recho, Brian H. Ladle. Antecedent STING agonist therapy improves tumor response to chemotherapy in murine models of osteosarcoma [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 5461.

Abstract 5516: Aberrant activation and perpetuation of lung wound response facilitates osteosarcoma metastasis

Abstract Introduction: The mechanisms that allow tumor cells to integrate with unfamiliar parenchymal cells within hostile distant tissues during metastatic colonization remain poorly defined. Nowhere are these mechanisms more important than in osteosarcoma-a pediatric bone tumor where metastases cause nearly all osteosarcoma related deaths and occur almost exclusively in the lung. The purpose of this study was to define the cellular and molecular events that facilitate osteosarcoma lung colonization to devise novel therapeutic strategies that prevent and treat metastasis. Experimental Approach: We generated experimental lung metastases using a panel of immunocompetent murine and human xenograft osteosarcoma models. A combination of immunohistochemistry, single cell RNA sequencing, and spatial transcriptomics were used to define the metastatic niche. Relevant findings were validated in human primary tumor, lung metastasis, and normal lung tissue specimens. Results: Disseminated osteosarcoma cells physically associate with alveolar epithelial cells and trigger changes in surrounding epithelial cells that are characteristic of the aberrant, non-resolving wound response seen in non-malignant lung diseases such as idiopathic pulmonary fibrosis (IPF). This process drives the accumulation of fibrotic epithelial cells and scar-associated macrophages confined within a dense fibronectin-based matrix. Anti-fibrotic tyrosine kinase inhibitors used to treat patients with IPF (nintedanib) prevent the observed fibrogenic changes and inhibit metastatic colonization. Epithelial-osteosarcoma paracrine signaling is dominated by an inflammatory cytokine milieu that facilitates this transition towards fibrosis. Blocking one of the dominant paracrine signals with a recombinant IL1 receptor antagonist (anakinra) has similar effects on both fibrosis and metastatic colonization. Conclusions: Our study demonstrates that tumor interactions with host stromal cells are critical for metastasis. Metastatic colonization requires transformation of the local lung microenvironment into a fibrotic, non-resolving, cytokine-rich, wound-like state that is both provoked and sustained by tumor-epithelial interactions. These insights have identified several potential therapeutic approaches to prevent metastatic colonization and treat established metastases. Citation Format: James Brandon Reinecke, Amy C. Gross, Maren Cam, Leyre Jimenez Garcia, Matthew V. Cannon, Ryan D. Roberts. Aberrant activation and perpetuation of lung wound response facilitates osteosarcoma metastasis [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 5516.

Abstract 148: Multiomic sequencing reveals diversity in clonal landscape and genomic alterations in a lung metastatic PDX osteosarcoma model

Abstract Introduction: Osteosarcoma is a primary malignant bone tumor characterized by the production of spindle cells resulting in immature bone formation. The lung is the most frequent site of metastatic disease and relapse occurs in more than 30 % of patients. Recent results show that relapse is due to a subset of cells with different phenotypic and genetic signatures conferring advantage to drive progression and drug resistance within the intra-tumorally heterogeneous population. Thus, developing a defined in vivo model that can identify the rare genetic subpopulation and recapitulate clonal evolution is crucial. In this study, we used whole exome, barcode and RNA sequencing to characterize the landscape of genomic alterations and also track and identify the clonal subpopulations, clonal and genetic drivers of lungs metastasis. Methods: We injected barcoded PDX (OS17) cells intravenously in ten SCID mice to track the clonal subpopulation of cells that metastasize to the lungs. Metastasized lung nodules were collected following death or euthanasia. All samples collected were snap frozen in liquid nitrogen and stored at -80°C. DNA and RNA was extracted and analyzed by PCR, NGS, WES and RNA sequencing to map clonality, mutational and evolutionary profiles. Results: Four (40%) of the mice developed lung metastases with three mice having multiple metastatic lung nodules. Surgery to remove the metastatic nodules was performed 216 ± 55.5 days following tumor cell injection. Nine metastatic lung nodules from three mice were used for sequencing and analysis. A Shannon-Weaver and Jaccard similarity index show a diversity in clonal architecture between the lung nodules. A total of 15,394 somatic variants was identified including 12,547 single nucleotide variants (SNV), 4054 synonymous, 2662 missense, 28 nonsense mutations and 1639 somatic indels. The SNVs accounted for 81% of all variants followed by CNV 11 % and indels 8% respectively. Synonymous and missense mutations were the most frequently observed in all samples. Copy number loss was two-fold compared to copy number gain across all tumors. Furthermore, the deletions span longer genomic distances compared to amplifications. The mutational spectrum showed that the highest substitutions were C>T/G>A followed by T>C/A>G; the least substitutions were T>A/A>T. Also, we identified a large set of genes with genomic aberrations. These include amplifications in VEGF, RB1, RUNX, PARP4, ICAM3, EGFR, BRCA2, COLA6A1, COLA6A2, CCND3, CDKN2D etc. Conclusions: In the current model, we identified multiple tumorigenic seeding clones and the diverse set of genes mutated in osteosarcoma. Further analysis of the mutational signature resulted in the identification of potential genes that act as drivers in the lung metastatic process. Acknowledgments: Swim Across America, the Foster Foundation and the Barbara Epstein Foundation. Citation Format: Sylvester Jusu, Wendong Zhang, Zhongting Zhang, Xu Zhaohui, Sankaranarayanan Kannan, Yifei Wang, Zhou Xin, Yi Yanhua, Michael Roth, Jonathan Gill, Richard Gorlick. Multiomic sequencing reveals diversity in clonal landscape and genomic alterations in a lung metastatic PDX osteosarcoma 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 148.

Identifying immune-related prognostic biomarkers in osteosarcoma: Development and validation of the tumor immune microenvironment risk model based on analysis of TCGA.

Osteosarcoma is a rare and aggressive malignancy with limited effective therapeutic options. This study aimed to identify immune-related prognostic biomarkers and develop a prognostic model for osteosarcoma. We performed integrated analysis of transcriptomic data and immune cell infiltration profiles of 84 osteosarcoma samples from the Cancer Genome Atlas (TCGA) database. Time-dependent receiver operating characteristic (ROC) curve analysis was used to assess the prognostic value of the TIMErisk model. We also performed functional annotation and pathway enrichment analyses to explore the potential mechanisms underlying the TIMErisk model. We identified a seven-gene TIMErisk model (C2, APBB1IP, BST2, TRPV2, CCL5, GBP1, and F13A1) that was independently associated with overall survival of osteosarcoma patients. The TIMErisk model showed significant associations with immune cell infiltration and immunosuppressive gene expression. In addition, the TIMErisk model was associated with drug sensitivity, and we found that several immune checkpoint genes were significantly differentially expressed between high- and low-TIMErisk groups. Functional annotation and pathway enrichment analyses revealed that the TIMErisk model was associated with multiple immune-related pathways, including antigen processing and presentation, cytokine-cytokine receptor interaction, and T cell receptor signaling pathway. Our study identified a novel TIME-based prognostic model for osteosarcoma that incorporates immune-related genes and can be used to predict patient prognosis and response to immunotherapy. Our findings highlight the importance of the TIME microenvironment in osteosarcoma progression and suggest that immune-related biomarkers may have clinical significance in the management of osteosarcoma.

Promising Dual Anticancer and Antimetastatic Action by a Cu(II) Complex Derived from Acylhydrazone on Human Osteosarcoma Models.

Osteosarcoma cancers are becoming more common in children and young adults, and existing treatments have low efficacy and a very high mortality rate, making it pressing to search for new chemotherapies with high efficacy and high selectivity index. Copper complexes have shown promise in the treatment of osteosarcoma. Here, we report the synthesis, characterization, and anticancer activity of [Cu(N-N-Fur)(NO3)(H2O)] complex where N-N-Fur is (E)-N'-(2-hydroxy-3-methoxybenzylidene)furan-2-carbohydrazide. The [Cu(N-N-Fur)(NO3)(H2O)] complex was characterized via X-ray diffraction and electron spin resonance (ESR), displaying a copper center in a nearly squared pyramid environment with the nitrate ligand acting as a fifth ligand in the coordination sphere. We observed that [Cu(N-N-Fur)(NO3)(H2O)] binds to DNA in an intercalative manner. Anticancer activity on the MG-63 cell line was evaluated in osteosarcoma monolayer (IC50 2D: 1.1 ± 0.1 μM) and spheroids (IC50 3D: 16.3 ± 3.1 μM). Selectivity assays using nontumoral fibroblast (L929 cell line) showed that [Cu(N-N-Fur)(NO3)(H2O)] has selectivity index value of 2.3 compared to cis-diamminedichloroplatinum(II) (CDDP) (SI = 0.3). Additionally, flow cytometry studies demonstrated that [Cu(N-N-Fur)(NO3)(H2O)] inhibits cell proliferation and conveys cells to apoptosis. Cell viability studies of MG-63 spheroids (IC50 = 16.3 ± 3.1 μM) showed that its IC50 value is 4 times lower than for CDDP (IC50 = 65 ± 6 μM). Besides, we found that cell death events mainly occurred in the center region of the spheroids, indicating efficient transport to the microtumor. Lastly, the complex showed dose-dependent reductions in spheroid cell migration from 7.5 to 20 μM, indicating both anticancer and antimetastatic effects.

Split Gp41-1 intein splicing as a model to evaluate the cellular location of the oncosuppressor Maspin in an in vitro model of osteosarcoma.

Inteins are proteins involved in the protein splicing mechanism, an autoprocessing event, where sequences (exteins) separated by inteins become ligated each other after recombination. Two kinds of inteins have been described, contiguous inteins and split inteins. The former ones are transcribed and translated as a single peptide along with their exteins, while the latter are fragmented between two different genes and are transcribed and translated separately. The aim of this study is to establish a method to obtain a fluorescent eukaryotic protein to analyze its cellular localization, using the natural split gp41-1 inteins. We chose natural split inteins due to their distribution in all three domains of life. Two constructs were prepared, one containing the N-terminal split intein along with the N-moiety of the Red Fluorescent Protein (RFP) and a second construct containing the C-terminal of split intein, the C-moiety of RFP and the gene coding for Maspin, a tumor suppressor protein. The trans-splicing was verified by transfecting both N-terminal and C-terminal constructs into mammalian cells. The success of the recombination event was highlighted through the fluorescence produced by reconstituted RFP after recombination, along with the overlap of the red fluorescence produced by recombined RFP and the green fluorescence produced by the hybridization of the recombinant Maspin with a specific antibody. In conclusion, we opted to use this mechanism of recombination to obtain a fluorescent Maspin instead to express a large fusion protein, considering that it could interfere with Maspin's structure and function.