Characterization of the metastatic phenotype of a panel of established osteosarcoma cells

Osteosarcoma cell-derived CCL2 facilitates lung metastasis via accumulation of tumor-associated macrophages

Osteosarcoma (OS) is the most common malignant tumor of bone in children and adolescents. Although lung metastasis is a major obstacle to improving the prognosis of OS patients, the underlying mechanism of lung metastasis of OS is poorly understood. Tumor-associated macrophages (TAMs) with M2-like characteristics are reportedly associated with lung metastasis and poor prognosis in OS patients. In this study, we investigated the metastasis-associated tumor microenvironment (TME) in orthotopic OS tumor models with non-metastatic and metastatic OS cells. Non-metastatic and metastatic tumor cells derived from mouse OS (Dunn and LM8) and human OS (HOS and 143B) were used to analyze the TME associated with lung metastasis in orthotopic OS tumor models. OS cell-derived secretion factors were identified by cytokine array and enzyme-linked immunosorbent assay (ELISA). Orthotopic tumor models with metastatic LM8 and 143B cells were analyzed to evaluate the therapeutic potential of a neutralizing antibody in the development of primary and metastatic tumors. Metastatic OS cells developed metastatic tumors with infiltration of M2-like TAMs in the lungs. Cytokine array and ELISA demonstrated that metastatic mouse and human OS cells commonly secreted CCL2, which was partially encapsulated in extracellular vesicles. In vivo experiments demonstrated that while primary tumor growth was unaffected, administration of CCL2-neutralizing antibody led to a significant suppression of lung metastasis and infiltration of M2-like TAMs in the lung tissue. Our results suggest that CCL2 plays a crucial role in promoting the lung metastasis of OS cells via accumulation of M2-like TAMs.

Immunotherapy-related cognitive impairment after CAR T cell therapy in mice

Immunotherapies have revolutionized cancer care for many tumor types, but their potential long-term cognitive impacts are incompletely understood. Here, we demonstrated in mouse models that chimeric antigen receptor (CAR) T cell therapy for both central nervous system (CNS) and non-CNS cancers impaired cognitive function and induced a persistent CNS immune response characterized by white matter microglial reactivity, microglial chemokine expression, and elevated cerebrospinal fluid (CSF) cytokines and chemokines. Consequently, oligodendroglial homeostasis and hippocampal neurogenesis were disrupted. Single-nucleus sequencing studies of human frontal lobe from patients with or without previous CAR T cell therapy for brainstem tumors confirmed reactive states of microglia and oligodendrocytes following treatment. In mice, transient microglial depletion or CCR3 chemokine receptor blockade rescued oligodendroglial deficits and cognitive performance in a behavioral test of attention and short-term memory function following CAR T cell therapy. Taken together, these findings illustrate targetable neural-immune mechanisms underlying immunotherapy-related cognitive impairment.

Macrophage and osteosarcoma cell crosstalk is dependent on oxygen tension and 3D culture

Osteosarcoma (OS), the most common form of primary bone cancer in young adults, has had no improvements in clinical outcomes in 50 years. This highlights a critical need to advance mechanistic understanding of OS to further therapeutic discovery, which will only be possible with accurate models of the disease. Compared to traditional monolayer studies and preclinical models, in vitro models that better replicate the three-dimensional (3D) bone marrow microenvironment will facilitate methodical investigations of the events and factors that drive OS progression. Herein, we use fibrin-alginate interpenetrating network (FA IPN) hydrogels to model the hematological bone marrow environment. We interrogated the effects of oxygen tension, 3D culture, and macrophage phenotype on OS behavior and specifically examine the immunomodulatory crosstalk between OS and macrophages. We observe that OS is more sensitive to oxygen tension when cultured in 3D. Specifically, both highly and less metastatic OS exhibit decreased changes in DNA content over time in 3D, but then demonstrate diverging behaviors in heterotypic culture with macrophages. OS response to macrophages differs as a function of metastatic potential, where highly metastatic OS shows increased immunosuppression that varies with oxygen tension but relies on direct coculture conditions. To our knowledge, this is among the first work to report the effects of 3D culture on the interplay between OS and macrophages in a coculture microenvironment. Together, these data introduce FA IPNs as a promising platform for cancer research and emphasize the importance of novel models for the mechanistic study of OS.

Expanding on roles of pleckstrin homology-like domain family A member 1 protein

Pleckstrin homology-like domain, family A, member 1 (PHLDA1), one of the three members of PHLDA (1-3) family, has been reported to be expressed in mammalian cells and tissues and play diverse roles in various biological processes such as apoptosis, pyroptosis, and differentiation. Nevertheless, new roles and mechanisms of PHLDA1 action have come to light, with some needing further clarification. The major aim of the publication is to review proapoptotic or antiapoptotic roles of PHLDA1 in cancer, including ample evidence on PHLDA1 role as a tumor suppressor gene or oncogene and its influence on tumor progression. The role of PHLDA1 as a prognostic marker of cancer emerges, as well as its role in drug response and resistance. PHLDA1 involvement in autophagy, endoplasmic reticulum stress, pyroptosis, or differentiation is also scrutinized. It is also important to note that the association of PHLDA1 with miRNA regulation is described. Additionally, the emerging functions of PHLDA1 are indicated, specifically in inflammation and ischemia/reperfusion injury.

Whole-Exome Analysis and Osteosarcoma: A Game Still Open

Osteosarcoma (OS) is the most prevalent malignant bone tumor in adolescents and young adults. OS cells grow in a permissive local microenvironment which modulates their behavior and facilitates all steps in tumor development (e.g., proliferation/quiescence, invasion/migration, and drug resistance) and contributes to their intrinsic heterogeneity. The lung parenchyma is the most common metastatic site in OS, and metastatic foci are frequently associated with a poor clinical outcome. Although multiple factors may be responsible for the disease, including genetic mutations (e.g., Rb and p53), the molecular mechanism of development of OS remains unclear, and the conventional treatment for OS is still based on a sequential approach that combines chemotherapy and surgery. Also, despite the increase in clinical trials, the survival rates for OS have not improved. Non-specific targeting therapies thus show poor therapeutic effects, along with side effects at high doses. For these reasons, many efforts have been made to characterize the complex genome of OS thanks to the whole-exome analysis, with the aim of identifying predictive biomarkers to give these patients a better therapeutic option. This review aims to summarize and discuss the main recent advances in OS molecular research for precision medicine.

Pharmacologic Inhibition of EIF4A Blocks NRF2 Synthesis to Prevent Osteosarcoma Metastasis

PURPOSE

Effective therapies for metastatic osteosarcoma (OS) remain a critical unmet need. Targeting mRNA translation in metastatic OS offers a promising option, as selective translation drives the synthesis of cytoprotective proteins under harsh microenvironmental conditions to facilitate metastatic competence.

EXPERIMENTAL DESIGN

We assessed the expression levels of eukaryotic translation factors in OS, revealing the high expression of the eukaryotic initiation factor 4A1 (EIF4A1). Using a panel of metastatic OS cell lines and patient-derived xenograft (PDX) models, EIF4A1 inhibitors were evaluated for their ability to block proliferation and reduce survival under oxidative stress, mimicking harsh conditions of the lung microenvironment. Inhibitors were also evaluated for their antimetastatic activity using the ex vivo pulmonary metastasis assay and in vivo metastasis models. Proteomics was performed to catalog which cytoprotective proteins or pathways were affected by EIF4A1 inhibition.

RESULTS

CR-1-31B, a rocaglate-based EIF4A1 inhibitor, exhibited nanomolar cytotoxicity against all metastatic OS models tested. CR-1-31B exacerbated oxidative stress and apoptosis when OS cells were co-treated with tert-butylhydroquinone, a chemical oxidative stress inducer. CR-1-31B potently inhibited OS growth in the pulmonary metastasis assay model and in experimental and spontaneous models of OS lung metastasis. Proteomic analysis revealed that tert-butylhydroquinone-mediated upregulation of the NRF2 antioxidant factor was blocked by co-treatment with CR-1-31B. Genetic inactivation of NRF2 phenocopied the antimetastatic activity of CR-1-31B. Finally, the clinical-grade EIF4A1 phase-1-to-2 inhibitor, zotatifin, similarly blocked NRF2 synthesis and the OS metastatic phenotype.

CONCLUSIONS

Collectively, our data reveal that pharmacologic targeting of EIF4A1 is highly effective in blocking OS metastasis by blunting the NRF2 antioxidant response.

IRF5 suppresses metastasis through the regulation of tumor-derived extracellular vesicles and pre-metastatic niche formation

Metastasis is driven by extensive cooperation between a tumor and its microenvironment, resulting in the adaptation of molecular mechanisms that evade the immune system and enable pre-metastatic niche (PMN) formation. Little is known of the tumor-intrinsic factors that regulate these mechanisms. Here we show that expression of the transcription factor interferon regulatory factor 5 (IRF5) in osteosarcoma (OS) and breast carcinoma (BC) clinically correlates with prolonged survival and decreased secretion of tumor-derived extracellular vesicles (t-dEVs). Conversely, loss of intra-tumoral IRF5 establishes a PMN that supports metastasis. Mechanistically, IRF5-positive tumor cells retain IRF5 transcripts within t-dEVs that contribute to altered composition, secretion, and trafficking of t-dEVs to sites of metastasis. Upon whole-body pre-conditioning with t-dEVs from IRF5-high or -low OS and BC cells, we found increased lung metastatic colonization that replicated findings from orthotopically implanted cancer cells. Collectively, our findings uncover a new role for IRF5 in cancer metastasis through its regulation of t-dEV programming of the PMN.

Comparative responses to demethylating therapy in animal models of osteosarcoma

Background

The demethylating agent decitabine (DAC) effectively inhibits tumor growth and metastasis by targeting ESR1 methylation to restore estrogen receptor alpha (ERα) signaling and promoting cellular differentiation in models of human osteosarcoma (OSA). Whether this pathway can be targeted in canine OSA patients is unknown.

Methods

Canine OSA tumor samples were tested for ERα expression and ESR1 promoter methylation. Human (MG63.3) and canine (MC-KOS) OSA cell lines and murine xenografts were treated with DAC in vitro and in vivo, respectively. Samples were assessed using mRNA sequencing and tissue immunohistochemistry.

Results

ESR1 is methylated in a subset of canine OSA patient samples and the MC-KOS cell line. DAC treatment led to enhanced differentiation as demonstrated by increased ALPL expression, and suppressed tumor growth in vitro and in vivo. Metastatic progression was inhibited, particularly in the MG63.3 model, which expresses higher levels of DNA methyltransferases DNMT1 and 3B. DAC treatment induced significant alterations in immune response and cell cycle pathways.

Conclusion

DAC treatment activates ERα signaling, promotes bone differentiation, and inhibits tumor growth and metastasis in human and canine OSA. Additional DAC-altered pathways and species- or individual-specific differences in DNMT expression may also play a role in DAC treatment of OSA.

Multiomics Analysis of the PHLDA Gene Family in Different Cancers and Their Clinical Prognostic Value

The PHLDA (pleckstrin homology-like domain family) gene family is popularly known as a potential biomarker for cancer identification, and members of the PHLDA family have become considered potentially viable targets for cancer treatments. The PHLDA gene family consists of PHLDA1, PHLDA2, and PHLDA3. The predictive significance of PHLDA genes in cancer remains unclear. To determine the role of pleckstrin as a prognostic biomarker in human cancers, we conducted a systematic multiomics investigation. Through various survival analyses, pleckstrin expression was evaluated, and their predictive significance in human tumors was discovered using a variety of online platforms. By analyzing the protein-protein interactions, we also chose a collection of well-known functional protein partners for pleckstrin. Investigations were also carried out on the relationship between pleckstrins and other cancers regarding mutations and copy number alterations. The cumulative impact of pleckstrin and their associated genes on various cancers, Gene Ontology (GO), and pathway analyses were used for their evaluation. Thus, the expression profiles of PHLDA family members and their prognosis in various cancers may be revealed by this study. During this multiomics analysis, we found that among the PHLDA family, PHLDA1 may be a therapeutic target for several cancers, including kidney, colon, and brain cancer, while PHLDA2 can be a therapeutic target for cancers of the colon, esophagus, and pancreas. Additionally, PHLDA3 may be a useful therapeutic target for ovarian, renal, and gastric cancer.

Development of an Optical System for Strain Drop Measurement of Osteosarcoma Cells on Substrates with Different Stiffness

Adherent cells perceive mechanical feedback from the underlying matrix and convert it into biochemical signals through a process known as mechanotransduction. The response to changes in the microenvironment relies on the cell's mechanical properties, including elasticity, which was recently identified as a biomarker for various diseases. Here, we propose the design, development, and characterization of a new system for the measurement of adherent cells' strain drop, a parameter correlated with cells' elasticity. To consider the interplay between adherent cells and the host extracellular matrix, cell stretching was combined with adhesion on substrates with different stiffnesses. The technique is based on the linear stretching of silicone chambers, high-speed image acquisition, and feedback for image centering. The system was characterized in terms of the strain homogeneity, impact of collagen coating, centering capability, and sensitivity. Subsequently, it was employed to measure the strain drop of two osteosarcoma cell lines, low-aggressive osteoblast-like SaOS-2 and high-aggressive 143B, cultured on two different substrates to recall the stiffness of the bone and lung extracellular matrices. Results demonstrated good substrate homogeneity, a negligible effect of the collagen coating, and an accurate image centering. Finally, the experimental results showed an average strain drop that was lower in the 143B cells in comparison with the SaOS-2 cells in all the tested conditions.

Immunotherapy-related cognitive impairment after CAR T cell therapy in mice

Persistent central nervous system (CNS) immune dysregulation and consequent dysfunction of multiple neural cell types is central to the neurobiological underpinnings of a cognitive impairment syndrome that can occur following traditional cancer therapies or certain infections. Immunotherapies have revolutionized cancer care for many tumor types, but the potential long-term cognitive sequelae are incompletely understood. Here, we demonstrate in mouse models that chimeric antigen receptor (CAR) T cell therapy for both CNS and non-CNS cancers can impair cognitive function and induce a persistent CNS immune response characterized by white matter microglial reactivity and elevated cerebrospinal fluid (CSF) cytokines and chemokines. Consequently, oligodendroglial homeostasis and hippocampal neurogenesis are disrupted. Microglial depletion rescues oligodendroglial deficits and cognitive performance in a behavioral test of attention and short-term memory function. Taken together, these findings illustrate similar mechanisms underlying immunotherapy-related cognitive impairment (IRCI) and cognitive impairment following traditional cancer therapies and other immune challenges.

Osteosarcoma PDX-Derived Cell Line Models for Preclinical Drug Evaluation Demonstrate Metastasis Inhibition by Dinaciclib through a Genome-Targeted Approach

PURPOSE

Models to study metastatic disease in rare cancers are needed to advance preclinical therapeutics and to gain insight into disease biology. Osteosarcoma is a rare cancer with a complex genomic landscape in which outcomes for patients with metastatic disease are poor. As osteosarcoma genomes are highly heterogeneous, multiple models are needed to fully elucidate key aspects of disease biology and to recapitulate clinically relevant phenotypes.

EXPERIMENTAL DESIGN

Matched patient samples, patient-derived xenografts (PDX), and PDX-derived cell lines were comprehensively evaluated using whole-genome sequencing and RNA sequencing. The in vivo metastatic phenotype of the PDX-derived cell lines was characterized in both an intravenous and an orthotopic murine model. As a proof-of-concept study, we tested the preclinical effectiveness of a cyclin-dependent kinase inhibitor on the growth of metastatic tumors in an orthotopic amputation model.

RESULTS

PDXs and PDX-derived cell lines largely maintained the expression profiles of the patient from which they were derived despite the emergence of whole-genome duplication in a subset of cell lines. The cell lines were heterogeneous in their metastatic capacity, and heterogeneous tissue tropism was observed in both intravenous and orthotopic models. Single-agent dinaciclib was effective at dramatically reducing the metastatic burden.

CONCLUSIONS

The variation in metastasis predilection sites between osteosarcoma PDX-derived cell lines demonstrates their ability to recapitulate the spectrum of the disease observed in patients. We describe here a panel of new osteosarcoma PDX-derived cell lines that we believe will be of wide use to the osteosarcoma research community.

A novel patient-derived immortalised cell line of myxofibrosarcoma: a tool for preclinical drugs testing and the generation of near-patient models

BACKGROUND

Myxofibrosarcoma is a rare malignant soft tissue sarcoma characterised by multiple local recurrence and can become of higher grade with each recurrence. Consequently, myxofibrosarcoma represents a burden for patients, a challenge for clinicians, and an interesting disease to study tumour progression. Currently, few myxofibrosarcoma preclinical models are available.

METHODS

In this paper, we present a spontaneously immortalised myxofibrosarcoma patient-derived cell line (MF-R 3). We performed phenotypic characterization through multiple biological assays and analyses: proliferation, clonogenic potential, anchorage-independent growth and colony formation, migration, invasion, AgNOR staining, and ultrastructural evaluation.

RESULTS

MF-R 3 cells match morphologic and phenotypic characteristics of the original tumour as 2D cultures, 3D aggregates, and on the chorioallantoic membrane of chick embryos. Overall results show a clear neoplastic potential of this cell line. Finally, we tested MF-R 3 sensitivity to anthracyclines in 2D and 3D conditions finding a good response to these drugs.

CONCLUSIONS

In conclusion, we established a novel patient-derived myxofibrosarcoma cell line that, together with the few others available, could serve as an important model for studying the molecular pathogenesis of myxofibrosarcoma and for testing new drugs and therapeutic strategies in diverse experimental settings.

Unveiling the role of osteosarcoma-derived secretome in premetastatic lung remodelling

BACKGROUND

Lung metastasis is the most adverse clinical factor and remains the leading cause of osteosarcoma-related death. Deciphering the mechanisms driving metastatic spread is crucial for finding open therapeutic windows for successful organ-specific interventions that may halt or prevent lung metastasis.

METHODS

We employed a mouse premetastatic lung-based multi-omics integrative approach combined with clinical features to uncover the specific changes that precede lung metastasis formation and identify novel molecular targets and biomarker of clinical utility that enable the design of novel therapeutic strategies.

RESULTS

We found that osteosarcoma-bearing mice or those preconditioned with the osteosarcoma cell secretome harbour profound lung structural alterations with airway damage, inflammation, neutrophil infiltration, and extracellular matrix remodelling with increased deposition of fibronectin and collagens by resident stromal activated fibroblasts, favouring the adhesion of disseminated tumour cells. Systemic-induced microenvironmental changes, supported by transcriptomic and histological data, promoted and accelerated lung metastasis formation. Comparative proteome profiling of the cell secretome and mouse plasma identified a large number of proteins involved in extracellular-matrix organization, cell-matrix adhesion, neutrophil degranulation, and cytokine-mediated signalling, consistent with the observed lung microenvironmental changes. Moreover, we identified EFEMP1, an extracellular matrix glycoprotein exclusively secreted by metastatic cells, in the plasma of mice bearing a primary tumour and in biopsy specimens from osteosarcoma patients with poorer overall survival. Depletion of EFEMP1 from the secretome prevents the formation of lung metastasis.

CONCLUSIONS

Integration of our data uncovers neutrophil infiltration and the functional contribution of stromal-activated fibroblasts in ECM remodelling for tumour cell attachment as early pro-metastatic events, which may hold therapeutic potential in preventing or slowing the metastatic spread. Moreover, we identified EFEMP1, a secreted glycoprotein, as a metastatic driver and a potential candidate prognostic biomarker for lung metastasis in osteosarcoma patients. Osteosarcoma-derived secreted factors systemically reprogrammed the lung microenvironment and fostered a growth-permissive niche for incoming disseminated cells to survive and outgrow into overt metastasis. Daily administration of osteosarcoma cell secretome mimics the systemic release of tumour-secreted factors of a growing tumour in mice during PMN formation; Transcriptomic and histological analysis of premetastatic lungs revealed inflammatory-induced stromal fibroblast activation, neutrophil infiltration, and ECM remodelling as early onset pro-metastatic events; Proteome profiling identified EFEMP1, an extracellular secreted glycoprotein, as a potential predictive biomarker for lung metastasis and poor prognosis in osteosarcoma patients. Osteosarcoma patients with EFEMP1 expressing biopsies have a poorer overall survival.

Temporal chromatin accessibility changes define transcriptional states essential for osteosarcoma metastasis

The metastasis-invasion cascade describes the series of steps required for a cancer cell to successfully spread from its primary tumor and ultimately grow within a secondary organ. Despite metastasis being a dynamic, multistep process, most omics studies to date have focused on comparing primary tumors to the metastatic deposits that define end-stage disease. This static approach means we lack information about the genomic and epigenomic changes that occur during the majority of tumor progression. One particularly understudied phase of tumor progression is metastatic colonization, during which cells must adapt to the new microenvironment of the secondary organ. Through temporal profiling of chromatin accessibility and gene expression in vivo, we identify dynamic changes in the epigenome that occur as osteosarcoma tumors form and grow within the lung microenvironment. Furthermore, we show through paired in vivo and in vitro CRISPR drop-out screens and pharmacological validation that the upstream transcription factors represent a class of metastasis-specific dependency genes. While current models depict lung colonization as a discrete step within the metastatic cascade, our study shows it is a defined trajectory through multiple epigenetic states, revealing new therapeutic opportunities undetectable with standard approaches.

Engineered bone marrow as a clinically relevant ex vivo model for primary bone cancer research and drug screening

Osteosarcoma (OS) is the most common primary malignant bone cancer in children and adolescents. While numerous other cancers now have promising therapeutic advances, treatment options for OS have remained unchanged since the advent of standard chemotherapeutics and offer less than a 25% 5-y survival rate for those with metastatic disease. This dearth of clinical progress underscores a lack of understanding of OS progression and necessitates the study of this disease in an innovative system. Here, we adapt a previously described engineered bone marrow (eBM) construct for use as a three-dimensional platform to study how microenvironmental and immune factors affect OS tumor progression. We form eBM by implanting acellular bone-forming materials in mice and explanting the cellularized constructs after 8 wk for study. We interrogate the influence of the anatomical implantation site on eBM tissue quality, test ex vivo stability under normoxic (5% O2) and standard (21% O2) culture conditions, culture OS cells within these constructs, and compare them to human OS samples. We show that eBM stably recapitulates the composition of native bone marrow. OS cells exhibit differential behavior dependent on metastatic potential when cultured in eBM, thus mimicking in vivo conditions. Furthermore, we highlight the clinical applicability of eBM as a drug-screening platform through doxorubicin treatment and show that eBM confers a protective effect on OS cells that parallel clinical responses. Combined, this work presents eBM as a cellular construct that mimics the complex bone marrow environment that is useful for mechanistic bone cancer research and drug screening.

Determination of a Measurement Procedure for the Study of Cells' Dielectric Properties through Descriptive Statistic

This paper presents a measurement procedure for analyzing the dielectric properties of cells using descriptive statistics. The study focuses on four cancer cell lines (MDA-MB-231 and MCF-7 breast cancer, SaOS-2, and 143B osteosarcoma) and DMEM culture medium, utilizing the Lorentzian fit model of the return-loss function. The measurements are performed using a circular patch resonator with a 40 mm diameter, powered by a miniVNA operating in the frequency range of 1 MHz to 3 GHz. Eight specimens are prepared for each group to ensure reliability, and the return loss is recorded ten times for each specimen. Various statistical parameters are calculated and evaluated, including the average value, standard deviation, coefficient of variation, and relative error between the average and the first values. The results demonstrate that one single acquisition highly represents the entire set of ten data points, especially for the resonant frequency, with an accuracy error lower than 0.05%. These findings have significant implications for the methodological approach to detecting cells' dielectric properties, as they substantially reduce time and preserve the specimens without compromising the accuracy of the experimental results.

SOX9 is a key component of RUNX2-regulated transcriptional circuitry in osteosarcoma

BACKGROUND

The absence of prominent, actionable genetic alternations in osteosarcomas (OS) implies that transcriptional and epigenetic mechanisms significantly contribute to the progression of this life-threatening form of cancer. Therefore, the identification of potential transcriptional events that promote the survival of OS cells could be key in devising targeted therapeutic approaches for OS. We have previously shown that RUNX2 is a transcription factor (TF) essential for OS cell survival. Unfortunately, the transcriptional network or circuitry regulated by RUNX2 in OS cells is still largely unknown.

METHODS

The TFs that are in the RUNX2 transcriptional circuitry were identified by analyzing RNAseq and ChIPseq datasets of RUNX2. To evaluate the effect of SOX9 knockdown on the survival of osteosarcoma cells in vitro, we employed cleaved caspase-3 immunoblotting and propidium iodide staining techniques. The impact of SOX9 and JMJD1C depletion on OS tumor growth was examined in vivo using xenografts and immunohistochemistry. Downstream targets of SOX9 were identified and dissected using RNAseq, pathway analysis, and gene set enrichment analysis. Furthermore, the interactome of SOX9 was identified using BioID and validated by PLA.

RESULT

Our findings demonstrate that SOX9 is a critical TF that is induced by RUNX2. Both in vitro and in vivo experiments revealed that SOX9 plays a pivotal role in the survival of OS. RNAseq analysis revealed that SOX9 activates the transcription of MYC, a downstream target of RUNX2. Mechanistically, our results suggest a transcriptional network involving SOX9, RUNX2, and MYC, with SOX9 binding to RUNX2. Moreover, we discovered that JMJD1C, a chromatin factor, is a novel binding partner of SOX9, and depletion of JMJD1C impairs OS tumor growth.

CONCLUSION

The findings of this study represent a significant advancement in our understanding of the transcriptional network present in OS cells, providing valuable insights that may contribute to the development of targeted therapies for OS.

Indoleamine 2,3-dioxygenase 1 promotes osteosarcoma progression by regulating tumor-derived exosomal miRNA hsa-miR-23a-3p

Background: Osteosarcoma (OS) is the most common primary malignant tumor originating in bone. Immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) participates in tumor immune tolerance and promotes tumor progression, while the study of IDO1 in OS is limited. Methods: Immunohistochemistry analysis was performed to test the expression of IDO1 and Ki67. The relationship between IDO1 or Ki67 positive count and clinical stage of the patient was analyzed. Laboratory test indexes including serum alkaline phosphatase (ALP), lactate dehydrogenase (LDH), white blood cell (WBC) count and C-reactive protein (CRP) at diagnosis of OS patients were collected. The relationship between positive count of IDO1 and Ki67 or laboratory test indexes was analyzed by Pearson's correlation analysis. IDO1 stably overexpressed cell lines of these cells (MG63 OE, 143B OE and hFOB1.19 OE) were constructed and validated by Western blot and Elisa. Exosomes were isolated from conditioned culture media of these cells and were identified by Zetaview nanoparticle tracking analyzer. Next-generation sequencing was conducted to identify miRNAs enriched in exosomes. Differentially expressed miRNAs (DE miRNAs) were verified in clinical samples and cell lines by qPCR. Biological processes and cell components analysis of DE miRNAs was conducted by GO enrichment analysis using the protein interaction network database. Results: Immunosuppressive enzyme IDO1 was highly expressed in tumor tissues. 66.7% (6/9) of the tissues showed moderately or strongly positive immunostaining signal of IDO1, and 33.3% (3/9) were weakly positive. The expression of IDO1 was positively related to Ki67 and associated with prognostic-related clinical features of OS patients. Overexpression of IDO1 significantly affected the exosome-derived miRNA subsets from MG63, 143B and hFOB1.19 cells. A total of 1244 DE miRNAs were identified, and hsa-miR-23a-3p was further screened as key DE miRNA involved in the progression of OS. GO analysis of target genes of the DE miRNA results showed that target enrichment in the functions of immune regulation and tumor progression. Discussion: Our results indicate that IDO1 has the potential to promote the progression of OS that is related to miRNAs mediated tumor immunity. Targeting IDO1-mediated hsa-miR-23a-3p may be a potential therapeutic strategy for OS treatment.

Isolation and Characterization of Novel Canine Osteosarcoma Cell Lines from Chemotherapy-Naïve Patients

The present study aimed to establish novel canine osteosarcoma cell lines (COS3600, COS3600B, COS4074) and characterize the recently described COS4288 cells. The established D-17 cell line served as a reference. Analyzed cell lines differed notably in their biological characteristics. Calculated doubling times were between 22 h for COS3600B and 426 h for COS4074 cells. COS3600B and COS4288 cells produced visible colonies after anchorage-independent growth in soft agar. COS4288 cells were identified as cells with the highest migratory capacity. All cells displayed the ability to invade through an artificial basement membrane matrix. Immunohistochemical analyses revealed the mesenchymal origin of all COS cell lines as well as positive staining for the osteosarcoma-relevant proteins alkaline phosphatase and karyopherin α2. Expression of p53 was confirmed in all tested cell lines. Gene expression analyses of selected genes linked to cellular immune checkpoints (CD270, CD274, CD276), kinase activity (MET, ERBB2), and metastatic potential (MMP-2, MMP-9) as well as selected long non-coding RNA (MALAT1) and microRNAs (miR-9, miR-34a, miR-93) are provided. All tested cell lines were able to grow as multicellular spheroids. In all spheroids except COS4288, calcium deposition was detected by von Kossa staining. We believe that these new cell lines serve as useful biological models for future studies.

Tri-Lineage Differentiation Potential of Osteosarcoma Cell Lines and Human Bone Marrow Stromal Cells from Different Anatomical Locations

The bone cancer osteosarcoma, found mainly in adolescents, routinely forms around the growth plate/metaphysis of long bones. Bone marrow composition changes with age, shifting from a more hematopoietic to an adipocyte-rich tissue. This conversion occurs in the metaphysis during adolescence, implicating a link between bone marrow conversion and osteosarcoma initiation. To assess this, the tri-lineage differentiation potential of human bone marrow stromal cells (HBMSCs) isolated from the femoral diaphysis/metaphysis (FD) and epiphysis (FE) was characterized and compared to two osteosarcoma cell lines, Saos-2 and MG63. Compared to FE-cells, FD-cells showed an increase in tri-lineage differentiation. Additionally, differences were found between the Saos-2 cells exhibiting higher levels of osteogenic differentiation, lower adipogenic differentiation, and a more developed chondrogenic phenotype than MG63, with the Saos-2 being more comparable to FD-derived HBMSCs. The differences found between the FD and FE derived cells are consistent with the FD region containing more hematopoietic tissue compared to the FE. This may be related to the similarities between FD-derived cells and Saos-2 cells during osteogenic and chondrogenic differentiation. These studies reveal distinct differences in the tri-lineage differentiations of 'hematopoietic' and 'adipocyte rich' bone marrow, which correlate with specific characteristics of the two osteosarcoma cell lines.

Development and characterization of new patient-derived xenograft (PDX) models of osteosarcoma with distinct metastatic capacities

Models to study metastatic disease in rare cancers are needed to advance preclinical therapeutics and to gain insight into disease biology, especially for highly aggressive cancers with a propensity for metastatic spread. Osteosarcoma is a rare cancer with a complex genomic landscape in which outcomes for patients with metastatic disease are poor. As osteosarcoma genomes are highly heterogeneous, a large panel of models is needed to fully elucidate key aspects of disease biology and to recapitulate clinically-relevant phenotypes. We describe the development and characterization of osteosarcoma patient-derived xenografts (PDXs) and a panel of PDX-derived cell lines. Matched patient samples, PDXs, and PDX-derived cell lines were comprehensively evaluated using whole genome sequencing and RNA sequencing. PDXs and PDX-derived cell lines largely maintained the expression profiles of the patient from which they were derived despite the emergence of whole-genome duplication (WGD) in a subset of cell lines. These cell line models were heterogeneous in their metastatic capacity and their tissue tropism as observed in both intravenous and orthotopic models. As proof-of-concept study, we used one of these models to test the preclinical effectiveness of a CDK inhibitor on the growth of metastatic tumors in an orthotopic amputation model. Single-agent dinaciclib was effective at dramatically reducing the metastatic burden in this model.

2-Methoxyestradiol Damages DNA in Glioblastoma Cells by Regulating nNOS and Heat Shock Proteins

Gliomas are the most prevalent primary tumors of the central nervous system (CNS), accounting for over fifty percent of all primary intracranial neoplasms. Glioblastoma (GBM) is the most prevalent form of malignant glioma and is often incurable. The main distinguishing trait of GBM is the presence of hypoxic regions accompanied by enhanced angiogenesis. 2-Methoxyestradiol (2-ME) is a well-established antiangiogenic and antiproliferative drug. In current clinical studies, 2-ME, known as Panzem, was examined for breast, ovarian, prostate, and multiple myeloma. The SW1088 grade III glioma cell line was treated with pharmacological and physiological doses of 2-ME. The induction of apoptosis and necrosis, oxidative stress, cell cycle arrest, and mitochondrial membrane potential were established by flow cytometry. Confocal microscopy was used to detect DNA damage. The Western blot technique determined the level of nitric oxide synthase and heat shock proteins. Here, for the first time, 2-ME is shown to induce nitro-oxidative stress with the concomitant modulation of heat shock proteins (HSPs) in the SW1088 grade III glioma cell line. Crucial therapeutic strategies for GMB should address both cell proliferation and angiogenesis, and due to the above, 2-ME seems to be a perfect candidate for GBM therapy.

PHLDA1 promotes glioblastoma cell growth via sustaining the activation state of Ras

Activation of the Ras signaling pathway promotes the growth of malignant human glioblastoma multiforme (GBM). Mutations in Ras are rare in GBM, elevated levels of activated Ras are prevalently observed in GBM. However, the potential mechanism of how Ras is activated in GBM remains unclear. In this study, we screened a new interacted protein of Ras, PHLDA1. Our findings confirmed that PHLDA1 acted as an oncogene and promoted glioma progression and recurrence. We demonstrated that PHLDA1 was upregulated in GBM tissues and cells. PHLDA1 overexpression promoted cell proliferation and tumor growth. In terms of mechanism, PHLDA1 promoted cell proliferation by regulating Ras/Raf/Mek/Erk signaling pathway. Moreover, Src promotes GTPase activity of Ras via tyrosine 32 phosphorylation. PHLDA1 and Src competed for binding with Ras, inhibiting Ras phosphorylation by Src and rescuing Ras activity. This study may provide a new idea of the molecular mechanism underlying glioma progression and a novel potential therapeutic target for comprehensive glioblastoma treatment.

Doxycycline inhibits the progression of metastases in early-stage osteosarcoma by downregulating the expression of MMPs, VEGF and ezrin at primary sites

INTRODUCTION

Osteosarcoma (OS) is the most common primary osseous malignant tumour, with high propensity to metastasise in lungs. Pulmonary micro-metastases are present in up to 80% of patients at initial diagnosis and they are associated with significantly worse prognosis. Doxycycline (Dox) is a synthetic tetracycline that has been shown to have anti-cancer properties in vitro and in vivo, and inhibit angiogenesis - effects that may prove beneficial for several types of cancer. The aim of the present work was to study how Dox affects OS cell growth in vitro and in vivo and OS-driven pulmonary metastasis in vivo.

METHODS

In vitro, the effect of Dox was measured in MG-63 and 143B human OS cell viability, apoptosis, invasion and migration. In vivo, highly metastatic 143B cells were orthotopically implanted into the tibia of SCID mice. The tumour growth and pulmonary metastases between Dox treated and untreated, non-amputated and early amputated xenografts were examined.

RESULTS

In vitro, Dox decreased viability, inhibited invasion, migration, and induced the apoptosis of OS cells. In vivo, Dox significantly enhanced tumour necrosis at primary OS sites, similarly to its in vitro effect, and downregulated the expression of Ki67, MMP2, MMP9, VEGFA and ezrin. It also decreased circulating VEGFA and MMP9 protein levels, in line with the decreased metastatic burden in Dox-treated mice (non-amputated and early-amputated).

CONCLUSIONS

Reprofiling of Dox can prevent the evolvement of pulmonary micro-metastases to clinically detectable macro-metastases and suppress the lethal progress of OS by inhibiting the expression of MMPs, VEGFA and ezrin at primary sites.

ERK phosphorylation is dependent on cell adhesion in a subset of pediatric sarcoma cell lines

Osteosarcoma (OS) and Pax-Foxo1 fusion negative rhabdomyosarcoma (FN-RMS) are pediatric sarcomas with poor prognoses in patients with advanced disease. In both malignancies, an actin binding protein has been linked to poor prognosis. Integrin adhesion complexes (IACs) are closely coupled to actin networks and IAC-mediated signaling has been implicated in the progression of carcinomas. However, the relationship of IACs and actin cytoskeleton remodeling with cell signaling is understudied in pediatric sarcomas. Here, we tested the hypothesis that IAC dynamics affect ERK activation in OS and FN-RMS cell lines. Adhesion dependence of ERK activation differed among the OS and FN-RMS cells examined. In the OS cell lines, adhesion did not have a consistent effect on phospho-ERK (pERK). ERK phosphorylation in response to fetal calf serum or 1 ng/ml EGF was nearly as efficient in OS cell lines and one FN-RMS cell line in suspension as cells adherent to poly-l-lysine (PL) or fibronectin (FN). By contrast, adhesion to plastic, PL or FN increased ERK phosphorylation and was greater than additive with a 15 min exposure to 1 ng/ml EGF in three FN-RMS cell lines. Increases in pERK were partly dependent on FAK and PAK1/2 but independent of IAC maturation. As far as we are aware, this examination of adhesion-dependent signaling is the first in pediatric sarcomas and has led to the discovery of differences from the prevailing paradigms and differences in the degree of coupling between components in the signaling pathways among the cell lines.

A Novel Microwave Resonant Sensor for Measuring Cancer Cell Line Aggressiveness

The measurement of biological tissues' dielectric properties plays a crucial role in determining the state of health, and recent studies have reported microwave biosensing to be an innovative method with great potential in this field. Research has been conducted from the tissue level to the cellular level but, to date, cellular adhesion has never been considered. In addition, conventional systems for diagnosing tumor aggressiveness, such as a biopsy, are rather expensive and invasive. Here, we propose a novel microwave approach for biosensing adherent cancer cells with different malignancy degrees. A circular patch resonator was designed adjusting its structure to a standard Petri dish and a network analyzer was employed. Then, the resonator was realized and used to test two groups of different cancer cell lines, based on various tumor types and aggressiveness: low- and high-aggressive osteosarcoma cell lines (SaOS-2 and 143B, respectively), and low- and high-aggressive breast cancer cell lines (MCF-7 and MDA-MB-231, respectively). The experimental results showed that the sensitivity of the sensor was high, in particular when measuring the resonant frequency. Finally, the sensor showed a good ability to distinguish low-metastatic and high-metastatic cells, paving the way to the development of more complex measurement systems for noninvasive tissue diagnosis.

Canine and murine models of osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor in children. Despite efforts to develop and implement new therapies, patient outcomes have not measurably improved since the 1980s. Metastasis continues to be the main source of patient mortality, with 30% of cases developing metastatic disease within 5 years of diagnosis. Research models are critical in the advancement of cancer research and include a variety of species. For example, xenograft and patient-derived xenograft (PDX) mouse models provide opportunities to study human tumor cells in vivo while transgenic models have offered significant insight into the molecular mechanisms underlying OS development. A growing recognition of naturally occurring cancers in companion species has led to new insights into how veterinary patients can contribute to studies of cancer biology and drug development. The study of canine cases, including the use of diagnostic tissue archives and clinical trials, offers a potential mechanism to further canine and human cancer research. Advancement in the field of OS research requires continued development and appropriate use of animal models. In this review, animal models of OS are described with a focus on the mouse and tumor-bearing pet dog as parallel and complementary models of human OS.

Analysis and identification of m6A RNA methylation regulators in metastatic osteosarcoma

Osteosarcoma (OS) is characterized by rapid growth and early metastasis. However, its mechanism remains unclear. N6-methyladenosine (m6A) modification and its regulatory factors play essential roles in most cancers, including OS. In this study, we screened out 21 m6A modifiers using the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database, followed by the identification of the critical m6A methylation modifiers. The results revealed that the expression levels of three m6A methylation regulators, namely RBM15, METTL3, and LRPPRC, were associated with the low survival rate of patients with OS. We further studied the independent prognostic factors by performing univariate and multivariate Cox analyses and found that metastasis was an independent prognostic factor for patients with OS. Furthermore, we found for the first time that RBM15 was specific for metastatic OS rather than non-metastatic OS. Moreover, the significant overexpression of RBM15 was validated in metastatic OS cell lines and in actual human clinical specimens. We also revealed that RBM15 promoted the invasion, migration, and metastasis of OS cells through loss-functional and gain-functional experiments and an animal metastatic model. In conclusion, RBM15 has a high correlation with OS metastasis formation and the decreased survival rate of patients with OS, and this may serve as a useful biomarker for predicting metastasis and prognosis of patients with OS.

Osteosarcoma and Metastasis

Osteosarcoma is the most common primary bone malignancy in adolescents. Its high propensity to metastasize is the leading cause for treatment failure and poor prognosis. Although the research of osteosarcoma has greatly expanded in the past decades, the knowledge and new therapy strategies targeting metastatic progression remain sparse. The prognosis of patients with metastasis is still unsatisfactory. There is resonating urgency for a thorough and deeper understanding of molecular mechanisms underlying osteosarcoma to develop innovative therapies targeting metastasis. Toward the goal of elaborating the characteristics and biological behavior of metastatic osteosarcoma, it is essential to combine the diverse investigations that are performed at molecular, cellular, and animal levels from basic research to clinical translation spanning chemical, physical sciences, and biology. This review focuses on the metastatic process, regulatory networks involving key molecules and signaling pathways, the role of microenvironment, osteoclast, angiogenesis, metabolism, immunity, and noncoding RNAs in osteosarcoma metastasis. The aim of this review is to provide an overview of current research advances, with the hope to discovery druggable targets and promising therapy strategies for osteosarcoma metastasis and thus to overcome this clinical impasse.

Impact of limb amputation and cisplatin chemotherapy on metastatic progression in mouse models of osteosarcoma

Development of animal models that accurately recapitulate human cancer is an ongoing challenge. This is particularly relevant in the study of osteosarcoma (OS), a highly malignant bone tumor diagnosed in approximately 1000 pediatric/adolescent patients each year. Metastasis is the leading cause of patient death underscoring the need for relevant animal models of metastatic OS. In this study, we describe how existing OS mouse models can be interrogated in a time-course context to determine the kinetics of spontaneous metastasis from an orthotopically implanted primary tumor. We evaluated four highly metastatic OS cell lines (3 human, 1 mouse) to establish a timeline for metastatic progression in immune deficient NSG mice. To discern the effects of therapy on tumor development and metastasis in these models, we investigated cisplatin therapy and surgical limb amputation at early and late timepoints. These data help define the appropriate observational periods for studies of metastatic progression in OS and further our understanding of existing mouse models. Efforts to advance the study of metastatic OS are critical for facilitating the identification of novel therapeutics and for improving patient survival.

Assessing a Novel 3D Assay System for Drug Screening against OS Metastasis

Osteosarcoma (OS) is an aggressive mesenchymal cell tumor that carries a poor long-term prognosis. Despite definitive surgery for the primary tumor and adjuvant chemotherapy, pulmonary metastasis is common and is the primary cause of morbidity. To improve outcomes for patients, we have developed and optimized a phenotypic screen for drugs that may target OS disseminated tumor cells (DTCs) and inhibit their metastatic outbreak rather than merely screening for cytotoxic activity against proliferating cells, as is commonly conducted in conventional drug discovery approaches. We report on the validation of a previously described 3D reconstituted basement membrane extract (3D BME) model system for tumor dormancy and metastatic outgrowth adapted to clonal pairs of high and low metastatic OS cells. A post-hoc validation of the assay was possible by comparing the activity of a drug in our assay with early evidence of activity in human OS clinical trials (regorafenib and saracatinib). In this validation, we found concordance between our assay and human clinical trial experience We then explored an approved veterinary small molecule inhibitor of Janus kinase-1 (oclacitinib) as a potential drug candidate to take advantage of the high prevalence of OS in pet dogs and its translational value to humans. Despite the biological rationale, we found no evidence to support the use of oclacitinib as an antimetastatic agent in OS. The findings support our 3D BME assay as a highly efficient method to examine drugs for activity in targeting OS DTCs.

Comparison of Osteosarcoma Aggregated Tumour Models with Human Tissue by Multimodal Mass Spectrometry Imaging

Osteosarcoma (OS) is the most common primary bone malignancy and largely effects adolescents and young adults, with 60% of patients under the age of 25. There are multiple cell models of OS described in vitro that express the specific genetic alterations of the sarcoma. In the work reported here, multiple mass spectrometry imaging (MSI) modalities were employed to characterise two aggregated cellular models of OS models formed using the MG63 and SAOS-2 cell lines. Phenotyping of the metabolite activity within the two OS aggregoid models was achieved and a comparison of the metabolite data with OS human tissue samples revealed relevant fatty acid and phospholipid markers. Although, annotations of these species require MS/MS analysis for confident identification of the metabolites. From the putative assignments however, it was suggested that the MG63 aggregoids are an aggressive tumour model that exhibited metastatic-like potential. Alternatively, the SAOS-2 aggregoids are more mature osteoblast-like phenotype that expressed characteristics of cellular differentiation and bone development. It was determined the two OS aggregoid models shared similarities of metabolic behaviour with different regions of OS human tissues, specifically of the higher metastatic grade.

PHLDA1 expression in ulcerative colitis: A potential role in the management of dysplasia

Pleckstrin homology-like domain, family A, member 1 (PHLDA1) is a protein involved in cell proliferation, adhesion and migration in colon cancer. In normal large intestinal mucosa, this protein is expressed only in the crypts. By contrast, its expression in adenomas and cancers of the large intestine is spread throughout the glandular ducts, and it has been reported that PHLDA1 may be involved in the process of carcinogenesis. PHLDA1 may also be involved in the pathogenesis of ulcerative colitis (UC). The expression levels of PHLDA1 in tissues from patients with UC were analyzed using immunohistochemistry, and its relationship with the development of UC-associated colorectal cancer (UC-CRC) was examined. Overall, tissue samples from 143 lesions (90 colitis lesions, 39 dysplastic lesions and 14 UC-CRC lesions) were prepared from excised specimens of 49 patients with UC who underwent surgery in Tokyo Medical and Dental University Hospital between January 2004 and December 2017. Subsequently, immunostaining for PHLDA1 was performed. PHLDA1 expression was evaluated in UC-CRC and dysplastic tissues within the entire lesion area on the slide and in colitis over the area of the accompanying duct. The cytoplasmic staining intensity was classified into four levels, and the expression score (0-2 points) was calculated. The median PHLDA1 expression score was 0.295 for colitis, 0.607 for dysplasia and 0.865 for UC-CRC. The dysplasia expression score was significantly higher than the colitis score (P<0.001), while the UC-CRC expression score was significantly higher than the dysplasia score (P=0.003). The expression levels of PHLDA1 in UC cases were higher in colitis, followed by dysplasia and UC-CRC, which suggested that this protein may be involved in the carcinogenesis of UC-CRC. In addition, PHLDA1 immunostaining may help in the diagnosis of dysplasia, which is a type of precancerous lesion.

NSG Mice Facilitate ex vivo Characterization of Ewing Sarcoma Lung Metastasis Using the PuMA Model

Ewing sarcoma (EwS) is a highly malignant bone and soft tissue tumor primarily affecting children and young adults. While most patients initially respond well to conventional front-line therapy, frequent metastasis results in poor 5-year overall survival rates for this disease. Accordingly, there is a critical need to develop better models to understand EwS metastasis. We and others previously used the ex vivo pulmonary metastasis assay (PuMA) to study lung metastasis in solid tumors including osteosarcoma (OS), but this technique has to date not been achievable for EwS. PuMA involves tail vein injection of fluorescent tumor cells into NOD-SCID mice, followed by their visualization in long-term cultures of tumor-bearing lung explants. Here we demonstrate successful implementation of PuMA for EwS cells using NOD-SCID-IL2 receptor gamma null (NSG) immunocompromised mice, which demonstrated high engraftment of EwS cell lines compared to NOD-SCID mice. This may be linked to immune permissiveness required by EwS cells, as increased basal cytotoxicity of EwS cells was observed in NOD-SCID compared to NSG lung sections, possibly due to the absence of natural killer (NK) cell activity in the latter. Together, our data demonstrate the utility of NSG mice for PuMA modeling of EwS lung metastasis.

Prognostic Implications of the Complement Protein C1Q and Its Correlation with Immune Infiltrates in Osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most widespread bone tumour among childhood cancers, and distant metastasis is the dominant factor in poor prognosis for patients with OS. Therefore, it is necessary to identify new prognostic biomarkers for identifying patients with aggressive disease.

METHODS

Two OS datasets (GSE21257 and GSE33383) were downloaded from the Gene Expression Omnibus (GEO) and subsequently subjected to weighted gene co-expression network analysis (WGCNA) and differential gene expression analysis (DGE) to screen candidate genes. A prognostic model was constructed using OS data derived from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) program to further screen key genes and perform gene ontology (GO) analysis. The prognostic values of key genes were assessed using the Kaplan-Meier (KM) plotter. The GEO dataset was used for immune infiltration analysis and association analysis of key genes. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to validate the expression levels of potentially crucial genes in OS cell lines.

RESULTS

In the present study, we found 114 genes with a highly significant correlation in the module and 44 downregulated genes; 25 candidate genes overlapped in the two parts of the genes. Among these, three key genes, C1QA, C1QB, and C1QC, were the most significant hub genes, which had the highest node degrees, were clustered into one group, and implicated in most significant biological processes (regulation of immune effector process). Moreover, these three key genes were negatively associated with the prognosis of OS and positively associated with three immune cells (follicular helper T cells, memory B cells, and CD8 T cells). Additionally, compared to non-metastatic OS cell lines, the expression of three key genes was significantly downregulated in metastatic OS cell lines.

CONCLUSION

Our results revealed that three key genes (C1QA, C1QB, and C1QC) were implicated in tumour immune infiltration and may be promising biomarkers for predicting metastasis and prognosis of patients with OS.

Sodium Fluoride-18 and Radium-223 Dichloride Uptake Colocalize in Osteoblastic Mouse Xenograft Tumors

Background: Patients with osteoblastic bone metastases are candidates for radium-223 (²²³RaCl₂) therapy and may undergo sodium fluoride-18 (¹⁸F-NaF) positron emission tomography-computed tomography imaging to identify bone lesions. ¹⁸F-NaF has been shown to predict ²²³RaCl₂ uptake, but intratumor distributions of these two agents remain unclear. In this study, the authors evaluate the spatial distribution and relative uptakes of ¹⁸F-NaF and ²²³RaCl₂ in Hu09-H3 human osteosarcoma mouse xenograft tumors at macroscopic and microscopic levels to better quantify their correlation. Materials and Methods: ¹⁸F-NaF and ²²³RaCl₂ were co-injected into Hu09-H3 xenograft tumor severe combined immunodeficient mice. Tumor content was determined from in vivo biodistributions and visualized by PET, single photon emission computed tomography, and CT imaging. Intratumor distributions were visualized by quantitative autoradiography of tumor tissue sections and compared to histology of the same or adjacent sections. Results: ¹⁸F and ²²³Ra accumulated in proportional amounts in whole Hu09-H3 tumors (r² = 0.82) and in microcalcified regions within these tumors (r² = 0.87). Intratumor distributions of ¹⁸F and ²²³Ra were spatially congruent in these microcalcified regions. Conclusions: ¹⁸F-NaF and ²²³RaCl₂ uptake are strongly correlated in heterogeneously distributed microcalcified regions of Hu09-H3 xenograft tumors, and thus, tumor accumulation of ¹⁸F is predictive of ²²³Ra accumulation. Hu09-H3 xenograft tumors appear to possess certain histopathological features found in patients with metastatic bone disease and may be useful in clarifying the relationship between administered ²²³Ra dose and therapeutic effect.

Transcriptional activators YAP/TAZ and AXL orchestrate dedifferentiation, cell fate, and metastasis in human osteosarcoma

Osteosarcoma (OS) is a molecularly heterogeneous, aggressive, poorly differentiated pediatric bone cancer that frequently spreads to the lung. Relatively little is known about phenotypic and epigenetic changes that promote lung metastases. To identify key drivers of metastasis, we studied human CCH-OS-D OS cells within a previously described rat acellular lung (ACL) model that preserves the native lung architecture, extracellular matrix, and capillary network. This system identified a subset of cells—termed derived circulating tumor cells (dCTCs)—that can migrate, intravasate, and spread within a bioreactor-perfused capillary network. Remarkably, dCTCs highly expressed epithelial-to-mesenchymal transition (EMT)-associated transcription factors (EMT-TFs), such as ZEB1, TWIST, and SOX9, which suggests that they undergo cellular reprogramming toward a less differentiated state by coopting the same epigenetic machinery used by carcinomas. Since YAP/TAZ and AXL tightly regulate the fate and plasticity of normal mesenchymal cells in response to microenvironmental cues, we explored whether these proteins contributed to OS metastatic potential using an isogenic pair of human OS cell lines that differ in AXL expression. We show that AXL inhibition significantly reduced the number of MG63.2 pulmonary metastases in murine models. Collectively, we present a laboratory-based method to detect and characterize a pure population of dCTCs, which provides a unique opportunity to study how OS cell fate and differentiation contributes to metastatic potential. Though the important step of clinical validation remains, our identification of AXL, ZEB1, and TWIST upregulation raises the tantalizing prospect that EMT-TF-directed therapies might expand the arsenal of therapies used to combat advanced-stage OS.

Identification of potential modulators of osteosarcoma metastasis by high-throughput cellular screening of natural products

A high-throughput screening assay was developed and applied to a large library of natural product extract samples, in order to identify compounds which preferentially inhibited the in vitro 2D growth of a highly metastatic osteosarcoma cell line (MG63.3) compared to a cognate parental cell line (MG63) with low metastatic potential. Evaluation of differentially active natural product extracts with bioassay-guided fractionation led to the identification of lovastatin (IC50  = 11 µm) and the limonoid toosendanin (IC50  = 26 nm). Other statins and limonoids were then tested, and cerivastatin was identified as a particularly potent (IC50  < 0.1 µm) and selective agent. These compounds potently and selectively induced apoptosis in MG63.3 cells, but not MG63. Assays with other cell pairs were used to examine the generality of these results. Statins and limonoids may represent unexplored opportunities for development of modulators of osteosarcoma metastasis. As cerivastatin was previously approved for clinical use, it could be considered for repurposing in osteosarcoma, pending validation in further models.

Targetable Intercellular Signaling Pathways Facilitate Lung Colonization in Osteosarcoma

Outcomes for young people diagnosed with osteosarcoma hinge almost exclusively on whether they develop lung metastasis. The striking predilection that osteosarcoma shows for metastatic spread to lung suggests properties and/or lung interactions that generate tissue-specific survival and proliferation advantages. While these mechanisms remain overall poorly defined, studies have begun to describe biological elements important to metastasis. Mechanisms described to date include both cell-autonomous adaptations that allow disseminated tumor cells to survive the stressors imposed by metastasis and intercellular signaling networks that tumor cells exploit to pirate needed signals from surrounding tissues or to recruit other cells that create a more favorable niche. Evidence suggests that cell-autonomous changes are largely driven by epigenetic reprogramming of disseminated tumor cells that facilitates resistance to late apoptosis, manages endoplasmic reticulum (ER) stressors, promotes translation of complex transcripts, and activates clotting pathways. Tumor-host signaling pathways important for lung colonization drive interactions with lung epithelium, mesenchymal stem cells, and mediators of innate and adaptive immunity. In this chapter, we highlight one particular pathway that integrates cell-autonomous adaptations with lung-specific tumor-host interactions. In this mechanism, aberrant ΔNp63 expression primes tumor cells to produce IL6 and CXCL8 upon interaction with lung epithelial cells. This tumor-derived IL6 and CXCL8 then initiates autocrine, osteosarcoma-lung paracrine, and osteosarcoma-immune paracrine interactions that facilitate metastasis. Importantly, many of these pathways appear targetable with clinically feasible therapeutics. Ongoing work to better understand metastasis is driving efforts to improve outcomes by targeting the most devastating complication of this disease.

Tumor cell MT1-MMP is dispensable for osteosarcoma tumor growth, bone degradation and lung metastasis

The membrane-anchored matrix metalloprotease MT1-MMP is a potent collagenolytic enzyme with a well-established role in extracellular matrix turnover and cellular invasion into collagen-rich tissues. MT1-MMP is highly expressed in various types of cancer and has been demonstrated to be directly involved in several stages of tumor progression, including primary tumor growth, angiogenesis, invasion and metastasis. Osteosarcoma is the most common type of primary bone cancer. This disease is characterized by invasive tumor growth, leading to extensive bone destruction, and metastasis to the lungs. The tumor cells in human osteosarcoma display a strong expression of MT1-MMP, but the role of MT1-MMP in osteosarcoma progression is currently unknown. In this study, we investigated the role of MT1-MMP during various stages of osteosarcoma development. We utilized an optimized orthotopic murine osteosarcoma model and human osteosarcoma cells in which the MT1-MMP gene was knocked out using CRISPR/Cas9. We observed a strong expression of MT1-MMP in wildtype cells of both primary tumors and lung metastases, but, surprisingly, MT1-MMP deficiency did not affect primary tumor growth, bone degradation or the formation and growth of lung metastases. We therefore propose that, unlike findings reported in other cancers, tumor-expressed MT1-MMP is dispensable for all stages of osteosarcoma progression.

Prognostic value of tumoral and peritumoral magnetic resonance parameters in osteosarcoma patients for monitoring chemotherapy response

Objectives

To evaluate parameters of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as early imaging indicators of tumor histologic response to pre-operative neoadjuvant chemotherapy and as probable prognostic factors for event-free survival (EFS) and overall survival in osteosarcoma (OS) in both tumoral and peritumoral areas.

Methods

Thirty-four OS patients who received three courses of neoadjuvant chemotherapy followed by surgery during 2014–2018 were enrolled in this study. All patients underwent baseline and post-chemotherapy DWI and DCE-MRI. Lesion region was defined as the tumoral area and peritumoral area. Parameters of apparent diffusion coefficient, capacity transfer constant (Ktrans), elimination rate constant, extravascular extracellular space volume ratio (Ve), and initial area under the curve as well as corresponding differences between pre- and post-chemotherapy in lesion regions were evaluated. Receiver operating characteristic analysis was used to evaluate the diagnostic performance of these parameters. The associations of all parameters with tumor histologic response, EFS, and overall survival were also calculated.

Results

In the tumor area, moderate evidence was found that post-Ktrans was lower in responders as compared with that in poor responders (p = 0.04, false discovery rate [FDR] corrected), and ΔKtrans exhibited significant between-groups differences (p = 0.04, Bonferroni corrected; or p = 0.006, FDR corrected). Weak evidence for the between-groups difference was found in the Ve in the peritumoral area (p = 0.025 before treatment and p = 0.021 after treatment, uncorrected). Furthermore, lower post-Ktrans in the tumoral area and lower pre-Ve in the peritumoral area were significant prognostic indicators for longer EFS (p = 0.002, p = 0.026) and overall survival (p = 0.003, p = 0.023).

Conclusions

In OS, DWI and DCE-MRI parameters in both tumoral and peritumoral areas can reflect the chemotherapy response and prognosticate EFS and overall survival.

Key Points

• Peritumoral MRI parameters can reflect the chemotherapy response in OS patients.

• Peritumoral MRI parameters can predict EFS and overall survival in OS patients.

• MRI parameters may be predictive factors for evaluating chemotherapy efficacy and EFS.

Quantitative Lipidomic Analysis of Osteosarcoma Cell-Derived Products by UHPLC-MS/MS

Changes in lipid metabolism are involved in several pathological conditions, such as cancer. Among lipids, eicosanoids are potent inflammatory mediators, synthesized from polyunsaturated fatty acids (PUFAs), which coexist with other lipid-derived ones, including endocannabinoids (ECs) and N-acylethanolamides (NAEs). In this work, a bioanalytical assay for 12 PUFAs/eicosanoids and 20 ECs/NAEs in cell culture medium and human biofluids was validated over a linear range of 0.1-2.5 ng/mL. A fast pretreatment method consisting of protein precipitation with acetonitrile followed by a double step liquid-liquid extraction was developed. The final extracts were injected onto a Kinetex ultra-high-performance liquid chromatography (UHPLC) XB-C18 column with a gradient elution of 0.1% formic acid in water and methanol/acetonitrile (5:1; v/v) mobile phase. Chromatographic separation was followed by detection with a triple-quadrupole mass spectrometer operating both in positive and negative ion-mode. A full validation was carried out in a small amount of cell culture medium and then applied to osteosarcoma cell-derived products. To the best of our knowledge, this is the first lipid profiling of bone tumor cell lines (SaOS-2 and MG-63) and their secretome. Our method was also partially validated in other biological matrices, such as serum and urine, ensuring its broad applicability as a powerful tool for lipidomic translational research.

Targeting aggressive osteosarcoma with a peptidase-enhanced cytotoxic melphalan flufenamide

Background:

Low survival rates in metastatic high-grade osteosarcoma (HGOS) have remained stagnant for the last three decades. This study aims to investigate the role of aminopeptidase N (ANPEP) in HGOS progression and its targeting with a novel lipophilic peptidase-enhanced cytotoxic compound melphalan flufenamide (melflufen) in HGOS.

Methods:

Meta-analysis of publicly available gene expression datasets was performed to determine the impact of ANPEP gene expression on metastasis-free survival of HGOS patients. The efficacy of standard-of-care anti-neoplastic drugs and a lipophilic peptidase-enhanced cytotoxic conjugate melflufen was investigated in patient-derived HGOS ex vivo models and cell lines. The kinetics of apoptosis and necrosis induced by melflufen and doxorubicin were compared. Anti-neoplastic effects of melflufen were investigated in vivo.

Results:

Elevated ANPEP expression in diagnostic biopsies of HGOS patients was found to significantly reduce metastasis-free survival. In drug sensitivity assays, melflufen has shown an anti-proliferative effect in HGOS ex vivo samples and cell lines, including those resistant to methotrexate, etoposide, doxorubicin, and PARP inhibitors. Further, HGOS cells treated with melflufen displayed a rapid induction of apoptosis and this sensitivity correlated with high expression of ANPEP. In combination treatments, melflufen demonstrated synergy with doxorubicin in killing HGOS cells. Finally, Melflufen displayed anti-tumor growth and anti-metastatic effects in vivo.

Conclusion:

This study may pave the way for use of melflufen as an adjuvant to doxorubicin in improving the therapeutic efficacy for the treatment of metastatic HGOS.

CAM-Delam: an in vivo approach to visualize and quantify the delamination and invasion capacity of human cancer cells

The development of metastases is the major cause of cancer related death. To develop a standardized method that define the ability of human cancer cells to degrade the basement membrane, e.g. the delamination capacity, is of importance to assess metastatic aggressiveness. We now present the in vivo CAM-Delam assay to visualize and quantify the ability of human cancer cells to delaminate and invade. The method includes seeding cancer cells on the chick chorioallantoic membrane (CAM), followed by the evaluation of cancer-induced delamination and potential invasion within hours to a few days. By testing a range of human cancer cell lines in the CAM-Delam assay, our results show that the delamination capacity can be divided into four categories and used to quantify metastatic aggressiveness. Our results emphasize the usefulness of this assay for quantifying delamination capacity as a measurement of metastatic aggressiveness, and in unraveling the molecular mechanisms that regulate delamination, invasion, formation of micro-metastases and modulations of the tumor microenvironment. This method will be useful in both the preclinical and clinical characterization of tumor biopsies, and in the validation of compounds that may improve survival in metastatic cancer.

Tegavivint and the β-Catenin/ALDH Axis in Chemotherapy-Resistant and Metastatic Osteosarcoma

BACKGROUND

The Wnt/β-catenin pathway is closely associated with osteosarcoma (OS) development and metastatic progression. We investigated the antitumor activity of Tegavivint, a novel β-catenin/transducin β-like protein 1 (TBL1) inhibitor, against OS employing in vitro, ex vivo, and in vivo cell line and patient-derived xenograft (PDX) models that recapitulate high risk disease.

METHODS

The antitumor efficacy of Tegavivint was evaluated in vitro using established OS and PDX-derived cell lines. Use of an ex vivo three-dimensional pulmonary metastasis assay assessed targeting of β-catenin activity during micro- and macrometastatic development. The in vivo activity of Tegavivint was evaluated using chemoresistant and metastatic OS PDX models. Gene and protein expression were quantified by quantitative Reverse transcription polymerase chain reaction or immunoblot analysis. Bone integrity was determined via microCT. All statistical tests were two-sided.

RESULTS

Tegavivint exhibited antiproliferative activity against OS cells in vitro and actively reduced micro- and macrometastatic development ex vivo. Multiple OS PDX tumors (n = 3), including paired patient primary and lung metastatic tumors with inherent chemoresistance, were suppressed by Tegavivint in vivo. We identified that metastatic lung OS cell lines (n = 2) exhibited increased stem cell signatures, including enhanced concomitant aldehyde dehydrogenase (ALDH1) and β-catenin expression and downstream activity, which were suppressed by Tegavivint (ALDH1: control group, mean relative mRNA expression = 1.00, 95% confidence interval [CI] = 0.68 to 1.22 vs Tegavivint group, mean = 0.011, 95% CI = 0.0012 to 0.056, P < .001; β-catenin: control group, mean relative mRNA expression = 1.00, 95% CI = 0.71 to 1.36 vs Tegavivint group, mean = 0.45, 95% CI = 0.36 to 0.52, P < .001). ALDH1high PDX-derived lung OS cells, which demonstrated enhanced metastatic potential compared with ALDHlow cells in vivo, were sensitive to Tegavivint. Toxicity studies revealed decreased bone density in male Tegavivint-treated mice (n = 4 mice per group).

CONCLUSIONS

Tegavivint is a promising therapeutic agent for advanced stages of OS via its targeting of the β-catenin/ALDH1 axis.

PHLD Class Proteins: A Family of New Players in the p53 Network

The Pleckstrin Homology-like Domain (PHLD) class of proteins are multifunctional proteins. The class is comprised of two families of proteins, PHLDA and PHLDB, each with 3 members. All members of the families possess a pleckstrin homology (PH) domain. Though identified nearly 30 years ago, this class of proteins remains understudied with PHLDA family members receiving most of the research attention. Recent studies have also begun to reveal the functions of the PHLDB family proteins in regulation of p53 and AKT signaling pathways important for cancer and metabolism. This review will discuss current research and offer some prospects on the possible roles of both families in cancer and metabolism.

Establishment and Characterization of a Recurrent Osteosarcoma Cell Line: OSA 1777

Osteosarcoma (OSA) is the most common primary bone malignancy overall and is responsible for considerable adolescent mortality. Approximately 850 patients are newly diagnosed with OSA in the United States each year. While the 5-year survival rate for localized OSA has improved from <20% over 40 years ago to over 65% today, progress has dwindled over the past three decades. Therapeutic stagnation has occurred, in part, as a result of limited preclinical models and the overall heterogeneity of OSA among patients. In this study, we report the establishment and characterization of a novel OSA cell line: OSA 1777. This cell line was isolated from the recurrent tumor specimen of a 19-year-old female who initially experienced 99% tumor necrosis after neoadjuvant chemotherapy and eventually had local recurrence and metastases. We present OSA 1777 growth characteristics, tumor markers, chemotherapeutic sensitivities, and oncogenic spheroid formation. In a two-dimensional (2D) monolayer culture, OSA 1777 exhibited a spindle shape and 60 h doubling time. STR DNA profiling revealed a unique genomic identity not matching any existing human cancer cell lines from the ATCC or DSMZ databases. Consistent with the mesenchymal origin, western blot was positive for vimentin and negative for the carcinoma marker cytokeratin. Within three-dimensional (3D) culture, the cells formed spheroids of similar patterning and smaller size compared with MNNG-HOS and U2OS cell lines. The chemotherapeutic drug sensitivity of OSA 1777 was evaluated in both 2D and 3D culture systems. In summary, we report OSA 1777 as a novel biological model of OSA amenable to future studies focused on OSA that recurs despite an initially strong chemotherapeutic response. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:902-910, 2020.

The potential of micelleplexes as a therapeutic strategy for osteosarcoma disease

Osteosarcoma (OS) is a rare aggressive bone, presenting low patient survival rate, high metastasis and relapse occurrence, mostly due to multi-drug resistant cells. To surpass that, the use of nanomedicine for the targeted delivery of genetic material, drugs or both have been extensively researched. In this review, we address the current situation of the disorder and some gene therapy options in the nanomedicine field that have been investigated. Among them, polymeric micelles (PM) are an advantageous therapeutic alternative highly explored for OS, as they allow for the targeted transportation of poorly water-soluble drugs to cancer cells. In addition, micelleplexes are PMs with cationic properties with promising features, such as the possibility for a dual therapy, which have made them an attractive research subject. The aim of this review article is to elucidate the application of a micelleplex formulation encapsulating the underexpressed miRNA145 to achieve an active targeting to OS cells and overcome multi-drug resistance, as a new and viable therapeutic strategy.

Glutaminase-1 (GLS1) inhibition limits metastatic progression in osteosarcoma

BACKGROUND

Osteosarcoma (OS) is a malignant bone tumor that often develops during the period of rapid growth associated with adolescence. Despite successful primary tumor control accompanied by adjuvant chemotherapy, death from pulmonary metastases occurs in approximately 30% of patients within 5 years. As overall survival in patients remains unchanged over the last 30 years, urgent needs for novel therapeutic strategies exist. Cancer metastasis is characterized by complex molecular events which result from alterations in gene and protein expression/function. Recent studies suggest that metabolic adaptations, or "metabolic reprogramming," may similarly contribute to cancer metastasis. The goal of this study was to specifically interrogate the metabolic vulnerabilities of highly metastatic OS cell lines in a series of in vitro and in vivo experiments, in order to identify a tractable metabolically targeted therapeutic strategy for patients.

METHODS

Nutrient deprivation and drug treatment experiments were performed in MG63.3, 143B, and K7M2 OS cell lines to identify the impact of glutaminase-1 (GLS1) inhibition and metformin treatment on cell proliferation. We functionally validated the impact of drug treatment with extracellular flux analysis, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry. 13C-glucose and 13C-glutamine tracing was employed to identify specific contributions of these nutrients to the global metabolic profiles generated with GLS1 inhibition and metformin treatment in vivo.

RESULTS

Highly metastatic OS cell lines require glutamine for proliferation, and exposure to CB-839, in combination with metformin, induces both primary tumor growth inhibition and a distinct reduction in metastatic outgrowth in vivo. Further, combination-treated OS cells showed a reduction in cellular mitochondrial respiration, while NMR confirmed the pharmacodynamic effects of glutaminase inhibition in tumor tissues. We observed global decreases in glycolysis and tricarboxylic acid (TCA) cycle functionality, alongside an increase in fatty acid oxidation and pyrimidine catabolism.

CONCLUSIONS

This data suggests combination-treated cells cannot compensate for metformin-induced electron transport chain inhibition by upregulating glutaminolysis to generate TCA cycle intermediates required for cell proliferation, translating into significant reductions in tumor growth and metastatic progression. This therapeutic approach could be considered for future clinical development for OS patients presenting with or at high risk of developing metastasis.