Concise review: mesenchymal tumors: when stem cells go mad

68 Ga-Pentixafor PET/CT for in-vivo mapping of CXCR4 receptors as potential radiotheranostic targets in soft tissue and bone sarcoma: preliminary results

OBJECTIVE

To evaluate the diagnostic utility of 68 Ga-Pentixafor PET/CT for in vivo imaging of CXCR4 receptors in soft tissue/bone sarcoma.

METHODS

Ten (7M: 3F; mean age = 24.7 ± 14.2 years) consecutive patients with clinical and radiological evidence of bone/soft tissue sarcoma were recruited prospectively whole body 68 Ga-Pentixafor PET/CT imaging was performed at 60-min after tracer administration. After performing standard CT, PET acquisition from head to toe was done (3 min/bed position) in a caudocranial direction. PET/CT data was reconstructed and SUV max , SUV mean values, target-to-background ratio (TBR) and active tumor volume (cc) were computed for the tracer avid lesions. Histopathological and IHC analysis was performed on the surgically excised primary tumors. CXCR4 receptors' intensity was evaluated by visual scoring.

RESULTS

The mean SUV max and SUV mean values in the primary tumors were 4.80 ± 1.0 (3.9-7.7) and 2.40 ± 0.60 (0.9-4.0). The mean TBR and tumor volume (cc) were 1.84 ± 1.3 and 312.2 ± 285. Diagnosis of osteosarcoma in 7, chondrosarcoma, leiomyosarcoma and synovial sarcoma in 1 patient each was confirmed on HP analysis. Distant metastatic lesions were seen in 3/10 patients. Nuclear CXCR4 receptors' positivity was seen in 5, cytoplasmic in 4 and both pattern seen in 1 patient. The mean CXCR4 receptors' intensity was found to be 7.6 ± 2. The highest SUV max value of 7.7 was observed in the patient having both cytoplasmic and nuclear CXCR4 expression. SUV max was found to be poorly correlated ( r  = 0.441) with CXCR4 expression.

CONCLUSION

68 Ga-Pentixafor PET/CT detects CXCR4 receptors over-expressed in sarcoma, its radio-theranostics potential needs detailed evaluation.

Changes in the small noncoding RNA transcriptome in osteosarcoma cells

BACKGROUND

Osteosarcoma has the highest incidence among bone malignant tumors and mainly occurs in adolescents and the elderly, but the pathological mechanism is still unclear, which makes early diagnosis and treatment very difficult. Bone marrow mesenchymal stem cells (BMSCs) are considered to be one of the sources of osteosarcoma cells. Therefore, a full understanding of the gene expression differences between BMSCs and osteosarcoma cells is very important to explore the pathogenesis of osteosarcoma and facilitate the early diagnosis and treatment of osteosarcoma. Small noncoding RNAs (sncRNAs) are a class of RNAs that do not encode proteins but directly play biological functions at the RNA level. SncRNAs mainly include Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), small nuclear RNAs (snRNAs), repeat RNAs and microRNAs (miRNAs).

METHODS

In this study, we compared the expression of sncRNAs in BMSCs and osteosarcoma cells by high-throughput sequencing and qPCR and looked for differentially expressed sncRNAs. CCK-8, clone formation and transwell assay were used to detect the effect of sncRNA in MG63 cells.

RESULTS

We found that 66 piRNAs were significantly upregulated and 70 piRNAs were significantly downregulated in MG63 cells. As for snoRNAs, 71 snoRNAs were significantly upregulated and 117 snoRNAs were significantly downregulated in MG63 cells. As for snRNAs, 35 snRNAs were significantly upregulated and 17 snRNAs were significantly downregulated in MG63 cells. As for repeat RNAs, 6 repeat RNAs were significantly upregulated and 7 repeat RNAs were significantly downregulated in MG63 cells. As for miRNAs, 326 miRNAs were significantly upregulated and 281 miRNAs were significantly downregulated in MG63 cells. Overexpression of piRNA DQ596225, snoRNA ENST00000364830.2, snRNA ENST00000410533.1 and miRNA hsa-miR-369-5p inhibited the proliferation and migration of MG63 cells.

CONCLUSIONS

Our results provide a theoretical basis for the pathogenesis, early diagnosis and treatment of osteosarcoma.

EZH2/hSULF1 axis mediates receptor tyrosine kinase signaling to shape cartilage tumor progression

Chondrosarcomas are primary cancers of cartilaginous tissue and capable of alteration to highly aggressive, metastatic, and treatment-refractory states, leading to a poor prognosis with a five-year survival rate at 11 months for dedifferentiated subtype. At present, the surgical resection of chondrosarcoma is the only effective treatment, and no other treatment options including targeted therapies, conventional chemotherapies, or immunotherapies are available for these patients. Here, we identify a signal pathway way involving EZH2/SULF1/cMET axis that contributes to malignancy of chondrosarcoma and provides a potential therapeutic option for the disease. A non-biased chromatin immunoprecipitation sequence, cDNA microarray analysis, and validation of chondrosarcoma cell lines identified sulfatase 1 (SULF1) as the top EZH2-targeted gene to regulate chondrosarcoma progression. Overexpressed EZH2 resulted in downregulation of SULF1 in chondrosarcoma cell lines, which in turn activated cMET pathway. Pharmaceutical inhibition of cMET or genetically silenced cMET pathway significantly retards the chondrosarcoma growth and extends mice survival. The regulation of EZH2/SULF1/cMET axis were further validated in patient samples with chondrosarcoma. The results not only established a signal pathway promoting malignancy of chondrosarcoma but also provided a therapeutic potential for further development of effective target therapy to treat chondrosarcoma.

Imaging Hallmarks of Sarcoma Progression Via X-ray Computed Tomography: Beholding the Flower of Evil

Simple Summary

Sarcomas represent the largest group of rare solid tumors that arise from mesenchymal stem cells and are a leading cause of cancer death in individuals younger than 20 years of age. There is an immediate need for the development of an algorithm for the early accurate diagnosis of sarcomas due to the high rate of diagnostic inaccuracy, which reaches up to 30%. X-ray computed tomography is a non-invasive imaging technique used to obtain detailed internal images of the human or animal body in clinical practice and preclinical studies. We summarized the main imaging features of soft tissue and bone sarcomas, and noted the development of new molecular markers to reach tumor type-specific imaging. Also, we demonstrated the possibility of the use X-ray computed microtomography for non-destructive 3D visualization of sarcoma progression in preclinical studies. Finding correlations between X-ray computed tomography modalities and the results of the histopathological specimen examination may significantly increase the accuracy of diagnostics, which leads to the initiation of appropriate management in a timely manner and, consequently, to improved outcomes.

Abstract

Sarcomas are a leading cause of cancer death in individuals younger than 20 years of age and represent the largest group of rare solid tumors. To date, more than 100 morphological subtypes of sarcomas have been described, among which epidemiology, clinical features, management, and prognosis differ significantly. Delays and errors in the diagnosis of sarcomas limit the number of effective therapeutic modalities and catastrophically worsen the prognosis. Therefore, the development of an algorithm for the early accurate diagnosis of sarcomas seems to be as important as the development of novel therapeutic advances. This literature review aims to summarize the results of recent investigations regarding the imaging of sarcoma progression based on the use of X-ray computed tomography (CT) in preclinical studies and in current clinical practice through the lens of cancer hallmarks. We attempted to summarize the main CT imaging features of soft-tissue and bone sarcomas. We noted the development of new molecular markers with high specificity to antibodies and chemokines, which are expressed in particular sarcoma subtypes to reach tumor type-specific imaging. We demonstrate the possibility of the use of X-ray computed microtomography (micro-CT) for non-destructive 3D visualization of solid tumors by increasing the visibility of soft tissues with X-ray scattering agents. Based on the results of recent studies, we hypothesize that micro-CT enables the visualization of neovascularization and stroma formation in sarcomas at high-resolution in vivo and ex vivo, including the novel techniques of whole-block and whole-tissue imaging. Finding correlations between CT, PET/CT, and micro-CT imaging features, the results of the histopathological specimen examination and clinical outcomes may significantly increase the accuracy of soft-tissue and bone tumor diagnostics, which leads to the initiation of appropriate histotype-specific management in a timely manner and, consequently, to improved outcomes.

Proteomic and Metabolomic Profiling in Soft Tissue Sarcomas

Advances in proteomic and metabolomic technologies have accelerated our understanding of multiple aspects of cancer biology across distinct tumour types. Here we review the current state-of-the-art in the use of proteomics and metabolomics in soft tissue sarcomas. We highlight the utility of these Omics-based methodologies to identify new drug targets, synthetic lethal interactions, candidate therapeutics and novel biomarkers to facilitate patient stratification. Due to the unbiased and global nature of these profiling methods to assess the levels of protein expression, post-translational modifications such as phosphorylation and glycosylation as well as key metabolites, many of these findings have broad applications not just in specific histotypes but across multiple STS subtypes. Specific examples of proteomic and metabolomic findings that have led to the development of early phase clinical trials of investigational agents will be discussed. While promising, the use of these technologies in the study of sarcoma is still limited, and there is a need for further research in this area. In particular, it would be important to integrate these approaches with other Omics strategies such as genomics and epigenomics as well as implement these tools alongside clinical trials in order to maximize the impact of these tools on our biological understanding and treatment of this group of rare diseases of unmet need.

The Effect of miRNA-Modified Exosomes in Animal Models of Spinal Cord Injury: A meta-Analysis

Background: Spinal cord injury (SCI) is currently not completely curable. Exosomes have been widely used in preclinical studies of spinal cord injury. Here, in this meta-analysis, we focused on evaluating the overall efficacy of therapies based on miRNA-modified exosomes on functional recovery in animal models of SCI. Methods: PubMed, embase and Web of Science library databases were searched. Relevant literature was included, and the random effects model was used to assess the overall effect of the intervention, with outcomes expressed as SMD. The primary outcome included motor function scores. Risk of bias (ROB) was assessed using the ROB tool of the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE). R version 4.1.1software and Review Manager software were used for meta-analysis. Results: A total of 11 preclinical studies were included. The meta-analysis revealed that miRNA-modified exosome therapy was effective in improving motor function scores compared with exosomes alone or control therapy (standardized mean difference: 4.21; 95% confidence interval: 3.39-5.04). There was significant asymmetry in the funnel plot, and trim-and-fill analysis revealed four unpublished studies of motor scores. The quality of all included studies was evaluated with SYRCLE's ROB tool. The SCI model, administration time and dose had an impact on the effect of the treatment. Conclusion: MiRNA-modified exosomes have shown great potential in the treatment of SCI. Moreover, the efficacy of miRNA-modified exosomes was superior to that of exosomes alone.

Epithelial and Mesenchymal Markers in Adrenocortical Tissues: How Mesenchymal Are Adrenocortical Tissues?

A clinically relevant proportion of adrenocortical carcinoma (ACC) cases shows a tendency to metastatic spread. The objective was to determine whether the epithelial to mesenchymal transition (EMT), a mechanism associated with metastasizing in several epithelial cancers, might play a crucial role in ACC. 138 ACC, 29 adrenocortical adenomas (ACA), three normal adrenal glands (NAG), and control tissue samples were assessed for the expression of epithelial (E-cadherin and EpCAM) and mesenchymal (N-cadherin, SLUG and SNAIL) markers by immunohistochemistry. Using real-time RT-PCR we quantified the alternative isoform splicing of FGFR 2 and 3, another known indicator of EMT. We also assessed the impact of these markers on clinical outcome. Results show that both normal and neoplastic adrenocortical tissues lacked expression of epithelial markers but strongly expressed mesenchymal markers N-cadherin and SLUG. FGFR isoform splicing confirmed higher similarity of adrenocortical tissues to mesenchymal compared to epithelial tissues. In ACC, higher SLUG expression was associated with clinical markers indicating aggressiveness, while N-cadherin expression inversely associated with these markers. In conclusion, we could not find any indication of EMT as all adrenocortical tissues lacked expression of epithelial markers and exhibited closer similarity to mesenchymal tissues. However, while N-cadherin might play a positive role in tissue structure upkeep, SLUG seems to be associated with a more aggressive phenotype.

Delta-like Factor 1 as a Possible Therapeutic Target for Sarcomas

Backgroud

Cancer stem cells (CSCs) are cells characterized by their self-renewal and tumorigenic potential. The purpose of this study was to discover the role of the delta-like factor 1 (DLK1) in sarcoma.

Methods

mRNA expression of DLK1 from 13 sarcoma cell lines was examined. Isolated CSCs from the tumors were examined using fluorescence-activated cell sorting (FACS) with CD133, the CSC marker, or sphere-forming assay. The relationship between DLK1 and CSCs in sarcoma was examined using cell proliferation and cell invasion assays after they were treated with DLK1 short interfering RNA (siRNA).

Results

A high expression of DLK1 mRNA was observed in all sarcoma cell lines. However, CSCs were isolated from over expressed sarcomas of the DLK1 gene, and they have shown to be expressed lower than the wild type. The anti-cancer effects of DLK1 siRNA inhibited cell proliferation and invasion in U2OS, A204, and sw872. In addition, treatment with DLK1 siRNA inhibited cell invasion in sw872 CSCs. DLK1 gene induces tumorigenesis in various sarcoma cells and regulates the invasiveness of liposarcoma. These results suggest that DLK1 could serve as a possible therapeutic target for sarcoma.

Conclusions

Our study showed that the DLK1 gene induces tumorigenesis in various sarcomas and is associated with invasive mechanism in sarcoma. These results suggest DLK1 could serve as a possible therapeutic target in a variety of sarcomas.

Stem cell derived extracellular vesicles for vascular elastic matrix regenerative repair

Abdominal aortic aneurysms (AAA) are localized expansions of the abdominal aorta that develop due to chronic proteolytic disruption of the structural extracellular matrix (ECM) components (elastin and collagen) within the aorta wall. Major limitations in arresting or reversing AAAs lie in naturally poor and aberrant regeneration and repair of elastic matrix structures in the aorta wall. Bone marrow derived mesenchymal stem cells (BM-MSCs) have emerged as a promising regenerative tool and their therapeutic effects are also known to be effected through their paracrine secretions. Extracellular vesicles (EVs) present in these secretions have emerged as critical cellular component in facilitating many therapeutic benefits of MSCs. EV treatment is thus potentially appealing as a stem cell-inspired cell-free approach to avoid possible phenotypic plasticity of MSCs in vivo. In this study, we investigated the thus far unknown effects of BM-MSC derived EVs on vascular elastic matrix repair in the context of AAA treatment. EVs isolated from BM-MSC source were characterized and their pro-regenerative and their anti-proteolytic effects were evaluated on our established in vitro experimental conditions derived from AAA rat model. Our studies revealed the efficacy of BM-MSC derived EVs in attenuating the proteolytic activity and also in imparting elastic matrix regenerative benefits under aneurysmal environment. Interestingly, compared to cell culture conditioned media (CCM), EVs demonstrated superior regenerative and anti-proteolytic benefits in a proteolytic injury culture model of AAA. From these studies, it appears that EVs derived from BM-MSCs could be beneficial in undertaking a reparative effort in AAA induced degeneration of vascular tissue. Statement of Significance Abdominal aortic aneurysms (AAAs) are localized, rupture-prone expansions of the aorta which result from loss of wall flexibility due to enzymatic breakdown of elastic fibers. There are no established alternatives to surgery, which possess high risk for the mostly elderly patients. Our previous studies have established the elastic regenerative and reparative effect of cell culture secretions derived from adult stem cell source. In this study, we propose to isolate extracellular vesicles (exosomes) from these secretions and evaluate their regenerative benefits in AAA smooth muscle cell culture model. This simple and innovative treatment approach has the potential to arrest or reverse AAA growth to rupture, not possible so far.

Association of Preoperative Neutrophil/Lymphocyte Ratio with Clinical Outcomes in Dedifferentiated Chondrosarcoma Patients

Background

Dedifferentiated chondrosarcoma (DC) is an extremely uncommon malignant bone tumor with dismal survival outcomes. The purpose of this study was to investigate whether the preoperative neutrophil/lymphocyte ratio (NLR) has the ability to predict overall survival (OS) in DC patients.

Materials and Methods

Twenty-three DC patients with surgical resection were retrospectively reviewed between 2008 and 2015. The clinical pathological information and survival data were collected for analysis. The cut-off point for NLR was defined by receiver operating curve (ROC). The impact of NLR level on OS between two groups was compared using Kaplan–Meier curves with the Log-rank test. The association between NLR and OS was calculated by univariate and multivariate Cox proportional models.

Results

From the ROC analysis, the optimal NLR cut-off point was 3.11. Patients with high NLR had a worse OS than low NLR (p = 0.003, Log-rank test). In univariate analysis, a significant association was observed between high NLR and poor OS (Hazard ratio (HR) 4.62, 95% confidence interval (CI) 1.48–14.34, p = 0.008). After adjustment of co-variables, high NLR had more than 4 times the risk of mortality (HR 4.01, 95% CI 1.12–14.26, p = 0.032).

Conclusion

Preoperative NLR in peripheral blood is an easily accessible and cost-effective prognostic biomarker in DC patients. A prospective study with large sample size is warranted.

Molecular Biology of Osteosarcoma

Osteosarcoma (OS) is the most frequent primary bone cancer in children and adolescents and the third most frequent in adults. Many inherited germline mutations are responsible for syndromes that predispose to osteosarcomas including Li Fraumeni syndrome, retinoblastoma syndrome, Werner syndrome, Bloom syndrome or Diamond-Blackfan anemia. TP53 is the most frequently altered gene in osteosarcoma. Among other genes mutated in more than 10% of OS cases, c-Myc plays a role in OS development and promotes cell invasion by activating MEK-ERK pathways. Several genomic studies showed frequent alterations in the RB gene in pediatric OS patients. Osteosarcoma driver mutations have been reported in NOTCH1, FOS, NF2, WIF1, BRCA2, APC, PTCH1 and PRKAR1A genes. Some miRNAs such as miR-21, -34a, -143, -148a, -195a, -199a-3p and -382 regulate the pathogenic activity of MAPK and PI3K/Akt-signaling pathways in osteosarcoma. CD133+ osteosarcoma cells have been shown to exhibit stem-like gene expression and can be tumor-initiating cells and play a role in metastasis and development of drug resistance. Although currently osteosarcoma treatment is based on adriamycin chemoregimens and surgery, there are several potential targeted therapies in development. First of all, activity and safety of cabozantinib in osteosarcoma were studied, as well as sorafenib and pazopanib. Finally, novel bifunctional molecules, of potential imaging and osteosarcoma targeting applications may be used in the future.

Do Mutations Turn p53 into an Oncogene?

The key role of p53 as a tumor suppressor became clear when it was realized that this gene is mutated in 50% of human sporadic cancers, and germline mutations expose carriers to cancer risk throughout their lifespan. Mutations in this gene not only abolish the tumor suppressive functions of p53, but also equip the protein with new pro-oncogenic functions. Here, we review the mechanisms by which these new functions gained by p53 mutants promote tumorigenesis.

Neoplastic Transformation of Human Mesenchymal Stromal Cells Mediated via LIN28B

Bone marrow stromal (Mesenchymal) stem cells (MSCs) are multipotent bone cells capable of differentiating into mesoderm-type cells, such as osteoblasts and adipocytes. Existing evidence suggests that transformation of MSCs gives rise to sarcoma. In order to identify the molecular mechanism leading to spontaneous transformation of human bone marrow MSCs (hBMSCs), we performed comprehensive microRNA (miRNA) and mRNA profiling in the transformed hBMSC-Tum line compared to the parental clone. As a result, we identified multiple dysregulated molecular networks associated with the hBMSC transformed phenotype. LIN28B was upregulated 177.0-fold in hBMSC-Tum, which was associated with marked reduction in LET-7 expression and upregulated expression of its target HMGA2. Targeted depletion of LIN28B or exogenous expression of LET-7b suppressed hBMSC-Tum proliferation, colony formation, and migration. On the other hand, forced expression of LIN28B promoted malignant transformation of parental hBMSC cells as shown by enhanced in vitro colony formation, doxorubicin resistance, and in vivo tumor formation in immunocompromised mice. Analysis of LIN28B and HMGA2 expression levels in cohorts from The Cancer Genome Atlas sarcoma dataset revealed a strong inverse-relationship between elevated expression and overall survival (OS) in 260 patients (p = 0.005) and disease-free survival (DFS) in 231 patients (p = 0.02), suggesting LIN28B and HMGA2 are important regulators of sarcoma biology. Our results highlight an important role for the LIN28B/LET-7 axis in human sarcoma pathogenesis and suggest that the therapeutic targeting of LIN28B may be relevant for patients with sarcoma.

The Human IL-23 Decoy Receptor Inhibits T-Cells Producing IL-17 by Genetically Engineered Mesenchymal Stem Cells

The immunomodulatory and self-renewable features of human adipose mesenchymal stem cells (hAD-MSCs) mark their importance in regenerative medicine. Interleukin 23 (IL- 23) as a proinflammatory cytokine suppresses T regulatory cells (Treg) and promotes the response of T helper 17 (Th17) and T helper 1 (Th1) cells. This pathway starts inflammation and immunosuppression in several autoimmune diseases. The current study for producing recombinant IL- 23 decoy receptor (RIL- 23R) using hAD-MSCs as a good candidate for ex vivo cell-based gene therapy purposes reducing inflammation in autoimmune diseases. hAD-MSCs was isolated from lipoaspirate and then characterized by differentiation. RIL- 23R was designed and cloned into a pCDH-813A- 1 lentiviral vector. The transduction of hAD-MSCs was performed at MOI (multiplicity of infection) = 50 with pCDH- EFI α- RIL- 23R- PGK copGFP. Expressions of RIL- 23R and octamer-binding transcription factor 4 (OCT- 4) were determined by real-time polymerase chain reaction (real time-PCR). Self-renewing properties were assayed with OCT- 4. Bioactivity of the designed RIL- 23R was evaluated by IL- 17 and IL- 10 expression of mouse splenocytes. Cell differentiation confirmed the true isolation of hAD-MSCs from lipoaspirate. Restriction of the enzyme digestion and sequencing verified the successful cloning of RIL- 23R in the CD813A-1 lentiviral vector. The green fluorescent protein (GFP) positive transduction rate was up to 90%, and real-time PCR showed the expression level of RIL-23R. Oct-4 had a similar expression pattern with nontransduced hAD-MSCs and transduced hAD-MSCs/ RIL-23R indicating that lentiviral vector did not affect hAD-MSCs characteristics. Downregulation of IL-17 and upregulation of IL-10 showed the correct activity of the engineered hAD-MSCs. The results showed that the transduced hAD-MSCs/ RIL- 23R, expressing IL-23 decoy receptor, can give a useful approach for a basic research on cell-based gene therapy for autoimmune disorders.

Non-invasive imaging reveals conditions that impact distribution and persistence of cells after in vivo administration

Background

Cell-based regenerative medicine therapies are now frequently tested in clinical trials. In many conditions, cell therapies are administered systemically, but there is little understanding of their fate, and adverse events are often under-reported. Currently, it is only possible to assess safety and fate of cell therapies in preclinical studies, specifically by monitoring animals longitudinally using multi-modal imaging approaches. Here, using a suite of in vivo imaging modalities to explore the fate of a range of human and murine cells, we investigate how route of administration, cell type and host immune status affect the fate of administered cells.

Methods

We applied a unique imaging platform combining bioluminescence, optoacoustic and magnetic resonance imaging modalities to assess the safety of different human and murine cell types by following their biodistribution and persistence in mice following administration into the venous or arterial system.

Results

Longitudinal imaging analyses (i) suggested that the intra-arterial route may be more hazardous than intravenous administration for certain cell types, (ii) revealed that the potential of a mouse mesenchymal stem/stromal cell (MSC) line to form tumours depended on administration route and mouse strain and (iii) indicated that clinically tested human umbilical cord (hUC)-derived MSCs can transiently and unexpectedly proliferate when administered intravenously to mice.

Conclusions

In order to perform an adequate safety assessment of potential cell-based therapies, a thorough understanding of cell biodistribution and fate post administration is required. The non-invasive imaging platform used here can expose not only the general organ distribution of these therapies, but also a detailed view of their presence within different organs and, importantly, tumourigenic potential. Our observation that the hUC-MSCs but not the human bone marrow (hBM)-derived MSCs persisted for a period in some animals suggests that therapies with these cells should proceed with caution.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1076-x) contains supplementary material, which is available to authorized users.

Soft Tissue Sarcoma Cancer Stem Cells: An Overview

Soft tissue sarcomas (STSs) are an uncommon group of solid tumors that can arise throughout the human lifespan. Despite their commonality as non-bony cancers that develop from mesenchymal cell precursors, they are heterogeneous in their genetic profiles, histology, and clinical features. This has made it difficult to identify a single target or therapy specific to STSs. And while there is no one cell of origin ascribed to all STSs, the cancer stem cell (CSC) principle—that a subpopulation of tumor cells possesses stem cell-like properties underlying tumor initiation, therapeutic resistance, disease recurrence, and metastasis—predicts that ultimately it should be possible to identify a feature common to all STSs that could function as a therapeutic Achilles' heel. Here we review the published evidence for CSCs in each of the most common STSs, then focus on the methods used to study CSCs, the developmental signaling pathways usurped by CSCs, and the epigenetic alterations critical for CSC identity that may be useful for further study of STS biology. We conclude with discussion of some challenges to the field and future directions.

Mouse genetic background influences whether HrasG12V expression plus Cdkn2a knockdown causes angiosarcoma or undifferentiated pleomorphic sarcoma

Soft tissue sarcomas are rare mesenchymal tumours accounting for 1% of adult malignancies and are fatal in approximately one third of patients. Two of the most aggressive and lethal forms of soft tissue sarcomas are angiosarcomas and undifferentiated pleomorphic sarcomas (UPS). To examine sarcoma-relevant molecular pathways, we employed a lentiviral gene regulatory system to attempt to generate in vivo models that reflect common molecular alterations of human angiosarcoma and UPS. Mice were intraveneously injected with MuLE lentiviruses expressing combinations of shRNA against Cdkn2a, Trp53, Tsc2 and Pten with or without expression of HrasG12V , PIK3CAH1047R or Myc. The systemic injection of an ecotropic lentivirus expressing oncogenic HrasG12V together with the knockdown of Cdkn2a or Trp53 was sufficient to initiate angiosarcoma and/or UPS development, providing a flexible system to generate autochthonous mouse models of these diseases. Unexpectedly, different mouse strains developed different types of sarcoma in response to identical genetic drivers, implicating genetic background as a contributor to the genesis and spectrum of sarcomas.

Sarcoma Spheroids and Organoids-Promising Tools in the Era of Personalized Medicine

Cancer treatment is rapidly evolving toward personalized medicine, which takes into account the individual molecular and genetic variability of tumors. Sophisticated new in vitro disease models, such as three-dimensional cell cultures, may provide a tool for genetic, epigenetic, biomedical, and pharmacological research, and help determine the most promising individual treatment. Sarcomas, malignant neoplasms originating from mesenchymal cells, may have a multitude of genomic aberrations that give rise to more than 70 different histopathological subtypes. Their low incidence and high level of histopathological heterogeneity have greatly limited progress in their treatment, and trials of clinical sarcoma are less frequent than trials of other carcinomas. The main advantage of 3D cultures from tumor cells or biopsy is that they provide patient-specific models of solid tumors, and they overcome some limitations of traditional 2D monolayer cultures by reflecting cell heterogeneity, native histologic architectures, and cell-extracellular matrix interactions. Recent advances promise that these models can help bridge the gap between preclinical and clinical research by providing a relevant in vitro model of human cancer useful for drug testing and studying metastatic and dormancy mechanisms. However, additional improvements of 3D models are expected in the future, specifically the inclusion of tumor vasculature and the immune system, to enhance their full ability to capture the biological features of native tumors in high-throughput screening. Here, we summarize recent advances and future perspectives of spheroid and organoid in vitro models of rare sarcomas that can be used to investigate individual molecular biology and predict clinical responses. We also highlight how spheroid and organoid culture models could facilitate the personalization of sarcoma treatment, provide specific clinical scenarios, and discuss the relative strengths and limitations of these models.

Dysregulation of macrophage polarization is associated with the metastatic process in osteosarcoma

Osteosarcoma (OS) is the most common bone sarcoma in adolescents, and has poor prognosis. A vicious cycle is established between OS cells and their microenvironment in order to facilitate the tumor growth and cell spreading. The present work aims to better characterize the tumor microenvironment in OS in order to identify new therapeutic targets relating to metastatic process. Tissue microarrays of pre-chemotherapy OS biopsies were used for characterizing the tumor niche by immunohistochemistry. Parameters studies included: immune cells (M1, M2-subtypes of tumor-associated macrophages (TAM); T, B lymphocytes; mast cells), vascularization (endothelial, perivascular cells), OPG, RANKL, and mitotic index. Two groups of patients were defined, 22 localized OS (OS Meta-) and 28 metastatic OS (OS Meta+). The OS Meta- group was characterized by a higher infiltration of INOS+ M1-polarizedmacrophages and upregulated OPG immunostaining. OS Meta+ tumors showed a significant increase in CD146+ cells. INOS+ M1-macrophages were correlated with OPG staining, and negatively with the presence of metastases. CD163+ M2-macrophages were positively correlated with CD146+ cells. In multivariate analysis, INOS and OPG were predictive factors for metastasis. An older age, non-metastatic tumor, good response to chemotherapy, and higher macrophage infiltration were significantly associated with better overall survival. TAMs are associated with better overall survival and a dysregulation of M1/M2 polarized-macrophages in favor of M1 subtype was observed in non-metastatic OS.

Biology of Bone Sarcomas and New Therapeutic Developments

Bone sarcomas are tumours belonging to the family of mesenchymal tumours and constitute a highly heterogeneous tumour group. The three main bone sarcomas are osteosarcoma, Ewing sarcoma and chondrosarcoma each subdivided in diverse histological entities. They are clinically characterised by a relatively high morbidity and mortality, especially in children and adolescents. Although these tumours are histologically, molecularly and genetically heterogeneous, they share a common involvement of the local microenvironment in their pathogenesis. This review gives a brief overview of their specificities and summarises the main therapeutic advances in the field of bone sarcoma.

In vitro and in vivo characterization of stem-like cells from canine osteosarcoma and assessment of drug sensitivity

Cancer stem cell (CSC) self-renewing and drug resistance cause treatment failure and tumor recurrence. Osteosarcoma is an aggressive bone tumor characterized by biological and molecular heterogeneity, possibly dependent on CSCs. CSC identification in osteosarcoma and their efficient targeting are still open questions. Spontaneous canine osteosarcoma shares clinical and biological features with the human tumors, representing a model for translational studies. We characterized three CSC-enriched canine osteosarcoma cultures. In serum-free conditions, these CSC cultures grow as anchorage-independent spheroids, show mesenchymal-like properties and in vivo tumorigenicity, recapitulating the heterogeneity of the original osteosarcoma. Osteosarcoma CSCs express stem-related factors (Sox2, Oct4, CD133) and chemokine receptors and ligands (CXCR4, CXCL12) involved in tumor proliferation and self-renewal. Standard drugs for osteosarcoma treatment (doxorubicin and cisplatin) affected CSC-enriched and parental primary cultures, showing different efficacy within tumors. Moreover, metformin, a type-2 diabetes drug, significantly inhibits osteosarcoma CSC viability, migration and self-renewal and, in co-treatment with doxorubicin and cisplatin, enhances drug cytotoxicity. Collectively, we demonstrate that canine osteosarcoma primary cultures contain CSCs exhibiting distinctive sensitivity to anticancer agents, as a reliable experimental model to assay drug efficacy. We also provide proof-of-principle of metformin efficacy, alone or in combination, as pharmacological strategy to target osteosarcoma CSCs.

Mesenchymal stromal cell engagement in cancer cell epithelial to mesenchymal transition

Due to coexistence of stromal and epithelial tumor cells, their dynamic interactions have been widely recognized as significant cellular components to the tumor tissue integrity. Initiation and outcome of epithelial to mesenchymal transition (EMT) in tumor cells are dependent on their interaction with adjacent or recruited mesenchymal stromal cells (MSCs). A plethora of mechanisms are involved in MSCs-controlled employment of the developmental processes of EMT that contribute to loss of epithelial cell phenotype and acquisition of stemness, invasiveness and chemoresistance of tumor cells. Interplay of MSCs with tumor cells, including interchange of soluble biomolecules, plasma membrane structures, cytoplasmic content, and organelles, is established through cell-cell contact and/or by means of paracrine signaling. The main focus of this review is to summarize knowledge about involvement of MSCs in cancer cell EMT. Understanding the underlying cellular and molecular mechanism involved in the interplay between MSCs and cancer EMT is essential for development of effective therapy approaches, which in combination with current treatments may improve the control of tumor progression. Developmental Dynamics 247:359-367, 2018. © 2017 Wiley Periodicals, Inc.

Three-Dimensional Patient-Derived In Vitro Sarcoma Models: Promising Tools for Improving Clinical Tumor Management

Over the past decade, the development of new targeted therapeutics directed against specific molecular pathways involved in tumor cell proliferation and survival has allowed an essential improvement in carcinoma treatment. Unfortunately, the scenario is different for sarcomas, a group of malignant neoplasms originating from mesenchymal cells, for which the main therapeutic approach still consists in the combination of surgery, chemotherapy, and radiation therapy. The lack of innovative approaches in sarcoma treatment stems from the high degree of heterogeneity of this tumor type, with more that 70 different histopathological subtypes, and the limited knowledge of the molecular drivers of tumor development and progression. Currently, molecular therapies are available mainly for the treatment of gastrointestinal stromal tumor, a soft-tissue malignancy characterized by an activating mutation of the tyrosine kinase KIT. Since the first application of this approach, a strong effort has been made to understand sarcoma molecular alterations that can be potential targets for therapy. The low incidence combined with the high level of histopathological heterogeneity makes the development of clinical trials for sarcomas very challenging. For this reason, preclinical studies are needed to better understand tumor biology with the aim to develop new targeted therapeutics. Currently, these studies are mainly based on in vitro testing, since cell lines, and in particular patient-derived models, represent a reliable and easy to handle tool for investigation. In the present review, we summarize the most important models currently available in the field, focusing in particular on the three-dimensional spheroid/organoid model. This innovative approach for studying tumor biology better represents tissue architecture and cell–cell as well as cell–microenvironment crosstalk, which are fundamental steps for tumor cell proliferation and survival.

Photochemical internalization (PCI) of bleomycin is equally effective in two dissimilar leiomyosarcoma xenografts in athymic mice

BACKGROUND

Photochemical internalization (PCI) is a novel technique for delivery of active macromolecules into cancerous cells, via light activation of a specific photosensitizer and a low dose systemic drug. Numerous pre-clinical studies and one clinical trial have confirmed the treatment potential in carcinomas. Soft tissue sarcomas are rare and generally resistant to radio- and chemotherapy. Due to treatment resistance and surgical morbidity in sarcoma care, we seek to increase knowledge on PCI effects in sarcomas by studying two different, but closely related leiomyosarcomas.

METHODS

MES-SA and SK-LMS-1 tumours were established in the leg muscles of athymic mice. Treatment effects after AlPcS_2a-PCI of bleomycin, PCI with no drug (photodynamic therapy, PDT) and control groups were evaluated by: 1) assessment of tumour growth, 2) uptake of contrast agent during MRI and 3) histopathology.

RESULTS

PCI of bleomycin induced a similar and significant increase in time to reach the end point in both tumour models, while neither responded to AlPcS_2a-PDT. In the MES-SA tumours PCI reduced the growth rate, while in the SK-LMS-1 tumours the growth was blocked for 12days followed by exponential growth close to that of untreated tumours. SK-LMS-1 tumours were more homogenously and better vascularized than MES-SA. After PCI the vascular shutdown was more complete in the SK-LMS-1 tumours than in the MES-SA tumours.

CONCLUSIONS

AlPcS2a-based PCI, but not PDT, induced significant tumour growth delay in the evaluated sarcomas. Cellular responsiveness to bleomycin and tumour vascularity are identified as predictive markers for PCI treatment effects.

Orthopaedic tumors: What problems are we solving, and are universities and major medical centers doing enough?

Little has been published about the complexity of orthopaedic tumors compared to others tumors. The current study in the literature treated this problem in terms of classification, surgical intervention and impact on the patient. In this article, factors risks of tumors will be we identified. A strategy based on three dimensional simulations will be explained in order to improve the clinical trials.

Dedifferentiated chondrosarcoma: Radiological features, prognostic factors and survival statistics in 23 patients

Background

Dedifferentiated chondrosarcoma is a rare, highly malignant tumor with a poor survival. There are many confusing issues concerning the imaging feature that can facilitate early diagnosis and the factors that might be related to outcomes.

Methods

Twenty-three patients with dedifferentiated chondrosarcoma confirmed by pathology were retrospectively reviewed from 2008 to 2015. The patients’ clinical information, images from radiographs (n = 17), CT (n = 19), and MRI (n = 17), histological features, treatment and prognosis were analyzed.

Results

There were 12 males and 11 females, and the mean age was 50.39 years old. Fourteen cases affected the axial bone (pelvis, spine), and 9 cases involved the appendicular bone. Seven (41.17%), 9 (47.36), and 12 (66.66%) lesions showed a biphasic nature on radiograph, CT and MRI, respectively. Of the lesions, 17.39% (4/23) were accompanied by pathological fractures. Histologically, the cartilage component was considered histological Grade1 in 12 patients and Grade 2 in 11 patients. The dedifferentiated component showed features of osteosarcoma in 8 cases, malignant fibrous histiocytoma in3 cases, myofibroblastic sarcoma in 1 case and spindle cell sarcoma in 11cases. Twenty-two cases were treated with surgical resection, and 17 cases achieved adequate (wide or radical) surgical margin. In 8 cases, surgery was combined with adjuvant chemotherapy. The overall median survival time was nine months; 17.4% of patients survived to five years.

Conclusion

Axial bone location, lung metastasis at diagnosis, inadequate surgical margin, incorrect diagnosis before surgery and pathological fractures was related to poorer outcome. Pre- or postoperative chemotherapy had no definitively effect on improved survival.

Genetically transforming human osteoblasts to sarcoma: development of an osteosarcoma model

Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Although histologically defined by the presence of malignant osteoid, the tumor possesses lineage multipotency suggesting it could be derived from a cell anywhere on the differentiation pathway between a mesenchymal stem cell (MSC) and a mature osteoblast. To determine if preosteoblasts (pOB) could be the cell of origin differentiated MSCs were transformed with defined genetic elements. MSCs and pOB differentiated from the same MSCs were serially transformed with the oncogenes hTERT, SV40 large T antigen and H-Ras. Assays were performed to determine their tumorigenic properties, differentiation capacity and histologic appearance. When subcutaneously implanted in immunocompromised mice, cell lines derived from transformed MSC and pOB formed tumors in 4 weeks. In contrast to the transformed MSC, the pOB tumors demonstrated a histological appearance characteristic of osteosarcoma. The cell lines derived from the transformed pOB only had osteogenic and chondrogenic differentiation potential, but not adipogenic ones. However, the transformed MSC cells and standard osteosarcoma cell lines maintained their tri-lineage differentiation capacity. The inability of the transformed pOB cell line to undergo adipogenic differentiation, may suggest that osteosarcoma is derived from a cell intermediate in differentiation between an MSC and a pOB, with partial commitment to the osteoblastic lineage.

A novel rat fibrosarcoma cell line from transformed bone marrow-derived mesenchymal stem cells with maintained in vitro and in vivo stemness properties

Increasing evidence suggests a possible relationship between mesenchymal stem cells (MSCs) and sarcoma. MSCs are hypothesized to be the cells initiating sarcomagenesis, and cancer stem cells (CSCs) sharing features of MSCs have been identified in sarcomas. Here, we report on the characteristics of a bone marrow-derived rat mesenchymal stem cell line that spontaneously transformed in long-term culture. The rat transformed mesenchymal stem cells (rTMSCs) produced soft-tissue fibrosarcomas in immunocompromised mice and immunocompetent rats. In vitro, the rTMSCs displayed increased proliferation capacity compared to the untransformed cell line. The transformed MSCs maintained the mesenchymal phenotype by expression of the stem cell marker CD 90 and the lack of hematopoietic and endothelial markers. Cytogenetic analysis detected trisomy 6 in the rTMSCs. Side population (SP) isolation and tumorsphere cultivation of the transformed cells confirmed the presence of CSCs among the rTMSCs. Importantly, the rTMSCs retained their differentiation capacity towards osteogenic and adipogenic lineages. This transformed MSC-based cell line may be valuable in examining the balance in a mixed cell population between cancer stem cell properties and the ability to differentiate to specific non-transformed cell populations. Moreover, it may also be a useful tool to evaluate the efficacy of novel targeted immunotherapies in vivo.

Oncogenic Mutant p53 Gain of Function Nourishes the Vicious Cycle of Tumor Development and Cancer Stem-Cell Formation

More than half of human tumors harbor an inactivated p53 tumor-suppressor gene. It is well accepted that mutant p53 shows an oncogenic gain-of-function (GOF) activity that facilitates the transformed phenotype of cancer cells. In addition, a growing body of evidence supports the notion that cancer stem cells comprise a seminal constituent in the initiation and progression of cancer development. Here, we elaborate on the mutant p53 oncogenic GOF leading toward the acquisition of a transformed phenotype, as well as placing mutant p53 as a major component in the establishment of cancer stem cell entity. Therefore, therapy targeted toward cancer stem cells harboring mutant p53 is expected to pave the way to eradicate tumor growth and recurrence.

Generation of Osteosarcomas from a Combination of Rb Silencing and c-Myc Overexpression in Human Mesenchymal Stem Cells

Osteosarcoma (OS) was a malignant tumor occurring with unknown etiology that made prevention and early diagnosis difficult. Mesenchymal stem cells (MSCs), which were found in bone marrow, were claimed to be a possible origin of OS but with little direct evidence. We aimed to characterize OS cells transformed from human MSCs (hMSCs) and identify their association with human primary OS cells and patient survival. Genetic modification with p53 or retinoblastoma (Rb) knockdown and c-Myc or Ras overexpression was applied for hMSC transformation. Transformed cells were assayed for proliferation, differentiation, tumorigenecity, and gene expression profile. Only the combination of Rb knockdown and c-Myc overexpression successfully transformed hMSCs derived from four individual donors, with increasing cell proliferation, decreasing cell senescence rate, and increasing ability to form colonies and spheres in serum-free medium. These transformed cells lost the expression of certain surface markers, increased in osteogenic potential, and decreased in adipogenic potential. After injection in immunodeficient mice, these cells formed OS-like tumors, as evidenced by radiographic analyses and immunohistochemistry of various OS markers. Microarray with cluster analysis revealed that these transformed cells have gene profiles more similar to patient-derived primary OS cells than their normal MSC counterparts. Most importantly, comparison of OS patient tumor samples revealed that a combination of Rb loss and c-Myc overexpression correlated with a decrease in patient survival. This study successfully transformed human MSCs to OS-like cells by Rb knockdown and c-Myc overexpression that may be a useful platform for further investigation of preventive and target therapy for human OS. Stem Cells Translational Medicine 2017;6:512-526.

Cultured circulating tumor cells and their derived xenografts for personalized oncology

Recent cancer research has demonstrated the existence of circulating tumor cells (CTCs) in cancer patient's blood. Once identified, CTC biomarkers will be invaluable tools for clinical diagnosis, prognosis and treatment. In this review, we propose ex vivo culture as a rational strategy for large scale amplification of the limited numbers of CTCs from a patient sample, to derive enough CTCs for accurate and reproducible characterization of the biophysical, biochemical, gene expressional and behavioral properties of the harvested cells. Because of tumor cell heterogeneity, it is important to amplify all the CTCs in a blood sample for a comprehensive understanding of their role in cancer metastasis. By analyzing critical steps and technical issues in ex vivo CTC culture, we developed a cost-effective and reproducible protocol directly culturing whole peripheral blood mononuclear cells, relying on an assumed survival advantage in CTCs and CTC-like cells over the normal cells to amplify this specified cluster of cancer cells.

A porcine model of osteosarcoma

We previously produced pigs with a latent oncogenic TP53 mutation. Humans with TP53 germline mutations are predisposed to a wide spectrum of early-onset cancers, predominantly breast, brain, adrenal gland cancer, soft tissue sarcomas and osteosarcomas. Loss of p53 function has been observed in >50% of human cancers. Here we demonstrate that porcine mesenchymal stem cells (MSCs) convert to a transformed phenotype after activation of latent oncogenic TP53^R167H and KRAS^G12D, and overexpression of MYC promotes tumorigenesis. The process mimics key molecular aspects of human sarcomagenesis. Transformed porcine MSCs exhibit genomic instability, with complex karyotypes, and develop into sarcomas on transplantation into immune-deficient mice. In pigs, heterozygous knockout of TP53 was sufficient for spontaneous osteosarcoma development in older animals, whereas homozygous TP53 knockout resulted in multiple large osteosarcomas in 7–8-month-old animals. This is the first report that engineered mutation of an endogenous tumour-suppressor gene leads to invasive cancer in pigs. Unlike in Trp53 mutant mice, osteosarcoma developed in the long bones and skull, closely recapitulating the human disease. These animals thus promise a model for juvenile osteosarcoma, a relatively uncommon but devastating disease.

Asymmetric aneuploidy in mesenchymal stromal cells detected by in situ karyotyping and fluorescence in situ hybridization: suggestions for reference values for stem cells

Cytogenetic testing is important to ensure patient safety before therapeutic application of mesenchymal stromal cells (MSCs). However, the standardized methods and criteria for the screening of chromosomal abnormalities of MSCs have not yet been determined. We investigated the frequency of cytogenetic aberrations in MSCs using G-banding and fluorescence in situ hybridization (FISH) and suggest reference values for aneuploidy in MSCs. Cytogenetic analysis was performed on 103 consecutive cultures from 68 MSCs (25 adipose-origin, 20 bone marrow-origin, 18 cord blood-origin, and 5 neural stem cells; 8 from adipose tissue of patients with breast cancer and 60 from healthy donors). We compared the MSC aneuploidy patterns with those of hematological malignancies and benign hematological diseases. Interphase FISH showed variable aneuploid clone proportions (1%-20%) in 68 MSCs. The aneuploidy patterns were asymmetric, and aneuploidy of chromosomes 16, 17, 18, and X occurred most frequently. Clones with polysomy were significantly more abundant than those with monosomy. The cutoff value of maximum polysomy rates (upper 95th percentile value) was 13.0%. By G-banding, 5 of the 61 MSCs presented clonal chromosomal aberrations. Aneuploidy was asymmetric in the malignant hematological diseases, while it was symmetric in the benign hematological diseases. We suggest an aneuploidy cutoff value of 13%, and FISH for aneuploidy of chromosomes 16, 17, 18, and X would be informative to evaluate the genetic stability of MSCs. Although it is unclear whether the aneuploid clones might represent the senescent cell population or transformed cells, more attention should be focused on the safety of MSCs, and G-banding combined with FISH should be performed.

Cancer-associated mesenchymal stem cells aggravate tumor progression

Mesenchymal stem cells (MSCs) have both stemness and multi-modulatory activities on other cells, and the immunosuppressive and tumor-promotive mechanisms have been intensively investigated in cancer. The role of MSCs appears to be revealed in tumor aggravation, and targeting MSCs seems to be a promising strategy for treating cancer patients. However, it is still impractical in clinical therapy, since the precise MSCs are poorly understood in the in vivo setting. In previous studies, MSCs were obtained from different sources, and were prepared by ex vivo expansion for a long term. The inconsistent experimental conditions made the in vivo MSCs obscure. To define the MSCs in the host is a priority issue for targeting MSCs in cancer therapy. We recently identified a unique subpopulation of MSCs increasing in mice and human with cancer metastasis. These MSCs are specifically expanded by metastatic tumor cells, and promote tumor progression and dissemination accompanied by immune suppression and dysfunction in the host, more powerfully than normal MSCs growing without interference of cancer. In this review, we summarize current knowledge of the role of MSCs in tumor aggravation, along with our new findings of the bizarre MSCs.

A genetic platform to model sarcomagenesis from primary adult mesenchymal stem cells

The regulatory factors governing adult mesenchymal stem cell (MSC) physiology and their tumorigenic potential are still largely unknown, which substantially delays the identification of effective therapeutic approaches for the treatment of aggressive and lethal forms of MSC-derived mesenchymal tumors, such as undifferentiated sarcomas. Here, we have developed a novel platform to screen and quickly identify genes and pathways responsible for adult MSC transformation, modeled undifferentiated sarcoma in vivo, and, ultimately, tested the efficacy of targeting the identified oncopathways. Importantly, by taking advantage of this new platform, we demonstrate the key role of an aberrant LRF-DLK1-SOX9 pathway in the pathogenesis of undifferentiated sarcoma, with important therapeutic implications.

SIGNIFICANCE

The paucity of therapeutic options for the treatment of sarcoma calls for a rapid and effective preclinical assessment of new therapeutic modalities. We have here developed a new platform to deconstruct the molecular genetics underlying the pathogenesis of sarcoma and to evaluate in vivo the efficacy of novel targeted therapies.

The role of mesenchymal stem/progenitor cells in sarcoma: update and dispute

Sarcoma is the collective name for a relatively rare, yet heterogeneous group of cancers, most probably derived from mesenchymal tissues. There are currently over 50 sarcoma subtypes described underscoring the clinical and biologic diversity of this group of malignant cancers. This wide lineage range might suggest that sarcomas originate from either many committed different cell types or from a multipotent cell. Mesenchymal stem/progenitor cells (MSCs) are able to differentiate into many cell types and these multipotent cells have been isolated from several adult human tumors, making them available for research as well as potential beneficial therapeutical agents. Recent accomplishments in the field have broadened our knowledge of MSCs in relation to sarcoma origin and sarcoma treatment in therapeutic settings. However, numerous concerns and disputes have been raised about whether they are the putative originating cells of sarcoma and their questionable role in sarcomagenesis and progression. We summarize the update and dispute about MSC investigations in sarcomas including the definition, cell origin hypothesis, functional and descriptive assays, roles in sarcomagenesis and targeted therapy, with the purpose to give a comprehensive view of the role of MSCs in sarcomas.

Human bone marrow stromal cells lose immunosuppressive and anti-inflammatory properties upon oncogenic transformation

Because of their immunomodulatory properties, human bone marrow stromal cells (hBMSCs) represent promising stem cells for treatment of immune disorders. hBMSCs expansion precedes their clinical use, so the possibility that hBMSCs undergo spontaneous transformation upon long-term culture should be addressed. Whether hBMSCs retain immunosuppressive and anti-inflammatory properties upon oncogenic transformation remains unknown. Using sequentially mutated hBMSCs and spontaneously transformed hBMSCs, we report that, upon oncogenic transformation, hBMSCs lose immunosuppressive and anti-inflammatory properties in vitro and in vivo. Transcriptome profiling and functional assays reveal immune effectors underlying the loss of immunomodulation in transformed hBMSCs. They display a proinflammatory transcriptomic signature, with deregulation of immune and inflammatory modulators and regulators of the prostaglandin synthesis. Transformed hBMSCs lose their capacity to secrete the immunosuppressive prostacyclins prostaglandin E2 (PGE2) and PGI2 but produce proinflammatory thromboxanes. Together, the immunoregulatory profile adopted by hBMSCs largely depends on intrinsic genetic-molecular determinants triggered by genomic instability/oncogenic transformation.

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Oncogenic hBMSCs display robustly impaired immune properties

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Transformed hBMSCs display a proinflammatory transcriptomic signature

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Transformed hBMSCs lose capacity to secrete immunosuppressive prostacyclins

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Transformed hBMSCs gain the capacity to produce proinflammatory thromboxanes

Senescence bypass in mesenchymal stem cells: a potential pathogenesis and implications of pro-senescence therapy in sarcomas

Cellular senescence is a mechanism that limits the lifespan of somatic cells as the results of replicative proliferation and response to stresses, and that prevents undesired oncogenic changes constituting a barrier against immortalization and tumorigenesis. Mesenchymal stem cells (MSCs) reside in a variety of tissues, and participates in tissue maintenance with their multipotent differentiation ability. MSCs are also considered to be as cells of origin for certain type of sarcomas. We reviewed the mechanisms of cellular senescence in MSCs and hypothesized senescence bypass as the potential pathogenesis for sarcoma development, and proposed the possibility of senescence induction therapy for an alternative treatment strategy against sarcomas, especially cells with the resistance to conventional chemo and radiotherapy including sarcoma stem cells.

Imatinib mesylate exerts anti-proliferative effects on osteosarcoma cells and inhibits the tumour growth in immunocompetent murine models

Osteosarcoma is the most common primary malignant bone tumour characterized by osteoid production and/or osteolytic lesions of bone. A lack of response to chemotherapeutic treatments shows the importance of exploring new therapeutic methods. Imatinib mesylate (Gleevec, Novartis Pharma), a tyrosine kinase inhibitor, was originally developed for the treatment of chronic myeloid leukemia. Several studies revealed that imatinib mesylate inhibits osteoclast differentiation through the M-CSFR pathway and activates osteoblast differentiation through PDGFR pathway, two key cells involved in the vicious cycle controlling the tumour development. The present study investigated the in vitro effects of imatinib mesylate on the proliferation, apoptosis, cell cycle, and migration ability of five osteosarcoma cell lines (human: MG-63, HOS; rat: OSRGA; mice: MOS-J, POS-1). Imatinib mesylate was also assessed as a curative and preventive treatment in two syngenic osteosarcoma models: MOS-J (mixed osteoblastic/osteolytic osteosarcoma) and POS-1 (undifferentiated osteosarcoma). Imatinib mesylate exhibited a dose-dependent anti-proliferative effect in all cell lines studied. The drug induced a G0/G1 cell cycle arrest in most cell lines, except for POS-1 and HOS cells that were blocked in the S phase. In addition, imatinib mesylate induced cell death and strongly inhibited osteosarcoma cell migration. In the MOS-J osteosarcoma model, oral administration of imatinib mesylate significantly inhibited the tumour development in both preventive and curative approaches. A phospho-receptor tyrosine kinase array kit revealed that PDGFRα, among 7 other receptors (PDFGFRβ, Axl, RYK, EGFR, EphA2 and 10, IGF1R), appears as one of the main molecular targets for imatinib mesylate. In the light of the present study and the literature, it would be particularly interesting to revisit therapeutic evaluation of imatinib mesylate in osteosarcoma according to the tyrosine-kinase receptor status of patients.

p53: the barrier to cancer stem cell formation

The role of p53 as the "guardian of the genome" in differentiated somatic cells, triggering various biological processes, is well established. Recent studies in the stem cell field have highlighted a profound role of p53 in stem cell biology as well. These studies, combined with basic data obtained 20 years ago, provide insight into how p53 governs the quantity and quality of various stem cells, ensuring a sufficient repertoire of normal stem cells to enable proper development, tissue regeneration and a cancer free life. In this review we address the role of p53 in genomically stable embryonic stem cells, a unique predisposed cancer stem cell model and adult stem cells, its role in the generation of induced pluripotent stem cells, as well as its role as the barrier to cancer stem cell formation.

Identification of three molecular and functional subtypes in canine hemangiosarcoma through gene expression profiling and progenitor cell characterization

Canine hemangiosarcomas have been ascribed to an endothelial origin based on histologic appearance; however, recent findings suggest that these tumors may arise instead from hematopoietic progenitor cells. To clarify this ontogenetic dilemma, we used genome-wide expression profiling of primary hemangiosarcomas and identified three distinct tumor subtypes associated with angiogenesis (group 1), inflammation (group 2), and adipogenesis (group 3). Based on these findings, we hypothesized that a common progenitor may differentiate into the three tumor subtypes observed in our gene profiling experiment. To investigate this possibility, we cultured hemangiosarcoma cell lines under normal and sphere-forming culture conditions to enrich for tumor cell progenitors. Cells from sphere-forming cultures displayed a robust self-renewal capacity and exhibited genotypic, phenotypic, and functional properties consistent with each of the three molecular subtypes seen in primary tumors, including expression of endothelial progenitor cell (CD133 and CD34) and endothelial cell (CD105, CD146, and αvβ3 integrin) markers, expression of early hematopoietic (CD133, CD117, and CD34) and myeloid (CD115 and CD14) differentiation markers in parallel with increased phagocytic capacity, and acquisition of adipogenic potential. Collectively, these results suggest that canine hemangiosarcomas arise from multipotent progenitors that differentiate into distinct subtypes. Improved understanding of the mechanisms that determine the molecular and phenotypic differentiation of tumor cells in vivo could change paradigms regarding the origin and progression of endothelial sarcomas.

Zebrafish as a model for human osteosarcoma

For various reasons involving biological comparativeness, expansive technological possibilities, accelerated experimental speed, and competitive costs, zebrafish has become a comprehensive model for cancer research. Hence, zebrafish embryos and full-grown fish have been instrumental for studies of leukemia, melanoma, pancreatic cancer, bone tumors, and other malignancies. Although because of its similarities to human osteogenesis zebrafish appears to be an appealing model to investigate osteosarcoma, only a few osteosarcoma specific studies have been accomplished yet. Here, we review interesting related and unrelated reports of which the findings might be extrapolated to osteosarcoma. More importantly, rational but yet unexplored applications of zebrafish are debated to expand the window of opportunities for future establishment of osteosarcoma models. Accordingly technological advances of zebrafish based cancer research, such as robotic high-throughput multicolor injection systems and advanced imaging methods are discussed. Furthermore, various use of zebrafish embryos for screening drug regimens by combinations of chemotherapy, novel drug deliverers, and immune system modulators are suggested. Concerning the etiology, the high degree of genetic similarity between zebrafish and human cancers indicates that affected regions are evolutionarily conserved. Therefore, zebrafish as a swift model system that allows for the investigation of multiple candidate gene-defects is presented.

β-Catenin transcriptional activity is minimal in canine osteosarcoma and its targeted inhibition results in minimal changes to cell line behaviour

Canine osteosarcoma (OS) is an aggressive malignancy associated with poor outcomes. Therapeutic improvements are likely to develop from an improved understanding of signalling pathways contributing to OS development and progression. The Wnt signalling pathway is of interest for its role in osteoblast differentiation, its dysregulation in numerous cancer types, and the relative frequency of cytoplasmic accumulation of β-catenin in canine OS. This study aimed to determine the biological impact of inhibiting canonical Wnt signalling in canine OS, by utilizing either β-catenin siRNA or a dominant-negative T-cell factor (TCF) construct. There were no consistent, significant changes in cell line behaviour with either method compared to parental cell lines. Interestingly, β-catenin transcriptional activity was three-fold higher in normal canine primary osteoblasts compared to canine OS cell lines. These results suggest canonical Wnt signalling is minimally active in canine OS and its targeted inhibition is not a relevant therapeutic strategy.