Role of Activator Protein-1 Complex on the Phenotype of Human Osteosarcomas Generated from Mesenchymal Stem Cells

Signal Pathways and microRNAs in Osteosarcoma Growth and the Dual Role of Mesenchymal Stem Cells in Oncogenesis

The major challenges in Osteosarcoma (OS) therapy are its heterogeneity and drug resistance. The development of new therapeutic approaches to overcome the major growth mechanisms of OS is urgently needed. The search for specific molecular targets and promising innovative approaches in OS therapy, including drug delivery methods, is an urgent problem. Modern regenerative medicine focuses on harnessing the potential of mesenchymal stem cells (MSCs) because they have low immunogenicity. MSCs are important cells that have received considerable attention in cancer research. Currently, new cell-based methods for using MSCs in medicine are being actively investigated and tested, especially as carriers for chemotherapeutics, nanoparticles, and photosensitizers. However, despite the inexhaustible regenerative potential and known anticancer properties of MSCs, they may trigger the development and progression of bone tumors. A better understanding of the complex cellular and molecular mechanisms of OS pathogenesis is essential to identify novel molecular effectors involved in oncogenesis. The current review focuses on signaling pathways and miRNAs involved in the development of OS and describes the role of MSCs in oncogenesis and their potential for antitumor cell-based therapy.

TA-MSCs, TA-MSCs-EVs, MIF: their crosstalk in immunosuppressive tumor microenvironment

As an important component of the immunosuppressive tumor microenvironment (TME), it has been established that mesenchymal stem cells (MSCs) promote the progression of tumor cells. MSCs can directly promote the proliferation, migration, and invasion of tumor cells via cytokines and chemokines, as well as promote tumor progression by regulating the functions of anti-tumor immune and immunosuppressive cells. MSCs-derived extracellular vesicles (MSCs-EVs) contain part of the plasma membrane and signaling factors from MSCs; therefore, they display similar effects on tumors in the immunosuppressive TME. The tumor-promoting role of macrophage migration inhibitory factor (MIF) in the immunosuppressive TME has also been revealed. Interestingly, MIF exerts similar effects to those of MSCs in the immunosuppressive TME. In this review, we summarized the main effects and related mechanisms of tumor-associated MSCs (TA-MSCs), TA-MSCs-EVs, and MIF on tumors, and described their relationships. On this basis, we hypothesized that TA-MSCs-EVs, the MIF axis, and TA-MSCs form a positive feedback loop with tumor cells, influencing the occurrence and development of tumors. The functions of these three factors in the TME may undergo dynamic changes with tumor growth and continuously affect tumor development. This provides a new idea for the targeted treatment of tumors with EVs carrying MIF inhibitors.

Addressing Doxorubicin Resistance in Bone Sarcomas Using Novel Drug-Resistant Models

Bone sarcomas have not shown a significant improvement in survival for decades, due, in part, to the development of resistance to current systemic treatments, such as doxorubicin. To better understand those mechanisms mediating drug-resistance we generated three osteosarcoma and one chondrosarcoma cell lines with a stable doxorubicin-resistant phenotype, both in vitro and in vivo. These resistant strains include a pioneer model generated from a patient-derived chondrosarcoma line. The resistant phenotype was characterized by a weaker induction of apoptosis and DNA damage after doxorubicin treatment and a lower migratory capability. In addition, all resistant lines expressed higher levels of ABC pumps; meanwhile, no clear trends were found in the expression of anti-apoptotic and stem cell-related factors. Remarkably, upon the induction of resistance, the proliferation potential was reduced in osteosarcoma lines but enhanced in the chondrosarcoma model. The exposure of resistant lines to other anti-tumor drugs revealed an increased response to cisplatin and/or methotrexate in some models. Finally, the ability to retain the resistant phenotype in vivo was confirmed in an osteosarcoma model. Altogether, this work evidenced the co-existence of common and case-dependent phenotypic traits and mechanisms associated with the development of resistance to doxorubicin in bone sarcomas.

Proof of concept for the use of trained sniffer dogs to detect osteosarcoma

Sarcomas are mesenchymal cancers which often show an aggressive behavior and patient survival largely depends on an early detection. In last years, much attention has been given to the fact that cancer patients release specific odorous volatile organic compounds (VOCs) that can be efficiently detected by properly trained sniffer dogs. Here, we have evaluated for the first time the ability of sniffer dogs (n = 2) to detect osteosarcoma cell cultures and patient samples. One of the two dogs was successfully trained to discriminate osteosarcoma patient-derived primary cells from mesenchymal stem/stromal cells (MSCs) obtained from healthy individuals. After the training phase, the dog was able to detect osteosarcoma specific odor cues in a different panel of 6 osteosarcoma cell lines with sensitivity and specificity rates between 95 and 100%. Moreover, the same VOCs were also detected by the sniffer dog in saliva samples from osteosarcoma patients (n = 2) and discriminated from samples from healthy individuals with a similar efficacy. Altogether, these results indicate that there are common odor profiles shared by cultures of osteosarcoma cells and body fluid samples from patients and provide a first proof of concept about the potential of canine odor detection as a non-invasive screening method to detect osteosarcomas.

Cell Differentiation Trajectory-Associated Molecular Classification of Osteosarcoma

This study aims to investigate the differentiation trajectory of osteosarcoma cells and to construct molecular subtypes with their respective characteristics and generate a multi-gene signature for predicting prognosis. Integrated single-cell RNA-sequencing (scRNA-seq) data, bulk RNA-seq data and microarray data from osteosarcoma samples were used for analysis. Via scRNA-seq data, time-related as well as differentiation-related genes were recognized as osteosarcoma tumor stem cell-related genes (OSCGs). In Gene Expression Omnibus (GEO) cohort, osteosarcoma patients were classified into two subtypes based on prognostic OSCGs and it was found that molecular typing successfully predicted overall survival, tumor microenvironment and immune infiltration status. Further, available drugs for influencing osteosarcoma via prognostic OSCGs were revealed. A 3-OSCG-based prognostic risk score signature was generated and by combining other clinic-pathological independent prognostic factor, stage at diagnosis, a nomogram was established to predict individual survival probability. In external independent TARGET cohort, the molecular types, the 3-gene signature as well as nomogram were validated. In conclusion, osteosarcoma cell differentiation occupies a crucial position in many facets, such as tumor prognosis and microenvironment, suggesting promising therapeutic targets for this disease.

Generation of Mesenchymal Cell Lines Derived from Aged Donors

Background: Mesenchymal stromal cells (MSCs) have the capacity for self-renewal and multi-differentiation, and for this reason they are considered a potential cellular source in regenerative medicine of cartilage and bone. However, research on this field is impaired by the predisposition of primary MSCs to senescence during culture expansion. Therefore, the aim of this study was to generate and characterize immortalized MSC (iMSC) lines from aged donors. Methods: Primary MSCs were immortalized by transduction of simian virus 40 large T antigen (SV40LT) and human telomerase reverse transcriptase (hTERT). Proliferation, senescence, phenotype and multi-differentiation potential of the resulting iMSC lines were analyzed. Results: MSCs proliferate faster than primary MSCs, overcome senescence and are phenotypically similar to primary MSCs. Nevertheless, their multi-differentiation potential is unbalanced towards the osteogenic lineage. There are no clear differences between osteoarthritis (OA) and non-OA iMSCs in terms of proliferation, senescence, phenotype or differentiation potential. Conclusions: Primary MSCs obtained from elderly patients can be immortalized by transduction of SV40LT and hTERT. The high osteogenic potential of iMSCs converts them into an excellent cellular source to take part in in vitro models to study bone tissue engineering.

Molecular mechanisms underpinning sarcomas and implications for current and future therapy

Sarcomas are complex mesenchymal neoplasms with a poor prognosis. Their clinical management is highly challenging due to their heterogeneity and insensitivity to current treatments. Although there have been advances in understanding specific genomic alterations and genetic mutations driving sarcomagenesis, the underlying molecular mechanisms, which are likely to be unique for each sarcoma subtype, are not fully understood. This is in part due to a lack of consensus on the cells of origin, but there is now mounting evidence that they originate from mesenchymal stromal/stem cells (MSCs). To identify novel treatment strategies for sarcomas, research in recent years has adopted a mechanism-based search for molecular markers for targeted therapy which has included recapitulating sarcomagenesis using in vitro and in vivo MSC models. This review provides a comprehensive up to date overview of the molecular mechanisms that underpin sarcomagenesis, the contribution of MSCs to modelling sarcomagenesis in vivo, as well as novel topics such as the role of epithelial-to-mesenchymal-transition (EMT)/mesenchymal-to-epithelial-transition (MET) plasticity, exosomes, and microRNAs in sarcomagenesis. It also reviews current therapeutic options including ongoing pre-clinical and clinical studies for targeted sarcoma therapy and discusses new therapeutic avenues such as targeting recently identified molecular pathways and key transcription factors.

Single-cell transcriptome profiling reveals molecular heterogeneity in human umbilical cord tissue and culture-expanded mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem/stromal cells (UMSCs) demonstrate great therapeutic potential in regenerative medicine. The use of UMSCs for clinical applications requires high quantity and good quality of cells usually by in vitro expansion. However, the heterogeneity and the characteristics of cultured UMSCs and the cognate human umbilical cord tissue at single-cell resolution remain poorly defined. In this study, we created a single-cell transcriptome profile of human umbilical cord tissue and the cognate culture-expanded UMSCs. Based on the inferred characteristics of cell clusters and trajectory analysis, we identified three subgroups in culture-expanded UMSCs and putative novel transcription factors (TFs) in regulating UMSC state transition. Further, putative ligand-receptor interaction analysis demonstrated that cellular interactions most frequently occurred in epithelial-like cells with other cell groups in umbilical cord tissue. Moreover, we dissected the transcriptomic differences of in vitro and in vivo subgroups and inferred the telomere-related molecules and pathways that might be activated in UMSCs for cell expansion in vitro. Our study provides a comprehensive and integrative study of the transcriptomics of human umbilical cord tissue and their cognate-cultured counterparts, which paves the way for a deeper understanding of cellular heterogeneity and offers fundamental biological insight of UMSCs-based cell therapy.

Evidence for AJUBA-catenin-CDH4-linked differentiation resistance of mesenchymal stem cells implies tumorigenesis and progression of head and neck squamous cell carcinoma: a single-cell transcriptome approach

An increasing number of reports indicate that mesenchymal stem cells (MSCs) play an essential role in promoting tumorigenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the molecular mechanisms underlying this process remain unclear. Using the MSC model system, this study analyzes the molecular pathway by which differentiation resistant MSCs promote HNSCC. MSCs were cultured in osteogenic differentiation media and harvested on days 12 and 19. Cells were stained for cell differentiation analysis using Alizarin Red. The osteogenesis-resistant MSCs (OR-MSCs) and MSC-differentiation-derived osteoblasts (D-OSTBs) were identified and subjected to the single-cell transcriptome analysis. Gene-specific analyses of these two sub-populations were performed for the patterns of differential expression. A total of 1 780 differentially expressed genes were determined to distinguish OR-MSCs significantly from D-OSTB. Notably, AJUBA, β-catenin, and CDH4 expression levels were upregulated considerably within the OR-MSCs compared to D-OSTBs. To confirm their clinical relevance, a survey of a clinical cohort revealed a high correlation among the expression levels of AJUBA, β-catenin and CDH4. The results shed new light that OR-MSCs participate in the development of HNSCC via a pathway mediated by AJUBA, β-catenin, CDH4, and CTNNB1, thereby implying that MSC-based therapy is a promising therapeutic approach in the management of HNSCC.

The microRNA‑708‑5p/ZEB1/EMT axis mediates the metastatic potential of osteosarcoma

MicroRNA‑708‑5p (miR‑708‑5p) and epithelial‑​to‑mesenchymal transition (EMT) have been widely identified to contribute to the pathogenesis and progression of multiple cancers. However, the connection between miR‑708‑5p and EMT has not been sufficiently clarified. Therefore, our research aimed to investigate the impact of miR‑708‑5p on EMT and the metastasis of osteosarcoma (OS). We first analyzed the differentially expressed microRNAs (DEmiRNAs) from the GSE70367 dataset. We found that the expression of miR‑708‑5p was lower in OS cells. Overexpression of miR‑708‑5p was able to impair the migration and invasion of OS cells. Moreover, miR‑708‑5p inhibited EMT of OS cells MG63 and SaOS‑2, wherein E‑cadherin was increased, and N‑cadherin, vimentin, and Snail were decreased. Semaphorin 4C (SEMA4C), mitogen‑activated protein kinase kinase kinase 3 (MAP3K3), and zinc finger E‑box‑binding homeobox 1 (ZEB1) were predicted as target genes of miR‑708‑5p by bioinformatics method. Only ZEB1, one of the EMT‑inducing transcription factors, was validated as the direct target gene of miR‑708‑5p in OS cells through dual‑luciferase reporter assay and Western blot analysis. Knockdown of ZEB1 was found to inhibit the metastasis of MG63 and SaOS‑2 cells, whereas ZEB1 over-expression promoted their metastasis. In summary, miR‑708‑5p impaired the metastasis and EMT of OS, which was found to be mediated by inhibition of ZEB1.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.