CXCR7 maintains osteosarcoma invasion after CXCR4 suppression in bone marrow microenvironment

BMP2 induces osteogenic differentiation through ACKR3 in mesenchymal stem cells

In recent years, bone loss related diseases have attracted more and more attention, such as osteoporosis and osteonecrosis of the femoral head exhibited symptoms of osteopenia or insufficient bone mass in a certain stage. Mesenchymal stem cells (MSCs), which can be induced to differentiate into osteoblasts under certain conditions can provide a new solution bone disease. Herein, we deciphered the possible mechanism by which BMP2 drives the transduction of MSCs to the osteoblast lineage through ACKR3/p38/MAPK signaling. The levels of ACKR3 in femoral tissues of samples from humans with different ages and sexes were measured firstly and found that ACKR3 protein levels increase with age. In vitro cellular assays showed that ACKR3 inhibits BMP2-induced osteo-differentiation and promotes adipo-differentiation of MSCs, whereas siACKR3 exhibited the opposite effects. In vitro embryo femur culture experiment showed that inhibition of ACKR3 enhanced BMP2-induced trabecular bone formation in C57BL6/J mouse. In terms of molecular mechanisms, we found that p38/MAPK signaling might play the key role. ACKR3 agonist TC14012 suppressed the phosphorylation of p38 and STAT3 in BMP2 induced MSCs differentiation. Our findings suggested that ACKR3 might be a novel therapeutic target for the treatment of bone-associated diseases and bone-tissue engineering.

Modified mesenchymal stem cells in cancer therapy: A smart weapon requiring upgrades for wider clinical applications

Mesenchymal stem stromal cells (MSC) are characterized by the intriguing capacity to home toward cancer cells after systemic administration. Thus, MSC can be harnessed as targeted delivery vehicles of cytotoxic agents against tumors. In cancer patients, MSC based advanced cellular therapies were shown to be safe but their clinical efficacy was limited. Indeed, the amount of systemically infused MSC actually homing to human cancer masses is insufficient to reduce tumor growth. Moreover, induction of an unequivocal anticancer cytotoxic phenotype in expanded MSC is necessary to achieve significant therapeutic efficacy. Ex vivo cell modifications are, thus, required to improve anti-cancer properties of MSC. MSC based cellular therapy products must be handled in compliance with good manufacturing practice (GMP) guidelines. In the present review we include MSC-improving manipulation approaches that, even though actually tested at preclinical level, could be compatible with GMP guidelines. In particular, we describe possible approaches to improve MSC homing on cancer, including genetic engineering, membrane modification and cytokine priming. Similarly, we discuss appropriate modalities aimed at inducing a marked cytotoxic phenotype in expanded MSC by direct chemotherapeutic drug loading or by genetic methods. In conclusion, we suggest that, to configure MSC as a powerful weapon against cancer, combinations of clinical grade compatible modification protocols that are currently selected, should be introduced in the final product. Highly standardized cancer clinical trials are required to test the efficacy of ameliorated MSC based cell therapies.

New perspective into mesenchymal stem cells: Molecular mechanisms regulating osteosarcoma

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The origin of osteosarcoma cells from osteoblasts and mesenchymal stem cells remains controversial.

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Mesenchymal stem cells regulate the development of osteosarcoma by influencing the tumor microenvironment and mediating cell communication.

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Mesenchymal stem cells and exosomes secreted by them can be used as good genes and drug carriers for the treatment of osteosarcoma.

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Mesenchymal stem cells from different tissue sources have different regulatory effects on the development of osteosarcoma.

Mesenchymal stem cells (MSCs) are multipotent stem cells with significant potential for regenerative medicine. The tumorigenesis of osteosarcoma is an intricate system and MSCs act as an indispensable part of this, interacting with the tumor microenvironment (TME) during the process. MSCs link to cells by acting on each component in the TME via autocrine or paracrine extracellular vesicles for cellular communication. Because of their unique characteristics, MSCs can be modified and processed into good biological carriers, loaded with drugs, and transfected with anticancer genes for the targeted treatment of osteosarcoma. Previous high-quality reviews have described the biological characteristics of MSCs; this review will discuss the effects of MSCs on the components of the TME and cellular communication and the prospects for clinical applications of MSCs.

The Role of the CXCL12/CXCR4/CXCR7 Chemokine Axis in Cancer

Chemokines are a family of small, secreted cytokines which regulate a variety of cell functions. The C-X-C motif chemokine ligand 12 (CXCL12) binds to C-X-C chemokine receptor type 4 (CXCR4) and C-X-C chemokine receptor type 7 (CXCR7). The interaction of CXCL12 and its receptors subsequently induces downstream signaling pathways with broad effects on chemotaxis, cell proliferation, migration, and gene expression. Accumulating evidence suggests that the CXCL12/CXCR4/CXCR7 axis plays a pivotal role in tumor development, survival, angiogenesis, metastasis, and tumor microenvironment. In addition, this chemokine axis promotes chemoresistance in cancer therapy via complex crosstalk with other pathways. Multiple small molecules targeting CXCR4/CXCR7 have been developed and used for preclinical and clinical cancer treatment. In this review, we describe the roles of the CXCL12/CXCR4/CXCR7 axis in cancer progression and summarize strategies to develop novel targeted cancer therapies.

Bone Microenvironment and Osteosarcoma Metastasis

The bone microenvironment is an ideal fertile soil for both primary and secondary tumors to seed. The occurrence and development of osteosarcoma, as a primary bone tumor, is closely related to the bone microenvironment. Especially, the metastasis of osteosarcoma is the remaining challenge of therapy and poor prognosis. Increasing evidence focuses on the relationship between the bone microenvironment and osteosarcoma metastasis. Many elements exist in the bone microenvironment, such as acids, hypoxia, and chemokines, which have been verified to affect the progression and malignance of osteosarcoma through various signaling pathways. We thoroughly summarized all these regulators in the bone microenvironment and the transmission cascades, accordingly, attempting to furnish hints for inhibiting osteosarcoma metastasis via the amelioration of the bone microenvironment. In addition, analysis of the cross-talk between the bone microenvironment and osteosarcoma will help us to deeply understand the development of osteosarcoma. The cellular and molecular protagonists presented in the bone microenvironment promoting osteosarcoma metastasis will accelerate the exploration of novel therapeutic strategies towards osteosarcoma.

New Insights about the Wnt/β-Catenin Signaling Pathway in Primary Bone Tumors and Their Microenvironment: A Promising Target to Develop Therapeutic Strategies?

Osteosarcoma and Ewing sarcoma are the most common malignant primary bone tumors mainly occurring in children, adolescents and young adults. Current standard therapy includes multidrug chemotherapy and/or radiation specifically for Ewing sarcoma, associated with tumor resection. However, patient survival has not evolved for the past decade and remains closely related to the response of tumor cells to chemotherapy, reaching around 75% at 5 years for patients with localized forms of osteosarcoma or Ewing sarcoma but less than 30% in metastatic diseases and patients resistant to initial chemotherapy. Despite Ewing sarcoma being characterized by specific EWSR1-ETS gene fusions resulting in oncogenic transcription factors, currently, no targeted therapy could be implemented. It seems even more difficult to develop a targeted therapeutic strategy in osteosarcoma which is characterized by high complexity and heterogeneity in genomic alterations. Nevertheless, the common point between these different bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Therefore, targeting different actors of the bone tumor microenvironment has been hypothesized to develop new therapeutic strategies. In this context, it is well known that the Wnt/β-catenin signaling pathway plays a key role in cancer development, including osteosarcoma and Ewing sarcoma as well as in bone remodeling. Moreover, recent studies highlight the implication of the Wnt/β-catenin pathway in angiogenesis and immuno-surveillance, two key mechanisms involved in metastatic dissemination. This review focuses on the role played by this signaling pathway in the development of primary bone tumors and the modulation of their specific microenvironment.