Extracellular Vesicles in Tumors: A Potential Mediator of Bone Metastasis

Exosomal lncRNA HOTAIR promotes osteoclast differentiation by targeting TGF-β/PTHrP/RANKL pathway

Bone tissue is a common metastatic site of lung cancer, and bone metastasis is characterized by abnormal differentiation and malfunction of osteoclast, and the roles of exosomes derived from lung cancer have attracted much attention. In our study, we found that the level of HOTAIR expression in A549 and H1299 exosomes was higher than those of normal lung fibrocytes. Overexpression of HOTAIR in A549 and H1299 exosomes promoted osteoclast differentiation. Furthermore, A549-Exos and H1299-Exos targeted bone tissues, and bone formation was significantly inhibited in vivo. Mechanistically, exosomal lncRNA HOTAIR promoted bone resorption by targeting TGF-β/PTHrP/RANKL pathway.

The impacts of exosomes on bone metastatic progression and their potential clinical utility

Bone is one of the most common sites of cancer metastasis. Once cancer metastasizes to the bone, the mortality rate of cancer patients dramatically increases. Although the exact mechanisms for this observation remain elusive, recent studies have revealed that the complex crosstalk between bone marrow microenvironment and bone metastatic cancer cells is responsible for the induction of treatment resistance. Consequently, bone metastasis is currently considered incurable. Bone metastasis not only impairs the patients' survival, but also negatively affects their quality of life by causing painful complications. It has recently been implicated the regulatory role of exosomes in cancer development and/or progression as a delivery biomaterial between cancer cells and tumor microenvironment. However, little is known as to how exosomes contribute to the progression of bone metastasis by impaction on the crosstalk between bone metastatic cancer cells and bone marrow microenvironment. Here, we highlighted the emerging roles of cancer-derived exosomes in (i) the process of dissemination and bone colonization of bone metastatic cancer cells, (ii) the enhancement of crosstalk between bone marrow microenvironment and bone metastatic cancer cells, (iii) the development of its resultant painful complications, and (iv) the clinical applications of exosomes in the bone metastatic setting.

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Cancer-derived exosomes facilitate cancer dissemination and colonization to bone.

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Cancer-derived exosomes are crucial for controlling bone metastatic phenotype.

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Cancer-derived exosomes prime bone marrow microenvironment for further metastasis.

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Cancer-derived exosomes are involved in development of cancer-induced bone pain.

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Exosomes can be used as therapies and/or diagnostic tools for bone metastasis.

miR-92a-3p encapsulated in bone metastatic mammary tumor cell-derived extracellular vesicles modulates mature osteoclast longevity

Aberrant osteoclast formation and activation are the hallmarks of osteolytic metastasis. Extracellular vesicles (EVs), released from bone metastatic tumor cells, play a pivotal role in the progression of osteolytic lesions. However, the mechanisms through which tumor cell-derived EVs regulate osteoclast differentiation and function have not been fully elucidated. In this study, we found that 4T1 bone metastatic mouse mammary tumor cell-derived EVs (4T1-EVs) are taken up by mouse bone marrow macrophages to facilitate osteoclastogenesis. Furthermore, treatment of mature osteoclasts with 4T1-EVs promoted bone resorption, which was accompanied by enhanced survival of mature osteoclasts through the negative regulation of caspase-3. By comparing the miRNA content in 4T1-EVs with that in 67NR nonmetastatic mouse mammary tumor cell-derived EVs (67NR-EVs), miR-92a-3p was identified as one of the most enriched miRNAs in 4T1-EVs, and its transfer into mature osteoclasts significantly reduced apoptosis. Bioinformatic and Western blot analyses revealed that miR-92a-3p directly targeted phosphatase and tensin homolog (PTEN) in mature osteoclasts, resulting in increased levels of phospho-Akt. Our findings provide novel insights into the EV-mediated regulation of osteoclast survival through the transfer of miR-92a-3p, which enhances mature osteoclast survival via the Akt survival signaling pathway, thus promoting bone resorption.

Effectiveness and Safety of the Traditional Chinese Medicine Treatment (HuoxueHuayu Therapy) for Malignant Tumors: A Systematic Review and Meta-Analysis

Background. A malignant tumor is one of the refractory diseases that threaten human life and health. HuoxueHuayu therapy (one of the Traditional Chinese Medicine therapies to promote blood circulation and remove blood stasis) is widely used as an antitumor supplementary method. However, its efficacy and safety are still controversial. Therefore, the objective of this study was to provide evidence-based evidence for HuoxueHuayu therapy in the treatment of malignant tumors and confirm its safety and effectiveness. Methods. A systematic search in 8 electronic databases targeted randomized clinical studies evaluating HuoxueHuayu therapy for response evaluation, tumor progression rate, quality of life (QoL), peripheral hemogram, performance status, immunologic function, tumor marker, and blood coagulation function in cancer patients, published from the establishment of the database to December 31, 2020. Risk ratio (RR) was used for counting data, mean difference (MD) or standardized mean difference (SMD) was used for measurement data, and 95% confidence interval (CI) was used as efficacy analysis statistics. Results. Our search identified 69 studies, evaluating 4402 patients in total. Randomized controlled trials (RCTs) evaluated gastric (n = 14), lung (n = 18), pancreatic (n = 2), colorectal (n = 10), liver (n = 14), breast (n = 2), ovarian (n = 2), gallbladder (n = 1), esophagus (n = 1), and combined (n = 14) cancers and hematological malignancies (n = 2). The duration of HuoxueHuayu therapy ranged from 3 to 48 weeks. Methodological bias was low in 64 studies and high in 5 studies. HuoxueHuayu therapy was associated with significant improvement in response evaluation (Response Evaluation Criteria in Solid Tumor (RECIST): RR: 1.44, 95% CI: 1.27 to 1.63, I2 = 0%, n = 33 studies; World Health Organization Criteria in Solid Tumors (WHOCIST): RR: 1.40, 95% CI: 1.23 to 1.59, I2 = 0%, n = 26 studies), recurrence rate (RR: 0.85, 95% CI: 0.72 to 0.99, I2 = 0%, n = 2 studies), quality of life, performance status (MD: 5.60, 95% CI: 5.04 to 6.15, $p<0.001$ ), immunologic function (CD3: SMD: 1.23, 95% CI: 0.79 to 1.66, $p<0.001$ ; CD4: SMD: 1.25, 95% CI: 0.77 to 1.74, $p<0.001$ ; CD4/CD8: SMD: 1.05, 95% CI: 0.69 to 1.42, $p<0.001$ ; natural killer cell (NK): SMD: 0.74, 95% CI: 0.32 to 1.15, $p<0.001$ ), tumor marker, and blood coagulation function (D-dimer (D-D); fibrinogen (FIB)). In addition, HuoxueHuayu therapy could reduce toxicity caused by chemotherapy and radiotherapy without risks of liver and kidney injury or bleeding, although the effect on tumor metastasis was uncertain. Conclusions. The present update of our systematic review and meta-analyses provided essential evidence for the beneficial effect of HuoxueHuayu therapy to show promise in cancer treatment, improving quality of life, addressing cancer-related symptoms, and reducing toxicity in a secure way.

The basic characteristics of extracellular vesicles and their potential application in bone sarcomas

Bone sarcomas are rare cancers accompanied by metastatic disease, mainly including osteosarcoma, Ewing sarcoma and chondrosarcoma. Extracellular vesicles (EVs) are membrane vesicles released by cells in the extracellular matrix, which carry important signal molecules, can stably and widely present in various body fluids, such as plasma, saliva and scalp fluid, spinal cord, breast milk, and urine liquid. EVs can transport almost all types of biologically active molecules (DNA, mRNA, microRNA (miRNA), proteins, metabolites, and even pharmacological compounds). In this review, we summarized the basic biological characteristics of EVs and focused on their application in bone sarcomas. EVs can be use as biomarker vehicles for diagnosis and prognosis in bone sarcomas. The role of EVs in bone sarcoma has been analyzed point-by-point. In the microenvironment of bone sarcoma, bone sarcoma cells, mesenchymal stem cells, immune cells, fibroblasts, osteoclasts, osteoblasts, and endothelial cells coexist and interact with each other. EVs play an important role in the communication between cells. Based on multiple functions in bone sarcoma, this review provides new ideas for the discovery of new therapeutic targets and new diagnostic analysis.