Cancer cells reprogram to metastatic state through the acquisition of platelet mitochondria.

Metastasis is the major cause of cancer deaths, and cancer cells evolve to adapt to various tumor microenvironments, which hinders the treatment of tumor metastasis. Platelets play critical roles in tumor development, especially during metastasis. Here, we elucidate the role of platelet mitochondria in tumor metastasis. Cancer cells are reprogrammed to a metastatic state through the acquisition of platelet mitochondria via the PINK1/Parkin-Mfn2 pathway. Furthermore, platelet mitochondria regulate the GSH/GSSG ratio and reactive oxygen species (ROS) in cancer cells to promote lung metastasis of osteosarcoma. Impairing platelet mitochondrial function has proven to be an efficient approach to impair metastasis, providing a direction for osteosarcoma therapy. Our findings demonstrate mitochondrial transfer between platelets and cancer cells and suggest a role for platelet mitochondria in tumor metastasis.

ISG15 is a potential therapeutic target for osteosarcoma: a comprehensive analysis based on bioinformatics and in vitro experiments.

BACKGROUND: The expression of aberrant interferon-stimulated gene 15 (ISG15) is connected with various human diseases, including cancer. ISG15 is involved in tumor formation and metastasis. However, its role in osteosarcoma is uncertain. METHODS: ISG15 expression in pan-cancer from RNA Sequencing data were obtained from The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression (GTEx) databases. The relationship between ISG15 expression and prognosis was assessed through TCGA clinical survival data. Immunohistochemistry (IHC) images of ISG15 were retrieved using the Human Protein Atlas to analyze the differences in selected normal and tumor tissues. Gene enrichment analysis and signaling pathway analysis were used to assess the potential role of ISG15 in sarcoma, and the correlation between ISG15 expressions and immune cell infiltration levels was estimated by immune infiltration analysis. The expression levels of ISG15 were assessed by qRT-PCR and IHC. Colony formation, wound healing assay and transwell assay were used to detect the effects of ISG15 on the biological behaviors of osteosarcoma cells. The correlation between ISG15 levels and CD8+/CD68+ cells was further examined by double-labeled immunofluorescence. The chemotactic effect of ISG15 on CD8+/CD68+ cells was demonstrated by chemotactic experiments and flow cytometry. RESULTS: ISG15 was highly expressed in most cancers, while high ISG15 expression was significantly correlated with poor overall survival. Gene enrichment analysis in sarcoma suggested that antigen processing and presentation might be involved in the oncogenic mechanism of ISG15. Further immune infiltration analysis showed that high ISG15 expression might reflect the infiltration level of certain immune cells. Additionally, our verification showed that ISG15 was significantly related to the occurrence and metastasis of osteosarcoma, and knockdown of ISG15 significantly altered cell biological behavior, resulting in decreased proliferation, migration and invasion capabilities of osteosarcoma cells. The high expression of ISG15 in osteosarcoma tissue was associated with a high level of CD68+ immune cell infiltration while a low level of CD8+ T cell infiltration. CD68+ immune cells were recruited in vitro by overexpression of ISG15, which on the contrary could weaken the chemotaxis of CD8+ T cells. CONCLUSION: High ISG15 expression is an inherent feature of osteosarcoma and triggers tumorigenesis and metastasis by regulating tumor immunogenicity. ISG15 is expected to be the target of osteosarcoma treatment.

Circular RNA expression profile identifies circMGEA5 as a novel metastasis-promoting factor and potential biomarker in osteosarcoma.

Osteosarcoma (OS) is associated with a high incidence of lung metastasis, which leads to a high risk of cancer death. Circular RNA (circRNA), a novel class of noncoding RNA, is emerging as a key player in human cancer. Herein, we explored the role of circMGEA5 in OS metastasis by conducting circRNA expression microarray. CircMGEA5 was significantly upregulated in metastatic OS tissues compared to primary tissues. High circMGEA5 was positively related with shorter overall and disease-free survival time. Knockdown of circMGEA5 suppressed OS cell migration, invasion, and epithelial-mesenchymal transition (EMT). Mechanistically, circMGEA5 acted as a competing endogenous RNA (ceRNA) to directly sponge miR-153-3p and miR-8084, resulting in increasing ZEB1 and Snail expression, respectively, thereby inducing EMT and metastasis. In turn, ZEB1 and Snail were capable to bind to circMGEA5 promoter, activating circMGEA5 transcription, thus forming a positive feedback loop. Furthermore, we established the tail vein injection model and found that circMGEA5 depletion remarkably reduced lung metastasis nodules generated by OS cells. In sum, our findings, for the first time, reveal the metastasis-promoting role of circMGEA5 in OS. Targeting of this newly identified ceRNA axis may be crucial in the development of novel therapies for metastatic OS patients.

Metastasis of Osteosarcoma to the Abdomen: A Report of Two Cases and a Review of the Literature.

Two cases of primary distal femur osteosarcoma with subsequent metastasis to the abdomen are presented. In both cases, the development of abdominal metastasis was quickly followed by patient decline and death. A review of the literature was performed, assessing the presentation and survival of patients with osteosarcoma metastasized to the abdomen. As illustrated by the current cases and the literature review, abdominal metastasis in osteosarcoma is often a late manifestation and terminal prognostic indicator. Nonetheless, early detection and prompt intervention of this less common site of disease metastasis may improve patient care and palliative therapy.

Sea cucumber Cucumaria frondosa fucoidan inhibits osteosarcoma adhesion and migration by regulating cytoskeleton remodeling.

Osteosarcoma (OS) has been demonstrated to be difficult to cure due to its potently malignant metastasis. Therefore, new therapeutic approaches blocking the metastatic potential of OS are urgently required to improve the outcomes for OS patients. In the present study, the anti­metastatic capacity of sea cucumber (Cucumaria frondosa) fucoidan (Cf­Fuc) was evaluated on osteosarcoma cells by cell adhesion assay, Transwell assay and U2OS cell migration assay. The underlying mechanism on the dynamic remodeling of the cytoskeleton was also explored. The present data indicated that Cf­Fuc could block the U2OS osteosarcoma cell adhesion to fibronectin and significantly inhibit U2OS cell migration. Cf­Fuc greatly impaired the migration capacity of U2OS cells, and the migrated distance and velocity of Cf­Fuc­treated cells were markedly reduced. Also, Cf­Fuc could impair the dynamic remodeling of the cytoskeleton possibly by suppressing the phosphorylation of focal adhesion kinase and paxillin, as well as the activation of the Rac1/PAK1/LIMK1/cofilin signaling axis. Collectively, the present findings provide a novel therapeutic potential of C. frondosa fucoidan for osteosarcoma metastasis.

Novel oncogene COPS3 interacts with Beclin1 and Raf-1 to regulate metastasis of osteosarcoma through autophagy.

BACKGROUND: Expression of COP9 signalosome subunit 3 (COPS3), an oncogene overexpressed in osteosarcoma, has been demonstrated to be significantly correlated with tumor metastasis. However, the underlying mechanism by which COPS3 promotes metastasis of osteosarcoma and its role in autophagy remain unknown. METHODS: The expression of COPS3 was detected in primary osteosarcoma tissues and matching lung metastasis tissues by immunohistochemistry (IHC). The effect of COPS3 on the metastasis of osteosarcoma cells was investigated by transwell, wound healing assays and animal studies. Indicated proteins was analyzed by western blotting when COPS3 was knockdown or overexpressed. The COPS3 Interacting protein was determined by immunoprecipitation assay. The relationship between COPS3 and autophagy was detected by western blotting and immunofluorescence. RESULTS: We found that knockdown of COPS3 significantly reduced the lung metastasis of osteosarcoma cells in a mouse model, coinciding with downregulation of mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinase (ERK) signaling. The silencing of COPS3 also inhibited the epithelial-mesenchymal transition (EMT) through the 90 kDa ribosomal S6 kinases (RSK), a family of signal transduction proteins downstream of MEK/ERK. Reciprocal immunoprecipitation assays revealed that COPS3 directly interacts with Raf-1, an upstream regulator of MEK/ERK. Surprisingly, Beclin1, an important autophagic protein, appeared in the COPS3-immunoprecipitates, along with the autophagic markers LC3-I and LC3-II. Loss of COPS3 completely inhibited H2O2-induced autophagic flux and reduced Beclin1 expression. Additionally, autophagy inhibitor or silencing of Beclin1 both decreased cell metastasis. CONCLUSIONS: Taken together, these data reveal a novel function of COPS3 in the regulation of autophagy and highlight the relationship between autophagy and metastasis in osteosarcoma cells.

Connective tissue growth factor stimulates osteosarcoma cell migration and induces osteosarcoma metastasis by upregulating VCAM-1 expression.

Osteosarcoma is the most common bone malignancy that occurs in the young population. After osteosarcoma cells metastasize to the lung, prognosis is very poor owing to difficulties in early diagnosis and effective treatment. Recently, connective tissue growth factor (CTGF) was reported to be a critical contributor to osteosarcoma metastasis. However, the detailed mechanism associated with CTGF-directed migration in bone neoplasms is still mostly unknown. Through the in vivo and in vitro examination of osteosarcoma cells, this study suggests that VCAM-1 up-regulation and increased osteosarcoma cell migration are involved in this process. Antagonizing αvß3 integrin inhibited cell migration. Moreover, FAK, PI3K, Akt and NF-κB activation were also shown to be involved in CTGF-mediated osteosarcoma metastasis. Taken together, CTGF promotes VCAM-1 production and further induces osteosarcoma metastasis via the αvß3 integrin/FAK/PI3K/Akt/NF-κB signaling pathway, which could represent a promising clinical target to improve patient outcome.

miR-19a-mediated downregulation of RhoB inhibits the dephosphorylation of AKT1 and induces osteosarcoma cell metastasis.

Osteosarcoma is a primary malignancy that develops in bone, along with serious recurrence and metastasis. As an isoform of Rho family GTPases, RhoB could suppress cell proliferation, invasion, and anti-angiogenesis. But it is not clear how RhoB involves in tumor metastasis. Here we found that expression of RhoB was decreased in osteosarcoma primary samples and cell lines. Ectopic expression of RhoB restrains the migration of osteosarcoma cells in vitro and in vivo, and induces osteosarcoma cell apopotsis. Further study showed that overexpression of RhoB could increase the proportion of B55 in PP2A complex and enhance the dephosphorylation of AKT1 by interacting with B55. Moreover, we demonstrated that miR-19a, which exhibits abnormal expression in highly metastatic osteosarcoma cell lines, could inhibit the expression of RhoB and promote the lung metastasis of osteosarcoma cells in vivo. Our results indicate that miR-19a-mediated RhoB is a critical regulator for the dephosphorylation of AKT1 in osteosarcoma cells. It may have a possible strategy on suppressing osteosarcoma metastasis by miR-19a inhibitory oligonucleotides. The miR-19a/RhoB/AKT1 network may help us to better understand the mechanism of osteosarcoma metastasis.

Decrease in stathmin expression by arsenic trioxide inhibits the proliferation and invasion of osteosarcoma cells via the MAPK signal pathway.

Osteosarcoma (OS) is the most common type of malignant bone tumor in children and adolescents. In total, 40-50% of patients with OS experience metastasis, and thus have a poor prognosis. Our previous study demonstrated that arsenic trioxide (As2O3) combined with doxorubicin [also known as Adriamycin (ADM)] significantly inhibited OS cell proliferation by downregulating stathmin expression. The present study investigated the effect and mechanism of stathmin expression on OS cell invasion. It was identified that the expression of stathmin was increased in human ADM-resistant OS MG63 (MG63/dox) cells compared with the level in the normal osteoblast hFoB1.19cell line using western blot analysis. Lentiviral-mediated small hairpin RNA (shRNA) was constructed to silence stathmin expression of MG63/dox cells. In transwell assay, stathmin-knockdown significantly suppressed migration and invasion in MG63/dox cells. As2O3 combined with ADM inhibited the migration and invasion of MG63/dox cells, and was associated with the downregulation of phosphorylated-mitogen-activated protein kinase (MAPK) 1 and ß-catenin, and upregulation of phosphorylated-MAPK8 and E-cadherin. In addition, stathmin-knockdown significantly suppressed tumor growth and increased E-cadherin expression in a xenograft nude mouse model. Taken together, these data suggested that As2O3 combined with ADM inhibited stathmin-mediated invasion via the MAPK pathway. Elucidation of the mechanism for stathmin downregulation by As2O3 may provide novel insights into the mechanism of OS metastasis.

miR-491 Inhibits Osteosarcoma Lung Metastasis and Chemoresistance by Targeting αB-crystallin.

Dysregulated microRNAs (miRNAs) play an important role in osteosarcoma (OS) progression. In the present study, we investigate the clinical significance of serum miR-491 level and the potential role of miR-491 in OS lung metastasis and chemoresistance. Clinical data show that the level of miR-491 was decreased in serum from OS patients compared with healthy control subjects, and that a decreased serum miR-491 level is correlated with increased metastasis, poor chemoresponse, and lower survival rate in OS patients. In vitro and in vivo experiments show that overexpression of miR-491 suppresses OS cell lung metastasis, whereas it enhances cisplatin (CDDP)-induced tumor growth inhibition and apoptosis. In contrast, inhibition of miR-491 stimulates OS cell lung metastasis and suppresses CDDP-induced tumor growth inhibition and apoptosis. Furthermore, we demonstrate that miR-491 exerts its role by directly targeting αB-crystallin (CRYAB) in OS. Our findings suggest that serum level of miR-491 has potential as a biomarker for predicting OS progression and prognosis of OS patients. Additionally, restoration of miR-491 may be a novel strategy for inhibiting OS lung metastasis and overcoming OS cell resistance to chemotherapy.

Identification and functional study of osteosarcoma metastasis marker genes.

To date, osteosarcoma metastasis genes, which are key for accurate initial diagnosis of the disease, have not been well identified. In the present study, osteosarcoma samples with and without metastasis were collected from 31 patients. Specific complementary DNA subtraction techniques were used to identify the osteosarcoma metastasis transcripts, which are responsible for the metastasis of osteosarcoma. The specific differentially expressed transcripts were identified by Basic Local Alignment Search Tool analysis and the results were validated by immunoblotting. Specifically, ezrin and ß4 integrin were employed as markers to detect osteosarcoma metastasis in the initial stages. The results of the present study indicated that the two transcripts, ezrin and ß4 integrin, were highly expressed in patients with osteosarcoma metastasis, and concluded that these were osteosarcoma metastasis genes. These results indicate that ß4 integrin and/or ezrin may be used as a novel marker for the detection of osteosarcoma metastasis in the initial stages.

Amphiregulin enhances intercellular adhesion molecule-1 expression and promotes tumor metastasis in human osteosarcoma.

Osteosarcoma is a common, high malignant, and metastatic bone cancer. Amphiregulin (AREG) has been associated with cancer cellular activities. However, the effect of AREG on metastasis activity in human osteosarcoma cells has yet to be determined. We determined that AREG increases the expression of intercellular adhesion molecule-1 (ICAM-1) through PI3K/Akt signaling pathway via its interaction with the epidermal growth factor receptor, thus resulting in the enhanced cell migration of osteosarcoma. Furthermore, AREG stimulation increased the association of NF-κB to ICAM-1 promoter which then up-regulated ICAM-1 expression. Finally, we observed that shRNA silencing of AREG decreased osteosarcoma metastasis in vivo. Our findings revealed a relationship between osteosarcoma metastatic potential and AREG expression and the modulating effect of AREG on ICAM-1 expression.