The roles of metastasis-related proteins in the development of giant cell tumor of bone, osteosarcoma and Ewing's sarcoma

N6-(2-hydroxyethyl)-adenosine (HEA) exhibits antitumor activity for osteosarcoma progression by regulating IGF1 signaling

BACKGROUND

Osteosarcoma is a highly malignant bone tumor with poor prognosis and limited treatment options due to resistance and side effects.

OBJECTIVES

This study investigates the effects of N6-(2-hydroxyethyl)-adenosine (HEA) on osteosarcoma cells and its impact on the IGF1 signaling pathway.

METHODS

Saos2 and MG63 cell lines were treated with HEA. Cell viability, apoptosis, migration, invasion, and EMT markers were assessed. IGF1 expression was analyzed using Western blot, qPCR, and ELISA. IGF1 silencing and recombinant IGF1 treatments were used to explore HEA's mechanisms.

RESULTS

HEA significantly decreased osteosarcoma cell viability and induced apoptosis in a dose- and time-dependent manner. It also inhibited cell migration and invasion, and modulated EMT markers by upregulating E-cadherin and downregulating N-cadherin and vimentin. HEA downregulated IGF1 at both the mRNA and protein levels, and reduced IGF1 secretion. Furthermore, HEA inhibited the PI3K-AKT signaling pathway, which is activated by IGF1. IGF1 silencing mimicked HEA's effects, whereas recombinant IGF1 pre-treatment partially reversed HEA's effects on cell viability, apoptosis, and EMT markers.

CONCLUSIONS

HEA exerts potent anti-cancer effects on osteosarcoma cells both in vitro and in vivo by targeting the IGF1 pathway and inhibiting downstream PI3K-AKT signaling. These results suggest that HEA holds promise as a novel therapeutic agent for osteosarcoma.

CCL2-CCR2 Axis Inhibition in Osteosarcoma Cell Model: The Impact of Oxygen Level on Cell Phenotype

Treatment of osteosarcoma is hampered by tumor hypoxia and requires alternative approaches. Although the CCL2-CCR2 axis is indispensable in tumor-induced inflammation and angiogenesis, its blockade has not been effective to date. This study aimed to characterize how CCR2 inhibition affects the crosstalk of osteosarcoma cells with immune cells to better delineate tumor resistance mechanisms that help withstand such treatment. In this study, 143B cells were exposed to healthy donor PBMC supernatants in a transwell assay lacking direct cell-to-cell contact and subjected to different oxygen concentrations. In addition, mice bearing orthotopic 143B tumors were subjected to CCR2 antagonist treatment. Our findings show that hypoxic conditions alter cytokine and cancer- related protein expression on cells and impair CCR2 antagonist effects in the experimental osteosarcoma model. CCL2-CCR2 axis blockade in the 143B xenografts, which are positive for hypoxia marker CAIX, did not slow 143B tumor growth or metastasis but altered tumor microenvironment by VEGFR downregulation and shift in the CD44-positive cell population towards high CD44 expression. This study highlights differential responses of tumor cells to CCR2 antagonists in the presence of different oxygen saturations and expands our knowledge of compensatory mechanisms leading to CCL2-CCR2 treatment resistance.

Hypoxia inducible factor-1ɑ as a potential therapeutic target for osteosarcoma metastasis

Osteosarcoma (OS) is a malignant tumor originating from mesenchymal tissue. Pulmonary metastasis is usually present upon initial diagnosis, and metastasis is the primary factor affecting the poor prognosis of patients with OS. Current research shows that the ability to regulate the cellular microenvironment is essential for preventing the distant metastasis of OS, and anoxic microenvironments are important features of solid tumors. During hypoxia, hypoxia-inducible factor-1α (HIF-1α) expression levels and stability increase. Increased HIF-1α promotes tumor vascular remodeling, epithelial-mesenchymal transformation (EMT), and OS cells invasiveness; this leads to distant metastasis of OS cells. HIF-1α plays an essential role in the mechanisms of OS metastasis. In order to develop precise prognostic indicators and potential therapeutic targets for OS treatment, this review examines the molecular mechanisms of HIF-1α in the distant metastasis of OS cells; the signal transduction pathways mediated by HIF-1α are also discussed.