Bone Abstracts

Objectives: Osteosarcoma is the most common primary bone cancer and most frequent cause of cancer-related deaths in children and adolescents. Osteosarcoma cells are able to establish a crosstalk with resident bone cells leading to the formation of a deleterious vicious cycle. We hypothesized that osteosarcoma cells can release in the bone microenvironment transforming Extracellular Vesicles (EVs) involved in regulating the bone cell proliferation and differentiation, thereby promoting the tumour growth. So, our aims are to assess the EV production by osteosarcoma cells and to investigate the role of EVs in the communication between osteosarcoma cancer cells and normal recipient cells.

Methods: We used human osteosarcoma cell lines to set protocols aimed at isolating, visualizing and quantifying EVs. Once characterized, osteosarcoma-derived EVs were used to treat murine fibroblast cell line, NIH3T3. We studied the effects of tumoral EVs on normal NIH3T3 by cell count, cell cycle and apoptosis analyses. In order to verify tumoral-like phenotypes, we analyzed EV-treated NIH3T3 by wound healing, to test migration and soft agar assays, to assess anchorage-independent growth. Moreover, by exploiting the usage of human EVs and mouse recipient cells, we studied the presence of human osteoblastic and tumorigenic mRNAs in EV-treated NIH3T3 by using PCR assay.

Results: Our results showed that osteosarcoma cell lines are able to produce EVs that, in turn, induce tumour-like phenotype in recipient murine fibroblasts. In detail, EV-treated NIH3T3 showed an enhanced survival capability under low-serum conditions, high levels of activated survival pathways, an increased migration and the acquired capability to grow in an anchorage-independent manner. Moreover, in EV-treated NIH3T3 we found a de novo expression of specific mouse markers involved in osteoblastic differentiation and tumorigenesis, such as murine ALkaline Phosphatase (ALP) and Matrix MetalloProteinase (MMP)-9. Surprisingly, we also found the expression of human markers, as ALP and TNF-α, in EV-treated NIH3T3.

Conclusions: Our results demonstrate the ability of osteosarcoma-derived EV to transfer mRNAs and to induce tumoral-like phenotypes in normal recipient cells. Taken together, these findings highlight a crucial role of EVs in mediating tumoral transformation of normal cells.

Disclosure: The authors declared no competing interests.