Circulating exosomes secreted by osteosarcoma cells are potential biomarkers for metastasis
Date
2021
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Osteosarcoma is a primary malignant bone tumor found in children and is the third most common cancer in children and adolescents. Upon diagnosis, patients undergo surgery and aggressive chemotherapy treatments resulting in a high prognosis for survival. However, once metastasis occurs, primarily to the lung, prognosis is poor. Recent chemotherapy clinical trials have provided few successes, leading researchers to look into other non-invasive biomarkers for therapeutic development. One way to obtain biomarkers is through the use of liquid biopsies which are body fluids obtained from cancer patients at diagnosis. These liquid biopsies provide a way to analyze what tumors are secreting into the bloodstream. The contents of these biopsies give insight into cancer progression and provide multiple avenues for diagnostic marker research. ☐ Exosomes are small extracellular vesicles that contain a multitude of biomolecules varying from proteins, DNA, RNA (e.g., mRNA and miRNAs), lipids, and metabolites. These nanoparticles are released by an origin cell into the bloodstream with content that is reflective of its origin. Exosomes are secreted by all cells but they are secreted at a higher rate from cancer cells compared to normal cells. Therefore, there is a higher concentration of tumor-derived exosomes in cancer patients that can be utilized as a way to track metastasis. In order to track metastasis in exosomes, a specific biomolecule in their cargo needs to be used as a cancer-specific target for tracking and screening throughout the body. Based on previous research, our lab focuses on p27/Kip1 protein as a potential target in osteosarcoma-derived exosomes. ☐ p27 is a tumor suppressor involved in cell cycle regulation when localized to the nucleus, but upon localization out into the cytoplasm it facilitates oncogenic activity. Cytoplasmic p27 acts as a oncoprotein and is involved in many cellular processes including cytoskeletal dynamics and cell migration, therefore it is associated with tumorigenesis and disease progression. With this key characteristic of osteosarcoma, further research is needed to assess if p27 in exosome cargo acts as a mechanism of metastasis. I hypothesize that p27 protein is secreted in exosomes by osteosarcoma cells and facilitates metastasis to the lung. ☐ In this study, I examined the expression of p27 in osteosarcoma-derived exosomes and the uptake of exosomes by human lung fibroblasts. I investigated p27 expression in osteosarcoma-derived exosomes from multiple osteosarcoma cell lines compared to normal cells using immunoblot analysis. I found that exosomes secreted by human osteoblasts and human lung fibroblasts did not contain p27 in their cargo, but all three osteosarcoma cell lines (143B, HOS, and MG63) did. After confirmation that p27 in exosomes is osteosarcoma specific, I evaluated the uptake of exosomes by human lung fibroblast cells. Using immunofluorescence and immunoblot analysis, I found that exosomes are taken up by lung fibroblasts thus influencing both the content and proliferation of the lung fibroblast cells. In summary, this data provides insight into the role of osteosarcoma-derived exosomes in metastasis and provide a potential source of biomarkers for therapeutic development.
Description
Keywords
Exosomes, Osteosarcoma