Development and characterization of the novel human osteosarcoma cell line COS-33 with sustained activation of the mTOR pathway
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Ashley VanCleave1, Mykayla Palmer1,2, Fang Fang1, Haydee Torres1,3, Tania Rodezno1, Qilin Li4, Kirby Fuglsby1,5, Claire Evans1, Yohannes Afeworki6, Alan Ross7, Pulivarthi Rao8, Patricia Leiferman9,10, Siyuan Zheng4, Peter Houghton4 and Jianning Tao1,3,5,10
1 Cancer Biology and Immunotherapies Group, Sanford Research, Sioux Falls, SD, USA
2 SPUR Scholar Program, University of South Dakota, Sioux Falls, SD, USA
3 Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD, USA
4 Greehey Children’s Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
5 Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD, USA
6 Functional Genomics & Bioinformatics Core Facility, Sanford Research, Sioux Falls, SD, USA
7 Sanford Medical Genetics Laboratory of Sanford Health, Sioux Falls, SD, USA
8 Texas Children’s Cancer and Hematology Centers, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
9 EGL Genetics Laboratory, Tucker, GA, USA
10 Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD, USA
Keywords: osteosarcoma; COS-33; mTOR; osteogenic differentiation; TP53
Received: February 21, 2020 Accepted: May 01, 2020 Published: July 07, 2020
Outcomes have not improved for metastatic osteosarcoma for several decades. In part, this failure to develop better therapies stems from a lack of understanding of osteosarcoma biology, given the rarity of the disease and the high genetic heterogeneity at the time of diagnosis. We report here the successful establishment of a new human osteosarcoma cell line, COS-33, from a patient-derived xenograft and demonstrate retention of the biological features of the original tumor. We found high mTOR signaling activity in the cultured cells, which were sensitive to a small molecule inhibitor, rapamycin, a suppressor of the mTOR pathway. Suppressed mTOR signaling after treatment with rapamycin was confirmed by decreased phosphorylation of the S6 ribosomal protein. Increasing concentrations of rapamycin progressively inhibited cell proliferation in vitro. We observed significant inhibitory effects of the drug on cell migration, invasion, and colony formation in the cultured cells. Furthermore, we found that only a strong osteogenic inducer, bone morphogenetic protein-2, promoted the cells to differentiate into mature mineralizing osteoblasts, indicating that the COS-33 cell line may have impaired osteoblast differentiation. Grafted COS-33 cells exhibited features typical of osteosarcoma, such as production of osteoid and tumorigenicity in vivo. In addition, we revealed that the COS-33 cell line retained a complex karyotype, a homozygous deletion of the TP53 gene, and typical histological features from its original tumor. Our novel cellular model may provide a valuable platform for studying the etiology and molecular pathogenesis of osteosarcoma as well as for testing novel drugs for future genome-informed targeted therapy.
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