Abstract C80: Characterization of metastatic cancer stem cells in osteosarcoma

Abstract

Abstract Pulmonary metastasis is the leading cause of death in osteosarcoma (OS), the most common malignant bone tumor in children and young adults. The molecular mechanisms that regulate the formation of metastases in OS remain mostly unknown. A subset of cancer stem cells (CSCs) with metastatic potential has been identified in breast, colon and pancreatic cancers. Therefore, we hypothesize that CSCs drive the metastatic process in OS by their ability to migrate, adapt to a different microenvironment, and subsequently generate distal metastatic lesions in the lungs. Using a novel mutant p53 mouse model of metastatic OS, which has been developed in Dr. Jason Yustein's laboratory, we have identified putative OS CSCs in primary bone tumors and metastatic lesions. Cancer stem cells have been cultured from solid tumors growing as sphere-like structures under serum-free conditions. This method has been validated as a surrogate of their self-renewal capacity. We have observed that murine tumor cells obtained from both primary bone tumors and pulmonary nodules developed sarcospheres. Notably, sarcophere-forming efficiency was significantly increased (2-3 times) in tumor cells obtained from metastatic lesions. Aldehyde dehydrogenase 1 (ALDH1) activity has been used as a functional stem cell marker to isolate CSCs in numerous solid tumors. We have found that both primary bone tumors and metastatic pulmonary nodules contain ALDH Hi (stem-like cells). The high expression of ALDH1 in murine OS tumors ranged from 0.7 to 17%. Further analysis of derived cell lines generated from primary OS tumor, circulating tumor cells (CTCs) and metastatic tumors showed that distal metastases have 4-5 times more ALDH Hi cells than CTCs and up to 10 times more ALDH Hi cells than the primary bone tumors. The isolation of OS CSCs by fluorescent activated cell sorting (FACS) facilitates the analysis of the molecular pathways and biological process that regulates this tumor cell compartment. Our initial data has shown that the Insulin-like Growth Factor (IGF) family members were differentially expressed between OS primary and metastatic cells. Furthermore, we are actively utilizing these mouse derived cell lines to perform orthotopic transplants in immunocompetent (syngeneic) mice aiming to better understand the biology and genetics of CSCs in OS. Subsequent studies will be performed to determine the functional significance of the unique OS CSC genetic alterations. In summary, we have identified putative metastatic OS CSCc in a mutant p53 mouse model of metastatic OS. Our preliminary data has shown that CSC content seems to be increased in metastases. Our studies using an OS mouse model that parallels the biological behavior of human disease in addition to provide freshly isolated tumor specimens constitute a strong pre-clinical model to test the effect of novel anti-cancer therapies in the CSC compartment. Citation Format: Nino Rainusso, Lyazat Kurenbekova, Lawrence Donehower, Jeffrey Rosen, Jason Yustein. Characterization of metastatic cancer stem cells in osteosarcoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C80.