Abstract 2064: Down-regulation of miR-31 is associated with metastatic potential of human and canine osteosarcoma

Abstract

Abstract Osteosarcoma is the most common primary bone tumor in humans and dogs. The primary cause for the poor survival of patients with osteosarcoma in both species is the emergence of metastases in organs distant from the primary tumor, especially in the lung. Therefore, identification of molecular determinants of osteosarcoma metastasis is highly warranted. In order to identify microRNAs (miRNAs) that regulate osteosarcoma metastasis, we examined, using qRT-PCR, levels of 10 miRNAs commonly associated with cancer metastasis (miR-10b, miR-146a, miR182, miR183, miR-206, miR-335, miR373, miR-520c-5p, miR-21 and miR-31) in total RNA samples prepared from canine parental osteosarcoma (POS) and highly metastatic POS (HMPOS) cells. Of the 10 miRNAs, only miR-31 showed differential expression between the two cell lines (reduced by 7.8-fold in HMPOS cells versus POS cells). Exposure of HMPOS cells to various chemopreventive agents (myo-inositol, indole-3-carbinol, diindolylmethane, deguelin, phenethyl isothiocyanate, cisplatin, and aza-2′-deoxycytidine) increased the level of miR-31 at least by two-fold, the most potent agents being deguelin and phenethyl isothiocyanate. Subsequently, we assessed the expression of miR-31 in additional canine osteosarcoma cell lines (three cell lines established from primary tumors and three cell lines developed from pulmonary metastases) and human osteosarcoma cell lines differing in metastatic potential (parental SaOS2, low- (LM2), and high- (LM7) metastatic cells). miR-31 levels decreased by 18-fold in canine cell lines derived from pulmonary metastatic tumors relative to that obtained from primary tumors and by 2-fold and 3-fold in LM2 and LM7 cells, respectively, compared to the expression in parental Saos-2 cells. Also, analysis of 3 primary human osteosarcoma tissues and 3 pulmonary metastatic tissues revealed a 13-fold reduction of miR-31 in metastatic tissues relative to primary tumor tissues. In preliminary experiments where attempts were made to identify potential targets of miR-31, exogenous over-expression of a synthetic miR-31 cassette in HMPOS cells negatively regulated a tight junction protein claudin-2, which is incriminated in cancer metastasis. In summary, our studies indicate that miR-31 is a promising marker for the metastatic potential of osteosarcoma and for disease prognosis. Moreover, reactivation of silenced miR-31 by chemopreventive/chemotherapeutic agents could reverse osteosarcoma metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2064.