Heterogeneous pattern of gene expression in cloned cell lines established from a rat transplantable osteosarcoma lung metastatic nodule Kanya Honoki a , Toshio Mori b , Masahiro Tsutsumi c , Toshifumi Tsujiuchi c , Akira Kido a , Toru Morishita a , Yoshizumi Miyauchi a , Yoshiko Dohi d , Yoshio Mii e , Susumu Tamai a , Yoichi Konishi c, * a Department of Orthopedic Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634, Japan b RI Center, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634, Japan c Department of Oncological Pathology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634, Japan d Department of Public Health, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634, Japan e Surgical Center of Nara Medical University Hospital, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634, Japan Received 13 January 1998; accepted 5 February 1998 Abstract We have established three cloned cell lines (COS1NR, COS2NR and COS4NR) from the lung metastatic nodule of a highly metastatic variant of rat transplantable osteosarcoma, C-SLM. All three clones shared the same morphological characteristics and tumorigenicity, but their growth rates in vitro and metastatic ability in vivo differed from each other. Single-strand conformation polymorphism (SSCP) analysis revealed all three clones to have the same p53 gene mutation and parent C-SLM tumor. On the other hand, Northern blot analysis showed a different pattern of expression for the genes, c-fos, c-jun, c-Ha-ras, transin (rat stromelysin), bone Gla protein (osteocalsin) and nm23/NDP kinase. These results indicate the presence of a heterogeneous cell population in terms of the different pattern of gene expression in a lung metastatic nodule of rat osteo- sarcoma and the present newly established cell lines will be useful for further investigation of the biological behavior of osteosarcomas.  1998 Elsevier Science Ireland Ltd. Keywords: Osteosarcoma; Rat; Cell line; p53 mutation; Gene expression 1. Introduction Osteosarcoma is a common bone tumor with a poor prognosis due to its propensity for metastasis [1]. In order to understand the underlying mechanisms and modulation of the metastatic behavior of this tumor type, we have developed experimental models in rats which exhibit similar biological behavior to human cases [2]. Two highly metastatic transplantable tumor lines were established from spontaneous and chemical carcinogen (4-hydroxyamino quinoline 1- oxide (4-HAQO))-induced osteosarcomas, i.e. SOS and COS, respectively. We previously analyzed the Cancer Letters 127 (1998) 221–228 0304-3835/98/$19.00  1998 Elsevier Science Ireland Ltd. All rights reserved PII S0304-3835(98)00048-2 * Corresponding author. Tel.: +81 7442 23051, ext. 2576; fax: +81 7442 57338.