Abstract 2541: Anti-tumor efficacy of molecular targeted agents in osteosarcoma
Authors: Kwon Bo Ram , Jung Jae-Joon , Jeung Hei-Cheul , Shin Kyoo-Ho , Kim Tae Soo , Chung Hyun Cheol , Roh Jae Kyung , Rha Sun Young 
Published: February 2011

Abstract
Osteosarcoma (OS) is the most common malignant bone cancer which is characterized by local invasion and distant metastasis. With the use of multi-agent chemotherapy, there have been improvements in the overall survival. However, drug resistance still remains a problem resulting in poor outcome. Currently, targeted agents are being evaluated as a novel method for various cancers, but the efficacy of the agents in OS is not well known.
We examined the protein expression of c-Met, Akt, mTOR and their phosphorylated status in seven OS cell lines (MG-63, HOS, KHOS/NP, SK-ES-1, U-2OS, Saos-2, and G-292) using western blot. In addition, we evaluated the protein expression of PTEN, a negative regulator of PI3K/Akt/mTOR signaling pathway. To determine the efficacy of the targeted agents in OS, PHA-665752 (c-Met inhibitor) and Akti2-1/2 (Akt inhibitor) were evaluated in OS cell lines using the standard MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The drug concentration at which 50% of cells survived (IC50, μM) was calculated using Calcusyn software. Results were expressed as percent cell survival, which is calculated using the following formula: % survival = [(mean absorbance of test wells - standard absorbance) / (mean absorbance of control wells - standard absorbance)] × 100.
Seven OS cell lines had various expression levels of c-Met and p-Met with similar patterns. High levels of the Akt were observed in all the cell lines, but the levels of p-Akt varied. All the cell lines similarly expressed moderate levels of p-mTOR and PTEN. We observed that two cell lines, HOS and KHOS/NP, which both had high expression of c-Met and p-Met were sensitive to PHA-665752, less than 1.0 uM of IC50s. The IC50s of the other five cell lines were higher than 1.0 uM, suggesting resistant to PHA-665752. Especially, Saos-2 c resistant to PHA-665752 (IC50 &gt; 5uM) while showing high c-met and p-met expression with the highest p-Akt expression. The high expression of p-Akt seemed to be an alternative survival factor in the presence of PHA-665752. As we expected, there was a negative correlation between p-Akt and PTEN. Although p-Akt expression in OS cell lines differed, five of seven cell lines were evenly sensitive to Akti2-1/2, probably due to high expression of Akt in all cell lines.
In this study, we presented that osteosarcoma cell lines had various activated status and the targeted agents were effective when the c-Met and Akt were expressed. These targeted agents could be applicable in osteosarcoma by blocking the survival signaling pathway with single or combination treatment.
This work was supported by the Brain Korea 21 Project for Medical Science, Yonsei University
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 2541.