PPARgamma Ligand-Induced Decrease of in vivo Tumor Growth Accompanied by Increased Cytolytic Activity of Splenocytes

Jang, Kyu Yun; Yu, Ki Hoon; Lee, Hak Yong; Kim, Kyung Ryoul; Choi, Ha Na; Cha, Eun Jung; Park, Ho Sung; Moon, Woo Sung; Kang, Myoung Jae; Lee, Dong Geun

Abstract

BACKGROUND: Recent studies have proposed the use of peroxisome proliferator activated receptor-gamma (PPARgamma) ligands as new chemotherapeutic agents for human malignant tumors. However the in vivo mechanism of PPARgamma ligands on cellular toxicity is not clear. Therefore we examined the anti-tumor effects of the PPARgamma ligand, rosiglitazone (ROS), in animal models.
METHODS
To evaluate the effect of RSO on splenocytes, an in vitro and in vivo study was performed. Cytolytic activity was measured by use of a 51Cr release assay. The splenic natural killer (NK) cell population and effector-target conjugation were measured by flow cytometric analysis.
RESULTS
In 9L glioma bearing rats, 30 mg/kg/d of ROS treatment induced a significant decrease of subcutaneous tumor growth accompanied by an increased cytolytic activity of splenocytes and of the splenic NKR-P1bright/CD3- NK cell population. In normal rats, systemic administration of ROS also increased the cytolytic activity of splenocytes, the splenic NK cell population, and effector-target conjugation. Moreover, we found that a concentration of 20micrometer ROS caused an increase in the cytolytic activity of splenocytes, and a concentration of 50micrometer ROS increased effector-target conjugation in vitro.
CONCLUSIONS
These results suggest that increased splenic cytolytic activity and NK cell population may contribute to the anti-tumor effects of PPARgamma ligands in vivo. However, the roles of NK cells in the PPARgamma ligand-induced anti-tumor activity should be further investigated.