The synthetic ligand of PPARγ ciglitazone affects human glioblastoma cell lines

c) The number of text pages, number of tables, figures, and references, and the number of words in the Abstract, Introduction and Discussion (each item should be placed on a separate line) Text pages: 33 Number of tables: 1 Number of figures: 8 Number of references: 40 Number of words in the Abstract: 249 Number of words in the Introduction: 669 Number of words in the Discussion: 1 484 d) A list of nonstandard abbreviations used in the paper. RUNNING TITLE PAGE JPET #63438 3 Glioblastoma multiforme is the most common malignant brain tumour in adults, and it is among the most lethal of all cancers. Recent studies have shown that ligand activation of PPARγ can induce differentiation and inhibit proliferation of several cancer cells. In this study we have investigated whether one PPARγ ligand in particular, ciglitazone, inhibits cell viability and additionally whether it affects the cell cycle and apoptosis of human glioblastoma cell lines, T98G, U-87 MG, A172 and U-118 MG. All glioblastoma cell lines were found to express PPARγ protein and following treatment with ciglitazone, localisation was unchanged. Ciglitazone inhibited viability in a dose-dependent manner in all four tested glioblastoma cells after 24 hour treatment. Analysis of the cell cycle showed arrest in the G1 phase and partial block in G2/M phase of the cell cycle. Cyclin D1 and cyclin B expression was decreased. Phosphorylation of Rb protein dropped, as well. We found that ciglitazone was followed by increased expression of p27 Kip1 , p21 Waf1/Cip1. It also led to apoptosis induction; bax expression in T98G was elevated. Expression of the anti-apoptotic protein bcl-2 was reduced in U-118 MG and U-87 MG and showed a slight decrease in A172 cells. Flow cytometry confirmed the induction of apoptosis. Moreover, PPARγ ligand decreased telomerase activity in U-87 MG and U-118 MG cell lines. Our results demonstrate that ciglitazone inhibits the viability of human glioblastoma cell lines via induction of apoptosis and a result this ligand may offer potential new therapy for the treatment of CNS neoplasms. ABSTRACT JPET #63438 4 1. Glioblastoma The incidence of central nervous system neoplasm ranges from 3.8 to 5.1 cases per 100 000 in the population. Glioblastoma multiforme (GBM), the most common malignant brain tumor (34 %) in adults is among the most lethal of all cancers (Gurney and Kadan-Lottick, 2001). GBM composed of poorly differentiated neoplastic astrocytes, typically affects adults and is preferentially …