Abstract 2100: Preclinical evaluation of PF-04691502 in nasopharyngeal carcinoma.

Abstract

Abstract Nasopharyngeal carcinoma (NPC) is common in Southeast Asia. PF-04691502 (PF) is a novel potent dual inhibitor of PI3K/mTOR capable of inhibiting downstream effectors Akt, S6 and 4E-BP1, resulting in suppression of protein synthesis and cell survival. Five NPC cell lines include two well differentiated cell lines CNE-1 and HK1, two poorly differentiated NPC cell lines CNE-2 and HONE-1, and an undifferentiated NPC cell line C666-1 were selected for this preclinical study. All cell lines expressed basal level of Akt and p70S6K in both phosphorylated and total forms. The cytotoxicity of PF on NPC was evaluated by MTT assay. Cells were incubated in PF with increasing concentration (0.1nM, 50nM, 100nM, 200nM, 500nM, 1μM and 10μM) in culture medium for either 48 hours or 72 hours. Maximum growth inhibition was achieved in over 80% in 72 hours of PF incubation. The IC50 of all cell lines were in hundred nanomolar range (CNE-1 = 276nM, CNE-2 = 84nM, HK1 = 121nM, HONE-1 = 157nM and C666-1 = 395nM). Two most sensitive cell lines (CNE-2 and HK1) together with the least sensitive one (HONE-1) were selected to further evaluate the effect of PF on cell cycle, apoptosis and Akt signaling. Cells treated with either 100nM or 500nM PF for 6 hours and 24 hours were evaluated by cell cycle analysis and G0/G1 arrest was observed at 24 hour time point. Apoptotic effect was indicated by increasing cleaved PARP expression in which 500nM PF treatment for 24 hours induced apoptosis in CNE-2 and HK1 but not in HONE-1. At 48 hours, a lower dose of PF at 100nM could induce apoptosis in all NPC cell lines. The expression of pi-mTOR, pi-p70S6K, pi-Akt(S473), pi-Akt(T308), pi-S6 and pi-4EBP1 was inhibited in by PF, suggesting its effectiveness in anti-proliferation and inhibition of protein synthesis. Antitumor activity was observed in NPC xenograft model after 2 weeks of 10mg/kg PF administration to tumor bearing female athymic nude mice. Both tumor volume and tumor weight in the treatment group were significantly smaller and lighter than that in vehicle group (3.17cm3 vs. 5.58cm3 at 18 days, p=0.005 and 146mg vs. 284mg, p=0.001 respectively) while the body weight between groups were comparable, suggesting this working dose was well-tolerated. The beneficial effects of PF-09641502 in both in vitro and in vivo studies for NPC warrant a further investigation. Acknowledgement: This work is supported by an independent research grant from Pfizer. *Co-authorship Citation Format: Herbert H. Loong, Eric C H Wong, Connie W C Hui, Cecilia P Y Lau, Edwin P. Hui, Brigette B Y Ma, Anthony T C Chan. Preclinical evaluation of PF-04691502 in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2100. doi:10.1158/1538-7445.AM2013-2100