Abstract 4097: Targeting of mTOR mediated signaling pathways in papillary thyroid cancer cell.

Abstract

Abstract The mammalian target rapamycin (mTOR) signaling cascade is a key regulatory pathway controlling initiation of mRNA in mammalian cells. Torin2 is a potent, selective and orally available mTOR inhibitor for treatment of cancer. Dysregulation of mTOR signaling has been found in many cancers, however its role Papillary Thyroid Cancer (PTC) has not been explained. Therefore in this study, we investigated the role of mTOR and its associated molecules in PTC cell lines using MTT, flow cytometry and DNA fragmentation assays and western blotting. Our data showed that Torin2 caused a dose dependent growth inhibition in all cell lines studied. Cell cycle assay showed that the sub-G1 population in TPC-1 cell increased from 12.44% in untreated control sample to 31.50% after 200nM of Torin2 treatment and 44.08% after 400nM of Torin2 treatment for 48 hours. Similarly BCPAP cells increased from 8.47% in untreated control sample to 33.54% after 200nM of Torin2 treatment and 41.16% after 400nM of Torin2 treatment for 48 hours. Further confirmation using FITC-conjugated Annexin V and PI assay showed that apoptotic cell increased from 8.89% in untreated cells to 58.54% and 73.54% after 200nM and 400nM treatment in TPC-1 cells, and from 13.24% in control to 46.74% and 70.64% in BCPAP cells, indicating a dose dependent apoptosis induced in both cell lines. Treatment of PTC cell lines with Torin2 inactivated downstream targets of mTOR; p70S6 and 4E-BP1. Torin2 treatment of PTC cell lines also induced mitochondrial dependent apoptosis via activation and cleavage of caspase-9, and 3, and cleavage of PARP. Furthermore Torin2 positively regulated autophagy by disrupting the Beclin-1 complex, releasing Beclin-1 to induce autophagy. Our results suggest mTOR and its associated signaling pathway play a critical role in PTC tumorigenesis, therefore targeting of mTOR expression may be a viable therapeutic intervention for treatment of these cancers. Citation Format: Maqbool Ahmed, Azhar R. Hussain, Fouad Al Dayel, Shahab Uddin, Khawla S. Al-Kuraya. Targeting of mTOR mediated signaling pathways in papillary thyroid cancer cell. [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 4097. doi:10.1158/1538-7445.AM2013-4097