Abstract B161: SLC1A5 inactivation induces apoptosis-mediated cells death in non-small cell lung cancer.

Abstract

Abstract Introduction: We recently reported that solute carrier family A1 member 5 (SLC1A5) controls glutamine (GLN) uptake and modulates cell growth, oxidative stress and mTOR signalling pathway. SLC1A5 is a transmembrane, high affinity glutamine transporter that is overexpressed and located at the plasma membrane in non-small cell lung cancer (NSCLC). GLN deprivation has been shown to induce cell death in several types of cancers, however the exact mechanism by which SLC1A5 targeting affects NSCLC survival remains unknown. We hypothesize that inhibition of SLC1A5 deprives cells from GLN which induces autophagy which eventually leads to cell starvation and ultimately apoptotic cell death. Methods: To test our hypothesis we targeted SLC1A5 by siRNA or by its specific inhibitor, GPNA, in a panel of 6 NSCLC lung cancer cell lines (express high level of SLC1A5). For comparison 2 human bronchial epithelial cell lines (HBEs) (express low level of SLC1A5) were used. The effects of targeting SLC1A5 on growth, GLN uptake, ATP level, autophagy, and cell death were examined. Markers of autophagy and cell death were analysed using western blot, nuclear staining and cell cycle analysis. Results: SLC1A5 inactivation by GPNA or by siRNA resulted in a significant decrease in cellular GLN uptake in NSCLC cell lines, while HBE cell lines were unaffected. Decrease in GLN uptake was accompanied by an increase in autophagy as evident by decrease in cell size, increase of LC3-II and decrease if LC3-I markers of autophagy. In addition, we observed a significant drop in ATP levels by 2 folds with increasing doses of GPNA. Markers of internal apoptotic pathway that include decrease of mitochondrial potential and cleaved caspases-3 and 9 were detected in response to increasing doses of GPNA. No change was observed in external apoptotic markers, caspases 8 or 1. In addition a 2-10 fold increase (based on the cell line) of sub-G1 was observed in NSCLC cell lines but not in HBE cell lines. Conclusion: Our results show that targeting SLC1A5 in NSCLC cells induces apoptotic cell death. Cells starve due to GLN deprivation and undergo autophagy which leads to a decrease in ATP level resulting in apoptotic cell death. These findings suggest that targeting SLC1A5 may have therapeutic implications in NSCLC. Grant funding: Lung Cancer Research Foundation Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B161. Citation Format: Mohamed Hassanein, Jun Qian, Megan Hoeksema, Marie Jacobovitz, Fredrick T. Harris, Bradford Harris, Pierre P. Massion. SLC1A5 inactivation induces apoptosis-mediated cells death in non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B161.