Abstract 1428: Targeting metabolic alteration in cisplatin-resistant lung cancer
Authors: Wangpaichitr Medhi , Wu Chunjing , Li Ying Ying , Chen Shumei , You Min , Dinh Vy , Feun Lynn G. , Kuo Macus T. , Savaraj Niramol 
Published: May 2015

Abstract
We have discovered that all cisplatin resistant (CR) lung cancer cells are less reliant on glycolysis while increasing oxidative metabolism and mitochondrial numbers. Here, we showed that glutamine withdrawal has a detrimental effect on CR cell lines, especially in non small cell lung cancer (NSCLC) CR cells. We assayed for glutaminase, a key enzyme in glutaminolysis pathway and found a significant decrease in protein expression and activity in all our CR cells (n=8, P&lt;0.01). Likewise, NSCLC-CR also take up twice as much L-[G-3H] glutamine when compared to its parental counterpart (n=4, p&lt;0.05). Interestingly, we did not observe significant glutamine uptake in small cell lung cancer (SCLC) CR cells (n=4, P&gt;0.05). Since not all CR cells exhibited similar sensitivity to glutamine withdrawal, we further explored other key amino acids which may be used in TCA cycle. We have found that NSCLC-CR lost argininosuccinate synthetase (ASS) expression while SCLC-CR showed an increase. ASS is a key enzyme in urea cycle to regenerate arginine. Thus, NSCLC-CR will depend on exogenous arginine for their survival. Moreover, arginine in the urea cycle can be used to generate glutamate via proline pathway using P5CDH (pyrroline-5-carboxylate dehydrogenase) which may explain why NSCLC-CR are auxotrophic for both arginine and glutamine. To investigate this possibility, we have studied P5CDH expression in all CR cells and their parental cells in complete and glutamine-free media. We have found that NSCLC-CR has significantly less to non-detectable levels of P5CDH and cannot be upregulated upon glutamine deprivation, while its parental cells have higher P5CDH expression which is further upregulated on glutamine deprivation. In contrast, SCLC-CR has significantly higher P5CDH expression compared to its parental cells and both can be upregulated upon glutamine deprivation. To further confirm this finding, we have overexpressed ASS using the pCMV6 vector containing full length ASS cDNA in NSCLC cells (SCASS). These transfected cells were able to withstand arginine free media compared to the NSCLC-CR transfected with empty vector (10% of NSCLC-CR cells were viable after 72hrs in arginine free media compared to 90% of SCASS were still viable). SCASS also took up less glutamine and was able to withstand glutamine free media when compared to NSCLC-CR. Furthermore, SCASS expressed higher levels of P5CDH and was further upregulated upon glutamine withdrawal. Our data demonstrate a complex metabolic network between arginine, proline, and glutamine. The derangement of the key enzymes which are necessary for generation of these amino acids can be exploited for future clinical application to selectively kill cisplatin resistant cells and improve treatment outcome in lung cancer patients. Supported by Department of Veterans Affairs, CDA2 award.
Citation Format: Medhi Wangpaichitr, Chunjing Wu, Ying Ying Li, Shumei Chen, Min You, Vy Dinh, Lynn G. Feun, Macus T. Kuo, Niramol Savaraj. Targeting metabolic alteration in cisplatin-resistant lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1428. doi:10.1158/1538-7445.AM2014-1428