Abstract 884: A metabolomics approach to identify differences between P-glycoprotein (ABCB1) expressing drug resistant and sensitive cancer cells.
Authors: Shukla Suneet , Schwartz Candice , Ambudkar Suresh V. 
Published: August 2014

Abstract
P-glycoprotein (P-gp) is an ABC transporter whose expression in various human cancers including hepatocellular, lung and colon carcinomas often correlates with resistance to chemotherapeutics. Its activity not only affects the pharmacokinetics of therapeutic agents but also protects cells against xenobiotics and causes drug resistance in cancer cells. Although it is known that P-gp transports a wide variety of chemically dissimilar compounds, its function in the normal cellular milieu is poorly understood. This is primarily due to insufficient knowledge concerning what substrates it transports in vivo and how its expression is regulated. Identification of P-gp's physiological substrates and the pathways that regulate its function would help to reveal unknown roles of this transporter that may lead to new ways to overcome therapeutic drug resistance. This information would also be of great significance in predicting the pharmacokinetic and toxicological properties of novel drug candidates. In this study, we used a global metabolite profiling approach to identify and characterize P-gp expression-associated changes in the metabolic fingerprint of cells. P-gp was functionally expressed using a modified baculovirus based (BacMam) expression system to identify the metabolomic changes induced due to expression of Pgp in HeLa cells. A functionally dead mutant P-gp (E556Q/E1201Q) and a non-specific green fluorescent protein (BacMam-GFP) were expressed as negative controls for P-gp activity and viral transduction, respectively. Relative changes in chemical concentrations of small molecule metabolites including amino acids, carbohydrates, lipids, cofactors and nucleosides produced in response to expression of functional P-gp were evaluated to determine their effect on biochemical pathways. P-gp-positive cells had lower levels of glucose, acetyl-coA, citrate, malate and fumarate, which are components of the TCA cycle. Six structurally unidentified compounds were also significantly lower in P-gp-expressing cells. An overall lower metabolic state in virally transduced P-gp-expressing cells was observed. The difference in the metabolic state of the P-gp-expressing cells is currently being validated by transport- or mass spectrometry- based assays. The data presented here thus provide a global view of cellular networks and processes initiated when a drug-sensitive cell becomes drug-resistant due to expression of P-gp and bring to light new information about the physiological and pharmacological relevance of P-gp and other ABC drug transporters.
Citation Format: Suneet Shukla, Candice Schwartz, Suresh V. Ambudkar. A metabolomics approach to identify differences between P-glycoprotein (ABCB1) expressing drug resistant and sensitive cancer cells. [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 884. doi:10.1158/1538-7445.AM2013-884