The opportunistic uptake of extracellular molecules has been named as a key emerging hallmark of cancer metabolism[1]. Extracellular ATP (eATP) levels of various cancer types are 103 to 104 times higher than those in their corresponding normal tissues[2]. However, the biological significance of the high ATP concentrations is not clear. We recently reported that cancer cells uptake extracellular ATP via different endocytoses to enhance growth, survival, and drug resistance to tyrosine kinase inhibitors (TKIs)[3 ,4]. We hypothesized that eATP induces resistance to TKIs by endocytoses-mediated internalization of eATP, which competes with TKIs for the ATP-binding site of receptor TKs (RTKs), phosphorylating and activating RTKs and RTK-mediated signaling pathways. In contrast to previous reports that synthesized intracellular ATP (iATP) elevation contributed acquired drug resistance, here we report a novel intrinsic drug resistance in which eATP was internalized and substantially increased iATP levels and promoted cancer cell drug resistance to the TKI sunitinib in human NSCLC A549 cells. The iATP level elevation and drug resistance were mediated primarily by macropinocytosis. The resistance was reduced when macropinocytosis was suppressed by inhibitors or an siRNA knockdown of a key micropinocytosis protein PAK1. Intracellularly, the elevated iATP upregulated phosphorylation of PDGFR and proteins/enzymes in the PDGFR-mediated Akt-mTOR and Raf-ERK signaling pathways, resulting in reduced apoptosis triggered by sunitinib. Furthermore, both in vitro and in A549 tumors, eATP partially restored phosphorylation levels of PDGFR and PDGFR-mediated proteins/enzymes suppressed by sunitinib. The resistance cannot be accounted for by the overall purinergic receptor-mediated signaling, glycolysis, or mitochondrial OXPHOS. These results strongly suggest that the eATP-elevated intracellular ATP levels reversed the inhibition of TKIs by using the mechanism we hypothesized, linking for the first time the ATP-rich tumor microenvironment with cancer drug resistance. All these findings significantly expand our understanding of the roles of extracellular ATP in cancer, and offer new anti-drug resistance targets. 1. Pavlova N, Thompson C. Cell Metab. (2016) 23:27-47. 2. Falzoni et al., Interface Focus.(2013) 3: 20120101. 3. Qian Y, Wang X, et al., Cancer Lett. (2014)351: 242-5. 4. Qian Y, Wang X et al., Mol Cancer Res (2016) 14:1087-96

Citation Format: Xuan Wang, Yunsheng Li, Yanrong Qian, Yanyang Cao, Xiaozhuo Chen. A new mechanism of drug resistance in cancer: extracellular ATP-induced resistance through ATP internalization and upregulation of protein phosphorylation in Akt and ERK pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3194. doi:10.1158/1538-7445.AM2017-3194