Explore the Pivotal Role of Uncoupling Protein 2 in Cellular Anti-Oxidative Stress in Lung Cancer---Focusing on the Correlation with NRF2 and HLFT and Their Application in Cancer Treatment

Combination chemotherapy with anti-survival agents will increase therapy efficacy. Uncoupling protein 2 (UCP2), located in the inner mitochondrial membrane, functions as a negative ROS regulator. In lung cancer cells with lower UCP-2 expression, chemotherapy induced cellular survival via mitochondrial ROS/ Stat3 pathway. We may block chemotherapy-induced survival by using ROS inhibitors to increase therapy effect in low UCP-2 expression cancer cells. Since ROS inhibitors have dual role in cancer treatment, we suggested in lower UCP-2 expression cancer cells, combined chemotherapy and ROS inhibitors provide better efficacy (Cacinogenesis 33(11): 2065-75, 2012). However, the role of UCP-2 modulating cancer biology is largely unknown. In lower UCP-2 expression CL1-5 cancer cells, stably overexpressing UCP-2 cancer cells had negative impact on cells’ migration and proliferation, compared to vector control cells. There are some reports in normal cells that UCP-2 regulates cellular migration is through beta2 integrin and Src-FAK signaling (Clin Exp Metastasis 2012;29:901&Arterioscler Thromb Vasc Biol.2004;24:864) and that UCP-2 modulates proliferation is via MARK/ERKpathway and glycolysis (JBC 2008;283:30461 & FASEB J. 2008;22:9). The mechanism will be elucidated in the Aim I. In lung cancer, NrF2 activation may lead to cell growth and chemoresistance. There were many cAMP-response element binding protein (CREB) in the promoter area of the UCP-2 gene and Nrf2 cooperatively bind CBP, a CREB-binding protein, and synergistically activate transcription (BBRC 1999;265:326 & Genes Cells 2001;6:857). We assume that NrF2 may regulate UCP-2. In our lung cancer tissue array and cells, NrF2 has positive correlation with UCP-2. In low UCP-2 expression cells, suppressing NrF2 led to UCP-2 down-reguation; however, it made the cells more sensitive to cisplatin. MAPK, Akt, PKC and autophagy have been demonstrated to regulate NrF2 gene (Free Radic Biol Med.2012;52:1054) and we may study the interaction between NrF2 and UCP-2 via NrF2 overexpressing and silencing system (from 國衛院郭靜娟副研究員) in lower UCP-2 expression cancer cells. (Aim II) ROS causes DNA damage and HLTF is involved in post-replication repair. There is undefined role of HLTF in carcinogenesis and chemoresistance. In our result, cisplatin-resistant nasopharyngeal carcinoma cell lines (Hone-6) possessed higher HLTF expression, compared to parental Hone-1 cells. In Hone-6 cells, down-regulation of HLTF by shRNA (from 成大廖泓鈞助理教授) increases cellular sensitivity to cisplatin. In lung cancer tissue array, HLTF promotes lung carcinogenesis; whereas in advanced lung cancer, cancer cells with lower UCP-2 expression may possess higher HLTF expression, and, down-regulation with HLTF attenuated chemoresistance in lower UCP-2 expression cancer cells. According to statement from 成大廖泓鈞助理教授, HLTF interacts with PARP1 and DNA-PK, we assume that chemoresistance to cisplatin in lower UCP-2 expression cancer cells may result from Akt activation or RPA2 hyperphosphorylation (Neoplasia. 2011;13:1069 & Biochem Pharmacol. 2009;77:1348 & PLoS One. 2011;6(6):e21424). Further study will be done to prove our concept. We may study the interaction between HLTF and UCP-2 via Flag-tagg stable HLTF system. (Aim III) We have make PLGA nanoparticles (NPs) codliver paclitaxel and siRNA to improve cancer treatment (Int J Nanomedicine. 2012;7:4269). However, our nano-delivery drug can not work in vivo because they were uptaken by reticulo-endothelial system intravenously. Since siRNA against NrF2 and HLTF reduce cellular resistance to chemotherapy in preliminary, under the cooperation with 成大葉晨聖教授, we will synthesize chitosan-PEG blended PLGA NPs (Eur J Pharmacol. 2011;670:372) to codeliver anticancer drug and siRNA against NrF2 and HLTF to improve cancer treatment via intravenous route in vivo. In the future, ligand-guided chitosan-PEG blended PLGA NP will give the NPs to the specific site to exert anti-cancer function. (Aim IV)