Abstract 2946: Status of STAT3, STAT5, and NF-κB in pancreatic cancer cell lines, small molecule inhibitors, and potential clinical implications

BACKGROUND: Pancreatic cancer (PC) is one of the most deadly forms of human cancer with 5-year survival less than 5%. Presently the nucleoside analog gemcitabine is used for front line disease management but its low response rate and the frequent development of drug resistance, which is poorly understood, limits its effectiveness. A large body of literature indicates that the STAT3, STAT5, and NF-κB pathways are active drivers of pancreatic cancer development and progression. Agents targeting STAT3 and NF-κB pathways are being actively being considered as potentially effective drugs and have been tested in in vitro and in vivo pancreatic tumor models with limited success. EXPERIMENTAL DESIGN: We aimed to reassess the role and function of these three transcription factors in a panel of PC cell lines and assess the activity of WP1066, our lead STAT3/STAT5 inhibitor, and its close congeners in the same lines. Our reevaluation studies of the oncogenic function of STAT3, STAT5 and NF-κB were carried out in 3 established pancreatic cancer cell lines (PANC-1, Colo357, and MIAPaCa2) and 2 primary tumor cell lines (MDAPATC53 and MDAPATC50) isolated from patient tumor specimens with known clinical features and available relevant in vivo models. PC cells were separately treated with cytokines (IL-6 and IFN-α), gemcitabine and TNF-α and fractionated into cytoplasmic and nuclear portions. Levels of p-STAT3, p-STAT5, and NF-κB were assessed using Western blot, MesoScaleDiscovery, DNA binding activity, and confocal methods. RESULTS: Collectively, our data showed that STAT3 was constitutively activated and that tyrosine-phosphorylated STAT3 (p-STAT3Y 705 ) is exclusively located in the nucleus of the ColoFG357 and MiaPaCa2 cell lines. IL-6 and IFN-α treatment induced p-STAT3Y 705 , and their combined use resulted in synergistically higher levels of p-STAT3Y 705 and in nuclear localization in all five PC cell lines. In contrast, and rather surprisingly, the tyrosine-phosphorylated STAT5Y 694 and NF-κB were mostly localized in the cytoplasm in all five cell lines. Consistent with these results, the DNA binding activity of p-STAT5 and NF-κB is very low compared to p-STAT3. Interestingly, our studies revealed that gemcitabine treatment triggers the nuclear accumulation of NF-κB in a time-dependent manner suggesting that a combination of gemcitabine with NF-κB inhibitors can have synergistic activity in PDAC. CONCLUSION: Our findings contribute to unraveling the functional significance of p-STAT3 and NF-κB as oncogenic transcription factors during pre- and post- gemcitabine treatment and the critical need to concurrently inhibit several targets and develop drug combinations or multitargeted drugs that block these pathways. Acknowledgement: This research was supported by the grant from Viragh9s Foundation. Citation Format: Arumugam Jayakumar, Venugopal Radjendirane, Jason Fleming, Yaan Kang, Aleksandra Rusin, Rafal Zielinski, Stanislaw Skora, Izabela Fokt, Waldemar Priebe. Status of STAT3, STAT5, and NF-κB in pancreatic cancer cell lines, small molecule inhibitors, and potential clinical implications. [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 2946. doi:10.1158/1538-7445.AM2014-2946