Abstract 3993: New paradigms for the modulatory actions of p38δ MAPK restorative expression in esophageal squamous cancer cell growth, migration and response to chemotherapy: A possible future therapeutic target.
Authors: O'Callaghan Carol , Fanning Liam , Houston Aileen , Barry Orla P. 
Published: August 2014

Background: Esophageal cancer is an aggressive tumour which responds poorly to both chemotherapy and radiation therapy and has a poor prognosis. Approximately half of patients diagnosed with localized esophageal cancer die of metastatic disease within the first 2 years following tumour resection. Thus, a greater understanding of the biology of esophageal cancer is needed in order to identify novel therapeutic targets. Among these targets p38 MAPK isoforms are becoming increasingly important for a variety of cellular functions. A better understanding of the role(s) of p38 MAPKs may provide useful therapeutic tools for the management of human cancers. Methods: We analysed p38 MAPK isoform expression in both cancer cell lines and corresponding human normal and tumour tissue including esophageal, liver, lung, prostate, colon, renal and pancreatic. We observed that over 75% of both cell lines and human tumour tissue samples fail to express the specific isoform p38δ MAPK. To evaluate the role(s) of p38δ and active p-p38δ MAPK in esophageal cancer progression we developed a series of constructs: p38δ MAPK (pcDNA3-FLAG-p38δ MAPK), active p-p38δ MAPK (pcDNA3-MKK6b(E)-(Gly-Glu)5-FLAG-p38δ) and inactive p38δDN MAPK (pcDNA3-MKK6b(E)-(Gly-Glu)5-FLAG-p38δDN). The active p-p38δ plasmid was generated by removing the MKK6b(E) stop codon in pcDNA3-MKK6b(E). Secondly, FLAG-p38δ was amplified with a 5′(Gly-Glu)5 linker. Linear blunt-ended pcDNA3-MKK6b(E) and blunt ended (Gly-Glu)5-FLAG-p38δ were ligated. The dominant negative p-p38δ plasmid (p-p38δDN) was generated from pcDNA3-MKK6b(E)-(Gly-Glu)5-FLAG-p38δ by replacing Thr180 with Ala and Tyr182 with Phe. Stable esophageal squamous cancer cell lines expressing these plasmids were generated. Results: Re-introduction of p38δ or p-p38δ proved to be (a) anti-proliferative, (b) anti-migratory and (c) pro-apoptotic. We observed a time-dependent decrease in proliferation in esophageal cancer cells stably transfected with p38δ MAPK. This anti-proliferative effect was exacerbated with cells transfected with p-p38δ MAPK. Using a Boyden chamber and a wound healing assay we observed a decrease in cellular migration and invasion with cells transfected with p38δ or p-p38δ MAPK. Finally using Annexin V-FITC/PI double labeled flow cytometry we observed that p38δ and p-p38δ MAPK confers a greater sensitivity of esophageal cancer to certain chemotherapeutic drugs but resistance to others. Conclusion: We now provide data for the anti-tumourigenic effect of p38δ MAPK in esophageal cancer. Our research may provide a new potential target for the treatment of esophageal cancer and metastases. Interestingly, our findings are also applicable to other cancer types namely renal, prostate and pancreatic cancer which also lack p38δ MAPK isoform expression.

Citation Format: Carol O'Callaghan, Liam Fanning, Aileen Houston, Orla P. Barry. New paradigms for the modulatory actions of p38δ MAPK restorative expression in esophageal squamous cancer cell growth, migration and response to chemotherapy: A possible future therapeutic target. [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 3993. doi:10.1158/1538-7445.AM2013-3993