Abstract 2934: TRAIL-resistance in pancreatic cancer stem cells can be regulated through JNK pathway inhibition without impacting resident stem cell physiology
Authors: Recio Boiles Alejandro , Ilmer Matthias , Vykoukal Jody , Alt Eckhard 
Published: August 2015

Abstract
Cancer Stem Cells (CSC) are considered the drivers of drug-resistance and metastasis in patients with pancreatic ductal adenocarcinomas (PDAC). C-Jun N-terminal kinase (JNK) signaling has been shown to be of importance in cancer, glioblastoma CSC maintenance, and hepatocellular carcinoma cell growth. We aimed to sensitize resistant CSCs to the apoptotic effects of TNFa-related apoptosis-inducing ligand (TRAIL) by JNK inhibition (JNKi) through critical regulation of the TRAIL receptors in PDAC, without affecting the physiology of normal tissue-resident stem cells.
CSC-enriched tumorsphere cultures of Panc1, MiaPaca2, and L3.6pl were treated with JNKi to evaluate sphere-forming ability as well as gene expression of CSC markers Oct3/4, Nanog, Sox2, and CD44 by qRT-PCR. The regulation of apoptosis decoy and death TRAIL receptors were analyzed on low dose JNKi and TRAIL pressure. In addition, a TRAIL-resistant cell line from parental L3.6pl cells was created to investigate the effect of our established regimen. To resemble the desmoplastic environment of PDAC, human adipose tissue-derived stem cells (ASCs) were exposed to hypoxic conditions. Finally, we tested the efficacy of the combination of JNKi and TRAIL in vivo by injecting L3.6pl or MiaPaCa2 pancreatic cancer cells orthotopically into athymic nu/nu mice.
We found that JNKi, even at low concentrations, significantly reduced the number of spheres and decreased the expression of CSC markers to levels closer to those detected in parental cells. JNKi downregulates the TRAIL decoy receptor DcR1 while upregulating pro-apoptotic death receptors DR4/5 and thereby sensitizing cells with acquired TRAIL-resistance to apoptosis induction. The combination of JNKi and TRAIL significantly impacts on CSCs, but leaves ASCs - even under hypoxic stress conditions - unaffected. Treatment of orthotopic xenografts of L3.6pl, Panc1 or MiaPaCa2 with JNK (259.6 ± 72.58 mg) or TRAIL (260.6 ± 52.82 mg) alone for 4 weeks showed only modest effects compared to control (292.3 ± 66.88 mg), whereas the synergism of JNKi and TRAIL significantly reduced tumor weight (84.23 ± 25.44 mg; p &lt; 0.0174) and occurrence of metastasis.
The concept of selective treatment of pancreatic CSCs without impacting normal stem cell physiology warrants promising potential for further clinical evaluation. As an innovative approach, TRAIL-secreting ASC could increase the local concentration of TRAIL in the immediate tumor microenvironment while systemic JNKi treatment would sensitize PDAC for pro-apoptotic therapy.
Citation Format: Alejandro Recio Boiles, Matthias Ilmer, Jody Vykoukal, Eckhard Alt. TRAIL-resistance in pancreatic cancer stem cells can be regulated through JNK pathway inhibition without impacting resident stem cell physiology. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2934. doi:10.1158/1538-7445.AM2015-2934