Abstract 2691: Cigarette smoke induced upregulation of endothelin axis in the initiation of pancreatic cancer
Authors: Gupta Suprit , Rachagani Satyanarayana , Kumar Sushil , Batra Surinder Kumar , Jain Maneesh 
Published: July 2017

Background: Cigarette smoke is an established risk factor for pancreatic ductal adenocarcinoma (PDAC). Smoke induced inflammation accelerates the progression of PDAC in presence of constitutively active K-Ras mutation. Endothelin (ET) axis comprising of endothelin converting enzymes (ECE-1, ECE-2, and ECE-3), endothelin isoforms (ET-1, ET-2 and ET-3) and two receptors A (ETAR) and B (ETBR), is linked to pathobiology of pancreatitis and its components exhibit aberrant overexpression in PDAC. However, the expression of ET-axis in the oncogene-associated early Pancreatic Intraepithelial neoplastic (PanINs) lesions following exposure to cigarette smoke is unknown. We hypothesize that smoke induced alterations in the ET axis facilitate acinar to ductal metaplasia (ADM) in presence of oncogenic K-Ras. Thus, we characterized the impact of cigarette smoke exposure on ET axis components in the pancreas of mice harboring mutant K-Ras.

Methods: Expression of ECE-1, ET-1, ETAR and ETBR was analyzed by IHC and RT-PCR first in the murine model of preneoplastic lesions [KC model: (Pdx1-Cre, KrasG12D)). To determine the changes in ET axis after smoke exposure, wild type (WT) and KC mutant mice were exposed to cigarette smoke for 20 weeks and expression was analyzed in the pancreas. The impact of smoking on ET-axis was also studied on murine acinar and tumor cell lines derived from KC mice (UN-KC6141) and KPC (Pdx1-Cre, p53 (R172H) KrasG12D) mice (UN-KPC-961) by western blot and RT-PCR analysis.

Results: In contrast to the normal ducts, the expression of ECE-1, ET-1, ETAR and ETBR was upregulated in the early PaNIN lesions (20-30 weeks). In the advanced lesions (50 weeks), significant overexpression of all four molecules was noticeable in the tumor cells and stromal compartment. Smoke exposure resulted in significant increase in the transcripts of ET-1, ETAR and ETBR (p values = 0.04, 0.03 and 0.01 respectively) in the KC mice while the increase in WT mice was not significant. The changes in the expression were also corroborated by tissue IHC. Expression of ET axis components was predominantly seen in the islet cells in WT mice, while low immunoreactivity was observed in the acinar compartment. Smoke exposure of KC mice resulted in accelerated progression of PanIN lesions along with concomitant increase in the expression of ET axis components both in the ductal and stromal cells. In vitro exposure of cigarette smoke extract (CSE) to UN-KC6141 and UN-KPC-961 cells for 24 hours elicited a dose dependent upregulation of ECE 1 and ET-1.

Conclusions: In presence of mutated KrasG12D, smoking-mediated inflammatory insult promotes PanIN progression and tumorigenesis. The sustained increase and activation of ET axis with increasing dysplasia in the ductal compartment during this progression in KC mice and its further upregulation following smoke exposure suggests its possible role in promoting inflammation-associated pancreatic tumor progression.

Citation Format: Suprit Gupta, Satyanarayana Rachagani, Sushil Kumar, Surinder Kumar Batra, Maneesh Jain. Cigarette smoke induced upregulation of endothelin axis in the initiation of pancreatic cancer [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 2691. doi:10.1158/1538-7445.AM2017-2691