Abstract A62: ATDC is required for KRAS-induced pancreatic tumorigenesis

Abstract

Abstract We have recently demonstrated that ATDC, a novel oncogenic protein, serves as an invasive switch in pancreatic cancer (PDA) by activation of beta–catenin signaling and upregulation of CD44, resulting in EMT and an invasive phenotype during PanIN progression. To further explore the tumorigenic function of ATDC, we generated a floxed ATDC mouse (A F/F) to evaluate the impact of conditional knockout of ATDC on oncogenic Kras-induced PDA initiation and progression. Pancreas-specific ATDC knockout did not cause any histologic abnormalities in pancreas, up to 1 year of age (n=8). Through a series of crosses of LSL-KrasG12D (K), p53F/+ (P), RosaYFP (Y), Pdx1-Cre (C) and AF/F mice, KrasG12D; CY (KCY); KrasG12D; p53+/-; CY (KPCY), KCYA-/- KPCYA-/- mice were generated. Knockout of ATDC in KPCY mice completely prevented the development of ADM and PanIN lesions in 3 month old mice (n= 8), and resulted in the formation of very rare ADM and PanIN1 lesions (2 out of 8) in KPCYA-/- mice at 12 months of age (n=8). In contrast, all KPCY mice developed extensive PanIN (low and high grade) at 3 months of age (n= 8), with the subsequent development of invasive and metastatic cancer at frequencies similar to that reported in the literature. To determine the possible mechanisms by which ATDC inhibited KrasG12D-induced acinar-ductal metaplasia (ADM), we isolated acini from 1.5 month old KCY and KCYA-/- pancreata and performed in vitro 3D cultures and ADM assays. ADM lesions readily formed in 3-D cultures of acini from KCY mice at 5 days, and this was significantly inhibited in acini isolated from KCYA-/- mice (duct-like structures: 95.1±3.5% to 28.0±2.2%*, KCY vs KCYA-/-, n=3, *p<0.05). Expression of ATDC specific shRNA in acini from KCY mice also effectively decreased ADM formation in 3D culture, an effect that was completely reversed by ATDC overexpression using an ATDC-shRNA-resistant expression vector. To further evaluate the role of ATDC in ADM and PanIN formation, we induced caerulein-mediated acute pancreatitis in 1.5 month old WT, CYA-/-, KCY, KCYA-/- mice and analyzed pancreatic tissue 1 and 7 days following cerulein treatment. 1 day post-caerulein treatment, KCY, KCYA-/-, CYA-/- and WT mice exhibited widespread ADM, which was replaced by normal acini by 7 days in WT, CYA-/- and KCYA-/- mice. However, in KCY mice 7 days post-cerulein treatment, extensive ADM and PanIN lesions were present, suggesting that ATDC is required for oncogenic KRAS to promote ADM and PanIN formation. Conclusions: Knockout of ATDC markedly reduces KrasG12D-induced ADM and PanIN formation, highlighting a key biologic function for ATDC in this process and its role in driving progression of KRAS-induced tumorigenesis in the pancreas. Citation Format: Lidong Wang, Huibin Yang, Ethan V. Abel, Phillip L. Palmbos, Christophe Halbrook, Kenneth Takeuchi, Jiaqi Shi, Yaqing Zhang, Sumithra Urs, Meghna Waghray, Marina Pasca di Magliano, Andrew D. Rhim, Howard C. Crawford, Diane M. Simeone.{Authors}. ATDC is required for KRAS-induced pancreatic tumorigenesis. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A62.