RF19 | PSUN383 Potential Role of Activin A During Pancreatic Acinar-to-Ductal Metaplasia of Orthotopic Pancreatic Tumor Mice

Abstract

Pancreatic ductal adenocarcinoma (PDAC) comprises more than 90% of pancreatic cancer cases and commonly harbors mutations in KRAS and TP53. PDAC is the third leading cause of cancer-related deaths in the US with approximately 10% 5-year relative survival rate. The poor survival rate largely pertains to aggressive growth following metastasis and limited understanding of prognostic factors. Accumulated evidence indicates that PDAC survival rates are inversely correlated with the pancreatic gene expression of INHBA, which encodes inhibin βA, and circulating levels of activin A (a dimer of inhibin βA), which is overexpressed in pancreatic cancer cells. However, potential mechanisms supporting the correlations have remained unclear. PDAC is etiologically related to sustained metaplasia of acinar cells to ductal-like cells (ADM). Therefore, in this study, we tested the hypothesis that activin A plays a tumor-promoting role via ADM. We implanted mouse PDAC KPC (KrasG12D and Tp53R172H) cells into the pancreata of C57BL/6 male mice and divided them into four groups; sham and three groups of orthotopic mice intraperitoneally (IP) injected with either no (TO), scramble (sc) or inhba siRNA (inhba) packaged with CPX nanoparticles, which previously exhibited tumor-targeted delivery, starting on postoperative day 4. On day 16, blood and tissues were harvested for analyses of tumor-related prognostic blood markers and tumor histology. Implanted KPC cells significantly elevated serum activin A levels and induced tumors as demonstrated by the accumulation of SOX9-positive ADM and a-SMA-positive fibroblasts when compared to sham group. Also, metastases occurred to the liver, spleen, kidney, and intestine. No differences were observed between TO and sc groups. However, when compared to sc group, inhba group had significantly suppressed serum activin A levels and reduced tumor size. Statistically, inhba group had fewer metastases and longer survival rates. Histologically, inhba group exhibited more amylase-positive acini conserved and less accumulation of a-SMA-positive cells in the pancreas. Further, the expression of activin A receptor type 2B (ACVR2B) was greatly induced on the acinar cells undergoing ADM transition in sc group, whereas such expression was subdued in inhba group. Collectively, our data indicate that inhba suppression impedes ADM mediated by KPC cells in mice and suggests activin A as one of tumor-initiating factors. It warrants further investigations in human PDAC models and clinical settings to test the potential therapeutic roles of targeting tumor INHBA in early PDAC development.

Presentation: Sunday, June 12, 2022 12:30 p.m. - 12:35 p.m., Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.