Abstract 3250: LNA gapmer to gastrin inhibits growth and metastases of human pancreatic cancer in mice

Abstract Background: Pancreatic cancer has a poor prognosis and novel strategies are needed to improve the survival. Gastrin stimulates growth of pancreatic cancer by an autocrine mechanism and RNAi techniques that decrease gastrin expression have been shown to inhibit growth of this malignancy in vitro. Locked nucleic acid (LNA) Gapmers are antisense oligonucleotides (ASO) that have long half-life and stability in vivo, hence represent a potential method to deliver RNAi for cancer therapeutics. We developed an LNA Gapmer that selectively downregulates gastrin expression in pancreatic cancer cells in culture. The goal of this project was to test this anti-gastrin Gapmer in vivo as a novel therapy for pancreatic cancer. Methods: The anti-gastrin LNA Gapmer was modified using thiol-click chemistry to conjugate a peptide to the 5’ end and render the Gapmer target-specific with the ability to bind selectively to the cholecystokinin-B receptor that is over-expressed in pancreatic cancer. Forty athymic nude mice with established AsPC-1 human pancreatic orthotopic tumors were divided into four groups of equal tumor size. Mice (N=10 per group) were treated with PBS (controls), an untargeted LNA-Gapmer, the CCK-BR targeted Gapmer (60nM), and the CCK-BR targeted Gapmer (120nM) intraperitoneally twice a week for 4 weeks. Growth was monitored by luciferase IVIS imaging. At necropsy, tumors were excised, and metastases counted. Results: Mean tumor mass was 43% smaller in mice treated with the targeted Gapmer-120nM (P=0.0007). Untargeted and targeted Gapmer 60nM slightly decreased tumor mass but this difference was not significant. Compared to PBS control-treated mice, metastases were significantly less in mice treated with the untargeted Gapmer by -39% (p=0.01); in the targeted Gapmer-60nM by -44% (p=0.003), and with the targeted Gapmer-120nM by -72% (p<0.0001). Gastrin mRNA analysis of the tumors by qRT-PCR confirmed downregulation of gastrin. Conclusion: Novel LNA Gapmers that downregulate gastrin mRNA expression decrease growth and metastases of pancreatic cancer in a dose-related fashion. Citation Format: Godhanjali Chekuri, Wenqiang Chen, Narayan Shivapurkar, Hong Cao, Ruvanthi N. Kularatne, Stephan Stern, Jill P. Smith. LNA gapmer to gastrin inhibits growth and metastases of human pancreatic cancer in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3250.