Abstract 3356: Inhibiting phospholipase D1 reduces pancreatic carcinogenesis in mice
Authors: Addassi Hala Amer , Matsukuma Karen , Mackenzie Gerardo G. 
Published: March 2024

New therapeutic targets are needed for pancreatic ductal adenocarcinoma (PDAC), a leading cause of cancer-related death worldwide. Phospholipase D (PLD) is a lipid-signaling enzyme that appears to play a critical role in cell proliferation, survival/apoptosis, and downstream oncogenic transformation. Elevated PLD1 or PLD2 (the two classical mammalian isoforms) activity has been shown to promote tumor progression in various cancer types, however, the role and mechanisms of PLD in pancreatic cancer are not yet understood. Thus, the objective is to determine the role of PLD1 regulation in pancreatic carcinogenesis through genetic and pharmacological inhibition. To evaluate the role of PLD1 in tumor growth, we subcutaneously transplanted human MIA PaCa-2 pancreatic cancer cells expressing endogenous PLD1 levels (Ctr KD cells), or MIA PaCa-2 cells in which PLD1 was knocked down (Pld1 KD cells), into immunodeficient nude mice. After 18 days post implantation, tumors that arose from Pld1-KD cells presented a significantly smaller tumor size (p&lt;0.05) and had reduced levels of Bcl-xL and Bcl-2, compared to controls (Ctr KD). Then, to assess the role of PLD1 in the tumor microenvironment, we implanted KPC pancreatic cancer cells into C57BL/6 wild-type (WT) or C57BL/6 PLD1 knockout (Pld1−/−) mice with and without treatment with gemcitabine. Fourteen days after tumor implantation, the growth of KPC tumors was attenuated in Pld1−/− mice by 49% (p&lt;0.05). Treatment with gemcitabine reduced tumor growth by 51.6% (p&lt;0.05) in WT mice and by 79.5% (p&lt;0.03) in Pld1−/− mice. Moreover, we evaluated the effects of PLD1 genetic ablation by crossing LSL-KrasG12D/+; Ptf1Cre/+ (KC) mice into PLD1 knockout (Pld1−/−) mice to generate KC; Pld1−/− mice. At 8 months of age, KC; Pld1−/− mice had significantly smaller pancreases (p&lt;0.05) compared to KC mice. Interestingly, PLD1 ablation increased phosphorylation of ERK and c-Jun in KC; Pld1−/− mice compared to KC mice. Finally, to assess whether pharmacological inhibition of PLD can inhibit pancreatic carcinogenesis, KC mice received daily intraperitoneal injections of a small molecule inhibitor of PLD1 and PLD2 (FIPI) at a dosage of 3 mg/kg of body weight for a duration of 5 weeks. Treatment with FIPI reduced acinar-to-ductal metaplasia (p&lt;0.05) and reduced cell proliferation (p&lt;0.01), when compared to vehicle-treated KC controls. Additionally, FIPI treatment was safe demonstrating no significant differences in body weight between the groups and no significant alteration in the serum levels of liver enzymes, including aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase. In conclusion, these findings reveal PLD1 plays a critical role in pancreatic carcinogenesis and might represent a novel therapeutic target.

Citation Format: Hala Amer Addassi, Karen Matsukuma, Gerardo G. Mackenzie. Inhibiting phospholipase D1 reduces pancreatic carcinogenesis 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 3356.