Abstract 1470: Inhibition of protein myristoylation sensitizes pancreatic cancer cells to DNA damage agents

Abstract Pancreatic ductal adenocarcinoma (PDAC) has one of the highest cancer mortality rates with a 5-year survival rate of only 12% despite tumor removal and/or chemo-radiotherapy. The poor prognosis is partly due to therapy resistance driven by genes and pathways regulating cell signaling, proliferation, and metastasis. DNA damage response (DDR) pathways contribute to this resistance by enabling cancer cells to repair treatment-induced DNA damage, evade apoptosis, and adapt through alternative repair mechanisms, emphasizing the need for new therapeutic targets. We explored the role of protein myristoylation, which is the addition of a 14-carbon myristic acid to lysine and glycine catalyzed by N-myristoyl transferase (NMT) 1 and 2, in DDR regulation as potential therapeutic targets for PDAC. Analysis of The Cancer Genome Atlas (TCGA) database revealed correlation of lower levels of NMT1 and NMT2 with higher microsatellite instability score, a marker of genomic instability. Inhibition or knockdown of NMT1 and NMT2 in PDAC cells increased γH2AX levels, a marker for genomic instability, suggesting that NMTs may have a role in maintaining cellular genomic stability and regulating the DDR. TCGA and TARGET pan-cancer database analyses showed correlation between lower NMT1/2 expression with better cancer patient outcomes, including overall survival, progression-free survival, and disease-free progression. Gene expression analysis from the TNMplot database revealed elevated NMT1/2 levels in PDAC tumor tissues compared to nontumorigenic tissue. We then confirmed an increased level of NMT1 and NMT2 in PDAC cell lines, including MIA PaCa-2, PANC1, and HPAC, compared to nontumorigenic HPDE pancreatic ductal epithelial cells. Notably, NMT1/2 knockdown with siRNA significantly sensitized MIA PaCa-2 cells to DNA-damaging agents, including ionizing radiation (IR), topoisomerase inhibitor camptothecin (CPT), and poly (ADP-ribose) polymerase (PARP) inhibitor veliparib. Chemical inhibition of NMTs also sensitized MIA PaCa-2 cells to CPT and veliparib. These results suggest that NMTs could govern resistance of PDAC cells to DNA-damaging treatments by regulating DDR and genome stability. To further explore NMTs’ role in DDR, we performed affinity purification coupled with quantitative proteomics in HEK293T cells expressing EGFP-tagged NMT1 or NMT2. This approach identified 641 and 678 proteins, respectively, including 32 NMT1-associated proteins and 33 NMT2-associated proteins related to DNA repair. Additionally, global profiling of protein myristoylation using mass spectrometry revealed 576 myristoylated proteins in HCT116 cells, including 14 DNA repair proteins. Thus, NMT-mediated myristoylation may modulate the dynamic and functions of DNA repair proteins, thereby enhancing PDAC cell survival under therapeutic stress. Citation Format: Jiaxuan Hu, Nho C. Luong, Xin Xu, John Kim, Jinmeng G. Jiang, Roshika Roshika, Priya Kapoor-Vazirani, Sandip K. Rath, Ramona Haji-Seyed-Javadi, Ronghu Wu, David S. Yu. Inhibition of protein myristoylation sensitizes pancreatic cancer cells to DNA damage agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1470.