Abstract LB_C03: Protein translation inhibition enforces histone deacetylase inhibitor activity resulting in synergistic pancreatic cancer cell death
Authors: Safari Maryam , Scotto Luigi , Basseville Agnes , Litman Thomas , Xue Haoran , Petrukhin Luba , Zhou Ping , Damoci Christopher , Zhu Minhzhao , Hull Kenneth , Olive Kenneth P , Fojo Antonio T , Romo Daniel , Bates Susan E 
Published: December 2023

Abstract
Management of pancreatic cancer presents significant challenges due to late-stage diagnosis, aggressive tumor biology, and limited efficacy of existing treatment options. Gemcitabine and FOLFIRINOX (folinic acid, 5-FU, irinotecan hydrochloride, oxaliplatin) are standard treatments for advanced pancreatic cancer. Despite these therapies the overall 5-year survival rate for pancreatic cancer patients is at 12%, largely due to drug resistance. Thus, there is a critical need to explore new therapeutic strategies. Our study explores a small molecule combination that induces epigenetic reprogramming as a potential novel therapeutic strategy for pancreatic cancer. We have identified marked sensitivity of pancreatic cancer cells to the combination of a novel inhibitor of RNA helicase eIF4A, DMPatA (MZ735), and a histone deacetylase (HDAC) inhibitor, romidepsin. A short-term, low dose romidepsin treatment, when combined with MZ735, triggers persistent global histone acetylation, transcriptional upregulation, replication inhibition, and augmented DNA damage. This combined effect induces a synergistic anti-proliferative response in pancreatic cancer cells. We have identified a tolerable protocol for this combination regimen in animals, demonstrating its efficacy against tumor growth in a MIA PaCa-2 xenograft mouse model of pancreatic cancer. Treatment with the combination resulted in inhibition and then complete suppression of tumor growth in animals for 39 days. Our in vitro studies aimed at understanding the mechanism of this combination treatment showed that at low doses of romidepsin monotherapy, histone acetylation rapidly faded, while robust acetylation persisted to 18 and 24 hours with the combination. Additionally, R-loop accumulation was observed using confocal microscopy and DRIP-qPCR, along with a reduction in replication fork speed, which might account for the identified DNA damage and genome instability. The combination treatment significantly reduces acetyl-CoA and c-MYC protein levels and disrupts glycolysis and oxidative phosphorylation. We show that a structurally different HDAC inhibitor exhibits the same synergistic effects when co-administered with MZ735, confirming a unique method of eliciting synthetic lethality in PDAC cells. In conclusion, this combination shows significant antitumor activity in both in vitro and in vivo models of pancreatic cancer and warrant translation to the clinic.
Citation Format: Maryam Safari, Luigi Scotto, Agnes Basseville, Thomas Litman, Haoran Xue, Luba Petrukhin, Ping Zhou, Christopher Damoci, Minhzhao Zhu, Kenneth Hull, Kenneth P Olive, Antonio T Fojo, Daniel Romo, Susan E Bates. Protein translation inhibition enforces histone deacetylase inhibitor activity resulting in synergistic pancreatic cancer cell death [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C03.