Abstract 1059: Combination of gemcitabine and cytidine deaminase inhibitor: A breakthrough cocktail for the treatment of pancreatic ductal adenocarcinoma

Abstract

Abstract Pancreatic ductal adenocarcinoma is a very common type of pancreatic cancer and is one of the deadliest cancers. Gemcitabine (Gem), is still the mainstay drug for the treatment of PDAC. Gem is a hydrophilic drug which requires nucleoside transporters for its efficient uptake. Once inside the cell, Gem is converted to an active triphosphate form which inhibits DNA synthesis and causes apoptosis. However, Gem gets inactivated by cytidine deaminase (CDA). Long term treatment with Gem leads to increased CDA production thereby developing resistance. We hypothesize that combination of Gem with CDA inhibitor like Zebularine (Zeb), could prevent the intracellular degradation of Gem. Combination can potentially result in enhancing the anti-cancer activity of Gem, reduced dose and dosing frequency and minimizing side effects. The objectives of our study were; (a) to investigate the cytotoxic interaction of Gem and Zeb alone and in combination (b) Evaluating effect of various apoptosis and proliferation markers using flow cytometry and western blot assay. Initially we explored the anti-proliferative effects of Gem and Zeb as a single drug and in combination on MiaPaca-2 cells using MTT assay. Combination index was calculated using chou talalay method and Combenefit software. Effect of Gem, Zeb, and combination treatment on the cell viability of 3D tumor spheroids and its area was carried out using fluorescence microscopy and ImageJ software respectively. Apoptosis study was carried out using Annexin V apoptosis kit.Gem and Zeb exhibited dose-dependent inhibition in viability of MiaPaca-2 cells with an IC50 of 0.48 and 67.82 µM, respectively. The combination index of 0.09 suggest “very strong synergism” (Table 1). 3D spheroid treated with combination exhibited a highly distorted surface with significantly higher number of dead cells. Our research confirms that this synergistic combination can be a breakthrough approach for the treatment of PDAC. Table 1.IC50 of Gem, Zeb and combination of Gem+Zeb in Miapaca2 cellsDrugMolar RatioIC50 of GemIC50 of ZebCombination IndexSingle-0.4867.82Gem1:100.0440.40.09 Citation Format: Manali Patki, Aishwarya Saraswat, Shraddha Bhutkar, Vikas Dukhande, Ketankumar Patel. Combination of gemcitabine and cytidine deaminase inhibitor: A breakthrough cocktail for the treatment of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1059.