Abstract 2672: Combination of hydroxychloroquine, paricalcitol and gemcitabine modulate autophagy and anti-tumor responses in pancreatic ductal adenocarcinoma
Authors: Ganji Purnachandra Nagaraju , Saddala Madhu Sudhana , Putty-Reddy Sudhir , Foote Jeremy B. , Masood Ashiq , El-Rayes Bassel F. 
Published: June 2023

Background/Objective: Pancreatic ductal adenocarcinoma (PDAC) has low (~10%) five-year survival with standard of care chemotherapy regimens proving modest impact in median survival in part due to the abundant ECM. ECM acts a barrier to chemotherapeutic drug diffusion and the ability of tumor cells to catabolize (via autophagic pathways) host cell organelles to survive the hypoxic tumor microenvironment. Therefore, we hypothesized that the combined use of hydroxychloroquine (H), which affects autophagy, and paricalcitol (P), which inhibits cancer associated fibroblast development and ECM production, will act synergistically impacting both autophagy associated protein profiles, and anti-tumor activity of chemotherapy through increased drug penetrance of gemcitabine (G).

Methods: Female C57BL/6J mice (n=6/group) were implanted with 2×105 mouse derived PDAC cells into the pancreas and then randomized (day 5), into 1) vehicle (PBS), 2) G 3) P plus H, and 4) G, P, and H treatment groups. G and P (twice weekly) were administered via intraperitoneal injection. H was given orally (daily for 14 days). Tumors were analyzed via bioluminescent imaging to monitor growth and after 15 days proteomics analysis by using TMT 16-plex labelling were performed to monitor the impact of these therapies on the proteome and cellular pathways. Autophagy was determined using transmission electron microscopy and western blot analysis of autophagy-associated proteins.

Results: Combination of G, P, and H significantly (p&lt;0.001) reduced tumor growth/weight versus controls in orthotropic PDAC mouse model. Proteomic profiles identified 10550 proteins from control and treated groups showed 12 autophagy-associated proteins were upregulated and 2 autophagy associated proteins were downregulated in GPH treated PDAC mice as compared with PBS (Control) or G or PH treated PDAC mice respectively. This molecular evidence was confirmed by electron microscopy results and western blot analysis.

Conclusion: The combination of GPH creates higher cytotoxicity (decreased proliferation, clonogenicity and increased autophagy positive cells; p&lt;0.001) in PDAC cell lines and tumor regression in vivo. Collectively, this investigation offers mechanistic insight into the cytotoxicity initiated by GPH and suggests further evaluation of its utility for PDAC therapy is warranted.

Citation Format: Purnachandra Nagaraju Ganji, Madhu Sudhana Saddala, Sudhir Putty-Reddy, Jeremy B. Foote, Ashiq Masood, Bassel F. El-Rayes. Combination of hydroxychloroquine, paricalcitol and gemcitabine modulate autophagy and anti-tumor responses in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2672.