Virtual Screening Approach to Repurpose FDA‐approved Drugs for Targeting Acid Ceramidase‐1 in Pancreatic Cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer‐related deaths in the US. Despite extensive research and advances in molecular pathogenesis, PDAC remains a major problem in the US. It is also projected to be the second leading cause of cancer‐related deaths in the US by 2030. PDAC is an aggressive disease and characterized by poor prognosis, rapid progression, drug resistance and recurrence. The current chemotherapy treatment only improved survival to <10%, hence there is a need to identify a novel target for drug discovery.Recently, altered sphingolipid metabolism was identified in PDAC patients. Sphingolipids are critical constituents of the cell membrane that regulate several signaling pathways related to cell survival. The major sphingolipid metabolites are ceramide and sphingosine which are interconvertible, while ceramide is pro‐apoptotic and sphingosine is anti‐apoptotic. Ceramidases are a heterogeneous enzyme family that convert ceramides into sphingosine and fatty acids. The five human ceramidases are identified are the acid ceramidase (ASAH1); neutral ceramidase (ASAH2); alkaline ceramidase 1 (ACER1); alkaline ceramidase 2 (ACER2); and alkaline ceramidase 3 (ACER3). To understand the role of ceramides in PDAC, we first interrogated the cancer genome atlas database and found that all ceramides are expressed in lower levels in PDAC except ASAH1 which is uniquely overexpressed in PDAC patients compared to normal individuals. Further, immunocytochemistry of PDAC patient tissue microarray showed higher expression of ASAH1 in PDAC tumors compared to normal pancreas. Western blot analysis also showed overexpression of ASAH1 protein in PDAC cell lines. Studies indicate that ASAH1 plays an important role in PDAC progression. Our data indicate that ASAH1 is a potential target for the treatment of PDAC. For faster translation of this target to the clinic, we used virtual screening and molecular docking approach to identify FDA‐approved drugs for targeting ASAH1. We have downloaded the 3D‐protein structure of ASAH1 from the protein data bank and currently screening a library of small molecular drugs against ASAH1 protein using multiple software programs such as Autodock vina and PyRx. We will select the top 10 drug candidates from virtual screening based on their binding energies and the ability to form hydrogen bonds with key amino acids. We will confirm these findings using a cellular thermal shift assay to analyze the binding of these drugs to ASAH1 in PDAC cell lines and test their anticancer activities in cell culture system and orthotopic PDAC mouse model.