Repurposing Rilmenidine as a Potential Antimetastatic Therapy Targeting Nischarin in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancer types with a dismal prognosis, where early metastatic dissemination and rich desmoplastic stroma limit the therapeutic efficacy. Nischarin (NISCH)/Imidazoline-1 receptor (IR-1) is a potential tumor suppressor that is involved in the regulation of cell migration, invasion, and cytoskeletal organization. Importantly, several clinically approved agonists have been shown to target this receptor. This study aimed to examine NISCH expression in PDAC and the effects of its agonists with the intent of drug repurposing. NISCH was expressed in PDAC tumor tissue, in both the epithelial and stromal compartments of tumors, and higher NISCH expression was associated with longer patient survival. Out of the three tested NISCH agonists, moxonidine, clonidine and rilmenidine, rilmenidine was the only one affecting cancer cell viability and at high doses induced cancer cell apoptosis. Transcriptome analysis of rilmenidine-treated PDAC cells revealed changes associated with cytoskeletal organization, translating into decreased adhesion and migration in vitro. In cancer-associated fibroblasts (CAFs), rilmenidine treatment decreased the expression of activation markers and limited cancer cell-CAF cytokine communication in the co-culture. Ultimately, in the in vivo tumor xenograft zebrafish model, rilmenidine reduced the metastatic spread of pancreatic cancer cells. Our results suggest that the NISCH agonist rilmenidine is a promising candidate for drug repurposing as an antimetastatic agent in PDAC, and that NISCH can be a potential target for the development of new PDAC therapeutics.