Abstract 2504: Antiarrhythmic drugs repositioning to counteract the activated phenotype of prostate cancer-associated fibroblasts
Authors: Doldi Valentina , Tortoreto Monica , Percio Stefano , Gandellini Paolo , Zaffaroni Nadia 
Published: April 2023

Abstract
The interplay between cancer cells and adjacent stroma is fundamental to sustain carcinogenesis and promote the acquisition of additional malignant features. Cancer-associated fibroblasts (CAFs) have been shown to fuel prostate cancer (PCa) development and metastasis by mutually interacting with tumor cells. Comparative gene expression profile analysis of CAFs and normal fibroblasts, showed that CAFs are characterized by a positive enrichment of gene sets that regulate cytoskeleton remodeling and muscle contractility, including genes coding for calcium, potassium and sodium channels. Here, for the first time, we investigated the effects of cation channel inhibitors, currently used as antiarrhythmic drugs, on CAF-activated state and CAF-PCa cell interplay. Our results showed that antiarrhythmic drugs are able to interfere with crucial features of reactive prostate CAFs, as indicated by changes in cell morphology and modulation of specific fibroblast activation markers, such as α-SMA, fibroblast activation protein and collagen type I. In addition, although to a variable extent, antiarrhythmics reduced CAF motility and hindered CAF capability to remodel extracellular matrix, as assessed by 3D gel contraction and scratch assays. Interestingly, conditioned medium and co-culture experiments reveled that CAFs were able to promote cell growth and induce epithelial to mesenchymal transition (EMT) in PCa cells, as indicated by E-cadherin and β-catenin down-regulation and Snail and Vimentin up-regulation. Interestingly, antiarrhythmics partially reverted CAF-mediated protumoral effects, abrogating their ability to foster PCa cell proliferation and plasticity. Moreover, based on previous evidence indicating the involvement of matrix metalloproteinase (MMP) in CAF-induced EMT on PCa cells, we found that antiarrhythmics impaired the secretory phenotype of CAFs, as indicated by the reduction of MMP-2 releasing in the medium. Finally, gene expression analysis highlighted that antiarrhythmic-treated CAFs showed a gene expression pattern resembling that of normal fibroblasts. Consistent with our in vitro findings, in vivo experiments confirmed that intra-tumoral administration of medium form antiarrhythmic-treated CAF reduced tumor growth rate of PCa xenografts compared to medium form untreated CAFs. Overall, cation channels inhibition interferes with crucial features of prostate CAFs, affecting their activated state. Moreover, co-culture experiments indicate that antiarrhythmics are able to impair CAF-induced proliferative spur and EMT in PCa cells, and also induce tumor growth delay in vivo. Collectively, such data suggest new opportunities for the therapeutic repositioning of antiarrhythmic drugs with the aim of targeting CAFs and hence interrupting their supportive boost in PCa.
Citation Format: Valentina Doldi, Monica Tortoreto, Stefano Percio, Paolo Gandellini, Nadia Zaffaroni. Antiarrhythmic drugs repositioning to counteract the activated phenotype of prostate cancer-associated fibroblasts [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 2504.