Abstract C118: A Non-Canonical role of cGMP Links PDE5A Inhibition to Metastasis Suppression

Abstract Background: Cholesterol metabolism is integral to cancer progression, particularly in supporting the energy-intensive processes of tumor cell migration and metastasis. Although metastatic cells often exhibit increased cholesterol synthesis, disruptions in cholesterol trafficking can limit their migration and metastatic capability. PDE5A, a cyclic GMP phosphodiesterase, is critical in regulating cGMP levels, influencing various cellular processes. We hypothesized that sildenafil citrate (Viagra), a well-known PDE5A inhibitor, could impact cancer progression by reducing GMP and altering nucleotide pools. We discovered that sildenafil's primary effect on tumors is the disruption of cholesterol trafficking, therefore impairing metastatic progression. Sildenafil’s established clinical use highlights its potential as a therapeutic to target cholesterol metabolism and metastasis. Methods: We used RNA-seq, proteomics, and lipidomics to define sildenafil’s molecular effects across multiple cancer models. Cell proliferation and migration were assessed via live imaging. Genetic knockdown of PDE5A confirmed specificity. Lysosomal cholesterol trafficking was evaluated through immunofluorescence. Binding assays were performed to confirm direct cGMP interaction with the NPC1 transporter. In vivo metastasis was quantified in murine models. Clinical relevance was supported by retrospective analysis of cancer patients treated with PDE5A inhibitors and statins. Results: Sildenafil treatment elevated intracellular cGMP and impaired cholesterol binding to the lysosomal transporter NPC1, leading to lysosomal cholesterol accumulation and reduced mitochondrial ATP production. This triggered compensatory cholesterol gene expression and disrupted membrane lipid raft organization. Importantly, the effect was specific to tumor cells, with minimal impact on untransformed cells, underscoring a cancer-selective vulnerability. These alterations significantly reduced cell proliferation and migration in vitro. In vivo, sildenafil lowered metastatic burden, with enhanced efficacy when combined with statins. Retrospective analysis of patient medical records revealed improved survival with PDE5A inhibitor treatment, with additive benefits observed when combined with statin therapy. Conclusion: This study uncovers a novel anti-metastatic mechanism of sildenafil, showing that PDE5A inhibition disrupts cholesterol trafficking specifically in tumor cells via direct cGMP-mediated inhibition of NPC1, a previously undescribed interaction with major translational implications. By targeting a cancer-specific metabolic weakness with a well-characterized drug, our findings support repurposing sildenafil as a clinically accessible strategy to inhibit metastasis. Citation Format: Yarden Ariav, Samah Hayek, Naama Darzi, Lipika Ray, Efrat Ben-zeev, Sergey Malitsky, Inna Goliand, Eytan Ruppin, Ayelet erez. A Non-Canonical role of cGMP Links PDE5A Inhibition to Metastasis Suppression [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr C118.