Characterising the effect of circulating sphingolipids on metastatic prostate cancer cells.

BACKGROUND: Prostate cancer (PC) is a leading cause of cancer-related deaths in men, with advanced cases exhibiting resistance to androgen deprivation therapy. Dysregulated lipid metabolism has emerged as a hallmark of aggressive PC. This study investigates the biological underpinnings of a circulating three-lipid signature (3LS) previously validated as a prognostic biomarker in patients with metastatic castration-resistant prostate cancer (mCRPC). METHODS: Using plasma samples from 16 mCRPC patients (8 positive and 8 negative for the 3LS), we assessed the impact of 3LS-positive plasma on three prostate cancer cell lines representative of disease progression. We investigated changes in cell viability and intracellular lipid metabolism associated with plasma from the two patient cohorts. FINDINGS: Exposure to 3LS-positive plasma improved cell viability across AR-positive (LNCaP, C4-2B) and AR-negative (PC3) cell lines compared to exposure to 3LS-negative plasma. Lipidomic profiling revealed elevated sphingolipids and glycosphingolipids in 3LS-positive plasma-treated cells, accompanied by metabolic shifts characterised by increased monounsaturated and reduced polyunsaturated fatty acid levels. Inhibition of sphingosine kinase 1 abrogated the 3LS-positive plasma-treatment phenotype consistent with ceramide/sphingosine 1 phosphate (S1P) signalling being the mechanism of action. INTERPRETATION: These findings suggest that the circulating 3LS is not just a prognostic biomarker, but an actionable signature reflecting changes in PC biology. The plasma lipid milieu identified by the 3LS drives a pro-survival phenotype by modifying lipid metabolism and upregulating ceramide/S1P signalling. The study provides the biological rationale to target ceramide-S1P signalling in patients, who are 3LS-positive. FUNDING: National Health and Medical Research Council of Australia Investigator grants (1196225; 2009965; 1197190); Cancer Institute New South Wales Translational Program Grant (TPG172146); Victorian Government Operational Infrastructure Support Program; Australian Government Research Training Program; University of Sydney merit award.