Abstract B044: Exploring cannabidiol’s anticancer effect and uptake in prostate cancer: bridging <i>in vitro</i> and <i>ex vivo</i> models

Abstract Prostate cancer (PCa) is the 2nd most common cancer in men worldwide, excluding non-melanoma skin cancers. Whilst androgen deprivation therapy initially proves effective, the inevitable development of castration-resistance renders the disease incurable. Therefore, novel therapeutic approaches are urgently needed to improve treatment options and outcomes for patients with aggressive PCa. Our lab has previously shown that cannabidiol (CBD), a major non-psychoactive cannabinoid, reduces PCa cell viability and alters expression of key cell cycle proteins in in vitro cell line models and induced apoptosis in non-cancerous PCa cells. However, a knowledge gap surrounds the mechanism of entry of CBD into PCa cells. The aim of this study was to bring CBD forward into physiologically relevant 3D ex vivo PCa tissue models as well as explore how CBD is getting into PCa cells. Surgical biopsies were obtained from patients undergoing radical prostatectomy. Tumour cores were precision-cut to generate 200µm-thick tissue slice cultures (TSCs), incubated for 24hr, &amp; treated with CBD for 72hr. LNCaP was chosen as the cell line model to base the ex vivo experiments on. Using the MTT assay, CBD reduced LNCaP viability after 72hr treatment with an IC50 value of 13.31µM. Expression of the canonical (CNR1, CNR2, GPR55, TRPV1, &amp; TRPV2) and non-canonical receptor genes (GPR18, GPR19, TRPA1, TRPM8, PPARG, &amp; FAAH) was examined by RT-qPCR in a panel of PCa cell lines (DU145, PC-3, LNCaP, LNCaP Abl, 22Rv-1, &amp; C4) and the non-cancerous line (PWR1E). Early results show that 72hrs of CBD (2x the LNCaP IC50 value (26.62 µM)) exposure induces caspase 3 cleavage by 35% (P&amp;lt;0.001, consistent with our previous findings in PCa cell lines. In terms of receptor expression, CNR1, CNR2, GPR55, &amp; GPR18 were not expressed in any cell lines. TRPV1 &amp; TRPV2 were expressed across all cell lines at low-to-medium levels. TRPM8 was expressed exclusively in androgen receptor (AR)-positive PCa cell lines (LNCaP, 22Rv-1, C4, and LNCaP Abl). TRPA1 was exclusively expressed in the non-cancerous cell line. GPR19 and FAAH were expressed to varying extents across all cell lines. PPARG was widely expressed, with AR-negative cell lines (DU145 &amp; PC-3) having the highest expression. This is the first comprehensive analysis of gene expression of both canonical and non-canonical cannabinoid receptors, ion channels, nuclear receptors, and enzymes in a wide variety of PCa cell line models, encompassing androgen receptor (AR)-positive, AR-negative, castration resistant, hormone sensitive, &amp; non-cancerous cell lines. Future work will verify receptor expression in the PCa TSCs by PCR and immunohistochemistry. In addition, siRNA knock-down of selected receptors is ongoing to examine the influence on CBD’s effect on viability. In addition, ex vivo culture of CBD with PCa TSCs will be expanded to incorporate standard of care therapies This study provides a stepping stone to bridge the gap between in vitro&amp; in vivo studies, producing more translational results. Citation Format: Rianna Magee, Joanne Cosgrave, Emma Lishman-Walker, Kelly Coffey, Craig Robson, David Galvin, Maria Prencipe, Antoinette Perry. Exploring cannabidiol’s anticancer effect and uptake in prostate cancer: bridging in vitro and ex vivo models [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr B044.