Abstract B004: Analysis of proteomic changes in enzalutamide-resistant prostate cancer cells and identification of potential therapeutic targets for drug repurposing
Enzalutamide is indicated for treatment of castrate-resistant prostate cancer (CRPC), but therapeutic effect is transient. The mechanisms by which prostate cancer (PCa) cells survive Enzalutamide therapy are poorly understood, but androgen receptor (AR) and non-AR mediated mechanisms have been reported. We performed unbiased high resolution proteomic analyses to identify proteins and pathways that are involved in survival and progression in Enzalutamide treatment failure and which could be potential drug targets. Enzalutamide-resistant MR49F and MR42D cell lines were maintained in standard medium (DMEM with 5% FBS) with Enzalutamide 10µM. Parental LNCaP cells were grown in standard medium. For perturbation, MR49F and MR42D cells were then changed to standard medium with either Enzalutamide 10µM (ENZA) or DMSO (control) for 7 days in. Medium was changed every 48 hours. Protein lysates from 4 biological replicates were labelled using a Tandem Mass Tag (TMT) assay and subjected to mass spectrometry (MS). Protein abundance was measured and significant differences in expression were analysed using a 2-way t-test with a permutation based false detection rate (FDR) of 0.05 and 250 randomisations in the Perseus software suite. MR49F and MR42D were compared to parental LNCaP, and MR49F and MR42D were compared on and off Enzalutamide treatment pressure. Searches were performed on Drug-Target databases for drug interactions with identified proteins to assess potential for repurposing in Enzalutamide-resistant disease. MS identified 5364 unique proteins. Of these, 247 (180 up, 67 down) were differentially expressed by at least 50% in both MR49F and MR42D cell lines relative to parental LNCaP cells. When MR49F and MR42D cell lines were grown with or without Enzalutamide pressure, 5 proteins (4 up, 1 down) were regulated by at least 50% in both cell lines. Across all experimental conditions and cell lines, 16 proteins were dysregulated (8 up, 8 down). Pathway analyses with the differentially expressed and regulated proteins identified perturbations in biological pathways. Drug-Target interaction searches identified drugs that could potentially be modified and repurposed for Enzalutamide-resistance therapy including Doxorubicin, Busulfan, Curcumin, Azathioprine, Rituximab, Vinvcristine, Etacrynic acid, Magnesium carbonate and Riboflavin. This unbiased proteomic analysis of Enzalutamide-resistant PCa cells identified proteins and pathways that may be essential for PCa cell survival and progression during Enzalutamide therapy failure. Enzalutamide therapy failure involved some non-AR mediated mechanisms which may be targeted for therapeutic benefit. Drug repurposing offers potential for faster and cost-effective means to identify new therapeutic options for enzalutamide-resistant PCa. Chidi N. Molokwu, Anders Kirstensen, Chris Sutton. Analysis of proteomic changes in enzalutamide-resistant prostate cancer cells and identification of potential therapeutic targets for drug repurposing [abstract]. In: Proceedings of AACR Drug Discovery and Development (AACR D3) Conference; 2026 Jul 21-24; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(14_Suppl):Abstract nr B004.