Abstract C052: Proteomics analysis of enzalutamide-treated castration-sensitive and castration-resistant prostate cancer cell lines

Abstract INTRODUCTION: Androgen deprivation therapy (ADT) is the standard treatment for metastatic prostate cancer, a disease that disproportionately affects African Americans. However, tumors often progress to metastatic castration-resistant prostate cancer (mCRPC). Enzalutamide (ENZ) and other treatments initially work well for mCRPC, but their effectiveness decreases due to the evolution of tumor resistance. OBJECTIVE: Our study investigates how ENZ alters biological pathways in castration-sensitive (CS) and castration-resistant (CR) cell lines. We aim to compare whole-proteome expression profiles of two metastatic prostate cancer cell lines, LNCaP (CS) and C4-2B (CR), following ENZ exposure. METHODS: Both cell lines were treated with dihydrotestosterone alone (DHT group), ENZ alone (ENZ group), or a combination of DHT + ENZ. All cell lines were grown in Charcoal-stripped serum for 24 hours prior to ENZ and DHT exposure to remove trace androgens in the growth media. Proteins were analyzed using LC-MS/MS (Liquid Chromatography multi-stage mass spectrometry) shotgun proteomics. PEAKS Studio software (version 11) was used for proteomics-based expression analysis against the UniProt human reference proteome database (UP000005640). The differentially expressed protein lists were mapped to corresponding biological pathways in KEGG and REACTOME databases for enrichment analysis using the WEBGESTALT web-app. RESULTS: In total, 2,344 proteins were identified with high ID stringency (Q-value 20) in the C4-2B cell line. Using Label-Free Quantitation, we observed 32 Differentially Expressed Proteins (DEPs) in the ENZ group, 7 DEPs in the DHT group, and 82 DEPs in the combined DHT + ENZ group. DEPs were mapped to biological pathways in KEGG and REACTOME databases for enrichment analysis using the WEBGESTALT web-app. Notable pathways with significant enrichment score values included “mRNA degradation (KEGG Hsa03018)”, “Rho-GTPase-based activation (REACTOME #R-HSA-5625900; #R-HSA-5627117)", and “Interleukin-12 (IL-12) (REACTOME #R-HSA-9020591)” pathways. CONCLUSION: The “mRNA degradation pathway” was significantly enriched in the ENZ group. This suggests direct effects on protein expression regulation, potentially leading to adaptive protein synthesis that supports resistance. The “Rho-GTPase” and “IL-12" pathways were significantly enriched in the DHT + ENZ group, suggesting potential complex changes in cell signaling and immune interactions that may promote resistance by altering the tumor microenvironment and enabling cancer cells to adapt or evade the immune system. NEXT STEPS: Ongoing analysis of LNCaP (CS) proteomics data aims to reveal significant protein expression changes and affected cellular pathways following ENZ exposure. The goal is to identify proteome-wide cellular pathway alterations in elucidating castration-sensitive and -resistant prostate cancer subtypes. Citation Format: Lincoln E. Liburd II, Victor Paromov, Siddharth Pratap, LaMonica Stewart. Proteomics analysis of enzalutamide-treated castration-sensitive and castration-resistant prostate cancer cell lines abstract. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C052.