Abstract 6413: Exploring the role of DNMT1 in cell invasion and motility in docetaxel-resistant prostate cancer

Metastatic castration-resistant prostate cancer (mCRPC) is associated with poor prognosis and high mortality rates, primarily attributed to development of androgen resistance. Resistance to standard chemotherapies (i.e. docetaxel) occurs in nearly 50% of patients, further complicating treatment. DNA methylation contributes to both androgen and chemotherapy resistance through gene silencing. The objective of this study is to determine whether inducing global DNA hypomethylation through inhibition of DNMT1 can serve as a mechanism for reduction of cell invasion and motility in docetaxel-resistant (DR) prostate cancer (PCa). Parental and DR PCa cell lines (22Rv1, PC3, and DU145) were treated with 5-Azacytidine (5-AZA), a DNMT1 inhibitor (0.5-16μM) for 72 hrs. The clinical path of PCa from androgen-independent non-metastatic (22Rv1) to androgen receptor (AR)-negative metastatic PCa (PC3 and DU145) can be modelled using these cell lines. Cell viability was measured using the MTT assay. Protein expression changes in markers related to PCa (AR, ARv7), DR (MDR1), and DNA methylation regulation (GSTP1, DNMT1) were evaluated through Western Blot. Cell invasion and migration capacities were evaluated using the Cell Invasion kit and the Wound Healing assay. DNMT1 inhibition reduced cell viability in a dose-dependent manner across all PCa cell lines, except for DU145-DR cells. Reduction in cell viability by 42.5% and 70% was observed in DU145 cells when compared to DU145-DR cells at 8 and 16 μM 5-AZA, respectively (p<0.05). Successful DNMT1 inhibition was achieved in all PCa cell models in a dose-dependent manner. Re-expression of GSTP1, as a marker of successful DNA hypomethylation, was achieved in DU-145-DR, PC3 and PC3-DR cells. No differences in protein expression were observed for the PCa (AR, ARv7) or DR (MDR1) markers upon 5-AZA treatment. DNMT1 inhibition increased the invasion capacity in parental DU145 cells by 40% and 68% at 1 and 2 μM. In DU145-DR cells, 5-AZA increased cell invasion by almost two-fold at 2 μM. Significant differences were detected when comparing parental and DR cells (p<0.0001). In non-metastatic cells (22Rv1), 5-AZA reduced their invasion capacity in parental cells by almost 80% while causing a 75% increase in 22Rv1-DR (p<0.05). Reduced migration capacity was achieved with 5-AZA treatment (2 μM) in DU145-DR and PC3-DR cells by almost 65% when compared to parental cells. These findings show the impact of DNMT1 in regulating cell migration and invasion, which are crucial for metastasis in DR PCa cells. This study highlights the crucial role of DNA methylation in therapy resistance, offering valuable insights for developing novel therapeutic approaches for managing docetaxel-resistant mCRPC. Sponsored by U54 PHSU-MCC (U54CA163071 & U54CA163068) and NIMHD (MD007579) grants. Citation Format: Carmen M. Ortiz-Sánchez, Rodniel Aviles, Gabriela Castro, Solimar Esteves, Valerie Rodriguez, Ralphdy Vergne, Lenin Godoy, Kosj Yamoah, Jong Park, Gilberto Ruiz-Deya. Exploring the role of DNMT1 in cell invasion and motility in docetaxel-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6413.