Abstract Background: Metastatic castration-resistant prostate cancer (mCRPC) carries poor prognosis due to androgen- and chemotherapy-resistance. Nearly half of patients develop resistance to docetaxel (DR), underscoring the need for new strategies. Aberrant DNA methylation contributes to drug resistance through gene silencing. We investigated whether DNMT1 inhibition via 5-Azacytidine (5-AZA) could attenuate crucial process in epithelial-to-mesenchymal (EMT) such as invasion and migration of DR prostate cancer (PCa) cells. Methods: Parental and docetaxel-resistant PC3 cells were treated with 5-AZA (0. 5–16 µM, 72 h). Viability was measured by MTT. Protein markers (AR, ARv7, MDR1, GSTP1, DNMT1) were assessed by Western blot; invasion and migration by Matrigel and wound-healing assays; and EMT markers (CDH1, SNAI2, VIM) by RT-PCR. Results: 5-AZA reduced viability in a dose-dependent manner in both cell types. From these results, non-toxic concentrations of 5-AZA (1 and 2 µM) were selected for further experiments. DNMT1 inhibition and GSTP1 re-expression were successfully achieved, confirming global DNA hypomethylation. Invasion of PC3-DR cells was reduced by ∼90% versus untreated controls and by ∼40% compared with 5-AZA-treated parental cells (1 µM: p0. 0001; 2 µM: p0. 01). Migration was also significantly suppressed in DR cells after 48h of exposure to 1 µM and 2 µM 5-AZA. EMT modulation included significant CDH1 upregulation (1 µM: p0. 001; 2 µM: p0. 01) in PC3-DR cells when compared to untreated cells. Conclusions: DNMT1 inhibition decreases invasion and migration of docetaxel-resistant PCa cells, mediated in part by EMT marker modulation. These findings support DNA methylation as a therapeutic target and provide rationale for epigenetic-based strategies in resistant mCRPC. Sponsored by U54 PHSU-MCC Grants: U54CA163071 NIH-NIMHD Grant MD007579, and NIH-NIGMS Grant U54GM133807. Citation Format: Carmen Ortiz-Sánchez, Gabriela Castro, Shakira Abad, Solimar Esteves-Vega, Valerie Rodríguez, Stephanie Montalvo, Rodniel Avilés, Ralphdy Vergne, Gustavo Alayón, Caleb Santiago, Lenin Godoy, Gilberto Ruiz-Deyá, Jong Park. DNMT1 inhibition suppresses EMT-driven invasion and migration in docetaxel-resistant prostate cancer 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 (2Suppl): Abstract nr A052.
Ortíz et al. (Tue,) studied this question.