Dextromethorphan Enhances Apoptosis and Suppresses EMT in PANC-1 Pancreatic Cancer Cells: Synergistic Effects with Gemcitabine

This study aimed to evaluate the effects of dextromethorphan (DX), alone and in combination with gemcitabine (GEM), on cell viability, apoptosis, and epithelial-mesenchymal transition (EMT) markers in PANC-1 human pancreatic cancer cells. PANC-1 human pancreatic cancer cells were cultured and treated with varying concentrations of dextromethorphan (DX), gemcitabine (GEM), and 5-fluorouracil (5-FU), both as monotherapies and in combination. Cytotoxic effects were assessed using the MTT assay, and IC₅₀ values were calculated at 24, 48, and 72 h. Apoptotic responses were evaluated using Annexin V-FITC/PI staining followed by flow cytometry. Protein expression levels of Bax, Bcl-2, and Vimentin were determined via immunocytochemistry, while EMT markers (E-cadherin, N-cadherin, Vimentin) were analyzed using flow cytometry. Relative mRNA expression of apoptotic and EMT-related genes was quantified by qRT-PCR. DX exhibited time- and dose-dependent cytotoxicity in PANC-1 cells, with IC₅₀ values of 280.4 µM at 24 h, 163.2 µM at 48 h, and 105.6 µM at 72 h. For GEM, the 72 h IC₅₀ was 57.53 µM. The combination of DX 50 µM + GEM 12.5 µM resulted in significantly lower cell viability (24.93 ± 3.12%) compared to GEM 25 µM (35.33 ± 5.22%) and DX 100 µM (51.40 ± 3.10%) (<i>p</i> < 0.001). Flow cytometry revealed significant increases in early (21.83 ± 1.32%) and late apoptotic cells (32.20 ± 0.84%) in the combination group, with a corresponding reduction in viable cells compared to control (24.93 ± 3.12% vs. 89.53 ± 0.97%, <i>p</i> < 0.001). Immunocytochemical analysis showed increased Bax-positive cell count (62.0 cells/unit area), and decreased Bcl-2 (19.0) and Vimentin (28.0) levels in the combination group compared to control (Bax: 15.0, Bcl-2: 60.0, Vimentin: 70.0) (<i>p</i> < 0.001). Flow cytometry for EMT markers demonstrated increased E-cadherin (83.84 ± 0.65%) and decreased Vimentin (71.04 ± 1.17%) and N-cadherin (30.47 ± 0.72%) expression in the DX + GEM group compared to EMT control (E-cadherin: 68.97 ± 1.43%, Vimentin: 91.00 ± 0.75%, N-cadherin: 62.47 ± 1.13%) (<i>p</i> < 0.001). qRT-PCR supported these findings with increased Bax (2.1-fold), E-cadherin (2.0-fold), and reduced Bcl-2 (0.3-fold) and XIAP (0.6-fold) in the combination group (<i>p</i> < 0.05). Dextromethorphan, particularly in combination with gemcitabine, appears to enhance apoptosis and suppress EMT-associated marker expression in PANC-1 cells, supporting its potential as an adjuvant agent in pancreatic cancer therapy.