Fluoxetine Is Associated with Reduced Cell Viability and Decreased pERK1/2 Immunoreactivity in Ishikawa Endometrial Cancer Cells In Vitro: An Exploratory Study

Selective serotonin reuptake inhibitors are widely prescribed in oncology, yet their direct effects on endometrial cancer cell fate remain unclear. This study examined whether fluoxetine, at concentrations referenced to reported plasma exposure ranges, alters viability, cell death phenotype, DNA integrity and extracellular signal-regulated kinase 1/2 (ERK1/2) signalling. Ishikawa endometrial cancer cells and normal human dermal fibroblasts (HDFs) were exposed to fluoxetine (100–300 ng/mL) for a single exposure period of 48 h. Metabolic viability was assessed by MTT assay, cell death phenotypes by annexin V/propidium iodide (PI) flow cytometry, DNA fragmentation by TUNEL, and total and phosphorylated ERK1/2 (pERK1/2) by immunofluorescence; all experiments were performed in three independent experiments (n = 3), and per-experiment means were used as the unit of analysis. Fluoxetine reduced metabolic viability in Ishikawa cells, with significant reductions detected at 100 and 300 ng/mL, whereas HDF viability remained largely preserved. Flow cytometry showed predominantly viable populations in both cell types, with low early apoptotic, late apoptotic and annexin V−/PI+ fractions; no statistically significant treatment-related differences were detected in these cell death-associated populations, although analysis at a single 48 h endpoint cannot exclude earlier transient changes. TUNEL positivity showed a concentration-related numerical increase in Ishikawa cells, reaching statistical significance at 300 ng/mL, while remaining low in HDF cells. pERK1/2 immunoreactivity was significantly decreased at 300 ng/mL in both Ishikawa and HDF cells without a comparable change in total ERK1/2 immunoreactivity; because this readout was obtained by immunofluorescence only and was not validated by Western blotting, it is reported as a change in immunoreactivity rather than as confirmed pathway inhibition. These exploratory in vitro findings indicate that fluoxetine exposure is associated with reduced viability, DNA fragmentation and decreased pERK1/2 immunoreactivity in Ishikawa cells; the limited injury in HDF cells reflects a general non-malignant comparator response rather than cancer-specific selectivity. The findings are hypothesis-generating and require confirmation by protein- and transcript-level validation, pathway modulation experiments and additional malignant and non-malignant cell models.