THYMOQUINONE TREATMENT ALTERS CELL CYCLE DISTRIBUTION IN PA-1 OVARIAN CANCER CELLS: A FLOW CYTOMETRIC ANALYSIS

Abstract

Background: Ovarian cancer has the highest mortality rate among gynecological cancers. Thymoquinone, extracted from Nigella sativa, exhibits anticancer activity in multiple experimental models; however, its effects on ovarian cancer cell cycle dynamics have not been systematically characterized.

Objective: We examined redistribution of cell cycle phases and cytotoxicity following thymoquinone exposure in PA-1 ovarian cancer cells.

Methods: PA-1 cells were treated with thymoquinone or vehicle control. Flow cytometry was used to quantify the G1, S, and G2 phase distributions (n=3 technical replicates per group). The MTT assay was used to assess viability across the 0–100 µg/mL thymoquinone concentration range. We applied Welch's t-test with a Benjamini-Hochberg false-discovery rate adjustment for between-group comparisons.

Results: Thymoquinone shifted the cell cycle distribution across all measured phases. G1 increased from 42.35±1.88% to 53.91±1.43%, a 27% relative increase (FDR-adjusted p=0.00317). S phase declined from 20.64±1.00% to 15.53±0.82% (p=0.00509), a 25% reduction. G2 decreased from 35.93±2.37% to 28.94±0.27% (p=0.0425), a 19% reduction. All three phase changes survived multiple-comparison corrections. Viability declined with increasing concentration, producing an IC50 of 78.77 µg/mL.

Conclusion: Thymoquinone treatment enriched the G1 phase cells in PA-1 ovarian cancer while depleting the S and G2 phases. This redistribution pattern indicates interference at the G1/S checkpoint and supports investigation of thymoquinone as a cell-cycle-modulating agent in ovarian cancer.