Annonacin Exerts Antitumor Activity through Induction of Apoptosis and Extracellular Signal‑regulated Kinase Inhibition

Background: Endometrial cancer (EC) is the most common gynecologic malignancy in developed countries. Annonacin, a natural pure compound extracted from the seeds of Annona muricata, is a potential alternative therapeutic agent to treat EC. Objective: To study the antitumor activity of annonacin and its mechanism of action in EC cells (ECCs). Materials and Methods: Viability of ECCs treated with annonacin for 72 h was determined using methyl thiazolyl tetrazolium assay. The induction of cell cycle arrest and apoptotic cell death was evaluated using propidium iodide and annexin V‑PE/7‑AAD assay, respectively. DNA strand breaks were visualized using transferase dUTP nick end labeling assay, and the effects of annonacin on survival signaling were determined using western blotting. Results: Annonacin exhibited antiproliferative effects on EC cell lines (ECC‑1 and HEC‑1A) and primary cells (EC6‑ept and EC14‑ept) with EC₅₀ values ranging from 4.62 to 4.92 µg/ml. EC cells were shown arrested at G2/M phase after treated with 4 µg/ml of annonacin for 72 h. This led to a significant increase in apoptotic cell death (65.7%) in these cells when compared to vehicle‑treated cells (P < 0.005). We further showed that annonacin‑mediated apoptotic cell death was associated with an increase in caspase‑3 cleavage and DNA fragmentation. Cell apoptosis was accompanied with downregulation of extracellular signal‑regulated kinase survival protein expression and induction of G2/M cell cycle arrest. Conclusion: Annonacin may be a potential novel therapeutic agent for EC patients.