Introduction and objective:
Endometrial cancer involves uncontrolled cell proliferation and cell cycle dysregulation. Natural compounds, such as microalgae-derived extracts, are being studied as potential chemopreventive agents. The aim of the study is to assess the effects of Chlorella pyrenoidosa water extract on proliferation, cytoskeletal marker expression, and cell cycle progression in human endometrial cancer cells.

Material and methods:
Endometrial adenocarcinoma cell lines (HEC-1-B, KLE) and patient-derived EDC cells were treated with chlorella extract at 50 to 1,000 µg/mL for 48 hours. Morphological changes were evaluated by May-Grünwald-Giemsa staining. Ki-67 and cytokeratin 7 expression were measured by flow cytometry and cell cycle distribution was analyzed using propidium iodide staining.

Results:
Treatment with C. pyrenoidosa extract induced morphological alterations and reduced cell density in all examined models. Ki-67 expression decreased, indicating reduced proliferative activity, with the strongest effect noted in HEC-1-B cells. Cytokeratin 7 expression was also reduced. Cell cycle analysis showed accumulation of EDC cells in the G0/G1 phase, whereas HEC-1-B cells demonstrated an increased S-phase fraction.

Conclusions:
C.pyrenoidosa water extract exerted antiproliferative effects in human endometrial cancer cells, associated with reduced proliferative activity, decreased cytokeratin 7 expression and altered cell cycle distribution. The obtained results indicate that chlorella extract may modulate key cellular features related to tumour cell growth and phenotype maintenance, supporting its relevance as a natural compound with chemopreventive potential in endometrial cancer models.