Synergistic Growth Inhibitory Effects of Eryngium kotschyi Extracts with Conventional Cytotoxic Agents: Cisplatin and Doxorubicin against Human Endometrium Cancer Cells

Background: Endometrial cancer is one of the most common types of cancer. For this reason, various studies have been carried out on its treatment and the effects of natural products on this disease. Objectives: This study aimed to examine the growth inhibitory effects of Eryngium kotschyi Boiss. ethyl acetate [EKE] and butanol [EKB] obtained from the main methanol [EKM] extract from the aerial parts on human endometrium carcinoma [RL95-2] cells and their synergistic effect with cisplatin or doxorubicin. Methods: RL95-2 cells were treated with E. kotschyi extracts either alone or in combination with cisplatin or doxorubicin. The effects on cell growth were determined using the MTT assay and real-time cell analysis xCELLigence. Results: The extracts demonstrated growth inhibitory activity, with a certain degree of selectivity against the RL95-2 cell line. Synergistic effects of EKE/cisplatin or doxorubicin at different concentration levels were demonstrated in RL95-2 cells. In some instances, the EKE/doxorubicin combinations resulted in antagonistic effects. The reduction level of cell viability was different and specific to each combination for the RL95-2 cell line. Conclusion: The growth inhibitory activity of cisplatin or doxorubicin, as a single agent, may be modified by combinations of the extracts and be synergistically enhanced in some cases. A significant synergistic effect of EKE on the RL95-2 cell line with cisplatin and doxorubicin was observed. This cytotoxic effect can be investigated in terms of molecular mechanisms. This study is the first of its kind in the literature. The mechanisms involved in this interaction between chemotherapeutic drugs and plant extracts remain unclear and should be further evaluated.