Ethyl acetate fraction of tiwai onion (Eleutherine palmifolia (L), Merr) increases the cytotoxicity of NK-92 cells against HeLa CCL-2 cells

Tiwai onion (Eleutherine palmifolia (L)., Merr) is a medicinal plant that has been believed as an anti-cancer treatment by the people of East Kalimantan. The immune effectors such as Natural Killer (NK) has been known to be related to immune surveillance through its cytotoxicity ability. This study aimed to determine the effect of ethyl acetate fraction of tiwai onion (EAFT) to increasing the cytotoxicity of NK-92 cells against HeLa CCL-2 cells. HeLa CCL-2 cells and NK-92 Cells were co-cultured and divided into control negative and series of EAFT concentrations, 125, 250, 500 and 1000μg/ml, respectively. HLA-G was induced by IL-10 treatment before EAFT exposure. Apoptosis of Hela CCL-2 cells was determined by flow cytometry, whereas soluble HLA-G and granzyme secretion were measured using ELISA. Membrane-bound HLA-G was assayed using the immunofluorescence method and calculated using ImageJ. All data obtained were analyzed by Anova and LSD test. EAFT administration significantly increased apoptosis of HeLa CCL-2 cells during co-culture with NK-92 cells, in a dose-dependent manner. This increase is significantly higher when compared to the apoptotic effect of EAFT on the HeLa cell culture alone. EAFT suppressed HLA-G membrane expression of HeLa CCL-2 cell in co-culture. Granzyme secretion was inhibited by EAFT, particularly at a concentration of 125μg/ml. It could be concluded that EAFT increased the cytotoxicity of NK-92 cells against HeLa CCL-2 cells, through suppression of HLA-G expression.