OBJECTIVES : Various types of stresses disturb homeostasis in the endoplasmic reticulum (ER) triggerring the ER stress response. Duration and intensity of ER stress determines further cellular physiology - adaptive response, or if the effect of stressors is prolonged and intense - cell death. Main objective of this study is in vitro examination of the effects of semisynthetic bile acid, 12-oxochenodeoxycholic acid (12-monoketocholic acid, 12-MKC) on doxorubicin-induced stress of the ER on the human breast adenocarcinoma cell model as well as the influence of 12-MKC on the expression of apoptosis markers (BAX and BCL-2) induced by doxorubicin.

METHODS : The continuous cell line of human breast adenocarcinoma cells (MCF-7) was incubated in the medium containing doxorubicin (0,25 uM) and the selected non-toxic concentration of 12-MKC (25uM). After incubation for 24 hours, the mRNA was isolated, and gene expression was determined by RT-qPCR and analysed by comparative ΔCt method.

RESULTS : Incubation of cells with doxorubicin increased the expression of ER stress marker, GRP-78, however co-incubation with 12-MKC significantly increased the expression of GRP-78 compared both to the control group and the group of doxorubicin treated cells (p<0.001). The increase in expression of GRP-78 was associated with an increase in the expression of pro-apoptotic BAX as well as BAX to BCL-2 ratio, relative to control (p<0.001) and a group of doxorubicin-treated cells (p=0.001), indicating significant activation of apoptosis by mitochondrial pathway in co-treated group.

CONCLUSIONS : On the basis of the obtained results, it can be concluded that 12-MKC is a semisynthetic bile acid derivative with the potential to improve existing and to develop novel strategies in the treatment of patients with malignant diseases. Acknowledgment: Supported by HORIZON2020 MEDLEM project No.690876, and the Project for Scientific and Technological Development of Vojvodina No. 114-451-2072-/2016-02, and project III41012 of Ministry of Education, Science and Technological Development of the Republic of Serbia.