Naturally Occurring Sesquiterpene Lactone-Santonin, Exerts Anticancer Effects in Multi-Drug Resistant Breast Cancer Cells by Inducing Mitochondrial Mediated Apoptosis, Caspase Activation, Cell Cycle Arrest, and by Targeting Ras/Raf/MEK/ERK Signaling Pathway
Authors: Mingzhu Huang
Yiqun Du
Zhiqiang Wu
Zhonghua Tao
Wangjun Yan
Chenchen Wang
Journal: Medical Science Monitor (2019)
Discipline: CLINICAL MEDICINE
Keywords: Sesquiterpene lactones; santonin; breast cancer; SK-BR-3 cells; anticancer effects
Affiliations: Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China (mainland)., Department of Musculoskeletal Oncology, Fudan University Shanghai Cancer Center, Shanghai, China (mainland)., Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai, China (mainland).

Abstract:  BACKGROUND Sesquiterpene lactones have gained tremendous attention owing to their potent anticancer properties. The main focus of this study was to evaluate the anticancer effects of a naturally occurring sesquiterpene lactone, santonin, against human breast cancer SK-BR-3 cells. MATERIAL AND METHODS Cell counting kit 8 assay was used for the determination of cell viability. Apoptosis was detected by DAPI (4',6-diamidino-2-phenylindole) and annexin V/propidium iodide (IP) staining. Flow cytometry was used for cell cycle analysis and western blotting was used for the estimation of protein expression. RESULTS Results showed that santonin exerts significant anti-proliferative effects on the SK-BR-3 breast cancer cells in a concentration dependent manner. Santonin showed an IC₅₀ of 16 µM against SK-BR-3 cells. DAPI staining showed that santonin caused DNA fragmentation in the SK-BR-3 cells, which is indicative of apoptosis. Annexin V/PI staining showed that apoptotic cell percentage increased up to 34.32% at 32 µM concentration of santonin. Santonin also caused an increase in the expression of Bax, caspase-3, and caspase-9, and a decrease in the expression of Bcl-2. Santonin also caused the arrest of the SK-BR-3 cells at the G2/M phase of the cell cycle and suppressed the expression of cyclin A and B1. Finally, santonin could also block the Raf/MEK/ERK pathway in breast cancer cells. CONCLUSIONS The findings of this study suggest the potential for the naturally occurring sesquiterpene lactone santonin in breast cancer treatment and also suggest that it could be developed as a promising anticancer agent. 

Retracted: Yes

PubPeer comments:
 Figure 2.  DAPI (4u2019,6-diamidino-2-phenylindole) assay showing induction of apoptosis in SK-BR-3 at indicated concentrations of santonin. The figure shows that santonin induces apoptosis in SK-BR-3 cells concentration dependently . Some repeated visual elements are marked. ![file] , 
 The corresponding author s choice of email address is unexpected. ![file] , 
 Figs 4, 5.  Effect of santonin on the expression of Bax and Bcl-2 as depicted by western blot analysis. The figure shows that santonin increases apoptosis percentage of SKBR-3 cells concentration dependently ...  Effect of santonin on the expression of caspase-3 and caspase-9 as depicted by western blot analysis. The figure shows that santonin increases caspase-3 and caspase-9 expression in SK-BR-3 cells concentration dependently . ![file] For comparison: Figure 9 from [He, Li Xia (2018)] .  Inhibition of mTOR PI3K AKT signalling pathway by lupeol at indicated concentrations as shown by the western blotting . With horizontally-flipped version. ![file] , 
 Retracted [30 December 2020] .  It is now clear that the photomicrographs in Figure 2 are duplicates of the same image and that Figures 4 and 5 have been copied from a publication  Lupeol triterpene exhibits potent antitumor effects in A427 human lung carcinoma cells via mitochondrial mediated apoptosis, ROS generation, loss of mitochondrial membrane potential and downregulation of m-TOR PI3Ksol;AKT signalling pathway by Wei He, Xiang Li, Shuyue Xia, PMID: 30003730. Because the manuscript contains non-credible results and has also breached copyright, this journal is retracting the above publication. ,