Keimyung Med J.  2020 Jun;39(1):6-13. 10.46308/kmj.2020.00059.

Cucurbitacin E’s Anti-Cancer Effects on HCT116 Human Colon Cancer Cells by Controlling Expression and Phosphorylation Levels of Caspase-9, eIF-2α, and ATF-4

Affiliations
  • 1Department of Molecular Medicine, Keimyung University School of Medicine, Daegu, Korea

Abstract

Cucurbitacin E is a pivotal member of the cucurbitacin family and has been shown to have anti-cancer effects. However, until now, the anti-cancer effect and mode of action of cucurbitacin E in human colon cancer cells remain unclear. In this study, we investigated whether cucurbitacin E inhibits the growth of HCT116 human colorectal cancer cells. Treatment of cucurbitacin E at 1 mM markedly reduced the survival of HCT116 cells. Moreover, treatment of cucurbitacin E at 1 mM caused nuclear DNA fragmentation in HCT116 cells, pointing out its apoptosis-inducing effect. Treatment of cucurbitacin E at 1 mM also led to the activation of caspase-9 and poly(ADP‑ribose) polymerase (PARP) cleavage without affecting expression of death receptor (DR)-4/5 in HCT116 cells. Furthermore, while treatment of cucurbitacin E at 1 mM had no effect on expression of Mcl-1, it largely increased expression and phosphorylation of eukaryotic translation initiation factor-2α (eIF-2α) and activating transcription factor-4 (ATF-4) in HCT116 cells. Treatment of cucurbitacin E at 1 mM further up-regulated phosphorylation of extracellular signal-regulated kinase-1/2 (ERK-1/2), but not c-Jun N-terminal kinase1/2 (JNK-1/2), in HCT116 cells. However, treatment with PD98059, an inhibitor of ERK-1/2, that strongly blocked activation of ERK-1/2 had no effect on reduction of survival of HCT116 cells treated with cucurbitacin E at 1 mM. Taken together, these findings demonstrate that cucurbitacin E at 1 mM has strong anti-survival and pro-apoptotic effects on HCT116 cells, which are mediated through control of the expression and phosphorylation levels of caspase-9, PARP, eIF-2α, and ATF-4.

Keyword

Apoptosis; ATF-4; Caspase-9; Cucurbitacin E; eIF-2α; HCT116
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