Zerumbone enhances TRAIL-induced apoptosis through the induction of death receptors in human colon cancer cells: Evidence for an essential role of reactive oxygen species
Authors: Bokyung Sung
Pornngarm Limtrakul
Bharat B Aggarwal
Supachai Yodkeeree
Journal: Cancer Research (2009)
Discipline: CLINICAL MEDICINE
Keywords: Traditional medicine; Zerumbone; Anticancer effects; TRAIL; Apoptosis
Affiliations: Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, 77030, USA.

Abstract:  Identification of the active component and mechanisms of action of traditional medicines is highly desirable. We investigated whether zerumbone, a sesquiterpene from tropical ginger, can enhance the anticancer effects of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We found that zerumbone potentiated TRAIL-induced apoptosis in human HCT116 colon cancer cells and that this correlated with the up-regulation of TRAIL death receptor (DR) 4 and DR5. Induction of DRs occurred at the transcriptional level, and this induction was not cell-type specific, as its expression was also up-regulated in prostate, kidney, breast, and pancreatic cancer cell lines. Deletion of DR5 or DR4 by small interfering RNA significantly reduced the apoptosis induced by TRAIL and zerumbone. In addition to up-regulating DRs, zerumbone also significantly down-regulated the expression of cFLIP but not that of other antiapoptotic proteins. The induction of both DRs by zerumbone was abolished by glutathione and N-acetylcysteine (NAC), and this correlated with decreased TRAIL-induced apoptosis, suggesting a critical role of reactive oxygen species. Inhibition of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase but not of Jun NH(2)-terminal kinase abolished the effect of zerumbone on DR induction. Zerumbone also induced the p53 tumor suppressor gene but was found to be optional for DR induction or for enhancement of TRAIL-induced apoptosis. Both bax and p21, however, were required for zerumbone to stimulate TRAIL-induced apoptosis. Overall, our results show that zerumbone can potentiate TRAIL-induced apoptosis through the reactive oxygen species-mediated activation of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase leading to DR4 and DR5 induction and resulting in enhancement of the anticancer effects of TRAIL. 

Retracted: No

PubPeer comments:
 The presented in figures 4Q, as well as the original uncrossed blot provided in figure S9A appear to be a composite of several blots. This is especially apparent when the image contrast is increased. The splice marks are shown with red arrows. The uncropped blots are not provided for most of the blots in the paper making it difficult to assess if there are any other issues. ![file] , 
 ![file] Some cell lines express Gli1 at much lower levels compared to others. For instance, see H460 (asterisk, red box) compared to H358 in  a . Corresponding loading controls shown in  c . Longer exposure films of the **same gels** were used instead to assess differences in Gli1 protein levels. For instance, see  b versus  a (red box), same loading controls (c). , 
 Thank you very much for responding to my comments and for providing new blots. I feel that the data would have been better represented independently for each cell line. This could have been provided with justification that you have written here regarding the relative levels of Gli1 expression in different cell lines. In its current form, it gives the impression that it is possible to compare the response between cell lines. I appreciate your explanation, but still feel that presenting the blots in this form is problematic, especially considering they are described as being  uncropped scans in the legend of figure S9, and there is no mention of the image treatment in the materials and methods. The raw blots with different exposure levels are not presented in the sup materials. , 
 Thank you and I agree that these low and high exposure blots should be presented. For maximum transparency, we will submit them to the journal. Thanks again! ,