Abstract
Abstract
The endoplasmic reticulum (ER) is a cellular organelle that is primarily responsible for oxidative protein folding. When the protein folding load in cells exceeds the protein folding capacity, ER stress occurs. The ER stress pathway is a prominent regulator of cancer cell death and as a result, ER stress inducers are being exploited pharmacologically. Cytotoxic ER stress is typically regulated by the transcription factor, C/EBP homologous protein 10 (CHOP10). Transcriptional products of CHOP10 include pro-apoptotic genes, such as tribbles-related protein 3 (TRB3), death receptor-5 (DR5), and ER oxidoreductase 1α (ERO1α). Our previous data showed that apoptosis mediated by 15deoxy, Δ12,14 prostamide J2 (15dPMJ2) occurred in an ER stress-dependent manner. However, the signaling pathway that regulates 15dPMJ2 mediated ER stress apoptosis has not been identified. Therefore, the goal of this study is to determine the role of CHOP10 and its transcriptional targets in ER stress apoptosis that is induced by 15dPMJ2 in colon cancer cells. According to our data, 15dPMJ2 was 3-fold more effective in inducing apoptosis in the human colon cancer cell line, HCT116, compared to the non-tumorigenic colon cell line, FHC. The induction of apoptosis in HCT116 cells occurred coincident with a significant increase in CHOP10 protein expression. In addition, blockade of the ER stress pathway with 4-phenylbuterate (PBA) or salubrinal prevented apoptosis indicating that cell death is reliant upon ER stress. To determine the role of CHOP10 in this process, CRISPR/Cas9 CHOP10 knockout HCT116 cells (CHOP10-KO-HCT116) were generated. As anticipated, 15dPMJ2 increased CHOP10 expression in wt-HCT116 cells but not in CHOP10-KO-HCT116 cells. Furthermore, 15dPMJ2 increased the expression of ERO1α, DR5, TRB3, and it induced apoptosis in wt-HCT116 cells, but not in CHOP10-KO cells. Interestingly, the induction of TRB3, but not DR5 or ERO1α, was completely inhibited in cells devoid of CHOP10 expression. Therefore, the activity of protein kinase B (PKB)/Akt, a known TRB3 target, was investigated. CHOP10 stimulation by 15dPMJ2 inactivated Akt in wt-HCT116 cells, but not in CHOP10-KO cells. These findings suggest the importance of CHOP10, TRB3, and Akt in the control of the ER stress-mediated apoptosis in response to 15dPMJ2 treatment. Thus, 15dPMJ2 is a potential chemotherapeutic agent that inhibits PKB/Akt survival signaling by upregulating the CHOP10/TRB3 pathway to prevent colon cancer growth.
Citation Format: Hussam Albassam, Daniel A. Ladin, Rukiyah Van Dross. CHOP10/TRB3/Akt signaling regulates ER stress apoptosis in colon cancer cells treated with prostamide-J [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3873.