AMP-activated protein kinase (AMPK)/Ulk1-dependent autophagic pathway contributes to C6 ceramide-induced cytotoxic effects in cultured colorectal cancer HT-29 cells

• DOI: 10.1007/s11010-013-1608-8
• Publication Date: 2013-03-18T11:17:14Z
• Authors: Hai-zhong Huo; Bing Wang; Jian Qin; Shan-yu Guo; Wen-yong Liu; Yan Gu
• Keywords: Sirolimus; 0303 health sciences; Cell Survival; Intracellular Signaling Peptides and Proteins; Antineoplastic Agents; Apoptosis; AMP-Activated Protein Kinases; Protein Serine-Threonine Kinases; Ribonucleotides; Aminoimidazole Carboxamide; Ceramides; HCT116 Cells; 3. Good health; Enzyme Activation; 03 medical and health sciences; Autophagy; Autophagy-Related Protein-1 Homolog; Humans; Everolimus; Colorectal Neoplasms; HT29 Cells; Signal Transduction

Colorectal cancer is the second leading cause of cancer-related deaths. Drug resistance and/or off-target toxicity against normal cells limit the effectiveness of current chemotherapies for the treatment of colorectal cancer. In the current study, we studied the potential cytotoxic effects of short-chain and cell-permeable C6 ceramide in cultured colorectal cancer HT-29 cells and focused on the underlying mechanisms. We observed that C6 ceramide-induced HT-29 cell death and growth inhibition in a dose- and time-dependent manner. However, no significant apoptosis was observed in C6 ceramide-treated HT-29 cells. Our data support that autophagy contributed to C6 ceramide-induced cytotoxic effects, as autophagy inhibitors, 3-methyladenine (3-MA) and hydroxychloroquine, inhibited C6 ceramide's effect; however, autophagy activators, everolimus (RAD001) and temsirolimus, mimicked C6 ceramide effects and induced HT-29 cell death. Further, we indentified that AMP-activated protein kinase (AMPK)/Ulk1 signaling was required for autophagy induction by C6 ceramide, and AMPK silencing by a specific short hairpin RNA suppressed C6 ceramide-induced autophagy and cytotoxic effects. Reversely, forced activation of AMPK by its activator AICAR or by genetic manipulation caused autophagic death in HT-29 cells, which was inhibited by 3-MA. Our results suggest that autophagy, but not apoptosis, is a major contributor for C6 ceramide-induced cytotoxic effects in HT-29 cells, and activation of AMPK/Ulk1 is required for the process.