title: Reactive oxygen species-dependent EndoG release mediates cisplatin-induced caspase-independent apoptosis in human head and neck squamous carcinoma cells.
abstract: Cisplatin is a chemotherapeutic agent that is widely used to treat cancers such as head and neck squamous cell carcinoma (HNSCC). Previously, we have reported that cisplatin induced an early caspase-dependent apoptosis (8 hr) in a HNSCC cell, HN4. In this study, we examined a late caspase-independent apoptosis as well as an early caspase-dependent apoptosis in cisplatin-treated HN4 cells. While z-VAD-fmk, a pan-caspase inhibitor, blocked the caspase activities and protected cells from the early apoptosis, it did not provide protection against delayed apoptosis occurring after extended exposure (16 hr) to cisplatin, suggesting that the delayed apoptotic response in the presence of z-VAD-fmk was caspase-independent. Cisplatin treatment induced reactive oxygen species (ROS) generation, loss of the mitochondrial membrane potential (MMP) and nuclear translocation of endonuclease G (EndoG). Small interfering RNA mediated-knockdown of EndoG significantly protected cells from the delayed apoptosis induced by cisplatin in the presence of z-VAD-fmk. Overexpression of Bcl-2 in HN4 cells prevented loss of MMP, nuclear translocation of EndoG and protected cells from the delayed apoptosis induced by cisplatin in the presence of z-VAD-fmk. Pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, prevented both ROS generation, loss of the MMP and nuclear translocation of EndoG. Together, our data indicate that cisplatin treatment induced ROS-mediated loss of the MMP, and, then, the nuclear translocation of EndoG, which played a crucial role in caspase-independent apoptosis of HN4 cells in the presence of z-VAD-fmk. This is the first report about the involvement of EndoG in cisplatin-induced caspase-independent apoptosis of cells.
authors.affiliation: Department of Biological Sciences, University of Ulsan, Ulsan, Korea.
authors.forename: Jong Soo
authors.initials: JS
authors.lastname: Kim
authors.forename: Ji Hae
authors.initials: JH
authors.lastname: Lee
authors.forename: Won Wook
authors.initials: WW
authors.lastname: Jeong
authors.forename: Dae Hwa
authors.initials: DH
authors.lastname: Choi
authors.forename: Hee Jeong
authors.initials: HJ
authors.lastname: Cha
authors.forename: Do Ha
authors.initials: DH
authors.lastname: Kim
authors.forename: Joong Keun
authors.initials: JK
authors.lastname: Kwon
authors.forename: Soon Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Jae Hoo
authors.initials: JH
authors.lastname: Park
authors.forename: Hong Rae
authors.initials: HR
authors.lastname: Cho
authors.forename: Seon Ho
authors.initials: SH
authors.lastname: Lee
authors.forename: Sang Kyu
authors.initials: SK
authors.lastname: Park
authors.forename: Byung Ju
authors.initials: BJ
authors.lastname: Lee
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Min
authors.forename: Jeong Woo
authors.initials: JW
authors.lastname: Park
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism*; D002945:Cisplatin / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D020287:In Situ Nick-End Labeling; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013347:Subcellular Fractions
chemical_list: D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D045304:Cytochromes c; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D020169:Caspases; D002945:Cisplatin