title: Prodigiosin activates endoplasmic reticulum stress cell death pathway in human breast carcinoma cell lines.
abstract: Prodigiosin is a bacterial tripyrrole pigment with potent cytotoxicity against diverse human cancer cell lines. Endoplasmic reticulum (ER) stress is initiated by accumulation of unfolded or misfolded proteins in the ER lumen and may induce cell death when irremediable. In this study, the role of ER stress in prodigiosin-induced cytotoxicity was elucidated for the first time. Comparable to the ER stress inducer thapsigargin, prodigiosin up-regulated signature ER stress markers GRP78 and CHOP in addition to activating the IRE1, PERK and ATF6 branches of the unfolded protein response (UPR) in multiple human breast carcinoma cell lines, confirming prodigiosin as an ER stress inducer. Prodigiosin transcriptionally up-regulated CHOP, as evidenced by its promoting effect on the CHOP promoter activity. Of note, knockdown of CHOP effectively lowered prodigiosin's capacity to evoke PARP cleavage, reduce cell viability and suppress colony formation, highlighting an essential role of CHOP in prodigiosin-induced cytotoxic ER stress response. In addition, prodigiosin down-regulated BCL2 in a CHOP-dependent manner. Importantly, restoration of BCL2 expression blocked prodigiosin-induced PARP cleavage and greatly enhanced the survival of prodigiosin-treated cells, suggesting that CHOP-dependent BCL2 suppression mediates prodigiosin-elicited cell death. Moreover, pharmacological inhibition of JNK by SP600125 or dominant-negative blockade of PERK-mediated eIF2α phosphorylation impaired prodigiosin-induced CHOP up-regulation and PARP cleavage. Collectively, these results identified ER stress-mediated cell death as a mode-of-action of prodigiosin's tumoricidal effect. Mechanistically, prodigiosin engages the IRE1-JNK and PERK-eIF2α branches of the UPR signaling to up-regulate CHOP, which in turn mediates BCL2 suppression to induce cell death.
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.
authors.forename: Mu-Yun
authors.initials: MY
authors.lastname: Pan
authors.forename: Yuh-Chiang
authors.initials: YC
authors.lastname: Shen
authors.forename: Chien-Hsing
authors.initials: CH
authors.lastname: Lu
authors.forename: Shu-Yi
authors.initials: SY
authors.lastname: Yang
authors.forename: Tsing-Fen
authors.initials: TF
authors.lastname: Ho
authors.forename: Yu-Ta
authors.initials: YT
authors.lastname: Peng
authors.forename: Chia-Che
authors.initials: CC
authors.lastname: Chang
mesh_terms: D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000502:physiology; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D061986:MCF-7 Cells; D011353:Prodigiosin / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D056811:Unfolded Protein Response; D015854:Up-Regulation / Q000187:drug effects; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism
chemical_list: D051702:Activating Transcription Factor 6; D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; D004722:Endoribonucleases; D006360:Heat-Shock Proteins; D011353:Prodigiosin; D017346:Protein Serine-Threonine Kinases; D012313:RNA; D051742:Transcription Factor CHOP; D019892:eIF-2 Kinase; C497111:ATF6 protein, human; C000717247:HSPA5 protein, human; C528229:ERN1 protein, human