Prodigiosin activates endoplasmic reticulum stress cell death pathway in human breast carcinoma cell lines

• Published in: Toxicology and applied pharmacology 2012-12, Vol.265 (3), p.325-334
• Main Authors: Pan, Mu-Yun, Shen, Yuh-Chiang, Lu, Chien-Hsing, Yang, Shu-Yi, Ho, Tsing-Fen, Peng, Yu-Ta, Chang, Chia-Che
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Activating Transcription Factor 6 - genetics; Activating Transcription Factor 6 - metabolism; Antineoplastic Agents - pharmacology; APOPTOSIS; BCL2; Biological and medical sciences; BIOLOGICAL RECOVERY; BIOLOGICAL STRESS; Breast cancer; Breast carcinoma; Breast Neoplasms - drug therapy; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; c-Jun amino-terminal kinase; Cancer; CARCINOMAS; Cell death; Cell Death - drug effects; Cell Line, Tumor; Cell survival; CHOP/GADD153; CLEAVAGE; Colonies; COLONY FORMATION; Cytotoxicity; eIF-2 Kinase - genetics; eIF-2 Kinase - metabolism; ENDOPLASMIC RETICULUM; Endoplasmic Reticulum Stress - drug effects; Endoplasmic Reticulum Stress - physiology; Endoribonucleases - genetics; Endoribonucleases - metabolism; ER stress; Female; Gene Expression Regulation, Neoplastic - drug effects; Gynecology. Andrology. Obstetrics; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; Humans; Immunoblotting; INHIBITION; Initiation factor eIF-2; Mammary gland diseases; MAMMARY GLANDS; MCF-7 Cells; Medical sciences; Mortality; PHOSPHORYLATION; PIGMENTS; Poly(ADP-ribose) polymerase; Prodigiosin; Prodigiosin - pharmacology; PROMOTERS; Protein folding; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; PROTEINS; Reverse Transcriptase Polymerase Chain Reaction; RNA - chemistry; RNA - genetics; Signal transduction; Stress; Survival; thapsigargin; TOXICITY; Toxicology; Transcription; Transcription Factor CHOP - genetics; Transcription Factor CHOP - metabolism; Tumor cell lines; Tumors; Unfolded Protein Response; Up-Regulation - drug effects
• ISSN: 0041-008X; 1096-0333
• DOI: 10.1016/j.taap.2012.08.034

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. [Display omitted] ► Prodigiosin is a bacterial tripyrrole pigment with potent anticancer effect. ► Prodigiosin is herein identified as an endoplasmic reticulum (ER) stress inducer. ► Prodigiosin-induced cytotoxicity involves ER stress-mediated cell death. ► Prodigiosin transcriptionally induces CHOP to suppress BCL2 for evoking cell death. ► Prodigiosin engages the IRE1–JNK and PERK–eIF2α pathways to up-regulate CHOP.