title: CBP-mediated FOXO-1 acetylation inhibits pancreatic tumor growth by targeting SirT.
abstract: Here, we investigated the potential mechanism of capsaicin-mediated apoptosis in pancreatic cancer cells. Capsaicin treatment phosphorylated c-jun-NH2-kinase (JNK); forkhead box transcription factor, class O (FOXO1); and BIM in BxPC-3, AsPC-1, and L3.6PL cells. The expression of BIM increased in response to capsaicin treatment. Capsaicin treatment caused cleavage of caspase-3 and PARP, indicating apoptosis. Antioxidants tiron and PEG-catalase blocked capsaicin-mediated JNK/FOXO/BIM activation and protected the cells from apoptosis. Furthermore, capsaicin treatment caused a steady increase in the nuclear expression of FOXO-1, leading to increased DNA binding. Capsaicin-mediated expression of BIM was found to be directly dependent on the acetylation of FOXO-1. The expression of CREB-binding protein (CBP) was increased, whereas SirT-1 was reduced by capsaicin treatment. Using acetylation mimic or defective mutants, our result demonstrated that phosphorylation of FOXO-1 was mediated through acetylation by capsaicin treatment. JNK inhibitor attenuated the phosphorylation of FOXO-1, activation of BIM, and abrogated capsaicin-induced apoptosis. Moreover, silencing FOXO1 by siRNA blocked capsaicin-mediated activation of BIM and apoptosis, whereas overexpression of FOXO-1 augmented its effects. Silencing Bim drastically reduced capsaicin-mediated cleavage of caspase-3 and PARP, indicating the role of BIM in apoptosis. Oral administration of 5 mg/kg capsaicin substantially suppressed the growth of BxPC-3 tumor xenografts in athymic nude mice. Tumors from capsaicin-treated mice showed an increase in the phosphorylation of JNK, FOXO-1, BIM, and levels of CBP, cleavage of caspase-3, PARP, and decreased SirT-1 expression. Taken together, our results suggest that capsaicin activated JNK and FOXO-1, leading to the acetylation of FOXO-1 through CBP and SirT-1. Acetylated FOXO1 induced apoptosis in pancreatic cancer cells through BIM activation.
authors.affiliation: Corresponding Author: Sanjay K. Srivastava, Department of Biomedical Sciences, Suite 1103, Texas Tech University Health Sciences Center, 1406 Coulter Drive, Amarillo, TX 79106. sanjay.srivastava@ttuhsc.edu.
authors.forename: Kartick C
authors.initials: KC
authors.lastname: Pramanik
authors.forename: Neel M
authors.initials: NM
authors.lastname: Fofaria
authors.forename: Parul
authors.initials: P
authors.lastname: Gupta
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Srivastava
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D050882:CREB-Binding Protein / Q000235:genetics*; D002211:Capsaicin / Q000008:administration & dosage; D045744:Cell Line, Tumor; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000235:genetics; D051379:Mice; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D056564:Sirtuin 1 / Q000235:genetics
chemical_list: C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D017382:Reactive Oxygen Species; D050882:CREB-Binding Protein; D048670:MAP Kinase Kinase 4; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D002211:Capsaicin