title: D,L-Sulforaphane-induced cell death in human prostate cancer cells is regulated by inhibitor of apoptosis family proteins and Apaf-1.
abstract: D,L-Sulforaphane (SFN), a synthetic analogue of cruciferous vegetable-derived isomer l-SFN, suppresses proliferation of cancer cells by causing apoptosis but the mechanism of cell death is not fully understood. We used LNCaP (wild-type p53) and PC-3 (p53 deficient) human prostate cancer cells to gain further insights into the mechanism of SFN-induced apoptosis. The LNCaP cell line was relatively more sensitive to SFN-induced apoptosis compared with PC-3. The SFN treatment caused stabilization of p53 protein in LNCaP cells, but SFN-mediated apoptosis was not attenuated by knockdown of p53 protein. Instead, the differential sensitivity of these cells to SFN-induced apoptosis correlated with difference in kinetics of Bax conformational change. Ectopic expression of Bcl-2 failed to confer protection against SFN-induced cell death in LNCaP cells. Treatment of PC-3 cells with SFN resulted in a marked decrease in the levels of inhibitor of apoptosis (IAP) family proteins (cIAP1, cIAP2 and XIAP), which was accompanied by inhibition of nuclear translocation of p65-nuclear factor kappaB (NFkappaB). The effect of SFN on levels of IAP family proteins as well as transcriptional activity of NFkappaB was biphasic in LNCaP cells. The SFN-treated LNCaP and PC-3 cells exhibited a marked increase in protein level of Apaf-1, which was accompanied by an increase in transcriptional activity of E2F1. The SFN-induced apoptosis in both cell lines was significantly attenuated by Apaf-1 protein knockdown. In conclusion, the present study reveals a complex signaling mechanism involving Bax activation, downregulation of IAP family proteins and Apaf-1 induction in regulation of SFN-induced cell death.
authors.affiliation: Department of Pharmacology, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Sunga
authors.initials: S
authors.lastname: Choi
authors.forename: Karen L
authors.initials: KL
authors.lastname: Lew
authors.forename: Hui
authors.initials: H
authors.lastname: Xiao
authors.forename: Anna
authors.initials: A
authors.lastname: Herman-Antosiewicz
authors.forename: Dong
authors.initials: D
authors.lastname: Xiao
authors.forename: Charles K
authors.initials: CK
authors.lastname: Brown
authors.forename: Shivendra V
authors.initials: SV
authors.lastname: Singh
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053477:Apoptotic Protease-Activating Factor 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2; D050687:E2F1 Transcription Factor / Q000378:metabolism; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D017879:Isothiocyanates; D007700:Kinetics; D008297:Male; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000737:chemistry / Q000378:metabolism
chemical_list: D016588:Anticarcinogenic Agents; D053477:Apoptotic Protease-Activating Factor 1; C494826:BAX protein, human; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D051034:Inhibitor of Apoptosis Proteins; D017879:Isothiocyanates; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D013454:Sulfoxides; D013861:Thiocyanates; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D051028:bcl-2-Associated X Protein; C494833:BIRC2 protein, human; C494832:BIRC3 protein, human; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D044767:Ubiquitin-Protein Ligases; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; D020169:Caspases; C016766:sulforaphane