title: Regulation of p53 and suppression of apoptosis by the soluble guanylyl cyclase/cGMP pathway in human ovarian cancer cells.
abstract: Dysregulated apoptosis plays a critical role in the development of a number of aberrant cellular processes, including tumorigenesis and chemoresistance. However, the mechanisms that govern the normal apoptotic program are not completely understood. Soluble guanylyl cyclase (sGC) and cyclic guanosine monophosphate (cGMP) promote mammalian cell viability via an unknown mechanism and p53 status is a key determinant of cell fate in human ovarian cancer cells. Whether an interaction exists between these two determinants of cell fate is unknown. We hypothesized that basal sGC activity reduces p53 content and attenuates p53-dependent apoptosis in human ovarian cancer cells. Suppression of sGC activity with the specific inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) lowered cGMP content, and increased p53 protein content and induced apoptosis in three ovarian cancer cell lines, effects which were attenuated by the cGMP analog 8-Br-cGMP and by Atrial Natriuretic Factor, an activator of particulate guanylyl cyclase, which circumvent the inhibition of sGC. ODQ prolonged p53 half-life, induced phosphorylation of p53 on Ser15, and upregulated the p53-dependent gene products p21, murine double minute-2, and the proapoptotic, p53-responsive gene product Bax. ODQ activated caspase-3, and ODQ-induced apoptosis was inhibited by overexpression of X-linked inhibitor of apoptosis Protein. Pretreatment with the specific p53 inhibitor pifithrin or downregulation of p53 using a specific small inhibitory RNA significantly attenuated ODQ-induced apoptosis. Moreover, ODQ-induced upregulation of p21 and Bax and ODQ-induced apoptosis were significantly reduced in a p53 mutant cell line relative to the wild-type parental cell line. Thus, the current study establishes that basal sGC/cGMP activity regulates p53 protein stability, content, and function, possibly by altering p53 phosphorylation and stabilization, and promotes cell survival in part through regulation of caspase-3 and p53.
authors.affiliation: Reproductive Biology Unit and Division of Gynecologic Oncology, Department of Obstetrics & Gynecology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Fraser
authors.forename: S L
authors.initials: SL
authors.lastname: Chan
authors.forename: S S L
authors.initials: SS
authors.lastname: Chan
authors.forename: R R
authors.initials: RR
authors.lastname: Fiscus
authors.forename: B K
authors.initials: BK
authors.lastname: Tsang
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D052160:Benzothiazoles; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D009154:Mutation; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D010069:Oxadiazoles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D013844:Thiazoles / Q000494:pharmacology; D014050:Toluene / Q000031:analogs & derivatives / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D052160:Benzothiazoles; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D011810:Quinoxalines; D034741:RNA, Small Interfering; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; D051028:bcl-2-Associated X Protein; C016276:8-bromocyclic GMP; D014050:Toluene; D012694:Serine; D009320:Atrial Natriuretic Factor; C121565:pifithrin; D051736:Proto-Oncogene Proteins c-mdm2; D017869:Cyclic GMP-Dependent Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D006162:Guanylate Cyclase; D006152:Cyclic GMP