title: Cyclooxygenase-2 expression induced by photofrin photodynamic therapy involves the p38 MAPK pathway.
abstract: Photodynamic therapy (PDT), using the porphyrin photosensitizer Photofrin (PH), is approved for the clinical treatment of solid tumors. In addition to the direct cytotoxic responses of PH-PDT-mediated oxidative stress, this procedure also induces expression of angiogenic and prosurvival molecules including cyclooxygenase-2 (COX-2). In vivo treatment efficacy is improved when PH-PDT is combined with inhibitors of COX-2. In the current study we evaluated the signaling pathways involved with PH-PDT-mediated COX-2 expression in a mouse fibrosarcoma cell line. COX-2 promoter reporter constructs with mutated transcription elements documented that the nuclear factor kappa B (NFkappaB) element, cyclic-AMP response element 2 (CRE-2), CCAAT/enhancer binding protein (C/EBP) element and activator binding protein-1 (AP-1) element were responsive to PH-PDT. Transcription factor binding assays demonstrated that nuclear protein binding to NFkappaB, CRE-2, c-fos and c-jun elements were elevated following PH-PDT. Kinase phosphorylation upstream of COX-2 expression was also examined following PH-PDT. Stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and c-Jun were phosphorylated following PH-PDT but the SAPK/JNK inhibitor SP600125 failed to attenuate COX-2 expression. In contrast, p38 mitogen-activated protein kinase (MAPK), which activates CRE-2 binding, was phosphorylated following PH-PDT and inhibitors of p38 MAPK, SB203580 and SB202190, decreased PH-PDT-induced COX-2 expression at both the mRNA and protein levels. Extracellular signal-regulated kinase (ERK1/2) phosphorylation, which also increases CRE-2 binding activity, was initially high in untreated cells, decreased immediately following PH-PDT and then rapidly increased. MEK1/2 is immediately upstream of ERK1/2 and the MEK1 inhibitor PD98059 failed to attenuate COX-2 expression while the MEK1/2 inhibitor U0126 induced a slight decrease in COX-2 expression. The NFkappaB inhibitor SN50 failed to reduce COX-2 expression. These results demonstrate that multiple protein kinase cascades can be activated by oxidative stress and that the p38 MAPK signaling pathway and CRE-2 binding are involved in COX-2 expression following PH-PDT.
authors.affiliation: Saban Research Institute, Childrens Hospital Los Angeles, Los Angeles, CA, USA.
authors.forename: Marian
authors.initials: M
authors.lastname: Luna
authors.forename: Sam
authors.initials: S
authors.lastname: Wong
authors.forename: Angela
authors.initials: A
authors.lastname: Ferrario
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Gomer
mesh_terms: D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D017323:Dihematoporphyrin Ether / Q000494:pharmacology*; D051379:Mice; D010778:Photochemotherapy; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D017323:Dihematoporphyrin Ether; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases