title: Enhanced aggressiveness of bystander cells in an anti-tumor photodynamic therapy model: Role of nitric oxide produced by targeted cells.
abstract: The bystander effects of anti-cancer ionizing radiation have been widely studied, but far less is known about such effects in the case of non-ionizing photodynamic therapy (PDT). In the present study, we tested the hypothesis that photodynamically-stressed prostate cancer PC3 cells can elicit nitric oxide (NO)-mediated pro-growth/migration responses in non-stressed bystander cells. A novel approach was used whereby both cell populations existed on a culture dish, but made no physical contact with one other. Visible light irradiation of target cells sensitized with 5-aminolevulinic acid-induced protoporphyrin IX resulted in a striking upregulation of inducible nitric oxide synthase (iNOS) along with NO, the level of which increased after irradiation. Slower and less pronounced iNOS/NO upregulation was also observed in bystander cells. Activation of transcription factor NF-κB was implicated in iNOS induction in both targeted and bystander cells. Like surviving targeted cells, bystanders exhibited a significant increase in growth and migration rate, both responses being strongly attenuated by an iNOS inhibitor (1400W), a NO scavenger (cPTIO), or iNOS knockdown. Incubating bystander cells with conditioned medium from targeted cells failed to stimulate growth/migration, ruling out involvement of relatively long-lived stimulants. The following post-irradiation changes in pro-survival/pro-growth proteins were observed in bystander cells: upregulation of COX-2 and activation of protein kinases Akt and ERK1/2, NO again playing a key role. This is the first reported evidence for NO-enhanced bystander aggressiveness in the context of PDT. In the clinical setting, such effects could be averted through pharmacologic use of iNOS inhibitors as PDT adjuvants.
authors.affiliation: Department of Biophysics, Jagiellonian University, Krakow, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Bazak
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226-3548, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Fahey
authors.affiliation: Department of Biophysics, Jagiellonian University, Krakow, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Wawak
authors.affiliation: Department of Biophysics, Jagiellonian University, Krakow, Poland; Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226-3548, USA. Electronic address: witekkor@mcw.edu.
authors.forename: Witold
authors.initials: W
authors.lastname: Korytowski
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226-3548, USA. Electronic address: agirotti@mcw.edu.
authors.forename: Albert W
authors.initials: AW
authors.lastname: Girotti
mesh_terms: D000578:Amidines / Q000008:administration & dosage; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001565:Benzoates / Q000008:administration & dosage; D001596:Benzylamines / Q000008:administration & dosage; D024201:Bystander Effect / Q000528:radiation effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D055785:Gene Knockdown Techniques; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage; D008027:Light; D008297:Male; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics* / Q000378:metabolism; D010778:Photochemotherapy; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology; D011524:Protoporphyrins / Q000235:genetics / Q000378:metabolism
chemical_list: D000578:Amidines; D001565:Benzoates; D001596:Benzylamines; D004791:Enzyme Inhibitors; D007093:Imidazoles; C104820:N-(3-(aminomethyl)benzyl)acetamidine; D016328:NF-kappa B; D011524:Protoporphyrins; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009569:Nitric Oxide; C028025:protoporphyrin IX; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human
keywords: Bystander effects; Inducible NO synthase; Nitric oxide; Photodynamic therapy