title: Accelerated migration and invasion of prostate cancer cells after a photodynamic therapy-like challenge: Role of nitric oxide.
abstract: Employing an in vitro model for 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT), we recently reported that human prostate cancer PC3 cells rapidly and persistently overexpressed inducible nitric oxide synthase (iNOS) and nitric oxide (NO) after a moderate ALA/light challenge. The upregulated iNOS/NO was shown to play a key role in cell resistance to apoptotic photokilling and also in the dramatic growth spurt observed in surviving cells. In the present study, we found that PC3 cells surviving an ALA/light insult not only proliferated faster than non-stressed controls, but migrated and invaded faster as well, these effects being abrogated by an iNOS inhibitor or NO scavenger. Photostressed prostate DU145 cells exhibited similar behavior. Using in-gel zymography, we showed that PC3 extracellular matrix metalloproteinase-9 (MMP-9) was strongly activated 24 h after ALA/light treatment and that MMP-9 inhibitor TIMP-1 was downregulated, consistent with MMP-9 involvement in enhanced invasiveness. We also observed a photostress-induced upregulation of α6 and β1 integrins, implying their involvement as well. The MMP-9, TIMP-1, and integrin effects were strongly attenuated by iNOS inhibition, confirming NO's role in photostress-enhanced migration/invasion. This study reveals novel, potentially tumor-promoting, side-effects of prostate cancer PDT which may be averted through use of iNOS inhibitors as PDT adjuvants.
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 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: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects*; D006801:Humans; D008297:Male; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011524:Protoporphyrins / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000528:radiation effects
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; D009569:Nitric Oxide; C028025:protoporphyrin IX; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II
keywords: Cell migration/invasion; Nitric oxide; Photodynamic therapy; Prostate cancer