title: Necrotic and apoptotic features of cell death in response to Foscan photosensitization of HT29 monolayer and multicell spheroids.
abstract: Photodynamic therapy (PDT) is an approved anticancer treatment modality that eliminates unwanted cells by the photochemical generation of reactive oxygen species following absorption of visible light by a photosensitizer, which is selectively taken up by tumor cells. Present study reports the modalities of cell death after photosensitization of human adenocarcinoma HT29 monolayer and spheroid cells with a second generation photosensitizer Foscan. Kinetics of apoptosis and necrosis after Foscan-PDT in monolayer cells determined by flow cytometry using labeling of cleaved poly(ADP-ribose) polymerase (PARP) and staining with propidium iodide (PI) demonstrated that Foscan was not a strong inducer of apoptosis and necrosis was a prevailing mode of cell death. Cytochrome c release (cyt c) and mitochondrial membrane potential (Deltapsim) addressed by flow cytometry technique at different time points post-Foscan-PDT demonstrated that cell photoinactivation was governed by these mitochondrial events. Foscan-loaded HT29 multicell spheroids, subjected to irradiation with different fluence rates and equivalent light doses, displayed much better tumoricidal activity at the lowest fluence rate used. Apoptosis, measured by caspase-3 activation was evidenced only in spheroids irradiated with the lowest fluence rate and moderate fluence inducing 65% of cell death. Application of higher fluence rates for the same level of photocytotoxicity did not result in caspase-3 activation. The observation of the fluence rate-dependent modulation of caspase-3 activity in spheroids offers the possibility of regulating the mechanism of direct cell photodamage and could be of great potential in the clinical context.
authors.affiliation: Centre Alexis Vautrin, CRAN CNRS UMR 7039, 54511 Vandoeuvre les Nancy, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Marchal
authors.forename: Anas
authors.initials: A
authors.lastname: Fadloun
authors.forename: Estelle
authors.initials: E
authors.lastname: Maugain
authors.forename: Marie-Ange
authors.initials: MA
authors.lastname: D'Hallewin
authors.forename: François
authors.initials: F
authors.lastname: Guillemin
authors.forename: Lina
authors.initials: L
authors.lastname: Bezdetnaya
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000032:analysis / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005434:Flow Cytometry; D019073:HT29 Cells; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008652:Mesoporphyrins / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009336:Necrosis / Q000473:pathology; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D018874:Spheroids, Cellular / Q000187:drug effects*
chemical_list: D008652:Mesoporphyrins; D017319:Photosensitizing Agents; D045304:Cytochromes c; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C072269:temoporfin