Necrotic and apoptotic features of cell death in response to Foscan photosensitization of HT29 monolayer and multicell spheroids.
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.
Marchal
Sophie
S
Centre Alexis Vautrin, CRAN CNRS UMR 7039, 54511 Vandoeuvre les Nancy, France.
Fadloun
Anas
A
Maugain
Estelle
E
D'Hallewin
Marie-Ange
MA
Guillemin
François
F
Bezdetnaya
Lina
L
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*
D008652:Mesoporphyrins; D017319:Photosensitizing Agents; D045304:Cytochromes c; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C072269:temoporfin