The development of drug resistance is a major problem which often occurs during anticancer chemotherapies. Photodynamic therapy (PDT) has been studied as an alternative treatment modality for drug-resistant tumors, however the question of resistance to PDT and potential cross-resistance with chemotherapy has yet to be fully answered. To investigate the mechanism of resistance to PDT, we developed an in vitro experimental model system in a mouse mammary carcinoma cell line 4T1. We used two ethylene glycol derivatives of tetraphenylporphyrin, and tetraphenylchlorin derivative, temoporfin, as photosensitizers (PS). PDT-resistant clones were obtained by exposure to a set concentration of PS followed by irradiation with increasing light doses. PDT resistance to soluble glycol porphyrins was mediated mainly by increased drug efflux through ABCB1 (P-glycoprotein) as we demonstrated by specific ABCB1 knockdown experiments, which in turn rescued the sensitivity of resistant cells to PDT. In contrast, resistance raised to temoporfin, which is generally more lipophilic than glycol porphyrins, elicited mechanism based on sequestration of the drug to lysosomes. The resistance that is acquired from a particular PS could be overcome by using a different PS, which is not susceptible to the same mechanism(s) of resistance. Elucidation of the underlying mechanisms in various types of resistance might facilitate improvements in PDT treatment design.

• MeSH
• chemorezistence genetika   MeSH
• ethylenglykoly aplikace a dávkování   chemie   MeSH
• fotochemoterapie MeSH
• fotosenzibilizující látky aplikace a dávkování   chemie   MeSH
• genový knockdown MeSH
• glykoly chemie   MeSH
• lidé MeSH
• mesoporfyriny aplikace a dávkování   chemie   MeSH
• MFC-7 buňky MeSH
• myši MeSH
• nádory mléčné žlázy u zvířat farmakoterapie   genetika   patologie   MeSH
• P-glykoprotein genetika   MeSH
• paclitaxel škodlivé účinky   MeSH
• porfyriny aplikace a dávkování   chemie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ethylenglykoly MeSH
• fotosenzibilizující látky MeSH
• glykoly MeSH
• mesoporfyriny MeSH
• P-glykoprotein MeSH
• paclitaxel MeSH
• porfyriny MeSH
• temoporfin MeSH Prohlížeč

We have analyzed the molecular mechanisms of photoinduced cell death using porphyrins with similar structure differing only in the position of the ethylene glycol (EG) chain on the phenyl ring. Meta- and para-positioned EG chains targeted porphyrins to different subcellular compartments. After photoactivation, both types of derivatives induced death of tumor cells via reactive oxygen species (ROS). Para derivatives pTPP(EG)4 and pTPPF(EG)4 primarily accumulated in lysosomes activated the p38 MAP kinase cascade, which in turn induced the mitochondrial apoptotic pathway. In contrast, meta porphyrin derivative mTPP(EG)4 localized in the endoplasmic reticulum (ER) induced dramatic changes in Ca(2+) homeostasis manifested by Ca(2+) rise in the cytoplasm, activation of calpains and stress caspase-12 or caspase-4. ER stress developed into unfolded protein response. Immediately after irradiation the PERK pathway was activated through phosphorylation of PERK, eIF2α and induction of transcription factors ATF4 and CHOP, which regulate stress response genes. PERK knockdown and PERK deficiency protected cells against mTPP(EG)4-mediated apoptosis, confirming the causative role of the PERK pathway.

• MeSH
• apoptóza účinky léků   účinky záření   MeSH
• ethylenglykol chemie   MeSH
• fotochemoterapie * MeSH
• genový knockdown MeSH
• homeostáza účinky léků   účinky záření   MeSH
• iniciační kaspasy metabolismus   MeSH
• kaspasa 2 metabolismus   MeSH
• kinasa eIF-2 nedostatek   genetika   metabolismus   MeSH
• lidé MeSH
• mitogenem aktivované proteinkinasy p38 metabolismus   MeSH
• nádorové buněčné linie MeSH
• porfyriny chemie   farmakologie   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• signální transdukce účinky léků   účinky záření   MeSH
• stres endoplazmatického retikula účinky léků   účinky záření   MeSH
• subcelulární frakce účinky léků   metabolismus   účinky záření   MeSH
• vápník metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CASP4 protein, human MeSH Prohlížeč
• ethylenglykol MeSH
• iniciační kaspasy MeSH
• kaspasa 2 MeSH
• kinasa eIF-2 MeSH
• mitogenem aktivované proteinkinasy p38 MeSH
• PERK kinase MeSH Prohlížeč
• porfyriny MeSH
• reaktivní formy kyslíku MeSH
• vápník MeSH