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Mechanisms of Cytotoxicity in Human Ovarian Carcinoma Cells Exposed to Free Mce 6 or HPMA Copolymer–Mce 6 Conjugates ¶
Author(s) -
Tijerina Monica,
Kopec̆ková Pavla,
Kopec̆ek Jindŕich
Publication year - 2003
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2003)0770645mociho2.0.co2
Subject(s) - chemistry , cytotoxicity , linker , thioether , conjugate , fluorescein isothiocyanate , apoptosis , biophysics , biochemistry , stereochemistry , fluorescence , in vitro , biology , mathematical analysis , mathematics , physics , quantum mechanics , computer science , operating system
It is essential to understand cellular responses on photodynamic therapy (PDT) to design delivery systems that maximize cytotoxic effects coupled with minimal induction of side effects or protective mechanisms (or both). Here, we investigated mechanisms of toxicity in human ovarian carcinoma A2780 cells treated with structurally diverse N ‐(2‐hydroxypropyl)methacrylamide (HPMA) copolymer (P)–mesochlorin e 6 monoethylenediamine (Mce 6 ) conjugates that possessed differential subcellular accumulation or covalent attachments of photosensitizers (or both). Apoptosis and necrosis were observed after photoactivation, with increased apoptotic responses observed in cells exposed to conjugates possessing Mce 6 linkage via a lysosomally degradable tetrapeptide spacer (HPMA copolymer–Mce 6 conjugates containing Mce 6 bound via glycylphenylalanylleucylglycine [GFLG] linker [P‐GFLG‐Mce 6 ], HPMA copolymer–Mce 6 conjugates containing Mce 6 bound via a GFLG spacer and containing nuclear localization sequence, PKKKRKV 132 K(FITC)C [NLS(fluorescein‐5‐isothiocyanate [FITC])] bound via a thioether linkage [P‐NLS(FITC)‐GFLG‐Mce 6 ]). Furthermore, the induction of necrosis was more pronounced in cells exposed to conjugates containing both a nuclear localization sequence (NLS) and Mce 6 bound by a degradable linker (P‐NLS(FITC)‐GFLG‐Mce 6 ). Caspase‐independent mechanisms of cell death were identified in cells treated with nuclear‐targeted conjugates possessing Mce 6 attached using a nondegradable tether (HPMA copolymer–Mce 6 conjugates containing Mce 6 bound via a GG spacer and containing NLS(FITC) bound via a thioether linkage [P‐NLS(FITC)‐GG‐Mce 6 ]), whereas low levels of apoptosis and necrosis were detected in cells exposed to photoactivated nontargeted HPMA copolymer–Mce 6 conjugates containing Mce 6 coupled through a nondegradable spacer (HPMA copolymer–Mce 6 conjugates containing Mce 6 bound via GG linker [P‐GG‐Mce 6 ]). Variations in gene expression were observed in cells on PDT. Specifically, HSP70 expression was solely detected in cells treated with P‐GFLG‐Mce 6 , whereas the loss of detection of several genes were observed in cells treated with P‐NLS(FITC)‐GFLG‐Mce 6 . Variations in cellular responses on PDT using different HPMA copolymer–Mce 6 conjugates will prove useful in the design of optimal HPMA copolymer PDT delivery systems.