MacDonald I J, Morgan J, Bellnier D A, Paszkiewicz G M, Whitaker J E, Litchfield D J, Dougherty T J
Photodynamic Therapy Center, Roswell Park Cancer Institute, Buffalo, NY, USA.
Photochem Photobiol. 1999 Nov;70(5):789-97.
To determine if subcellular localization is important to photodynamic therapy (PDT) efficacy, an in vitro fluorescence microscopy study was conducted with a congeneric series of pyropheophorbide-a derivatives in human pharyngeal squamous cell carcinoma (FaDu) cells and murine radiation-induced fibrosarcoma (RIF) mutant cells. In the FaDu cells the octyl, decyl and dodecyl ether derivatives localized to the lysosomes at extracellular concentrations less than needed to produce a 50% cell kill (LD50). At extracellular concentrations equal or greater than the LD50 the compounds localized mainly to mitochondria. The propyl, pentyl, hexyl and heptyl ether derivatives localized mainly to the mitochondria at all concentrations studied. This suggested that mitochondria are a sensitive PDT target for these derivatives. Similar experiments were performed with two Photofrin-PDT resistant RIF cell lines, one of which was found to be resistant to hexyl ether derivative (C6) mediated-PDT and the other sensitive to C6-PDT relative to the parent line. At extracellular concentrations of C6 below the LD50 of each cell line, the mutants exhibited lysosomal localization. At concentrations above these values the patterns shifted to a mainly mitochondrial pattern. In these cell lines mitochondrial localization also correlated with PDT sensitivity. Localization to mitochondria or lysosomes appeared to be affected by the aggregation state of the congeners, all of which are highly aggregated in aqueous medium. Monomers apparently were the active fraction of these compounds because equalizing the extracellular monomer concentrations produced equivalent intracellular concentrations, photoxicity and localization patterns. Compounds that were mainly aggregates localized to the lysosomes where they were rendered less active. Mitochondria appear to be a sensitive target for pyropheophorbide-a-mediated photodamage, and the degree of aggregation seems to be a determinant of the localization site.
为了确定亚细胞定位对光动力疗法（PDT）疗效是否重要，我们进行了一项体外荧光显微镜研究，使用了一系列同类的焦脱镁叶绿酸-a衍生物，作用于人类咽鳞状细胞癌（FaDu）细胞和小鼠辐射诱导的纤维肉瘤（RIF）突变细胞。在FaDu细胞中，辛基、癸基和十二烷基醚衍生物在细胞外浓度低于产生50%细胞杀伤（LD50）所需浓度时定位于溶酶体。在细胞外浓度等于或高于LD50时，这些化合物主要定位于线粒体。丙基、戊基、己基和庚基醚衍生物在所有研究浓度下主要定位于线粒体。这表明线粒体是这些衍生物的一个敏感的PDT靶点。我们对两种对Photofrin-PDT耐药的RIF细胞系进行了类似实验，相对于亲本系，其中一种对己基醚衍生物（C6）介导的PDT耐药，另一种对C6-PDT敏感。在每个细胞系的细胞外C6浓度低于LD50时，突变体表现出溶酶体定位。在高于这些值的浓度下，定位模式转变为主要是线粒体模式。在这些细胞系中，线粒体定位也与PDT敏感性相关。定位于线粒体或溶酶体似乎受同类物聚集状态的影响，所有这些同类物在水性介质中高度聚集。单体显然是这些化合物的活性部分，因为使细胞外单体浓度相等会产生相等的细胞内浓度、光毒性和定位模式。主要为聚集体的化合物定位于溶酶体，在那里它们的活性降低。线粒体似乎是焦脱镁叶绿酸-a介导的光损伤的一个敏感靶点，聚集程度似乎是定位位点的一个决定因素。
