He J, Agarwal M L, Larkin H E, Friedman L R, Xue L Y, Oleinick N L
Division of Radiation Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4942, USA.
Photochem Photobiol. 1996 Nov;64(5):845-52. doi: 10.1111/j.1751-1097.1996.tb01845.x.
Photodynamic therapy (PDT) is an efficient inducer of apoptosis, an active form of cell death that can be inhibited by the BCL-2 oncoprotein. The ability of BCL-2 to modulate PDT-induced apoptosis and overall cell killing has been studied in a pair of Chinese hamster ovary cell lines that differ from one another by a transfected human BCL-2 gene in one of them (Bissonnette et al, Nature 359, 552-554, 1992). Cells were exposed to the phthalocyanine photosensitizer Pc 4 and various fluences of red light. Pc 4 uptake was identical in the two cell lines. The parental cells displayed a high incidence of apoptosis after PDT, whereas at each fluence there was a much lower incidence of apoptosis in the BCL-2-expressing cells. Apoptosis was monitored by (a) observation of 50 kbp and oligonucleosome-size DNA fragments by gel electrophoresis, (b) flow cytometry of cells labeled with fluorescently tagged dUTP by terminal deoxynucleotidyl transferase and (c) fluorescence microscopy of acridine orange-stained cells. The time course of apoptosis varied with the PDT dose, suggesting that only after moderately high doses (> 99% loss of clonogenicity) was there a relatively synchronous and rapid entry of many cells into apoptosis. At PDT doses reducing cell survival by 90 or 99%, significant increases in apoptotic cells were found in the population after 6-12 h. Clonogenic assays showed that BCL-2 protein inhibited not only apoptosis but overall cell killing as well, effecting a two-fold resistance at the 10% survival level. Thus, BCL-2-expressing cells may be relatively resistant to PDT.
光动力疗法（PDT）是一种有效的凋亡诱导剂，凋亡是一种可被BCL-2癌蛋白抑制的细胞死亡的活跃形式。在一对中国仓鼠卵巢细胞系中研究了BCL-2调节PDT诱导的凋亡及整体细胞杀伤的能力，其中一个细胞系转染了人BCL-2基因，二者存在差异（比索内特等人，《自然》359卷，552 - 554页，1992年）。将细胞暴露于酞菁光敏剂Pc 4及不同光通量的红光下。两种细胞系对Pc 4的摄取相同。亲本细胞在PDT后显示出高凋亡发生率，而在每个光通量下，表达BCL-2的细胞凋亡发生率要低得多。通过以下方法监测凋亡：（a）通过凝胶电泳观察50 kbp和寡核小体大小的DNA片段；（b）用末端脱氧核苷酸转移酶标记荧光dUTP的细胞进行流式细胞术检测；（c）对吖啶橙染色的细胞进行荧光显微镜观察。凋亡的时间进程随PDT剂量而变化，这表明只有在中等高剂量（> 99%克隆形成能力丧失）后，才有许多细胞相对同步且快速地进入凋亡。在使细胞存活率降低90%或99%的PDT剂量下，6 - 12小时后群体中凋亡细胞显著增加。克隆形成试验表明，BCL-2蛋白不仅抑制凋亡，还抑制整体细胞杀伤，在10%存活水平时产生两倍的抗性。因此，表达BCL-2的细胞可能对PDT相对耐药。
