Ali S M, Chee S K, Yuen G Y, Olivo M
Department of Medical Sciences, National Cancer Centre, 11 Hospital Drive, Singapore 16910, Singapore.
J Photochem Photobiol B. 2001 Dec 1;65(1):59-73. doi: 10.1016/s1011-1344(01)00252-4.
Potent photosensitizers hypocrellin A (HA), hypocrellin B (HB) and hypericin (HY) are lipid-soluble perylquinone derivatives of the genus Hypericum and have a strong photodynamic effect on tumors and viruses. However, the mechanisms of tumor cell death induced by HA, HB and HY are still unclear. Moreover, no reports have mentioned cell apoptosis induced by HA, HB and HY in human nasopharyngeal carcinoma (NPC) and other mucosal cells. In this study, we attempt to clarify the photodynamic effects of HA, HB and HY compounds in poorly differentiated (CNE2) and moderately differentiated (TW0-1) human NPC cells as well as human mucosal colon and bladder cells. Using these cell lines we investigated few hallmarks of apoptotic commitments in a drug dose dependent manner. Tumor cells photo-activated with HA, HB and HY showed cell size shrinkage and an increase in the sub-diploid DNA content. A loss of membrane phospholipid asymmetry associated with apoptosis was induced by all tumor cell lines as evidenced by the externalization of phosphatidylserine. Under apoptotic conditions, Western blot analysis of poly(ADP-ribose) polymerase, a caspases substrate, showed the classical cleavage pattern (116 to 85 kDa) associated with apoptosis in HA, HB and HY-treated cell lysates. In addition, 85 kDa cleaved product was blocked by the tetrapepdide caspase inhibitors such as DEVD-CHO or z-VAD-fmk. Both inhibitors protect tumor cells from apoptosis. These results demonstrate that tumor cell death induced by HA, HB and HY is mediated by caspase proteases. This study also identifies HB as a more potent and promising photosensitizer for the treatment of mucosal cancer cells.
强效光敏剂金丝桃素A（HA）、金丝桃素B（HB）和金丝桃素（HY）是金丝桃属的脂溶性苝醌衍生物，对肿瘤和病毒具有强烈的光动力效应。然而，HA、HB和HY诱导肿瘤细胞死亡的机制仍不清楚。此外，尚无报道提及HA、HB和HY在人鼻咽癌（NPC）及其他黏膜细胞中诱导的细胞凋亡情况。在本研究中，我们试图阐明HA、HB和HY化合物对低分化（CNE2）和中分化（TW0-1）人NPC细胞以及人黏膜结肠和膀胱细胞的光动力效应。利用这些细胞系，我们以药物剂量依赖的方式研究了凋亡相关的几个特征。用HA、HB和HY光激活的肿瘤细胞显示细胞体积缩小以及亚二倍体DNA含量增加。所有肿瘤细胞系均诱导了与凋亡相关的膜磷脂不对称性丧失，这通过磷脂酰丝氨酸的外化得以证明。在凋亡条件下，对凋亡蛋白酶底物聚（ADP-核糖）聚合酶进行蛋白质印迹分析，结果显示在HA、HB和HY处理的细胞裂解物中出现了与凋亡相关的经典切割模式（116 kDa至85 kDa）。此外，85 kDa的切割产物被四肽凋亡蛋白酶抑制剂如DEVD-CHO或z-VAD-fmk阻断。这两种抑制剂均可保护肿瘤细胞免于凋亡。这些结果表明，HA、HB和HY诱导的肿瘤细胞死亡是由凋亡蛋白酶介导的。本研究还确定HB是一种更有效且有前景的用于治疗黏膜癌细胞的光敏剂。
