Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan.
Int J Radiat Oncol Biol Phys. 2010 Jul 15;77(4):1232-9. doi: 10.1016/j.ijrobp.2010.01.007.
Increasing the sensitivity of tumor cells to radiation is a major goal of radiotherapy. The present study investigated the radiosensitizing effects of andrographolide and examined the molecular mechanisms of andrographolide-mediated radiosensitization.
An H-ras-transformed rat kidney epithelial (RK3E) cell line was used to measure the radiosensitizing effects of andrographolide in clonogenic assays, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide assays, and a xenograft tumor growth model. The mechanism of andrographolide-sensitized cell death was analyzed using annexin V staining, caspase 3 activity assays, and terminal transferase uridyl nick end labeling assays. The roles of nuclear factor kappa B (NF-kappaB) and Akt in andrographolide-mediated sensitization were examined using reporter assays, electrophoretic mobility shift assays, and Western blotting.
Concurrent andrographolide treatment (10 microM, 3 h) sensitized Ras-transformed cells to radiation in vitro (sensitizer enhancement ratio, 1.73). Andrographolide plus radiation (one dose of 300 mg/kg peritumor andrographolide and one dose of 6 Gy radiation) resulted in significant tumor growth delay (27 +/- 2.5 days) compared with radiation alone (22 +/- 1.5 days; p <.05). Radiation induced apoptotic markers (e.g., caspase-3, membrane reversion, DNA fragmentation), and andrographolide treatment did not promote radiation-induced apoptosis. However, the protein level of activated Akt was significantly reduced by andrographolide. NF-kappaB activity was elevated in irradiated Ras-transformed cells, and andrographolide treatment significantly reduced radiation-induced NF-kappaB activity.
Andrographolide sensitized Ras-transformed cells to radiation both in vitro and in vivo. Andrographolide-mediated radiosensitization was associated with downregulation of Akt and NF-kappaB activity. These observations indicate that andrographolide is a novel radiosensitizing agent with potential application in cancer radiotherapy.
提高肿瘤细胞对放射治疗的敏感性是放射治疗的主要目标。本研究探讨了穿心莲内酯的放射增敏作用，并研究了穿心莲内酯介导的放射增敏的分子机制。
使用 H-ras 转化的大鼠肾上皮（RK3E）细胞系，通过集落形成试验、3-(4,5-二甲基-2-噻唑基)-2,5-二苯基-2H 四唑溴盐试验和异种移植肿瘤生长模型来测量穿心莲内酯的放射增敏作用。通过 Annexin V 染色、caspase 3 活性测定和末端转移酶尿嘧啶核苷酸末端标记测定分析穿心莲内酯增敏细胞死亡的机制。使用报告基因测定、电泳迁移率变动分析和 Western 印迹分析，研究核因子 kappa B（NF-kappaB）和 Akt 在穿心莲内酯介导的增敏中的作用。
同时给予穿心莲内酯（10 μM，3 小时）处理可使 Ras 转化细胞在体外对辐射敏感（增敏比为 1.73）。与单独放射治疗（22 ± 1.5 天；p <.05）相比，肿瘤周围给予穿心莲内酯（一次剂量 300mg/kg ，一次剂量 6Gy 辐射）加放射治疗可导致肿瘤生长明显延迟（27 ± 2.5 天）。放射诱导的凋亡标志物（例如，caspase-3、膜反转、DNA 片段化），而穿心莲内酯处理不会促进放射诱导的凋亡。然而，穿心莲内酯显著降低了激活的 Akt 的蛋白水平。NF-kappaB 活性在照射的 Ras 转化细胞中升高，穿心莲内酯处理显著降低了辐射诱导的 NF-kappaB 活性。
穿心莲内酯在体外和体内均可使 Ras 转化细胞对辐射敏感。穿心莲内酯介导的放射增敏与 Akt 和 NF-kappaB 活性的下调有关。这些观察结果表明，穿心莲内酯是一种新型的放射增敏剂，在癌症放射治疗中有潜在的应用。
