Nakamura Y, Gindhart T D, Winterstein D, Tomita I, Seed J L, Colburn N H
Laboratory of Viral Carcinogenesis, National Cancer Institute, Frederick Cancer Research Facility, MD 21701-1013.
Carcinogenesis. 1988 Feb;9(2):203-7. doi: 10.1093/carcin/9.2.203.
Evidence has been obtained that implicates the generation of reactive oxygen species as an early and critical event in the promotion of neoplastic transformation in mouse JB6 cells. The time courses for specific inhibition by CuZn-superoxide dismutase (CuZn-SOD) of the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of neoplastic transformation in JB6 cells and for changes in antioxidant enzyme activities associated with TPA-exposure were examined. The antipromoting effect of CuZn-SOD was found to be critically dependent on the time of addition of CuZn-SOD relative to the start of a 14-day exposure of cells to TPA. Treatment of JB6 P+ Clone 22 and Clone 41 cells with CuZn-SOD for 18 h before, simultaneously with or up to 1 h after exposure to TPA, all inhibited promotion of transformation maximally. Delay of addition of CuZn-SOD by 2 h or more after the start of TPA treatment resulted in a marked decrease in the promotion inhibitory effect. CuZn-SOD added 24 or 48 h after TPA had no effect on promotion of transformation. Exposure of JB6 cells to 0.2- (superoxide anion radical) generated exogenously by the aerobic xanthine oxidase reaction resulted in promotion of neoplastic transformation that was prevented by concurrent addition of CuZn-SOD. Taken together these studies provide evidence that increased superoxide anion generation within the first 2 h following TPA exposure is an essential event in promotion of transformation in JB6 cells. Upon TPA exposure, JB6 Clone 41 cells exhibited time-specific activity changes in the cellular SOD, glutathione peroxidase (GSH-Px), and catalase. SOD and GSH-Px activities were reduced to 54% and 26% respectively of basal levels within 2 h of TPA treatment. GSH-Px activity recovered to basal levels within 4 h and CuZn-SOD within 48 h. Catalase activity was maximally reduced to 50% of basal within 1 h after TPA treatment and rebounded to greater than basal levels within 4 h. It is postulated that a c-kinase-dependent event induces rapid elevation of superoxide anion following TPA exposure and that this leads to reduced activity of antioxidant enzymes. Since antipromotion by exogenous CuZn-SOD is effective only during the first 2 h following TPA exposure, this suggests that the promotion-relevant 0.2- elevation is transient.
已有证据表明，活性氧的产生是小鼠JB6细胞肿瘤转化促进过程中的一个早期关键事件。研究了铜锌超氧化物歧化酶（CuZn-SOD）对12-O-十四烷酰佛波醇-13-乙酸酯（TPA）诱导的JB6细胞肿瘤转化促进作用的特异性抑制的时间进程，以及与TPA暴露相关的抗氧化酶活性变化。发现CuZn-SOD的抗促进作用关键取决于相对于细胞开始暴露于TPA 14天的CuZn-SOD添加时间。在暴露于TPA之前、同时或暴露后1小时内，用CuZn-SOD处理JB6 P+克隆22和克隆41细胞18小时，均能最大程度地抑制转化促进作用。在TPA处理开始后延迟2小时或更长时间添加CuZn-SOD，导致促进抑制作用显著降低。在TPA处理后24或48小时添加CuZn-SOD对转化促进作用无影响。通过需氧黄嘌呤氧化酶反应外源性产生的0.2-（超氧阴离子自由基）暴露于JB6细胞导致肿瘤转化促进，同时添加CuZn-SOD可阻止这种促进作用。这些研究共同提供了证据，表明在TPA暴露后的前2小时内超氧阴离子产生增加是JB6细胞转化促进中的一个必要事件。暴露于TPA后，JB6克隆41细胞在细胞超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）和过氧化氢酶中表现出时间特异性活性变化。在TPA处理后2小时内，SOD和GSH-Px活性分别降至基础水平的54%和26%。GSH-Px活性在4小时内恢复到基础水平，CuZn-SOD在48小时内恢复。过氧化氢酶活性在TPA处理后1小时内最大程度地降至基础水平的50%，并在4小时内反弹至高于基础水平。据推测，一个依赖c激酶的事件在TPA暴露后诱导超氧阴离子迅速升高，这导致抗氧化酶活性降低。由于外源性CuZn-SOD的抗促进作用仅在TPA暴露后的前2小时内有效，这表明与促进相关的0.2-升高是短暂的。
