Zhang Xuexian, Malejka-Giganti Danuta
Veterans Affairs Medical Center (151), Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, USA.
Anticancer Res. 2003 May-Jun;23(3B):2473-9.
Induction of apoptosis is an approach to suppress carcinogenesis. The effects of a 12-week treatment of female Sprague-Dawley rats with indole-3-carbinol (I3C), beta-naphthoflavone or vehicle (40% ethanol in corn oil), by oral gavages starting 3 weeks after initiation of mammary tumorigenesis with 7,12-dimethylbenz[alpha]anthracene, on apoptotic activities in the mammary adenocarcinomas were examined. Apoptotic cells in tumor sections were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and quantitated by light microscopy and an Image-Plus Program. Activities of caspase-3, caspase-8 and caspase-9 were determined by colorimetric assays using the specific substrate and total tumor protein. There were no significant treatment-related effects on the numbers of apoptotic cells and caspase activities in the mammary adenocarcinomas. Likewise, protein expression levels of Bcl-2 and Bax genes in these tumors, determined by Western blot analysis, showed no treatment-related stimulation of apoptotic process. In the absence of tumorigenesis, the activities of caspase-3, caspase-8 and caspase-9 were increased up to approximately 3.6-fold in the mammary gland of rats treated with I3C at 5 or 25 mg/kg of body weight for 4 or 10 days. The I3C-effected induction of caspase-3 activity in the mammary gland was further confirmed by the cleavage of poly (ADP-ribose) polymerase. Treatment of rats with 3,3'-diindolylmethane, a major product of I3C in vivo, at the dose levels equimolar to those of I3C above, did not increase the caspase activities in the mammary gland. Thus, this I3C dimer does not seem to account for the increases of apoptotic activities in the mammary gland observed with I3C. The results suggest that increase of apoptosis in the mammary gland induced by I3C before initiation of tumorigenesis may contribute to suppression of tumor development.
诱导细胞凋亡是一种抑制肿瘤发生的方法。在用7,12-二甲基苯并[a]蒽启动乳腺肿瘤发生3周后，通过口服灌胃对雌性斯普拉格-道利大鼠进行为期12周的吲哚-3-甲醇（I3C）、β-萘黄酮或赋形剂（玉米油中的40%乙醇）处理，检测其对乳腺腺癌凋亡活性的影响。通过末端脱氧核苷酸转移酶介导的dUTP缺口末端标记检测肿瘤切片中的凋亡细胞，并通过光学显微镜和Image-Plus程序进行定量。使用特异性底物和总肿瘤蛋白通过比色法测定半胱天冬酶-3、半胱天冬酶-8和半胱天冬酶-9的活性。乳腺腺癌中凋亡细胞数量和半胱天冬酶活性未发现与处理相关的显著影响。同样，通过蛋白质印迹分析确定的这些肿瘤中Bcl-2和Bax基因的蛋白质表达水平，未显示与处理相关的凋亡过程刺激。在无肿瘤发生的情况下，体重5或25 mg/kg的I3C处理4或10天的大鼠乳腺中，半胱天冬酶-3、半胱天冬酶-8和半胱天冬酶-9的活性增加至约3.6倍。聚（ADP-核糖）聚合酶的裂解进一步证实了I3C对乳腺中半胱天冬酶-3活性的诱导作用。用I3C体内主要产物3,3'-二吲哚基甲烷以与上述I3C等摩尔剂量处理大鼠，未增加乳腺中的半胱天冬酶活性。因此，这种I3C二聚体似乎不能解释I3C观察到乳腺中凋亡活性的增加。结果表明，I3C在肿瘤发生起始前诱导乳腺细胞凋亡增加可能有助于抑制肿瘤发展。
