Boone C W, Stoner G D, Bacus J V, Kagan V, Morse M A, Kelloff G J, Bacus J W
Chemopreventive Agent Development Research Group, Division of Cancer Prevention, National Cancer Institute, Bethesda, Maryland 20892-7322, USA.
Cancer Epidemiol Biomarkers Prev. 2000 Nov;9(11):1149-54.
The objective of the study was to compare three methods of monitoring the inhibition by dietary theaflavins of N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal intraepithelial neoplasia: the mean tile grade, measured by computer-assisted quantitative image tile analysis; tumor multiplicity; and mean tumor size. A "tile" is defined as a small portion of a microscopic image at x 40, 87 x 292 microm in size. The computer divided the image of esophageal intraepithelial neoplasia into a grid of contiguous tiles and measured four tissue features within each tile based on cytonuclear and tissue architectural changes used by pathologists to diagnose intraepithelial neoplasia. The tile grade is defined as the weighted sum of the four feature measurements within a tile, the weights being determined by Fisher linear discriminant analysis. The mean tile grade of 300 tiles is used to grade rat esophageal intraepithelial neoplasia. NMBA was given s.c., 0.5 mg/kg, three times a week for 5 weeks. Theaflavins were given in the drinking water at 360 ppm (low dose) and 1200 ppm (high dose) throughout the experiment. In a given set of four groups of rats, one group received theaflavins alone, one NMBA alone, one NMBA plus low-dose theaflavins, and one NMBA plus high-dose theaflavins. One set of four groups, four rats/group, was sacrificed at the 15th week and another at the 20th week after starting NMBA; a final set with 15 rats/group was sacrificed at 25 weeks. At the 15th and 20th weeks, the mean tumor grade was the only variable that responded significantly (P < 0.01) to the low dose of dietary theaflavins. In fact, tumor multiplicity and mean tumor size sometimes showed enhancement at these doses. At the 25th week, when there were 15 instead of 4 rats/group, the mean tile grade, tumor multiplicity, and mean tumor size were all significantly (P < 0.01) decreased by both low and high doses of theaflavins. The mean tile grade is a more sensitive and reproducible variable than tumor multiplicity and mean tumor size in detecting the chemopreventive effects of theaflavins on intraepithelial neoplasia in the rat esophagus. This suggests that the mean tile grade may be a useful intermediate end point for use in human chemoprevention trials.
本研究的目的是比较三种监测膳食茶黄素对N-亚硝基甲基苄胺（NMBA）诱导的大鼠食管上皮内瘤变抑制作用的方法：通过计算机辅助定量图像切片分析测量的平均切片等级、肿瘤多发性和平均肿瘤大小。“切片”定义为40倍显微镜图像的一小部分，大小为87×292微米。计算机将食管上皮内瘤变图像划分为连续的切片网格，并根据病理学家用于诊断上皮内瘤变的细胞核和组织结构变化，在每个切片中测量四个组织特征。切片等级定义为一个切片内四个特征测量值的加权和，权重由Fisher线性判别分析确定。300个切片的平均切片等级用于对大鼠食管上皮内瘤变进行分级。NMBA皮下注射，剂量为0.5mg/kg，每周三次，共5周。在整个实验过程中，茶黄素以360ppm（低剂量）和1200ppm（高剂量）添加到饮用水中。在给定的四组大鼠中，一组单独接受茶黄素，一组单独接受NMBA，一组接受NMBA加低剂量茶黄素，一组接受NMBA加高剂量茶黄素。在开始给予NMBA后的第15周处死一组四组大鼠，每组4只；另一组在第20周处死；最后一组每组15只大鼠在第25周处死。在第15周和第20周，平均肿瘤等级是唯一对低剂量膳食茶黄素产生显著反应（P<0.01）的变量。事实上，在这些剂量下，肿瘤多发性和平均肿瘤大小有时会增加。在第25周，当每组有15只而非4只大鼠时，低剂量和高剂量的茶黄素均使平均切片等级、肿瘤多发性和平均肿瘤大小显著降低（P<0.01）。在检测茶黄素对大鼠食管上皮内瘤变的化学预防作用方面，平均切片等级比肿瘤多发性和平均肿瘤大小更敏感且可重复。这表明平均切片等级可能是用于人类化学预防试验的有用中间终点。
