Richmond R E, DeAngelo A B, Potter C L, Daniel F B
Northern Kentucky University, Department of Biological Sciences, Highland Heights 41076.
Carcinogenesis. 1991 Aug;12(8):1383-7. doi: 10.1093/carcin/12.8.1383.
Dichloroacetic acid (DCA) has recently been shown to increase significantly the incidence of hepatic adenomas (HAs) and hepatocarcinomas (HCs) in male B6C3F1 mice. Although little is known about the mechanism of DCA carcinogenesis, chronic ingestion of the compound in drinking water induces primarily hyperplastic nodules (HNs) prior to the appearance of HAs and HCs. Given the putative preneoplastic potential of the HNs, we undertook this study to determine the role of the HNs in the progression of DCA-induced hepatocarcinogenesis. This role was assessed by detecting the expression of five different tumor markers: p21 ras, p39 c-jun, phosphotyrosine, tumor-associated aldehyde dehydrogenase and alpha-fetoprotein, all known from previous studies to be expressed more often in neoplastic liver lesions than in normal liver. Tumor marker expression was detected by immunohistochemical methods using formalin-fixed, paraffin-embedded sections of normal B6C3F1 mouse liver, and DCA-induced HNs, HAs and HCs. The results demonstrated that, except for the c-jun marker, HNs expressed the markers significantly less often than either HAs or HCs. Equal expression of c-jun occurred in any of the three lesion types. Although these results could be used to argue that no relationship existed between HNs and later-appearing HAs and HCs, those HNs that were marker positive contained small nests of marker-positive hepatocytes among a field of normally appearing unstained hepatocytes. No similar nests of marker-positive cells were detected in any area of normal liver outside the HNs. Also very few altered hepatic foci (AF) were detected with these markers or with hematoxylin and eosin, or with histochemical stains for ATPase or glucose-6-phosphatase deficiencies. These results suggested that these nests within some HNs were areas of transformed, or neoplastic hepatocytes. Phenotypic heterogeneity analysis, in which the number of tumor markers co-expressed by any given lesion was examined, confirmed a significantly greater percentage of HAs and HCs expressing multiple markers than HNs. Those HNs that expressed multiple markers, however, expressed at the same frequency as HAs and HCs and the expression was confined to the same nests of cells. Taken together, these data suggest that these nests of marker-positive cells within the HNs were neoplastic and could develop into later-appearing HAs and/or HCs. The absence of marker expression in normal liver and limited expression in the few AF indicates that the HNs may be the only significant preneoplastic lesion in DCA-induced hepatocarcinogenesis.
最近研究表明，二氯乙酸（DCA）可显著增加雄性B6C3F1小鼠肝腺瘤（HA）和肝癌（HC）的发生率。尽管对DCA致癌机制知之甚少，但长期饮用含该化合物的水主要诱导增生性结节（HN），随后才出现HA和HC。鉴于HN具有假定的癌前潜能，我们开展本研究以确定HN在DCA诱导的肝癌发生发展中的作用。通过检测五种不同肿瘤标志物的表达来评估这一作用：p21 ras、p39 c-jun、磷酸酪氨酸、肿瘤相关醛脱氢酶和甲胎蛋白，以往研究表明，这些标志物在肿瘤性肝损伤中的表达频率高于正常肝脏。使用正常B6C3F1小鼠肝脏、DCA诱导的HN、HA和HC的福尔马林固定石蜡包埋切片，通过免疫组化方法检测肿瘤标志物的表达。结果表明，除c-jun标志物外，HN表达这些标志物的频率显著低于HA或HC。c-jun在三种病变类型中的表达相同。尽管这些结果可能用于证明HN与后期出现的HA和HC之间不存在关联，但那些标志物阳性的HN在正常未染色的肝细胞区域中含有小巢状的标志物阳性肝细胞。在HN以外的正常肝脏任何区域均未检测到类似的标志物阳性细胞巢。使用这些标志物、苏木精和伊红，或用于检测ATP酶或葡萄糖-6-磷酸酶缺乏的组织化学染色，也很少检测到改变的肝灶（AF）。这些结果表明，一些HN内的这些巢状区域是转化的或肿瘤性肝细胞区域。表型异质性分析检查了任何给定病变共表达的肿瘤标志物数量，结果证实，表达多种标志物的HA和HC的百分比显著高于HN。然而，那些表达多种标志物的HN，其表达频率与HA和HC相同，且表达局限于相同的细胞巢。综上所述，这些数据表明，HN内这些标志物阳性细胞巢是肿瘤性的，可能发展为后期出现的HA和/或HC。正常肝脏中无标志物表达，少数AF中表达有限，这表明HN可能是DCA诱导的肝癌发生中唯一重要的癌前病变。
