Schulte-Hermann R, Timmermann-Trosiener I, Barthel G, Bursch W
Institut für Tumorbiologie-Krebsforschung, Universität Wien, Austria.
Cancer Res. 1990 Aug 15;50(16):5127-35.
Carcinogenesis was initiated in female rat liver by a single dose of N-nitrosomorpholine; subsequently phenobarbital (PB) was administered via the diet at a daily dose of 50 mg/kg body weight for up to 49 weeks. Subgroups of rats were left untreated after 10 or 28 weeks on PB. PB produced the following changes: (a) accelerated appearance of neoplastic nodules and hepatocellular carcinoma (from 28 weeks onwards); (b) phenotypic changes in altered foci such as a shift from clear to eosinophilic appearance, enhanced expression of gamma-glutamyltranspeptidase and other markers, and more distinct borders from surrounding liver; (c) an increase in foci number; and (d) accelerated foci enlargement. The increase in foci number was found to be due to increased phenotypic expression of foci. DNA synthesis was measured by [3H]thymidine labeling at multiple time points. The rate of DNA synthesis was always approximately 10-fold higher in foci than in surrounding liver tissue. Despite this, after N-nitrosomorpholine alone foci grew little before 18-24 weeks. Continuous treatment with PB did not produce a persistent further increase of DNA synthesis in foci, although it accelerated foci growth. Furthermore, at early stages small and larger foci showed similar DNA synthesis activity. These findings indicate that the rate of cell replication as measured by DNA synthesis is not the only determinant of the growth rate of foci. Further studies showed that foci with indistinct borders (reflecting weak expression of the altered phenotype) grew much less than foci with distinct borders; this was at least in part due to an increased rate of cell death by apoptosis found in foci with indistinct borders. In conclusion, besides cell replication, apoptosis and the extent of phenotypic expression (remodeling) determine the growth rate of foci. Foci with weak phenotypic expression predominated after N-nitrosomorpholine alone; in these, a high incidence of apoptosis counterbalanced cell replication. In contrast, during PB treatment foci with strong phenotypic expression predominated; in these, apoptotic activity was lower and the high replicative activity could manifest itself. Finally, all effects of PB on foci were largely although not completely reversible upon cessation of treatment; as a result phenotypic expression declined, and "remodeling" foci with high apoptotic activity predominated again.
通过单次给予N-亚硝基吗啉在雌性大鼠肝脏中引发致癌作用；随后通过饮食以每日50 mg/kg体重的剂量给予苯巴比妥（PB），持续49周。在给予PB 10周或28周后，将大鼠亚组不进行处理。PB产生了以下变化：（a）加速肿瘤结节和肝细胞癌的出现（从28周起）；（b）改变灶的表型变化，如从清亮外观转变为嗜酸性外观、γ-谷氨酰转肽酶和其他标志物的表达增强以及与周围肝脏的边界更清晰；（c）灶数量增加；（d）灶加速增大。发现灶数量的增加是由于灶的表型表达增加。通过在多个时间点进行[3H]胸苷标记来测量DNA合成。灶中的DNA合成速率始终比周围肝组织高约10倍。尽管如此，仅给予N-亚硝基吗啉后，灶在18 - 24周之前几乎没有生长。持续用PB处理虽然加速了灶的生长，但并未使灶中的DNA合成持续进一步增加。此外，在早期，小灶和大灶显示出相似的DNA合成活性。这些发现表明，通过DNA合成测量的细胞复制速率不是灶生长速率的唯一决定因素。进一步的研究表明，边界不清晰的灶（反映改变表型的弱表达）的生长比边界清晰的灶少得多；这至少部分是由于在边界不清晰的灶中发现凋亡导致的细胞死亡速率增加。总之，除了细胞复制外，凋亡和表型表达（重塑）的程度决定了灶的生长速率。仅给予N-亚硝基吗啉后，表型表达弱的灶占主导；在这些灶中，高凋亡发生率抵消了细胞复制。相反，在PB处理期间，表型表达强的灶占主导；在这些灶中，凋亡活性较低，高复制活性得以显现。最后，PB对灶的所有作用在停止治疗后虽然不是完全可逆，但在很大程度上是可逆的；结果表型表达下降，具有高凋亡活性的“重塑”灶再次占主导。
