Manam S, Shinder G A, Joslyn D J, Kraynak A R, Hammermeister C L, Leander K R, Ledwith B J, Prahalada S, van Zwieten M J, Nichols W W
Department of Safety Assessment, Merck Research Laboratories, West Point, PA 19486, USA.
Carcinogenesis. 1995 May;16(5):1113-9. doi: 10.1093/carcin/16.5.1113.
We investigated the role of dosing regimen on ras mutations in chemically induced CD-1 mouse liver tumors. The spectra of ras gene mutations in liver tumors that were induced by 15 daily i.p. injections of 7,12-dimethylbenz[a]anthracene (DMBA), 4-aminoazobenzene (AAB), N-hydroxy-2-acetylaminofluorene (N-OH-AAF) or N-nitrosodiethylamine (DEN) were compared to those previously obtained for tumors induced by a single but higher dose of each carcinogen. The principal assay used was a direct tumor analysis involving sequencing of polymerase chain reaction (PCR)-amplified tumor DNA; additional mutations that were present in only a small fraction of tumor cells were detected using a transfection assay or a PCR-engineered restriction fragment length polymorphism method. Spontaneous liver tumors had a relatively low frequency of ras mutations, all found in Ha-ras codon 61, and most of these mutations were present in only a small fraction of tumor cells. With the exception of multiple-dose DEN, each group of single- and multiple-dose carcinogen-induced tumors exhibited a higher frequency of ras mutations compared with spontaneous tumors. For AAB, N-OH-AAF and DEN, the dosing regimen was found to affect significantly the profile of ras mutations. For each of these carcinogens, the multiple-dose tumor group (versus single-dose group) had fewer Ki-ras and N-ras mutations and more tumors in which the Ha-ras codon 61 (C-->A) mutation was present in a large fraction of cells. Our results demonstrate that the dosing procedure can materially affect the pattern of ras gene mutation in mouse liver tumors.
我们研究了给药方案对化学诱导的CD-1小鼠肝肿瘤中ras基因突变的作用。将通过每天腹腔注射15次7,12-二甲基苯并[a]蒽（DMBA）、4-氨基偶氮苯（AAB）、N-羟基-2-乙酰氨基芴（N-OH-AAF）或N-亚硝基二乙胺（DEN）诱导的肝肿瘤中的ras基因突变谱，与先前通过单次但更高剂量的每种致癌物诱导的肿瘤所获得的突变谱进行了比较。使用的主要检测方法是直接肿瘤分析，包括对聚合酶链反应（PCR）扩增的肿瘤DNA进行测序；使用转染检测或PCR工程化的限制性片段长度多态性方法检测仅在一小部分肿瘤细胞中存在的其他突变。自发肝肿瘤的ras基因突变频率相对较低，所有突变均在Ha-ras密码子61中发现，并且这些突变中的大多数仅存在于一小部分肿瘤细胞中。除了多剂量DEN外，与自发肿瘤相比，每组单剂量和多剂量致癌物诱导的肿瘤均表现出更高的ras基因突变频率。对于AAB、N-OH-AAF和DEN，发现给药方案会显著影响ras基因突变谱。对于每种致癌物，多剂量肿瘤组（与单剂量组相比）的Ki-ras和N-ras突变较少，并且有更多肿瘤中Ha-ras密码子61（C→A）突变存在于大部分细胞中。我们的结果表明，给药程序可实质性影响小鼠肝肿瘤中ras基因突变模式。
