Zhuang S, Söderkvist P
Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, Linköping University, Sweden.
Mutat Res. 2000 Jul 20;452(1):19-26. doi: 10.1016/s0027-5107(00)00031-2.
We have previously identified activation of ras proto-oncogenes and inactivation of tumor suppressor genes including p53, p16(INK4a) and p15(INK4b) in 2',3'-dideoxycytidine (ddC)- and/or 1,3-butadiene (BD)-induced lymphomas derived from B6C3F1 (C57BL/6xC3H/He) mice, indicating that alterations of ras signaling pathway, p53 and pRb growth control pathways are important in the development of these chemically induced lymphomas. However, there is still a subset of tumors that displayed no changes in these genes. Thus, we investigated whether the Raf1, Mdm2, c-Myc, Cdc25a and Cdc25b proto-oncogenes, which are implicated in the ras or p53 or pRb pathways, are alternative oncogenic target genes. Analyses of gross genomic alterations by Southern blots failed to reveal rearrangement or amplification in any of the tumors examined. Frequent point mutations on the substrate binding domain of the Raf1 gene has been reported in 1-ethyl-1-nitrosourea (ENU)-induced murine lymphomas and lung tumors, along with a conspicuous lack of ras mutations [U. Naumann, I. Eisenmann-Tappe, U.R. Rapp, The role of raf kinases in development and growth of tumors, Recent Results Cancer Res., 143 (1997) 237-244]. To investigate whether Raf1 mutation is involved in our set of tumor especially those without ras mutations, the PCR-based single-strand conformation analyses (SSCA) and direct DNA sequencing were employed. No mutations but four genetic polymorphisms between C57BL/6 and C3H/He were found, with two of them reported as point mutations previously (op. cit.). The polymorphisms were utilized for allelic loss study of Raf1 locus. Losses of heterozygosity were found in six of 31 BD-induced lymphomas. These results indicate that genetic alterations of c-Myc, Cdc25, Raf1 and Mdm2 proto-oncogenes may not be involved in the development of ddC- and BD-induced lymphomas and the inactivation of tumor suppressor gene(s) located close to Raf1 gene might be important in the development of a subset of BD-induced lymphomas.
我们之前已经在源自B6C3F1（C57BL/6xC3H/He）小鼠的2'，3'-二脱氧胞苷（ddC）和/或1,3-丁二烯（BD）诱导的淋巴瘤中鉴定出ras原癌基因的激活以及包括p53、p16（INK4a）和p15（INK4b）在内的肿瘤抑制基因的失活，这表明ras信号通路、p53和pRb生长控制通路的改变在这些化学诱导的淋巴瘤的发生发展中起重要作用。然而，仍有一部分肿瘤在这些基因中未显示出变化。因此，我们研究了与ras或p53或pRb通路相关的Raf1、Mdm2、c-Myc、Cdc25a和Cdc25b原癌基因是否为替代的致癌靶基因。通过Southern印迹分析基因组总体改变，未能在任何检测的肿瘤中发现重排或扩增。在1-乙基-1-亚硝基脲（ENU）诱导的小鼠淋巴瘤和肺癌中，已报道Raf1基因底物结合域存在频繁的点突变，同时明显缺乏ras突变[U. Naumann，I. Eisenmann-Tappe，U.R. Rapp，Raf激酶在肿瘤发生和生长中的作用，近期癌症研究成果，143（1997）237-244]。为了研究Raf1突变是否参与我们所研究的肿瘤，尤其是那些没有ras突变的肿瘤，采用了基于PCR的单链构象分析（SSCA）和直接DNA测序。未发现突变，但发现了C57BL/6和C3H/He之间的四个基因多态性，其中两个先前已报道为点突变（同前引）。这些多态性被用于Raf1基因座的杂合性缺失研究。在31个BD诱导的淋巴瘤中有6个发现了杂合性缺失。这些结果表明，c-Myc、Cdc25、Raf1和Mdm2原癌基因的遗传改变可能与ddC和BD诱导的淋巴瘤的发生无关，而位于Raf1基因附近的肿瘤抑制基因的失活可能在一部分BD诱导的淋巴瘤的发生中起重要作用。
