Role of the alternating reading frame (P19)-p53 pathway in an in vivo murine colon tumor model.
Role of the alternating reading frame (P19)-p53 pathway in an in vivo murine colon tumor model.
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发表时间：
2002-07
期刊：
影响因子：
11.2
通讯作者：
P. Nambiar;C. Giardina;K. Guda;Wataru Aizu;R. Raja;D. Rosenberg
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文献类型：
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作者：
P. Nambiar;C. Giardina;K. Guda;Wataru Aizu;R. Raja;D. Rosenberg
鉴于交替阅读框架(ARF)-P53途径癌基因检查点功能的重要性，我们研究了该途径在偶氮甲烷(AOM)诱导的小鼠结肠肿瘤中的作用。对正常结肠组织和AOM诱导的结肠肿瘤组织中ARF和P53cDNA的基于聚合酶链式反应的分析未能检测到这两个关键抑癌基因中的任何一个突变。此外，对肿瘤进行激光捕获显微切割，然后对基因组P53的第5-7外显子进行基于PCR的测序，结果表明，即使是最具多形性的癌细胞也是P53正常的。在结肠肿瘤中，ARF的mRNA和蛋白水平显著升高，表明ARF-P53通路在这些肿瘤中被激活。高水平的ARF蛋白稳定了肿瘤中的P53蛋白，但P53蛋白的生化活性很低。与高表达野生型P53(YAMC)的小鼠结肠癌细胞系相比，肿瘤中的P53蛋白没有检测到DNA结合活性，也没有激活p21的表达。事实上，肿瘤组织中的p21水平低于正常黏膜，尽管肿瘤组织中的p53水平比对照高出约30倍。在A/J肿瘤中，我们还使用了cDNA微阵列方法来筛选一组受功能性P53转录上调或下调的基因。这些受P53调控的基因的表达模式与功能P53的缺失相一致。这项工作表明，ARF-P53癌基因检查点可以在没有P53突变的情况下被克服，并且用于克服这一检查点的机制涉及抑制P53转录激活活性。AOM结肠癌模型可能非常适合于研究在P53干扰之前的肿瘤促进事件。
Considering the importance of the oncogene checkpoint function of the alternating reading frame(ARF)-p53 pathway, studies were undertaken to evaluate the status of this pathway in azoxymethane (AOM)-induced mouse colon tumors. A PCR-based analysis of ARF and p53 cDNAs in normal colon tissues and AOM-induced colon tumors failed to detect mutations in either of these two critical tumor suppressor genes. In addition, laser capture microdissection of tumors followed by PCR-based sequencing of exons 5-7 of genomic p53 showed that even the most pleomorphic cancer cells were p53 normal. A marked increase in ARF mRNA and protein levels was observed in colon tumors, indicating activation of the ARF-p53 pathway in these tumors. High levels of ARF protein stabilized p53 protein in the tumors, but the p53 protein showed little biochemical activity. Compared with a mouse colonocyte cell line that expresses high levels of wild-type p53 (YAMC), the p53 protein in tumors had no detectable DNA binding activity nor did it activate p21 expression. In fact, p21 levels were lower in tumor tissue relative to normal mucosa, even though p53 levels were approximately 30-fold higher in tumors relative to control. Within the A/J tumors, we also used a cDNA microarray approach to screen a panel of genes that are transcriptionally up- or down-regulated by functional p53. The expression patterns of these p53-regulated genes were consistent with a lack of functional p53. This work demonstrates that the ARF-p53 oncogene checkpoint can be overcome without p53 mutations and that the mechanism used to overcome this checkpoint involves the suppression of p53 transcriptional activating activity. The AOM colon cancer model may be well suited for studying tumor promotion events that precede p53 disruption.