Truncating APC mutations have dominant effects on proliferation, spindle checkpoint control, survival and chromosome stability
Truncating APC mutations have dominant effects on proliferation, spindle checkpoint control, survival and chromosome stability
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DOI：
10.1242/jcs.01556
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发表时间：
2004-12-15
影响因子：
4
通讯作者：
Taylor, SS
中科院分区：
文献类型：
--
作者：
Tighe, A;Johnson, VL;Taylor, SS
由于潜在的染色体不稳定性表型，大多数人类肿瘤细胞是非整倍体。虽然导致染色体不稳定的遗传病变仍不明确，但携带纯合性结肠腺瘤性息肉病（APC）突变的小鼠ES细胞通常是四倍体。此外，具有APC突变的结肠癌细胞具有减弱的着丝粒-微管相互作用。此外，有丝分裂纺锤体组装在APC耗尽爪蟾卵提取物是异常的。因此，为了确定APC突变是否可以在人类细胞中引发染色体不稳定性，我们在HCT-116细胞中表达了N-末端APC片段，HCT-116细胞是一种具有两个野生型APC等位基因的近二倍体结肠癌细胞系。我们发现，表达N-APC突变体的细胞在纺锤体毒素的存在下过早地退出有丝分裂，这与纺锤体检查点缺陷一致。此外，N-APC细胞在长时间纺锤体损伤后显示出增强的存活。与对照组相比，N-APC幸存者经常含有双着丝粒染色体，然后继续成为高度非整倍体。这些观察结果表明，截短APC突变可以发挥显性效应，这反过来又可以启动染色体不稳定性。因此，APC突变不仅会损害肿瘤抑制功能，而且还可能具有致癌特性。因此，我们认为最初的APC突变起到了“双重打击”的作用，使基因组不稳定，并为第二个APC等位基因丢失后的失控增殖奠定了基础。
The majority of human tumour cells are aneuploid owing to an underlying chromosome instability phenotype. While the genetic lesions that cause chromosome instability remain undefined, mouse ES cells harbouring homozygous adenomatous polyposis coli (APC) mutations are frequently tetraploid. In addition, colon cancer cells with APC mutations have weakened kinetochore-microtubule interactions. Furthermore, mitotic spindles assembled in APC-depleted Xenopus egg extracts are aberrant. Therefore, to determine whether APC mutations can initiate chromosome instability in human cells, we expressed N-terminal APC fragments in HCT-116 cells, a near diploid colon cancer cell line with two wild-type APC alleles. We show that cells expressing N-APC mutants exit mitosis prematurely in the presence of spindle toxins, consistent with a spindle checkpoint defect. In addition, N-APC cells show enhanced survival following prolonged spindle damage. In contrast to controls, the N-APC survivors frequently contain dicentric chromosomes and then go on to become highly aneuploid. These observations suggest that truncating APC mutations can exert dominant effects which in turn can initiate chromosome instability. As such, APC mutation not only compromises tumour suppressor function but may also have oncogenic properties. We suggest therefore that the initial APC mutation acts as a 'double whammy', destabilising the genome and setting the stage for deregulated proliferation upon loss of the second APC allele.