Institut Curie, INSERM U830, Paris, France.
Cancer Res. 2010 Sep 1;70(17):6757-66. doi: 10.1158/0008-5472.CAN-09-4691. Epub 2010 Jul 21.
The multistage process of cancer formation is driven by the progressive acquisition of somatic mutations. Replication stress creates genomic instability in mammals. Using a well-defined multistep leukemia model driven by Spi-1/PU.1 overexpression in the mouse and Spi-1/PU.1-overexpressing human leukemic cells, we investigated the relationship between DNA replication and cancer progression. Here, using DNA molecular combing and flow cytometry methods, we show that Spi-1 increases the speed of replication by acting specifically on elongation rather than enhancing origin firing. This shortens the S-phase duration. Combining data from Spi-1 knockdown in murine cells with Spi-1 overexpression in human cells, we provide evidence that inappropriate Spi-1 expression is directly responsible for the replication alteration observed. Importantly, the acceleration of replication progression coincides with an increase in the frequency of genomic mutations without inducing DNA breakage. Thus, we propose that the hitherto unsuspected role for spi-1 oncogene in promoting replication elongation and genomic mutation promotes blastic progression during leukemic development.
癌症的多阶段形成过程是由体细胞突变的逐渐获得驱动的。复制应激在哺乳动物中造成基因组不稳定。使用在小鼠中由 Spi-1/PU.1 过表达驱动的明确的多步骤白血病模型和 Spi-1/PU.1 过表达的人类白血病细胞，我们研究了 DNA 复制与癌症进展之间的关系。在这里，我们使用 DNA 分子梳理和流式细胞术方法表明，Spi-1 通过特异性作用于延伸而不是增强起始来增加复制速度。这缩短了 S 期持续时间。将小鼠细胞中 Spi-1 敲低的数据与人类细胞中 Spi-1 过表达的数据相结合，我们提供了证据表明，不适当的 Spi-1 表达直接导致了观察到的复制改变。重要的是，复制进展的加速伴随着基因组突变频率的增加，而不会诱导 DNA 断裂。因此，我们提出，迄今为止未被怀疑的 spi-1 癌基因在促进复制延伸和基因组突变方面的作用促进了白血病发展过程中的成髓细胞性进展。
