Cancer metastasis was mediated by circulating tumor cells (CTCs) found in the blood of cancer patient. Our research was mainly focused on the genetic architecture of cancer related genomic variations. By comparing copy number variation of CTCs of a small cell lung cancer patient collected from different time points, we found a large number of ubiquitous (widely present in CTCs) copy number decreased genes, suggesting that these tumor cells are easier to shed into blood vessel while cancer metastasis. We have also found that the occurrence of copy number variation is slightly reversely correlated with expression level of many normal human tissues and the anti-correlation is most significantly displayed  on primary tumor originated tissue or tissues with highly similar expression profiles. This found may help to understand how cancer cell acquire increased fitness through gnomic mutation and accompanying phenotypic change. Meanwhile these research may provide theoretical foundation for new cancer diagnosis technology. Finally, we are combining more epigenomic data and other cancer types to see whether one or some epigenetic modifications are mainly factors related to the CNVs and whether the associations between expression regulation and genomic variations  wildly present in different cancer types.