Global DNA hypomethylation and DNA hypermethylation of promoter regions—including tumor suppressor genes—are frequently detected in human cancers. Although many studies have suggested a contribution to carcinogenesis, it is still unclear whether the aberrant DNA hypomethylation observed in tumors is a consequence or a cause of cancer. We found that overexpression of Stella (also known as PGC7, Dppa3), a maternal factor required for the maintenance of DNA methylation in early embryos, induced global DNA hypomethylation and transformation in NIH3T3 cells. This hypomethylation was due to the binding of Stella to Np95 (also known as Uhrf1, ICBP90) and the subsequent impairment of Dnmt1 localization. In addition, enforced expression of Stella enhanced the metastatic ability of B16 melanoma cells through the induction of metastasis-related genes by inducing DNA hypomethylation of their promoter regions. Such DNA hypomethylation itself causes cellular transformation and metastatic ability. These data provide new insight into the function of global DNA hypomethylation in carcinogenesis. We used microarrays to detail the global programme of gene expression by PGC7/Stella overexpression. RNA was extracted from NIH3T3 or B16F10 murine cell lines overexpressed PGC7/Stella and was hybridized on Affymetrix microarrays. We compared gene expression levels between control and PGC7/Stella-overexpressed cells. Microarray analysis was performed in NIH3T3 cells including two independent Stella-expressing NIH3T3 clones and a mixture of Stella-expressing NIH3T3 clones and in B16-F10 cells including three independent Stella-expressing B16-F10 clones.