To determine whether bovine oocyte extract can affect the DNA methylation levels of gene promoters in cancer cells, we performed bisulphite sequencing for the tumour suppressor genes RUNX3 and CDH1, and the oncogenic pluripotency gene SOX2. The results (Fig. 1) showed that the promoter CpG islands of RUNX3 and CDH1 were both hypermethylated in untreated and buffer-treated cells. Here, SOX2 is linked to cancer.