The level and distribution of methylation across the TOX3 promoter CpG island and its impact on the expression of this gene was evaluated as described for TOX2. COBRA (Figure 4A) and bisulfite sequencing of 58 CpGs within the TOX3 promoter CpG island (Figure 4B) revealed that TOX3 is unmethylated in all normal samples and some lung and breast cancer cell lines. Here, TOX3 is linked to breast cancer.