Phosphatase and tensin homolog on chromosome ten (PTEN) is a ubiquitously expressed tumor suppressor which, in the cytoplasm, antagonizes the PI3K signaling pathway through its lipid phosphatase activity. Mutations of this gene are an important step in the development of many cancers since PTEN regulates essential cellular process such as growth and survival. PTEN is also found in the nucleus, and studies have demonstrated that its presence in the nucleus is regulated by SUMOylation and phosphorylation. Also, studies have showed that cells lacking nuclear PTEN are more sensitive to DNA damage.