Increased nuclear phosphatase and tensin homologue deleted on chromosome 10 is associated with G0-G1 in MCF-7 cells.

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor that causes cell cycle arrest. Lack of a nuclear locator sequence and a function in the cytosolic phosphatidylinositol 3'-kinase/Akt pathway diverted its study from the nucleus. However, immunohistochemistry revealed PTEN in the nucleus of normal cells and decreased nuclear PTEN in neoplastic tissues. Using protein expression analysis and fluoroscopic localization of green fluorescence protein-tagged PTEN, we examined nuclear PTEN in MCF-7 cells. We demonstrate that PTEN enters the nucleus and that nuclear PTEN varies throughout the cell cycle. Higher nuclear PTEN levels were associated with G0-G1 phase, and lower nuclear PTEN levels were associated with S phase. We postulate that nuclear PTEN activity might directly regulate the cell cycle.