PTEN是抑癌基因，编码蛋白是一种脂质和蛋白磷酸酶。PTEN具有多种生理功能，最显著的是作为磷脂酶在细胞膜上将磷脂酰肌醇（3,4,5）-三磷酸（PIP3）转化为磷脂酰肌醇（4,5）-二磷酸（PIP2）。PTEN功能损害会导致PIP3积累和下游AKT / mTOR信号传导的组成型激活。因此，PTEN失活促进细胞生长，增殖和存活。另外，核PTEN被认为调节RAD51表达，并且以这种方式还与DNA链断裂的同源重组和修复相关。因此，PTEN的丧失也可能导致更大的基因组不稳定性并促进其他有害突变的积累。PTEN突变经常在多种人类癌症中发生。大约80％的Cowden综合征的患者具有PTEN的胚系突变，Cowden综合征易患癌症，与高外显率乳腺癌和甲状腺癌有关。

PTEN encodes a tumor suppressor that is one of the most frequently mutated genes in human cancer. PTEN has several physiological functions, most notably operating as a phosphatase that converts phosphatidylinositol (3, 4, 5)-triphosphate (PIP3) to phosphatidylinositol (4, 5)-triphosphate (PIP2) at the cell membrane. Impairment of PTEN function through multiple mechanisms, including through non-synonymous mutations, results in PIP3 accumulation and constitutive activation of catabolic downstream AKT/mTOR signaling. PTEN inactivation therefore promotes cell growth, proliferation and survival. Additionally, nuclear PTEN is thought to regulate RAD51 expression, and in this way is also associated with homologous recombination and repair of DNA strand breaks. Thus, loss of PTEN may also lead to greater genomic instability and provide a setting for the accumulation of other deleterious mutations. PTEN is frequently mutated in many types of human cancers. Germline loss-of-function PTEN mutations occur in approximately 80% of patients with the cancer predisposition syndrome Cowden disease, which is associated with high-penetrance breast and thyroid cancer.

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