PTEN is a tumor suppressor gene, located on chromosome 10q23, and loss of PTEN results in upregulation of the PI3K/ AKT pathway. Loss of PTEN may occur due to homozygous deletion, nonsense mutations, promoter hypermethylation, or with loss of heterozygosity (LOH). In prostate cancer, homozygous deletions spanning the PTEN locus occurs at one of the highest rates of any tumor type studied thus far. PTEN mutations may occur in multiple exons. Approximately in 25%-70% of prostate cancer, PI3K pathway has been altered either through PI3k overactivation or PTEN inactivation. PTEN is inactivated mainly through deletion in nearly 40%, or mutations in about 10%; both are more common in advanced prostate cancer.

PTEN is an obligate haplo-insufficient tumor suppressor gene and is mutated in a large number of cancers. It encodes a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase. It negatively regulates intracellular levels of phosphatidylinositol-3,4,5-trisphosphate in cells and functions as a tumor suppressor by negatively regulating AKT/mTOR signaling pathway. Most PTEN mutations are loss-of-function mutations. Mono-allelic or bi-allelic loss of PTEN is found in a considerable fraction of tumors, including gliomas (75%). In glioblastoma, PTEN loss/deletion is associated with poor patient prognosis, and/or shorter disease-free survival. There are ongoing clinical trials investigating anti-tumor activity of agents in recurrent glioblastoma with this mutation.

PTEN is an obligate haplo-insufficient tumor suppressor gene and is commonly mutated in a large number of cancers. It negatively regulates intracellular levels of Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in cells and functions as a tumor suppressor by negatively regulating AKT/mTOR signaling pathway. Mono- and bi-allelic loss of PTEN is found in approximately 40-50% and 5% of breast cancers, respectively. It has been reported to occur in BRCA1-associated basal-like breast cancer. Germline mutations in PTEN are also responsible for Cowden disease, a rare autosomal dominant multiple-hamartoma syndrome. In one study, germline mutations of PTEN have been reported to be associated with 85% lifetime risk of breast cancer in patients with PTEN hamartoma tumor syndrome. Aberrant PTEN pathway is associated with metastases and poor prognosis in breast cancer. It also predicts poor response to trastuzumab. There are ongoing clinical trials investigating anti-tumor activity of PI3K-beta inhibitor in PTEN deficient tumors.