PTEN (a.k.a. MMAC1 and TEP1) and Cowden’s Disease “Phosphatase and tensin homolog on Chromosome ten” PTEN (a.k.a. MMAC1 and TEP1) and Cowden’s Disease

Cowden Disease Multiple benign growths – hamartomas CD confers an increased susceptibility to malignant carcinomas Breast cancer, thyroid cancers and glioblastoma GLIOBLASTOMA http:www.ncbi.nlm.nih.gov

Cowden Disease 89% of females with CD get breast hamartomas 74% develop malignant breast tumors (Schrager et al. 1998) 50% - 75% of people with CD develop thyroid disease Prostate Cancer Loss of PTEN and p27 In many of the cases of advanced metastatic tumors, the individual has also suffered additional mutations

Discovery of PTEN In 1996 Cowden Syndrome was mapped to the 10q22-23 This region is also commonly mutated in thyroid cancers

Phosphatase and Tensin Homologue on Chromosome 10 Either germline or sporadic mutation 80% have a germline mutation PTEN acts as classic tumor suppressor Inherited as an autosomal dominant trait Must lose both copies to be affected - Loss of Heterozygosity (LOH) 81% of Cowden’s Disease patients have suffered a mutation in PTEN. 80% of CD patients with a PTEN mutation have a germline mutation, the remaining 20% lost the PTEN gene by sporadic mutation Simpson and Parsons.(2001) Experimental Cell Research 264, 29-41

PTEN is a Phosphatase High degree of sequence homology with typical protein phosphatase Postulated dual specificity as a protein and lipid phosphatase As a protein phosphatase PTEN is thought to regulate the MAP kinase pathway by dephosphorylating serine/threonine residues upstream of ERK and FAK

Phosphatase and Tensin Homologue on Chromosome 10 Component of the PIP3/PI3K/AKT pathway NEGATIVE REGULATOR of this pathway Antagonist of cell survival, cell growth, cell cycle and cell migration FROM HERE ON OUT I WILL BE TALKING ABOUT PTEN AS A LIPID PHOSPHATASE Since we’ve already established that it acts as a tumor suppressor it makes sense that it is a negative regulator of a pathway that promotes cell survival, growth, cycle progression and cell migration Waite and Eng.(2002) Am. J. Hum. Genet. 70:829-844

Biochemical Structure and Activity of PTEN Phosphatase Catalytic Domain Protein Protein Binding Domain Lipid Binding Domain Stability N C 403 aa

Biochemical Structure and Function of PTEN Active site of the phosphatase domain

PTEN Intracellular role PTEN functions in the PI3K/AKT pathway by negatively regulating the levels of PtdIns(3,4,5)P3 or PIP3 PIP3 is a potent secondary messenger that binds proteins with PH domains 1999. Coffee Break. PTEN and the Tumor Suppressor. 1-3

Biochemical Structure and Activity of PTEN Found 8 different mutations in PTEN Protein Protein Binding Domain Phosphatase Catalytic Domain Lipid Binding Domain Stability 186 403 In studies on the CD patients they identified 8 different mutations scattered throughout the length of the protein with a clustering in Exon 5, which contains the phosphatase catalytic domain, specifically the substitution of an E for a G at amino acid 129 “Hot Spot” – 31% of all mutations G129E 43% of all mutations

PTEN Intracellular role 1999. Coffee Break. PTEN and the Tumor Suppressor. 1-3

Cooper (2000) The CELL a Molecular Approach fig.15.3 Critical Role of Akt AKT family proteins directly stimulate cell division, cell growth, angiogenesis and INHIBITS apoptosis SUPPRESSES CELL DEATH!!! Cooper (2000) The CELL a Molecular Approach fig.15.3

Biochemical structure and function of PTEN Converts PIP3  PIP2 = INACTIVATED PIP2 can NOT signal AKT = Suppression of GROWTH Loss of PTEN results in hyper-accumulation of PIP3 This leads to hyper-activation of AKT Result = INCREASED GROWTH, DIVISION and the ability to EVADE APOPTOSIS Sulis and Parson(2003) TRENDS in Cell Biology Vol.13:9

Simpson and Parsons (2001) Experimental Cell Research 264, 29-41 Cellular Role of PTEN Cell Culture: PTEN -/- mutants – showed a decreased sensitivity to apoptotic signals These mutants could be rescued by reintroduction of PTEN Mice Knockouts: PTEN -/- mutant – LETHAL PTEN -/+ mutants developed multiple tumors including endometrial, prostate, thyroid and colon Simpson and Parsons (2001) Experimental Cell Research 264, 29-41