The biology and clinical relevance of the PTEN tumor suppressor pathway.
Genetic alterations targeting the PTEN tumor suppressor gene are among the most frequently noted somatic mutations in human cancers. Such lesions have been noted in cancers of the prostate and endometrium and in glioblastoma multiforme, among many others. Moreover, germline mutation of PTEN leads to the development of the related hereditary cancer predisposition syndromes, Cowden disease, and Bannayan-Zonana syndrome, wherein breast and thyroid cancer incidence is elevated. The protein product, PTEN, is a lipid phosphatase, the enzymatic activity of which primarily serves to remove phosphate groups from key intracellular phosphoinositide signaling molecules. This activity normally serves to restrict growth and survival signals by limiting activity of the phosphoinositide-3 kinase (PI3K) pathway. Multiple lines of evidence support the notion that this function is critical to the ability of PTEN to maintain cell homeostasis. Indeed, the absence of functional PTEN in cancer cells leads to constitutive activation of downstream components of the PI3K pathway including the Akt and mTOR kinases. In model organisms, inactivation of these kinases can reverse the effects of PTEN loss. These data raise the possibility that drugs targeting these kinases, or PI3K itself, might have significant therapeutic activity in PTEN-null cancers. Akt kinase inhibitors are still in development; however, as a first test of this hypothesis, phase I and phase II trials of inhibitors of mTOR, namely, rapamycin and rapamycin analogs are underway.
Sansal
Isabelle
I
Department of Medical Oncology, Dana-Farber Cancer Institute, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA.
Sellers
William R
WR
D000970:Antineoplastic Agents / Q000627:therapeutic use; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D009154:Mutation / Q000235:genetics; D009369:Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000503:physiopathology; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology*; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000502:physiology*
D000970:Antineoplastic Agents; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D058570:TOR Serine-Threonine Kinases; D025521:Tumor Suppressor Proteins; C546842:MTOR protein, human; C494929:PTEN protein, human