Wise Young
11-28-2001, 06:29 AM
• Dubey P, Wu H, Reiter RE and Witte ON (2001). Alternative pathways to prostate carcinoma activate prostate stem cell antigen expression. Cancer Res. 61 (8): 3256-61. Summary: Prostate Stem Cell Antigen (PSCA) is a glycosylphosphatidylinositol-anchored cell surface protein that is expressed in normal human prostate and overexpressed in human prostate cancers. To test whether different pathways that generate prostate cancer would affect PSCA expression, a murine model system was developed. Monoclonal antibodies were generated against murine PSCA (mPSCA). mPSCA is expressed on approximately 20% of cells in normal prostate epithelium, and this number decreases with increasing age. In the transgenic adenocarcinoma of the mouse prostate (TRAMP) model of prostate cancer, tumors develop between 19 and 25 weeks of age. Murine PSCA was strongly expressed on approximately 60% of the cells of TRAMP tumors, at an age where the number of PSCA+ cells and the level of expression of PSCA is very low in the normal prostate. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) +/- mice develop a number of different cancers, including prostate cancer. The incidence of prostate cancer is low and occurs after a relatively long latency. Fluorescence-activated cell sorter analysis of prostatic tissue from 11-18-month-old PTEN +/- mice showed elevated numbers of PSCA+ cells in the prostate, and immunohistochemical analysis showed high mPSCA expression in the tumors of these mice. Together, these results show that two distinct mechanisms of carcinogenesis lead to expression of a common target antigen. <http://cancerres.aacrjournals.org/cgi/content/full/61/8/3256
http://cancerres.aacrjournals.org/cgi/content/abstract/61/8/3256
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11309275> Department of Microbiology, Howard Hughes Medical Institute, Los Angeles, CA 90095-1662, USA.
• Groszer M, Erickson R, Scripture-Adams D, Lesche R, Trumpp A, Zack JA, Kornblum HI, Liu X and Wu H (2001). Negative Regulation of Neural Stem/Progenitor Cell Proliferation by the Pten Tumor Suppressor Gene in Vivo. Science. Summary: The mechanisms controlling neural stem cell proliferation are poorly understood. Here we demonstrate that the PTEN tumor suppressor plays an important role in regulating neural stem/progenitor cells in vivo and in vitro. Mice lacking PTEN exhibited enlarged, histoarchitecturally abnormal brains, which resulted from increased cell proliferation, decreased cell death, and enlarged cell size. Neurosphere cultures revealed a greater proliferation capacity for tripotent Pten(-/-) CNS stem/progenitor cells, which is due, at least in part, to a shortened cell cycle. However, cell fate commitments of the progenitors were largely undisturbed. Our results suggest that PTEN negatively regulates neural stem cell proliferation. <http://www.sciencemag.org/cgi/content/abstract/1065518v1
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11691952> Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Medicine and AIDS Institute, UCLA School of Medicine, Los Angeles, CA 90095, USA., Epigenomics AG, Kastanienallee 24, 10435 Berlin, Germany; Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA., Institut Suisse de Recherche Experimentale sur le Cancer, Ch. de Boveresses 155, 1066 Epalinges/Lausanne, Switzerland., Department of Medicine and AIDS Institute, Department of Microbiology and Molecular Genetics, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, Department of Pediatrics, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, CA 90095, USA., Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA.
• Lilja JF, Wu D, Reynolds RK and Lin J (2001). Growth suppression activity of the PTEN tumor suppressor gene in human endometrial cancer cells. Anticancer Res. 21 (3B): 1969-74. Summary: The AKT proteins are constitutively activated in several types of human cancers, which may play a role in carcinogenesis. In this study, we examined the activation of AKT in a panel of human endometrial cancer cell lines and tumor samples in this study. Two endometrial cancer cell lines, Ishikawa (ISK) and RL-95 and several tumor samples showed elevated levels of phosphorylated AKT PTEN, which is mutated in 45% of endometrial cancers, is a negative regulator of AKT. We examined the growth suppression activity of PTEN in ISK and KLE endometrial cancer cells. Expression of PTEN significantly suppressed the growth of both cell clines. In primary rat embryo fibroblasts, PTEN also inhibited malignant transformation mediated by ras and c-myc oncogenes. These two oncogenes are commonly mutated or amplified in endometrial cancer. These results suggest that PTEN may be a potent therapeutic agent for endometrial cancer. <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11497285> Department of Obstetrics and Gynecology, The University of Michigan Comprehensive Cancer Center, Ann Arbor 48109, USA.
• Mamillapalli R, Gavrilova N, Mihaylova VT, Tsvetkov LM, Wu H, Zhang H and Sun H (2001). PTEN regulates the ubiquitin-dependent degradation of the CDK inhibitor p27(KIP1) through the ubiquitin E3 ligase SCF(SKP2). Curr Biol. 11 (4): 263-7. Summary: The PTEN tumor suppressor acts as a phosphatase for phosphatidylinositol-3,4,5-trisphosphate (PIP3) [1, 2]. We have shown previously that PTEN negatively controls the G1/S cell cycle transition and regulates the levels of p27(KIP1), a CDK inhibitor [3, 4]. Recently, we and others have identified an ubiquitin E3 ligase, the SCF(SKP2) complex, that mediates p27 ubiquitin-dependent proteolysis [5-7]. Here we report that PTEN and the PI 3-kinase pathway regulate p27 protein stability. PTEN-deficiency in mouse embryonic stem (ES) cells causes a decrease of p27 levels with concomitant increase of SKP2, a key component of the SCF(SKP2) complex. Conversely, in human glioblastoma cells, ectopic PTEN expression leads to p27 accumulation, which is accompanied by a reduction of SKP2. We found that ectopic expression of SKP2 alone is sufficient to reverse PTEN-induced p27 accumulation, restore the kinase activity of cyclin E/CDK2, and partially overcome the PTEN-induced G1 cell cycle arrest. Consistently, recombinant SCF(SKP2) complex or SKP2 protein alone can rescue the defect in p27 ubiquitination in extracts prepared from cells treated with a PI 3-kinase inhibitor. Our findings suggest that SKP2 functions as a critical component in the PTEN/PI 3-kinase pathway for the regulation of p27(KIP1) and cell proliferation. <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11250155> Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA.
• Neshat MS, Mellinghoff IK, Tran C, Stiles B, Thomas G, Petersen R, Frost P, Gibbons JJ, Wu H and Sawyers CL (2001). Enhanced sensitivity of PTEN-deficient tumors to inhibition of FRAP/mTOR. Proc Natl Acad Sci U S A. 98 (18): 10314-9. Summary: Recent evidence places the FRAP/mTOR kinase downstream of the phosphatidyl inositol 3-kinase/Akt-signaling pathway, which is up-regulated in multiple cancers because of loss of the PTEN tumor suppressor gene. We performed biological and biochemical studies to determine whether PTEN-deficient cancer cells are sensitive to pharmacologic inhibition of FRAP/mTOR by using the rapamycin derivative CCI-779. In vitro and in vivo studies of isogenic PTEN(+/+) and PTEN(-/-) mouse cells as well as human cancer cells with defined PTEN status showed that the growth of PTEN null cells was blocked preferentially by pharmacologic FRAP/mTOR inhibition. Enhanced tumor growth caused by constitutive activation of Akt in PTEN(+/+) cells also was reversed by CCI-779 treatment, indicating that FRAP/mTOR functions downstream of Akt in tumorigenesis. Loss of PTEN correlated with increased S6 kinase activity and phosphorylation of ribosomal S6 protein, providing evidence for activation of the FRAP/mTOR pathway in these cells. Differential sensitivity to CCI-779 was not explained by differences in biochemical blockade of the FRAP/mTOR pathway, because S6 phosphorylation was inhibited in sensitive and resistant cell lines. These results provide rationale for testing FRAP/mTOR inhibitors in PTEN null human cancers. <http://www.pnas.org/cgi/content/full/98/18/10314
http://www.pnas.org/cgi/content/abstract/98/18/10314
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11504908> Department of Medicine, University of California School of Medicine, Los Angeles, CA 90095, USA.
• Wu Y, Dowbenko D, Pisabarro MT, Dillard-Telm L, Koeppen H and Lasky LA (2001). PTEN 2, a Golgi-associated testis-specific homologue of the PTEN tumor suppressor lipid phosphatase. J Biol Chem. 276 (24): 21745-53. Summary: The tumor suppressor PTEN is a phosphatidylinositol phospholipid phosphatase, which indirectly down-regulates the activity of the protein kinase B/Akt survival kinases. Examination of sequence data bases revealed the existence of a highly conserved homologue of PTEN. This homologue, termed PTEN 2, contained an extended amino-terminal domain having four potential transmembrane motifs, a lipid phosphatase domain, and a potential lipid-binding C2 domain. Transcript analysis demonstrated that PTEN 2 is expressed only in testis and specifically in secondary spermatocytes. In contrast to PTEN, PTEN 2 was localized to the Golgi apparatus via the amino-terminal membrane-spanning regions. Molecular modeling suggested that PTEN 2 is a phospholipid phosphatase with potential specificity for the phosphate at the 3 position of inositol phosphates. Enzymatic analysis of PTEN 2 revealed substrate specificity that is similar to PTEN, with a preference for the dephosphorylation of the phosphatidylinositol 3,5-phosphate phospholipid, a known mediator of vesicular trafficking. Together, these data suggest that PTEN 2 is a Golgi-localized, testis-specific phospholipid phosphatase, which may contribute to the terminal stages of spermatocyte differentiation. <http://www.jbc.org/cgi/content/full/276/24/21745
http://www.jbc.org/cgi/content/abstract/276/24/21745
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11279206> Department of Molecular Oncology, Genentech, Inc., South San Francisco, California 94080, USA.
http://cancerres.aacrjournals.org/cgi/content/abstract/61/8/3256
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11309275> Department of Microbiology, Howard Hughes Medical Institute, Los Angeles, CA 90095-1662, USA.
• Groszer M, Erickson R, Scripture-Adams D, Lesche R, Trumpp A, Zack JA, Kornblum HI, Liu X and Wu H (2001). Negative Regulation of Neural Stem/Progenitor Cell Proliferation by the Pten Tumor Suppressor Gene in Vivo. Science. Summary: The mechanisms controlling neural stem cell proliferation are poorly understood. Here we demonstrate that the PTEN tumor suppressor plays an important role in regulating neural stem/progenitor cells in vivo and in vitro. Mice lacking PTEN exhibited enlarged, histoarchitecturally abnormal brains, which resulted from increased cell proliferation, decreased cell death, and enlarged cell size. Neurosphere cultures revealed a greater proliferation capacity for tripotent Pten(-/-) CNS stem/progenitor cells, which is due, at least in part, to a shortened cell cycle. However, cell fate commitments of the progenitors were largely undisturbed. Our results suggest that PTEN negatively regulates neural stem cell proliferation. <http://www.sciencemag.org/cgi/content/abstract/1065518v1
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11691952> Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Medicine and AIDS Institute, UCLA School of Medicine, Los Angeles, CA 90095, USA., Epigenomics AG, Kastanienallee 24, 10435 Berlin, Germany; Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA., Institut Suisse de Recherche Experimentale sur le Cancer, Ch. de Boveresses 155, 1066 Epalinges/Lausanne, Switzerland., Department of Medicine and AIDS Institute, Department of Microbiology and Molecular Genetics, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, Department of Pediatrics, UCLA School of Medicine, Los Angeles, CA 90095, USA., Department of Molecular and Medical Pharmacology, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, CA 90095, USA., Howard Hughes Medical Institute, Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, CA 90095, USA.
• Lilja JF, Wu D, Reynolds RK and Lin J (2001). Growth suppression activity of the PTEN tumor suppressor gene in human endometrial cancer cells. Anticancer Res. 21 (3B): 1969-74. Summary: The AKT proteins are constitutively activated in several types of human cancers, which may play a role in carcinogenesis. In this study, we examined the activation of AKT in a panel of human endometrial cancer cell lines and tumor samples in this study. Two endometrial cancer cell lines, Ishikawa (ISK) and RL-95 and several tumor samples showed elevated levels of phosphorylated AKT PTEN, which is mutated in 45% of endometrial cancers, is a negative regulator of AKT. We examined the growth suppression activity of PTEN in ISK and KLE endometrial cancer cells. Expression of PTEN significantly suppressed the growth of both cell clines. In primary rat embryo fibroblasts, PTEN also inhibited malignant transformation mediated by ras and c-myc oncogenes. These two oncogenes are commonly mutated or amplified in endometrial cancer. These results suggest that PTEN may be a potent therapeutic agent for endometrial cancer. <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11497285> Department of Obstetrics and Gynecology, The University of Michigan Comprehensive Cancer Center, Ann Arbor 48109, USA.
• Mamillapalli R, Gavrilova N, Mihaylova VT, Tsvetkov LM, Wu H, Zhang H and Sun H (2001). PTEN regulates the ubiquitin-dependent degradation of the CDK inhibitor p27(KIP1) through the ubiquitin E3 ligase SCF(SKP2). Curr Biol. 11 (4): 263-7. Summary: The PTEN tumor suppressor acts as a phosphatase for phosphatidylinositol-3,4,5-trisphosphate (PIP3) [1, 2]. We have shown previously that PTEN negatively controls the G1/S cell cycle transition and regulates the levels of p27(KIP1), a CDK inhibitor [3, 4]. Recently, we and others have identified an ubiquitin E3 ligase, the SCF(SKP2) complex, that mediates p27 ubiquitin-dependent proteolysis [5-7]. Here we report that PTEN and the PI 3-kinase pathway regulate p27 protein stability. PTEN-deficiency in mouse embryonic stem (ES) cells causes a decrease of p27 levels with concomitant increase of SKP2, a key component of the SCF(SKP2) complex. Conversely, in human glioblastoma cells, ectopic PTEN expression leads to p27 accumulation, which is accompanied by a reduction of SKP2. We found that ectopic expression of SKP2 alone is sufficient to reverse PTEN-induced p27 accumulation, restore the kinase activity of cyclin E/CDK2, and partially overcome the PTEN-induced G1 cell cycle arrest. Consistently, recombinant SCF(SKP2) complex or SKP2 protein alone can rescue the defect in p27 ubiquitination in extracts prepared from cells treated with a PI 3-kinase inhibitor. Our findings suggest that SKP2 functions as a critical component in the PTEN/PI 3-kinase pathway for the regulation of p27(KIP1) and cell proliferation. <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11250155> Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA.
• Neshat MS, Mellinghoff IK, Tran C, Stiles B, Thomas G, Petersen R, Frost P, Gibbons JJ, Wu H and Sawyers CL (2001). Enhanced sensitivity of PTEN-deficient tumors to inhibition of FRAP/mTOR. Proc Natl Acad Sci U S A. 98 (18): 10314-9. Summary: Recent evidence places the FRAP/mTOR kinase downstream of the phosphatidyl inositol 3-kinase/Akt-signaling pathway, which is up-regulated in multiple cancers because of loss of the PTEN tumor suppressor gene. We performed biological and biochemical studies to determine whether PTEN-deficient cancer cells are sensitive to pharmacologic inhibition of FRAP/mTOR by using the rapamycin derivative CCI-779. In vitro and in vivo studies of isogenic PTEN(+/+) and PTEN(-/-) mouse cells as well as human cancer cells with defined PTEN status showed that the growth of PTEN null cells was blocked preferentially by pharmacologic FRAP/mTOR inhibition. Enhanced tumor growth caused by constitutive activation of Akt in PTEN(+/+) cells also was reversed by CCI-779 treatment, indicating that FRAP/mTOR functions downstream of Akt in tumorigenesis. Loss of PTEN correlated with increased S6 kinase activity and phosphorylation of ribosomal S6 protein, providing evidence for activation of the FRAP/mTOR pathway in these cells. Differential sensitivity to CCI-779 was not explained by differences in biochemical blockade of the FRAP/mTOR pathway, because S6 phosphorylation was inhibited in sensitive and resistant cell lines. These results provide rationale for testing FRAP/mTOR inhibitors in PTEN null human cancers. <http://www.pnas.org/cgi/content/full/98/18/10314
http://www.pnas.org/cgi/content/abstract/98/18/10314
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11504908> Department of Medicine, University of California School of Medicine, Los Angeles, CA 90095, USA.
• Wu Y, Dowbenko D, Pisabarro MT, Dillard-Telm L, Koeppen H and Lasky LA (2001). PTEN 2, a Golgi-associated testis-specific homologue of the PTEN tumor suppressor lipid phosphatase. J Biol Chem. 276 (24): 21745-53. Summary: The tumor suppressor PTEN is a phosphatidylinositol phospholipid phosphatase, which indirectly down-regulates the activity of the protein kinase B/Akt survival kinases. Examination of sequence data bases revealed the existence of a highly conserved homologue of PTEN. This homologue, termed PTEN 2, contained an extended amino-terminal domain having four potential transmembrane motifs, a lipid phosphatase domain, and a potential lipid-binding C2 domain. Transcript analysis demonstrated that PTEN 2 is expressed only in testis and specifically in secondary spermatocytes. In contrast to PTEN, PTEN 2 was localized to the Golgi apparatus via the amino-terminal membrane-spanning regions. Molecular modeling suggested that PTEN 2 is a phospholipid phosphatase with potential specificity for the phosphate at the 3 position of inositol phosphates. Enzymatic analysis of PTEN 2 revealed substrate specificity that is similar to PTEN, with a preference for the dephosphorylation of the phosphatidylinositol 3,5-phosphate phospholipid, a known mediator of vesicular trafficking. Together, these data suggest that PTEN 2 is a Golgi-localized, testis-specific phospholipid phosphatase, which may contribute to the terminal stages of spermatocyte differentiation. <http://www.jbc.org/cgi/content/full/276/24/21745
http://www.jbc.org/cgi/content/abstract/276/24/21745
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11279206> Department of Molecular Oncology, Genentech, Inc., South San Francisco, California 94080, USA.