Germline mutations in PTEN are present in Bannayan-Zonana syndrome

Hamartomatous polyposis syndromes

Since the histologic description of the hamartomatous polyp in 1957 by Horrilleno and colleagues, descriptions have appeared of several different syndromes with the propensity to develop these polyps in the upper and lower gastrointestinal tracts. These syndromes include juvenile polyposis, Peutz-Jeghers syndrome, hereditary mixed polyposis syndrome, and the phosphatase and tensin homolog gene (PTEN) hamartoma tumor syndromes (Cowden and Bannayan-Riley-Ruvalcaba syndromes), which are autosomal-dominantly inherited, and Cronkhite-Canada syndrome, which is acquired. This article reviews the clinical aspects, the molecular pathogenesis, the affected organ systems, the risks of cancer, and the management of these hamartomatous polyposis syndromes. Although the incidence of these syndromes is low, it is important for clinicians to recognize these disorders to prevent morbidity and mortality in these patients, and to perform presymptomatic testing in patients at risk.

Differential expression of PTEN-targeting microRNAs miR-19a and miR-21 in Cowden syndrome

Germline mutations in the gene encoding phosphatase and tensin homolog deleted on chromosome ten (PTEN [MIM 601728]) are associated with a number of clinically distinct heritable cancer syndromes, including both Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRRS). Seemingly identical pathogenic PTEN mutations have been observed in patients with CS and BRRS, as well as in patients with incomplete features of CS, referred to as CS-like (CSL) patients. These observations indicate that additional, unidentified, genetic and epigenetic factors act as phenotypic modifiers in these disorders. These genetic factors could also contribute to disease in patients with CS, CSL, or BRRS without identifiable PTEN mutations. Two potential modifiers are miR-19a and miR-21, which are previously identified PTEN-targeting miRNAs. We investigated the role of these miRNAs by characterizing their relative expression levels in PTEN-mutation-positive and PTEN-mutation-negative patients with CS, CSL, or BRRS. Interestingly, we observed differential expression of miR-19a and miR-21 in our PTEN-mutation-positive patients. Both were found to be significantly overexpressed within this group (p < 0.01) and were inversely correlated with germline PTEN protein levels. Similarly, the relative expression of miR-19a and miR-21 was differentially expressed in a series of PTEN-mutation-negative patients with CS or CSL with variable clinical phenotypes and decreased full-length PTEN protein expression. Among PTEN-mutation-positive patients with CS, both miRNAs were significantly overexpressed (p = 0.006-0.013). Taken together, our study results suggest that differential expression of PTEN-targeting miR-19a and miR-21 modulates the PTEN protein levels and the CS and CSL phenotypes, irrespective of the patient's mutation status, and support their roles as genetic modifiers in CS and CSL.

What's in a cancer syndrome? Genes, phenotype and pathology

Syndromes are characterised by a group of specific signs and symptoms. This review aims to provide an overview of cancer syndromes and sheds light on possible roles for general health professionals in relation to their abilities to identify patients with cancer syndromes and therefore to refer such patients to specialists.

t-Darpp promotes cancer cell survival by up-regulation of Bcl2 through Akt-dependent mechanism

t-Darpp is a cancer-related truncated isoform of Darpp-32 (dopamine and cyclic-AMP-regulated phosphoprotein of M(r) 32,000). We detected overexpression of t-Darpp mRNA in two thirds of gastric cancers compared with normal samples (P = 0.004). Using 20 micromol/L ceramide treatment as a model for induction of apoptosis in AGS cancer cells, we found that expression of t-Darpp led to an increase in Bcl2 protein levels and blocked the activation of caspase-3 and caspase-9. The MitoCapture mitochondrial apoptosis and cytochrome c release assays indicated that t-Darpp expression enforces the mitochondrial transmembrane potential and protects against ceramide-induced apoptosis. Interestingly, the expression of t-Darpp in AGS cells led to >or=2-fold increase in Akt kinase activity with an increase in protein levels of p-Ser(473) Akt and p-Ser(9) GSK3 beta. These findings were further confirmed using tetracycline-inducible AGS cells stably expressing t-Darpp. We also showed transcriptional up-regulation of Bcl2 using the luciferase assay with Bcl2 reporter containing P1 full promoter, quantitative reverse transcription-PCR, and t-Darpp small interfering RNA. The Bcl2 promoter contains binding sites for cyclic AMP-responsive element binding protein CREB/ATF1 transcription factors and using the electrophoretic mobility shift assay with a CREB response element, we detected a stronger binding in t-Darpp-expressing cells. The t-Darpp expression led to an increase in expression and phosphorylation of CREB and ATF-1 transcription factors that were required for up-regulating Bcl2 levels. Indeed, knockdown of Akt, CREB, or ATF1 in t-Darpp-expressing cells reduced Bcl2 protein levels. In conclusion, the t-Darpp/Akt axis underscores a novel oncogenic potential of t-Darpp in gastric carcinogenesis and resistance to drug-induced apoptosis.

Expression of PTEN protein in patients with laryngeal squamous cell carcinoma

OBJECTIVE

PTEN (phosphatase and tensin homologue deleted on chromosome 10), also referred to as MMAC1 (mutated in multiple advanced cancers) gene was recently identified as a putative tumor suppressor in a variety of malignant tumors. PTEN expression has been investigated in some squamous cell carcinomas (SCC) of head and neck. However, there is only little knowledge about laryngeal malignancies. Therefore, we examined PTEN product protein immunohistochemically in 30 consecutive laryngeal specimens from patients with laryngeal SCC and compared the results according to the clinicopathologic characteristics of the patients.

METHOD

Surgical resection specimens of patients with laryngeal SCC were stained for PTEN protein using a primary rabbit polyclonal anti-PTEN antibody. Standard avidin-biotin immunohistochemical analysis was used to process the sections. The extent and intensity of PTEN staining in the specimens were compared according to the age and sex of the patients and localization, differentiation, size and stage of the tumor.

RESULTS

Out of 30 tumoral specimens (23 glottic and 7 supraglottic) 22 showed decreased PTEN staining intensity compared to the adjacent normal tissue. The extent of cytoplasmic PTEN staining was significantly less in supraglottic tumors (p < 0.05). When characteristics of the patients were analyzed according to the extent of cytoplasmic PTEN staining no difference was observed according to age, sex, measure, differentiation, T or N status.

CONCLUSION

A significant decrease in the extent of PTEN staining was observed in supraglottic SCC. It could be worthwhile to test if PTEN expression is diminished in patients with more aggressive laryngeal tumors, with special attention to tumor localization in larger series.

RAS/ERK modulates TGFbeta-regulated PTEN expression in human pancreatic adenocarcinoma cells

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is rarely mutated in pancreatic cancers, but its regulation by transforming growth factor (TGF)-beta might mediate growth suppression and other oncogenic actions. Here, we examined the role of TGFbeta and the effects of oncogenic K-RAS/ERK upon PTEN expression in the absence of SMAD4. We utilized two SMAD4-null pancreatic cell lines, CAPAN-1 (K-RAS mutant) and BxPc-3 (WT-K-RAS), both of which express TGFbeta surface receptors. Cells were treated with TGFbeta1 and separated into cytosolic/nuclear fractions for western blotting with phospho-SMAD2, SMAD 2, 4 phospho-ATP-dependent tyrosine kinases (Akt), Akt and PTEN antibodies. PTEN mRNA levels were assessed by reverse transcriptase-polymerase chain reaction. The MEK1 inhibitor, PD98059, was used to block the downstream action of oncogenic K-RAS/ERK, as was a dominant-negative (DN) K-RAS construct. TGFbeta increased phospho-SMAD2 in both cytosolic and nuclear fractions. PD98059 treatment further increased phospho-SMAD2 in the nucleus of both pancreatic cell lines, and DN-K-RAS further improved SMAD translocation in K-RAS mutant CAPAN cells. TGFbeta treatment significantly suppressed PTEN protein levels concomitant with activation of Akt by 48 h through transcriptional reduction of PTEN mRNA that was evident by 6 h. TGFbeta-induced PTEN suppression was reversed by PD98059 and DN-K-RAS compared with treatments without TGFbeta. TGFbeta-induced PTEN expression was inversely related to cellular proliferation. Thus, oncogenic K-RAS/ERK in pancreatic adenocarcinoma facilitates TGFbeta-induced transcriptional down-regulation of the tumor suppressor PTEN in a SMAD4-independent manner and could constitute a signaling switch mechanism from growth suppression to growth promotion in pancreatic cancers.

Association of multiple vertebral hemangiomas and severe paraparesis in a patient with a PTEN hamartoma tumor syndrome. Case report

The PTEN hamartoma tumor syndrome, manifestations of which include Cowden disease and Bannayan-Riley-Ruvalcaba syndrome, is caused by various mutations of the PTEN gene located at 10q23. Its major criteria are macrocephaly and a propensity to develop breast and thyroid cancers as well as endometrial carcinoma. Minor diagnostic criteria include hamartomatous intestinal polyps, lipomas, fibrocystic disease of the breasts, and fibromas. Mutations of PTEN can also be found in patients with Lhermitte-Duclos disease (dysplastic gangliocytoma of the cerebellum). The authors report the case of a 17-year-old girl who had a severe cyanotic cardiac malformation for which surgery was not advised and a heterozygous missense mutation (c.406T>C) in exon 5 of PTEN resulting in the substitution of cysteine for arginine (p.Cysl36Arg) in the protein, which was also found in her mother and sister. The patient presented in the pediatric emergency department with severe spastic paraparesis. A magnetic resonance imaging study of the spine showed vertebral hemangiomas at multiple levels, but stenosis and compression were maximal at level T5-6. An emergency T5-6 laminectomy was performed. The decompression was extremely hemorrhagic because the rapid onset of paraparesis necessitated prompt treatment, and there was no time to perform preoperative embolization. The patient's postoperative course was uneventful with gradual recovery. This represents the first report of an association of a PTEN mutation and multiple vertebral angiomas. The authors did not treat the remaining angiomas because surgical treatment was contraindicated without previous embolization, which in itself would present considerable risk in this patient with congenital cyanotic heart disease.

Targeting phosphoinositide 3-kinase: moving towards therapy

Phosphoinositide 3-kinases (PI3K) orchestrate cell responses including mitogenic signaling, cell survival and growth, metabolic control, vesicular trafficking, degranulation, cytoskeletal rearrangement and migration. Deregulation of the PI3K pathway occurs by activating mutations in growth factor receptors or the PIK3CA locus coding for PI3Kalpha, by loss of function of the lipid phosphatase and tensin homolog deleted in chromosome ten (PTEN/MMAC/TEP1), by the up-regulation of protein kinase B (PKB/Akt), or the impairment of the tuberous sclerosis complex (TSC1/2). All these events are linked to growth and proliferation, and have thus prompted a significant interest in the pharmaceutical targeting of the PI3K pathway in cancer. Genetic targeting of PI3Kgamma (p110gamma) and PI3Kdelta (p110delta) in mice has underlined a central role of these PI3K isoforms in inflammation and allergy, as they modulate chemotaxis of leukocytes and degranulation in mast cells. Proof-of-concept molecules selective for PI3Kgamma have already successfully alleviated disease progress in murine models of rheumatoid arthritis and lupus erythematosus. As targeting PI3K moves forward to therapy of chronic, non-fatal disease, safety concerns for PI3K inhibitors increase. Many of the present inhibitor series interfere with target of rapamycin (TOR), DNA-dependent protein kinase (DNA-PK(cs)) and activity of the ataxia telangiectasia mutated gene product (ATM). Here we review the current disease-relevant knowledge for isoform-specific PI3K function in the above mentioned diseases, and review the progress of >400 recent patents covering pharmaceutical targeting of PI3K. Currently, several drugs targeting the PI3K pathway have entered clinical trials (phase I) for solid tumors and suppression of tissue damage after myocardial infarction (phases I,II).

Role of PTEN/PI3K pathway in endothelial cells

PTEN (phosphatase and tensin homologue deleted on chromosome 10) is an important tumour-suppressor gene that encodes a 3-phosphatase. The major substrate of PTEN is PIP(3) (phosphatidylinositol 3,4,5-trisphosphate) generated by the action of PI3Ks (phosphoinositide 3-kinases). Hereditary mutation of PTEN causes tumour-susceptibility diseases such as Cowden disease. We used the Cre-loxP system to generate an endothelial cell-specific mutation of PTEN in mice. Heterozygous mutation of PTEN in endothelial cells enhances postnatal neovascularization, including tumour angiogenesis necessary for tumour growth. This observation suggests that Cowden disease patients are not only at risk for additional tumorigenic mutations due to complete loss of PTEN function, but may also experience accelerated growth of incipient tumours due to enhanced angiogenesis. Homozygous mutation of Pten in murine endothelial cells impairs cardiovascular morphogenesis and is embryonic lethal due to endothelial cell hyperproliferation and impaired vascular remodelling. Additional homozygous mutation of p85alpha, the regulatory subunit of class IA PI3Ks, or p110gamma, the catalytic subunit of the sole class IB PI3K, led to a partial rescue of all phenotypes in our PTEN-deficient mice. Thus inhibition of the PI3K pathway, including the targeting of PI3Kgamma, may be an attractive therapeutic strategy for the treatment of various malignancies.

Cowden syndrome and Bannayan Riley Ruvalcaba syndrome represent one condition with variable expression and age-related penetrance: results of a clinical study of PTEN mutation carriers

BACKGROUND

The most commonly reported phenotypes described in patients with PTEN mutations are Bannayan-Riley-Ruvalcaba syndrome (BRRS), with childhood onset, macrocephaly, lipomas and developmental delay, and Cowden Syndrome (CS), an adult-onset condition recognised by mucocutaneous signs, with a risk of cancers, in particular those of the thyroid and breast. It has been suggested that BRRS and CS are the same condition, but the literature continues to separate them and seek a genotype-phenotype correlation.

OBJECTIVE

To study the clinical features of patients with known PTEN mutations and observe any genotype-phenotype correlation.

METHODS

In total, 42 people (25 probands and 17 non-probands) from 26 families of all ages with PTEN mutations were recruited through the UK clinical genetics services. A full clinical history and examination were undertaken.

RESULTS

We were unable to demonstrate a genotype-phenotype correlation. Furthermore, our findings in a 31-year-old woman with CS and an exon 1 deletion refutes previous reports that whole exon deletions are only found in patients with a BRRS phenotype.

CONCLUSION

Careful phenotyping gives further support for the suggestion that BRRS and CS are actually one condition, presenting variably at different ages, as in other tumour-suppressor disorders such as neurofibromatosis type 1. This has important counselling implications, such as advice about cancer surveillance, for children diagnosed with BRRS.

Immunohistochemical detection of phosphorylated Akt, PI3K, and PTEN in ameloblastic tumors

OBJECTIVE

To evaluate roles of the Akt signaling pathway in oncogenesis and cytodifferentiation of odontogenic tumors, expression of phosphorylated Akt (pAkt), PI3K, and PTEN was analyzed in ameloblastic tumors as well as in tooth germs.

METHODS

11 tooth germs, 40 ameloblastomas, and 5 malignant ameloblastic tumors were examined immunohistochemically with antibodies against pAkt, PI3K, and PTEN.

RESULTS

Immunoreactivity for pAkt, PI3K, and PTEN was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and ameloblastic tumors. The levels of immunoreactivity for pAkt and PI3K were slightly higher in ameloblastic tumors than in tooth germs. Plexiform ameloblastomas showed significantly higher expression of PI3K than follicular ameloblastomas, and PI3K immunoreactivity in ameloblastomas without cellular variation was significantly higher than that in acanthomatous ameloblastomas. The level of PTEN immunoreactivity was significantly lower in ameloblastomas than in tooth germs.

CONCLUSION

Expression of pAkt, PI3K, and PTEN in tooth germs and ameloblastic tumors suggests that these signaling molecules regulate cell survival and growth in normal and neoplastic odontogenic tissues by mediating growth factor signals. Increased expression of pAkt and PI3K and decreased expression of PTEN in ameloblastic tumors may participate in oncogenesis of odontogenic epithelium by activating the Akt signaling pathway.

Zebrafish pten genes have overlapping and non-redundant functions in tumorigenesis and embryonic development

In human cancer, PTEN (Phosphatase and TENsin homolog on chromosome 10, also referred to as MMAC1 and TEP1) is a frequently mutated tumor suppressor gene. We have used the zebrafish as a model to investigate the role of Pten in embryonic development and tumorigenesis. The zebrafish genome encodes two pten genes, ptena and ptenb. Here, we report that both Pten gene products from zebrafish are functional. Target-selected inactivation of ptena and ptenb revealed that Ptena and Ptenb have redundant functions in embryonic development, in that ptena-/- and ptenb-/- mutants did not show embryonic phenotypes. Homozygous single mutants survived as adults and they were viable and fertile. Double homozygous ptena-/-ptenb-/- mutants died at 5 days post fertilization with pleiotropic defects. These defects were rescued by treatment with the phosphatidylinositol-3-kinase inhibitor, LY294002. Double homozygous embryos showed enhanced cellular proliferation. In addition, cell survival was dramatically enhanced in embryos that lack functional Pten upon gamma-irradiation. Surprisingly, adult ptenb-/- zebrafish developed ocular tumors later in life, despite the expression of ptena in adult eyes. We conclude that whereas Ptena and Ptenb have redundant functions in embryonic development, they apparently do not have completely overlapping functions later in life. These pten mutant zebrafish represent a unique model to screen for genetic and/or chemical suppressors of Pten loss-of-function.

PTEN hamartomatous tumor syndromes (PHTS): rare syndromes with great relevance to common cancers and targeted drug development

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor gene located on chromosome 10q22-23 that negatively regulates the pro-survival PI3K/Akt/mTOR pathway by functioning as a lipid phosphatase. Signaling through this pathway promotes cellular transformation and survival as well as resistance to chemotherapy and radiation. Loss of PTEN function is commonly observed in human cancers through somatic mutation, hypermethylation, and/or enhanced degradation. PTEN hamartomatous tumor syndromes (PHTS) are a collection of rare clinical syndromes marked by germline PTEN loss. Compared to the general population, PHTS patients have an increased risk of developing certain cancers and can develop benign tumors in virtually any organ. These patients provide a unique opportunity to examine the role of PTEN in human tumorigenesis, as well as study genotype-phenotype relationships. Because these patients are at higher risk of developing malignancies and have no established medical therapies, early screening, surveillance, and preventive care are important issues. Inhibitors of the PI3K/Akt/mTOR pathway that are being developed as cancer therapeutics could provide new therapeutic options for these rare patients, and could be credentialed as pathway inhibitors prior to testing in the general oncology population.

Café au lait macules and juvénile polyps

Several hereditary and nonhereditary gastrointestinal tract polyposis syndromes exhibit extra-intestinal manifestations, including cutaneous findings. However, a lack of information exists regarding cutaneous features of juvenile polyposis. Our objective was to document the prevalence of cutaneous hyperpigmented lesions in children with juvenile polyposis coli or juvenile polyposis coli and their first degree relatives.Children seen in the gastroenterology practice at The Children's Hospital in Denver, Colorado with polyps (juvenile polyposis coli, sporadic juvenile polyps, and familial adenomatous polyposis coli) and their first degree relatives were invited to participate in the study. A comprehensive skin examination was performed on those who consented to participate. We found that 8 of 14 patients (eight with juvenile polyposis coli, four with juvenile polyposis, and two with familial adenomatous polyposis coli) had at least one café-au-lait macule, compared with three of 27 relatives (p=0.003).The prevalence of at least one café-au-lait macule in our patients (8/14 or 57.1%, CI: 28.9–82.3%) was significantly higher than the general population prevalence of 28.5% (p=0.023). However, if the two patients with familial adenomatous polyposis coli were excluded, the comparison with the general population prevalence did not reach statistical significance (p=0.095). The prevalence of multiple cafe´-au-lait macules in our patients (4/14 or 28.6%; CI:8.4–58.1%) was significantly higher than the general population prevalence of 5.2% (p ¼ 0.005). A notable finding was the presence of multiple café -au-lait macules in 4 of 12 juvenile polyposis coli/juvenile polyposis patients.Two patients with juvenile polyposis coli also had lentigines. In this selected case series, we observed single or multiple café-au-lait macules in a high proportion of children with the three types of polyps. Further studies are needed to assess a possible common pathway for hamartomatous polypsand café-au-lait macules.

Phosphatidylinositol-3-OH kinase or RAS pathway mutations in human breast cancer cell lines

Constitutive activation of the phosphatidylinositol-3-OH kinase (PI3K) and RAS signaling pathways are important events in tumor formation. This is illustrated by the frequent genetic alteration of several key players from these pathways in a wide variety of human cancers. Here, we report a detailed sequence analysis of the PTEN, PIK3CA, KRAS, HRAS, NRAS, and BRAF genes in a collection of 40 human breast cancer cell lines. We identified a surprisingly large proportion of cell lines with mutations in the PI3K or RAS pathways (54% and 25%, respectively), with mutants for each of the six genes. The PIK3CA, KRAS, and BRAF mutation spectra of the breast cancer cell lines were similar to those of colorectal cancers. Unlike in colorectal cancers, however, mutational activation of the PI3K pathway was mutually exclusive with mutational activation of the RAS pathway in all but 1 of 30 mutant breast cancer cell lines (P = 0.001). These results suggest that there is a fine distinction between the signaling activators and downstream effectors of the oncogenic PI3K and RAS pathways in breast epithelium and those in other tissues.

PTEN regulates phospholipase D and phospholipase C

PTEN is an ubiquitously expressed tumor suppressor which plays a prominent role in the pathogenesis of many types of sporadic solid tumors, including breast cancer, as well as hematologic malignancies. Germline PTEN mutations cause 85% of Cowden syndrome (CS), characterized by a high risk of breast and thyroid cancers, and 65% of Bannayan-Riley-Ruvalcaba syndrome (BRRS), characterized by lipomatosis, hemangiomas and speckled penis. Historically, PTEN's role in tumor suppression has been linked to the down-regulation of the PI3K/AKT pathway by PTEN's lipid phosphatase activity. Beyond the AKT pathway, however, there has been minimal examination of PTEN's responsibility in lipid-derived cellular signaling. As phospholipids have been shown to be critical components in signal transduction and cellular proliferation and PTEN controls cellular phospholipid levels, we hypothesized that PTEN functions as a regulator of lipid signaling and homeostasis. Increased PTEN expression in unstimulated MCF-7 breast cancer cells results in a 51% increase in phosphatidic acid, with a decrease in phosphatidylcholine, suggesting that PTEN may regulate phospholipase D (PLD). PTEN overexpression results in a 30% increase in basal PLD activity. As phospholipase C (PLC) is both involved in PLD activation and is regulated by PIP2/3 levels, we investigated the role of PTEN on PLC activation. Our data suggest that PTEN modulates PLC:PLD activation pathways and indicate that the pathogenesis of CS/BRRS has a more complex biochemical basis beyond simply activating the PI3K pathway. This provides alternative routes for PTEN's tumor suppressor action that may be beneficial in the creation of novel targets for cancer therapy and prevention.

Cancer phenomics: RET and PTEN as illustrative models

Cancer phenomics, the systematic acquisition and objective documentation of host and/or somatic cancer phenotypic data at many levels, is a young field compared with other molecular-based 'omics'. Two relatively advanced phenomic paradigms are associated with phosphatase and tensin homologue (PTEN) and rearranged during transfection (RET), genes that are associated with cancer predisposition syndromes in addition to developmental disorders. The phenomic characterization of PTEN and RET underscores the importance of incorporating robust phenomics into the host 'omic' profile, and shows that the evolution of phenomics will be crucial to the advancement of personalized medicine.

Analysis of PTEN mutation in non-familial pheochromocytoma

PTEN, a tumor suppressor gene, is frequently mutated in a variety of human tumors. In mice, monoallelic inactivation of this gene predisposes animals to neoplasia of multiple organs. Interestingly, Pten heterozygous mice develop bilateral hyperplasia of the adrenal medulla. In this report we demonstrate that these neoplasms are hormonally active pheochromocytomas that secrete increased amounts of bioactive catecholamines: norepinephrine and epinephrine. To test a possibility that PTEN might be one of the genes responsible for human sporadic pheochromocytoma, we performed mutation analysis of DNA obtained from tumors of 29 patients. However, direct sequencing of all nine exons of the PTEN gene, including the splice junctions, revealed no mutations. Examination of protein expression by immunohistochemistry using 8 normal adrenals and 11 sporadic pheochromocytomas showed no decrease in the PTEN protein expression in the tumor tissue, but upregulation of insulin-like growth factor II, a peptide implicated in growth of adrenal tissue, was observed in four cases (36%).

PTEN c.511C>T nonsense mutation in a BRRS family disrupts a potential exonic splicing enhancer and causes exon skipping

Bannayan-Riley-Ruvalcaba syndrome (BRRS) is an autosomal dominant disorder characterized by macrocephaly, intestinal hamartomatous polyps, lipomas and pigmented macules of the glans penis. We identified a Thai family affected with BRRS. In addition to typical manifestations of BRRS, the proband has a large hepatic AVM which is rarely found in BRRS. The molecular analysis revealed affected members were heterozygous for an exon skipping-associated nonsense mutation c.511C>T in the PTEN gene. The mutation was previously assumed to be deleterious by causing a change to a termination codon, Q171X. We, herein, found that another pathogenic effect was splicing related by disrupting a potential exonic splicing enhancer (ESE) and causing an entire exon 6 skipping. The results prompted us to investigate other reported missense/nonsense mutations in the PTEN gene. We found that they do not colocalize with ESE sites, suggesting that most of their pathogenic effects are not through ESE disruption.

Cancer-associated genodermatoses: a personal history

Cancer-associated genodermatoses are a group of genetic disorders inherited in an autosomal-dominant fashion in which unique cutaneous findings are a reliable marker for the risk of developing internal malignancies. The historical, clinical and dermatopathological aspects of basal cell nevus syndrome, Muir-Torre syndrome, Cowden syndrome, Carney complex and Birt-Hogg-Dubé syndrome are reviewed in a personal and informal fashion. The latest advances in the molecular genetics of the disorders are also summarized.

Cutaneous lipoma in children: 5 cases with Bannayan-Riley-Ruvalcaba syndrome

Cutaneous lipoma is rare in children, but it can be part of a syndrome such as the Bannayan-Riley-Ruvalcaba syndrome (BRRS). The BRRS is a dominant autosomal disorder characterized by cutaneous lipomas, macrocephaly, intestinal polyps, and developmental delay associated with PTEN gene mutations. This syndrome is thought to represent a pediatric form of the Cowden syndrome, characterized among other features by an increased risk of cancer. We report 5 cases of BRRS, all diagnosed in children with lipoma and macrocephaly. Children presenting with lipomas need a complete physical examination to look for other signs of BRRS, because they may need further follow-up for tumor screening in adulthood.

Mutation of the PI3' kinase gene in a human colon carcinoma cell line, HCC2998

HCC2998 is a highly differentiated human colon carcinoma cell line, which has been shown to be converted to a poorly differentiated one after expression of a constitutively active phosphatidylinositol 3-kinase (PI3' kinase). These cells express aberrant sizes of a regulatory subunit of PI3' kinase, p85alpha, with molecular weights of 50 and 76 kDa at a very low level. To elucidate how these cells express these proteins, we analyzed mutations within the p85alpha gene. DNA sequencing analysis revealed that these mutant proteins were generated by independent point mutations in the two alleles of the p85alpha gene: one in the coding sequence, and the other in the acceptor sequence for splicing. Introduction of wild-type p85alpha into HCC2998 cells induced slight rounding of the cells and enhancement of mucin secretion. At the same time, a membrane receptor, ErbB3, was phosphorylated on tyrosine, which in turn, binds to PI3' kinase. Since ErbB3 is upstream of PI3' kinase, it is likely that there is an autocrine loop in which PI3' kinase is activated by ErbB3, which may contribute to dedifferentiation of the cells.

Effects of cotransfection of antisense-EGFR and wild-type PTEN cDNA on human glioblastoma cells

The main molecular genetic changes identified in glioblastomas are overexpression/amplification of the epidermal growth factor receptor (EGFR) gene and mutation/ deletion of the tumor suppressor PTEN gene. These two genetic changes both play important roles in glial tumorigenesis and progression. In this study, we demonstrated that wild-type PTEN transfection inhibited the growth and transforming ability of U87MG cells by 69.3% and 73.5%, respectively. On the other hand, antisense-EGFR transfection inhibited the growth and transforming phenotype of these cells by 50.3% and 46.8%, respectively. However, cotransfection of U87MG cells with wild-type PTEN and antisense EGFR constructs could inhibit the cellular growth by 91.7%. The transforming phenotype of these cells was completely inhibited. In addition, these cotransfected cells showed a differentiated form and expressed much lower telomerase activity than cells transfected with wild-type PTEN or antisense-EGFR alone. In summary, these results suggest that cotransfection is a better approach to suppress glioma cell growth than wild-type PTEN transfer or antisense-EGFR transfection alone. This approach may prove useful as an adjunct therapy in the treatment of glioblastomas.

Clinical Implications of Our Advancing Knowledge of Colorectal Cancer Genetics: Inherited Syndromes, Prognosis, Prevention, Screening and Therapeutics

Recent genetic advances in our knowledge of colorectal cancer genetics are beginning to pay translational dividends in the management of this common clinical problem. We are now able to accurately screen and counsel individuals at risk of rare inherited cancer syndromes. We have recently introduced two of what are sure to be numerous biologic-based therapies, and have shown that colorectal neoplasia risk can be modestly reduced by various chemopreventative agents. Finally, our advancing knowledge has led to significant inroads into understanding what genetic alterations define prognosis and predict response to specific chemotherapeutic agents, and we are beginning to explore the utility of this knowledge in mass genetic-based clinical screening efforts. Enthusiasm must be tempered, however, by the extraordinary cost that often accompanies relatively modest gains. Finally, although genetic-based therapy often receives the greatest attention, molecular genetics, will likely have the greatest cost-effective impact in primary prevention and early diagnosis.

Targeting the PTPome in human disease

Protein tyrosine phosphatases (PTPs) play vital roles in numerous cellular processes and are implicated in a growing number of human diseases, ranging from cancer to cardiovascular, immunological, infectious, neurological and metabolic diseases. There are at least 107 genes in the human genome, collectively referred to as the human 'PTPome'. Here the authors review the involvement of PTPs in human disease, discuss their potential as drug targets, and current efforts to develop PTP inhibitors for the treatment of human disease. Finally, the authors present their view of the future for PTPs as drug targets.

Lipid phosphatases as a possible therapeutic target in cases of type 2 diabetes and obesity

Phosphatidyl inositol 3-kinase (PI3-kinase) functions as a lipid kinase to produce PI(3,4,5)P(3) from PI(4,5)P(2) in vivo. PI(3,4,5)P(3) is crucial as a lipid second messenger in various metabolic effects of insulin. Lipid phosphatases, src homology 2 domain containing inositol 5'-phosphatase 2 (SHIP2) and skeletal muscle and kidney-enriched inositol phosphatase (SKIP) hydrolyze PI(3,4,5)P(3) to PI(3,4)P(2) and phosphatase and tensin homolog deleted on chromosome ten (PTEN) hydrolyzes PI(3,4,5)P(3) to PI(4,5)P(2). SHIP2 negatively regulates insulin signaling relatively specifically via its 5'-phosphatase activity. Targeted disruption of the SHIP2 gene in mice resulted in increased insulin sensitivity and conferred protection from obesity induced by a high-fat diet. Polymorphisms in the human SHIP2 gene are associated, at least in part, with the insulin resistance of type 2 diabetes. Importantly, inhibition of endogenous SHIP2 through the liver-specific expression of a dominant-negative SHIP2 improves glucose metabolism and insulin resistance in diabetic db/db mice. Overexpression of PTEN and SKIP also inhibited insulin-induced phosphorylation of Akt and the uptake of glucose in cultured cells. Although a homozygous disruption of the PTEN gene in mice results in embryonic lethality, either skeletal muscle or adipose tissue-specific disruption of PTEN ameliorated glucose metabolism without formation of tumors in animal models of diabetes. The role of SKIP in glucose metabolism remains to be further clarified in vivo. Taken together, inhibition of endogenous SHIP2 in the whole body appears to be effective at improving the insulin resistance associated with type 2 diabetes and/or obesity. Inhibition of PTEN in the tissues specifically targeted, including skeletal muscle and fat, may result in an amelioration of insulin resistance in type 2 diabetes, although caution against the formation of tumors is needed.

Mutation screening and association study of the candidate prostate cancer susceptibility genes MSR1, PTEN, and KLF6

BACKGROUND

MSR1, PTEN, and KLF6 have been implicated as candidate susceptibility genes for prostate tumorigenesis.

METHODS

Three hundred Jewish prostate cancer patients were screened for alterations in these genes.

RESULTS

MSR1 was conserved in all patients. PTEN screening revealed a novel missense mutation and a silent change. Five KLF6 alterations were detected in 17 patients, including Q160X, the only nonsense KLF6 germline mutation described to date in a cancer patient. The KLF6 IVS1-27G>A polymorphism, recently associated with prostate cancer risk, was detected in 11.9% of the patients and 17.3% of the controls (P = 0.043). IVS1-27A allele frequency was significantly lower in prostate cancer patients (P = 0.030), specifically in Ashkenazi patients (P = 0.047) compared to controls.

CONCLUSIONS

We found no evidence that MSR1 and PTEN germline mutations are associated with prostate cancer risk in Jews. The negative association between KLF6 IVS1-27A and prostate cancer risk supports a population-specific effect of susceptibility alleles in prostate tumorigenesis.

Cellular and molecular regulation of hematopoietic and intestinal stem cell behavior

Two fundamental questions in stem cell research are what controls stem cell number in vivo and which signal pathways regulate self-renewal. Here we summarize our recent studies regarding the role of BMP signaling in regulation of stem cell behavior in both the hematopoietic and intestinal systems. These studies provide evidence to show that BMP signaling plays an important role in controlling stem cell number, at least in these two stem cell compartments. However, the BMP signal utilizes different mechanisms to fulfill this purpose: in the hematopoietic stem cell compartment it controls stem cell number through regulation of the niche size; in the intestinal stem cell compartment it directly controls self-renewal of stem cells through restriction of Wnt/beta-catenin activity. The Bmpr1a mutant mouse provided an elegant model which allowed us to identify the HSC niche, an enigma for more than 25 years. Our work provided more evidence to demonstrate the essential function of the niche in maintenance of stem cells and showed that multiple signals are required to maintain a balanced control of stem cell self-renewal.

Impact of loss of heterozygosity of encoding phosphate and tensin homolog on the prognosis of gastric cancer

BACKGROUND AND AIM

Encoding phosphate and tensin homolog (PTEN) is a cancer suppressor gene and it has been assumed that gene mutation and loss of heterozygosity (LOH) occurs frequently in various types of carcinoma. However, the role of LOH of PTEN and its outcome variables in gastric cancer have not been well established. In the present study, we investigated the roles of PTEN, LOH and their outcomes.

METHODS

Fresh frozen tumor samples from 119 gastric cancer patients with a primary diagnosis of gastric carcinoma were evaluated for LOH of PTEN using an automated sequencer. Results were compared with pathological parameters. The median follow-up period was 559 days.

RESULTS

Loss of heterozygosity of PTEN was observed in 17.1% of patients (13/76) diagnosed with gastric cancer. No particular relationship was found with any clinicopathological factor. However, the prognosis of patients with LOH of PTEN was significantly poor. Multivariate analyses revealed that vascular invasion, invasion depth, LOH of PTEN, histology and lymph node metastasis were correlated with survival of the patient.

CONCLUSIONS

Even though mutation of PTEN in gastric cancer has rarely been reported, according to our findings, LOH of PTEN frequently occurs in gastric cancers and is correlated with disease-related deaths. The LOH of PTEN is an independent prognostic factor and PTEN is a candidate as a haploinsufficient tumor suppressor in gastric cancers.

PTEN couples Sema3A signalling to growth cone collapse

Distinct changes in glycogen synthase kinase-3 (GSK-3) signalling can regulate neuronal morphogenesis including the determination and maintenance of axonal identity, and are required for neurotrophin-mediated axon elongation. In addition, we have previously shown a dependency on GSK-3 activation in the semaphorin 3A (Sema3A)-mediated growth-cone-collapse response of sensory neurons. Regulation of GSK-3 activity involves the intermediate signalling lipid phosphatidylinositol 3,4,5-trisphosphate, which can be modulated by phosphatidylinositol 3-kinase (PI3K) and the tumour suppressor PTEN. We report here the involvement of PTEN in the Sema3A-mediated growth cone collapse. Sema3A suppresses PI3K signalling concomitant with the activation of GSK-3, which depends on the phosphatase activity of PTEN. PTEN is highly enriched in the axonal compartment and the central domain of sensory growth cones during axonal extension, where it colocalises with microtubules. Following exposure to Sema3A, PTEN accumulates rapidly at the growth cone membrane suggesting a mechanism by which PTEN couples Sema3A signalling to growth cone collapse. These findings demonstrate a dependency on PTEN to regulate GSK-3 signalling in response to Sema3A and highlight the importance of subcellular distributions of PTEN to control growth cone behaviour.

PTEN autoregulates its expression by stabilization of p53 in a phosphatase-independent manner

PTEN (phosphatase and tensin homologue, deleted on chromosome 10) is a tumor suppressor with dual phosphatase activity and mutations of its gene, PTEN, have been associated with many sporadic cancers and heritable neoplasia syndromes, including Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome. However, accumulating evidence now shows that PTEN may have novel functions other than as a phosphatase. In the present study, we show that PTEN is able to autoregulate its expression through the stabilization of another tumor suppressor p53. We further show that PTEN enhances p53 transactivation, a relationship that requires the interaction between PTEN and p53 and is PTEN phosphatase independent. We show that cell lines from Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome patients with germ line PTEN promoter mutations in the vicinity of the p53-binding motifs have altered p53 regulation. This seems to be due to reduced PTEN stability and decreased PTEN-p53 interactions. Our data provide clues to better understand the regulation of PTEN expression and the possible mechanisms of the pathogenesis of the subset of Cowden syndrome individuals with germ line promoter variation and who lack mutations in the PTEN coding region and splice sites. Importantly, this mechanism also holds for those sporadic tumors that lack intragenic mutations but have hemizygous deletion of PTEN, which includes the promoter region as manifested by loss-of-heterozygosity of 10q markers. The importance of our observations is underlined by the broad spectrum of neoplasias that harbor somatic PTEN or p53 alterations, or both.

PTEN levels in Alzheimer's disease medial temporal cortex

Phosphatase and tensin homologue deleted from chromosome 10 (PTEN) is a dual (protein tyrosine and lipid) phosphatase one of the functions of which is to dephosphorylate phosphatidylinositol 3,4,5-trisphosphate to phosphatidylinositol-3,4-biphosphate thereby inhibiting phosphoinositide-dependent kinase activation of the cell survival kinase Akt. Akt activity is up regulated in Alzheimer's disease (AD) brain in parallel to the progression of neurofibrillary pathology. The present study determined whether altered expression of PTEN occurs in Alzheimer's disease brain. Western immunoblotting revealed no significant changes of PTEN protein levels in nuclear and membrane fractions of medial temporal cortex from a series of Alzheimer's disease and control cases. Similarly, no changes in PTEN protein levels, as determined by dot-blotting, were seen in temporal cortex homogenates from a separate series of Alzheimer's disease and control brains. A small but significant decrease in the levels of Ser(380) p-PTEN was seen in homogenates of Alzheimer's disease temporal cortex. Immunohistochemistry revealed PTEN immunoreactivity in a number of brain structures including neurons, capillaries and structures resembling oligodendrocytes and astrocytes. The majority of temporal cortex pyramidal neurons (93-100%) were PTEN immunopositive. The Alzheimer's disease cases had significantly lower numbers of total ( approximately 12% loss, P<0.02) and PTEN immunopositive ( approximately 15% loss, P<0.01) pyramidal neurons as compared to the control cases.

Molecular changes in prostatic cancer

Prostate cancer is one of the most commonly diagnosed and potentially devastating cancers in men, throughout the world. However, the clinical manifestation of this disease varies greatly, from indolent tumours, requiring little or no treatment, to those aggressive cancers which require radical therapies. Prostate cancer, like all other cancers, develops and progresses as a consequence of an accumulation of genetic changes. While several putative genes have been isolated for the development of breast, ovarian and colon cancer, the aetiology and pathogenesis of prostate cancer remains poorly understood. In this review, we discuss important genetic markers in early, metastatic and hormone refractory prostate cancer which may, in the future, be used as markers for diagnosis and prognosis, as well as targets for therapeutic intervention.

Akt-regulated pathways in prostate cancer

Prostate cancer remains a major cause of cancer-related mortality. Genetic clues to the molecular pathways driving the most aggressive forms of prostate cancer have been limited. Genetic inactivation of PTEN through either gene deletion or point mutation is reasonably common in metastatic prostate cancer and the resulting activation of phosphoinostide 3-kinase, AKT and mTOR provides a major therapeutic opportunity in this disease as mTOR inhibitors, HSP90 inhibitors and PI3K inhibitors begin to enter clinical development.

Ptena and ptenb genes play distinct roles in zebrafish embryogenesis

PTEN is a tumor suppressor gene associated with multiple tumor types. PTEN function is essential for early embryonic development and is involved in the regulation of cell size, number, and survival. By dephosphorylating PIP(3), PTEN normally acts to inhibit the PI3-Kinase/AKT pathway. Here we have identified two zebrafish orthologs, ptena and ptenb, of the single mammalian PTEN gene and analyzed the role of these genes in zebrafish development. Ptena transcripts were expressed throughout the embryo at early somitogenesis. By 24 hpf, expression was predominant in the central nervous system, axial vasculature, retina, branchial arches, ear, lateral line primordium, and pectoral fin bud. Ptenb was also ubiquitously expressed early in somitogenesis, but transcripts became more restricted to the somites and central nervous system as development progressed. By 48 hpf, ptena and ptenb were expressed predominantly in the central nervous system, branchial arches, pectoral fins, and eye. Antisense morpholinos were used to knock down translation of ptena and ptenb mRNA in zebrafish embryos. Knockdown of either pten gene caused increased levels of phosphorylated Akt in morphant embryos, indicating that Ptena and Ptenb each possess PIP(3) lipid phosphatase activity. Ptena morphants had irregularities in notochord shape (73%), vasculogenesis (83%), head shape (72%), and inner ear development (59%). The most noticeable defects in ptenb morphants were upward hooked tails (73%), domed heads (83%), and reduced yolk extensions (90%). These results indicate that ptena and ptenb encode functional enzymes and that each pten gene plays a distinct role during zebrafish embryogenesis.

The Akt of translational control

The oncogene AKT (also called protein kinase B (PKB)) signals to the translational machinery, and activation of protein synthesis by Akt is associated with cancer formation. Akt directly stimulates the activity of translation initiation factors and upregulates ribosome biogenesis. Activation of protein synthesis by Akt is phylogenetically conserved from Drosophila to humans, and is important for regulating cell growth, proliferation and cell survival. Consequently, translation defects due to aberrant Akt activation may be a crucial mechanism leading to tumorigenesis. However, few in vivo studies have established a causative role for aberrant protein synthesis control in cancer. A major challenge in the future will be to identify the specific mRNAs regulated at the level of translation control directly relevant for cellular transformation. In this review, we highlight and discuss the emerging molecular and genetic evidence that support a model by which deregulation of specific or global protein synthesis contributes to cancer.

Akt phosphorylation associates with LOH of PTEN and leads to chemoresistance for gastric cancer

Growth factor receptor-mediated signal transduction has been implicated in conferring resistance to conventional chemotherapy on cancer cells. We describe a pathway that involves AKT/PI3K to mediate chemoresistance in gastric cancer patients. Primary gastric carcinoma tissues and corresponding normal mucosa were obtained from 76 gastric cancer patients who underwent surgery in the Department of Surgery II in Kyushu University Hospital from the years 1996-2000. AKT activation was investigated by immunostaining with a phosphorylation-specific antibody, and LOH (loss of heterozygosity) of PTEN was studied in the same samples. AKT was phosphorylated in 22 cases (28.9%) of gastric cancer cases. AKT and phosphorylated AKT were not correlated with any clinicopathological factor. We found that the gastric cancer patients who had higher AKT phosphorylation (activated AKT) seemed to have LOH of PTEN (p = 0.0008). When the chemotherapeutic sensibilities of these patients were studied in an MTT assay, it was found that the activated AKT was associated with increased resistance to multiple chemotherapeutic agents (5-fluorouracil, adriamycin, mitomycin C and cis-platinum). The results of our study indicate that AKT activation and LOH of PTEN plays an important role in conferring a broad-spectrum chemoresistance in gastric cancer patients. It also indicates that AKT may therefore be a novel molecular target for therapies or chemosensitivity tests that improve the outcomes of gastric cancer patients.

Targeted biallelic inactivation of Pten in the mouse prostate leads to prostate cancer accompanied by increased epithelial cell proliferation but not by reduced apoptosis

The PTEN tumor suppressor gene is frequently inactivated in human tumors, including prostate cancer. Based on the Cre/loxP system, we generated a novel mouse prostate cancer model by targeted inactivation of the Pten gene. In this model, Cre recombinase was expressed under the control of the prostate-specific antigen (PSA) promoter. Conditional biallelic and monoallelic Pten knock-out mice were viable and Pten recombination was prostate-specific. Mouse cohorts were systematically characterized at 4 to 5, 7 to 9, and 10 to 14 months. A slightly increased proliferation rate of epithelial cells was observed in all prostate lobes of monoallelic Pten knock-out mice (PSA-Cre;Pten-loxP/+), but minimal pathologic changes were detected. All homozygous knock-out mice (PSA-Cre;Pten-loxP/loxP) showed an increased size of the luminal epithelial cells, large areas of hyperplasia, focal prostate intraepithelial neoplasia lesions and an increased prostate weight at 4 to 5 months. More extensive prostate intraepithelial neoplasia and focal microinvasion occurred at 7 to 9 months; invasive prostate carcinoma was detected in all male PSA-Cre;Pten-loxP/loxP mice at 10 to 14 months. At 15 to 16 months, a rare lymph node metastasis was found. In hyperplastic cells and in tumor cells, the expression of phospho-AKT was up-regulated. In hyperplastic and tumor cells, expression of luminal epithelial cell cytokeratins was up-regulated; tumor cells were negative for basal epithelial cell cytokeratins. Androgen receptor expression remained detectable at all stages of tumor development. The up-regulation of phospho-AKT correlated with an increased proliferation rate of the epithelial cells, but not with a reduced apoptosis.

Activation of AKT kinases in cancer: implications for therapeutic targeting

The AKT1, AKT2, and AKT3 kinases have emerged as critical mediators of signal transduction pathways downstream of activated tyrosine kinases and phosphatidylinositol 3-kinase. An ever-increasing list of AKT substrates has precisely defined the multiple functions of this kinase family in normal physiology and disease states. Cellular processes regulated by AKT include cell proliferation and survival, cell size and response to nutrient availability, intermediary metabolism, angiogenesis, and tissue invasion. All these processes represent hallmarks of cancer, and a burgeoning literature has defined the importance of AKT alterations in human cancer and experimental models of tumorigenesis, continuing the legacy represented by the original identification of v-Akt as the transforming oncogene of a murine retrovirus. Many oncoproteins and tumor suppressors intersect in the AKT pathway, finely regulating cellular functions at the interface of signal transduction and classical metabolic regulation. This careful balance is altered in human cancer by a variety of activating and inactivating mechanisms that target both AKT and interrelated proteins. Reprogramming of this altered circuitry by pharmacologic modulation of the AKT pathway represents a powerful strategy for rational cancer therapy. In this review, we summarize a large body of data, from many types of cancer, indicating that AKT activation is one of the most common molecular alterations in human malignancy. We also review mechanisms of activation of AKT kinases, examples of therapeutic modulation of the AKT pathway in animal models, and the current status of efforts to target molecular components of the AKT pathway for cancer therapy and, possibly, cancer prevention.

Analysis of PTEN gene mutations in Korean patients with Cowden syndrome and polyposis syndrome

PURPOSE

PTEN (phosphatase and tensin homologue deleted in chromosome 10) is a candidate tumor suppressor gene. Mutations of this gene are responsible for PTEN hamartoma tumor syndromes, including Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus -like syndromes. Recently, PTEN mutations were identified in several human neoplasms. We analyzed the DNA of various organs and lesions in Korean patients with Cowden syndrome, their family members, and patients with familial adenomatous polyposis for germline or somatic PTEN mutations.

METHODS

The 11 patients included in this study were 5 patients with Cowden syndrome, 4 of their family members, and 2 patients with familial adenomatous polyposis. Deletions and mutations in exons 1 to 9 of the PTEN gene were evaluated by polymerase chain reaction-single strand conformation polymorphism and sequencing analysis in esophageal acanthosis, gastric polyps, colonic polyps, skin lesions, and peripheral blood mononuclear cells. To exclude common polymorphisms, 240 controls were tested.

RESULTS

All patients with Cowden syndrome showed several to numerous polyps in the gastrointestinal tract. A missense mutation at codon 217 (GTC to GAC, Val to Asp) in exon 7 was identified in one Cowden syndrome patient, and a nonsense mutation at codon 211 (TGC to TGA, Cys to stop) in exon 6 was identified in a second patient. Identical mutations were found in all tissue samples, including colonic polyps, from each patient. No PTEN mutations were found in their family members or in any patient with familial adenomatous polyposis. None of tested controls contained a mutation.

CONCLUSIONS

We have identified two new germline PTEN mutations in Korean patients with Cowden syndrome. Mutations in the introns and regulatory regions of the PTEN gene may be present in additional patients with Cowden syndrome and polyposis syndrome.

PED Mediates AKT-Dependent Chemoresistance in Human Breast Cancer Cells

Killing of tumor cells by cytotoxic therapies, such as chemotherapy or gamma-irradiation, is predominantly mediated by the activation of apoptotic pathways. Refractoriness to anticancer therapy is often due to a failure in the apoptotic pathway. The mechanisms that control the balance between survival and cell death in cancer cells are still largely unknown. Tumor cells have been shown to evade death signals through an increase in the expression of antiapoptotic molecules or loss of proapoptotic factors. We aimed to study the involvement of PED, a molecule with a broad antiapoptotic action, in human breast cancer cell resistance to chemotherapeutic drugs-induced cell death. We show that human breast cancer cells express high levels of PED and that AKT activity regulates PED protein levels. Interestingly, exogenous expression of a dominant-negative AKT cDNA or of PED antisense in human breast cancer cells induced a significant down-regulation of PED and sensitized cells to chemotherapy-induced cell death. Thus, AKT-dependent increase of PED expression levels represents a key molecular mechanism for chemoresistance in breast cancer.

Biomedicine and diseases: the Klippel-Trenaunay syndrome, vascular anomalies and vascular morphogenesis

Vascular morphogenesis is a vital process for embryonic development, normal physiologic conditions (e.g. wound healing) and pathological processes (e.g. atherosclerosis, cancer). Genetic studies of vascular anomalies have led to identification of critical genes involved in vascular morphogenesis. A susceptibility gene, VG5Q (formally named AGGF1), was cloned for Klippel-Trenaunay syndrome (KTS). AGGF1 encodes a potent angiogenic factor, and KTS-associated mutations enhance angiogenic activity of AGGF1, defining 'increased angiogenesis' as one molecular mechanism for the pathogenesis of KTS. Similar studies have identified other genes involved in vascular anomalies as important genes for vascular morphogenesis, including TIE2, VEGFR-3, RASA1, KRIT1, MGC4607, PDCD10, glomulin, FOXC2, NEMO, SOX18, ENG, ACVRLK1, MADH4, NDP, TIMP3, Notch3, COL3A1 and PTEN. Future studies of vascular anomaly genes will provide insights into the molecular mechanisms for vascular morphogenesis, and may lead to the development of therapeutic strategies for treating these and other angiogenesis-related diseases, including coronary artery disease and cancer.