Germline mutations of the PTEN gene in Cowden disease, an inherited breast and thyroid cancer syndrome

Mapping of a gene predisposing to familial thyroid tumors with cell oxyphilia to chromosome 19 and exclusion of JUN B as a candidate gene

BACKGROUND

Familial nonmedullary thyroid carcinoma (FNMTC) is a clinical entity characterized by a more aggressive phenotype than the sporadic counterpart. The transmission of susceptibility of FNMTC is compatible with autosomal dominant inheritance. We report the identification of a new entity of FNMTC and the mapping of the responsible gene named TCO (for thyroid tumor with cell oxyphilia).

METHODS

In one family, multinodular goiters were diagnosed in six individuals and papillary thyroid carcinoma was diagnosed in three. Eight patients were operated on. Blood samples were collected from the nine affected patients and from eight unaffected relatives. The gene was mapped by linkage analysis with a whole-genome panel of microsatellite markers.

RESULTS

The neoplastic cells from all lesions showed characteristic faint to marked cytoplasmic oxyphilia. We found a logarithm of odd ratio (LOD) score of 2.41 at theta = 0 for marker D19S586. Additional markers were typed in the region and were found to be in linkage, with LOD scores peaking at markers D19S916 (Zmax = 3.01 at theta = 0) and D19S413 (Zmax = 2.95 at theta = 0). All these markers have been physically mapped to 19p13.2.

CONCLUSIONS

TCO was mapped to chromosome 19p13.2. Interestingly, both the benign and malignant thyroid tumors in this family exhibit some degree of oxyphilia, which has not been described until now in the familial forms of NMTC.

Germline mutations of p53 but not p16/CDKN2 or PTEN/MMAC1 tumor suppressor genes predispose to gliomas. The ANOCEF Group. Association des NeuroOncologues d'Expression Française

Constitutional DNA from 44 selected patients suspected of being genetically predisposed to develop astrocytic tumors was analyzed for germline mutations of the p53, p16, and PTEN genes. Six constitutional missense mutations of the p53 gene were identified (13.6%), but no mutations of the p16 and PTEN genes were found, suggesting that (1) germline p53 mutations contribute to a small portion of astrocytic tumors, (2) inherited mutations of the p16 and PTEN gene do not predispose to the development of gliomas, and (3) other genes are involved in glioma predisposition.

Thyroid pathologic findings in patients with Cowden disease

We describe the histologic findings in thyroid glands from six female and five male patients with Cowden disease. The patients were aged 9 to 43 years (mean age, 26 years). The salient thyroid lesions in this syndrome were multicentric follicular adenomas and adenomatous (parenchymatous, hyperplastic) nodules showing a wide range of nonspecific cytoarchitectural patterns. Multiple tiny cellular foci, so-called microadenomas, were also a feature. Specific lesions composed of oxyphil or clear cells, a tumor with features of hyalinizing trabecular adenoma, and an adenolipoma also occurred. Two cases showed a follicular carcinoma in addition to multiple benign follicular cell proliferations. The follicular carcinomas occurred at an older age and were larger in size than the clinically significant benign nodular lesions, suggesting tumor progression. All tumors showed thyroglobulin immunoreactivity and were negative for calcitonin. The histologic findings of a multiple adenomatous goiter or multiple follicular adenomas, particularly in children and young adults, should alert the pathologist and physician to the possibility of an inherited trait, such as Cowden disease, with its implications for family screening. The tumors are usually benign and well demarcated, but, because of multicentricity and increased risk of recurrence or progression to carcinoma, total thyroidectomy should be advocated.

Mutational analysis of the PTEN/MMAC1 gene in primary oesophageal squamous cell carcinomas

AIM

To investigate whether PTEN/MMAC1 mutations play a role in the carcinogenesis of oesophageal squamous cell carcinoma.

METHODS

A panel of 33 primary oesophageal squamous cell carcinoma tumour samples and 20 corresponding morphologically normal tissues was examined for mutations in all nine exons of the PTEN/MMAC1 gene by means of polymerase chain reaction single strand conformational polymorphism analysis (PCR-SSCP) and direct DNA sequencing methods.

RESULTS

Only one of 33 oesophageal squamous cell carcinomas showed an aberrant SSCP band. Further sequencing analysis of this sample revealed an 802 -29 T-->C substitution in intron 7. PTEN/MMAC1 mutations were not found in the mutational "hot spot" in exon 5, even after direct sequencing of six oesophageal squamous cell carcinoma samples and three normal tissues. However, a deletion of one nucleotide T at position 492 +8 in intron 5 was seen in all samples.

CONCLUSION

These results suggest that PTEN/MMAC1 mutations do not play a major role in the carcinogenesis of oesophageal squamous cell carcinoma.

Mutational spectra of PTEN/MMAC1 gene: a tumor suppressor with lipid phosphatase activity

PTEN/MMAC1 (phosphatase, tensin homologue/mutated in multiple advanced cancers) is a tumor suppressor protein that has sequence homology with dual-specificity phosphatases, which are capable of dephosphorylating both tyrosine phosphate and serine/threonine phosphate residues on proteins. The in vivo function of PTEN/MMAC1 appears to be dephosphorylation of phosphotidylinositol 3,4, 5-triphosphate. The PTEN/MMAC1 gene is mutated in the germline of patients with rare autosomal dominant cancer syndromes and in subsets of specific cancers. Here we review the mutational spectra of the PTEN/MMAC1 gene in tumors from various tissues, especially endometrium, brain, prostate, and ovary, in which the gene is inactivated very frequently. Germline and somatic mutations in the PTEN/MMAC1 gene occur mostly in the protein coding region and involve the phosphatase domain and poly(A)(6) stretches. Compared with germline alterations found in the PTEN/MMAC1 gene, there is a substantially increased frequency of frameshift mutations in tumors. Glioblastomas and endometrial carcinomas appear to have distinct mutational spectra, probably reflecting differences in the underlying mechanisms of inactivation of the PTEN/MMAC1 gene in the two tissue types. Also, depending on the tissue type, the gene appears to be involved in the initiation or the progression of cancers. Further understanding of PTEN/MMAC1 gene mutations in different tumors and the physiologic consequences of these mutations is likely to open up new therapeutic opportunities for targeting this critical gene.

PTEN gene and integrin signaling in cancer

Integrins are major adhesion- and signaling-receptor proteins that mediate cell migration and invasion. They also trigger a variety of signal transduction pathways and regulate cytoskeletal organization, specific gene expression, growth control, and apoptosis (programmed cell death). Consequently, integrins are thought to play important roles in embryonic development and in the biology of cancers. The functions of integrins can be negatively regulated by the recently discovered tumor suppressor PTEN, a protein with homology to protein tyrosine phosphatases and tensin. The PTEN gene is mutated in a wide range of human cancers. PTEN inhibits cell migration and invasion by directly dephosphorylating two key tyrosine-phosphorylated proteins, thereby antagonizing interactions of integrins with the extracellular matrix and integrin-triggered signaling pathways. Other studies demonstrate important roles for PTEN in dephosphorylating a key signal transduction lipid. In the absence of PTEN, this lipid signal transduction pathway can protect tumor cells from apoptosis. Thus, PTEN appears to be a unique tumor suppressor-with both lipid phosphatase and protein tyrosine phosphatase activities-that negatively regulates cell interactions with the extracellular matrix and that maintains cell sensitivity to apoptosis, e.g., after loss of cell contact with the extracellular matrix. The complex signal transduction pathways regulated by PTEN are described in this review. PTEN and the signaling pathways it regulates may provide novel targets for potential therapy.

Loss of heterozygosity on 8p in prostate cancer implicates a role for dematin in tumor progression

Dematin is a cytoskeletal protein that bundles actin filaments in a phosphorylation-dependent manner. The primary structure of dematin is organized into an N-terminal core domain of unknown function and a C-terminal domain that is homologous to the "headpiece" domain of villin. We have previously localized the dematin gene on human chromosome 8p21.1, a region distal to the ankyrin locus for hereditary spherocytosis. Radiation hybrid mapping now places dematin between D8S258 and D8S137, two microsatellite markers frequently deleted in prostate cancer. The 8p21.1 region is also deleted in prostate, breast, colon, and bladder cancers, suggesting the presence of a tumor suppressor gene(s). Using laser-capture microdissection technique and fluorescence in situ hybridization (FISH), we demonstrate loss of heterozygosity (LOH) of the dematin gene in a majority of chromosomal region 8p21-linked prostate tumors. One allele of dematin was also deleted in the established prostate adenocarcinoma cell line PC-3, which displays a classic oncogenic phenotype. Overexpression of wild-type dematin in PC-3 cells resulted in the restoration of a more polarized, epithelial-like phenotype. Conversely, the heterologous expression of dominant negative mutants of dematin perturbed normal cell morphology of NIH 3T3 fibroblasts. These results suggest a biological function of dematin in the regulation of cell shape, with implications in the pathobiology of prostate tumorigenesis.

Histology of familial thyroid tumours linked to a gene mapping to chromosome 19p13.2

This paper describes the pathology of thyroid tumours showing an autosomal mode of inheritance linked to a gene that maps to chromosome 19p13.2. All the affected members from the family (seven males and two females; mean age 23 years) were clinically euthyroid and presented with nodular goitre; tumour recurrence after thyroidectomy was observed in four. In four of the five patients studied, the tumours were multifocal, bilateral well demarcated or encapsulated and composed of follicles, papillae, trabeculae/solid areas (often resembling hyalinizing trabecular adenoma of the thyroid) or an admixture, formed by cells with pale to intense cytoplasmic eosinophilia. A diagnosis of multiple adenomatous goitre was made in the thyroidectomy specimen from two patients, while the other two patients showed, in addition to multiple adenomas, a co-existent oxyphil papillary carcinoma. The fifth patient had an oxyphil cell carcinoma. All tumours were of follicular cell origin as shown by immunocytochemistry. Less than a third of the benign tumours and all three carcinomas showed a variable number of neoplastic cells diffusely immunostained for mitochondria. Histological findings of a 'multiple adenomatous goitre', non-endemic 'multinodular goitre' or multiple neoplasms of follicular cell origin with the morphology of those described here, particularly in young patients, should alert the pathologist and physician to the possibility of an inherited trait, with its implications for family screening. The tumours are usually benign and well demarcated but because of multicentricity and consequently increased risk of recurrence and/or progression to carcinoma, total thyroidectomy should be advocated.

Modulation of cellular apoptotic potential: contributions to oncogenesis

The importance of apoptosis as a natural means to eliminate unwanted or damaged cells has been realized over the past decade. Many components required to exercise programmed cell death have been identified and shown to pre-exist in most, if not all, cells. Such ubiquity requires that apoptosis be tightly controlled and suggests the propensity of cells to trigger the cellular death machinery can be regulated. Recently, several signaling pathways have been demonstrated to impact the apoptotic potential of cells, most notably the phosphatidylinositol 3' kinase (PI3'K) pathway. The 3' phosphorylated lipid products generated by this enzyme promote activation of a protein-serine kinase, PKB/AKT, which is necessary and sufficient to confer cell PI3'K-dependent survival signals. The relevance of this pathway to human cancer was revealed by the recent finding that the product of the PTEN tumor suppressor gene acts to antagonize PI3'K. This review focuses on the regulation and mechanisms by which PKB activation protects cells and the oncologic consequences of dysregulation of the pathway.

Cell cycle arrest and astrocytic differentiation resulting from PTEN expression in glioma cells

OBJECT

Genetic alterations of the PTEN gene (also known as MMAC1 or TEP1) have frequently been identified in high-grade gliomas, indicating that inactivation of PTEN plays a crucial role in human glioma progression. The aim of this study was to assess the biological significance of PTEN inactivation in the development of glioma.

METHODS

The authors introduced wild-type PTEN complementary DNA into four human glioma cell lines (T98G, U-251MG, U-87MG, and A172) containing endogenous aberrant PTEN alleles. The number of colonies transfected with the wild-type PTEN was reduced to 15 to 32% of those found after transfection of a control vector, suggesting growth suppression by the exogenous PTEN. To analyze phenotypic alterations produced by PTEN expression, T98G-derived clones with inducible PTEN expression were further established using a tetracycline-regulated inducible gene expression system. Induction of PTEN expression suppressed the in vitro growth of T98G cells with accumulation of G1 phase cells. Furthermore, when cells were cultured in the presence of the extracellular matrix (ECM), PTEN expression caused distinct morphological changes, with multiple and elongated cytoplasmic processes similar to those of normal astrocytes. The level of glial fibrillary acidic protein, an intermediate protein specifically expressed in differentiated astrocytes, was upregulated concomitantly.

CONCLUSIONS

These findings strongly indicate that exogenous PTEN expression inhibits the proliferation of glioma cells by inducing G1 arrest and elicits astrocytic differentiation in the presence of the ECM. Inactivation of PTEN would play an important role in the enhancement of unregulated growth of undifferentiated glioma cells.

Alternative splicing of the Drosophila PTEN gene

Mutations in the human PTEN gene have been identified in a number of different tumour types, and in the hamartomatous polyposis syndromes Cowden disease and Bannayan-Zonana syndrome. The PTEN gene encodes a phosphatase that antagonises phosphoinositide 3-kinase (PI3K) signalling by removing the 3' phosphate from phosphatidylinositol 3, 4,5-trisphosphate (PtdIns (3,4,5)P(3)). Here we show that the PTEN gene is conserved in the invertebrate Drosophila melanogaster and demonstrate that the gene undergoes alternative splicing.

Genetic testing for breast cancer predisposition

The recent identification of the BRCA1 and BRCA2 genes has improved our understanding of the association between breast and ovarian cancers in certain families. Carriers of predisposing germline mutations must decide on different options for management, including close follow-up or prophylactic surgery. Further studies are needed to elucidate the optimal management of these patients and to identify the factors that modify their risk for developing breast cancer. Finally, we must work to prevent any form of discrimination against those who, following genetic testing, are found to be at increased risk for breast cancer.

Allelic loss of the PTEN region (10q23) in breast carcinomas of poor pathophenotype

Loss of heterozygosity (LOH) in loci of the 10q23 region that harbor the PTEN gene and mutations in the sequence of this gene have been found in several primary human tumors including breast carcinomas, suggesting that this gene could be implicated in their pathogenesis. We investigated allelic losses in microsatellites of the 10q23 region, and their correlations with nine pathologic parameters in 105 breast carcinomas. The LOH analysis was performed by amplifying DNA by PCR, using five markers of the 10q23 region (D10S1687, D10S541, D10S2491, D10S583 and D10S571). LOH in at least one marker of the PTEN region was found in 29.5% of tumors. The statistical comparison between carcinomas with and without LOH in terms of the pathologic parameters showed significant differences in age (p = 0.03), lymph node metastases (p = 0.02), and higher histological grade (p = 0.02); a trend toward significance was found for progesterone receptors (p = 0.05). LOH in an individual marker and statistically significant relationships to tumor characteristics were observed at locus D10S541 for lymph node metastases (p = 0.04), at D10S2491 (intragenic to the PTEN gene) for lymph node metastases (p = 0.02), and at D10S583 for progesterone receptors (p = 0.01) and for high grade (p = 0.03). These results suggest the PTEN gene, or other genes of the 10q23 region, could be functionally related to breast cancer, probably influencing the development of histological features associated with poor prognosis.

Immunohistochemical evidence of loss of PTEN expression in primary ductal adenocarcinomas of the breast

Germline mutations in PTEN, encoding a dual-specificity phosphatase on 10q23.3, cause Cowden syndrome (CS), which is characterized by a high risk of breast and thyroid cancers. Loss of heterozygosity of 10q22-24 markers and somatic PTEN mutations have been found to a greater or lesser extent in a variety of sporadic component and noncomponent cancers of CS. Among several series of sporadic breast carcinomas, the frequency of loss of flanking markers around PTEN is approximately 30 to 40%, and the somatic intragenic PTEN mutation frequency is <5%. In this study, we analyzed PTEN expression in 33 sporadic primary breast carcinoma samples using immunohistochemistry and correlated this to structural studies at the molecular level. Normal mammary tissue had a distinctive pattern of expression: myoepithelial cells uniformly showed strong PTEN expression. The PTEN protein level in mammary epithelial cells was variable. Ductal hyperplasia with and without atypia exhibited higher PTEN protein levels than normal mammary epithelial cells. Among the 33 carcinoma samples, 5 (15%) were immunohistochemically PTEN-negative; 6 (18%) had reduced staining, and the rest were PTEN-positive. In the PTEN-positive tumors as well as in normal epithelium, the protein was localized in the cytoplasm and in the nucleus (or nuclear membrane). Among the immunostain negative group, all had hemizygous PTEN deletion but no structural alteration of the remaining allele. Thus, in these cases, an epigenetic phenomenon such as hypermethylation, -ecreased protein synthesis or increased protein degradation may be involved. In the cases with reduced staining, 5 of 6 had hemizygous PTEN deletion and 1 did not have any structural abnormality. Finally, clinicopathological features were analyzed against PTEN protein expression. Three of the 5 PTEN immunostain-negative carcinomas were also both estrogen and progesterone receptor-negative, whereas only 5 of 22 of the PTEN-positive group were double receptor-negative. The significance of this last observation requires further study.

A highly accurate, low cost test for BRCA1 mutations

The hereditary breast and ovarian cancer syndrome is associated with a high frequency of BRCA1 mutations. However, the widespread use of BRCA1 testing has been limited to date by three principal concerns: the fear of loss of health and life insurance, the uncertain clinical value of a positive test result, and the current lack of an inexpensive and sensitive screening test for BRCA1 mutations. We have developed an inexpensive system for gene mutational scanning, based on a combination of extensive multiplex PCR amplification and two dimensional electrophoresis. The efficiency of this system, as a screening test for BRCA1 mutations, was evaluated in a panel of 60 samples from high risk women, 14 of which contained a previously identified mutation in BRCA1. All 14 mutations were identified, as well as an additional five that had previously escaped detection. In addition to the 19 mutations, a total of 15 different polymorphic variants were scored, most of which were recurring. All were confirmed by nucleotide sequencing. The cost of screening per sample was calculated to be approximately US$70 for the manual technique used in this study, and may be reduced to approximately US$10 with the introduction of commercially available PCR robotics and fluorescent imaging. Implementation of this method of mutation screening in the research and clinical setting should permit rapid accrual of quantitative data on genotype-phenotype associations for the evaluation of diagnostic testing.

Impaired Fas response and autoimmunity in Pten+/- mice

Inactivating mutations in the PTEN tumor suppressor gene, encoding a phosphatase, occur in three related human autosomal dominant disorders characterized by tumor susceptibility. Here it is shown that Pten heterozygous (Pten+/-) mutants develop a lethal polyclonal autoimmune disorder with features reminiscent of those observed in Fas-deficient mutants. Fas-mediated apoptosis was impaired in Pten+/- mice, and T lymphocytes from these mice show reduced activation-induced cell death and increased proliferation upon activation. Phosphatidylinositol (PI) 3-kinase inhibitors restored Fas responsiveness in Pten+/- cells. These results indicate that Pten is an essential mediator of the Fas response and a repressor of autoimmunity and thus implicate the PI 3-kinase/Akt pathway in Fas-mediated apoptosis.

Somatic mutation of the PTEN/MMAC1 gene in breast cancers with microsatellite instability

The extent to which microsatellite instability (MI) contributes to the etiology of breast cancer has not been established in any large-scale studies. We examined 528 samples of tumor DNA from patients with primary breast cancer for MI, using 14 polymorphic CA-repeat markers. The frequency of MI in these tumors was unexpectedly low (10/528, 1.9%). The ten MI+ tumors were analyzed for mutations in five potential target genes that contain simple repeat sequences (TGFBIIR, IGF2R, hMSH6, BAX and PTEN/MMAC1). A somatic insertion of an extra adenine in the (A)6 region at codon 321-323 (exon 8) of the PTEN/MMAC1 gene, leading to a frame-shift, was identified in one tumor. This observation represented the first documented instance of PTEN/MMAC1 alteration in a MI+ primary breast cancer.

Rare-type mutations of MMAC1 tumor suppressor gene in human glioma cell lines and their tumors of origin

A total of 10 glioma cell lines were examined to evaluate the status of the MMAC1 gene, a candidate tumor suppressor gene. Six cell lines showed mutations with presumed loss of heterozygosity and 1 cell line showed no mRNA expression. The 6 mutations consisted of 3 3-bp deletions (codons 17, 101 or 199), 1 missense mutation (codon 252) and 2 truncation mutations (1 nonsense mutation at codon 233 and 12-bp insertion at codon 241). Among them, the 3-bp deletions, which are a rare type of mutation in MMAC1 gene, were located in the N-terminal half (codons 1-212) of the coding region, which is considered important in MMAC1 function. The missense mutation was located unusually in the C-terminal half (codons 212-403), but it was in a small region in which some other reported missense mutations are clustered. Thus, these 4 mutations were suggested to have functional effects on the MMAC1 activity, like the other 2 mutations with predicted protein truncations. By sequence analysis of cDNA clones, we confirmed that all the mutations including these 4 rare ones were in the MMAC1 gene, not in the PTH2 pseudogene. In 2 cases, we also examined the primary glioma tissues from which the cell lines had been derived and found the same mutations as in the cell lines in both cases. This suggested that the mutations in these cell lines were derived from the primary glioma tissues, but not from artifacts arising during long-term in vitro cultivation.

The tumor-suppressor activity of PTEN is regulated by its carboxyl-terminal region

PTEN is a recently identified tumor suppressor inactivated in a variety of cancers such as glioblastoma and endometrial and prostate carcinoma. It contains an amino-terminal phosphatase domain and acts as a phosphatidylinositol 3,4,5-trisphosphate phosphatase antagonizing the activity of the phosphatidylinositol 3-OH kinase. PTEN also contains a carboxyl-terminal domain, and we addressed the role of this region that, analogous to the amino-terminal phosphatase domain, is the target of many mutations identified in tumors. Expression of carboxyl-terminal mutants in PTEN-deficient glioblastoma cells permitted the anchorage-independent growth of the cells that otherwise was suppressed by wild-type PTEN. The stability of these mutants in cells was reduced because of rapid degradation. Although the carboxyl-terminal region contains regulatory PEST sequences and a PDZ-binding motif, these specific elements were dispensable for the tumor-suppressor function. The study of carboxyl-terminal point mutations affecting the stability of PTEN revealed that these were located in strongly predicted beta-strands. Surprisingly, the phosphatase activity of these mutants was affected in correlation with the degree of disruption of these structural elements. We conclude that the carboxyl-terminal region is essential for regulating PTEN stability and enzymatic activity and that mutations in this region are responsible for the reversion of the tumor-suppressor phenotype. We also propose that the molecular conformational changes induced by these mutations constitute the mechanism for PTEN inactivation.

Genetic counseling for BRCA1/BRCA2 testing

Genetic counseling plays a key role in the BRCA1/BRCA2 testing process. The initial genetic counseling encounter will determine the appropriateness of the test by collecting a detailed family history and determining the likelihood that the family has a BRCA1 or BRCA2 mutation. Once the test is offered, then genetic counseling discussions center around the possible test results, implications of the results to the patient and other relatives, and risks and benefits of testing. The goal of this pre-test genetic counseling session is to ensure that patients have sufficient information with which to make a decision about being tested. At results disclosure, individuals can learn their results along with information about cancer risks and medical management options. Follow-up genetic counseling services can provide continued support and help arrange consultations with other medical care providers as needed. All clinical BRCA1/BRCA2 testing programs should include pre- and post-test genetic counseling.

Mutation testing of early-onset breast cancer genes BRCA1 and BRCA2

BRCA1 and BRCA2, genes predisposing to early-onset breast cancer, have been isolated and are characterized for mutation spectrum, risks of cancer, and function. The different methodologies to screen for mutations in BRCA1 and BRCA2 are briefly discussed including DNA-based methodologies and potential new assays. The numbers and types of mutations identified to date are described, including the problems of ascribing risk to missense mutations. Recurring, possibly founding mutations have been identified in several populations including Ashkenazi Jews, Icelanders, Swedes, and African Americans. From population-based studies, estimates are that 6%-10% of breast cancers are due to mutations in BRCA1 and BRCA2. Knowledge of mutation status raises additional questions including the interpretation of negative tests and the risks of breast and other cancers associated with positive test results.

Accurate, high-throughput "snapshot" detection of hMLH1 mutations by two-dimensional DNA electrophoresis

The human genome and related projects have resulted in the isolation of a rapidly growing number of genes that cause susceptibility to human cancer. With rare exception, these genes are large and have disease-associated mutations scattered along the length of the genes. Therefore, the development of accurate and cost-efficient mutation detection tests that can scan entire genes singly or in combination is warranted. hMLH1, encoding a mismatch repair enzyme, is a susceptibility gene for hereditary nonpolyposis colon cancer syndrome. This gene comprises 19 exons; mutations are scattered, typical of many susceptibility genes. Here, we present a strategy that combines extensive PCR multiplexing and two-dimensional DNA electrophoresis (Two-Dimensional Gene Scanning, TDGS) to scan accurately for mutations that lie within the exons and splice junctions of hMLH1. All target fragments, designed to have optimal melting characteristics, were prepared in a two-stage PCR--a four-plex long-distance PCR followed by short PCR in two multiplex groups of 10 and 11 amplicons. The mixture of amplicons was subjected to two-dimensional electrophoresis: separation by size in the first dimension and by melting characteristics in the second. Using this design, 41 samples containing known hMLH1 sequence variants or no alterations were blindly subjected to TDGS. All mutations were detected; there were no genuine false-positive or false-negative results. These results confirm that TDGS is a generally applicable, rapid, accurate, and reproducible mutation detection technology that would serve large-scale molecular epidemiologic studies as well as clinical molecular diagnostic purposes.

Growth suppression by Lkb1 is mediated by a G(1) cell cycle arrest

Germ-line mutations of LKB1 (STK11) lead to Peutz-Jeghers syndrome characterized by gastrointestinal polyps and cancer of different organ systems. The mutations lead to loss or severe impairment of Lkb1 serine/threonine kinase activity. Therefore LKB1 has been implicated as a tumor suppressor gene, but only a few mutations in the coding exons of LKB1 have been detected in sporadic tumors. Here, we have identified tumor cell lines with severely reduced mRNA levels and impaired Lkb1 kinase activity. Reintroducing Lkb1 into these cells suppressed cell growth. The Lkb1-mediated growth inhibition was caused by a G(1) cell cycle block and was not detected with several naturally occurring Lkb1 mutants. These results indicate that LKB1 has functional and specific growth-suppressing activity.

PTEN mutation spectrum and genotype-phenotype correlations in Bannayan-Riley-Ruvalcaba syndrome suggest a single entity with Cowden syndrome

Germline mutations in the tumour suppressor gene PTEN have been implicated in two hamartoma syndromes that exhibit some clinical overlap, Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRR). PTEN maps to 10q23 and encodes a dual specificity phosphatase, a substrate of which is phosphatidylinositol 3,4,5-triphosphate, a phospholipid in the phosphatidylinositol 3-kinase pathway. CS is characterized by multiple hamartomas and an increased risk of benign and malignant disease of the breast, thyroid and central nervous system, whilst the presence of cancer has not been formally documented in BRR. The partial clinical overlap in these two syndromes is exemplified by the hallmark features of BRR: macrocephaly and multiple lipomas, the latter of which occur in a minority of individuals with CS. Additional features observed in BRR, which may also occur in a minority of CS patients, include Hashimoto's thyroiditis, vascular malformations and mental retardation. Pigmented macules of the glans penis, delayed motor development and neonatal or infant onset are noted only in BRR. In this study, constitutive DNA samples from 43 BRR individuals comprising 16 sporadic and 27 familial cases, 11 of which were families with both CS and BRR, were screened for PTEN mutations. Mutations were identified in 26 of 43 (60%) BRR cases. Genotype-phenotype analyses within the BRR group suggested a number of correlations, including the association of PTEN mutation and cancer or breast fibroadenoma in any given CS, BRR or BRR/CS overlap family ( P = 0.014), and, in particular, truncating mutations were associated with the presence of cancer and breast fibroadenoma in a given family ( P = 0.024). Additionally, the presence of lipomas was correlated with the presence of PTEN mutation in BRR patients ( P = 0.028). In contrast to a prior report, no significant difference in mutation status was found in familial versus sporadic cases of BRR ( P = 0.113). Comparisons between BRR and a previously studied group of 37 CS families suggested an increased likelihood of identifying a germline PTEN mutation in families with either CS alone or both CS and BRR when compared with BRR alone ( P = 0.002). Among CS, BRR and BRR/CS overlap families that are PTEN mutation positive, the mutation spectra appear similar. Thus, PTEN mutation-positive CS and BRR may be different presentations of a single syndrome and, hence, both should receive equal attention with respect to cancer surveillance.

PTEN/MMAC1/TEP1 in signal transduction and tumorigenesis

The level of phosphorylation within cells is tightly regulated by the concerted action of protein kinases and protein phosphatases [Hunter, T. (1995) Cell 80, 225-236]. Disregulation in the activity of either of these players can lead to cellular transformation. Many protein tyrosine kinases are proto-oncogenes and it has been postulated that some protein phosphatases may act as tumor suppressors. Herein we will review the recent findings addressing the roles the candidate tumor suppressor PTEN/MMAC1/TEP1 (PTEN, phosphatase and tensin homologue deleted from chromosome 10; MMAC 1, mutated in multiple advanced cancers 1; TEP1, TGF beta regulated and epithelial cell enriched phosphatase 1) plays in signal transduction and tumorigenesis. PTEN is a dual specificity protein phosphatase (towards phospho-Ser/Thr and phospho-Tyr) and, unexpectedly, also has a phosphoinositide 3-phosphatase activity. PTEN plays an important role in the modulation of the 1-phosphatidylinositol 3-kinase (PtdIns 3-kinase) pathway, by catalyzing the degradation of the PtdIns(3,4,5)P3 generated by PtdIns 3-kinase; this inhibits the downstream functions mediated by the PtdIns 3-kinase pathway, such as activation of protein kinase B (PKB, also known as Akt), cell survival and cell proliferation. Furthermore, PTEN modulates cell migration and invasion by negatively regulating the signals generated at the focal adhesions, through the direct dephosphorylation and inhibition of focal adhesion kinase (FAK). Growth factor receptor signaling is also negatively regulated by PTEN, through the inhibition of the adaptor protein Shc. While some of the functions of PTEN have been elucidated, it is clear that there is much more to discover about the roles of this unique protein.

Alteration of the PTEN/MMAC1 gene locus in primary lung cancer with distant metastasis

The PTEN/MMAC1 gene located at 10q23, has been proposed to be a tumor suppressor gene. To determine the involvement of alteration of the PTEN/MMAC1 gene in carcinogenesis and the progression of primary lung cancers, we analyzed tumor samples of primary and distant metastatic sites and normal lung tissue samples of 30 patients with advanced lung cancer with distant metastasis. The tissues were analyzed for allelic deletion and mutational inactivation of PTEN/MMAC1 by loss of heterozygosity (LOH) analysis, polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), and direct sequence analysis. LOH of the PTEN/MMAC1 locus was common in each histologic type of primary lung cancer. In this study, the overall allelic deletion rate was 33.3% (7/21). Allelic loss at the primary site and that at the metastatic site of each patient, were identical; in most cases, it seemed that the allelic loss had occurred before metastasis. Sequence analysis of the PTEN/MMAC1 gene revealed a G to C substitution located 8 bp upstream of the coding region of exon 1 and which seems to be a polymorphism, in 4 of the 30 cases. Somatic mutations of the PTEN/MMAC1 gene were not identified in any of the tumors at the primary and metastatic sites. These data indicate that point mutations in the PTEN/MMAC1 gene are probably not an important factor in tumorigenesis and the progression of a major subset of lung cancers. Due to frequent allelic loss at the PTEN/MMAC1 locus occurring at a stage earlier than the metastatic process, alternative mechanisms in which the remaining allele is inactivated such as methylation or homozygous deletion of a small region of the gene that can not be detected by the usual analysis, or alteration of other important tumor suppressor genes lying close to the PTEN/MMAC1 gene on 10q23, may be involved in the tumorigenesis of lung cancers of all histologic subtypes.

PTEN transcriptionally modulates c-myc gene expression in human breast carcinoma cells and is involved in cell growth regulation

A novel tumor suppressor gene, PTEN, has recently been identified at chromosome 10q23, which is inactivated in a number of different tumor types including breast cancer. An investigation of the functional role suggested that PTEN transcriptionally represses both exogenous and endogenous c-myc expressions in human breast carcinoma cells. PTEN, when ectopically expressed in human breast carcinoma cells, exhibited an inhibition of phosphorylation of both activating residues of protein kinase B (PKB)/AKT at Ser-473 and Thr-308 without any significant alteration of AKT expression. Furthermore, introduction of PTEN into human breast carcinoma cells induced apoptotic cell death and inhibited cell growth and tumor formation in nude mice. Taken together, our data suggest that PTEN acts as a transcriptional repressor, inhibits the AKT-mediated cell survival signaling pathway, and negatively regulates human breast carcinoma cell growth. These results further emphasize the potential of PTEN as a gene therapeutic agent.

PTEN interactions with focal adhesion kinase and suppression of the extracellular matrix-dependent phosphatidylinositol 3-kinase/Akt cell survival pathway

The tumor suppressor PTEN is a phosphatase with sequence homology to tensin. PTEN dephosphorylates phosphatidylinositol 3,4, 5-trisphosphate (PIP3) and focal adhesion kinase (FAK), and it can inhibit cell growth, invasion, migration, and focal adhesions. We investigated molecular interactions of PTEN and FAK in glioblastoma and breast cancer cells lacking PTEN. The PTEN trapping mutant D92A bound wild-type FAK, requiring FAK autophosphorylation site Tyr397. In PTEN-mutated cancer cells, FAK phosphorylation was retained even in suspension after detachment from extracellular matrix, accompanied by enhanced PI 3-K association with FAK and sustained PI 3-K activity, PIP3 levels, and Akt phosphorylation; expression of exogenous PTEN suppressed all five properties. PTEN-mutated cells were resistant to apoptosis in suspension, but most of the cells entered apoptosis after expression of exogenous PTEN or wortmannin treatment. Moreover, overexpression of FAK in PTEN-transfected cells reversed the decreased FAK phosphorylation and PI 3-K activity, and it partially rescued PIP3 levels, Akt phosphorylation, and PTEN-induced apoptosis. Our results show that FAK Tyr397 is important in PTEN interactions with FAK, that PTEN regulates FAK phosphorylation and molecular associations after detachment from matrix, and that PTEN negatively regulates the extracellular matrix-dependent PI 3-K/Akt cell survival pathway in a process that can include FAK.

No evidence for germline PTEN mutations in families with breast and brain tumours

Germline mutations of the PTEN gene are involved in Cowden disease, a genetic condition associated with an increased risk of breast cancer. Further somatic PTEN mutations have been found in glioblastomas and to a lesser extent in meningiomas. Therefore, PTEN germline mutations were searched for in a series of 20 unrelated women with breast cancer who also had a personal or familial breast-brain tumour history. Inclusion criteria were 1. family history of breast cancer; 2. absence of germline BRCA1 and p53 mutation; and 3. at least one case of brain tumour (glioblastoma, meningioma, or medulloblastoma) in either the index case or one of their first or second degree relatives. Any stigmata of Cowden disease was an exclusion criteria. Screening of the PTEN gene for point mutations or small rearrangements were performed using the denaturing gradient gel electrophoresis method on the 9 coding exons. No disease-associated mutation of the PTEN gene has been detected in our series. It is, thus, unlikely that PTEN is a significant BRCA predisposing locus. However, one might ask whether breast cancer cases resulting from germline PTEN mutation could occur without any mammary histological feature of Cowden disease.

Loss-of-function mutations in PPAR gamma associated with human colon cancer

The gamma isoform of the peroxisome proliferator-activated receptor, PPAR gamma, regulates adipocyte differentiation and has recently been shown to be expressed in neoplasia of the colon and other tissues. We have found four somatic PPAR gamma mutations among 55 sporadic colon cancers: one nonsense, one frameshift, and two missense mutations. Each greatly impaired the function of the protein. c.472delA results in deletion of the entire ligand binding domain. Q286P and K319X retain a total or partial ligand binding domain but lose the ability to activate transcription through a failure to bind to ligands. R288H showed a normal response to synthetic ligands but greatly decreased transcription and binding when exposed to natural ligands. These data indicate that colon cancer in humans is associated with loss-of-function mutations in PPAR gamma.

PTEN/MMAC1 mutations in hepatocellular carcinomas

Mutations in the PTEN/MMAC1 gene have been identified in several types of human cancers and cancer cell lines, including brain, endometrial, prostate, breast, thyroid, and melanoma. In this study, we screened a total of 96 hepatocellular carcinoma (HCC) samples from Taiwan, where HCC is the leading cancer in males and third leading cancer in females, for mutations in the PTEN/MMAC1 gene. Complete sequence analysis of these samples demonstrated a missense mutation in exon 5 (K144I) and exon 7 (V255A) from HCC samples B6-21 and B6-2, respectively. A putative splice site mutation was also detected in intron 3 from sample B6-2. Both B6-21 and B6-2 were previously shown to contain missense mutations in the coding sequences of the p53 gene. Functional studies with the two missense mutations demonstrated that while mutation V255A in exon 7 resulted in a loss of phosphatase activity, mutation K144I in exon 5 retained its phosphatase activity. Additionally, we identified a silent mutation (P96P) in exon 5 of the PTEN/MMAC1 gene from HCC sample B6-22. These data provide the first evidence that the PTEN/MMAC1 gene is mutated in a subset of HCC samples.

MYC oncogenes and human neoplastic disease

c-myc, N-myc and L-myc are the three members of the myc oncoprotein family whose role in the pathogenesis of many human neoplastic diseases has received wide empirical support. In this review, we first summarize data, derived mainly from non-clinical studies, indicating that these oncoproteins actually serve quite different roles in vivo. This concept necessarily lies at the heart of the basis for the observation that the deregulated expression of each MYC gene is reproducibly associated with only certain naturally occurring malignancies in humans and that these genes are not interchangeable with respect to their aberrant functional consequences. We also review evidence implicating each of the above MYC genes in specific neoplastic diseases and have attempted to identify unresolved questions which deserve further basic or clinical investigation. We have made every attempt to review those diseases for which significant and confirmatory evidence, based on studies with primary tumor material, exists to implicate MYC members in their causation and/or progression.

Mutation analysis of the putative tumor suppression gene PTEN/MMAC1 in sporadic breast cancer

PTEN/MMAC1, a potential human tumor suppressor gene, has been found to have inactivating mutations in several types of cancer, including breast cancer. The incidence of breast cancer in Chinese is quite low in comparison with Caucasians, and genetic factors may play some roles. To further determine the role of PTEN/MMAC1 in breast cancer in Chinese, we used loss of heterozygosity (LOH), single strand conformation polymorphism (SSCP) with direct sequencing of variant bands, and Southern blot analysis methods to analyze mutations in PTEN/MMAC1 in 52 cases of breast cancer. None had LOH at chromosome 10q23.3. One mutation was identified, a somatic 3-base deletion, in one case. Our results suggest PTEN/MMAC1 does not play a major role in the development of sporadic breast cancer.

Familial non-medullary thyroid carcinoma: pathology review in 27 affected cases from 13 French families

BACKGROUND AND OBJECTIVES

When familial non-medullary thyroid cancer (FNMTC) develops with no obvious associated pathogenetic factor, an inherited predisposition may underlie the process. The present study was conducted because detailed pathological findings are lacking in most series of FNMTC.

PATIENTS AND METHODS

Thirteen families comprising 27 cases of FNMTC were included (1.8% of differentiated thyroid carcinoma). The family relationship (20 F, 7 M; age 46 +/- 16 years; mean +/- SD) was 'siblings' in eight families, 'parent and child' in four and 'aunt and niece' in one. Careful pathological review of the thyroid tumours (papillary/follicular: 25/2, size: 16 +/- 11 mm) was performed.

RESULTS

Initial staging according to extension was as follows: grade I (n = 16), II (n = 2), III (n = 6), IV (n = 3). Fourteen tumours were papillary microcarcinomas (size: 8 +/- 2 mm). No tumour phenotype that may be considered specific for FNMTC was found when considering either age, pathological findings or tumour aggressiveness. Although rare events were found in both relatives of some families suggesting a putative 'familial' phenotype of FNMTC, this may be fortuitous.

CONCLUSION

Micro familial non-medullary thyroid cancers are more common than previously reported and further studies are required to be able to distinguish this subgroup from sporadic papillary microcarcinomas. The careful pathological review of the familial non-medullary thyroid cancer in this study does not seem to point to a distinct subgroup of familial differentiated thyroid carcinoma although the data are intriguing. Genetic studies are now required to investigate this issue.

Somatic mutation of PTEN in bladder carcinoma

The tumour suppressor gene PTEN/MMAC1, which is mutated or homozygously deleted in glioma, breast and prostate cancer, is mapped to a region of 10q which shows loss of heterozygosity (LOH) in bladder cancer. We screened 123 bladder tumours for LOH in the region of PTEN. In 53 informative muscle invasive tumours (> or = pT2), allele loss was detected in 13 (24.5%) and allelic imbalance in four tumours (overall frequency 32%). LOH was found in four of 60 (6.6%) informative, non-invasive tumours (pTa/pT1). We screened 63 muscle invasive tumours for PTEN mutations by single-strand conformation polymorphism (SSCP) analysis and for homozygous deletion by duplex quantitative polymerase chain reaction (PCR). Two homozygous deletions were identified but no mutations. Of 15 bladder tumour cell lines analysed, three showed homozygous deletion of all or part of the PTEN gene, but none had mutations detectable by SSCP analysis. Our results indicate that PTEN is involved in the development of some bladder tumours. The low frequency of mutation of the retained allele in tumours with 10q23 LOH suggests that there may be another predominant mechanism of inactivation of the second allele, for example small intragenic deletions, that hemizygosity may be sufficient for phenotypic effect, or that there is another target gene at 10q23.

Mutation and deletion analysis of GFR alpha-1, encoding the co-receptor for the GDNF/RET complex, in human brain tumours

Glial cell line-derived neurotrophic factor (GDNF) plays a key role in the control of vertebrate neuron survival and differentiation in both the central and peripheral nervous systems. GDNF preferentially binds to GFRalpha-1 which then interacts with the receptor tyrosine kinase RET. We investigated a panel of 36 independent cases of mainly advanced sporadic brain tumours for the presence of mutations in GDNF and GFRalpha-1. No mutations were found in the coding region of GDNF. We identified six previously described GFRalpha-1 polymorphisms, two of which lead to an amino acid change. In 15 of 36 brain tumours, all polymorphic variants appeared to be homozygous. Of these 15 tumours, one also had a rare, apparently homozygous, sequence variant at codon 361. Because of the rarity of the combination of homozygous sequence variants, analysis for hemizygous deletion was pursued in the 15 samples and loss of heterozygosity was found in 11 tumours. Our data suggest that intragenic point mutations of GDNF or GFRalpha-1 are not a common aetiologic event in brain tumours. However, either deletion of GFRalpha-1 and/or nearby genes may contribute to the pathogenesis of these tumours.

Expression of LKB1 and PTEN tumor suppressor genes during mouse embryonic development

Germ-line mutations of LKB1 and PTEN tumor suppressor genes underlie the phenotypically related Peutz-Jeghers syndrome (PJS) and Cowden disease (CD), respectively. To analyze possible developmental roles of PTEN and LKB1, we have studied their mRNA expression during mouse embryonic development (E7-17.5) by in situ hybridization. Ubiquitous expression of both genes during early stages (E7-11) became more restricted in later embryonic development (E15-19) where LKB1 and PTEN showed prominent overlapping expression in e.g. gastrointestinal tract and lung. In contrast, LKB1 was selectively expressed at high levels in testis and PTEN was prominently expressed in skin epithelium and underlying mesenchyme. These results indicate that LKB1 and PTEN display largely overlapping expression patterns during embryonic development. Moreover, a high expression of these genes was observed in the tissues and organs affected in PJS and CD patients and in PTEN+/- mice.

Tinnitus as the presenting symptom in a case of Lhermitte-Duclos disease

Dysplastic gangliocytoma or Lhermitte-Duclos disease (LDD) is a hamartomatous malformation of the cerebellar hemisphere that usually presents with signs of increased intracranial pressure or symptoms of cerebellar dysfunction. In this paper, we report a case of LDD presenting with tinnitus, and postulate a probable mechanism for this unusual presentation.

Mutational analysis of the PTEN gene in gliomas: molecular and pathological correlations

The PTEN gene, recently identified on chromosome 10q23, has been proposed to be a candidate tumor suppressor gene inactivated in multiple cancers including glial tumors. We investigated 47 glioblastomas (GBM), 14 anaplastic astrocytomas (AA), 6 non-pilocytic low-grade astrocytomas (LGA), 21 low-grade and anaplastic oligodendrogliomas (O) and oligoastrocytomas (OA), and 3 ependymomas (E) for mutation of the PTEN gene using denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing. These tumors have been previously screened for loss of heterozygosity (LOH) on chromosome 10q, p53 mutations and EGFR amplification. Overall, PTEN mutations, detected in 14 of 91 tumors, were present in 13 of 47 GBM and 1 of 14 AA. In contrast, mutations were absent in other glioma subtypes (0/30). In all informative cases, PTEN mutations occurred in tumors showing LOH on chromosome 10q, confirming the inactivation of this gene by a 2-hit mechanism. No correlation was observed between the presence of PTEN mutation and p53 mutation and EGFR amplification. Our results indicate that biallelic PTEN inactivation plays an important role in the pathogenesis of high-grade astrocytomas as a late event. Moreover, they suggest that PTEN alterations are equally involved in the 2 glioblastoma pathways defined by the presence of EGFR amplification and p53 mutation. Finally, correlation analysis with clinical data did not show that PTEN mutation was linked to survival of the patients.

New insights into tumor suppression: PTEN suppresses tumor formation by restraining the phosphoinositide 3-kinase/AKT pathway

The most recently discovered PTEN tumor suppressor gene has been found to be defective in a large number of human cancers. In addition, germ-line mutations in PTEN result in the dominantly inherited disease Cowden syndrome, which is characterized by multiple hamartomas and a high proclivity for developing cancer. A series of publications over the past year now suggest a mechanism by which PTEN loss of function results in tumors. PTEN appears to negatively control the phosphoinositide 3-kinase signaling pathway for regulation of cell growth and survival by dephosphorylating the 3 position of phosphoinositides.

Inactivation of the PTEN tumor suppressor gene is associated with increased angiogenesis in clinically localized prostate carcinoma

The PTEN tumor suppressor gene encodes a dual-specificity protein phosphatase that may play a key role in modulating integrin-mediated signals. Inactivation of the PTEN gene has been detected in a small percentage of clinically localized prostate cancers but is common in metastatic disease. It has been shown in glioblastoma cell lines that loss of chromosome 10q, where the PTEN gene is located, is associated with increased angiogenic activity in the conditioned medium attributable to downregulation of thrombospondin-1, a negative regulator of angiogenesis. Therefore, we wished to determine whether inactivation of PTEN might be associated with increased angiogenesis in prostate cancers, because increased angiogenesis in localized cancers is associated with development of metastatic disease. Angiogenesis was assessed by counting microvessels in areas of maximal neovascularization after immunostaining with anti-factor VIII-related antigen antibodies in eight cases with proven homozygous deletion of the PTEN gene and 24 control cases. There was a statistically significant correlation between PTEN inactivation and increased microvessel counts. The microvessel density was higher at all Gleason scores in the cases with PTEN inactivation compared with control cases with the same score. To determine whether the increased angiogenesis in cases with PTEN inactivation was caused by downregulation of expression of the angiogenesis inhibitor thrombospondin-1, we analyzed a subset of the cases by immunostaining with anti-thrombospondin-1 antibody. Approximately 25% of cases showed decreased staining of prostate cancer cells, but there was no correlation with PTEN inactivation. Thus, PTEN inactivation is associated with increased angiogenesis, but the increased angiogenesis is not attributable to downregulation of thrombospondin-1 expression.

Mutation analysis of the PTEN/MMAC1 gene in cancers of the digestive tract

The 10q23.3 gene PTEN (phosphatase and Tensin homologue deleted on chromosome 10) or MMAC1 (mutated in multiple advanced cancers 1) was recently reported to undergo frequent mutation, including mutations and deletions in multiple advanced cancers. This study showed that the aberrant transcripts of this gene are frequently found in cancers of the digestive tract, paired non-cancerous tissues and normal peripheral mononuclear cells. Sequence analysis of the aberrant transcripts revealed three types of deletions: (i) a deletion junction with a splicing-like donor or acceptor sequence; (ii) several-base homology near or between the donor acceptor site at the deletion junction; and (iii) deletion with insertion. From these results, it is suggested that aberrant transcripts of PTEN/MMAC1 found by nested reverse transcription-polymerase chain reaction are a common (or natural) phenomenon unrelated to oncogenesis. The mechanism producing these aberrant transcripts needs further investigation. Using single-strand conformation polymorphism and direct sequencing to analyse for small base changes of the genomic DNA of the PTEN/MMAC1 gene revealed no point mutations or small base changes.

Lhermitte-Duclos disease as a component of Cowden's syndrome. Case report and review of the literature

In recent years, 16 cases involving the association between Lhermitte-Duclos disease (LDD), which is a hamartomatous overgrowth of cerebellar tissue, and Cowden's syndrome (CS), an autosomal-dominant condition characterized by multiple hamartomas and neoplasias, have been reported. LDD may be one of the manifestations of CS. Recently, mutations of the PTEN/MMAC 1 gene, a tumor suppressor gene, have been found in families with CS, including four patients in whom LDD was diagnosed. The authors present a case of LDD in a 53-year-old woman who also had the typical mucocutaneous lesions found in CS, as well as goiter and intestinal polyposis. In this case, CS had never been suspected until the diagnosis of LDD was made. The mutation detected in the PTEN/MMAC 1 gene as well as neuropathological results are described.