Mutation analysis of the PTEN / MMAC1 gene in Japanese patients with Cowden disease

Analysis of the loss of phosphatase and tensin homolog expression in thyroid tissue for the diagnosis of Cowden syndrome

BACKGROUND

Cowden syndrome is an autosomal-dominant disorder caused by a germline phosphatase and tensin homolog mutation, giving rise to several tumors with an aggressive clinical course. In the thyroid, there are certain histologic criteria that could be related to this syndrome that could be useful for its early detection. We sought to analyze the loss of phosphatase and tensin homolog in thyroid histologic pieces with certain histologic criteria and to determine the percentage of patients diagnosed with Cowden syndrome with this methodology.

METHODS

Five hundred thirty-five thyroid specimens collected were retrospectively analyzed (2017-2020). Those samples that presented certain histologic criteria were studied for loss of phosphatase and tensin homolog expression. Patients with loss of expression underwent a clinical study to rule out dermatologic or other lesions compatible with Cowden syndrome. Patients with positive clinical study were referred for genetic study.

RESULTS

The phosphatase and tensin homolog study was performed in 6.7% (n = 36) of the thyroidectomy samples, showing loss of expression in 22% (n = 8); the most frequent histologic finding was the presence of multiple monomorphous adenomatous nodules. The samples with loss of expression showed more diffuse oncocytic changes. Of the 8 patients with loss of expression, 5 showed dermatologic lesions that could be associated with Cowden syndrome and 1 had a history of macrocephaly. These patients were referred for genetic study, being positive for Cowden syndromein in one quarter of the cases (n = 2).

CONCLUSION

The immunohistochemical study of phosphatase and tensin homolog in pieces of thyroidectomies with histologic criteria suggestive of Cowden syndrome can help in its early diagnosis.

Defining the membrane-associated state of the PTEN tumor suppressor protein

Phosphatase and tensin-homolog deleted on chromosome 10 (PTEN) is a tumor-suppressor protein that regulates phosphatidylinositol 3-kinase (PI3-K) signaling by binding to the plasma membrane and hydrolyzing the 3' phosphate from phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3) to form phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2). Several loss-of-function mutations in PTEN that impair lipid phosphatase activity and membrane binding are oncogenic, leading to the development of a variety of cancers, but information about the membrane-associated state of PTEN remains sparse. We have modeled a membrane-associated state of the truncated PTEN structure bound to PI(3,4,5)P3 via multiscale molecular dynamics simulations. We show that the location of the membrane-binding surface agrees with experimental observations and is robust to changes in lipid composition. The level of membrane interaction is substantially reduced in the phosphatase domain for the triple mutant R161E/K163E/K164E, in line with experimental results. We observe clustering of anionic lipids around the C2 domain in preference to the phosphatase domain, suggesting that the C2 domain is involved in nonspecific interactions with negatively charged lipid headgroups. Finally, our simulations suggest that the oncogenicity of the R335L mutation may be due to a reduction in the interaction of the mutant PTEN with anionic lipids.

Multiple primary malignancies and subtle mucocutaneous lesions associated with a novel PTEN gene mutation in a patient with Cowden syndrome: case report

Background

Cowden syndrome (CS) is a cancer predisposition syndrome associated with increased risk of breast, thyroid, and endometrial cancers, and is characterized by development of benign mucocutaneous lesions.

Case presentation

Here we report on a 58-year-old woman with multiple primary malignancies and subtle mucocutaneous lesions such as small polyps and wart-like papulas. Over a period of 23 years, she developed various malignant neoplasms including thyroid, ovarian, stomach, and colon carcinomas, and a benign meningioma. Direct sequencing analysis of the PTEN gene revealed a novel germline mutation (c.438delT, p.Leu146X).

Conclusion

This case demonstrates that Cowden syndrome is a multi-system disease that can result in the development of multiple malignant and benign tumors.

A novel mutation of the PTEN gene in a Japanese patient with Cowden syndrome and bilateral breast cancer

Cowden syndrome (CS), also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome associated with a high risk of breast and thyroid cancers. The phosphatase and tensin homolog gene (PTEN) encodes a lipid phosphatase that contains a PTPase domain and a C2 domain and plays a role as a tumor suppressor that negatively regulates the cell-survival signaling pathway initiated by phosphatidylinositol 3-kinase (PI3K). PTEN inhibits angiogenesis, and germline mutations of the PTEN gene are associated with CS. We screened for mutations in the PTEN gene in two unrelated Japanese patients with CS. In one patient, who suffered from bilateral breast cancer, thyroid adenoma, and gastric malignant lymphoma, we found a single-base substitution in exon 2 (115G>C) of the PTEN gene. This transversion results in a germline missense mutation (A39P). To date, nine different mutations have been identified in exon 2 of the PTEN gene in patients with CS and variant CS; however, the A39P missense mutation has not been reported previously. We also detected a previously reported nonsense mutation, 697C>T, resulting in R233X.

A novel mutation of PTEN gene in a patient with Cowden syndrome with excessive papillomatosis of the lips, discrete cutaneous lesions, and gastrointestinal polyposis

Cowden syndrome is an inherited disease characterized by mucocutaneous lesions, gastrointestinal hamartomatous polyposis and an increased risk of breast, thyroid and endometrial carcinomas. Despite well described phenotypic expression of this disease, it is not easy to determine correct clinical diagnosis. In this case report we present a clinical history of a patient with Cowden syndrome. When he was 22 years old, he was found to have polyposis of gastrointestinal tract. The diagnosis of Peutz-Jeghers syndrome was established. Owing to intensive belly spasms, as a 36-year-old he was sent to another gastroenterological department where the thorough gastrointestinal tract examination was performed. We found glycogenic acanthosis of the esophagus; diffuse polyposis with large polyps within the stomach, and polyposis with small polyps in duodenum, colon, and rectum. We also noted the presence of excessive mucocutaneous papillomatosis of the lips and subtle skin lesions. Possible Cowden syndrome diagnosis was suggested. The same year he underwent plastic operation of the lips. During surgery, diffuse nodularity of the trachea was also noted. After plastic operation and assessment of Cowden syndrome as a possible diagnosis, he was recommended for a genetic examination. Diagnosis of Cowden syndrome was confirmed by sequencing analysis of the PTEN gene (phosphatase and tensin homolog deleted on chromosome 10). We found 'c.825_840delAAATACATTCTTCATA' deletion. This case affirmed that, for establishment of a correct diagnosis, especially for rare clinically overlapping syndromes, molecular testing is usually the only reliable method.

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.

Two novel mutations ofPTEN gene in Japanese patients with Cowden syndrome

Cowden syndrome (CS), also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome associated with high risk of breast and thyroid cancer. In three unrelated Japanese CS patients, three PTEN germline mutations were identified, including two novel ones: 589A --> T, resulting in Lys197Stop, and 219-222delAAGA. We also detected a previously reported mutation: 697C --> T, resulting in Arg233Stop. Reports from Western countries have indicated that approximately two-thirds of mutations are found in exons 5, 7, and 8, which is almost the same frequency as found in Japanese CS. No genotype-phenotype correlations have been found in CS patients from 21 Japanese families.

PTEN: one gene, many syndromes

PTEN, on 10q23.3, encodes a major lipid phosphatase which signals down the phosphoinositol-3-kinase/Akt pathway and effects G1 cell cycle arrest and apoptosis. Germline PTEN mutations have been found to occur in 80% of classic Cowden syndrome (CS), 60% of Bannayan-Riley-Ruvalcaba syndrome (BRRS), up to 20% of Proteus syndrome (PS), and approximately 50% of a Proteus-like syndrome (PSL). CS is a heritable multiple hamartoma syndrome with a high risk of breast, thyroid, and endometrial carcinomas. BRRS is a congenital autosomal dominant disorder characterized by megencephaly, developmental delay, lipomatosis, and speckled penis. PS and PSL had never been associated with risk of malignancy. Finding germline PTEN mutations in patients with BRRS, PS, and PSL suggests equivalent risks of developing malignancy as in CS with implications for medical management. The mutational spectra of CS and BRRS overlap, with many of the mutations occurring in exons 5, 7, and 8. Genotype-phenotype association analyses have revealed that the presence of germline PTEN mutations is associated with breast tumor development, and that mutations occurring within and 5' of the phosphatase motif were associated with multi-organ involvement. Pooled analysis of PTEN mutation series of CS and BRRS occurring in the last five years reveals that 65% of CS-associated mutations occur in the first five exons encoding the phosphatase domain and the promoter region, while 60% of BRRS-associated mutations occur in the 3' four exons encoding mainly the C2 domain. Somatic PTEN mutations occur with a wide distribution of frequencies in sporadic primary tumors, with the highest frequencies in endometrial carcinomas and glioblastoma multiform. Several mechanisms of PTEN inactivation occur in primary malignancies derived from different tissues, but a favored mechanism appears to occur in a tissue-specific manner. Inappropriate subcellular compartmentalization and increased/decreased proteosome degradation may be two novel mechanisms of PTEN inactivation. Further functional work could reveal more effective means of molecular-directed therapy and prevention.

Cowden's disease: clinical and molecular genetic findings in a patient with a novel PTEN germline mutation

We report a 54-year-old woman with Cowden's disease (CD) who was found to carry a novel germline mutation in the PTEN gene. The mutation (c.334C-->G) introduced a splice donor site within exon 5 that caused the expression of an aberrant transcript lacking 159 nucleotides corresponding to codons 112-164. Clinically, the patient showed multiple benign hamartomatous lesions of the skin, papillomatosis of the lips and oral mucosa, polyposis coli and bilateral fibrocystic disease of the breast. In addition, she developed different types of malignant neoplasms, including bilateral carcinomas of the breast and malignant melanomas of the skin. Molecular genetic analysis of a benign skin hamartoma and an invasive ductal breast carcinoma revealed loss of heterozygosity (LOH) at microsatellite markers on chromosome 10 in the carcinoma but not in the hamartoma. The breast carcinoma additionally carried a somatic TP53 point mutation (c.466C-->G; R156G) that was associated with LOH on 17p and nuclear p53 protein accumulation. Taken together, our findings indicate that benign hamartomas in CD may develop without loss of the second (wild-type) PTEN allele, whereas the pathogenesis of malignant tumours, such as breast carcinomas, appears to require the complete inactivation of Pten as well as further alterations such as the loss of p53-dependent growth control.