LKB1 exonic and whole gene deletions are a common cause of Peutz-Jeghers syndrome.

BACKGROUND: LKB1/STK11 germline mutations cause Peutz-Jeghers syndrome (PJS). The existence of a second PJS locus is controversial, the evidence in its favour being families unlinked to LKB1 and the low frequency of LKB1 mutations found using conventional methods in several studies. Exonic and whole gene deletion or duplication events cannot be detected by routine mutation screening methods. OBJECTIVE: To seek evidence for LKB1 germline deletions or duplications by screening patients meeting clinical criteria for PJS but without detected mutations on conventional screening. METHODS: From an original cohort of 76 patients, 48 were found to have a germline mutation by direct sequencing; the remaining 28 were examined using multiplex ligation dependent probe amplification (MLPA) analysis to detect LKB1 copy number changes. RESULTS: Deletions were found in 11 of the 28 patients (39%)--that is, 14% of all PJS patients (11/76). Five patients had whole gene deletions, two had the promoter and exon 1 deleted, and in one patient exon 8 was deleted. Other deletions events involved: loss of exons 2-10; deletion of the promoter and exons 1-3; and loss of part of the promoter. No duplications were detected. Nine samples with deletions were sequenced at reported single nucleotide polymorphisms to exclude heterozygosity; homozygosity was found in all cases. No MLPA copy number changes were detected in 22 healthy individuals. CONCLUSIONS: These results lessen the possibility of a second PJS locus, as the detection rate of germline mutations in PJS patients was about 80% (59/76). It is suggested that MLPA, or a suitable alternative, should be used for routine genetic testing of PJS patients in clinical practice.

STK11 status and intussusception risk in Peutz-Jeghers syndrome.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is caused by germline STK11 mutations and characterised by gastrointestinal polyposis. Although small bowel intussusception is a recognised complication of PJS, risk varies between patients. OBJECTIVE: To analyse the time to onset of intussusception in a large series of PJS probands. METHODS: STK11 mutation status was evaluated in 225 PJS probands and medical histories of the patients reviewed. RESULTS: 135 (60%) of the probands possessed a germline STK11 mutation; 109 (48%) probands had a history of intussusception at a median age of 15.0 years but with wide variability (range 3.7 to 45.4 years). Median time to onset of intussusception was not significantly different between those with identified mutations and those with no mutation detected, at 14.7 years and 16.4 years, respectively (log-rank test of difference, chi(2) = 0.58, with 1df; p = 0.45). Similarly no differences were observed between patient groups on the basis of the type or site of STK11 mutation. CONCLUSIONS: The risk of intussusception in PJS is not influenced by STK11 mutation status.

Expression of the multidrug resistance-associated protein (MRP) gene in human cancers.

We determined the expression of a newly recognized drug resistance gene, the multidrug resistance-associated protein (MRP) gene, [Cole et al., Science (Washington DC), 258: 1650-1654, 1992], in normal human tissues and in >370 human tumor biopsies using a quantitative RNase protection assay and immunohistochemistry. MRP mRNA appeared to be ubiquitously expressed at low levels in all normal tissues, including peripheral blood, the endocrine glands (adrenal and thyroid), striated muscle, the lymphoreticular system (spleen and tonsil), the digestive tract (salivary gland, esophagus, liver, gall bladder, pancreas, and colon), the respiratory tract (lung), and the urogenital tract (kidney, bladder, testis, and ovary). The human cancers analyzed could be divided into three groups with regard to MRP expression. Group 1 consists of tumors that often exhibit high to very high MRP mRNA levels (e.g., chronic lymphocytic leukemia). Group 2 comprises the tumors that often exhibit low, but occasionally exhibit high MRP mRNA expression (e.g., esophagus squamous cell carcinoma, non-small cell lung cancer, and acute myelocytic leukemia). Group 3 comprises the tumors with predominantly low levels of MRP mRNA, comparable to the levels found in normal tissues (e.g., other hematological malignancies, soft tissue sarcomas, melanoma, and cancers of the prostate, breast, kidney, bladder, testis, ovary, and colon). Using the MRP-specific mAbs MRPr1 and MRPm6, we confirmed the elevated MRP mRNA levels in tumor tissues by immunohistochemistry. We conclude that hyperexpression of MRP is observed in several human cancers, and that additional studies are needed to assess the clinical relevance of MRP.

Molecular genetic alterations in hamartomatous polyps and carcinomas of patients with Peutz-Jeghers syndrome.

AIM: To investigate whether mutations in the STK11/LKB1 gene and genes implicated in the colorectal adenoma-carcinoma sequence are involved in Peutz-Jeghers syndrome (PJS) related tumorigenesis. METHODS: Thirty nine polyps and five carcinomas from 17 patients (from 13 families) with PJS were analysed for loss of heterozygosity (LOH) at 19p13.3 (STK11/LKB1 gene locus), 5q21 (APC gene locus), 18q21-22 (Smad4 and Smad2 gene locus), and 17p13 (p53 gene locus), and evaluated for immunohistochemical staining of p53. In addition, mutational analysis of K-ras codon 12, APC, and p53 and immunohistochemistry for Smad4 expression were performed on all carcinomas. RESULTS: LOH at 19p was seen in 15 of the 39 polyps and in all carcinomas (n = 5). Interestingly, six of the seven polyps from patients with cancer had LOH, compared with nine of the 31 polyps from the remaining patients (p = 0.01). In one polyp from a patient without a germline STK11/LKB1 mutation, no LOH at 19p or at three alternative PJS candidate loci (19q, 6p, and 6q) was found. No LOH at 5q was observed. However, mutational analysis revealed an APC mutation in four of the five carcinomas. LOH at 17p was not seen in polyps or carcinomas; immunohistochemistry showed expression of p53 in one carcinoma and focal expression in three polyps. At subsequent sequence analysis, no p53 mutation was found. One carcinoma had an activating K-ras codon 12 mutation and another carcinoma showed 18q LOH; however, no loss of Smad4 expression was seen. CONCLUSIONS: These results provide further evidence that STK11/LKB1 acts as a tumour suppressor gene, and may be involved in the early stages of PJS tumorigenesis. Further research is needed to see whether LOH in PJS polyps could be used as a biomarker to predict cancer. Differences in molecular genetic alterations noted between the adenoma-carcinoma sequence and PJS related tumours suggest the presence of a distinct pathway of carcinogenesis.

Molecular and phenotypic markers of hamartomatous polyposis syndromes in the gastrointestinal tract.

Hamartomatous gastrointestinal polyposis syndromes have always been considered as non-neoplastic. Nevertheless, an increased cancer risk both within and outside the gastrointestinal tract may exist in these syndromes. The hamartomatous polyps may sometimes harbor dysplasia, but their neoplastic potential is unknown. The genetic defects causing the hamartomatous syndromes are less well established than, for example, familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC). The genetic studies on the Mendelian inherited syndromes FAP and HNPCC have made a major contribution to the identification of genes involved in colorectal tumorigenesis. The genes involved in colorectal cancer development may also contribute to cancer development in the hamartomatous polyposis syndromes, and are currently under investigation. Furthermore, new insights into the development of various cancers may be obtained by the isolation and characterization of genes involved in Mendelian inherited hamartomatous polyposis syndromes. This report summarizes the available literature on this subject, and describes the pheno- and genotypic features of the hamartomatous syndromes of juvenile polyposis, Peutz-Jeghers syndrome, and Cowden's disease.

Peutz-Jeghers syndrome: risks of a hereditary condition.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare autosomal-dominant disorder characterized by hamartomatous polyposis of the gastrointestinal tract and melanin pigmentation of the skin and mucous membranes. We review the clinical features of PJS with special emphasis on the risks for its gene carriers. METHODS: Review of the literature. RESULTS: Risks imposed by the presence of polyps in PJS patients include surgical emergencies like small bowel intussusception, and chronic or acute bleeding from the polyps. As the polyps in PJS are hamartomas, the disease had in the past always been thought not to have malignant potential. However, more and more reports suggest an association of PJS with both gastrointestinal and non-gastrointestinal tumours. Whether these malignancies originate from the polyps is not clear, but the frequent occurrence of some rare extra-intestinal malignancies such as tumours of the ovary (sex cord tumours with annular tubules), cervix (adenoma malignum) and testis (Sertoli cell tumours) indicates a general susceptibility for the development of malignancies. The PJS gene, which was recently identified to encode for the serine threonine kinase STK11, is therefore thought to act as a tumour-suppressor gene. CONCLUSIONS: PJS gene carriers not only run risks of polyp-induced gastrointestinal complications, but also are at increased risk of developing cancer, both within and outside the gastrointestinal tract. As genetic identification of asymptomatic gene carriers in this relatively rare disorder becomes possible, surveillance and screening protocols need to be developed for PJS patients and their relatives.

Mutation analysis of three genes encoding novel LKB1-interacting proteins, BRG1, STRADalpha, and MO25alpha, in Peutz-Jeghers syndrome.

Mutations in LKB1 lead to Peutz-Jeghers syndrome (PJS). However, only a subset of PJS patients harbours LKB1 mutations. We performed a mutation analysis of three genes encoding novel LKB1-interacting proteins, BRG1, STRADalpha, and MO25alpha, in 28 LKB1-negative PJS patients. No disease-causing mutations were detected in the studied genes in PJS patients from different European populations.

Malignancy in Peutz-Jeghers syndrome? The pitfall of pseudo-invasion.

Peutz-Jeghers syndrome is a malignancy-associated polyposis syndrome. We describe a histopathologic phenomenon easily encountered when examining the nature of Peutz-Jeghers polyps but that is underreported in the literature. This phenomenon of "pseudo-invasion" may mimic invasive carcinoma due to epithelial displacement and erroneously give the impression, both macroscopically and microscopically, that a malignancy is involved. This potential pitfall is illustrated by the case of a patient with Peutz-Jeghers syndrome who was thought to harbor a metastasizing adenocarcinoma in his small bowel with peritoneal metastasis as a perioperative finding. Histologic examination, however, revealed pseudo-invasion.

Peutz-Jeghers polyps, dysplasia, and K-ras codon 12 mutations.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare, autosomal dominant, polyposis syndrome, associated with an increased risk of gastrointestinal and extragastrointestinal malignancy. Occasionally dysplasia occurs in PJS polyps. AIMS: In colorectal carcinomas, mutations in codon 12 of the K-ras oncogene are common and are found at similar frequency in precursor adenomas. Therefore, K-ras codon 12 point mutations in PJS polyps, were evaluated. MATERIALS AND METHODS: Fifty two PJS polyps, including four with dysplasia, collected from 19 patients with PJS, were analysed for mutations in the K-ras codon 12 by a mutant enriched polymerase chain reaction procedure, followed by allele specific oligodeoxynucleotide hybridisation. RESULTS: A K-ras codon 12 mutation was identified, in one colonic polyp with dysplasia. The mutation was found in the non-neoplasmic epithelial cells and not in the dysplastic component of the polyp. CONCLUSIONS: K-ras codon 12 point mutations are very rare in PJS polyps, by contrast with colorectal adenomas. The findings support previous evidence that there seems to be no intrinsic relation between K-ras codon 12 mutation and dysplasia.

Peutz-Jeghers syndrome: 78-year follow-up of the original family.

BACKGROUND: The association between heredity, gastrointestinal polyposis, and mucocutaneous pigmentation in Peutz-Jeghers syndrome (PJS) was first recognised in 1921 by Peutz in a Dutch family. This original family has now been followed-up for more than 78 years. We did mutation analysis in this family to test whether the recently identified LKB1 gene is indeed the PJS gene in this family. METHODS: The original family was retraced and the natural history of PJS was studied in six generations of this kindred by interview, physical examination, chart view, and histological review of tissue specimens. DNA-mutation analysis was done in all available descendants. FINDINGS: Clinical features in this family included gastrointestinal polyposis, mucocutaneous pigmentation, nasal polyposis, and rectal extrusion of polyps. Survival of affected family members was reduced by intestinal obstruction and by the development of malignant disease. A novel germline mutation in the LKB1 gene was found to cosegregate with the disease phenotype in the original family. The mutant LKB1 allele carried a T insertion at codon 66 in exon 1 resulting in frameshift and stop at codon 162 in exon 4. INTERPRETATION: The morbidity and mortality in this family suggest that PJS is not a benign disease. An inactivating germline mutation in the LKB1 gene is involved in the PJS phenotype in the original and oldest kindred known to be affected by PJS.

Germline and somatic mutations of the STK11/LKB1 Peutz-Jeghers gene in pancreatic and biliary cancers.

Peutz-Jeghers syndrome (PJS) is an autosomal-dominant disorder characterized by hamartomatous polyps in the gastrointestinal tract and by pigmented macules of the lips, buccal mucosa, and digits. Less appreciated is the fact that PJS also predisposes patients to an increased risk of gastrointestinal cancer, and pancreatic cancer has been reported in many PJS patients. It was recently shown that germline mutations of the STK11/LKB1 gene are responsible for PJS. We investigated the role of STK11/LKB1 in the development of pancreatic and biliary cancer in patients with and without the PJS. In a PJS patient having a germline splice site mutation in the STK11/LKB1 gene, sequencing analysis of an intestinal polyp and pancreatic cancer from this patient revealed loss of the wild-type allele of the STK11/LKB1 gene in the cancer. Inactivation of STK11/LKB1, by homozygous deletions or somatic sequence mutations coupled with loss of heterozygosity, was also demonstrated in 4-6% of 127 sporadic pancreatic and biliary adenocarcinomas. Our results demonstrate that germline and somatic genetic alterations of the STK11/LKB1 gene may play a causal role in carcinogenesis and that the same gene contributes to the development of both sporadic and familial forms of cancer.

Novel mutations in the LKB1/STK11 gene in Dutch Peutz-Jeghers families.

The Peutz-Jeghers syndrome (PJS) is a rare hereditary disorder in which gastrointestinal hamartomatous polyposis, mucocutaneous pigmentation, and a predisposition for developing cancer are transmitted in an autosomal dominant fashion. The recently identified LKB1/STK11 gene located at chromosome 19p13.3 is mutated in a number of PJS pedigrees. We performed mutation analysis in 19, predominantly Dutch, PJS families. In 12 of these families, we identified LKB1/STK11 mutations, none of which has been described before. These 12 novel LKB1/STK11 mutations consist of one nonsense mutation, three frameshift deletions, three frameshift insertions, two acceptor splice site mutations, and three missense mutations. In addition, we detected four polymorphisms in LKB1/STK11. In the remaining seven PJS families, we found no apparent abnormalities of the LKB1/STK1I gene, which could reflect the existence of locus heterogeneity in PJS. None of the mutations occurred in more than one family, and a number were demonstrated to have arisen de novo. The diverse array of mutations found, the apparent high mutation rate, as well as the existence of a possible second PJS locus, renders diagnostic or predictive genetic testing in individual patients difficult, although future identification of additional mutations or even gene(s) will help in increasing the yield of direct mutation analysis.