Exonic STK11 deletions are not a rare cause of Peutz-Jeghers syndrome

STK11 Causative Variants and Copy Number Variations Identified in Thai Patients With Peutz-Jeghers Syndrome

Introduction Peutz-Jeghers syndrome (PJS) is a rare autosomal dominant inherited disorder caused by germline mutations in the serine-threonine kinase 11 (STK11) tumor suppressor gene. This syndrome is characterized by hamartomatous gastrointestinal polyps, mucocutaneous melanin pigmentation, and a higher risk of developing various cancers. Methods We summarized the clinical and molecular characteristics of five unrelated Thai patients with PJS. Denaturing high-performance liquid chromatography (DHPLC) screening, coupled with direct DNA sequencing and multiplex ligation-dependent probe amplification (MLPA), were applied for the molecular analysis of STK11. Results A total of four STK11 pathogenic changeswere identified in the five PJS patients, including two frameshift variants (a novel c.199dup, p.Leu67ProfsTer96 and a known c.834_835del, p.Cys278TrpfsTer6) and two types of copy number variations (CNV), exon 1 deletion and exons 2-3 deletion. Among reported STK11 exonic deletions, exon 1 and exons 2-3 deletions were found to be the two most commonly deleted exons. Conclusion All identified STK11 mutations were null mutations that were associated with more severe PJS phenotypes and cancers. This study broadens the phenotypic and mutational spectrum of STK11 in PJS.

Locally Advanced Pancreatic Ductal Adenocarcinoma: Challenges and Progress

Pancreatic ductal adenocarcinoma (PDAC) is one of the major causes of death in the Western world, and it is estimated to become the second leading cause of tumour-related mortality in the next 10 years. Among pancreatic cancers, ductal adenocarcinomas are by far the most common, characterised by a challenging diagnosis due to the lack of initial and pathognomonic clinical signs. In this scenario, non-metastatic locally advanced pancreatic cancer (LAPC) accounts for a large proportion of all new pancreatic ductal adenocarcinoma diagnoses. There is no consensus on a common definition of LAPC. Still, it usually includes tumours that are not resectable due to vascular involvement. As of today, treatment is limited, and the prognosis is very unfavourable. Curative-intent surgery remains the gold-standard even if often jeopardized by vascular involvement. Continuing progress in our understanding of LAPC genetics and immunology will permit the development of different treatments, targeted or combined, including radiation therapy, hadrontherapy, targeted immunotherapies or new chemotherapies. A multidisciplinary approach combining various fields of expertise is essential in aiming to limit disease progression as well as patient outcome. Using a narrative literature review approach, the manuscript explores the most up-to-date knowledge concerning locally advanced pancreatic ductal adenocarcinoma management.

Novel germline STK11 variants and breast cancer phenotype identified in an Indian cohort of Peutz-Jeghers syndrome

Peutz-Jeghers syndrome (PJS) caused by germline STK11 variants is a rare autosomal dominant cancer predisposition syndrome characterized by multiple gastrointestinal (GI) hamartomatous polyps, mucocutaneous pigmentation and a high inherited risk of developing GI, breast and other cancers. Despite GI and breast being the two most common PJS-associated cancer sites, the immunohistochemical (IHC) and molecular features of these tumors in carriers of STK11 variant is not known. Detailed phenotyping including tumor IHC and its correlation with comprehensive STK11 genotyping by full gene sequencing followed by large genomic rearrangement analysis was performed in an Indian PJS cohort. A total of 4 distinct STK11 pathogenic or likely pathogenic variants were identified in 10 PJS cases from 7 of the 19 families tested-in 4/5 classical PJS families and 3/14 suspected PJS families. The pathogenic STK11 variant identified was novel in 3/7 families. In addition, four distinct, likely benign variants identified in seven families were also novel. All of the four breast cancer cases in families with STK11 pathogenic variant were estrogen receptor (ER)-positive and Her2-negative. Several novel STK11 variants identified in this Indian PJS cohort highlight the need to study PJS in different populations across the world. This is the first report showing ER positivity in breast cancer in carriers of STK11 variants and needs confirmation in a larger pooled cohort of PJS associated breast cancers. This could help establish the role of chemoprevention or prophylactic oophorectomy in female carriers of STK11 pathogenic variants.

An exploration of genotype-phenotype link between Peutz-Jeghers syndrome and STK11: a review

Peutz-Jeghers Syndrome (PJS) is an autosomal dominant hereditary polyposis syndrome. Clinical features include hamartomatous polyps, mucocutaneous pigmentation and an increased predisposition towards developing malignancy. Variants in STK11, a tumour suppressor gene, located on Chromosome 19, predispose to PJS. Peutz-Jeghers Syndrome is associated with increased rates of malignancy, particularly gastrointestinal. However, PJS is also associated with increased gynaecological, testicular and thyroid papillary malignancy. Truncating variants in STK11 are thought to predispose to a more severe phenotype. Phenotype severity is based on earlier onset of gastrointestinal pathology arising from the polyps, such as intussusception or earlier onset malignancy. Missense variants are generally considered less severe than truncating variants. There remain a large number of variants of undetermined significance. Studies have attempted to correlate the location of variants with impact on protein structure and overall severity of the PJS phenotype. The results from these cohort studies have consistently found a non-random distribution of variants. Nevertheless, a consensus on phenotype severity based on variant location is yet to be established. A centralised database that collates all known variants would facilitate the interpretation of these variants, best under the governance of an international disease-specific organisation (InSiGHT). In particular, it could help explore the significance of variants based on their type or location. Understanding the genotype-phenotype link between STK11 variants and PJS could allow more personalised care for PJS patients and their families via appropriate risk stratification and personalised and targeted cancer screening.

STK11 gene analysis reveals a significant number of splice mutations in Chinese PJS patients

BACKGROUND

The combination of direct sequencing and multiple ligation-dependent probe amplification (MLPA) has resulted in an 80% detection rate of serine/threonine kinase 11 (STK11) gene mutations in Peutz-Jeghers syndrome (PJS); however, this rate varies in different ethnicities.

AIMS

To test the efficacy of the combination in Chinese patients with PJS.

METHODS

PJS probands visiting our center during one year were enrolled. Sanger sequencing and MLPA were used to detect STK11 mutations. Associations between the occurrence of severe complications and risk factors were analyzed statistically.

RESULTS

We identified 47 PJS probands. Among them, 34 received an STK11 mutation test, revealing 23 point mutations and 2 exonic deletions. Nine of the mutations were splicing errors, reflecting a significantly higher proportion (p < 0.05). Laparotomy history existed for 33 of the probands, and seven families had a history of cancer. Statistical analysis revealed no associations between the occurrence of severe complications or cancers and risk factors.

CONCLUSION

The strategy achieved a high detection rate in Chinese people, validating its effectiveness. This cohort comprised a significantly higher proportion of splicing errors, reflecting the unique genetic characteristics Chinese people. No specific genotype-phenotype relationship was noted, while the wide usage of enteroscopy would benefit PJS surveillance.

Hereditary pancreatic cancer: related syndromes and clinical perspective

Pancreatic cancer is a very aggressive disease with a poor prognosis. The majority of them are attributed to sporadic causes, especially to many modifiable risk factors such as tobacco or alcohol abuse. The principal histologic subtype of pancreatic cancer is ductal adenocarcinoma. Pancreatic neuroendocrine tumors, which constitute a more indolent entity, represent second type of pancreatic cancer in terms of incidence. Individuals with a family history of pancreatic cancer carry an increased risk of developing the disease, which may be related to an underlying hereditary component. Unfortunately, in the majority of these families the suspected germline genetic cause responsible of the disease will not be identified, but approximately in a 20% of the cases a hereditary cancer predisposition syndrome with increased risk of pancreatic cancer development can be recognized. This review will be focused on the leading hereditary cancer syndromes related to pancreatic ductal adenocarcinoma and pancreatic neuroendocrine tumors. Additionally, we will try to explain clinical aspects related to the identification of germline mutations in pancreatic cancer patients and their potential implications in oncologic treatment decisions.

A Clinical and Molecular Genetic Study in 11 Chinese Children With Peutz-Jeghers Syndrome

OBJECTIVES

Peutz-Jeghers syndrome (PJS) is caused by the germline mutations in serine/threonine kinase 11 (STK11) gene. The aim of the present study was to investigate the spectrum of STK11 gene mutations using multiplex ligation-dependent probe amplification (MLPA) assay in combination with direct sequencing in Chinese children with PJS.

METHODS

Nine children who met the clinical criteria for PJS and 2 presumed patients with PJS were enrolled in the present study. Patients' clinical information on polyp characteristics, polyp-related complications, family histories, and so on were reviewed and analyzed. After obtaining informed consent, we performed a mutation analysis of STK11 gene in 11 Chinese patients using MLPA assay and direct sequencing.

RESULTS

By means of MLPA method, we detected exonic deletions in 5 patients. In details, 1 patient had the complete deletion of all 10 exons, 3 patients showed deletions of promoter region and exon 1, and 1 patient had exon deletions from 1 to 9. By direct sequencing of the coding region of STK11 gene, we identified point mutations in 4 patients at c.548T>G/p.Leu183Arg, c.580G>T/p.Asp194Tyr, c.152_153insGG/Asp53GlyfsX12, and c.631delC/Arg211GlyfsX76, respectively, and 3 of them are novel mutations. We failed to find any mutation in left 2 patients who met the clinical criteria of PJS.

CONCLUSIONS

MLPA plus direct sequencing revealed large genomic deletions of STK11 gene in Chinese children with PJS and increased the detecting rate of STK11 gene mutations in Chinese patients with PJS. MLPA combined with direct sequencing could serve as a better strategy for the genetic diagnosis of PJS in Chinese population.

Specific Alu elements involved in a significant percentage of copy number variations of the STK11 gene in patients with Peutz-Jeghers syndrome

Peutz–Jeghers syndrome (PJS) is a rare hereditary syndrome characterized by the occurrence of hamartomatous polyps in the gastrointestinal tract, mucocutaneous pigmentation and increased risk of cancer in multiple internal organs. PJS is preconditioned by the manifestation of mutations in the STK11 gene. The majority of detected STK11 changes are small scale mutations, however recent studies showed the significant contribution of medium-sized changes commonly known as copy number variations (CNVs). Here we present a novel 7001 bps deletion of STK11 gene fragment, in which we identified the presence of breakpoints (BPs) within the Alu elements. Comparative meta-analysis with the 80 other CNV cases from 12 publications describing STK11 mutations in patients with PJS revealed the participation of specific Alu elements in all deletions of exons 2–3 so far described. Moreover, we have shown their involvement in the two other CNVs, deletion of exon 2 and deletion of exon 1–3 respectively. Deletion of exons 2–3 of the STK11 gene may prove to be the most recurrent large rearrangement causing PJS. In addition, the sequences present in its BPs may be involved in a formation of a significant percentage of the remaining gene CNVs. This gives a new insight into the conditioning of this rare disease and enables improvements in PJS genetic diagnostics.

Clinical features, endoscopic polypectomy and STK11 gene mutation in a nine-month-old Peutz-Jeghers syndrome Chinese infant

AIM: To investigate multiple polyps in a Chinese Peutz-Jeghers syndrome (PJS) infant.

METHODS: A nine-month-old PJS infant was admitted to our hospital for recurrent prolapsed rectal polyps for one month. The clinical characteristics, a colonoscopic image, the pathological characteristics of the polyps and X-ray images of the intestinal perforation were obtained. Serine threonine-protein kinase 11 (STK11) gene analysis was also performed using a DNA sample from this infant.

RESULTS: Here we describe the youngest known Chinese infant with PJS. Five polyps, including a giant polyp of approximately 4 cm × 2 cm in size, were removed from the infant’s intestine. Laparotomy was performed to repair a perforation caused by pneumoperitoneum. The pathological results showed that this child had PJS. Molecular analysis of the STK11 gene further revealed a novel frameshift mutation (c.64_65het_delAT) in exon 1 in this PJS infant.

CONCLUSION: The appropriate treatment method for multiple polyps in an infant must be carefully considered. Our results also show that the STK11 gene mutation is the primary cause of PJS.

High Resolution Melting analysis as a rapid and efficient method of screening for small mutations in the STK11 gene in patients with Peutz-Jeghers syndrome

Background

Peutz-Jeghers syndrome (PJS) is a rare hereditary syndrome characterized by the occurrence of hamartomatous polyps in the gastrointestinal tract, mucocutaneous pigmentation and increased risk of cancer in multiple internal organs. Depending on the studied population, its incidence has been estimated to range from 1:200 000 even up to 1:50 000 births. Being an autosomal disease, PJS is caused in most cases by mutations in the STK11 gene.

Methods

The majority of causative DNA changes identified in patients with PJS are small mutations and, therefore, developing a method of their detection is a key aspect in the advancement of genetic diagnostics of PJS patients. We designed 13 pairs of primers, which amplify at the same temperature and enable examination of all coding exons of the STK11 gene by the HRM analysis.

Results

In our group of 41 families with PJS small mutations of the STK11 gene were detected in 22 families (54%). In the remaining cases all of the coding exons were sequenced. However, this has not allowed to detect any additional mutations.

Conclusions

The developed methodology is a rapid and cost-effective screening tool for small mutations in PJS patients and makes it possible to detect all the STK11 gene sequence changes occurring in this group.

Large deletions and splicing-site mutations in the STK11 gene in Peutz-Jeghers Chilean families

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disorder characterized by mucocutaneous melanocytic macules, gastrointestinal hamartomatous polyposis and an increased risk of various neoplasms. Germline mutations in the serine/threonine kinase 11 (STK11) gene have been identified as a cause for PJS. The aim of this study was to characterize the genotype of Chilean PJS patients. Mutation screening of 13 patients from eight PJS families was performed using a single strand conformation polymorphism analysis, DNA sequencing and multiplex ligation-dependent probe amplification assay. The breakpoints of the genomic rearrangements were assessed by a long-range polymerase chain reaction and sequencing. The results revealed the existence of seven different pathogenic mutations in STK11 gene in seven unrelated families, including three point mutations and four large genomic deletions. Three of these point mutations (43%, 3/7) may be considered as novel. Our results showed that a germline mutation is present in STK11 in 88% of probands fulfilling the diagnostic criteria of PJS. In this study, the combination of two different experimental approaches in the screening of the STK11 in PJS, led to a higher percentage of mutation detection.

Exon-level array CGH in a large clinical cohort demonstrates increased sensitivity of diagnostic testing for Mendelian disorders

PURPOSE

Mendelian disorders are most commonly caused by mutations identifiable by DNA sequencing. Exonic deletions and duplications can go undetected by sequencing, and their frequency in most Mendelian disorders is unknown.

METHODS

We designed an array comparative genomic hybridization (CGH) test with probes in exonic regions of 589 genes. Targeted testing was performed for 219 genes in 3,018 patients. We demonstrate for the first time the utility of exon-level array CGH in a large clinical cohort by testing for 136 autosomal dominant, 53 autosomal recessive, and 30 X-linked disorders.

RESULTS

Overall, 98 deletions and two duplications were identified in 53 genes, corresponding to a detection rate of 3.3%. Approximately 40% of positive findings were deletions of only one or two exons. A high frequency of deletions was observed for several autosomal dominant disorders, with a detection rate of 2.9%. For autosomal recessive disorders, array CGH was usually performed after a single mutation was identified by sequencing. Among 138 individuals tested for recessive disorders, 10.1% had intragenic deletions. For X-linked disorders, 3.5% of 313 patients carried a deletion or duplication.

CONCLUSION

Our results demonstrate that exon-level array CGH provides a robust option for intragenic copy number analysis and should routinely supplement sequence analysis for Mendelian disorders.

Chromosome 19p13.3 deletion in a child with Peutz-Jeghers syndrome, congenital heart defect, high myopia, learning difficulties and dysmorphic features: Clinical and molecular characterization of a new contiguous gene syndrome

The Peutz-Jeghers syndrome (PJS) is an autosomal-dominant hamartomatous polyposis syndrome characterized by mucocutaneous pigmentation, gastrointestinal polyps and the increased risk of multiple cancers. The causative point mutation in the STK11 gene of most patients accounts for about 30% of the cases of partial and complete gene deletion. This is a report on a girl with PJS features, learning difficulties, dysmorphic features and cardiac malformation, bearing a de novo 1.1 Mb deletion at 19p13.3. This deletion encompasses at least 47 genes, including STK11. This is the first report on 19p13.3 deletion associated with a PJS phenotype, as well as other atypical manifestations, thereby implying a new contiguous gene syndrome.

Germline mutation analysis of STK11 gene using direct sequencing and multiplex ligation-dependent probe amplification assay in Korean children with Peutz-Jeghers syndrome

Background and Aims Peutz-Jeghers syndrome is an autosomal, dominantly inherited disease characterized by mucocutaneous hyperpigmentation and hamartomatous polyps of the gastrointestinal tract. In this study, mutation analysis of the STK11 gene was performed to establish the genetic background of Peutz-Jeghers syndrome in Korean children.Methods This study included 17 children who were diagnosed with Peutz-Jeghers syndrome based on clinical diagnostic criteria between July 2006 and December 2007.The clinical records of these children were reviewed retrospectively.Genomic DNA was extracted from the blood samples of each patient and used for direct sequencing and the MLPA (multiplex ligation-dependent probe amplification)assay.Results By direct sequencing, mutations in the STK11 gene were observed in five of 17 (29.4%) children with Peutz-Jeghers syndrome. Missense mutations were observed in four, and a frameshift mutation in one. All these mutations were present in the kinase domain of the STK11 gene. By MLPA analysis, mutations in the STK11 gene were observed in six (35.3%) children—exonic deletions were observed in five and exonic duplication in one. Conclusions The detection rate of STK11 gene mutations by direct sequencing is relatively low, even in children clinically diagnosed with Peutz-Jeghers syndrome. With the introduction of the MLPA assay as a new cytogenetic technique, large deletions and exonic duplications could also be detected in children with PJS. In the future, these results may be useful for the genetic diagnosis of Peutz-Jeghers syndrome in Korean children.

Liver kinase B1 (LKB1) in the pathogenesis of epithelial cancers

LKB1 acts as a master kinase, with its major protein targets being the family of AMPKs. Through activation of multiple signaling pathways, LKB1's main physiologic functions involve regulating cellular growth, metabolism, and polarity. Germline mutations in LKB1 result in Peutz-Jeghers Syndrome, a rare cancer susceptibility syndrome. In addition, multiple LKB1 mutations have been identified in sporadic cancers, especially those of the lung. Recent studies from a variety of murine models have helped characterize LKB1's role in the pathogenesis of epithelial cancers. In some tumor types, LKB1 might function chiefly to suppress cell growth or invasion, while in other cases, it may serve to prevent metastasis. Moreover, molecular signatures of individual tumors likely influence LKB1's operational role, as multiple studies have shown that LKB1 can synergize with other tumor suppressors and/or oncogenes to accelerate tumorigenesis. To date, LKB1 has been considered mainly a tumor suppressor; however, some studies have suggested its potential oncogenic role, mainly through the suppression of apoptosis. In short, LKB1 is a tissue and context-specific kinase. This review aims to summarize our current understanding of its role in the pathogenesis of epithelial cancers.

Germline mutation analysis of STK11 gene using direct sequencing and multiplex ligation-dependent probe amplification assay in Korean children with Peutz-Jeghers syndrome

Background and Aims Peutz-Jeghers syndrome is an autosomal, dominantly inherited disease characterized by mucocutaneous hyperpigmentation and hamartomatous polyps of the gastrointestinal tract. In this study, mutation analysis of the STK11 gene was performed to establish the genetic background of Peutz-Jeghers syndrome in Korean children.Methods This study included 17 children who were diagnosed with Peutz-Jeghers syndrome based on clinical diagnostic criteria between July 2006 and December 2007.The clinical records of these children were reviewed retrospectively.Genomic DNA was extracted from the blood samples of each patient and used for direct sequencing and the MLPA (multiplex ligation-dependent probe amplification)assay.Results By direct sequencing, mutations in the STK11 gene were observed in five of 17 (29.4%) children with Peutz-Jeghers syndrome. Missense mutations were observed in four, and a frameshift mutation in one. All these mutations were present in the kinase domain of the STK11 gene. By MLPA analysis, mutations in the STK11 gene were observed in six (35.3%) children—exonic deletions were observed in five and exonic duplication in one. Conclusions The detection rate of STK11 gene mutations by direct sequencing is relatively low, even in children clinically diagnosed with Peutz-Jeghers syndrome. With the introduction of the MLPA assay as a new cytogenetic technique, large deletions and exonic duplications could also be detected in children with PJS. In the future, these results may be useful for the genetic diagnosis of Peutz-Jeghers syndrome in Korean children.

High prevalence of germline STK11 mutations in Hungarian Peutz-Jeghers Syndrome patients

BACKGROUND

Peutz-Jeghers syndrome (PJS) is a rare autosomal dominantly inherited disease characterized by gastrointestinal hamartomatous polyposis and mucocutaneous pigmentation. The genetic predisposition for PJS has been shown to be associated with germline mutations in the STK11/LKB1 tumor suppressor gene. The aim of the present study was to characterize Hungarian PJS patients with respect to germline mutation in STK11/LKB1 and their association to disease phenotype.

METHODS

Mutation screening of 21 patients from 13 PJS families were performed using direct DNA sequencing and multiplex ligation-dependent probe amplification (MLPA). Comparative semi-quantitative sequencing was applied to investigate the mRNA-level effects of nonsense and splice-affecting mutations.

RESULTS

Thirteen different pathogenic mutations in STK11, including a high frequency of large genomic deletions (38%, 5/13), were identified in the 13 unrelated families studied. One of these deletions also affects two neighboring genes (SBNO2 and GPX4), located upstream of STK11, with a possible modifier effect. The majority of the point mutations (88%, 7/8) can be considered novel. Quantification of the STK11 transcript at the mRNA-level revealed that the expression of alleles carrying a nonsense or frameshift mutation was reduced to 30-70% of that of the wild type allele. Mutations affecting splice-sites around exon 2 displayed an mRNA processing pattern indicative of co-regulated splicing of exons 2 and 3.

CONCLUSIONS

A combination of sensitive techniques may assure a high (100%) STK11 mutation detection frequency in PJS families. Characterization of mutations at mRNA level may give a deeper insight into the molecular consequences of the pathogenic mutations than predictions made solely at the genomic level.

Breakpoint determination of 15 large deletions in Peutz-Jeghers subjects

The Peutz-Jeghers Syndrome (PJS) is an autosomal dominant polyposis disorder with increased risk of multiple cancers. STK11/LKB1 (hereafter named STK11) germline mutations account for the large majority of PJS cases whereas large deletions account for about 30% of the cases. We report here the first thorough molecular characterization of 15 large deletions identified in a cohort of 51 clinically well-characterized PJS patients. The deletions were identified by MLPA analysis and characterized by custom CGH-array and quantitative PCR to define their boundaries. The deletions, ranging from 2.9 to 180 kb, removed one or more loci contiguous to the STK11 gene in six patients, while partial STK11 gene deletions were present in the remaining nine cases. By means of DNA sequencing, we were able to precisely characterize the breakpoints in each case. Of the 30 breakpoints, 16 were located in Alu elements, revealing non-allelic homologous recombination (NAHR) as the putative mechanism for the deletions of the STK11 gene, which lays in a region with high Alu density. In the remaining cases, other mechanisms could be hypothesized, such as microhomology-mediated end-joining (MMEJ) or non-homologous end-joining (NHEJ). In conclusion we here demonstrated the non-random occurrence of large deletions associated with PJS. All our patients had a classical PJS phenotype, which shows that haploinsufficiency for SBNO2, C19orf26, ATP5D, MIDN, C19orf23, CIRBP, C19orf24,and EFNA2, does not apparently affect their clinical phenotype.

Conditional deletion of the Lkb1 gene in the mouse mammary gland induces tumour formation

Heterozygous germline mutations in the LKB1 (STK11) gene cause Peutz-Jeghers syndrome (PJS), an autosomal dominant disorder characterized by hamartomatous polyposis of the gastrointestinal tract and an increased risk of colorectal, breast, and other cancers. To model the role of LKB1 mutation in mammary tumourigenesis, we have used a conditional gene targeting strategy to generate a mouse in which exons encoding the kinase domain of Lkb1 were deleted specifically in the mammary gland. Mammary gland tumours developed in these mice with a latency of 46-85 weeks and occurred in the thoracic or inguinal glands. These tumours were grade 2 invasive ductal carcinomas or solid papillary carcinomas with histological features similar to those described in breast cancers arising in patients with PJS. This mouse model of Lkb1 deficiency provides a potentially useful tool to investigate the role of Lkb1 in tumourigenesis and to guide the development of therapeutic approaches.

Truncating mutations in Peutz-Jeghers syndrome are associated with more polyps, surgical interventions and cancers

BACKGROUND AND GOALS

Peutz-Jeghers syndrome (PJS) is a rare autosomal dominant polyposis syndrome caused by STK11 germline mutations. PJS is associated with an increased risk of cancer. In our cohort, clinical and phenotypic parameters were correlated with genotypic findings and patients were prospectively followed by surveillance.

STUDY

Thirty-one patients treated between 2000 and 2006, were evaluated. STK11 genotyping was performed and phenotypes of patients with truncating (TM) and nontruncating mutations (NTM) were compared.

RESULTS

Median age at first symptoms was 11 years and complications occurred before the age of ten in 42% of patients. STK11 mutations were detected in 16 of 22 families (12 TM; four NTM). Patients with TM had more surgical gastrointestinal (GI) interventions (p = 0.021), and female patients in the TM group had an increased risk of undergoing gynecological surgery (p = 0.016). Also, there was a trend towards a higher polyp count (p = 0.11) and earlier age at first polypectomy (p = 0.13) in the TM group. Ten carcinomas were detected in six patients resulting in a cancer risk of 65% up to the age of 65 years. Patients with TM tended to develop more cancers (p = 0.10). Importantly, our surveillance strategy used detected 50% of cancers (n = 5) at an early potentially curable stage.

CONCLUSIONS

Our study shows that almost half of PJ patients have complications early in life independent of mutational status. Patients with TM require more surgical GI interventions and tend to develop more polyps and cancers. Furthermore, close surveillance detects early stage cancers in patients. We propose that surveillance should be started as early as 8 years in all patients to avoid complications. Moreover, patients with TM may benefit from surveillance at shorter intervals.

LKB1 and AMPK family signaling: the intimate link between cell polarity and energy metabolism

Research on the LKB1 tumor suppressor protein mutated in cancer-prone Peutz-Jeghers patients has continued at a feverish pace following exciting developments linking energy metabolism and cancer development. This review summarizes the current state of research on the LKB1 tumor suppressor. The weight of the evidence currently indicates an evolutionary conserved role for the protein in the regulation of various aspects of cellular polarity and energy metabolism. We focus on studies examining the concept that both cellular polarity and energy metabolism are regulated through the conserved LKB1-AMPK signal transduction pathway. Recent studies from a variety of model organisms have given new insight into the mechanism of polyp development and cancer formation in Peutz-Jeghers patients and the role of LKB1 mutation in sporadic tumorigenesis. Conditional LKB1 mouse models have outlined a tissue-dependent context for pathway activation and suggest that LKB1 may affect different AMPK isoforms independently. Elucidation of the molecular mechanism responsible for Peutz-Jeghers syndrome will undoubtedly reveal important insight into cancer development in the larger population.

Mutations in STK11 gene in Czech Peutz-Jeghers patients

Background

Peutz-Jeghers syndrome (PJS) is an autosomal dominant hereditary disease characterized by mucocutaneous pigmentation and gastrointestinal hamartomatous polyposis. The germline mutations in the serine/threonine kinase 11 (STK11) gene have been shown to be associated with the disease. Individuals with PJS are at increased risk for development of various neoplasms. The aim of the present study was to characterize the genotype and phenotype of Czech patients with PJS.

Methods

We examined genomic DNA of 8 individuals from five Czech families by sequencing analysis of STK11 gene, covering its promotor region, the entire coding region and the splice-site boundaries, and by multiplex ligation-dependent probe amplification (MLPA) assay designed for the identification of large exonic deletions or duplications of STK11 gene.

Results

We found pathogenic mutations in STK11 gene in two families fulfilling the diagnostic criteria of PJS and in one of three sporadic cases not complying with the criteria. The patient with the frameshift mutation in STK11 gene developed aggressive gastric cancer. No other studied proband has developed a carcinoma so far.

Conclusion

Our results showed that a germline mutation of STK11 gene can be found not only in probands fulfilling the PJS diagnostic criteria, but also in some sporadic cases not complying with the criteria. Moreover, we observed a new case of aggressive gastric cancer in a young patient with a frameshift mutation of STK11 gene.

mTOR and HIF-1alpha-mediated tumor metabolism in an LKB1 mouse model of Peutz-Jeghers syndrome

Peutz-Jeghers syndrome (PJS) is a familial cancer disorder due to inherited loss of function mutations in the LKB1/ STK11 serine/threonine kinase. PJS patients develop gastrointestinal hamartomas with 100% penetrance often in the second decade of life, and demonstrate an increased predisposition toward the development of a number of additional malignancies. Among mitogenic signaling pathways, the mammalian-target of rapamycin complex 1 (mTORC1) pathway is hyperactivated in tissues and tumors derived from LKB1-deficient mice. Consistent with a central role for mTORC1 in these tumors, rapamycin as a single agent results in a dramatic suppression of preexisting GI polyps in LKB1+/- mice. However, the key targets of mTORC1 in LKB1-deficient tumors remain unknown. We demonstrate here that these polyps, and LKB1- and AMPK-deficient mouse embryonic fibroblasts, show dramatic up-regulation of the HIF-1alpha transcription factor and its downstream transcriptional targets in an rapamycin-suppressible manner. The HIF-1alpha targets hexokinase II and Glut1 are up-regulated in these polyps, and using FDG-PET, we demonstrate that LKB1+/- mice show increased glucose utilization in focal regions of their GI tract corresponding to these gastrointestinal hamartomas. Importantly, we demonstrate that polyps from human Peutz-Jeghers patients similarly exhibit up-regulated mTORC1 signaling, HIF-1alpha, and GLUT1 levels. Furthermore, like HIF-1alpha and its target genes, the FDG-PET signal in the GI tract of these mice is abolished by rapamycin treatment. These findings suggest a number of therapeutic modalities for the treatment and detection of hamartomas in PJS patients, and potential for the screening and treatment of the 30% of sporadic human lung cancers bearing LKB1 mutations.

Pediatric juvenile polyposis syndromes: an update

Colon polyps are a common finding in pediatrics and can present with rectal bleeding, abdominal pain, or polyp prolapse from the rectum. Histologically classified as hamartomas, these isolated pediatric polyps lack epithelial dysplasia and have no cancer risk. However, when polyps are present in greater numbers, or are associated with a family history of polyps or colon or other cancers, a polyposis or hereditary colorectal cancer syndrome should be considered. Using a case-based format, this article reviews the clinical features and provides updates on the three most common hamartomatous polyp syndromes of childhood: juvenile polyposis syndrome, Peutz-Jeghers syndrome, and the PTEN hamartoma tumor syndrome. Each syndrome has distinctive intestinal and extra-intestinal findings that, when present, can guide genetic counseling and testing. Lifelong cancer surveillance is crucial to disease prevention and the long-term health of these patients and their families.

Mutation screening of fumarate hydratase by multiplex ligation-dependent probe amplification: detection of exonic deletion in a patient with leiomyomatosis and renal cell cancer

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a syndrome predisposing to cutaneous and uterine leiomyomatosis as well as renal cell cancer and uterine leiomyosarcoma. Heterozygous germline mutations in the fumarate hydratase (FH, fumarase) gene are known to cause HLRCC. On occasion, no FH mutation is detected by direct sequencing, despite the evident HLRCC phenotype in a family. In the present study, to investigate whole gene or exonic deletions and amplifications in FH mutation-negative patients, we used multiplex ligation-dependent probe amplification technology. The study material comprised 7 FH mutation-negative HLRCC patients and 12 patients affected with HLRCC-associated phenotypes, including papillary RCC, early-onset RCC, uterine leiomyomas, or uterine leiomyosarcoma. A novel FH mutation, a deletion of FH exon 1 that encodes the mitochondrial signal peptide, was detected in one of the HLRCC patients (1/7). The patient with the FH mutation displayed numerous painful cutaneous leiomyomas and papillary type renal cell cancer. Our finding, together with the two patients with whole FH gene deletion who had been detected previously, suggests that exonic or whole-gene FH deletions are not a frequent cause of HLRCC syndrome.

Genetic defects underlying Peutz-Jeghers syndrome (PJS) and exclusion of the polarity-associated MARK/Par1 gene family as potential PJS candidates

LKB1/STK11 germline inactivations are identified in the majority (66-94%) of Peutz-Jeghers syndrome (PJS) patients. Therefore, defects in other genes or so far unidentified ways of LKB1 inactivation may cause PJS. The genes encoding the MARK proteins, homologues of the Par1 polarity protein that associates with Par4/Lkb1, were analyzed in this study because of their link to LKB1 and cell polarity. The genetic defect underlying PJS was determined through analysis of both LKB1 and all four MARK genes. LKB1 point mutations and small deletions were identified in 18 of 23 PJS families using direct sequencing and multiplex ligation-dependent probe amplification analysis identified exon deletions in 3 of 23 families. In total, 91% of the studied families showed LKB1 inactivation. Furthermore, a MARK1, MARK2, MARK3 and MARK4 mutation analysis and an MARK4 quantitative multiplex polymerase chain reaction analysis to identify exon deletions on another eight PJS families without identified LKB1 germline mutation did not identify mutations in the MARK genes. LKB1 defects are the major cause of PJS and genes of the MARK family do not represent alternative PJS genes. Other mechanisms of inactivation of LKB1 may cause PJS in the remaining families.

Do sporadic Peutz-Jeghers polyps exist? Experience of a large teaching hospital

Most types of sporadic gastrointestinal (GI) polyps vastly outnumber their syndromic counterparts. In contrast, the incidence of sporadic Peutz-Jeghers polyps (PJP) is unknown. We examined all potential PJP seen at our hospital over a 22-year (y) period to assess the incidence of sporadic PJP. The pathology database of a large hospital was searched for "Peutz-Jeghers polyp(s)," yielding 121 polyps from 38 patients. The polyps were reviewed by 3 pathologists to confirm the diagnosis. Clinical information to confirm or refute a diagnosis of Peutz-Jeghers syndrome (PJS) was collected. Of the 102 polyps included after histologic review, 94 polyps arose in patients meeting the World Health Organization criteria for PJS. These PJS polyps were eliminated from further analysis. Clinical information was obtained for the remaining 8 patients with potential "sporadic" PJP (1 to 50 y; mean=14 y; median=4 y). Of the 8 potential sporadic PJP, only 3 polyps from 3 patients had unequivocal PJP histologic features, all from the small intestine. All 3 patients had clinical histories suggesting syndromic PJP although they did not meet World Health Organization criteria, that is, 2 developed pancreatic cancer, 1 had bilateral "ovarian cystic masses" and a glomus tympanicum tumor, and 1 had strong family history of GI malignancies. The 5 remaining patients each had a colonic polyp with features suggestive, but not definitely diagnostic of, PJP. In these cases, prolapse lesions could not be excluded. One patient had a history of high-grade dysplasia in a tubulovillous adenoma in the colon at 53 years, but no family cancer history. Another had a family GI cancer history. Another had a history of pituitary adenoma at age 39, and the last had ductal breast carcinoma diagnosed 4 years before the discovery of the polyp. Our findings suggest that if sporadic PJP exist, they are extremely rare. Moreover, our data suggest that individuals with a single PJP may have a cumulative lifetime risk of cancer similar to those with the syndrome.

A role for LKB1 gene in human cancer beyond the Peutz-Jeghers syndrome

Germline LKB1 mutations are responsible for Peutz-Jeghers syndrome (PJS). Tumors at several locations frequently arise in these patients, confirming that LKB1 is linked to cancer predisposition and is therefore a bona fide tumor-suppressor gene. In humans, the LKB1 gene is located in the short arm of chromosome 19, which is frequently deleted in many tumors of sporadic origin. However, LKB1 alterations in tumors other than those of PJS are rarely reported. Notably, this is not the case for non-small-cell lung cancer, where nearly half of the tumors harbor somatic and homozygous inactivating mutations in LKB1. The present review considers the frequency and pattern of LKB1 gene mutations in sporadic cancers of various origins, and the role of the encoded protein in cancer development.

The patient with multiple intestinal polyps

The management of patients with multiple intestinal polyps may be difficult and greatly depends on the correct classification. Polyposis syndromes account for less than 1% of newly diagnosed colorectal cancers. In addition the risk for extracolonic cancer is increased in most syndromes. Here we report the case of a difficult patient with severe gastric polyposis and we present a review of polyposis syndromes such as classical and attenuated familial adenomatous polyposis (FAP), MYH-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis as well as rare polyposis syndromes. The most practical approach for the diagnostic workup in patients with newly diagnosed gastrointestinal polyposis is based on the histological typing of polyps. In addition, a detailed family history regarding cancer, polyps and congenital abnormalities should be obtained from every polyposis patient. Patients with multiple adenomas are most likely to suffer from FAP, AFAP or MAP. Of these, younger age and higher polyp count are most likely a diagnosis of typical FAP. Older age and fewer polyps favour a diagnosis of AFAP or MAP. Germline testing of the APC gene is suggested, and if negative, MYH gene testing should be done. In patients with hamartomas, extraintestinal features should be evaluated and reference histology should be initiated. In addition panintestinal imaging should be performed with EGD, colonoscopy and small bowel imaging (PE, CE, and MR) enteroclysis. For diagnostic and therapeutic problems a familial colorectal cancer center should be consulted. Using this algorithm, correct classification and adequate treatment should be possible for every polyposis patient.

Prevalence and specificity of LKB1 genetic alterations in lung cancers

Germline LKB1 mutations cause Peutz-Jeghers syndrome, a hereditary disorder that predisposes to gastrointestinal hamartomatous polyposis and several types of malignant tumors. Somatic LKB1 alterations are rare in sporadic cancers, however, a few reports showed the presence of somatic alterations in a considerable fraction of lung cancers. To determine the prevalence and the specificity of LKB1 alterations in lung cancers, we examined a large number of lung cancer cell lines and lung adenocarcinoma (AdC) specimens for the alterations. LKB1 genetic alterations were frequently detected in the cell lines (21/70, 30%), especially in non-small cell lung cancers (NSCLCs) (20/51, 39%), and were significantly more frequent in cell lines with KRAS mutations. Point mutations were detected only in AdCs and large cell carcinomas, whereas homozygous deletions were detected in all histological types of lung cancer. Among lung AdC specimens, LKB1 mutations were found in seven (8%) of 91 male smokers but in none of 64 females and/or nonsmokers, and were significantly more frequent in poorly differentiated tumors. The difference in the frequency of LKB1 alterations between cell lines and tumor specimens was likely to be owing to masking of deletions by the contamination of noncancerous cells in the tumor specimens. These results indicate that somatic LKB1 genetic alterations preferentially occur in a subset of poorly differentiated lung AdCs that appear to correlate with smoking males.

More than just a bump: the hamartoma syndromes

The hamartoma syndromes detailed in this review are just a few examples of the many genodermatoses now known to be associated with uncontrolled tumor proliferation secondary to mutations in tumor suppressor genes. Knowledge gained through the study of these syndromes has not only improved our understanding of patients afflicted with such conditions, but has also led to significant insight into the important role tumor suppressor genes play in preventing tumor formation and in carcinogenesis. As major strides continue to be made in the identification of causative mutations in the hamartoma syndromes, options for genetic testing will continue to expand. Identification of mutations in PTEN in the various disorders that compose the PTEN hamartoma tumor syndrome illustrates just how such genetic knowledge has altered the way we both categorize and manage certain genetic conditions. As advances continue to be made in this arena, it is quite conceivable that many of the genetic syndromes will be renamed or categorized based on genetic mutations rather than the characteristic clinical features. However, despite these advances, it will still be the astute clinician's recognition of key clinical features that allows the diagnosis of a hamartoma syndrome to be considered.

Deletions in CCM2 are a common cause of cerebral cavernous malformations

Cerebral cavernous malformations (CCMs) are vascular abnormalities of the brain that can result in a variety of neurological disabilities, including hemorrhagic stroke and seizures. Mutations in the gene KRIT1 are responsible for CCM1, mutations in the gene MGC4607 are responsible for CCM2, and mutations in the gene PDCD10 are responsible for CCM3. DNA sequence analysis of the known CCM genes in a cohort of 63 CCM-affected families showed that a high proportion (40%) of these lacked any identifiable mutation. We used multiplex ligation-dependent probe analysis to screen 25 CCM1, -2, and -3 mutation-negative probands for potential deletions or duplications within all three CCM genes. We identified a total of 15 deletions: 1 in the CCM1 gene, 0 in the CCM3 gene, and 14 in the CCM2 gene. In our cohort, mutation screening that included sequence and deletion analyses gave disease-gene frequencies of 40% for CCM1, 38% for CCM2, 6% for CCM3, and 16% with no mutation detected. These data indicate that the prevalence of CCM2 is much higher than previously predicted, nearly equal to CCM1, and that large genomic deletions in the CCM2 gene represent a major component of this disease. A common 77.6-kb deletion spanning CCM2 exons 2-10 was identified, which is present in 13% of our entire CCM cohort. Eight probands exhibit an apparently identical recombination event in the CCM2 gene, involving an AluSx in intron 1 and an AluSg distal to exon 10. Haplotype analysis revealed that this CCM2 deletion occurred independently at least twice in our families. We hypothesize that these deletions occur in a hypermutable region because of surrounding repetitive sequence elements that may catalyze the formation of intragenic deletions.

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.

An updated mutation spectrum in an Australian series of PJS patients provides further evidence for only one gene locus

The genetic predisposition Peutz-Jeghers Syndrome (PJS) has been shown to be associated with mutations in the serine threonine kinase 11 (STK11) gene but only a proportion of probands have been shown to harbour changes in the gene. The remaining patients were proposed to be either associated with a second PJS gene or they harboured more cryptic mutations within the STK11 gene itself. With the introduction of the multiplex ligation probe amplification (MLPA) assay, large sequence losses or gains can be more readily identified. In this report we have screened 33 PJS patients from unrelated families, employing a combination of denaturing high-performance liquid chromatography, direct DNA sequencing and the MLPA assay to identify deleterious changes in the STK11 gene. The results revealed that 24 (73%) of patients diagnosed with PJS-harboured pathogenic mutations in the STK11 gene, including 10 (36%) with exonic or whole-gene deletions. No phenotypic differences were identified in patients harbouring large deletions in the STK11 gene compared to patients harbouring missense or nonsense mutations. Mutation analysis in PJS should include techniques such as MLPA to identify large exonic or whole-gene deletions and rearrangements. The high proportion of families with identifiable mutations in the STK11 gene using this range of techniques suggests that most, if not all PJS, is attributable to mutations in the STK11 gene, perhaps including as yet undiscovered changes in promoter or enhancer sequences or other cryptic changes.

The LKB1 tumor suppressor kinase in human disease

Inactivating germline mutations in the LKB1 gene underlie Peutz-Jeghers syndrome characterized by hamartomatous polyps and an elevated risk for cancer. Recent studies suggest the involvement of LKB1 also in more common human disorders including diabetes and in a significant fraction of lung adenocarcinomas. These observations have increased the interest towards signaling pathways of this tumor suppressor kinase. The recent breakthroughs in understanding the molecular functions of the LKB1 indicate its contribution as a regulator of cell polarity, energy metabolism and cell proliferation. Here we review how the substrates and cellular functions of LKB1 may be linked to Peutz-Jeghers syndrome and other diseases, and discuss how some of the molecular changes associated with altered LKB1 signaling might be used in therapeutic approaches.

Frequency and spectrum of cancers in the Peutz-Jeghers syndrome

BACKGROUND

Although an increased cancer risk in Peutz-Jeghers syndrome is established, data on the spectrum of tumors associated with the disease and the influence of germ-line STK11/LKB1 (serine/threonine kinase) mutation status are limited.

EXPERIMENTAL DESIGN

We analyzed the incidence of cancer in 419 individuals with Peutz-Jeghers syndrome, and 297 had documented STK11/LKB1 mutations.

RESULTS

Ninety-six cancers were found among individuals with Peutz-Jeghers syndrome. The risk for developing cancer at ages 20, 30, 40, 50, 60, and 70 years was 2%, 5%, 17%, 31%, 60%, and 85%, respectively. The most common cancers represented in this analysis were gastrointestinal in origin, gastroesophageal, small bowel, colorectal, and pancreatic, and the risk for these cancers at ages 30, 40, 50, and 60 years was 1%, 9%, 15%, and 33%, respectively. In women with Peutz-Jeghers syndrome, the risk of breast cancer was substantially increased, being 8% and 31% at ages 40 and 60 years, respectively. Kaplan-Meier analysis showed that cancer risks were similar in Peutz-Jeghers syndrome patients with identified STK11/LKB1 mutations and those with no detectable mutation (log-rank test of difference chi2 = 0.62; 1 df; P = 0.43). Furthermore, the type or site of STK11/LKB1 mutation did not significantly influence cancer risk.

CONCLUSIONS

The results from our study provide quantitative information on the spectrum of cancers and risks of specific cancer types associated with Peutz-Jeghers syndrome.