Mucosal prolapse in the pathogenesis of Peutz-Jeghers polyposis

Low bone mineral density in Greek patients with inflammatory bowel disease: prevalence and risk factors

BACKGROUND

A high prevalence of osteopenia and osteoporosis is observed in patients with inflammatory bowel disease (IBD). Various risk factors of bone loss have been suggested in IBD. The aim of the present study was to investigate the prevalence of low bone mineral density (BMD) and to identify related risk factors in Greek patients with IBD.

METHODS

One hundred and eighteen consecutive IBD patients were included. All patients underwent bone densitometry by dual energy X-ray absorptiometry at the femoral neck and lumbar spine levels. Serum levels of 25 hydroxyvitamin D (25 OH D), 1.25 dihydroxyvitamin D (1.25 OH 2D), osteocalcin, calcitonin and homocysteine were measured in all participants.

RESULTS

Forty (33.9%) patients were normal, 55 (46.6%) were osteopenic, and 23 (19.5%) were osteoporotic. No significant differences between IBD patients with osteopenia or osteoporosis and those with normal BMD concerning the use of steroids and the examined biochemical markers were found. Statistically significant differences among the three groups were found for body mass index (BMI), age and disease duration (P=0.002, P<0.0001 and P=0.03 respectively). Multivariate analysis revealed that the most significant factors associated with BMD were age and BMI (P<0.0001). A weak but statistically significant correlation was also found for disease duration (P=0.04).

CONCLUSIONS

There is a high prevalence of osteopenia and osteoporosis in Greek patients with IBD. Low BMI, age and disease duration are the most important independent risk factors for osteoporosis in Greek IBD patients.

Loss of Par-1a/MARK3/C-TAK1 kinase leads to reduced adiposity, resistance to hepatic steatosis, and defective gluconeogenesis

Par-1 is an evolutionarily conserved protein kinase required for polarity in worms, flies, frogs, and mammals. The mammalian Par-1 family consists of four members. Knockout studies of mice implicate Par-1b/MARK2/EMK in regulating fertility, immune homeostasis, learning, and memory as well as adiposity, insulin hypersensitivity, and glucose metabolism. Here, we report phenotypes of mice null for a second family member (Par-1a/MARK3/C-TAK1) that exhibit increased energy expenditure, reduced adiposity with unaltered glucose handling, and normal insulin sensitivity. Knockout mice were protected against high-fat diet-induced obesity and displayed attenuated weight gain, complete resistance to hepatic steatosis, and improved glucose handling with decreased insulin secretion. Overnight starvation led to complete hepatic glycogen depletion, associated hypoketotic hypoglycemia, increased hepatocellular autophagy, and increased glycogen synthase levels in Par-1a(-/-) but not in control or Par-1b(-/-) mice. The intercrossing of Par-1a(-/-) with Par-1b(-/-) mice revealed that at least one of the four alleles is necessary for embryonic survival. The severity of phenotypes followed a rank order, whereby the loss of one Par-1b allele in Par-1a(-/-) mice conveyed milder phenotypes than the loss of one Par-1a allele in Par-1b(-/-) mice. Thus, although Par-1a and Par-1b can compensate for one another during embryogenesis, their individual disruption gives rise to distinct metabolic phenotypes in adult mice.

Fishing for intestinal cancer models: unraveling gastrointestinal homeostasis and tumorigenesis in zebrafish

Zebrafish has proven to be a highly versatile model for comprehensive studies of gene function in development. Given that the molecular pathways involved in epithelial carcinogenesis appear to be conserved across vertebrates, zebrafish is now considered as a valid model to study tumor biology. Development and homeostasis in multicellular organisms are dependent on a complex interplay between cell proliferation, migration, differentiation, and cell death. The Wnt signaling pathway is a major signaling pathway during embryonic development and is the key regulator of self-renewal homeostasis in several adult tissues. A large body of knowledge on adult stem-cell biology has arisen from the study of the intestinal epithelium over the past 20 years. The Wnt pathway has appeared as its principal regulator of homeostatic self-renewal. Moreover, most cancers of the intestine are caused by activating mutations in the Wnt pathway. Recently, zebrafish models have been developed to study Wnt pathway-induced cancer. An appealing avenue for cancer research in zebrafish is large-scale screens to identify chemotherapeutic and chemopreventive agents in conjunction with the in vivo imaging approaches that zebrafish affords.

Mucosal prolapse syndrome presenting as rectal polyposis

Mucosal prolapse syndrome comprises a variety of clinical and histopathological entities, with mucosal prolapse as the underlying pathogenic mechanism. Due to variable clinical, endoscopic and histopathological presentation and rareness of symptomatic mucosal prolapse, misdiagnosis resulting in delayed or inappropriate treatment is frequent. This report describes a patient initially diagnosed with a colorectal polyposis syndrome consisting of multiple rectal hyperplastic and adenomatous polyps. But after careful review of medical history and histopathology, the patient was found to have a rare variant of solitary rectal ulcer syndrome presenting as rectal polyposis. The recognition of rectal polyposis as a manifestation of solitary rectal ulcer syndrome/mucosal prolapse syndrome will improve diagnosis and treatment and prevent inappropriate management of this condition.

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.

Differential expression and regulation of ADAM17 and TIMP3 in acute inflamed intestinal epithelia

The acute phase of Crohn's disease (CD) is characterized by a large afflux of polymorphonuclear leukocytes (PMNL) into the mucosa and by the release of TNF-alpha. Conversion of inactive TNF-alpha into an active form requires the cleavage of a transmembrane TNF-alpha precursor by the TNF-alpha-converting enzyme (ADAM17), a protease mainly regulated by the tissue inhibitor of metalloproteinase 3 (TIMP3). The aim of the present study was to investigate in an in vitro model of PMNL transepithelial migration and in the intestinal mucosa of patients with CD the expression and regulation of ADAM17 and TIMP3 in intestinal epithelial cells (IEC). ADAM17 and TIMP3 expression was analyzed by Western blotting, RT-PCR, confocal microscopy, and immunohistochemistry by using the T84 model and digestive biopsies. ADAM17 expression in IEC was increased at a posttranscriptional level during the early phase (from 2 to 4 h) of PMNL transepithelial migration whereas TIMP3 was only increased 24 h later. TNF-alpha induced an early upregulation of ADAM17 in T84 cells, whereas PMNL adhesion, H(2)O(2), or epithelial tight junction opening alone did not affect the amount of ADAM17. Immunohistochemistry of intestinal biopsies revealed that strong expression of ADAM17 was associated with a high activity of CD. In contrast, TIMP3 was very poorly expressed in these biopsies. ADAM17 and TIMP3 profiling did not correlated with the NOD2/CARD15 status. The ADAM17 activity was higher both in the early phase of PMNL transepithelial migration and in active CD. These results showed early posttranscriptional upregulation of ADAM17 in IEC linked to PMNL transepithelial migration and a high activity of CD.

LKB1; linking cell structure and tumor suppression

Germ line mutations in the LKB1 tumor suppressor gene are associated with the Peutz-Jeghers polyposis and cancer syndrome. Somatic mutations in Lkb1 are observed in sporadic pulmonary, pancreatic and biliary cancers and melanomas. The LKB1 serine-threonine kinase functionally and biochemically links control of cellular structure and energy utilization through activation of the AMPK family of kinases. Lkb1 regulates cell polarity through downstream kinases including AMPKs, MARKs and BRSKs, and nutrient utilization and cellular metabolism through the AMPK-mTOR pathway. LKB1 has been shown to affect normal chromosomal segregation, TGF-beta signaling in the mesenchyme and WNT and p53 activity. Although each of the LKB1-dependent processes and downstream pathways have been individually delineated through work across a range of experimental systems, how they relate to Lkb1's role as a tumor suppressor remains to be fully explored and elucidated. The recent development of mouse cancer models harboring engineered mutations in Lkb1 have offered insights into how LKB1 may be functioning to restrain tumorigenesis and how its role as a master regulator of polarity and metabolism could contribute to its tumor suppressor function.

Peutz-Jeghers syndrome with small intestinal malignancy and cervical carcinoma

We report a case of 30-year-old woman with Peutz-Jeghers syndrome (PJS). Because of small intestinal obstruction, she received the small intestinal polypectomy in 2001, and the pathological diagnosis was Peutz-Jeghers polyp canceration (mucinous adenocarcinoma, infiltrating full-thickness of the intestine). The patient did not feel uncomfortable after 6 mo of chemotherapy and other management. We kept a follow-up study on her and found that she suffered from cervical cancer in 2007, with a pathological diagnosis of cervical adenosquamous carcinoma.The patient presented with typical features of PJS, but without a family history. The PJS accompanied with both small intestinal and cervical malignancies has not been reported so far in the world.

Epithelial Pten is dispensable for intestinal homeostasis but suppresses adenoma development and progression after Apc mutation

PTEN acts as a tumor suppressor in a range of tissue types and has been implicated in the regulation of intestinal stem cells. To study Pten function in the intestine, we used various conditional transgenic strategies to specifically delete Pten from the mouse intestinal epithelium. We show that Pten loss specifically within the adult or embryonic epithelial cell population does not affect the normal architecture or homeostasis of the epithelium. However, loss of Pten in the context of Apc deficiency accelerates tumorigenesis through increased activation of Akt, leading to rapid development of adenocarcinoma. We conclude that Pten is redundant in otherwise normal intestinal epithelium and epithelial stem cells but, in the context of activated Wnt signaling, suppresses progression to adenocarcinoma through modulation of activated Akt levels.

Is there an association between intestinal perfusion and Crohn's disease activity? A feasibility study using contrast-enhanced ultrasound

A recent study used contrast-enhanced ultrasound to assess splanchnic haemodynamics. This study investigates whether an association exists between disease activity and splanchnic transit time in patients with suspected Crohn's disease. The study protocol had the approval of the local ethics committee, and written informed consent was obtained. 18 patients (11 women; mean age, 40 years; age range, 23-69 years) with suspected or confirmed Crohn's disease were recruited prospectively. A bolus injection of an ultrasound contrast agent was given via a peripheral vein and time-intensity curves of the superior mesenteric artery and vein were analysed. Splanchnic transit time was calculated as the time interval between the rise in signal intensity to >10% above baseline value. Baseline parameters measured included the time-averaged maximum velocity and cross-sectional area of the superior mesenteric artery (SMA). Pearson correlations were used to test associations between different numeric measurements; the independent samples t-test was used to test associations between different numeric measurements; and the independent samples t-test was used to compare mean values between patients with active and inactive disease. There was a weak negative association between splanchnic transit time and the Crohn's Disease Activity Index (CDAI) (r = -0.42), which did not reach statistical significance (p = 0.13), although the mean splanchnic transit time was reduced in the active group (4.0 s vs 6.9 s). The SMA flow rate was significantly greater in active disease (37 ml s(-1) vs 22 ml s(-1); Mann-Whitney U, p = 0.02). This study demonstrates the feasibility of using contrast-enhanced ultrasound as an assessment tool for Crohn's disease.

Recent advances in colorectal cancer genetics and diagnostics

Colorectal cancer (CRC) is one of the most prevalent cancers and leading cause of cancer mortality worldwide. It is also one of the most curable cancers if detected early. This review classifies the diverse disease subtypes using various parameters including phenotypes of the polyps and describes how recent advances in genetics have impacted on disease diagnostics. For familial syndromes, the discovery of initiating mutations in the germline made personalized medicine a reality. A model linking the main tumorigenesis (Wnt/TGF-beta-BMP/LKB-1/PI3K-AKT) pathways and a strategy for gene testing are proposed. For sporadic CRC, high throughput technology has enabled the discovery of susceptibility loci that increased CRC risk. The ramifications of screening the population for susceptibility loci are discussed.

LKB1 deficiency sensitizes mice to carcinogen-induced tumorigenesis

Lkb1 is a central regulator of cell polarity and energy metabolism through its capacity to activate the AMP-activated protein kinase (AMPK)-related family of protein kinases. Germ line-inactivating mutation of Lkb1 leads to Peutz-Jeghers syndrome, which is characterized by benign hamartomas and a susceptibility to malignant epithelial tumors. Mutations in Lkb1 are also found in sporadic carcinomas, most frequently in lung cancers associated with tobacco carcinogen exposure. The basis for Lkb1-dependent tumor suppression is not defined. Here, we uncover a marked sensitivity of Lkb1 mutant mice to the chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA). Lkb1(+/-) mice are highly prone to DMBA-induced squamous cell carcinoma (SCC) of the skin and lung. Confirming a cell autonomous tumor suppressor role of Lkb1, mice with epidermal-specific Lkb1 deletion are also susceptible to DMBA-induced SCC and develop spontaneous SCC with long latency. Restoration of wild-type Lkb1 causes senescence in tumor-derived cell lines, a process that can be partially bypassed by inactivation of the Rb pathway, but not by inactivation of p53 or AMPK. Our data indicate that Lkb1 is a potent suppressor of carcinogen-induced skin and lung cancers and that downstream targets beyond the AMPK-mTOR pathway are likely mediators of Lkb1-dependent tumor suppression.

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.

Hamartomatous polyposis syndromes

The hamartomatous polyposis syndromes are a heterogeneous group of disorders that share an autosomal-dominant pattern of inheritance and are characterized by hamartomatous polyps of the gastrointestinal tract. These syndromes include juvenile polyposis syndrome, Peutz-Jeghers syndrome and the PTEN hamartoma tumor syndrome. The frequency and location of the polyps vary considerably among syndromes, as does the affected patient's predisposition to the development of gastrointestinal and other malignancies. Although the syndromes are uncommon, it is important for the clinician to recognize these disorders because they are associated with considerable morbidity and mortality, not only from malignancy but also from nonmalignant manifestations such as bleeding, intussusception, and bowel obstruction. Each hamartomatous polyposis syndrome has its own distinctive organ-specific manifestations and each requires a different surveillance strategy, which makes accurate diagnosis crucial for appropriate patient management. The availability of clinical genetic testing for these disorders means that appropriate recognition allows for timely referral for cancer genetic counseling, and often allows for predicative testing in at-risk family members. Promisingly, an understanding of the molecular pathogenesis of these disorders offers insights into the mechanisms underlying the development of sporadic malignancy, and enables rational selection of targeted therapies that warrant further investigation.

Intestinal polyposis syndromes: progress in understanding and treatment

PURPOSE OF REVIEW

Dramatic advances in the understanding of the genetic basis for inherited diseases and in diagnosis and treatment are particularly applicable to intestinal polyposis. Recent contributions have impacted our understanding of the molecular basis for the disease and improved our ability to treat them.

RECENT FINDINGS

Insights into the genetic basis of the spectrum of disease and refinement of genetic screening, diagnostic tests, and surgical management of intestinal polyposis and extraintestinal manifestations are reviewed.

SUMMARY

Our understanding of the genetic basis for the intestinal polyposis syndromes remains incomplete, but recent studies have contributed to filling in significant gaps in our knowledge. Specific genetic alterations have been identified in the majority of the 30% of patients with familial adenomatous polyposis that do not test positive for mutations in the APC gene with routine testing. A novel gene ENG has been identified in a subgroup of patients with Peutz-Jegher's syndrome and a hypothesis has been proposed to explain the pathogenesis of the mucosal defects. Technological advancements in diagnosis and treatment include the use of capsule endoscopy for screening and the minimally invasive approach to total colectomy with ileoanal pullthrough. Treatment of desmoid tumors remains a challenge, but new chemotherapy regimens show some promise in treating this rare, but devastating, extraintestinal manifestation.