High VEGF serum values are associated with locoregional spread of gastroenteropancreatic neuroendocrine tumors (GEP-NETs)

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are highly vascularized neoplasms, capable of synthethisizing VEGF-A, a key mediator of angiogenesis. In pancreatic neuroendocrine tumors (pNETs) VEGF expression is higher in benign and low-grade tumors and associated with good prognosis (neuroendocrine paradox) while the VEGF role in gastrointestinal NETs (GI-NETs) is still unclear. In this study, we examined the VEGF-1154A/G polymorphism in 145 GEP-NET patients and 150 controls. Next, we measured VEGF serum levels and VEGF tumor protein expression, comparing it with Ki67 and tumor grade. Patients' VEGF serum levels were compared with VEGF -1145A/G genotypes and metastatic status as well as with chromogranin A (CgA) and 5-hydroxyindolacetic acid (5-HIAA) in case of GI-NET patients. In this study GEP-NET patients had elevated VEGF serum values when compared to healthy controls (p = 0.0013). VEGF-1145G allele correlated with higher VEGF serum levels (p = 0.002). Patients with metastatic tumors had higher VEGF serum values when compared to patients without metastases (p = 0.033), and highest levels were observed in case of lymph node metastases (p = 0.008). VEGF-1145G allele was more frequent in non-functional GI-NET patients than in healthy controls (p = 0.041). CgA was superior to VEGF in tumor detection, while VEGF was superior to 5-HIAA. A correlation was observed between VEGF immunohistochemical staining and Ki-67 (p = 0.028). Tumours with weaker VEGF protein expression were more aggressive than tumours with stronger VEGF expression, confirming a "neuroendocrine paradox" in GI-NETs. Our results suggest the role of VEGF in GI-NETs locoregional spread.

Advanced Intestinal Cancers often Maintain a Multi-Ancestral Architecture

A widely accepted paradigm in the field of cancer biology is that solid tumors are uni-ancestral being derived from a single founder and its descendants. However, data have been steadily accruing that indicate early tumors in mice and humans can have a multi-ancestral origin in which an initiated primogenitor facilitates the transformation of neighboring co-genitors. We developed a new mouse model that permits the determination of clonal architecture of intestinal tumors in vivo and ex vivo, have validated this model, and then used it to assess the clonal architecture of adenomas, intramucosal carcinomas, and invasive adenocarcinomas of the intestine. The percentage of multi-ancestral tumors did not significantly change as tumors progressed from adenomas with low-grade dysplasia [40/65 (62%)], to adenomas with high-grade dysplasia [21/37 (57%)], to intramucosal carcinomas [10/23 (43%]), to invasive adenocarcinomas [13/19 (68%)], indicating that the clone arising from the primogenitor continues to coexist with clones arising from co-genitors. Moreover, neoplastic cells from distinct clones within a multi-ancestral adenocarcinoma have even been observed to simultaneously invade into the underlying musculature [2/15 (13%)]. Thus, intratumoral heterogeneity arising early in tumor formation persists throughout tumorigenesis.

Evidence for a heritable contribution to neuroendocrine tumors of the small intestine

Small intestinal neuroendocrine tumors (SI-NETs) are rare tumors arising from the enterochromaffin cells of the gut. Having a first-degree relative with a SI-NET has been shown to confer a substantial risk arising from shared environment and genetics. Heritable risk was examined using a computerized genealogy linked to historical statewide cancer data. A population-based analysis of the observed familial clustering of SI-NETs was performed to assess the genetic risk in distant relatives. A test for significant excess relatedness of 384 individuals with genealogy data and histologically confirmed SI-NETs was performed by comparing pairwise relatedness of cases to 1000 sets of matched controls. Overall significant excess pairwise relatedness was found for the 384 cases (P<0.001) and was still observed when closer than first cousin relationships were ignored (P=0.041). Relative risks (RRs) for SI-NETs were estimated as a ratio of observed to expected number of SI-NET cases among each relationship class. Siblings have a 13.4-fold (P<0.0001) and parents have a 6.5-fold (P=0.143) RR, suggesting both genetic and environmental influences. The risk extends out to third-degree relatives with a 2.3-fold RR (P=0.008). Metachronous cancers were also reported in 26% of the SI-NET cases demonstrating an increased RR of colon, bladder, non-Hodgkin lymphoma, melanoma, and prostate cancers. Although SI-NETs are rare, relatives of these cases are at a significantly elevated risk of developing a SI-NET due to heritable genetic factors. Definition of the genetic risk factors will be an important tool for earlier diagnosis and better outcomes for SI-NETs.

[Gastro-intestinal neuroectodermal tumor (GNET): A case report of a small intestine tumor with hepatic metastases]

The gastro-intestinal neuroectodermal tumor (GNET) is a rare sarcoma of the digestive tract, which was recently recognised. The knowledge of the morphological, immunohistochemical and molecular diagnostic criteria is necessary to not mistake it for the metastasis of a melanoma or for another sarcoma of the digestive tract as the gastro-intestinal clear cells sarcoma or the malignant peripheral nervous system tumor (MPNST). We report the case of a 41-year-old patient with a GNET of the small intestine with hepatic metastasis. The histological examination showed a diffuse proliferation of epithelioid cells, which only express PS100. The presence EWSR1-ATF1 gene fusions with any melanocytic differentiation leads to the diagnosis of GNET.

Pathologic Classification of Neuroendocrine Neoplasms

The pathologic classification of neuroendocrine neoplasms has evolved over the past decades, as new understanding of the biological behavior, histologic characteristics, and genetic features have emerged. Nonetheless, many aspects of the classification systems remain confusing or controversial. Despite these difficulties, much progress has been made in determining the features predicting behavior. Genetic findings have helped establish relationships among different types of neuroendocrine neoplasms and revealed potential therapeutic targets. This review summarizes the current approach to the diagnosis, classification, grading, and therapeutic stratification of neuroendocrine neoplasms, with a focus on those arising in the lung and thymus, pancreas, and intestines.

PAK1 modulates a PPARγ/NF-κB cascade in intestinal inflammation

P21-activated kinases (PAKs) are multifunctional effectors of Rho GTPases with both kinase and scaffolding activity. Here, we investigated the effects of inflammation on PAK1 signaling and its role in colitis-driven carcinogenesis. PAK1 and p-PAK1 (Thr423) were assessed by immunohistochemistry, immunofluorescence, and Western blot. C57BL6/J wildtype mice were treated with a single intraperitoneal TNFα injection. Small intestinal organoids from these mice and from PAK1-KO mice were cultured with TNFα. NF-κB and PPARγ were analyzed upon PAK1 overexpression and silencing for transcriptional/translational regulation. PAK1 expression and activation was increased on the luminal intestinal epithelial surface in inflammatory bowel disease and colitis-associated cancer. PAK1 was phosphorylated upon treatment with IFNγ, IL-1β, and TNFα. In vivo, mice administered with TNFα showed increased p-PAK1 in intestinal villi, which was associated with nuclear p65 and NF-κB activation. p65 nuclear translocation downstream of TNFα was strongly inhibited in PAK1-KO small intestinal organoids. PAK1 overexpression induced a PAK1-p65 interaction as visualized by co-immunoprecipitation, nuclear translocation, and increased NF-κB transactivation, all of which were impeded by kinase-dead PAK1. Moreover, PAK1 overexpression downregulated PPARγ and mesalamine recovered PPARγ through PAK1 inhibition. On the other hand PAK1 silencing inhibited NF-κB, which was recovered using BADGE, a PPARγ antagonist. Altogether these data demonstrate that PAK1 overexpression and activation in inflammation and colitis-associated cancer promote NF-κB activity via suppression of PPARγ in intestinal epithelial cells.

Roles of miR-196a on gene regulation of neuroendocrine tumor cells

This study aims at investigating miR-196a roles using in vitro models. miR-196a was detected in small intestinal neuroendocrine tumors (SI-NETs) and lung NETs. miR-196a target prediction analysis suggested HOXA9, HOXB7, LRP4 and RSPO2 genes for further investigation. The level of these four genes is detectable in SI-NET tissue specimens at different disease stages and serum samples of untreated and somatostatin analogs treated patients with liver metastases. A miR-196a inhibitor was used to silence its effects in NET cells. We show that the four target genes were significantly upregulated at transcriptional level in silenced NET cells. HOXA9, HOXB7, LRP4 and RSPO2 encoded proteins are also upregulated at translational level in miR-196a silenced NET cells. miR-196a downstream genes BMP4, ETS1, CTNNB1, FZD5, LRP5 and LRP6 were significantly upregulated at transcriptional level in miR-196a silenced CNDT2.5 and NCI-H727 cells. In addition, miR-196a clearly does not play a role in NET cell growth control.

Diet- and Genetically-Induced Obesity Differentially Affect the Fecal Microbiome and Metabolome in Apc1638N Mice

Obesity is a risk factor for colorectal cancer (CRC), and alterations in the colonic microbiome and metabolome may be mechanistically involved in this relationship. The relative contribution of diet and obesity per se are unclear. We compared the effect of diet- and genetically-induced obesity on the intestinal microbiome and metabolome in a mouse model of CRC. Apc1638N mice were made obese by either high fat (HF) feeding or the presence of the Leprdb/db (DbDb) mutation. Intestinal tumors were quantified and stool microbiome and metabolome were profiled. Genetic obesity, and to a lesser extent HF feeding, promoted intestinal tumorigenesis. Each induced distinct microbial patterns: taxa enriched in HF were mostly Firmicutes (6 of 8) while those enriched in DbDb were split between Firmicutes (7 of 12) and Proteobacteria (5 of 12). Parabecteroides distasonis was lower in tumor-bearing mice and its abundance was inversely associated with colonic Il1b production (p<0.05). HF and genetic obesity altered the abundance of 49 and 40 fecal metabolites respectively, with 5 in common. Of these 5, adenosine was also lower in obese and in tumor-bearing mice (p<0.05) and its concentration was inversely associated with colonic Il1b and Tnf production (p<0.05). HF and genetic obesity differentially alter the intestinal microbiome and metabolome. A depletion of adenosine and P.distasonis in tumor-bearing mice could play a mechanistic role in tumor formation. Adenosine and P. distasonis have previously been shown to be anti-inflammatory in the colon and we postulate their reduction could promote tumorigenesis by de-repressing inflammation.

Let-7 Represses Carcinogenesis and a Stem Cell Phenotype in the Intestine via Regulation of Hmga2

Let-7 miRNAs comprise one of the largest and most highly expressed family of miRNAs among vertebrates, and is critical for promoting differentiation, regulating metabolism, inhibiting cellular proliferation, and repressing carcinogenesis in a variety of tissues. The large size of the Let-7 family of miRNAs has complicated the development of mutant animal models. Here we describe the comprehensive repression of all Let-7 miRNAs in the intestinal epithelium via low-level tissue-specific expression of the Lin28b RNA-binding protein and a conditional knockout of the MirLet7c-2/Mirlet7b locus. This ablation of Let-7 triggers the development of intestinal adenocarcinomas concomitant with reduced survival. Analysis of both mouse and human intestinal cancer specimens reveals that stem cell markers were significantly associated with loss of Let-7 miRNA expression, and that a number of Let-7 targets were elevated, including Hmga1 and Hmga2. Functional studies in 3-D enteroids revealed that Hmga2 is necessary and sufficient to mediate many characteristics of Let-7 depletion, namely accelerating cell cycle progression and enhancing a stem cell phenotype. In addition, inactivation of a single Hmga2 allele in the mouse intestine epithelium significantly represses tumorigenesis driven by Lin28b. In aggregate, we conclude that Let-7 depletion drives a stem cell phenotype and the development of intestinal cancer, primarily via Hmga2.

Cancer develops following multiple genetic mutations (i.e. in tumor suppressors and oncogenes), and mutations that cooperate or synergize are often advantageous to cancer cell growth. To study how multiple genes might cooperate, it is usually informative to generate candidate mutations in cells or in mice. Large gene families, such as the Let-7 family, are difficult to silence or mutate because of the large amount of redundancy that exists between similar copies of the same gene; the mutation of one will often be masked or compensated by the continued function of others. In the mouse intestine we have achieved comprehensive depletion of all Let-7 miRNAs in this large multi-genic family through use of an inhibitory protein, called LIN28B, that specifically represses Let-7, and genetic inactivation of another gene cluster called MirLet7c-2/Mirlet7b. Mice with this comprehensive depletion of Let-7 develop intestinal cancers that resemble human colon cancers. Our further analysis identified another gene, HMGA2, downstream of this pathway that is critical to this outcome.

Porcupine inhibitor suppresses paracrine Wnt-driven growth of Rnf43;Znrf3-mutant neoplasia

Rnf43 (RING finger protein 43) and Znrf3 (zinc/RING finger protein 3) (RZ) are two closely related transmembrane E3 ligases, encoded by Wnt target genes, that remove surface Wnt (wingless-int) receptors. The two genes are mutated in various human cancers. Such tumors are predicted to be hypersensitive to, yet still depend on, secreted Wnts. We previously showed that mutation of RZ in the intestine yields rapidly growing adenomas containing LGR5(+) (leucine-rich repeat-containing G-protein coupled receptor 5) stem cells and Wnt3-producing Paneth cells. We now show that removal of Paneth cells by Math1 mutation inhibits RZ(-/-) tumor formation. Similarly, deletion of Wnt3 inhibits tumorigenesis. Treatment of mice carrying RZ(-/-) intestinal neoplasia with a small molecule Wnt secretion inhibitor (porcupine inhibitor C59) strongly inhibited growth, whereas adjacent normal crypts remained intact. These results establish that paracrine Wnt secretion is an essential driver of RZ(-/-) tumor growth and imply that a therapeutic window exists for the use of porcupine inhibitors for RZ-mutant cancers.

Exome Sequencing and CNV Analysis on Chromosome 18 in Small Intestinal Neuroendocrine Tumors: Ruling Out a Suspect?

The genetic background in small intestinal neuroendocrine tumors is poorly understood, but several studies have revealed numerical imbalances. Loss of one copy of chromosome 18 is the most frequent genetic aberration in this tumor type, which indirectly suggests that a driver mutation may be present in the remaining allele. The aim of this study was to evaluate the mutation status on chromosome 18 in small intestinal neuroendocrine tumors. DNAs from 7 small intestinal neuroendocrine tumors were subjected to whole exome capture, followed by next generation sequencing and high resolution SNP array followed by copy number variation analysis. Exome capture sequencing generated an average coverage of 50.6-138.2. Only 19 genes were covered less than 8X. No tumor-specific somatic mutation was identified. Genomic profiling revealed loss of chromosome 18 in 5 out of 7 small intestinal neuroendocrine tumors and a number of other aberrancies. Loss of chromosome 18 is the most frequent genetic aberration in small intestinal neuroendocrine tumors, but no evidence for eventual mutations in the remaining allele. This suggests involvement of other mechanisms than point mutations in small intestinal neuroendocrine tumors tumorigenesis.

Telomere length abnormalities and telomerase RNA component expression in gastroenteropancreatic neuroendocrine tumors

Telomere lengths in normal human cells are tightly regulated within a narrow range. Telomere length abnormalities are prevalent genetic alterations in malignant transformation. We studied telomere length abnormalities, telomerase RNA component (TERC) expression, alpha-thalassemia X-linked mental retardation (ATRX) expression, and death domain-associated protein (DAXX) expression in gastroenteropancreatic neuroendocrine tumors (GEP-NETs). We used tissue microarrays to perform telomere fluorescent in situ hybridization (FISH) and TERC in situ hybridization in 327 formalin-fixed paraffin-embedded tissues of GEP-NETs. Telomere length abnormalities were detected in 35% of 253 informative cases by using telomere FISH. Ten cases had altered lengthening of telomeres (ALT), an ALT-positive phenotype (4%), and 79 cases had telomere shortening (31%). The ALT-positive phenotype was significantly associated with tumors of pancreatic origin (7/10) and loss of ATRX or DAXX protein (8/10). Telomere shortening was significantly associated with low TERC expression. In the survival analysis, loss of ATRX or DAXX protein was associated with a decreased overall survival. Multivariate regression analysis showed that lymph node metastasis and high TERC expression were independent prognostic factors of reduced overall survival (OS) for patients with GEP-NETs. Our results showed that telomere lengthening (the ALT-positive phenotype) and telomere shortening accompanied by low TERC levels are two types of clinically significant telomere abnormalities in GEP-NETs.

Vanek’s tumor of the small bowel in adults

Inflammatory fibroid polyps (IFPs), or Vanek’s tumor, are one of the least common benign small bowel tumors. IFP affects both sexes and all age groups, with a peak of incidence in the fifth and seventh decades. They can be found throughout the gastrointestinal tract but most commonly in the gastric antrum or ileum. The underlying cause of IFPs is still unknown. Genetic study of IFP showed mutations in platelet derived growth factor alpha in some cases. At the time of diagnosis most IFPs have a diameter of 3 to 4 cm. The lesions have always been recorded as solitary polyps. Symptoms depend on the location and the size of the lesion, including abdominal pain, vomiting, altered small bowel movements, gastrointestinal bleeding and loss of weight. IFPs arising below the Treitz ligament can present with an acute abdomen, usually due to intussusceptions. Abdominal computed tomography is currently considered the most sensitive radiological method to show the polyp or to confirm intussusceptions. Most inflammatory fibroid polyps can be removed by endoscopy. Surgery is rarely needed. Exploratory laparoscopy or laparotomy is frequently recommended as the best treatment for intussusceptions caused by IFP. The operation should be performed as early as possible in order to prevent the intussusceptions from leading to ischemia, necrosis and subsequent perforation of the invaginated bowel segment. This report aims at reviewing the diagnosis, etiology, genetics, clinical presentation, endoscopy, radiology, and best treatment of IFP.

Predictive value of CHFR and MLH1 methylation in human gastric cancer

BACKGROUND

Gastric carcinoma (GC) has one of the highest mortality rates of cancer diseases and has a high incidence rate in China. Palliative chemotherapy is the main treatment for advanced gastric cancer. It is necessary to compare the effectiveness and toxicities of different regimens. This study explores the possibility of methylation of DNA damage repair genes serving as a prognostic and chemo-sensitive marker in human gastric cancer.

METHODS

The methylation status of five DNA damage repair genes (CHFR, FANCF, MGMT, MLH1, and RASSF1A) was detected by nested methylation-specific PCR in 102 paraffin-embedded gastric cancer samples. Chi-square or Fisher's exact tests were used to evaluate the association of methylation status and clinic-pathological factors. The Kaplan-Meier method and Cox proportional hazards models were employed to analyze the association of methylation status and chemo-sensitivity.

RESULTS

The results indicate that CHFR, MLH1, RASSF1A, MGMT, and FANCF were methylated in 34.3% (35/102), 21.6% (22/102), 12.7% (13/102), 9.8% (10/102), and 0% (0/102) of samples, respectively. No association was found between methylation of CHFR, MLH1, RASSF1A, MGMT, or FANCF with gender, age, tumor size, tumor differentiation, lymph node metastasis, and TNM stage. In docetaxel-treated gastric cancer patients, resistance to docetaxel was found in CHFR unmethylated patients by Cox proportional hazards model (HR 0.243, 95% CI, 0.069-0.859, p = 0.028), and overall survival is longer in the CHFR methylated group compared with the CHFR unmethylated group (log-rank, p = 0.036). In oxaliplatin-treated gastric cancer patients, resistance to oxaliplatin was found in MLH1 methylated patients (HR 2.988, 95% CI, 1.064-8.394, p = 0.038), and overall survival was longer in the MLH1 unmethylated group compared with the MLH1 methylated group (log-rank, p = 0.046).

CONCLUSIONS

CHFR is frequently methylated in human gastric cancer, and CHFR methylation may serve as a docetaxel-sensitive marker. MLH1 methylation was related to oxaliplatin resistance in gastric cancer patients.

Mucinous phenotype and CD10 expression of primary adenocarcinoma of the small intestine

AIM: To clarify the correlation with phenotypic expression, clinicopathological features, genetic alteration and microsatellite-instability status in small intestinal adenocarcinoma (SIA).

METHODS: The cases of 47 patients diagnosed with primary SIAs that were surgically resected at our institution in 1975-2005 were studied. We reviewed clinicopathological findings (age, gender, tumor size, gross appearance, histological morphologic type, invasion depth, lymphatic permeation, venous invasion, and lymph node metastasis), and the immunohistochemical expression of MUC5AC, MUC6, MUC2, CD10, and mismatch-repair (MMR) proteins (MLH1 and MSH2). We analyzed KRAS and BRAF gene mutations, and the microsatellite instability (MSI) status. The immunohistochemical staining of CD10, MUC2, MUC5AC and MUC6 was considered positive when distinct staining in > 5% of the adenocarcinoma cells was recorded. To evaluate of MMR protein expression, we used adjacent normal tissue including lymphoid follicles, inflammatory cells, and stromal cells as an internal positive control. Sections without nuclear staining in the tumor cells were considered to have lost the expression of the respective MMR protein.

RESULTS: There were 29 males and 18 females patients (mean age 59.9 years, range: 23-87 years). Tumors were located in the duodenum in 14 cases (30%), the jejunum in 21 cases (45%), and the ileum in 12 cases (25%). A phenotypic expression analysis revealed 20 MUC2-positive tumors (42.6%), 11 MUC5AC-positive (23.4%), 4 MUC6-positive (8.5%), and 7 CD10-positive (14.9%). The tumor sizes of the MUC2(+) tumors were significantly larger than those of the MUC2(-) tumors (mean, 5.7 ± 1.4 cm vs 4.7 ± 2.1 cm, P < 0.05). All three tumors with adenomatous component were positive for MUC2 (P < 0.05). Polypoid appearance was seen significantly more frequently in the CD10(+) group than in the CD10(-) group (P < 0.05). The tumor size was significantly larger in the CD10 (+) group than in the CD10(-) group (mean, 5.9 ± 1.4 cm vs 5.0 ± 2.1 cm, P < 0.05). Of 34 SIAs with successfully obtained MSI data, 4 were MSI-high. Of the 4 SIAs positive for both MUC5AC and MUC2, 3 showed MSI-H (75%) and 3 were mucinous adenocarcinoma (75%). KRAS mutations were detected in 4 SIAs. SIAs had KRAS mutation expressed only MUC2, but were negative for MUC5AC, MUC6 and CD10.

CONCLUSION: These findings suggest that the phenotypic expression of SIAs is correlated with their biological behavior, genetic alteration, and MSI status.

Retrotransposition of long interspersed nucleotide element-1 is associated with colitis but not tumors in a murine colitic cancer model

Long interspersed element-1 (L1) is a transposable element that can move within the genome, potentially leading to genome diversity and modified gene function. Although L1 activity in somatic cells is normally suppressed through DNA methylation, some L1s are activated in tumors including colorectal carcinoma. However, how L1-retrotransposition (L1-RTP) is involved in gastrointestinal disorders remains to be elucidated. We hypothesized that L1-RTP in somatic cells might contribute to colitis-associated cancer (CAC). To address this, we employed an experimental model of CAC using transgenic L1-reporter mice carrying a human L1-EGFP reporter gene. Mice were subjected to repeated cycles of colitis induced by administration of dextran sodium sulfate (DSS) in drinking water with injection of carcinogen azoxymethane (AOM). L1-RTP levels were measured by a quantitative polymerase chain reaction targeting the newly inserted reporter EGFP in various tissues and cell types, including samples obtained by laser microdissection and cell sorting with flow cytometry. DNA methylation levels of the human L1 promoter were analyzed by bisulfite pyrosequencing. AOM+DSS-treated mice exhibited significantly higher levels of L1-RTP in whole colon tissue during the acute phase of colitis when compared with control naïve mice. L1-RTP levels in whole colon tissue were positively correlated with the histological severity of colitis and degree of neutrophil infiltration into the lamina propria (LP), but not with tumor development in the colon. L1-RTP was enriched in LP mesenchymal cells rather than epithelial cells (ECs), myeloid, or lymphoid cells. DNA methylation levels of the human L1 promoter region showed a negative correlation with L1-RTP levels. L1-RTP was absent from most tumors found in 22-week-old mice. In conclusion, we demonstrated that L1-RTP was induced in the mouse CAC mucosa in accordance with the acute inflammatory response; however, retrotransposition appears not to have direct relevance to colitis-induced cancer initiation.

Actin cytoskeletal control during epithelial to mesenchymal transition: focus on the pancreas and intestinal tract

The formation of epithelial tissues allows organisms to specialise and form tissues with diverse functions and compartmentalised environments. The tight controls on cell growth and migration required to maintain epithelia can present problems such as the development and spread of cancer when normal pathways are disrupted. By attaining a deeper understanding of how cell migration is suppressed to maintain the epithelial organisation and how it is reactivated when epithelial tissues become mesenchymal, new insights into both cancer and development can be gained. Here we discuss recent developments in our understanding of epithelial and mesenchymal regulation of the actin cytoskeleton in normal and cancerous tissue, with a focus on the pancreas and intestinal tract.

mTORC1-mediated translational elongation limits intestinal tumour initiation and growth

Inactivation of APC is a strongly predisposing event in the development of colorectal cancer, prompting the search for vulnerabilities specific to cells that have lost APC function. Signalling through the mTOR pathway is known to be required for epithelial cell proliferation and tumour growth, and the current paradigm suggests that a critical function of mTOR activity is to upregulate translational initiation through phosphorylation of 4EBP1 (refs 6, 7). This model predicts that the mTOR inhibitor rapamycin, which does not efficiently inhibit 4EBP1 (ref. 8), would be ineffective in limiting cancer progression in APC-deficient lesions. Here we show in mice that mTOR complex 1 (mTORC1) activity is absolutely required for the proliferation of Apc-deficient (but not wild-type) enterocytes, revealing an unexpected opportunity for therapeutic intervention. Although APC-deficient cells show the expected increases in protein synthesis, our study reveals that it is translation elongation, and not initiation, which is the rate-limiting component. Mechanistically, mTORC1-mediated inhibition of eEF2 kinase is required for the proliferation of APC-deficient cells. Importantly, treatment of established APC-deficient adenomas with rapamycin (which can target eEF2 through the mTORC1-S6K-eEF2K axis) causes tumour cells to undergo growth arrest and differentiation. Taken together, our data suggest that inhibition of translation elongation using existing, clinically approved drugs, such as the rapalogs, would provide clear therapeutic benefit for patients at high risk of developing colorectal cancer.

High-density array comparative genomic hybridization detects novel copy number alterations in gastric adenocarcinoma

AIM

To investigate frequent quantitative alterations of intestinal-type gastric adenocarcinoma.

MATERIALS AND METHODS

We analyzed genome-wide DNA copy numbers of 22 samples and using CytoScan® HD Array.

RESULTS

We identified 22 gene alterations that to the best of our knowledge have not been described for gastric cancer, including of v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 4 (ERBB4), SRY (sex determining region Y)-box 6 (SOX6), regulator of telomere elongation helicase 1 (RTEL1) and UDP-Gal:betaGlcNAc beta 1,4- galactosyltransferase, polypeptide 5 (B4GALT5). The most significant alterations related to peritoneal invasion involved the regions 13q21.1 (gain) and 15q15.1, 17q23.1, 19q13.2 and 20q11.22 (loss of heterozygozity; LOH), where we found LOH of erythrocyte membrane protein band 4.1-like 1 (EPB41L1) gene. In relation to early age of onset, the most significant alterations were gains in the regions Xq26 and Xp22.31 and a loss in the region 11p15.4.

CONCLUSION

These quantitative changes may play a role in the development of this type of neoplasia and may be used as markers in evaluating poor prognosis, as well as act as potential therapeutic targets for gastric cancer.

Genetic testing: medico-legal issues

BACKGROUND

The availability and frequency of genetic testing is increasing. Genetic testing poses some unique ethical and legal issues for medical practitioners because of the potential to identify genetic variants that carry implications for the risk of disease in the future for the patient and their relatives. The regulatory framework within which genetic testing is provided in Australia is also changing.

OBJECTIVE

This article examines some medico-legal issues associated with genetic testing that general practitioners (GPs) are likely encounter in their practices.

DISCUSSION

There is inevitable involvement of the GP in the long term care of a patient (and possibly their family) following genetic testing, regardless of whether or not the GP has ordered the testing. Cases are presented to illustrate some of the medico-legal issues that may arise from direct-to-consumer genetic testing, information disclosure to genetic relatives and requests for parentage testing.

Cyclin B2 and p53 control proper timing of centrosome separation

Cyclins B1 and B2 are frequently elevated in human cancers and are associated with tumour aggressiveness and poor clinical outcome; however, whether and how B-type cyclins drive tumorigenesis is unknown. Here we show that cyclin B1 and B2 transgenic mice are highly prone to tumours, including tumour types where B-type cyclins serve as prognosticators. Cyclins B1 and B2 both induce aneuploidy when overexpressed but through distinct mechanisms, with cyclin B1 inhibiting separase activation, leading to anaphase bridges, and cyclin B2 triggering aurora-A-mediated Plk1 hyperactivation, resulting in accelerated centrosome separation and lagging chromosomes. Complementary experiments revealed that cyclin B2 and p53 act antagonistically to control aurora-A-mediated centrosome splitting and accurate chromosome segregation in normal cells. These data demonstrate a causative link between B-type cyclin overexpression and tumour pathophysiology, and uncover previously unknown functions of cyclin B2 and p53 in centrosome separation that may be perturbed in many human cancers.

TCEB3C a putative tumor suppressor gene of small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (SI-NETs), formerly known as midgut carcinoids, are rare and slow-growing neoplasms. Frequent loss of one copy of chromosome 18 in primary tumors and metastases has been observed. The aim of the study was to investigate a possible role of TCEB3C (Elongin A3), currently the only imprinted gene on chromosome 18, as a tumor suppressor gene in SI-NETs, and whether its expression is epigenetically regulated. Primary tumors, metastases, the human SI-NET cell line CNDT2.5, and two other cell lines were included. Immunohistochemistry, gene copy number determination by PCR, colony formation assay, western blotting, real-time quantitative RT-PCR, RNA interference, and quantitative CpG methylation analysis by pyrosequencing were performed. A large majority of tumors (33/43) showed very low to undetectable Elongin A3 expression and as expected 89% (40/45) displayed one gene copy of TCEB3C. The DNA hypomethylating agent 5-aza-2'-deoxycytidine induced TCEB3C expression in CNDT2.5 cells, in primary SI-NET cells prepared directly after surgery, but not in two other cell lines. Also siRNA to DNMT1 and treatment with the general histone methyltransferase inhibitor 3-deazaneplanocin A induced TCEB3C expression in a cell type-specific way. CpG methylation at the TCEB3C promoter was observed in all analyzed tissues and thus not related to expression. Overexpression of TCEB3C resulted in a 50% decrease in clonogenic survival of CNDT2.5 cells, but not of control cells. The results support a putative role of TCEB3C as a tumor suppressor gene in SI-NETs. Epigenetic repression of TCEB3C seems to be tumor cell type-specific and involves both DNA and histone methylation.

Chemopreventive effects of an HDAC2-selective inhibitor on rat colon carcinogenesis and APCmin/+ mouse intestinal tumorigenesis

Epigenetic modulators, particularly histone deacetylases (HDACs), are valid targets for cancer prevention and therapy. Recent studies report that HDAC2 overexpression is associated with colon tumor progression and is a potential target for colon cancer prevention. This study tested chemopreventive and dose-response effects of Ohio State University HDAC42 (OSU-HDAC42), a selective HDAC2 inhibitor, using a rat colon carcinogenesis model to assess aberrant crypt foci inhibition and a familial adenomatous polyposis model to assess intestinal tumor inhibition. Colonic aberrant crypt foci were induced by azoxymethane (AOM) (15 mg/kg body weight, once-weekly subcutaneous injections at 8 and 9 weeks age). One week after AOM treatment, groups of rats were fed an AIN-76A diet containing 0, 75, 150, and 300 ppm OSU-HDAC42 for 8 weeks, and colonic aberrant crypt foci were evaluated. To assess the inhibitory effect of OSU-HDAC42 on small-intestinal polyps and colon tumor growth, 6-week-old male C57Bl/6J-APC(min/+)mice were fed an AIN-76A diet containing 150 ppm OSU-HADC42 or 300 ppm pan-HDAC inhibitor suberoylanilide hydroxyamic acid (SAHA) for 80 days. Our results demonstrate that dietary OSU-HDAC42 produced dose-dependent inhibition of AOM-induced colonic aberrant crypt foci formation (13-50%; P < 0.01 to < 0.0001) and reduced multiple crypts with ≥ 4 crypts per focus (25-57%; P < 0.01 to < 0.0001) in F344 rats. Our findings show that 150 ppm OSU-HDAC42 significantly inhibited small-intestinal polyps (>46%; P < 0.001), with polyp size measuring >1 mm (P < 0.001), and colon tumors (>26%) in APC(min/+)mice, whereas 300 ppm SAHA showed nonsignificant inhibition. Mice fed 150 ppm OSU-HDAC42 had significantly decreased HDAC2, proliferating cell nuclear antigen, B cell lymphoma 2, cyclin-dependent kinase 2, and cell division cycle homolog 25C expression levels and increased p53 expression levels. These observations demonstrate the chemopreventive efficacy of OSU-HDAC42 against chemically induced and polyposis models of intestinal tumorigenesis.