Infrequent alterations of the APC and MCC genes in gastric cancers from British patients

Wnt/β-catenin, an oncogenic pathway targeted by H. pylori in gastric carcinogenesis

A section of gastric cancers presents nuclear β-catenin accumulation correlated with H. pylori infection. H. pylori stimulate Wnt/β-catenin pathway by activating oncogenic c-Met and epidermal growth factor receptor (EGFR), or by inhibiting tumor suppressor Runx3 and Trefoil factor 1 (TFF1). H. pylori also trigger Wnt/β-catenin pathway by recruiting macrophages. Moreover, Wnt/β-catenin pathway is found involved in H. pylori-induced gastric cancer stem cell generation. Recently, by using gastroids, researchers have further revealed that H. pylori induce gastric epithelial cell proliferation through β-catenin. These findings indicate that Wnt/β-catenin is an oncogenic pathway activated by H. pylori. Therefore, this pathway is a potential therapy target for H. pylori-related gastric cancer.

Frequent inactivation of MCC/CTNNBIP1 and overexpression of phospho-beta-catenin(Y654) are associated with breast carcinoma: Clinical and prognostic significance

Transcriptional activation of β-catenin is a hallmark of Wnt/β-catenin pathway activation. The MCC (Mutated in colorectal cancers) and CTNNBIP1 (catenin, beta interacting protein 1) are two candidate genes which inhibit the transcriptional activity of nuclear β-catenin. The importance of MCC and CTNNBIP1 in breast cancer (BC) development has not yet been studied in detail. For this reason, in present study, the alterations (deletion/methylation/mutation/expression) of MCC and CTNNBIP1 were analyzed in BC of Indian patients (N=120) followed by expression/mutation analysis of β-catenin. Then transcriptional activity of β-catenin was checked by expression analysis of its target genes (EGFR, C-MYC and CCND1) in the same set of samples. Frequent methylation (44-45%) than deletion (20-32%) with overall alterations of 52-55% was observed in MCC/CTNNBIP1 in the BC samples. The alterations of MCC/CTNNBIP1 showed significant correlation with increased nuclear β-catenin/p-β-catenin(Y654) expression. Also, a significant correlation was seen between nuclear β-catenin expression and overexpression of its target genes like EGFR, MYC and CCND1 in the BC samples (P<0.0001). An upregulation of MCC and CTNNBIP1 expression by 5-Aza-2'-deoxycytidine treatment of MCF7 and MDA-MB-231 cell lines lead to downregulation of β-catenin and its target genes. The expression of nuclear p-β-catenin(Y654), EGFR, MYC and CCND1 were significantly high in TNBC (Triple negative BC) and Her2+ compared to Luminal A/B+ subtypes. The TNBC patients in stage III/IV having reduced expression of MCC in the tumors showed poor prognosis. Thus, our data suggests that inactivation of MCC/CTNNBIP1 could be an important event in activation of β-catenin mediated transcription of target genes in BC.

Mutated in colorectal cancer (MCC) is a novel oncogene in B lymphocytes

Background

Identification of novel genetic risk factors is imperative for a better understanding of B lymphomagenesis and for the development of novel therapeutic strategies. TRAF3, a critical regulator of B cell survival, was recently recognized as a tumor suppressor gene in B lymphocytes. The present study aimed to identify novel oncogenes involved in malignant transformation of TRAF3-deficient B cells.

Methods

We used microarray analysis to identify genes differentially expressed in TRAF3^−/− mouse splenic B lymphomas. We employed lentiviral vector-mediated knockdown or overexpression to manipulate gene expression in human multiple myeloma (MM) cell lines. We analyzed cell apoptosis and proliferation using flow cytometry, and performed biochemical studies to investigate signaling mechanisms. To delineate protein-protein interactions, we applied affinity purification followed by mass spectrometry-based sequencing.

Results

We identified mutated in colorectal cancer (MCC) as a gene strikingly up-regulated in TRAF3-deficient mouse B lymphomas and human MM cell lines. Aberrant up-regulation of MCC also occurs in a variety of primary human B cell malignancies, including non-Hodgkin lymphoma (NHL) and MM. In contrast, MCC expression was not detected in normal or premalignant TRAF3^−/− B cells even after treatment with B cell stimuli, suggesting that aberrant up-regulation of MCC is specifically associated with malignant transformation of B cells. In elucidating the functional roles of MCC in malignant B cells, we found that lentiviral shRNA vector-mediated knockdown of MCC induced apoptosis and inhibited proliferation in human MM cells. Experiments of knockdown and overexpression of MCC allowed us to identify several downstream targets of MCC in human MM cells, including phospho-ERK, c-Myc, p27, cyclin B1, Mcl-1, caspases 8 and 3. Furthermore, we identified 365 proteins (including 326 novel MCC-interactors) in the MCC interactome, among which PARP1 and PHB2 were two hubs of MCC signaling pathways in human MM cells.

Conclusions

Our results indicate that in sharp contrast to its tumor suppressive role in colorectal cancer, MCC functions as an oncogene in B cells. Our findings suggest that MCC may serve as a diagnostic marker and therapeutic target in B cell malignancies, including NHL and MM.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-014-0056-6) contains supplementary material, which is available to authorized users.

Subtype-specific alterations of the Wnt signaling pathway in breast cancer: clinical and prognostic significance

The aim of the study is to understand the importance of the Wnt/β-catenin pathway in the development of breast cancer (BC) and its association with different clinicopathological parameters. Alterations (deletion/methylation/expression) of some Wnt/β-catenin pathway antagonists like APC, SFRP1/2, CDH1 and activator β-catenin (CTNNB1) were analyzed in primary BC in Indian patients. High frequencies (65-70%) of overall alterations (deletion/methylation) of the antagonists were seen in the BC samples. Also, 99% (156/158) of the samples showed alterations in any one of the genes, indicating the importance of this pathway in the development of this tumor. Co-alterations of these genes were observed in 30% of samples, with significantly high alterations in late-onset (37%) and estrogen receptor (ER)-/progesterone receptor (PR)- (37%) BC compared with early onset (21%) and ER/PR+ (18%) BC samples, respectively. Significantly high (P-value = 0.001-0.02) alterations of APC and CDH1 genes were seen in ER-/PR- BC compared with ER/PR+ BC. Immunohistochemical analysis showed reduced expression of the Wnt antagonists in BC concordant with their molecular alterations. Nuclear localization of β-catenin showed significant association with alterations in the antagonists and was also significantly high in the ER-/PR- BC samples. Alterations of SFRP2 coupled with a late clinical stage and low/nulliparity predicted the worst prognosis in BC patients. Therefore, the present study suggests that cumulative alterations in more than one Wnt antagonist along with increased nuclear accumulation of β-catenin play an important role in the development of BC and have significant clinical as well as prognostic importance.

Genome-wide analysis of genetic alterations in Barrett's adenocarcinoma using single nucleotide polymorphism arrays

We performed genome-wide analysis of copy-number changes and loss of heterozygosity (LOH) in Barrett's esophageal adenocarcinoma by single nucleotide polymorphism (SNP) microarrays to identify associated genomic alterations. DNA from 27 esophageal adenocarcinomas and 14 matching normal tissues was subjected to SNP microarrays. The data were analyzed using dChipSNP software. Copy-number changes occurring in at least 25% of the cases and LOH occurring in at least 19% were regarded as relevant changes. As a validation, fluorescence in situ hybridization (FISH) of 8q24.21 (CMYC) and 8p23.1 (SOX7) was performed. Previously described genomic alterations in esophageal adenocarcinomas could be confirmed by SNP microarrays, such as amplification on 8q (CMYC, confirmed by FISH) and 20q13 or deletion/LOH on 3p (FHIT) and 9p (CDKN2A). Moreover, frequent gains were detected on 2p23.3, 7q11.22, 13q31.1, 14q32.31, 17q23.2 and 20q13.2 harboring several novel candidate genes. The highest copy numbers were seen on 8p23.1, the location of SOX7, which could be demonstrated to be involved in amplification by FISH. A nuclear overexpression of the transcription factor SOX7 could be detected by immunohistochemistry in two amplified tumors. Copy-number losses were seen on 18q21.32 and 20p11.21, harboring interesting candidate genes, such as CDH20 and CST4. Finally, a novel LOH region could be identified on 6p in at least 19% of the cases. In conclusion, SNP microarrays are a valuable tool to detect DNA copy-number changes and LOH at a high resolution. Using this technique, we identified several novel genes and DNA regions associated with esophageal adenocarcinoma.

Frameshift mutations of Wnt pathway genes AXIN2 and TCF7L2 in gastric carcinomas with high microsatellite instability

Frameshift mutations of genes with mononucleotide repeats are features of colorectal and gastric cancers with microsatellite instability (MSI). Deregulation of Wnt pathway is involved in the mechanisms of cancer development, and mutations of the Wnt-pathway genes have frequently been detected in cancers, indicating somatic mutations are important deregulation mechanisms of the Wnt signaling in cancer development. Both AXIN2 and TCF7L2 genes in the Wnt pathway possess mononucleotide repeats in their coding sequences and are considered as candidate tumor suppressor genes. The aim of this study was to see whether AXIN2 and TCF7L2 are altered by frameshift mutations in gastric carcinomas with MSI. For this, we analyzed human AXIN2 exon 8 and TCF7L2 exon 14 in 32 gastric carcinomas with high MSI, 13 gastric carcinomas with low MSI, and 47 gastric carcinomas without MSI by a single-strand conformation polymorphism analysis. Overall, we detected 9 AXIN2 and 6 TCF7L2 frameshift mutations in the mononucleotide repeats in the cancers with MSH-H, and all of them were found in MSH-H cancers (AXIN2, 28.1%; TCF7L2, 18.8%). Of the 32 high MSI cancers, 13 cancers (40.6%) harbored at least one of AXIN2 and TCF7L2 mutation, whereas 19 cancers (59.4%) harbored neither. The present data indicate that frameshift mutations in both AXIN2 and TCF7L2 genes are common in gastric carcinomas with high MSI and suggest that these mutations may contribute to development of gastric cancers with high MSI by deregulating the Wnt signaling in the affected cancer cells.

Adenomatous polyposis coli gene, beta-catenin, and E-cadherin expression in proximal and distal gastric cancers and precursor lesions: an immunohistochemical study using tissue microarrays

The aims of this study were (1) to compare protein expression of adenomatous polyposis coli (APC) gene, beta-catenin, and E-cadherin between proximal and distal gastric adenocarcinomas and (2) to investigate their use as markers of cancer risk in intestinal metaplasia (IM). The epidemiology of proximal (cardia and gastroesophageal junction) and distal (antrum and corpus) gastric carcinomas is strikingly different despite similar morphologies. Carcinoma of the distal stomach is decreasing in incidence, whereas proximal carcinomas are increasing in incidence more than any other cancer in the Western world. This phenomenon has so far not been satisfactorily explained. IM is a well-established precursor for adenocarcinoma in the distal stomach but less so in the proximal stomach. However, its specificity as a predictor of gastric carcinoma is very low. Abnormalities of APC, beta-catenin, and E-cadherin are implicated in carcinogenesis of the stomach and may show aberrant expression at early stages of the neoplastic process. This study evaluated their immunoprofiles in 3 groups: biopsies showing normal mucosa (n = 108), biopsies showing IM (n = 99), and gastric cancer resections (n = 117). In the last group, carcinoma and noninvolved mucosa were studied. All groups included material from both proximal and distal locations. The results of this study showed that there were no differences between proximal and distal locations with regard to APC, beta-catenin, or E-cadherin expression. In both locations, high normal expression rates for all 3 molecules were present in biopsies showing normal gastric mucosa or IM and noninvolved mucosa from gastric cancer resections. In carcinomas, there was a significant decrease in both APC and E-cadherin expression, whereas beta-catenin showed abnormal cytoplasmic and nuclear staining. Diffuse-type cancers showed significantly lower E-cadherin expression than intestinal types. Noninvolved mucosa from cancer resections showed normal APC, beta-catenin, and E-cadherin expression regardless of adjacent tumor type and whether the mucosa was morphologically normal or showed IM. In conclusion, proximal and distal gastric carcinomas show no differences in expression of APC, beta-catenin, or E-cadherin; thus, the observed abnormalities do not seem to contribute to the observed epidemiologic differences between these tumors. Because loss of APC, decreased E-cadherin, or abnormal beta-catenin expression did not occur in IM, even when associated with carcinoma these immunostains are unlikely to be of value in the assessment of malignant potential in IM.

Mutation analysis of APC gene in gastric cancer with microsatellite instability

AIM: To evaluate the role of APC mutation in gastric carcinogenesis and to correlate APC mutation with microsatellite instability (MSI) in gastric carcinomas.

METHODS: APC mutation was measured with multiplex PCR, denaturing gradient gel electrophoresis and DNA sequencing; and MSI was analyzed by PCR-based methods.

RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for APC mutation at exon 15 and MSI. APC mutaions were detected in 15 (22.1%) gastric cancers. Frequence of APC mutation (33.3%) in intestinal type of gastric cancer was significantly higher than that in diffuse type (13.1%, P < 0.05). On the contrary, no association was observed between APC mutation and tumor size, differentiation, depth of invasion, metastasis or clinical stages. Using five microsatellite markers, MSI in at least one locus was detected in 17 of 68 (25%) of the tumors analyzed. APC mutations were all detected in MSI-L (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51), but no mutation was found in MSI-H (≥ 2 loci, n = 8).

CONCLUSION: APC mutation is involved in carcinogenesis of intestinal type of gastric cancer and is independent of MSI phenotype but related to the LOH pathway in gastric cancer.

Genetic alterations in gastric cancers from British patients

Twenty-six gastric carcinoma and matching normal tissue DNAs, which had previously been analyzed for alterations of the APC (adenomatous polyposis coli) and MCC (mutated in colorectal cancer) genes were further investigated for the following genetic alterations: mutation and loss of heterozygosity (LOH) of the p53 gene, replication error (RER) and LOH at 12 microsatellite repeat loci, and mutation of the hMSH2 gene. In addition, 9 of the 26 gastric carcinomas were analyzed for genetic alterations using comparative genomic hybridization (CGH). Somatic mutations of the p53 gene were found to be frequent being detected in 31% of gastric carcinomas while LOH at the p53 locus was observed in 37.5% of informative cases. Loss of wild type p53 allele was detected in the majority (7 of 8) tumors found to be harboring a mutation. In the hMSH2 gene, an intronic 4 base pair insertion at 31 base pairs upstream of the beginning of exon 13 was detected in both tumor and normal tissue from one gastric carcinoma case. RER was detected in 11.5% of gastric carcinomas, at one or more microsatellite repeat loci. Of the 12 microsatellite repeat loci analyzed LOH was most frequently observed at D22S351 (30% informative cases) suggesting that a tumor suppressor gene on 22q may be important in gastric carcinogenesis. In support of this, CGH analysis carried out on 9 of the gastric carcinomas identified loss of chromosome 22 in 5 of these tumors.

Molecular biology of Barrett's adenocarcinoma

OBJECTIVE

To review the current knowledge on the genetic alterations involved in the development and progression of Barrett's esophagus-associated neoplastic lesions.

SUMMARY BACKGROUND DATA

Barrett's esophagus (BE) is a premalignant condition in which the normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. BE predisposes patients to the development of esophageal adenocarcinoma. Endoscopic surveillance can detect esophageal adenocarcinomas when they are early and curable, but most of the adenocarcinomas are detected at an advanced stage. Despite advances in multimodal therapy, the prognosis for invasive esophageal adenocarcinoma is poor. A better understanding of the molecular evolution of the Barrett's metaplasia to dysplasia to adenocarcinoma sequence may allow improved diagnosis, therapy, and prognosis.

METHODS

The authors reviewed data from the published literature to address what is known about the molecular changes thought to be important in the pathogenesis of BE-associated neoplastic lesions.

RESULTS

The progression of Barrett's metaplasia to adenocarcinoma is associated with several changes in gene structure, gene expression, and protein structure. Some of the molecular alterations already showed promise as markers for early cancer detection or prognostication. Among these, alterations in the p53 and p16 genes and cell cycle abnormalities or aneuploidy appear to be the most important and well-characterized molecular changes. However, the exact sequence of events is not known, and probably multiple molecular pathways interact and are involved in the progression of BE to adenocarcinoma.

CONCLUSIONS

Further research into the molecular biology of BE-associated adenocarcinoma will enhance our understanding of the genetic events critical for the initiation and progression of Barrett's adenocarcinoma, leading to more effective surveillance and treatment.

Cellular phenotypes of differentiated-type adenocarcinomas and precancerous lesions of the stomach are dependent on the genetic pathways

To elucidate the relationship between genetic alterations and cellular phenotypes in differentiated-type carcinomas and precancerous lesions of the stomach, mutations of p53, APC and K-ras genes were examined, as well as microsatellite instability (MSI), in 52 tumours of the stomach. Tumours were selected with the following phenotypical features, using mucin histochemical and immunohistochemical analyses, in addition to their morphological features: (1) tumours with an extremely well-preserved gastric foveolar phenotype (foveolar-type); (2) tumours with an extremely well-preserved complete-type intestinal metaplastic phenotype (CIM-type); and (3) ordinary tumours without extreme phenotypes (ordinary-type). MSI occurred in 45% of foveolar-type, 24% of ordinary-type, and 0% of CIM-type tumours. p53 gene alterations occurred in 5% of foveolar-type, 18% of ordinary-type, and 31% of CIM-type. APC gene alterations were detected in 9% of foveolar-type, 6% of ordinary-type, and 0% of CIM-type. No K-ras gene mutation was detected in any of the three types. These results indicate that the genetic pathways are quite different among the phenotypes of tumours of the stomach. The 'mutator pathway', characterized by MSI, plays an important role in the tumourigenesis of foveolar-type, but not CIM-type tumours. The 'suppressor pathway', represented by p53 alteration, could participate in the tumourigenesis of the CIM-type, but is rare in foveolar-type tumours.

Detection of microsatellite instability but not truncating APC mutations in gastric adenocarcinomas in Brazilian patients

A crucial role for the adenomatous polyposis colonic (APC) gene in colorectal carcinogenesis has been conclusively established, but, the role of APC in gastric tumors remains controversial. APC mutations have been detected at a relatively high frequency in gastric tumors of Japanese patients, yet such mutations have been reported to be extremely rare in British patients and patients from north-central-Italy. We here report the analysis of 40 primary sporadic gastric adenocarcinomas and 35 primary sporadic colon adenocarcinomas (from patients resident in São Paulo, Brazil), for mutations in the APC gene between codons 686 and 1693 using the protein truncation test. Although 19 truncating mutations were detected in 35 colon adenocarcinomas (54.2%) none were found in any of the gastric adenocarcinomas. As an internal control the tumor samples were also evaluated for microsatellite alterations, which are also common features of both tumor types. Microsatellite instability was present in 1 colon and 7 gastric tumor samples. This suggests that in relation to APC mutations gastric adenocarcinomas from Brazilian patients are similar to those that occur in Europe, and support a fundamental difference both between gastric carcinomas that occur in different geographical regions and between the molecular etiology of gastric and colorectal adenocarcinomas occurring in São Paulo, Brazil.

Assessment of hepatitis C virus sequence complexity by electrophoretic mobilities of both single-and double-stranded DNAs

To assess genetic variation in hepatitis C virus (HCV) sequences accurately, we optimized a method for identifying distinct viral clones without determining the nucleotide sequence of each clone. Twelve serum samples were obtained from seven individuals soon after they acquired HCV during a prospective study, and a 452-bp fragment from the E2 region was amplified by reverse transcriptase PCR and cloned. Thirty-three cloned cDNAs representing each specimen were assessed by a method that combined heteroduplex analysis (HDA) and a single-stranded conformational polymorphism (SSCP) method to determine the number of clonotypes (electrophoretically indistinguishable cloned cDNAs) as a measure of genetic complexity (this combined method is referred to herein as the HDA+SSCP method). We calculated Shannon entropy, incorporating the number and distribution of clonotypes into a single quantifier of complexity. These measures were evaluated for their correlation with nucleotide sequence diversity. Blinded analysis revealed that the sensitivity (ability to detect variants) and specificity (avoidance of false detection) of the HDA+SSCP method were very high. The genetic distance (mean +/- standard deviation) between indistinguishable cloned cDNAs (intraclonotype diversity) was 0.6% +/- 0.9%, and 98.7% of cDNAs differed by <2%, while the mean distance between cloned cDNAs with different patterns was 4.0% +/- 3.2%. The sensitivity of the HDA+SSCP method compared favorably with either HDA or the SSCP method alone, which resulted in intraclonotype diversities of 1.6% +/- 1.8% and 3.5% +/- 3.4%, respectively. The number of clonotypes correlated strongly with genetic diversity (R2, 0.93), but this correlation fell off sharply when fewer clones were assessed. This HDA+SSCP method accurately reflected nucleotide sequence diversity among a large number of viral cDNA clones, which should enhance analyses to determine the effects of viral diversity on HCV-associated disease. If sequence diversity becomes recognized as an important parameter for staging or monitoring of HCV infection, this method should be practical enough for use in laboratories that perform nucleic acid testing.

Optimized non-radioactive protein truncation test for mutation analysis of the adenomatous polyposis coli (APC) gene

Germline mutations in the adenomatous polyposis coli gene cause familial adenomatous polyposis, a colon cancer predisposition syndrome. More than 95% of the identified mutations result in the generation of stop codons or reading frame shifts and encode a truncated gene product, a mutation profile also found in other tumor predisposition genes such as the breast cancer or the hereditary non-polyposis coli. Therefore the protein truncation test is ideally suited for screening of mutations in these genes, starting from simple blood samples. Gene segments of interest are amplified from genomic DNA or mRNA, thereby incorporating a T7 promoter at the 5'-end. After in vitro transcription and translation of the PCR products, the resulting protein is analysed by gel electrophoresis. Truncated translation products indicate the presence of a stop mutation. We have developed a non-radioactive protein truncation test that uses a biotinylated Lys-t-RNA to label the translation products and allows a chemiluminescent detection instead of the standard radioactive method. This generic protein truncation test kit was then used to develop a parameter-specific protein truncation test for adenomatous polyposis coli. The adenomatous polyposis coli gene was divided in 5 overlapping segments, and primers were optimized to produce distinct bands with very low background in the protein truncation test. The assay was tested on 20 familial adenomatous polyposis patient samples, where 18 mutations were found, demonstrating the efficiency of this method.