Genetic profiling of colon cancer

Myeloid TGF-β signaling contributes to colitis-associated tumorigenesis in mice

Myeloid cells have a critical role in maintaining intestinal homeostasis and regulating the development of inflammatory bowel disease and colitis-associated cancer (CAC). However, the signaling pathways that control the function of colonic myeloid cells in these pathological processes are still poorly defined. In this study, we demonstrate that transforming growth factor-β (TGF-β) signaling in colonic myeloid cells is significantly involved in the development of CAC. Myeloid TGF-β receptor II (Tgfbr2)-deficient mice showed reduced susceptibility to chemically induced colitis-associated tumorigenesis, as evidenced by decreases in number and size of tumors. Myeloid Tgfbr2 deficiency markedly decreased the production of interleukin-6 and tumor necrosis factor-α, two proinflammatory cytokines that are essential for colonic tumorigenesis; in addition, a marked increase in the proportions of Foxp3+CD4+ regulatory T cells was observed in the colonic lamina propria in the initial stage of CAC. Loss of myeloid Tgfbr2 was associated with a decrease in the presence of F4/80 positive macrophages and a downregulation of phosphorylated STAT3, proliferative cell nuclear antigen and cyclin D1 expression in colonic adenoma tissues. TGF-β enhanced macrophage recruitment, at least in part, through modulating the expression of the chemokine (C-C motif) receptor 2 (CCR2) ligands in tumor environment and the CCR2 signaling in macrophages. Collectively, these results suggest that myeloid TGF-β signaling modulates intestinal inflammation and significantly promotes tumorigenesis in the development of colitis-associated colon cancer.

Type III TGF-β receptor enhances colon cancer cell migration and anchorage-independent growth

The type III TGF-β receptor (TβRIII or betagylcan) is a TGF-β superfamily coreceptor with emerging roles in regulating TGF-β superfamily signaling and cancer progression. Alterations in TGF-β superfamily signaling are common in colon cancer; however, the role of TβRIII has not been examined. Although TβRIII expression is frequently lost at the message and protein level in human cancers and suppresses cancer progression in these contexts, here we demonstrate that, in colon cancer, TβRIII messenger RNA expression is not significantly altered and TβRIII expression is more frequently increased at the protein level, suggesting a distinct role for TβRIII in colon cancer. Increasing TβRIII expression in colon cancer model systems enhanced ligand-mediated phosphorylation of p38 and the Smad proteins, while switching TGF-β and BMP-2 from inhibitors to stimulators of colon cancer cell proliferation, inhibiting ligand-induced p21 and p27 expression. In addition, increasing TβRIII expression increased ligand-stimulated anchorage-independent growth, a resistance to ligand- and chemotherapy-induced apoptosis, cell migration and modestly increased tumorigenicity in vivo. In a reciprocal manner, silencing endogenous TβRIII expression decreased colon cancer cell migration. These data support a model whereby TβRIII mediates TGF-β superfamily ligand-induced colon cancer progression and support a context-dependent role for TβRIII in regulating cancer progression.

Epigenetic inactivation of the NORE1 gene correlates with malignant progression of colorectal tumors

Background

NORE1 (RASSF5) is a newly described member of the RASSF family with Ras effector function. NORE1 expression is frequently inactivated by aberrant promoter hypermethylation in many human cancers, suggesting that NORE1 might be a putative tumor suppressor. However, expression and mutation status of NORE1 and its implication in colorectal tumorigenesis has not been evaluated.

Methods

Expression, mutation, and methylation status of NORE1A and NORE1B in 10 cancer cell lines and 80 primary tumors were characterized by quantitative PCR, SSCP, and bisulfite DNA sequencing analyses. Effect of NORE1A and NORE1B expression on tumor cell growth was evaluated using cell number counting, flow cytometry, and colony formation assays.

Results

Expression of NORE1A and NORE1B transcript was easily detectable in all normal colonic epithelial tissues, but substantially decreased in 7 (70%) and 4 (40%) of 10 cancer cell lines and 31 (38.8%) and 25 (31.3%) of 80 primary carcinoma tissues, respectively. Moreover, 46 (57.6%) and 38 (47.5%) of 80 matched tissue sets exhibited tumor-specific reduction of NORE1A and NORE1B, respectively. Abnormal reduction of NORE1 was more commonly observed in advanced stage and high grade tumors compared to early and low grade tumors. While somatic mutations of the gene were not identified, its expression was re-activated in all low expressor cells after treatment with the demethylating agent 5-aza-dC. Bisulfite DNA sequencing analysis of 31 CpG sites within the promoter region demonstrated that abnormal reduction of NORE1A is tightly associated with promoter CpG sites hypermethylation. Moreover, transient expression and siRNA-mediated knockdown assays revealed that both NORE1A and NORE1B decrease cellular growth and colony forming ability of tumor cells and enhance tumor cell response to apoptotic stress.

Conclusion

Our data indicate that epigenetic inactivation of NORE1 due to aberrant promoter hypermethylation is a frequent event in colorectal tumorigenesis and might be implicated in the malignant progression of colorectal tumors.

Selective suicide gene therapy of colon cancer exploiting the urokinase plasminogen activator receptor promoter

Colon cancer is the third and fourth most prevalent cancer among Iranian men and women, respectively. Suicide gene therapy is one of the alternative therapeutic modalities for cancer. The application of specific promoters for therapeutic genes should decrease the adverse effects of this modality. The combined aims of this study were to design a specific suicide gene therapy construct for colon cancer and study its effect in distinct representatives of transformed and nontransformed cells. The KRAS oncogene signaling pathway is one of the most important signaling pathways activated in colon cancer; therefore, we inserted the urokinase plasminogen activator receptor (uPAR; PLAUR gene) promoter as one of the upregulated promoters by this pathway upstream of a suicide gene (thymidine kinase [TK]) and a reporter gene (beta-galactosidase, beta-gal [LacZ]). This promoter is a natural combination of different motifs responsive to the RAS signaling pathway, such as the transcription factors AP1 (FOS/JUN), SP1, SP3, and AP2alpha, and nuclear factor kappa B (NFkappaB). The reporter plasmid under the control of the uPAR promoter (PUCUPARLacZ) had the ability to express beta-gal in colon cancer cells (human colon adenocarcinoma [SW480] and human colorectal carcinoma [HCT116] cell lines), while it could not express beta-gal in nontransformed human umbilical vein endothelial cells (HUVEC) and normal colon cells. After confirming the ability of pUCUPARTK (suicide plasmid) to express TK in SW480 and HCT116 cells by real-time PCR, cytotoxicity assays showed that pUCUPARTK decreased the viability of these cells in the presence of ganciclovir 20 and 40 microg/mL (and higher), respectively. Although M30 CytoDEATH antibody could not detect a significant rate of apoptosis induced by ganciclovir in pUCUPARTK-transfected HCT116 cells, the percentage of stained cells was marked in comparison with untreated cells. While this antibody could detect apoptosis in HCT116 cell line transfected with positive control plasmid, it could not detect apoptosis in SW480 cells transfected with the same positive control. This discrepancy could be attributed to the different mechanisms of TK/ganciclovir-induced apoptosis in tumor protein p53 (TP53)-expressing (HCT116) and -deficient (SW480) cells. Annexin-propidium iodide staining could detect apoptosis in treated, pUCUPARTK-transfected SW480 and HCT116 cells. This study showed that the uPAR promoter can be considered as a suitable candidate for specific suicide gene therapy of colon cancer and probably other cancers in which the RAS signaling pathway is involved in their carcinogenesis process.

Pathologic classification and clinical behavior of the spectrum of goblet cell carcinoid tumors of the appendix

Appendiceal tumors exhibiting both neuroendocrine and glandular differentiation are uncommon and have caused difficulty in pathologic classification, prediction of prognosis, and clinical management. Previously, such lesions have been variously designated as adenocarcinoid, goblet cell carcinoid (GCC), and mixed adenocarcinoma carcinoid. In this study, we undertook a retrospective investigation of 63 such cases and classified them as typical GCC (group A) and adenocarcinoma ex GCC on the basis of the histologic features of the tumor at the primary site. The adenocarcinoma ex GCC group was further divided into signet ring cell type (group B) and poorly differentiated adenocarcinoma type (group C). The clinical characteristics and prognosis were compared within these groups and with conventional de novo appendiceal adenocarcinomas. Both groups A and B tumors shared a similar immunoprofile, which included generally focal immunoreactivity for neuroendocrine markers, and a normal intestinal type mucin glycoprotein profile (negative MUC1 expression and preserved MUC2 immunoreactivity). The proliferative index was relatively low in these tumors and slightly increased from groups A to B tumors (11% to 16%). Both beta-catenin and E-cadherin exhibited a normal membranous staining pattern in groups A and B tumors. The poorly differentiated adenocarcinomas ex GCC (group C) demonstrated abnormal p53 and beta-catenin immunoreactivity. The mean follow-up time was 49+/-5 (SE) months. The overall disease-specific survival for all subtypes was 77%, with 46% of patients without evidence of disease and 31% alive with disease. The mean survival was 43+/-7 months. All the patients with clinical stage of I or IIA disease had a favorable outcome after appropriate surgery with or without chemotherapy. Although most patients (63%) with GCC presented at an advanced clinical stage, their clinical outcome could be differentiated by subclassification of tumors. The stage IV-matched 5-year survival was 100%, 38%, and 0% for groups A, B, and C, respectively. In conclusion, GCC is a distinctive appendiceal neoplasm that exhibits unique pathologic features and clinical behavior. They display a spectrum of histologic features and possess the potential to transform to an adenocarcinoma phenotype of either signet ring cell or poorly differentiated adenocarcinoma types. Careful evaluation of the morphologic features of GCCs and appropriate pathologic classification are crucial for clinical management and prediction of outcome. Surgical management with right hemicolectomy is recommended after appendectomy for most cases, particularly those with an adenocarcinoma component (groups B and C).

Recent advances in the molecular diagnosis and prognosis of colorectal cancer

Colon cancer remains a leading cause of mortality worldwide despite the well-characterized molecular events in the adenoma-to-carcinoma sequence. There has been a strong emphasis on early detection of colon cancer, and fecal DNA-based methods have been developed to assist with early screening. Tissue-based assays have been utilized for many years to assess tumor aggressiveness and to determine prognosis and response to chemotherapeutic interventions. The most widely used serum marker for colon cancer (carcinoembryonic antigen) remains a useful modality to assess for occult disease following curative resection. Identification of tumor mutations in circulating tumor cells and microarray analysis holds a great deal of promise in the diagnosis and prognosis of patients with colorectal cancer. The inhibitors of apoptosis may be important markers to determine resistance to radiation cytotoxicity in rectal cancer. This report presents a summary of the current status of the molecular markers of colorectal cancer to establish a diagnosis, determine prognosis and chemoradiotherapeutic interventions, and assess relapse following curative surgery.

The forkhead box M1 transcription factor contributes to the development and growth of mouse colorectal cancer

BACKGROUND & AIMS

In this study, we used Forkhead Box m1b (Foxm1b) transgenic mice and conditional Foxm1 knock-out mice to examine the role of Foxm1 in colon cancer development and proliferation.

METHODS

To induce mouse colorectal cancer, we used a single intraperitoneal injection of azoxymethane (AOM) followed by three 1-week cycles of 2.5% dextran sodium sulfate (DSS) water, each cycle separated by 2 weeks. For these colon tumor studies, we used either Rosa26-Foxm1b transgenic mice that ubiquitously expressed the human Foxm1b complementary DNA or mice in which the Foxm1 fl/fl targeted allele was deleted in colonic epithelial cells using the gut-specific Villin-Cre recombinase transgene (Villin-Cre). Colorectal tumor number and bromodeoxyuridine labeling were determined in Rosa26-Foxm1b mice, Villin-Cre Foxm1-/-, mice and wild-type mice after 12 weeks of AOM/DDS exposure. We also used Foxm1 small interfering RNA-depleted human DLD1 and mouse CT26 colon cancer cell lines to examine DNA replication and anchorage-independent growth.

RESULTS

After 12 weeks of treatment with AOM/DSS, Rosa26 Foxm1b transgenic mice showed an increase in the number and size of colorectal tumors compared with wild-type mice. Likewise, a significant reduction in the development and growth of colorectal tumors was found in Villin-Cre Foxm1-/- mice compared with Foxm1 fl/fl mice after AOM/DSS treatment, which was associated with decreased expression of cyclin A2, cyclin B1, survivin, and T-cell factor 4 genes. Moreover, Foxm1-depleted colon cancer cell lines showed reduced DNA replication and anchorage-independent growth.

CONCLUSIONS

These studies suggest that Foxm1 is critical for the proliferation and growth of colorectal cancer.

Influence of methylated p15 and p16 genes on clinicopathological features in colorectal cancer

BACKGROUND AND AIM

Genetic silencing by promoter methylation has attracted attention in the carcinogenesis of colorectal cancer. Methylation of the p16(INK4a) gene has been found in primary colorectal cancer. Although the p15(INK4b) gene displays high homology to the p16(INK4a) gene in the amino acid sequence, methylation of p15(INK4b) has not been fully studied. We investigated p15(INK4b) methylation status in patients with colorectal cancer to verify the association between the methylation of p15(INK4b) and clinicopathological features compared with p16(INK4a).

METHODS

DNA samples from the tissues of primary colorectal cancer and corresponding adjacent normal colon mucosa were obtained from surgical resections of 88 patients (47 males and 41 females, aged 29-83 years). Methylation-specific polymerase chain reaction was used to analyze p15(INK4b) and p16(INK4a) methylation status after bisulfite modification. Cumulative survival rates (mean follow-up period: 53.2 months) were calculated by the Kaplan-Meier analysis. Methylations of p15(INK4b) and p16(INK4a) genes were detected in 23 (26.1%) and 20 (22.7%) colorectal cancers, respectively.

RESULTS

Methylation of p15(INK4b) was not associated with any clinicopathological features. Compared with normal mucosa, the methylation of p15(INK4b) was more prominent in tumor tissue (P < 0.001). Reverse transcription-polymerase chain reaction (RT-PCR) revealed that p15(INK4b) methylaton decreased mRNA expression. Kaplan-Meier analysis showed that patients with stage I-II had a significant difference in survival rate between those with and without methylated p15(INK4b) (P = 0.018).

CONCLUSIONS

Our results suggest that methylation of the p15(INK4b) gene contributes to the process of carcinogenesis in colorectal cancer as well as p16(INK4a) and is useful as a prognostic factor in the early stage.

Gene expression profiling of primary cultures of ovarian epithelial cells identifies novel molecular classifiers of ovarian cancer

In order to elucidate the biological variance between normal ovarian surface epithelial (NOSE) and epithelial ovarian cancer (EOC) cells, and to build a molecular classifier to discover new markers distinguishing these cells, we analysed gene expression patterns of 65 primary cultures of these tissues by oligonucleotide microarray. Unsupervised clustering highlights three subgroups of tumours: low malignant potential tumours, invasive solid tumours and tumour cells derived from ascites. We selected 18 genes with expression profiles that enable the distinction of NOSE from these three groups of EOC with 92% accuracy. Validation using an independent published data set derived from tissues or primary cultures confirmed a high accuracy (87–96%). The distinctive expression pattern of a subset of genes was validated by quantitative reverse transcription–PCR. An ovarian-specific tissue array representing tissues from NOSE and EOC samples of various subtypes and grades was used to further assess the protein expression patterns of two differentially expressed genes (Msln and BMP-2) by immunohistochemistry. This study highlights the relevance of using primary cultures of epithelial ovarian cells as a model system for gene profiling studies and demonstrates that the statistical analysis of gene expression profiling is a useful approach for selecting novel molecular tumour markers.

Helicobacter infection is required for inflammation and colon cancer in SMAD3-deficient mice

Accumulating evidence suggests that intestinal microbial organisms may play an important role in triggering and sustaining inflammation in individuals afflicted with inflammatory bowel disease (IBD). Moreover, individuals with IBD are at increased risk for developing colorectal cancer, suggesting that chronic inflammation may initiate genetic or epigenetic changes associated with cancer development. We tested the hypothesis that bacteria may contribute to the development of colon cancer by synergizing with defective transforming growth factor-beta (TGF-beta) signaling, a pathway commonly mutated in human colon cancer. Although others have reported that mice deficient in the TGF-beta signaling molecule SMAD3 develop colon cancer, we found that SMAD3-deficient mice maintained free of the Gram-negative enterohepatic bacteria Helicobacter spp. for up to 9 months do not develop colon cancer. Furthermore, infection of SMAD3(-/-) mice with Helicobacter triggers colon cancer in 50% to 66% of the animals. Using real-time PCR, we found that Helicobacter organisms concentrate in the cecum, the preferred site of tumor development. Mucinous adenocarcinomas develop 5 to 30 weeks after infection and are preceded by an early inflammatory phase, consisting of increased proliferation of epithelial cells; increased numbers of cyclooxygenase-2-positive cells, CD4(+) T cells, macrophages; and increased MHC class II expression. Colonic tissue revealed increased transcripts for the oncogene c-myc and the proinflammatory cytokines interleukin-1alpha (IL-1alpha), IL-1beta, IL-6, IFN-gamma, and tumor necrosis factor-alpha, some of which have been implicated in colon cancer. These results suggest that bacteria may be important in triggering colorectal cancer, notably in the context of gene mutations in the TGF-beta signaling pathway, one of the most commonly affected cellular pathways in colorectal cancer in humans.

The altered DNA methylation pattern and its implications in liver cancer

DNA methylation is the most intensively studied epigenetic phenomenon, disturbances of which result in changes in gene transcription, thus exerting drastic imparts onto biological behaviors of cancer. Both the global demethylation and the local hypermethylation have been widely reported in all types of tumors, providing both challenges and opportunities for a better understanding and eventually controlling of the malignance. However, we are still in the very early stage of information accumulation concerning the tumor associated changes in DNA methylation pattern. A number of excellent recent reviews have covered this issue in depth. Therefore, this review will summarize our recent data on DNA methylation profiling in cancers. Perspectives for the future direction in this dynamic and exciting field will also be given.

A novel protein-DNA interaction involved with the CpG dinucleotide at -30 upstream is linked to the DNA methylation mediated transcription silencing of the MAGE-A1 gene

To understand the DNA-methylation mediated gene silencing mechanisms, we analyzed in cell culture of the promoter function of the MAGE-A1 gene, which is frequently demethylated and over-expressed in human hepatocellular carcinoma. We have established the correlation of the DNA methylation of the promoter CpG island with expression status of this gene in a panel of the established liver cancer cell lines. The crucial CpG dinucleotide(s) within the minimal promoter subjected to the control mediated by DNA methylation with profound biological functions was also delineated. Furthermore, a novel sequence-specific DNA-protein interaction at the -30 CpG dinucleotide upstream of the gene was found having a vital part to play in the DNA methylation mediated transcription silencing of the MAGE-A1 gene. Our results would not only provide new insights into the DNA methylation mediated mechanisms over transcription of the MAGE-A1 gene, but also pave the way for further defining the cross-talk among DNA methylation, histone modification and chromatin remodeling in detail.

Methylation profile of the promoter CpG islands of 31 genes that may contribute to colorectal carcinogenesis

AIM: To establish the methylation profile of the promoter CpG islands of 31 genes that might play etiological roles in colon carcinogenesis.

METHODS: The methylation specific PCR in conjunction of sequencing verification was used to establish the methylation-profile of the promoter CpG islands of 31 genes in colorectal cancer (n = 65), the neighboring non-cancerous tissues (n = 5), colorectal adenoma (n = 8), and normal mucosa (n = 1). Immunohistochemically, expression of 10 genes was assessed on the home-made tissue microarrays of tissues from 58 patients. The correlation of tumor specific changes with each of clinical-pathologic features was scrutinized with relevant statistic tools.

RESULTS: In comparison with the normal mucosa of the non-cancer patients, the following 14 genes displayed no tumor associated changes: breast cancer 1, early onset (BRCA1), cadherin 1, type 1, E-cadherin (epithelial) (CDH1), death-associated protein kinase 1 (DAPK1), DNA (cytosine-5-)-methyltransferase 1 (DNMT1), melanoma antigen, family A, 1 (directs expression of antigen MZ2-E) (MAGEA1), tumor suppressor candidate 3 (N33), cyclin-dependent kinase inhibitor 1A (p21, Cip1) (p21^WAF1), cyclin-dependent kinase inhibitor 1B (p27, Kip1) (p27^KIP1), phosphatase and tensin homolog (mutated in multiple advanced cancers 1) (PTEN), retinoic acid receptor, beta (RAR- , Ras association (RalGDS/AF-6) domain family 1 C (RASSF1C), secreted frizzled-related protein 1 (SFRP1), tissue inhibitor of metalloproteinase 3 (Sorsby fundus dystrophy, pseudoinflammatory) (TIMP3), and von Hippel-Lindau syndrome (VHL). The rest 17 targets exhibited to various extents the tumor associated changes. As changes in methylation of the following genes occurred marginally, their impact on the formation of colorectal cancer were trivial: adenomatous polyposis coli (APC) (8%, 5/65), Ras association (RalGDS/AF-6) domain family 1A (RASSF1A) (3%, 2/65) and cyclin-dependent kinase inhibitor 2A, alternated reading frame (p14^ARF) (6%, 4/65). The following genes exhibited moderate changes in methylation: O-6-methylguanine-DNA methyltransferase (MGMT) (20%, 13/65), mutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli) (hMLH1) (18%, 12/65), cyclin-dependent kinase inhibitor 2A (melanoma, p16, inhibits CDK4) (p16^INK4a ) (10%, 10/65), methylated in tumor 1 (MINT1) (15%, 10/65), methylated in tumor 31 (MINT31) (11%, 7/65). The rest changed greatly in the methylation pattern in colorectal cancer (CRC): cyclin A1 (cyclin a1) (100%, 65/65), caudal type homeobox transcription factor 1 (CDX1) (100%, 65/65), RAR-(85%, 55/65), myogenic factor 3 (MYOD1) (69%, 45/65), cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4) (p15^INK4b) (68%, 44/65), prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) (COX2) (72%, 47/65), cadherin 13, H-cadherin (heart) (CDH13) (65%, 42/65), CAAX box 1 (CXX1) (58%, 38/65), tumor protein p73 (p73) (63%, 41/65) and Wilms tumor 1 (WT1) (58%, 38/65). However, no significant correlation of changes in methylation with any given clinical-pathological features was detected. Furthermore, the frequent changes in methylation appeared to be an early phase event of colon carcinogenesis. The in situ expression of 10 genes was assessed by the immunohistochemical approach at the protein level: CDH1, CDH13, COX2, cyclin A1, hMLH1, MGMT, p14^ARF, p73, RAR- , and TIMP3 genes in the context of the methylation status in colorectal cancer. No clear correlation between the hypermethylation of the promoter CpG islands and the negative expression of the genes was established.

CONCLUSION: The methylation profile of 31 genes was established in patients with colon cancer and colorectal adenomas, which provides new insights into the DNA methylation mediated mechanisms underlying the carcinogenesis of colorectal cancer and may be of prognostic values for colorectal cancer.

Methylation profiles of thirty four promoter-CpG islands and concordant methylation behaviours of sixteen genes that may contribute to carcinogenesis of astrocytoma

Background

Astrocytoma is a common aggressive intracranial tumor and presents a formidable challenge in the clinic. Association of altered DNA methylation patterns of the promoter CpG islands with the expression profile of cancer-related genes, has been found in many human tumors. Therefore, DNA methylation status as such may serve as an epigenetic biomarker for both diagnosis and prognosis of human tumors, including astrocytoma.

Methods

We used the methylation specific PCR in conjunction with sequencing verification to establish the methylation profile of the promoter CpG island of thirty four genes in astrocytoma tissues from fifty three patients (The WHO grading:. I: 14, II: 15, III: 12 and IV: 12 cases, respectively). In addition, compatible tissues (normal tissues distant from lesion) from three non-astrocytoma patients were included as the control.

Results

Seventeen genes (ABL, APC, APAF1, BRCA1, CSPG2, DAPK1, hMLH1, LKB1, PTEN, p14^ARF, p15^INK4b, p27^KIP1, p57^KIP2, RASSF1C, RB1, SURVIVIN, and VHL) displayed a uniformly unmethylated pattern in all the astrocytoma and non-astrocytoma tissues examined. However, the MAGEA1 gene that was inactivated and hypermethylated in non-astrocytoma tissues, was partially demethylated in 24.5% of the astrocytoma tissues (co-existence of the hypermethylated and demethylated alleles). Of the astrocytoma associated hypermethylated genes, the methylation pattern of the CDH13, cyclin a1, DBCCR1, EPO, MYOD1, and p16^INK4a genes changed in no more than 5.66% (3/53) of astrocytoma tissues compared to non-astrocytoma controls, while the RASSF1A, p73, AR, MGMT, CDH1, OCT6,, MT1A, WT1, and IRF7 genes were more frequently hypermethylated in 69.8%, 47.2%, 41.5%, 35.8%, 32%, 30.2%, 30.2%, 30.2% and 26.4% of astrocytoma tissues, respectively. Demethylation mediated inducible expression of the CDH13, MAGEA1, MGMT, p73 and RASSF1A genes was established in an astrocytoma cell line (U251), demonstrating that expression of these genes is likely regulated by DNA methylation. AR gene hypermethylation was found exclusively in female patients (22/27, 81%, 0/26, 0%, P < 0.001), while the IRF7 gene hypermethylation preferentially occurred in the male counterparts (11/26, 42.3% to 3/27, 11%, P < 0.05). Applying the mathematic method "the Discovery of Association Rules", we have identified groups consisting of up to three genes that more likely display the altered methylation patterns in concert in astrocytoma.

Conclusions

Of the thirty four genes examined, sixteen genes exhibited astrocytoma associated changes in the methylation profile. In addition to the possible pathological significance, the established concordant methylation profiles of the subsets consisting of two to three target genes may provide useful clues to the development of the useful prognostic as well as diagnostic assays for astrocytoma.

The role of flat and depressed colorectal lesions in colorectal carcinogenesis: new insights from clinicopathological findings in high-magnification chromoscopic colonoscopy

High-magnification chromoscopic endoscopy is a new technique which has been recently introduced to the UK. This technology, initially pioneered by the Japanese in the 1980s, has changed our understanding of the pathogenesis of colorectal cancer and our subsequent therapeutic strategies aimed at the secondary prevention of cancer. Magnification colonoscopic techniques when combined with colonic chromoscopy (dye spraying of the colon) permit in vivo assessments of lesions at a magnification and resolution similar to a stereomicroscope. Furthermore, flat/depressed adenomas and cancers can be diagnosed with increasing frequency and new resection practices performed. This technique is known as endoscopic mucosal resection. As gastrointestinal endoscopists adopt these new techniques, close liaison with histopathologists is essential to provide the highest standards of diagnostic accuracy. The histopathologist also needs to be aware of the endoscopic findings when interpreting specimens and hence must understand new endoscopic terminologies and classification systems that accompany the introduction of new technologies and therapeutic techniques. This article describes the controversies relating to the flat and depressed colorectal lesion, where these new endoscopic technologies are ideally suited. It then provides a working description of high-magnification chromoscopic colonoscopy including the Japanese 'pit pattern' and morphological classification system-information which will be provided to histopathologists with specimens obtained by these new techniques. Finally, we describe the procedure of endoscopic mucosal resection, as the type and quality of specimens received for histopathological analysis will be highly influenced by these techniques.

Clusterin as a biomarker in murine and human intestinal neoplasia

Early detection of colorectal cancer is critical for the management of this disease. Biomarkers for early detection of several cancers have been developed and applied clinically in recent years. We have sought to discover candidate biomarkers without the restricted choice of markers placed on microarrays, and without the biological complications of genetic and environmental heterogeneity. We have compared by cDNA subtraction two genetically matched sets of mice, one developing multiple intestinal neoplasia (C57BL/6J-ApcMin) and the other tumor-free (C57BL/6J). One prominent candidate biomarker, clusterin, was then subjected to a series of validation steps. In situ hybridization and immunohistochemistry were used to analyze clusterin expression at a cellular level on a series of murine intestinal and human colonic neoplasms. Elevated clusterin expression was characterized within certain regions of murine and human tumors regardless of tumor stage, location, or mode of initiation. The cells showing high clusterin levels generally lacked differentiation markers and adenomatous polyposis coli antigen. Tumor cells undergoing apoptosis expressed low levels of clusterin. Its specific expression patterns and correlation with cellular events during tumorigenesis make it a useful diagnostic tool in the mouse and a potential contributor to the set of biomarkers for early detection of human colon cancer.