Serrated tubulovillous adenoma of the large intestine.

AIMS: Most colorectal polyps are classified readily, but a subset of tubulovillous adenomas (TVA) with prominent serrated architecture causes diagnostic confusion. We aimed to (i) identify histological features that separate serrated TVAs from both conventional TVAs and traditional serrated adenomas (TSA) and (ii) perform a clinicopathological and molecular analysis to determine if the serrated TVA has unique features. METHODS AND RESULTS: We collected 48 serrated TVAs, 50 conventional TVAs and 66 BRAF wild-type TSAs for analysis. For each polyp we performed a clinicopathological assessment, BRAF and KRAS mutation profiling, cytosine-phosphate-guanosine (CpG) island methylator phenotype status, MGMT methylation and immunohistochemical assessment of seven markers [MutL homologue 1 (MLH1), p16, p53, ß-catenin, Ki67, CK7 and CK20]. We found that serrated TVAs can be diagnosed reliably, and have features distinct from both conventional TVAs and TSAs. Compared to conventional TVAs, serrated TVAs are larger, more often proximal, more histologically advanced, show more CpG island methylation and more frequent KRAS mutation. Compared to TSAs they are more often proximal, show less CpG island methylation, more frequent MGMT methylation and more frequent nuclear staining for ß-catenin. CONCLUSIONS: The serrated TVA can be diagnosed reliably and has unique features. It represents a precursor of KRAS mutated, microsatellite stable colorectal carcinoma.

Are all RAS mutations the same? Coexisting KRAS and NRAS mutations in a caecal adenocarcinoma and contiguous tubulovillous adenoma.

Mutations of the human Kirsten rat sarcoma viral oncogene homologue (KRAS) and the highly homologous human neuroblastoma RAS viral oncogene homologue (NRAS) are associated with resistance to antiepidermal growth factor receptor therapies in patients with colorectal cancer. In this report, we describe a caecal adenocarcinoma that contains both KRAS c.35G>T (G12V) and NRAS c.34G>A (G12S) mutations. The adenocarcinoma arises from a contiguous high-grade tubulovillous adenoma, which also carries the identical KRAS and NRAS mutations, supporting their common origin. While KRAS mutations are common in colorectal cancers, NRAS mutations are relatively rare and the coexistence of multiple RAS mutations is not documented, presumably reflecting similar functions of wild-type and mutant forms of RAS. Recent experimental evidence has suggested that KRAS and NRAS may in fact mediate distinct biological processes in the colon, and this unusual case potentially illustrates the hypothesis clinically. Characterisation of the diverse and divergent functions of RAS family members and mutant forms of RAS in the colon form important considerations for the development of RAS-targeting therapeutics.

Frequent lack of GNAS mutations in colorectal adenocarcinoma associated with GNAS-mutated villous adenoma.

Colorectal villous adenoma is thought to be associated with a high risk of progression to adenocarcinoma. To better characterize the genetic alterations involved in colorectal carcinogenesis related to villous adenoma, we analyzed mutations in APC, BRAF, KRAS, TP53, and GNAS in 12 colorectal adenocarcinomas associated with villous adenomas. APC, KRAS, and BRAF mutations were identified in five, 11, and one lesion, respectively, and most of these mutations were shared between the villous adenoma and the adenocarcinoma components in the respective lesions, except in one lesion with APC mutations and in two lesions with KRAS mutations. TP53 mutations were observed exclusively in four adenocarcinoma components, consistent with their role in the progression from adenoma to adenocarcinoma. Activating GNAS mutations were found in nine villous adenomas; however, unexpectedly, these mutations were shared only in three associated adenocarcinomas. Notably, all six adenocarcinomas with discordant GNAS mutation statuses were nonmucinous type, whereas all the other adenocarcinomas, including three adenocarcinomas associated with GNAS wild-type villous adenomas, were mucinous type. The current study suggests that GNAS-mutated villous adenomas may not necessarily be direct precursors of associated adenocarcinomas. At the same time, our observations support the role of activating GNAS mutations in increased mucin production in colorectal neoplasms.

Frequent activating GNAS mutations in villous adenoma of the colorectum.

To elucidate the role of GNAS mutations in colorectal tumourigenesis, we performed a mutation analysis in a total of 234 colorectal tumours, including adenomas, serrated lesions and adenocarcinomas. Activating GNAS mutations were found in 20 of the 24 villous adenomas (83%) but were absent in all the other tumours, except for one tubulovillous adenoma (3%) and two adenocarcinomas (3%). KRAS and BRAF mutations were always mutually exclusive. KRAS mutations were frequent in villous (67%) and tubulovillous (60%) adenomas but were rare or absent in tubular adenomas (6%) and serrated lesions, including hyperplastic polyps, sessile serrated polyps/sessile serrated lesions and traditional serrated adenomas (0-9%). BRAF mutations were found in four villous adenomas (17%) and in the large majority of serrated lesions (81-92%), but were absent in tubular and tubulovillous adenomas. Seventeen villous adenomas (71%) harboured GNAS mutations concomitantly with KRAS or BRAF mutations. Immunohistochemically, all the villous adenomas retained mismatch repair protein expression, suggesting that they are microsatellite-stable. The current study showed that the presence of activating GNAS mutations, in association with KRAS or BRAF mutations, is a characteristic genetic feature of colorectal villous adenoma.

Ki-ras gene mutations are invariably present in low-grade mucinous tumors of the vermiform appendix.

OBJECTIVE: Low-grade mucinous tumors of the appendix appear to have a simple histological structure. Paradoxically, reports have suggested a greater frequency of Ki-ras gene mutation in these lesions than in more complex lesions such as benign colonic adenomas and carcinomas. We assessed several molecular genetic changes, including Ki-ras gene mutations, in a large series of low-grade mucinous tumors of the appendix. MATERIAL AND METHODS: We retrospectively ascertained low-grade mucinous tumors of the appendix from computerized pathology records. Extracted DNA was analyzed for APC and DCC gene loss of heterozygosity, microsatellite instability and for the presence of Ki-ras gene mutation using standard molecular techniques. Controls consisted of normal appendices, other appendiceal neoplasms, and ovarian mucinous cystadenomas. RESULTS: A total of 31 low-grade appendiceal mucinous tumors were identified. All were microsatellite stable and none demonstrated loss of heterozygosity for the APC or DCC genes. By contrast, all 31 lesions contained a Ki-ras gene mutation. CONCLUSIONS: The presence of a Ki-ras gene mutation in all lesions, with no other molecular changes identified, strongly suggests a possible etiological role of the Ki-ras mutation in the development of this particular lesion of the appendix. Based on other work regarding intestinal bacteria, we hypothesize a relationship between chronic inflammation of the appendix from bacterial overgrowth and Ki-ras gene mutation.

Tubular adenomas with minor villous changes show molecular features characteristic of tubulovillous adenomas.

Advanced colorectal polyps are identified based on size ≥10 mm, high-grade dysplasia, and/or villous histology. A diagnosis of tubular adenoma (TA) is recommended if villous change occupies <20% of the lesion, or tubulovillous adenoma (TVA) is recommended if there is 20% to 80% villosity. We hypothesized that even subtle villous changes (1% to 20%) would correlate with advanced molecular features. Two hundred sixty-nine colorectal adenomas were examined for KRAS and BRAF mutation and immunohistochemical staining of ß-catenin, O6-Methyl Guanine DNA Methyltransferase (MGMT), and p53. Adenomas were classified as TA1 (0% villosity, n=70), TA2 (1% to 20% villosity, n=81), or TVA (21% to 80% villosity, n=118). Clinical and molecular features were analyzed by univariate χ² and multivariate logistic regression. There was an incremental increase in KRAS mutation frequency with increasing villous compartment (17.9% TA1, 59.0% TA2, 78.4% TVA; P<0.001). MGMT was more frequently lost in TA2 (37.0%) than in TA1 (8.6%) (P<0.001) but did not differ from TVA (39.8%). p53 overexpression was more common in TA2 (38.3%) than in TA1 (10.0%) (P<0.001) but did not differ from TVA (32.2%). On multivariate analysis, TA2 adenomas were more likely to have a KRAS mutation [odds ratio (OR) 6.6, 95% confidence interval (CI), 3.0-14.2], MGMT loss (OR 6.2, 95% CI, 2.4-16.0), or p53 overexpression (OR 5.6, 95% CI, 2.3-13.7) than TA1. We have identified a subgroup of TAs based on subtle villous changes. These adenomas are more likely to show molecular features that are characteristic of TVAs than TAs. These data support the concept that any villous change may indicate increased malignant potential and may be useful to consider when assigning surveillance guidelines.

Differentiation of tubular and villous adenomas based on Wnt pathway-related gene expression profiles.

This study was undertaken to define whether differences in the expression of Wnt pathway components are present between normal colonic mucosa, early (tubular) adenomas and villous adenomas which have a higher malignant potential. Normal mucosa, tubular adenomas and villous adenomas were obtained from twelve patients. RNA was isolated and utilized for Wnt pathway-specific membrane array expression analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) and fluorescent immunohistochemistry (IHC) were utilized for confirmatory analyses. Fifteen Wnt pathway-related genes showed differential expression between villous adenomas and normal mucosa and villous and tubular adenomas at a significance level of p<0.01. Genes involved in canonical Wnt (beta-catenin) signaling with increased expression in villous adenomas included wnt1, fz2, csnk2A2, pygo2, pygo1, frat2 and myc, the latter confirmed by qRT-PCR and IHC. Myc protein expression was confined primarily to stromal components of villous adenomas. Genes involved in non-canonical Wnt signaling with increased expression in villous adenomas included rho-u, daam1, damm2, cxxc4 and nlk. Successive increases in the expression of ctnnb1 (beta-catenin) from normal to tubular adenomas to villous adenomas was seen. The Wnt pathway gene expression profile can differentiate between tubular and villous adenomas. These data suggest that Wnt signaling regulation changes during the progression from normal mucosa to tubular adenomas to villous adenomas. Expression of Myc in adenoma stroma suggests a dynamic signaling network within adenomas between mucosal and stromal elements. Inhibition of the Wnt pathway may provide a novel approach for cancer prevention in patients with benign tubular adenomas.

[A study on microsatellite instability status for colorectal serrated lesions].

OBJECTIVE: To verify the traditional serrated pathway by comparing microsatellite instability (MSI) status among traditional serrated adenoma, traditional adenoma, serrated colorectal cancer and non-serrated colorectal cancer. METHODS: Seventy-five paraffin-embedded tissue samples, including 15 with serrated adenocarcinoma (Sca), 20 with non-serrated adenocarcinoma (N-Sca), 20 with traditional serrated adenoma (TSA) and 20 with villous adenoma (AD) were collected from the pathology department of our hospital. Genomic DNA was extracted from these samples and then amplified with fluorescently-labeled primer specific for BAT25 and BAT26. The MSI status was detected with DNA automatic sequencer. RESULTS: Six of 18 samples with TSA harbored MSI-H and twelve MSI-L/MSS; 18 samples with conventional adenoma were exclusively of MSS; 3 of 13 samples of serrated carcinoma harbored MSI-H and ten MSI-L/MSS; 18 of 19 N-Sca samples harbored MSI-L/MSS and only one MSI-H. With Chi-square test, the MSI frequency in AD group and N-Sca group was significantly lower than that in TSA group and Sca group (P<0.05); but with no statistical difference between the TSA group and Sca groups (P>0.05). CONCLUSION: MSI-H frequency in AD group and N-Sca group was obviously lower than that of TSA group and Sca group. It is concluded that there might be a new traditional serrated neoplasia pathway which is different from the conventional adenoma-carcinoma carcinogenesis pathway, but we still need prospective follow-up studies to verify its existence.

Deletion hotspots in AMACR promoter CpG island are cis-regulatory elements controlling the gene expression in the colon.

Alpha-methylacyl-coenzyme A racemase (AMACR) regulates peroxisomal beta-oxidation of phytol-derived, branched-chain fatty acids from red meat and dairy products -- suspected risk factors for colon carcinoma (CCa). AMACR was first found overexpressed in prostate cancer but not in benign glands and is now an established diagnostic marker for prostate cancer. Aberrant expression of AMACR was recently reported in Cca; however, little is known about how this gene is abnormally activated in cancer. By using a panel of immunostained-laser-capture-microdissected clinical samples comprising the entire colon adenoma-carcinoma sequence, we show that deregulation of AMACR during colon carcinogenesis involves two nonrandom events, resulting in the mutually exclusive existence of double-deletion at CG3 and CG10 and deletion of CG12-16 in a newly identified CpG island within the core promoter of AMACR. The double-deletion at CG3 and CG10 was found to be a somatic lesion. It existed in histologically normal colonic glands and tubular adenomas with low AMACR expression and was absent in villous adenomas and all CCas expressing variable levels of AMACR. In contrast, deletion of CG12-16 was shown to be a constitutional allele with a frequency of 43% in a general population. Its prevalence reached 89% in moderately differentiated CCas strongly expressing AMACR but only existed at 14% in poorly differentiated CCas expressing little or no AMACR. The DNA sequences housing these deletions were found to be putative cis-regulatory elements for Sp1 at CG3 and CG10, and ZNF202 at CG12-16. Chromatin immunoprecipitation, siRNA knockdown, gel shift assay, ectopic expression, and promoter analyses supported the regulation by Sp1 and ZNF202 of AMACR gene expression in an opposite manner. Our findings identified key in vivo events and novel transcription factors responsible for AMACR regulation in CCas and suggested these AMACR deletions may have diagnostic/prognostic value for colon carcinogenesis.

Tumor marker utility and prognostic relevance of cathepsin B, cathepsin L, urokinase-type plasminogen activator, plasminogen activator inhibitor type-1, CEA and CA 19-9 in colorectal cancer.

BACKGROUND: Cathepsin B and L (CATB, CATL), urokinase-type plasminogen activator (uPA) and its inhibitor PAI-1 play an important role in colorectal cancer invasion. The tumor marker utility and prognostic relevance of these proteases have not been evaluated in the same experimental setting and compared with that of CEA and CA-19-9. METHODS: Protease, CEA and CA 19-9 serum or plasma levels were determined in 56 patients with colorectal cancer, 25 patients with ulcerative colitis, 26 patients with colorectal adenomas and 35 tumor-free control patients. Protease, CEA, CA 19-9 levels have been determined by ELISA and electrochemiluminescence immunoassay, respectively; their sensitivity, specificity, diagnostic accuracy have been calculated and correlated with clinicopathological staging. RESULTS: The protease antigen levels were significantly higher in colorectal cancer compared with other groups. Sensitivity of PAI-1 (94%), CATB (82%), uPA (69%), CATL (41%) were higher than those of CEA or CA 19-9 (30% and 18%, respectively). PAI-1, CATB and uPA demonstrated a better accuracy than CEA or CA 19-9. A combination of PAI-1 with CATB or uPA exhibited the highest sensitivity value (98%). High CATB, PAI-1, CEA and CA 19-9 levels correlated with advanced Dukes stages. CATB (P = 0.0004), CATL (P = 0.02), PAI-1 (P = 0.01) and CA 19-9 (P = 0.004) had a significant prognostic impact. PAI-1 (P = 0.001), CATB (P = 0.04) and CA 19-9 (P = 0.02) proved as independent prognostic variables. CONCLUSION: At the time of clinical detection proteases are more sensitive indicators for colorectal cancer than the commonly used tumor markers. Determinations of CATB, CATL and PAI-1 have a major prognostic impact in patients with colorectal cancer.

CpG island methylation is frequently present in tubulovillous and villous adenomas and correlates with size, site, and villous component.

CpG island methylator phenotype (CIMP) pathway in colorectal cancer is characterized by methylation of promoter regions of multiple putative tumor suppressor genes. Aberrant methylation also occurs in serrated and adenomatous polyps. We examined 32 tubulovillous/villous adenomas and 30 tubular adenomas for BRAF/KRAS mutations and methylation at hMLH1, p16, HIC1, RASSF2, MGMT, MINT1, and MINT31. CIMP-positive status (methylation at 3 or more loci) was observed in 44% tubulovillous/villous adenomas compared with 8 (27%) of 30 tubular adenomas (P = .08). Tubulovillous/villous adenomas showed significantly higher methylation than tubular adenomas at MGMT (87% vs 37%, P < .01) and RASSF2 (94% vs 70%, P = .02). There was no significant difference in methylation of HIC1, MINT1, MINT31, and p16. hMLH1 methylation was absent in all tubulovillous/villous adenomas and seen in only 2 (7%) tubular adenomas. CIMP-positive status correlated with large size, right-sided location, and amount of villous component in tubulovillous/villous adenomas. BRAF V600E mutation was not observed in any tubular adenoma or tubulovillous/villous adenoma. KRAS mutations were seen in 9% of tubulovillous/villous adenomas and 10% of tubular adenomas. In conclusion, CIMP-positive phenotype is common in tubulovillous/villous adenomas and increases with large size, right-sided location, and amount of villous component. Methylation of MGMT and RASSF2 increases during the progression from tubular adenoma to tubulovillous/villous adenoma. BRAF mutations are absent in tubulovillous/villous adenomas.

Allelic losses at genomic instability-associated loci in villous adenomas and adjacent colorectal cancers.

Allelic imbalances in premalignant villous adenomas were compared with those in adjacent microdissected colorectal carcinoma that had arisen directly from the adenomas. Carcinoma-adenoma pairs were examined from 17 patients who underwent resections for colorectal cancer. In all, 28 microsatellite markers were examined, from regions of the genome where individual allelic losses have been associated with overall genomic instability in colorectal carcinomas. Microsatellite instability (MSI) was also evaluated for each marker in each tissue type. Loss of heterozygosity for multiple markers was found in 35% of adenomas and 65% of carcinomas; the average fractional allelic loss rate was 2.5 times higher in carcinomas than in adenomas. Of the 17 patients, 4 had MSI for >30% of markers in both adenoma and carcinoma, with no significant differences between the two tissues. Markers with particularly high imbalance rates in adenomas were seen on chromosomes 11, 14, and 15. These findings provide further evidence that genomic instability is an ongoing process during carcinogenesis, with a markedly increased frequency of allelic losses seen in carcinomas, compared with adjacent adenomas. Markers on chromosomes 11, 14, and 15 may become valuable tools in the identification of patients destined to progress to colorectal carcinomas.

Associations of Ki-ras proto-oncogene mutation and p53 gene overexpression in sporadic colorectal adenomas with demographic and clinicopathologic characteristics.

In colorectal tumorigenesis, Ki-ras proto-oncogene mutation often occurs early in the adenoma-adenocarcinoma sequence, whereas mutation of the p53 gene is associated with late progression to carcinoma. We evaluated the relationship of demographic and clinicopathologic characteristics to Ki-ras mutation and p53 gene product overexpression in 1,093 baseline sporadic colorectal adenomas from 926 individuals enrolled in a phase III recurrence prevention trial. Ki-ras mutation was found in 14.7% of individuals and p53 overexpression was found in 7.0% of those tested. Multivariate analysis found older age, rectal location, and villous histology to be independently associated with Ki-ras mutation. Individuals with an advanced adenoma (>or=1 cm or high-grade dysplasia or villous histology) had a 4-fold higher likelihood of Ki-ras mutation [odds ratios (OR), 3.96; 95% confidence intervals (CI), 2.54-6.18]. Ki-ras mutations in codon 12 and of the G-to-A transition type were more frequent in older individuals, whereas G-to-T transversion was more frequent in rectal adenomas than in the colon. Multivariate analysis showed that previous history of a polyp (P = 0.03) was inversely associated with p53 overexpression. Large adenoma size (>or=1 cm), high-grade dysplasia, and villous histology were independently associated with p53 overexpression, with the strongest association for advanced adenomas (OR, 7.20; 95% CI, 3.01-17.22). Individuals with a Ki-ras mutated adenoma were more likely to overexpress p53 (OR, 2.46; 95% CI, 1.36-4.46), and 94.8% of adenomas with both alterations were classified as advanced (P

Expression and localisation of kinin receptors in colorectal polyps.

Kinins increase vascular permeability as well as mitogenesis and proliferation, hence they have a potential to promote neoplasmatic transformation. In the present study we investigated the expression profile and localization of kinin B1 and B2 receptors in colorectal polyps. The biopsy samples from various polyps were obtained during endoscopy in tubular (n=18), villous (n=15) and hyperplasic polyps (n=15). The expression of genes encoding B1 and B2 was estimated by QRT-PCR TaqMan analysis. In second series B1 and B2 receptors were visualized by immunohistochemical staining in tissue specimens from colonic polyps and adjacent normal tissue. We found the highest expression of gene encoding B1 in tubular adenomas (1891 number of copies mRNA/microg total RNA+/-312 SE) which is significantly higher as compared with controls (683+/-197 SE, p<0.013). In contrast, the expression of gene for B2 was significantly increased in hyperplastic polyps (3852+/-936 SE) as compared with controls (843+/-263 SE, p<0.0016). In normal colon a well as in hyperplasic polyps B1 and B2 receptors were immunohistochemically localized in enterocytes, however in hyperplastic polyps the intensity of staining was more prominent for B2 comparing to the control group. In contrast, in tubular adenomas staining reaction for B1 was more intense than in control samples. Increased level of B1 in adenoma suggests that kinins may play a role in abnormal cellular transformation; whereas higher B2 level in hyperplasic polyp suggests its protective role. Our data may indicate that the overall effect of kinins on cellular proliferation depends on the relative level of B1 and B2 receptor expression.

Low rate of microsatellite instability in young patients with adenomas: reassessing the Bethesda guidelines.

BACKGROUND AND AIM: Screening adenomas for microsatellite instability (MSI) in patients younger than 40 yr of age has been recommended by the Bethesda Guidelines as a means of identifying patients at risk for hereditary nonpolyposis colorectal cancer (HNPCC). We sought to determine the rate of MSI in adenomas removed from individuals under 40 yr of age over a 5-yr period in a university general gastroenterology practice. METHODS: We identified patients between 18 and 39 yr of age with endoscopically removed adenomatous colorectal polyps. Patients with polyposis syndromes, inflammatory bowel disease, or colorectal carcinoma were excluded. A three-generation family history was obtained via telephone interview. Endoscopic and histology reports were reviewed. Adenomas were tested for MSI using the BAT26 and BAT40 microsatellite markers, and expression of the MSH2 and MLH1 proteins was assessed by immunostaining. RESULTS: A total of 34 patients had 46 adenomas removed endoscopically. Out of 34 patients, 14 (41%) had a family history of colorectal cancer and 3 were from Amsterdam criteria positive families. A total of 28 of 46 adenomas (61%) were distal to the splenic flexure. Polyps ranged in size from 2 to 20 mm and averaged 6.6 mm. Five polyps (11%) were tubulovillous adenomas, and the remainder were tubular adenomas. None of the polyps were serrated adenomas and none demonstrated high-grade dysplasia. Among the 40 adenomas available for testing, none demonstrated MSI using either BAT26 (0/40) or BAT40 (0/21), nor did any of the polyps tested demonstrate loss of either MSH2 or MLH1 expression (0/16). CONCLUSION: Screening adenomas from patients younger than 40 yr of age for MSI was ineffective in identifying potentially new cases of HNPCC. New strategies that improve on the current clinical and molecular screening methods should be developed so that at-risk individuals can be identified and referred for germline testing before developing their first cancer.

Microsatellite analysis of sporadic flat and depressed lesions of the colon.

Prior studies of molecular and genetic derangements in flat and depressed lesions of the colon have revealed lower frequencies in a number of markers commonly present in exophytic lesions. These and other differences suggest that flat lesions are driven by alternative pathways. We reviewed a database of patients who had undergone endoscopic mucosal resection (EMR) for flat and depressed lesions at the University of Chicago from January 2001 to April 2003. Formalin-fixed and paraffin-embedded colonic samples were retrieved from the tissue bank, and five standardized mononucleotide and dinucleotide microsatellite regions were analyzed for instability (MSI) using fluorescently labeled forward primers in nonmultiplex reactions. Sixteen patients were identified with flat or depressed lesions who had adequate tissue specimens available for MSI analysis. Of these specimens, eight were tubular adenomas, three were tubulovillous adenomas, and five were carcinomas in situ. Four of the lesions were microsatellite unstable, each at a single locus, and one lesion showed probable instability at a second locus. Eleven lesions were microsatellite stable. Aberrations in DNA repair mechanisms do not appear to significantly contribute to the molecular derangements underlying sporadic flat or depressed colonic lesions. The molecular bases that underlie the aggressive behavior of sporadic flat and depressed lesions remain to be determined, and further investigation is warranted.

A case of colorectal carcinoma in adenoma analyzed by a cDNA array.

PATIENT AND METHODS: A 68-year-old woman presenting with bloody stools and anemia was referred to our hospital. Colonoscopy showed a Is-type tumor of 45 mm in diameter in the cecum and three Is-type tumors in the ascending colon. Ileocecal resection with regional lymph node dissection was performed. Microscopically, the large tumor consisted of a well-differentiated adenocarcinoma with a tubulovillous adenoma (TVA) component (carcinoma in adenoma). Some carcinoma (CA) cells had invaded the submucosal layer, but the lymph nodes were negative for malignancy. The other three polyps were diagnosed as TVAs. Because her family history fulfilled the Amsterdam criteria II for hereditary non-polyposis colorectal cancer (HNPCC), genetic analysis was performed. All of the four tumor tissues were classified as microsatellite stable (MSS) according to the National Cancer Institute guideline for analysis of microsatellite instability (MSI). K-ras mutation was detected in both CA and TVA lesions of the carcinoma in adenoma. To clarify relevant alterations of gene expression associated with adenoma-carcinoma progression, the gene expression profiles of these tumor tissues were analyzed by a cDNA array. RESULTS: Although the gene expression profiles were similar, insulin-like growth factor-II (IGF-II) was expressed most differentially in CA and TVA tissues. The results were further substantiated by comparison of the gene expression profiles of CA and TVA lesions of the carcinoma in adenoma. CONCLUSION: The results suggest that overexpression of IGF-II played an important role in the progression of adenoma to carcinoma in this patient.

The Immunohistochemical expression of endothelial cell differentiation gene-2 receptor in human colorectal adenomas.

BACKGROUND/AIMS: The EDG-2 (endothelial cell differentiation gene-2) has been characterized as one of the high-affinity receptors of lysophosphatidic acid: an extracellular lipid mediator which can induce tumor progression. Recent studies have revealed that EDG-2 plays an important role in various pathological events including cell proliferation and tumor development. The investigation of EDG-2 is thus considered important for eliciting the mechanism of tumorigenesis. However, in colorectal tissue, the clinical significance of EDG-2 expression remains unclear. In the current study, we examined the immunohistochemical expression of EDG-2 in colorectal mucosa and adenoma, and clarified its relation with the clinicopathological features. METHODOLOGY: One hundred and sixty-one colorectal polyps were resected endoscopically or surgically at our institute from 2000 to 2001. According to the degree of dysplasia, adenomas were grouped into two categories: low-grade (mild or moderate dysplasia) and high-grade (severe dysplasia or carcinoma in situ). We investigated EDG-2 expression by immunohistochemistry. RESULTS: EDG-2 was expressed almost exclusively in the cytoplasm in colorectal normal mucosa and adenoma. EDG-2 expression in normal mucosa and adenoma was 8% and 76%, respectively. EDG-2 expression was increased in low-grade adenoma compared with that in normal mucosa (P < 0.001). EDG-2 expression was significantly greater in adenomas with larger diameters (P < 0.001). CONCLUSIONS: We demonstrated that EDG-2 expression was increased in the early stage of adenoma. A significant correlation between EDG-2 expression and the size of the adenomas suggests that EDG-2 may play an important role in the growth of these adenomas.