Analysis of Ki-ras and p53 gene mutations in laterally spreading tumors of the colorectum

Comparison of the histopathological characteristics of large colorectal laterally spreading tumors according to growth pattern

OBJECTIVES

Colorectal laterally spreading tumors (LSTs) are widely recognized owing to their structural characteristics. This study aims to clarify the histopathological characteristics of large colorectal LSTs according to growth pattern.

METHODS

We studied 297 colorectal LSTs measuring ≥20 mm in diameter. The LSTs were classified into four types: granular homogenous type (LST-G-H), granular nodular mixed type (LST-G-M), non-granular flat elevated type (LST-NG-F), and non-granular pseudo-depressed type (LST-NG-PD). Retrospectively collected data were examined to compare the histopathological characteristics of LSTs according to the growth pattern.

RESULTS

LST-G-M lesions (142 lesions) were most common, followed by LST-NG-F (74 lesions), LST-G-H (61 lesions), and LST-NG-PD (20 lesions). The mean tumor diameter of LST-G lesions (38.5 ± 17.2 mm) was significantly greater than that of LST-NG lesions (26.3 ± 7.0 mm, P < 0.001). In particular, 45% of LST-G-M lesions were ≥40 mm in diameter. Adenomas accounted for 54% of LST-G-H lesions compared with only 10% of LST-NG-PD lesions. Pathological T1 carcinomas accounted for 55% of LST-NG-PD lesions and were not found among LST-G-H lesions.

CONCLUSIONS

The biological malignancy of colorectal LSTs differs considerably depending on the growth pattern even among large lesions and therefore should be considered when selecting treatment regimens.

Predictors of invasive cancer of large laterally spreading colorectal tumors: A multicenter study in Japan

Background and Aim

Although colorectal laterally spreading tumors (LSTs) can be classified into four subtypes, the histopathological characteristics are known to differ among these subtypes. We therefore performed a logistic regression analysis to determine whether the risk of pathological T1 cancer of large colorectal LSTs can be predicted based on factors such as endoscopic findings in a large group of patients enrolled in a multicenter study in Japan.

Methods

In the main study, we assessed 1236 colorectal adenomas or early cancers that were classified as LSTs measuring 20 mm or more in diameter and treated endoscopically. Logistic regression analysis was performed to determine whether factors such as the subtype of LST could be used to predict the risk of pathological T1 cancer. A validation study of 356 large colorectal LSTs was conducted to confirm the validity of the results obtained in the main study.

Results

The locations and tumor diameter of the LSTs in the main study were found to differ significantly according to the LST subclassification (P < 0.001). The frequency of pathological T1 cancers was the highest at 36% of LST nongranular pseudodepressed type, followed by 14% of LST nongranular flat‐elevated type, 11% of LST granular nodular mixed type, and 3% of LST granular homogenous type lesions. The risk of pathological T1 cancer was significantly associated with LST subclassification and tumor diameter. The area under the curve (AUC) was high (0.743). In the validation study, the AUC was 0.573.

Conclusions

In patients with large colorectal LSTs resected endoscopically, the risk of pathological T1 cancer can be predicted on the basis of the LST subclassification and tumor diameter.

Analysis of molecular alterations in laterally spreading tumors of the colorectum

BACKGROUND

Colorectal laterally spreading tumors (LSTs) are classified into LST-Gs and LST-NGs, according to macroscopic findings. In the present study, we determined the genetic and epigenetic alterations within colorectal LSTs and protruding adenomas.

METHODS

A crypt isolation method was used to isolate DNA from tumors and normal glands of 73 macroscopically verified colorectal LSTs (histologically defined adenomas; 38 LST-Gs and 35 LST-NGs) and 36 protruding adenomas. The DNA was processed using polymerase chain reaction (PCR) microsatellite assays, single-strand conformation polymorphism (SSCP) assays, and pyrosequencing to detect chromosomal allelic imbalance (AI), mutations in APC, KRAS, and TP53, and the methylation of MLH1, MGMT, CDKN2A, HPP1, RASSF2A, SFRP1, DKK1, ZFP64, and SALL4 genes. In addition, methylation status was examined using the following set of markers: MIN1, MINT2, MINT31, MLH1, and CDKN2A (with classification of negative/low and high). Microsatellite instability (MSI) was also examined.

RESULTS

5q AI and methylation of the SFRP1 and SALL4 genes were common molecular events in both LST-Gs and LST-NGs. Neither MSI nor mutations in BRAF ware observed in the LSTs. TP53 mutations were rarely found in LSTs. The frequencies of KRAS and APC mutations and the methylation levels of ZFP64, RASSF2A, and HPP1 genes were significantly higher in LST-Gs than in LST-NGs. Protruding adenomas showed alterations common to LST-Gs. Negative/low methylation status was common among the three types of tumors.

CONCLUSION

Combined genetic and epigenetic data suggested that the molecular mechanisms of tumorigenesis were different between LST-Gs and LST-NGs.

Epigenetic silencing of NTSR1 is associated with lateral and noninvasive growth of colorectal tumors

Our aim was to identify DNA methylation changes associated with the growth pattern and invasiveness of colorectal cancers (CRCs). Comparison of the methylation statuses of large (≥20 mm in diameter along the colonic surface) noninvasive tumors (NTs) and small (<20 mm in diameter along the colonic surface) invasive tumors (ITs) using CpG island microarray analysis showed neurotensin receptor 1 (NTSR1) to be hypermethylated in large NTs. Quantitative bisulfite pyrosequencing revealed that NTSR1 is frequently methylated in colorectal tumors, with large NTs exhibiting the highest methylation levels. The higher NTSR1 methylation levels were associated with better prognoses. By contrast, NTSR1 copy number gains were most frequent among small ITs. Methylation of NTSR1 was associated with the gene's silencing in CRC cell lines, whereas ectopic expression of NTSR1 promoted proliferation and invasion by CRC cells. Analysis of primary tumors composed of adenomatous and malignant portions revealed that NTSR1 is frequently methylated in the adenomatous portion, while methylation levels are generally lower in the cancerous portions. These results suggest that NTSR1 methylation is associated with lateral and noninvasive growth of colorectal tumors, while low levels of methylation may contribute to the malignant potential through activation of NTSR1. Our data also indicate that NTSR1 methylation may be a prognostic biomarker in CRC.

Tumoral Versus Flat Intraepithelial Neoplasia of Pancreatobiliary Tract, Gallbladder, and Ampulla of Vater

Context.—The identification of a precursor lesion is important to understanding the histopathologic and genetic alterations in carcinogenesis. There are a plethora of terminologies that describe precursor lesions of the pancreatobiliary tract, ampulla of Vater, and gallbladder. The current terminologies for precursor lesions may make it difficult to understand the tumor biology. Here, we propose the concept of tumoral and flat intraepithelial neoplasia to improve our understanding of precursor lesions of many epithelial organs, including the pancreatobiliary tract, ampulla of Vater, and gallbladder.

Objective.—To understand the dichotomous pattern of tumoral and flat intraepithelial neoplasia in carcinogenesis of pancreatobiliary tract, ampulla of Vater, and gallbladder.

Data Sources.—Review of relevant literatures indexed in PubMed.

Conclusions.—Tumoral intraepithelial neoplasia presents as an intraluminal or intraductal, mass-forming, polypoid lesion or a macroscopic, visible, cystic lesion without intracystic papillae. Microscopically, tumoral intraepithelial neoplasia shows various proportions of papillary and tubular architecture, often with a mixed pattern, such as papillary, tubular, and papillary-tubular. The malignant potential depends on the degree of dysplasia and the cell phenotype of the epithelium. Flat intraepithelial neoplasia presents as a flat or superficial, spreading, mucosal lesion that is frequently accompanied by an invasive carcinoma. Tumoral and flat intraepithelial neoplasias are not homogeneous entities and may exhibit histopathologic spectrum changes and different genetic profiles. Although intraepithelial neoplasia showed a dichotomous pattern in the tumoral versus flat types, they can coexist. Tumoral and flat intraepithelial neoplasia can be interpreted as part of a spectrum of changes in the carcinogenesis pathway of each organ.

Gene expression profiling of laterally spreading tumors

BACKGROUND

Laterally spreading tumors (LSTs) are generally defined as lesions >10 mm in diameter, are characterized by lateral expansion along the luminal wall with a low vertical axis. In contrast to other forms of tumor, LSTs are generally considered to have a superficial growth pattern and the potential for malignancy. We focused on this morphological character of LSTs, and analyzed the gene expression profile of LSTs.

METHODS

The expression of 168 genes in 41 colorectal tumor samples (17 LST-adenoma, 12 LST-carcinoma, 12 Ip [pedunculated type of the Paris classification)-adenoma, all of which were 10 mm or more in diameter] was analyzed by PCR array. Based on the results, we investigated the expression levels of genes up-regulated in LST-adenoma, compared to Ip-adenoma, by hierarchical and K-means clustering. To confirm the results of the array analysis, using an additional 60 samples (38 LST-adenoma, 22 Ip-adenoma), we determined the localization of the gene product by immunohistochemical staining.

RESULT

The expression of 129 genes differed in colorectal tumors from normal mucosa by PCR array analysis. As a result of K-means clustering, the expression levels of five genes, AKT1, BCL2L1, ERBB2, MTA2 and TNFRSF25, were found to be significantly up-regulated (p < 0.05) in LST-adenoma, compared to Ip-adenoma. Immunohistochemical analysis showed that the BCL2L1 protein was significantly and meaningfully up-regulated in LST-adenoma compared to Ip-adenoma (p = 0.010). With respect to apoptosis status in LST-Adenoma, it assumes that BCL2L1 is anti-apoptotic protein, the samples such as BCL2L1 positive and TUNEL negative, or BCL2L1 negative and TUNEL positive are consistent with the assumption. 63.2 % LST-adenoma samples were consistent with the assumption.

CONCLUSIONS

LSTs have an unusual profile of gene expression compared to other tumors and BCL2L1 might be concerned in the organization of LSTs.

Association of gankyrin and stemness factor expression in human colorectal cancer

BACKGROUND

It is widely accepted that the adenoma-carcinoma sequence represents the process by which most colorectal cancers (CRCs) arise. Although gankyrin is overexpressed in CRC tissues, its roles in the initiation step of colorectal carcinogenesis remain largely unexplored.

AIM

We investigated the expression of gankyrin and stemness factors in human colorectal adenomas, precancerous lesions, as well as CRC tissues to assess its involvement in colorectal carcinogenesis.

METHODS

Expression of several molecules including gankyrin and certain stemness factors was compared in 50 pairs of adenoma and surrounding normal mucosa using real-time quantitative polymerase chain reaction and in 30 CRC tissues using immunohistochemistry.

RESULTS

In CRC specimens, expression of CD133, a cancer stem cell marker, was significantly correlated with gankyrin expression. Gankyrin knockdown decreased the expression of vascular endothelial growth factor (VEGF) and stemness factors such as Nanog and Oct-4 in colorectal cancer cells. Expression of gankyrin and these stemness factors was significantly higher in adenomas than in the surrounding normal mucosa. Importantly, a significant correlation was observed between the expression of gankyrin, VEGF, and Nanog in colorectal adenomas.

CONCLUSION

In CRC development, gankyrin would control stem cell behavior by regulating the expression of stemness factors.

Tracking the molecular features of nonpolypoid colorectal neoplasms: a systematic review and meta-analysis

OBJECTIVES

Nonpolypoid colorectal neoplasms (NP-CRNs) are proposed as a major contributor to the occurrence of interval cancers, but their underlying biology remains controversial. We conducted a systematic review and meta-analysis to clarify the major biological events in NP-CRNs.

METHODS

We systematically searched for studies examining molecular characteristics of NP-CRNs. We performed random effect meta-analyses. We measured the heterogeneity among studies using I(2) and possible publication bias using funnel plots.

RESULTS

Fifty-three studies on KRAS, APC, or BRAF mutations, microsatellite instability (MSI), CpG island methylator phenotype (CIMP), or DNA promoter hypermethylation were included. We observed less KRAS mutations (summary odds ratio (OR) 0.30, confidence interval (CI)=0.19-0.46, I(2)=77.4%, CI=70.1-82.9) and APC mutations (summary OR 0.42, CI=0.24-0.72, I(2)=22.6%, CI=0.0-66.7) in NP-CRNs vs. protruded CRNs, whereas BRAF mutations were more frequent (summary OR 2.20, CI=1.01-4.81, I(2)=0%, CI=0-70.8), albeit all with large heterogeneity. Less KRAS mutations were especially found in NP-CRNs subtypes: depressed CRNs (summary OR 0.12, CI=0.05-0.29, I(2)=0%, CI=0-67.6), non-granular lateral spreading tumors (LSTs-NG) (summary OR 0.61, CI=0.37-1.0, I(2)=0%, CI=0-74.6), and early nonpolypoid carcinomas (summary OR 0.11, CI=0.06-0.19, I(2)=0%, CI=0-58.3). MSI frequency was similar in NP-CRNs and protruded CRNs (summary OR 0.99, CI=0.21-4.71, I(2)=70.3%, CI=38.4-85.7). Data for promoter hypermethylation and CIMP were inconsistent, precluding meaningful conclusions.

CONCLUSIONS

This meta-analysis provides indications that NP-CRNs are molecularly different from protruded CRNs. In particular, some subtypes of NP-CRNs, the depressed and LST-NG, are featured by less KRAS mutations than polypoid CRNs. Prospective, multicenter studies are needed to clarify the molecular pathways underlying nonpolypoid colorectal carcinogenesis and potential implications for surveillance intervals.

Overexpression of hTERT in potentially malignant colorectal laterally spreading tumors

Human telomerase reverse transcriptase (hTERT) is the main subunit of the core enzyme telomerase, which consists of three subunits. Telomeres are essential for chromosomal stability and integrity, protecting the ends of chromosomes from degradation and preventing chromosomal end fusions and recombination. A loss of telomere function is a major mechanism for the generation of chromosomal abnormalities. Telomere shortening leads to mutations, chromosome rearrangements and translocations. Colorectal laterally spreading tumors (LSTs) are a special type of superficial colorectal tumor. They are considered to have a high malignancy potential. The aim of the present study was to characterize the expression of hTERT in an LST cell line and paraffin sections. Immunohistochemistry was utilized to examine the protein expression of hTERT in the LST cell line, 48 resected LSTs, 48 protruded-type colorectal adenomas (PAs) and 48 normal mucosa samples. Statistical analyses were applied to test the associations between hTERT expression and clinicopathological parameters. The present study demonstrated that the positive expression levels of hTERT in LSTs, PAs and normal mucosa were 60.4, 22.9 and 10%, respectively. Compared with polypi and normal mucosa, the expression levels of hTERT were significantly increased in LSTs. The expression of hTERT was also observed in the LST cell line. The expression of hTERT was significantly higher in LSTs, which may indicate a potential for malignancy.

Colorectal lateral spreading tumor subtypes: clinicopathology and outcome of endoscopic submucosal dissection

PURPOSE

This study aims to investigate the clinicopathological features of specific subtypes of laterally spreading tumor (LST) and assessed the outcome of endoscopic submucosal dissection (ESD) based upon subdifferentiation status.

METHODS

A total of 137 LSTs were present in 135 patients; 96 were granular and 41 exhibited a nongranular pattern. Granular LSTs, subdivided into homogeneous and nodular mixed, and nongranular LSTs, subdivided into flat-elevated and pseudodepressed, were retrospectively evaluated with respect to clinicopathological features and results of ESD (en bloc R0 curative resection, procedure time, complication, and recurrence rate) according to specific subtype.

RESULTS

The distribution of high-grade intraepithelial neoplasia and submucosal carcinomas was more prominent among granular nodular mixed tumors than among granular homogeneous tumors (P = 0.007), whereas there was no significant difference between nongranular pseudodepressed tumors and flat-elevated tumors. The frequency of en bloc R0 curative resection did not differ significantly among specific subtypes. For nodular mixed and pseudodepressed lesions, the median tumor size was significantly larger (P < 0.001 for each) and mean procedure time was also longer (P < 0.05 for each) than for the other two subtypes. All complications, which included three perforations, five episodes of postoperative bleeding, and one recurrence, occurred in granular nodular mixed and nongranular pseudodepressed tumors.

CONCLUSION

The risk of cancer varies with the subtypes of LSTs. ESD is an effective treatment for LSTs, however ESD is more technically demanding and carries more complications in pseudodepressed and granular mixed subtypes.

MUC5AC/β-catenin expression and KRAS gene alteration in laterally spreading colorectal tumors

AIM: To clarify differences in mucin phenotype, proliferative activity and oncogenetic alteration among subtypes of colorectal laterally spreading tumor (LST).

METHODS: LSTs, defined as superficial elevated lesions greater than 10 mm in diameter with a low vertical axis, were macroscopically classified into two subtypes: (1) a granular type (Gr-LST) composed of superficially spreading aggregates of nodules forming a flat-based lesion with a granulonodular and uneven surface; and (2) a non-granular type (NGr-LST) with a flat smooth surface and an absence of granulonodular formation. A total of 69 LSTs, comprising 36 Gr-LSTs and 33 NGr-LSTs, were immunohistochemically stained with MUC2, MUC5AC, MUC6, CD10 (markers of gastrointestinal cell lineage), p53, β-catenin and Ki-67 antibodies, and examined for alteration in exon 1 of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and exon 15 of v-raf murine sarcoma viral oncogene homologue B1 (BRAF) by polymerase chain reaction followed by direct sequencing.

RESULTS: Histologically, 15 Gr-LST samples were adenomas with low-grade dysplasia (LGD), 12 were high-grade dysplasia (HGD) and 9 were adenocarcinomas invading the submucosa (INV), while 12 NGr-LSTs demonstrated LGD, 14 HGD and 7 INV. In the proximal colon, MUC5AC expression was significantly higher in the Gr-type than the NGr-type. MUC6 was expressed only in NGr-LST. MUC2 or CD10 did not differ. P53 expression demonstrated a significant stepwise increment in progression through LGD-HGD-INV with both types of LST. Nuclear β-catenin expression was significantly higher in the NGr-type. Ki-67 expression was significantly higher in the Gr-type in the lower one third zone of the tumor. In proximal, but not distal colon tumors, the incidence of KRAS provided mutation was significantly higher in the Gr-type harboring a specific mutational pattern (G12V). BRAF mutations (V600E) were detected only in two Gr-LSTs.

CONCLUSION: The two subtypes of LST, especially in the proximal colon, have differing phenotypes of gastrointestinal cell lineage, proliferation and activation of Wnt/β-catenin or RAS/RAF/extracellular signal-regulated kinase signaling.

Laterally spreading tumors in the colon and rectum

The large and relatively flat colorectal neoplastic lesions called laterally spreading tumors are classified as nonpolypoid despite some mixed patterns with protruding nodules. Large hyperplastic polyps and sessile serrated lesions are non-neoplastic lesions that also have this morphology and may potentially progress to neoplasia. All these large and relatively flat lesions are more frequent in the proximal colon and less conspicuous than polypoid lesions. Their underdiagnosis is a major factor in the failure of colonoscopy to prevent cancer in the proximal colon. The treatment of laterally spreading tumors by endoscopic resection (endoscopic mucosal resection, piecemeal endoscopic mucosal resection, endoscopic submucosal dissection), or by surgery is based on a careful morphologic analysis, taking into account the size and surface with nodules or depression. The technique of endoscopic submucosal dissection should be diffused because it reduces the number of surgical indications.

Comprehensive mutation analysis in colorectal flat adenomas

BACKGROUND

Flat adenomas are a subgroup of colorectal adenomas that have been associated with a distinct biology and a more aggressive clinical behavior compared to their polypoid counterparts. In the present study, we aimed to compare the mutation spectrum of 14 cancer genes, between these two phenotypes.

METHODS

A consecutive series of 106 flat and 93 polypoid adenomas was analyzed retrospectively for frequently occurring mutations in "hot spot" regions of KRAS, BRAF, PIK3CA and NRAS, as well as selected mutations in CTNNB1 (β-catenin), EGFR, FBXW7 (CDC4), PTEN, STK11, MAP2K4, SMAD4, PIK3R1 and PDGFRA using a high-throughput genotyping technique. Additionally, APC was analyzed using direct sequencing.

RESULTS

APC mutations were more frequent in polypoid adenomas compared to flat adenomas (48.5% versus 30.3%, respectively, p = 0.02). Mutations in KRAS, BRAF, NRAS, FBXW7 and CTNNB1 showed similar frequencies in both phenotypes. Between the different subtypes of flat adenomas (0-IIa, LST-F and LST-G) no differences were observed for any of the investigated genes.

CONCLUSION

The lower APC mutation rate in flat adenomas compared to polypoid adenomas suggests that disruption of the Wnt-pathway may occur via different mechanisms in these two phenotypes. Furthermore, in contrast to previous observations our results in this large well-defined sample set indicate that there is no significant association between the different morphological phenotypes and mutations in key genes of the RAS-RAF-MAPK pathway.

Macroscopic morphologic subtypes of laterally spreading colorectal tumors showing distinct molecular alterations

Recent advances in colonoscopic techniques have resulted in more frequent detection of superficial-type colorectal tumors, that is, laterally spreading tumors (LSTs), although little is known about the characteristic clinical features and genetic alterations of LSTs. To elucidate the molecular characteristics of LSTs, genetic alterations in the KRAS, BRAF and PIK3CA genes and abnormal expression of the p53, beta-catenin and MYC proteins were analyzed using direct DNA sequencing and immunohistochemistry for 50 protruded-type tumors (Protruded), 35 granular-type LSTs (LST-G) and 19 nongranular-type LSTs (LST-NG). In addition, loss of heterozygosity (LOH) close to the adenomatous polyposis coli (APC) gene (5q21) was examined in these tumors. In univariate analyses, significant differences were noted in the percentages with KRAS mutations (Protruded, LST-G, LST-NG = 30.0%, 54.3%, 21.1%, respectively, p = 0.0156), nuclear accumulation of beta-catenin (Protruded, LST-G, LST-NG = 50.0%, 37.1%, 68.4%, respectively, p = 0.0267), expression of MYC (Protruded, LST-G, LST-NG = 26.0%, 17.1%, 42.1%, respectively, p = 0.0456) and LOH at the APC gene locus (Protruded, LST-G, LST-NG = 22.0%, 20.0%, 47.4%, respectively, p = 0.0302). Multivariate analysis demonstrated that the macroscopic subtype of LST was significantly associated with KRAS mutation (for LST-NG: odds ratio [OR] 0.23, 95% CI 0.06-0.90) and nuclear accumulation of beta-catenin (for LST-NG: OR 4.05, 95% CI 1.11-14.8). Our data revealed that the 2 subtypes of LST have different molecular characteristics, suggesting that 2 or more different molecular mechanisms result in colorectal tumors with a similar growth pattern.

Correlation of laterally spreading type and JC virus with methylator phenotype status in colorectal adenoma

Accurate frequencies of CpG island methylator phenotype (CIMP) have not been determined for laterally spreading tumors (LSTs) and other flat-type colorectal adenomas, and the role of JC virus T-antigen (T-Ag) in these tumors is unclear. We used MethyLight assay to analyze the relationship between CIMP status and clinicopathologic characteristics in tissue from 72 LST of granular-type (LST-G), 35 LST of nongranular-type (LST-NG), 54 protruded-type adenomas, and 89 colorectal cancers. We also investigated the relationship between CIMP status and T-Ag by immunohistochemistry. With the use of 5 markers for CIMP status, tumors were classified as CIMP-high (> or = 4/5 methylated promoters), CIMP-low (1/5 to 3/5 methylated promoters), or CIMP-0 (no methylated promoters). The proportion classified as CIMP-0 status was 5.6% for protruded-type adenoma, 17.1% for LST-NG, and 29.2% for LST-G (LST-G versus protruded-type adenoma, P = .001). CIMP-low status was established for 62.5% of LST-G, 74.3% of LST-NG, and 81.5% of protruded-type adenomas. CIMP-high status was established for 8.3% of LST-G, 8.6% of LST-NG, and 12.9% of protruded-type adenomas. The proportions of CIMP-low and CIMP-high status were not significantly different between the 3 groups. Multiple logistic analysis showed that LST-G appearance was the only significant factor for identifying CIMP-0 status. BRAF mutation was the only significant factor for identifying CIMP-high status. T-Ag expression increased with CIMP status and was not associated with macroscopic appearance. In conclusion, among colorectal adenomas, CIMP-high status was determined by BRAF mutation and not by macroscopic type, unlike CIMP-0. JC virus T-Ag may be important in determining methylator phenotype.

Hypermethylation status of APC inversely correlates with the presence of submucosal invasion in laterally spreading colorectal tumors

Little is known about epigenetic alterations in laterally spreading colorectal tumors (LSTs). The goal of the present study was to elucidate the epigenetic background of LSTs and compare the methylation status of DNA CpG islands (CGIs) with clinicopathologic features. Methylation of MINT1, MINT2, MINT31, p16, O(6)-methylguanine-DNA methyltransferase (MGMT), adenomatous polyposis coli (APC), and human MutL homologue 1 (hMLH1) in 42 LSTs was assessed by methylation-specific polymerase chain reaction (MSP) and compared with clinicopathologic parameters. The frequency of hypermethylation was 12.5% (4/32) for MINT1, 40.0% (16/40) for MINT2, 25.0% (10/40) for MINT31, 25.7% (9/35) for p16, 7.7% (3/39) for hMLH1, 26.5% (9/34) for MGMT, and 35.9% (14/39) for APC. APC methylation was inversely associated with submucosal invasion (P = 0.034), which was not found in any of 14 LST cases with APC methylation, whereas submucosal invasion was present in 8 of 25 (32.0%) cases without APC methylation. These data suggest that hypermethylation of APC could be a predictive marker for the absence of submucosal invasion of LSTs.

Flat-type colorectal advanced adenomas (laterally spreading tumors) have different genetic and epigenetic alterations from protruded-type advanced adenomas

Morphologically, colorectal adenomas can be divided into two groups, protruded-type and flat-type. However, the accurate frequencies of genetic and epigenetic alterations in flat-type colorectal advanced adenomas (laterally spreading tumors) have remained largely unknown. In the current study, we investigated genetic and epigenetic alterations in 101 flat-type colorectal advanced adenomas and 68 protruded-type colorectal advanced adenomas by using direct DNA sequencing and quantitative real-time PCR (MethyLight), respectively. KRAS mutation was detected in a significantly higher percentage of flat-type adenomas (35%) than in protruded-type adenomas (13%). When the samples were limited to the tumors in the distal colon, the difference of KRAS mutation was still significant. KRAS mutation in G-to-A transitions at codons 12 and 13 was detected in a significantly higher percentage of flat-type adenomas (26%) than in protruded-type adenomas (9%). BRAF and beta-catenin mutations were detected in 3 and 8% of the 101 flat-type adenomas, respectively. No significant difference was found between frequencies of those mutations in flat-type adenomas and protruded-type adenomas. Methylations of MGMT, CDKN2A (p16) and MLH1 were detected in 28, 33 and 9% of the 101 flat-type adenomas, respectively. CDKN2A methylation was detected in a significantly lower percentage of flat-type adenomas than in protruded-type adenomas (63%). Methylation of at least one gene was detected in a significantly lower percentage of flat-type adenomas (54%) than in protruded-type adenomas (78%). In conclusion, KRAS mutation was frequently detected in flat-type advanced adenomas and the mutational patterns in most of them with KRAS mutations were a transition from G-to-A. Therefore, these genetic alterations seem to play an important role in the development of flat-type advanced adenomas, especially in the distal colon. Epigenetic alterations infrequently occurred in flat-type advanced adenomas, suggesting that they have different genetic and epigenetic alterations from those of protruded-type advanced adenomas.

Relationship between molecular markers and endoscopic findings in laterally spreading tumors

BACKGROUND AND AIM

Characteristic clinicopathological features of laterally spreading tumors (LSTs) have been reported by endoscopists; however, only a few studies have been conducted on the biological features. These studies were not fully associated with the endoscopic findings of LSTs. The aim of this study was to estimate the biological features of each type of endoscopic finding of LST using two molecular markers, matrix metalloproteinase-7 (MMP-7) and beta-catenin.

METHODS

Expression of the molecular markers and the endoscopic findings were compared in 22 LSTs and 14 subpedunculated polyps. MMP-7 and beta-catenin were immunostained. Three types of representative endoscopic findings of LST were defined as segments in LSTs. They were 15 granular segments, seven large nodular segments, and seven flat segments that corresponded to the area composed of aggregates of similar size granules, large nodules of diameter more than 10 mm, and a flat surface with no granule, respectively.

RESULTS

Expression of MMP-7 and coexpression of MMP-7 and beta-catenin were higher in large nodular segments than in granular segments (P < 0.0167). Among the three types of segments, flat segments showed the highest expression densities of beta-catenin accumulated in the nucleus. Large nodular segments and subpedunculated polyps showed similar expression patterns for the molecular markers.

CONCLUSIONS

This study provides new and important information on the relationship between the molecular markers and endoscopic findings of LSTs.

Mutational analysis of beta-catenin and the RAS-RAF signalling pathway in early flat-type colorectal tumours

Morphologically, early colorectal tumours can be divided into two groups, protruded-type and flat-type. However, little is known about genetic mechanisms of the latter. We investigated mutations of beta-catenin, KRAS, BRAF, and PIK3CA in 310 early colorectal tumours. beta-catenin mutation was detected in 7.1% of 310 tumours. beta-catenin mutation was detected in a significantly higher percentage of flat-type tumours with depressed areas (4/17, 23.5%) than in other tumours (18/293, 6.1%; p=0.0246). KRAS, BRAF, and PIK3CA mutations were detected in 21.6%, 5.4%, and 1.0% of 310 tumours, respectively. Concomitant mutations of beta-catenin and KRAS or BRAF were detected in seven tumours. Mutation of at least one gene was detected in a significantly higher percentage of flat-type tumour tissues (75/193, 38.9%) than in protruded-type tumour tissues (25/117, 21.4%; p=0.0014), and it was correlated significantly with size (p=0.0001). In conclusion, beta-catenin mutation seemed to play an important role in flat-type tumours, especially in those with depressed areas. The genetic abnormalities could arise and accumulate in the early stage of colorectal tumourigenesis, and seem to contribute to the development of flat-type tumour.

Different expressions of dynamin II between colorectal cancer cell lines

AIM: To detect different expressions of dynamin II between laterally spreading tumor (LST) and SW480 cell line as well as between LST and Lovo cell line.

METHODS: Different expressions were detected using semiquantitative polymerase chain reaction (PCR) method. Extraction of total RNA from LST, SW480 and Lovo cell lines, respectively, was performed to synthesize cDNA through reverse transcription. The conditions of PCR were optimized, including annealing temperature, cycle parameters and amount of template. UVI imaging was used to detect the PCR products.

RESULTS: Dynamin II and amplificated segment of beta-actin were 475 bp and 239 bp respectively. The expression of dynamin II in colorectal LST cell line was twifold higher than that in both SW480 and Lovo cell lines. The genetic sequence we gained from targeted gene was the same as the sequence of L36983 and BC016045 in GeneBank.

CONCLUSION: Dynamin II is differently expressed in LST cell line compared with SW480 and Lovo cell lines. It may play an important role in the morphology and cancerogenesis of the tumor.