Eui Jin Lee

Molecular features of colorectal hyperplastic polyps and sessile serrated adenoma/polyps from Korea.

Abundant recent data suggest that sessile serrated adenoma/polyp (SSA/P) is an early precursor lesion in the serrated pathway of carcinogenesis. It is believed that SSA/Ps develop cancer by an SSA/P-dysplasia-carcinoma sequence. Hyperplastic polyps (HPs) share some histologic and molecular characteristics with SSA/P, but it is unclear whether SSA/Ps are derived from HPs or whether they develop by a different pathogenetic pathway. Previous studies have shown that serrated polyps from Korean patients show different prevalence rates of certain molecular abnormalities compared with similar lesions from American patients, and this suggests that lifestyle and dietary factors may influence the serrated neoplasia pathway. The purpose of this study was to evaluate the molecular features of HPs and SSA/Ps, the latter both with and without dysplasia, from Korean patients and to compare the findings with similar lesions from American patients. One hundred and eleven serrated polyps, consisting of 45 HPs (30 microvesicular, 11 goblet cell, 4 mucin depleted) and 56 SSA/Ps (36 with dysplasia, 20 without dysplasia), were retrieved from the pathology files of a large medical center in Korea and 38 SSA/P from American patients were evaluated for BRAF and KRAS mutations, microsatellite instability, and hypermethylation of O6-methylguanine-DNA methyltransferase (MGMT), hMLH1, adenomatous polyposis coli (APC), p16, methylated in tumor-1 (MINT-1), MINT2, and MINT31. Methylation of hMLH1 was performed using 2 different sets of primers. Twenty-three conventional adenomas from Korean patients were included as controls. The data were compared between polyp subtypes and between polyps in the right versus the left colon. With regard to HP, KRAS mutations were present in 31.1% of polyps and BRAF mutations in 46.7% of polyps. KRAS mutations were significantly more common in goblet cell HP and BRAF in microvesicular HP (MVHP). Methylation of MGMT, hMLH1, APC, p16, MINT1, MINT2, and MINT31 were present in 42.2%, 64.4% (and 24.4%), 37.8%, 60%, 68.9%, 51.1%, and 60% of HPs. CpG island methylator phenotype high was noted in 60% of HPs. Methylation of hMLH1, p16, MINT2, and MINT31 were more frequent in MVHPs compared with other types of HPs. In contrast, SSA/Ps showed KRAS and BRAF mutations in 12.5% and 60.7% of cases, respectively. Methylation of all tumor-related genes, except hMLH1 (23.2% using 1 type of primers) and APC (37.5%), occurred in >50% of lesions, and CpG island methylator phenotype (CIMP) high was noted in 76.8% of cases. None of the molecular findings were significantly more common in SSA/P with, versus those without, dysplasia, but only 2 of the 36 polyps with dysplasia were of the conventional adenomatous type; the remainder (34 of 36) was of the serrated type. Nevertheless, both SSA/P with conventional adenomatous dysplasia showed methylation of MGMT, APC, MINT1, and MINT31 and were CIMP high. BRAF mutations, methylation of most tumor related genes, and CIMP high occurred more frequently in HPs and SSA/Ps in the right colon, compared with the left colon. In fact, no significant differences were observed between HPs and SSPs of the right colon and HPs and SSA/Ps from the left colon. Furthermore, compared with American patients, Korean male individuals were affected more frequently than female individuals, and both BRAF mutations and hMLH1 methylation were less frequent in the latter compared with the former. We conclude that HPs and SSA/Ps in Korean patients share some, but not all, clinical and molecular characteristics to those that occur in Americans. The data support the theory that the right and left colon are biologically different with regard to susceptibility to serrated cancer, and that anatomic location (right vs. left) may be a more significant risk factor of progression than the histologic type of polyp. Our data also support the theory that right-sided MVHPs may be a precursor to SSA/P.

KRAS mutations in traditional serrated adenomas from Korea herald an aggressive phenotype.

The pathogenesis and risk of malignancy of traditional serrated adenomas (TSAs) are unclear. In North America, TSAs are relatively uncommon, occur mainly in the left colon, and in some studies, have not been shown to have a strong association with hyperplastic polyp (HPP) or sessile polyp adenoma (SSA) precursor lesions. In the Far East, and particularly in Korea, TSAs are more common and occur both in the left and right colon. However, the pathogenesis of TSAs in Korean patients, and the similarity to those that occur in North America, have never been evaluated. The purpose of this study was to determine the frequency and type of precursor lesion in TSAs, and to determine the molecular profile according to the grade of histologic dysplasia and/or cancer and anatomic location of the colon in a cohort of Korean patients. One hundred and twelve TSAs were evaluated pathologically and categorized according to the grade of dysplasia (either low or high grade) and the presence or absence of adenocarcinoma. TSAs were also separated into those with serrated versus conventional adenomatous dysplasia. As controls 35 conventional adenomas were evaluated, 14 of which had adenocarcinoma. All lesions were evaluated for the presence and type of precursor lesions and for KRAS and BRAF mutations and methylation of MGMT, hMLH1, and APC. A nondysplastic precursor lesion (HPP or SSA) was identified in 35 TSAs (31.3%). TSAs with a precursor lesion were more commonly found in the right colon compared with the left colon (P=0.03). Mutations of KRAS and BRAF and methylation of MGMT, hMLH1, and APC were present in 29%, 55%, 63%, 56%, and 37% of TSAs, respectively. TSAs with high-grade dysplasia and intramucosal adenocarcinoma showed a significantly higher frequency of KRAS mutation and MGMT methylation, and a significantly lower frequency of BRAF mutations, compared with TSAs with low-grade dysplasia (P<0.05). KRAS mutations were more prevalent in TSAs from the left colon and correlated significantly with higher grades of dysplasia. In a subgroup of TSAs in which both the precursor and neoplastic components were evaluated, a similar molecular profile was shown in both types of epithelium. Our results suggest that up to one-third of TSAs show a histologically identifiable nondysplastic HPP or SSA precursor lesion, particularly in lesions from the right colon. The development of KRAS mutations and methylation of MGMT may herald the onset of an aggressive phenotype in the neoplastic progression of TSAs and also suggests that a fusion between the serrated pathway of carcinogenesis and the chromosomal instability pathway may occur in some TSAs. Further studies are needed to determine the natural history and risk of malignancy of TSAs, specifically related to the anatomic site of development.

The CpG island methylator phenotype may confer a survival benefit in patients with stage II or III colorectal carcinomas receiving fluoropyrimidine-based adjuvant chemotherapy

BackgroundColorectal carcinoma (CRC) with CpG island methylator phenotype (CIMP) is recognized as a distinct subgroup of CRC, and CIMP status affects prognosis and response to chemotherapy. Identification of CIMP status in CRC is important for proper patient management. In Eastern countries, however, the clinicopathologic and molecular characteristics and prognosis of CRCs with CIMP are still unclear.MethodsA total of 245 patients who underwent their first surgical resection for sporadic CRC were enrolled and CIMP status of the CRCs was determined using the quantitative MethyLight assay. The clinicopathologic and molecular characteristics were reviewed and compared according to CIMP status. In addition, the three-year recurrence-free survival (RFS) of 124 patients with stage II or stage III CRC was analyzed in order to assess the effectiveness of fluoropyrimidine-based adjuvant chemotherapy with respect to CIMP status.ResultsCIMP-high CRCs were identified in 34 cases (13.9%), and were significantly associated with proximal tumor location, poorly differentiated carcinoma, mucinous histology, and high frequencies of BRAF mutation, MGMT methylation, and MSI-high compared to CIMP-low/negative carcinomas. For patients with stage II or III CIMP-low/negative CRCs, no significant difference was found in RFS between those undergoing surgery alone and those receiving surgery with fluoropyrimidine-based adjuvant chemotherapy. However, for patients with CIMP-high CRCs, patients undergoing surgery with fluoropyrimidine-based adjuvant chemotherapy (n = 17; three-year RFS: 100%) showed significantly better RFS than patients treated with surgery alone (n = 7; three-year RFS: 71.4%) (P = 0.022).ConclusionsOur results suggest that selected patients with CIMP-high CRC may benefit from fluoropyrimidine-based adjuvant chemotherapy with longer RFS. Further large scale-studies are required to confirm our results.

Prognostic stratification of high-risk gastrointestinal stromal tumors in the era of targeted therapy.

Background:Recently, a trial of adjuvant imatinib for primary R0-resected intermediate and high-risk gastrointestinal stromal tumors (GISTs) significantly improved recurrence-free survival. But identifying patients having higher chances of recurrence will reduce economic losses and prevent adverse side effects caused by adjuvant treatment. Methods:Tissue samples from 93 patients with high-risk GISTs were studied for p16, CD34, and CD44 protein expression and mutations of KIT and PDGFRA gene. Clinicopathologic, immunohistochemical, and mutation results were compared with clinical outcome by univariate and multivariate analyses. Results:KIT mutations were observed in 75 cases (81%) including 46 exon 11 deletion mutations and 31 deletions affecting codons 557–558. A novel 12 bp deletion mutation (KHNG484-488) on KIT exon 9 was detected in a small intestinal GIST. For recurrence-free survival, R0 resection, organ-confined disease stage, and female sex are better prognostic factors in univariate analysis and disease stage was the only factor predicting recurrence (P = 0.02) in multivariate analysis. In overall survival, mutation types, presence of mutation, location of GISTs, and mitosis were significant by univariate analysis. After multivariate analysis, mitotic counts and presence of KIT mutation corresponded to independent prognostic factors. Moreover, mitosis, KIT exon 11 deletion mutation, and deletions affecting exon 557–558 predict recurrence in R0-resected high-risk GISTs (P < 0.05). Conclusion:Prognostic stratification in high-risk GISTs will help identify patients with high-risk GIST who may benefit from adjuvant therapy.

KIT amplification and gene mutations in acral/mucosal melanoma in Korea

Yun J, Lee J, Jang J, Lee EJ, Jang KT, Kim JH, Kim K‐M. KIT amplification and gene mutations in acral/mucosal melanoma in Korea. APMIS 2011; 119: 330–5.

Prognostic significance of O6-methylguanine DNA methyltransferase and p57 methylation in patients with diffuse large B-cell lymphomas

To evaluate whether promoter methylation is related to responsiveness for chemotherapy or clinical outcome, we performed an association analysis between methylation and clinical outcomes. Patients with nodal diffuse large B‐cell lymphomas (DLBCL) at a single institute (n=44) were studied for methylation of tumor‐related genes, MGMT, p15INK4B, p16INK4A, p16INK4A, Mad2, TMS1/ASC, CASP8, and GSTP1. The clinical behavior of DLBCL after chemotherapy was followed up and analyzed. Hypermethylation of promoters of MGMT, p15INK4B, p16INK4A, p16INK4A, Mad2, and TMS1/ASC genes was observed in 52.3%, 31.8%, 54.5%, 47.7%, 50%, and 2.3% of the cases, respectively. Methylation of CASP8 and GSTP1 genes was not observed. Promoter methylation was not related to chemo‐responsiveness, disease‐free survival, and progress of disease after chemotherapy. However, in overall survival analyses, MGMT methylation (p<0.05) and responsiveness to chemotherapy (p<0.01) were significant prognostic factors in patients with DLBCL. In the low‐risk group, patients with p57 methylation showed longer overall survival than patients without p57 methylation (p=0.02) and all patients with p57 methylation were alive during follow‐up. Our results demonstrate that aberrant promoter methylation of MGMT and p57 is an additional biological marker for predicting increased overall survival in patients with DLBCL.

Composite glandular-endocrine cell carcinomas of the stomach: clinicopathologic and methylation study.

Four cases of very rare composite glandular‐endocrine cell carcinoma of the stomach are presented with methylation findings. All but one of the tumors arose in the antrum and two of them were at the early stage. Each composite carcinoma was accompanied by atrophic and metaplastic gastritis in the adjacent mucosa. Three cases showed lymph nodes metastasis, and one of them showed both glandular and neuroendocrine tumor components within the metastatic nodes. Mucin stains were positive in the adenocarcinoma areas while only the neuroendocrine markers were positive in neuroendocrine tumor components. Of all seven markers tested for, p16INK4A methylation was observed in both components of one composite carcinoma and hMLH1 was methylated in the neuroendocrine tumor component within the same tumor. An additional six gastric large cell neuroendocrine carcinomas showed no methylation. Follow up of patients indicated short survival in patients with poorly differentiated neuroendocrine carcinoma components and advanced stages of tumors, while patients with well‐differentiated neuroendocrine tumor components and early stages showed long disease‐free survival. Our results suggest that hypermethylation of tumor suppressor genes is rare in gastric composite and neuroendocrine carcinomas, and prognosis of gastric composite carcinomas appears to be related to the histopathology of neuroendocrine components and tumor stage.

Filiform serrated adenoma is an unusual, less aggressive variant of traditional serrated adenoma

Aims: Filiform serrated adenoma (SA) is an uncommon type of polyp that shows morphological features similar to traditional serrated adenoma (TSA). Unlike TSA, filiform SA is composed predominantly of prominent, thin, elongated filiform projections lined by neoplastic epithelium with a serrated contour. However, the molecular pathogenesis underlying filiform SA is unclear and its relationship with TSA has not been explored yet. The purpose of this study was to determine the clinicopathological and molecular characteristics of filiform SA in a cohort of Korean patients. Methods: Thirteen filiform SAs were evaluated for mutations of BRAF and KRAS genes, microsatellite instability (MSI), and promoter hypermethylation of hMLH1, MGMT, p16, MINT1, MINT2, MINT31 and the APC genes. The clinicopathological and molecular results were compared to results from previously published studies of left-sided TSAs among Koreans. Results: All but one filiform SAs were located in the left colon and showed low grade dysplasia. BRAF and KRAS mutations were observed in six (46.2%) and four (30.3%) filiform SAs, respectively. Hypermethylation of hMLH1 (using both Herman et al. and Park et al.), MGMT, p16, MINT1, MINT2, MINT31 and the APC gene was found in 30.3% and 7.7%, 38.5%, 15.4%, 53.8%, 46.2%, 38.5% and 15.4% of cases, respectively. Thirteen filiform SAs were MS stable and classified with a CpG island methylator phenotype (CIMP) of high in five, CIMP low in five and CIMP negative in three cases. Compared to TSAs in the left colon, methylation of hMLH1, APC, and MGMT was less frequent in cases of filiform SA, but the filiform SA sizes were larger. Conclusion: Our findings suggest that filiform SA may grow larger without acquisition of additional genetic alterations and can be categorised as a rare, less aggressive variant of TSA with unique morphology.

Plexiform angiomyxoid myofibroblastic tumor of the stomach: report of two cases and review of the literature.

Plexiform angiomyxoid myofibroblastic tumor (PAMT) of the stomach is a recently recognized entity. Because of its rarity, only 22 cases have been reported in the English-language literature and most of these are single case reports. We report two cases of gastric PAMT. The tumor cells were bland and plexiform arranged in a myxoid stroma, which was positive for alcian blue. Immunohistochemically, the tumor cells were positive for smooth muscle actin, but negative for c-kit, CD34, desmin, S-100 protein, epithelial membrane antigen, neurofilament, and protein kinase C-theta. Mutation analyses for exon 9, 11, 13, and 17 of KIT genes and 12, 14, and 18 of the platelet-derived growth factor receptor alpha (PDGFRA) genes were performed and the tumors were wild-type for mutation.

GSTT1 copy number gain and ZNF overexpression are predictors of poor response to imatinib in gastrointestinal stromal tumors.

Oncogenic mutations in gastrointestinal stromal tumors (GISTs) predict prognosis and therapeutic responses to imatinib. In wild-type GISTs, the tumor-initiating events are still unknown, and wild-type GISTs are resistant to imatinib therapy. We performed an association study between copy number alterations (CNAs) identified from array CGH and gene expression analyses results for four wild-type GISTs and an imatinib-resistant PDGFRA D842V mutant GIST, and compared the results to those obtained from 27 GISTs with KIT mutations. All wild-type GISTs had multiple CNAs, and CNAs in 1p and 22q that harbor the SDHB and GSTT1 genes, respectively, correlated well with expression levels of these genes. mRNA expression levels of all SDH gene subunits were significantly lower (P≤0.041), whereas mRNA expression levels of VEGF (P=0.025), IGF1R (P=0.026), and ZNFs (P<0.05) were significantly higher in GISTs with wild-type/PDGFRA D842V mutations than GISTs with KIT mutations. qRT-PCR validation of the GSTT1 results in this cohort and 11 additional malignant GISTs showed a significant increase in the frequency of GSTT1 CN gain and increased mRNA expression of GSTT1 in wild-type/PDGFRA D842V GISTs than KIT-mutant GISTs (P=0.033). Surprisingly, all four malignant GISTs with KIT exon 11 deletion mutations with primary resistance to imatinib had an increased GSTT1 CN and mRNA expression level of GSTT1. Increased mRNA expression of GSTT1 and ZNF could be predictors of a poor response to imatinib. Our integrative approach reveals that for patients with wild-type (or imatinib-resistant) GISTs, attempts to target VEGFRs and IGF1R may be reasonable options.