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Abstract. DNA methylation change is known to play a crucial role in early gastric carcinogenesis. The present study aimed to identify and validate the correlation between differentially methylated regions (DMRs) and the subtypes of early gastric cancers (EGCs). Illumina Infinium methylation assay (IIMA; 450K BeadChip kit) was performed on fresh tumor and non-tumor tissues of 12 EGCs to screen the methylation status of 450,000 CpG sites. To evaluate the significance of DNA methylation in each histologic subtype, pyrosequencing assay (PA) was performed on 38 EGCs (18 intestinal-, 12 mixed-and 8 diffuse-type) using 12 genes selected from the screening. Between tumors of the intestinal-type (n=6), and diffuse-(n=4) plus mixed-types (n=2), 169 regions showed significant differences (intensity >3,000, Δβ >0.2) in IIMA. Hierarchical clustering using the 169 DMRs revealed distinct separation between the two groups. In PA using 12 selected genes from the IIMA results, the aberrant methylation statuses of DVL2 (p=0.0186) and ETS1 (p=0.0222) were significantly related to diffuse-and mixed-types rather than the intestinal-type, while C19orf35 (p=0.019) and CNRIP1 (p=0.0473) were related to the diffuse-type rather than intestinal-type, and GAL3ST2 (p=0.0158) and ITGA3 (p=0.0273) were related to the mixedtype rather than the other two types. The methylation of other genes, CLIP4, XKR6, CCDC57, MAML3 and SDC2, was related with age, tumor location, or Helicobacter infection rather than the histologic subtype. Aberrant DNA methylation of certain genes may be independently involved in each histologic subtype of EGC. Furthermore, mixed-type EGCs may be a distinctive histologic subtype based on the different subset of DMRs compared to those of other subtypes. IntroductionDespite its decreasing trend, gastric cancer (GC) still remains one of the most troublesome malignant diseases worldwide. It is the fourth most common cancer and the second leading cause of cancer-related death worldwide (1-3). In Asian countries such as Japan and Korea, it has the highest incidence among all malignancies although its overall survival rate has improved during the last few decades due to extensive screening programs (3,4). Due to the poor prognosis and limited treatment options of advanced GC, it remains a challenging task to determine effective molecular-pathological markers for early diagnosis with appropriate histological classification (5).Lauren classification, which subgroups GCs mainly as two types, intestinal and diffuse, was first introduced in 1965 and has been generally accepted as a distinct and simple histological classification of GCs by most pathologists (6). Since the two major types show distinctively different phenotypic, epidemiologic and biologic characteristics, it is believed that different genetic alterations may be implicated in each histologic type of the classification (7). However, a considerable number of GCs accounting for 10-15% of cases, share the histologic features of these two types and are designated as mixed-type ...

BackgroundCancer stem cells (CSCs) are notorious for their capacity of tumor progression, metastasis or resistance to chemo-radiotherapy. However, the undisputed role of cancer stem marker, CD133, in colorectal cancers (CRCs) is not clear yet.MethodsWe assessed 271 surgically-resected stage II and III primary CRCs with (171) and without (100) adjuvant therapy after surgery. CD133 expression was analyzed by immunohistochemical (IHC) staining and real-time RT-PCR. CD133 promoter methylation was quantified by pyrosequencing.ResultsThe CD133 IHC expression was significantly correlated with mRNA expression (p=0.0257) and inversely correlated with the promoter methylation (p=0.0001). CD133 was expressed more frequently in rectal cancer (p=0.0035), and in moderately differentiated tumors (p=0.0378). In survival analysis, CD133 expression was not significantly correlated with overall survival (OS) (p=0.9689) as well as disease-free survival (DFS) (p=0.2103). However, CD133+ tumors were significantly associated with better OS in patients with adjuvant therapy compared to those without adjuvant therapy (p<0.0001, HR 0.125, 95% CI 0.052-0.299). But the patients with CD133- tumors did not show any significant difference of survival according to adjuvant therapy (p=0.055, HR 0.500, 95% CI 0.247-1.015).ConclusionsIn stage II and III CRCs, CD133 IHC expression may signify the benefit for adjuvant therapy although it is not an independent prognostic factor.

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are potentially malignant with variable biologic behavior that originates from neuroendocrine cells of digestive tract. Recently, the existence of cancer stem cells (CSC) was demonstrated in tumors of gastrointestinal tract. CD133 is a transmembrane glycoprotein that serves as a CSC marker in various malignancies. However, the expression of CD133 in neuroendocrine neoplasms (NEN) of digestive tract has not been studied. We evaluated tissue expression of CD133 by immunohistochemistry in 90 NENs of digestive tract with their matched non-neoplastic mucosa including stomach (n = 15), small intestine (n = 7), appendix (n = 3), colon (n = 8), rectum (n = 41), pancreas (n = 2), gallbladder (n = 4) and liver (n = 10). Tumors were divided according to 2010 WHO classification. CD133 was expressed in 30.3% (17/56) of well-differentiated neuroendocrine tumors (NET), 26.1% (6/23) of poorly-differentiated neuroendocrine carcinomas (NEC) and 63.6% (7/11) of mixed adenoneuroendocrine carcinoma (MANECs). MANEC refers to existence of both adenocarcinoma and NEC together, each one comprising at least 30% of the tumor. CD133 was expressed in cytoplasm, luminal-side of cell membrane, or both and the staining pattern correlated with tumor growth pattern. CD133 expression was not significantly correlated with tumor grade, site, expression of neuroendocrine markers (chromogranin-A and synaptophysin) and patients' survival. Thus, CD133 expression may lack prognostic significance in GEP-NETs. Importantly, CD133 was not detectable in non-neoplastic neuroendocrine cells of digestive system including pancreatic islets. In conclusion, CD133 is expressed in poorly-differentiated NECs and well-differentiated NETs of the digestive tract.

Endometrial carcinomas arising in a bicornuate uterus are rare, only five case of which have been previously reported. We present a case of endometrial cancer arising in a bicornuate uterus, occurring in a 65-year-old woman. Unlike previously reported cases, our case showed mixed endometrial adenocarcinoma and undifferentiated carcinoma in one horn and focal adenocarcinoma in the other. Adequate tissue sampling of both horns is necessary for accurate diagnosis of malignancy in patients with a bicornuate uterus. Physicians should be aware of the possibility of this abnormality in cases when endometrial cancer is suspected but histology fails to confirm.