BackgroundAlthough there is a growing interest in developing circulating microRNA (miRNA) as noninvasive diagnostic biomarkers for the detection of high-risk colorectal adenomas and early-stage CRCs, but the comparative diagnostic significance of serum vs. exosomal miRNAs remains unexplored.MethodsBased upon published literature, we performed an initial discovery step by investigating the expression of a miRNA panel in 20 normal colonic mucosa, 27 adenomas, and 19 CRC tissues. We performed subsequent validation by quantifying expression of candidate miRNAs in total serum and in exosomes from 26 adenoma patients and 47 healthy controls, and evaluated their clinical significance and potential diagnostic value in colorectal adenomas.ResultsWe observed that the expression of four miRNAs, miR-21, miR-29a, miR-92a, and miR-135b, was significantly higher in colorectal adenomas vs. normal colonic mucosa. During validation, expression of miR-21, miR-29a and miR-92a in serum was significantly higher in adenomas vs. healthy controls, significantly correlated with adenoma size and total adenoma number within the colorectum, and significantly discriminated patients with advanced adenomas. In contrast, although exosomal miR-21 and miR-29a levels in adenoma patients were significantly higher than those of healthy volunteers, only exosomal miR-21 significantly correlated with adenoma size and total adenoma number, and could discriminate patients with high-risk adenomas.ConclusionCompared to exosomal miRNAs, serum levels of miR-21, miR-29a and miR-92a are superior diagnostic biomarkers in patients with high-risk adenomatous polyps.

555 Background: Rac GTPase activating protein (RacGAP) 1 plays a key role in controlling various cellular phenomena including cytokinesis, transformation and migration. Recently, the clinical significance of RacGAP1 expression has been reported in several malignancies. However, direct association between the RacGAP1 expression and colorectal cancer (CRC) has not been fully investigated. The aim of this study is to elucidate the function and clinical significance of RacGAP1 expression in CRC. Methods: The intrinsic functions of RacGAP1 in CRC cells were analyzed using small interfering RNA (siRNA). We analyzed RacGAP1 mRNA expression in surgical specimens from 193 CRC patients (Cohort 1) by real-time polymerase chain reaction. Then, we validated RacGAP1 protein expression using formalin-fixed paraffin-embedded samples from 298 CRC patients (Cohort 2) by immunohistochemistry. Finally, we evaluated the association between RacGAP1 mRNA and protein expression and clinicopathological data. Results: Reduced RacGAP1 expression by siRNA in CRC cell lines showed significantly decreased cellular proliferation, migration, and invasion. In Cohort 1, RacGAP1 expression in CRC was significantly higher than in adjacent normal mucosa, and increased according to TNM stage progression. High RacGAP1 expression in tumors was significantly associated with progression and prognosis. In Cohort 2, RacGAP1 protein was overexpressed mainly in the nuclei of CRC cells; however, its expression was scarcely observed in normal colorectal mucosa. RacGAP1 protein expression was significantly higher in CRC patients with higher T stage, vessel invasion, and lymph node and distant metastasis. Increased expression of RacGAP1 protein was significantly associated with poor disease-free and overall survival. Multivariate analyses revealed that high RacGAP1 expression was an independent predictive marker for lymph node metastasis, recurrence, and poor prognosis in CRC. Conclusions: Our data provide novel evidence for the biological and clinical significance of RacGAP1 as a potential biomarker for identifying patients with lymph node metastasis and poor prognosis in CRC.

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A 50-year-old man with anemia was referred to our hospital to undergo capsule endoscopy (CE), which revealed small intestinal ulcers. After 5 months of CE, he returned because of recurrent anemia without abdominal symptoms. Abdominal X-ray and computed tomography showed capsule retention in the small intestine at the pelvic cavity. The capsule remained at the same place for 7 days. We performed capsule retrieval by laparoscopy-assisted surgery with resection of the involved small intestine, including an ileal stricture. Resected specimen showed double ulcers with different morphologies, an ulcer scar with stricture, and a wide ulcer at the proximal side of the others. Each ulcer had different histopathological findings such as the degree of fibrosis and monocyte infiltration. These differences led us to consider that the proximal ulcer may have been secondarily induced by capsule retention. Our experience indicated that careful follow-up and the cooperation between medical institutions after CE examination should be undertaken for patients with incomplete examination, unknown excretion of the capsule, and/or ulcerative lesions despite the lack of abdominal symptoms. Additionally, a retained CE remaining over long periods and at the same place in the small intestine may lead to secondary ulceration.