Over-Expression of miRNA miR-7-5p is a Potential Biomarker in Neuroendocrine Neoplasia of the Small Intestine

BACKGROUND/AIMS: Neuroendocrine neoplasms of the small intestine (SI-NENs) constitute 25-30% of all gastroenteropancreatic NEN. These tumors arise from enterochromaffin cells, and little is known about their microRNA (miRNA) expression. The purpose of this study was to characterize the expression of miRNAs in SI-NEN and to determine the potential of miRNAs as noninvasive blood-based biomarkers. METHODS: miRNA was purified from 15 tumor and 7 control tissue samples, converted to cDNA, and applied to a miScript miRNA PCR. The small nucleolar RNA, SNORD95, was used as an endogenous control. RESULTS: Microarray analysis revealed 7 miRNAs that showed a promising distinction between tumorous and healthy tissue. The miRNAs miR-7-5p and miR-96-5p were clearly upregulated in the tumor compared to the healthy tissue. In contrast, miRNAs miR-9-5p, miR-122-5p, miR-124-3p, miR-143-3p, and miR-144-3p showed a distinct downregulation in the tumor compared to the healthy tissue. These results were validated on a further 15 tumor samples, and the findings held true. As the miR-7-5p was significantly upregulated and revealed a low range across tumor samples, its presence was tested in the sera of 32 tumor patients and 25 healthy controls. Sera from all patients with SI-NENs had significantly higher levels of miR-7-5p than those from the 25 healthy controls (p = 0.0002), whereas there was no correlation with age, gender, or T-stage or UICC stage. CONCLUSION: The miRNA miR-7-5p may be a promising biomarker test for SI-NEN, which should be validated in a large-scale prospective study.