Grading of gastrointestinal neuroendocrine neoplasms (GI-NENs) relies mainly on mitotic activity and Ki-67 proliferation index. It is often difficult to predict metastatic potential of these neoplasms. Recent studies have shown that GI-NENs express a wide spectrum of microRNAs. We examined two microRNAs (miR-96 and miR-133a) that were recently identified in GI-NENs to determine if they could assist in evaluating the biological behavior of these neoplasms. A tissue microarray (TMA) was constructed with 51 primary GI-NENs, mainly from the small intestine and metastatic tumors from the same cases, including liver metastases (N = 20) and lymph node metastases (N = 33). The cases were immunohistochemically stained for chromogranin A, synaptophysin, and Ki-67. In situ hybridization (ISH) was done with probes from Exiqon (Woburn, MA). Quantitative RT-PCR (qRT-PCR) was also performed on all the cases (N = 105). ISH analysis showed that miR-96 expression was significantly higher in the liver metastatic neoplasms compared to the primary NENs (p < 0.05); however, it was not significant for miR-133a expression levels. qRT-PCR showed that miR-96 levels were increased during progression from the primary tumors to metastases in the liver. qRT-PCR showed a decrease in miR-133a in the liver metastases compared to the primary tumors (p < 0.05). Appendiceal carcinoids without metastases (n = 3) had low levels of miR-96 and high levels of miR-133a by qPCR. The study suggests that analysis of these two microRNAs by qRT-PCR may be useful in detecting more aggressive GI-NENs and that ISH analysis may also assist in the evaluation of patients with GI-NENs.
Keywords: Carcinoid; Gastrointestinal neuroendocrine neoplasm; In situ hybridization; miR-133a; miR-96.