Abstracts
1999 Digestive Disease Week

# 2158 ISLET PROLIFERATION IS INHIBITED BY OVEREXPRESSION OF MENIN.
Allan Y Wu, WLA VA Med Ctr and UCLA Sch of Medicine, Los Angeles, CA; Shimode T Alan, J C Arora, Eric H Wang, WLA VA Med Ctr and UCLA, Los Angeles, CA; Passarro Edward Jr., UCLA Sch of Medicine, Dept of Surg, Los Angeles, CA; Mark P Sawicki, WLA VA Med Ctr and UCLA Sch of Medicine, Los Angeles, CA

MENIN, a putative tumor supressor gene, is delected or mutated in patients with MEN-1 syndrome and some sporadic islet tumors. The exact function of MENIN has not been elucidated, though has been implicated to be involved in cell proliferation based on fruit fly studies. We hypothesized that overexpression of MENIN leads to decreased proliferation in pancreatic islet cells in culture. METHODS: A mouse pancreatic islet cell line, TGP-1, was transiently transfected with a MENIN-GFP construct and a control vector expressing Renilla luciferase. The control group was tranfected with empty GFP expression vector and control vector R. luciferase Cells were pulsed with 10uCi/ml of H3-Thy and harvested 24 and 48 hours post treatment. Transfection efficiency was assessed prior to harvest with direct visualization of green flourescence under an inverted flourescence microscope in addition to measuring expression of cotransfected R. luciferase. DNA incorporation was measured by liquid scintillation. Direct proliferation and cytotoxicity was determined by histomorphometry and quantitation. Experiments were performed in quadruplicate and data was analyzed for statistical significance. RESULTS: Rate of DNA synthesis was decreased from 13,000 CPM to 10,000 CPM in MENIN transformed islets (p = 0.005) at 24 hours post treatment with H3-Thy. No effect was seen at 48 hours. Histomorphomotry and direct cell counting revealed no significant difference in the number of dead cells seen after transfection with either MENIN or empty vector. Direct proliferation studies revealed less confluent cells in the MENIN transformed wells (20%) versus sham and blank vector transformed cells (80 and 100% respectively). CONCLUSION: MENIN functions as a tumor surpessor by inhibiting proliferation and DNA synthesis in mouse islet cells.

Copyright 1996 - 1999, SSAT, Inc.