Levamisole induced apoptosis in cultured vascular endothelial cells

1 To better understand the anticancer activity of Levamisole (LMS), which s erves as an adjuvant in colon cancer therapy in combination with 5-Fluorour acil, this study analyses LMS' ability to induce apoptosis and growth arres t in cultured human micro- and macrovascular endothelial cells (ECs) and fi broblasts. 2 Cells exposed (24 h) to Levamisole (range: 0.5-2 mmol l(-1)) alone or in combination with antioxidants (10 mmol l(-1) glutathione or 5 mmol l(-1) N- Acetylcysteine or 0.1 mmol l(-1) Tocopherol) were evaluated for apoptosis ( H-3-thymidine assays, in situ staining), mRNA/protein expression (Northern/ Western blot), and proliferation (H-3-thymidine incorporation). 3 Levamisole dose-dependently increased apoptosis in ECs to 230% (HUVECs-hu man umbilical vein ECs), 525% (adult human venous ECs) and 600% (human uter ine microvascular ECs) but not in fibroblasts compared to control cells (se t as 100%). 4 Levamisole increased in ECs integrin-dependent matrix adhesion, inhibited proliferation (-70%), reduced expression of survival factors such as clust erin (-30%), endothelin-1 (-43%), bcl-2 (-34%), endothelial NO-synthase (-3 2%) and pRb (Retinoblastoma protein: -89%), and increased that of growth ar rest/death signals such as p21 (+73%) and bak (+50%). 5 LMS (2 mmol l(-1))-induced apoptosis was inhibited by glutathione (-50%) and N-Acetylcysteine (-36%), which also counteracted reduction by Levamisol e of pRb expression, suggesting reactive oxygen species and pRb play a role in these processes. 6 The ability of LMS to selectively induce apoptosis and growth arrest in e ndothelial cells potentially hints at vascular targeting to contribute to L evamisole's anticancer activity.