Systemic therapy with PPARγ ligands prevents metastatic invasion after removal of primary LLC. (a) Visual comparison of mouse lungs on treatment day 17 with vehicle (Ctr) or rosiglitazone (R50, 50 mg/kg/d; R100, 100 mg/kg/d). Scale bar, 1 cm. (b) Rosiglitazone (R50 and R100) prevents metastasis, as represented by a significant decrease in lung weight, which correlates with tumor burden. R400, 400 mg/kg/d. NL, normal lung weight. (c) Hematoxylin-and-eosin staining showing individual LLC tumor cells inside blood vessels (black arrowheads) in lungs of rosiglitazone-treated mice. Scale bar, 50 μm. (d and e, insets) Typical patterns of centrosomal abnormalities in control LLC metastasis, as demonstrated by immunofluorescence staining for pericentrin (green). (d and e) In rosiglitazone-treated mouse lungs, immunofluorescence double staining for pericentrin and PECAM (endothelial marker) demonstrates LLC tumor cells inside blood vessels. Abnormal centrosomes of tumor cells stained with pericentrin are green (white arrowheads), and endothelium is red. The asterisk shows red blood cells (d, red). Hoechst staining of nuclei is blue. Scale bar, 5 μm. (f and g) Effect of rosiglitazone treatment on MMP and TIMP activity. Representative gelatin zymograms demonstrate that the activity of the predominant gelatinase detected in HUVECs appears to be unaffected by rosiglitazone treatment (f). In contrast, TIMP bioactivity assays demonstrate an increase in TIMP activity up to approximately 1.0 μM rosiglitazone (g).