Downregulation of gene expression in ex vivo–isolated liver endothelial cells from tumor-bearing immuno-competent mice. ESbL-lacZ lymphoma cells were injected intradermally into syngeneic DBA/2 mice. Twenty-eight days later, endothelial cells were isolated using liver perfusion and differential adhesion to collagen pretreated Petri dishes. Then mRNA was extracted from control (C) and tumor-bearing mice (day 28), and dot-blot analysis performed and evaluated as described in the legend to Fig 1 and in Materials and Methods. The pBluescript SK DNA which was used as vector gave no densitometric signal. The difference in the expression of all four genes between C and the day 28 tumor-bearing immuno-competent host was significant (P = .044, paired t-test).