To determine whether PTN induced the monocyte cell line THP-1 to express VEC genes, total RNA was isolated and separated by 1% agarose gel electrophoresis after THP-1 monocytes were cultured with PMA, PCL serum, or normal human serum or cocultured with U266 and RPMI8226. In addition, THP-1 cells exposed to U266 or PCL serum were also treated with either anti-PTN or isotype-matched control antibodies during tissue culture. RT-PCR was performed on RNA from THP-1 cells with primers specific for the Tie-2, Flk-1, VWF, and GAPDH genes. HCAECs were used as a positive control.