Expression of VEGF after transfection of PC-3 cells with VEGF or mock expression vectors. Western blot analysis of conditioned medium of PC-3/VEGF cell clones revealed several clones positive for 23 kD VEGF protein. The larger bands at approximately 60 kD may represent cleaved formes of larger splice variants in these cells. The expression level in mock cells was very low. One PC-3/VEGF clone (PC-3/VEGF3) and one PC-3/mock clone (PC-3/mock2) were selected for in vivo studies.