A new ELISA for use in a 3-ELISA system to assess concentrations of VEGF splice variants and VEGF110 in ovarian cancer tumors

BACKGROUND: Vascular endothelial growth factor (VEGF), which affects tumor angiogenesis, is expressed as different splice variants, including the major isoforms VEGF(165) and VEGF(121), and can be cleaved by plasmin to generate VEGF(110). The amount of VEGF(121) and VEGF(121) in biological samples has not been Well studied. METHODS: We developed an ELISA that detects VEGF(121) and VEGF(121) equally, but does not detect VEGF(121). We used this ELISA together with 2 other ELISAs, one detecting VEGF,,, and the other detecting VEGF(121), VEGF(121), and VEGF(110) equally, to assess the concentrations of VEGF(121) and VEGF(121) in ovarian cancer tumors. RESULTS: The median concentrations in ovarian cancer tumor lysates were 0.61 (range <0.055-74) fmol/mg protein for VEGF(165), 1.4 (range <0.20-500) fmol/mg protein for VEGF165 plus VEGF(121), and 2.3 (range <0.079-520) fmol/mg protein for total VEGF including VEGF(110) (n = 248). VEGF concentrations measured by the 3 ELISAs were highly correlated (r = 0.91-0.94). Median estimated VEGF(121) and VEGF(110) concentrations were 0.77 and 0.58 fmol/mg protein, respectively. In lysates with measurable VEGF165 and total VEGF concentrations, mean VEGF165 was approximately 31% (SD 23%) of the total VEGE (n = 217). In contrast, VEGF(165) constituted approximately half of the total circulating VEGF. CONCLUSION: VEGF(165), VEGF(121), and VEGF(110) may be present at significant amounts in ovarian cancer tumors.