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 VEGF₁₆₅ and VEGF₁₂₁, and can be cleaved by plasmin to generate VEGF₁₁₀. The amount of VEGF₁₂₁ and VEGF₁₁₀ in biological samples has not been well studied. METHODS: We developed an ELISA that detects VEGF₁₆₅ and VEGF₁₂₁ equally, but does not detect VEGF₁₁₀. We used this ELISA together with 2 other ELISAs, one detecting VEGF₁₆₅ and the other detecting VEGF₁₆₅, VEGF₁₂₁, and VEGF₁₁₀ equally, to assess the concentrations of VEGF₁₂₁ and VEGF₁₁₀ 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 VEGF₁₂₁, and 2.3 (range <0.079 -520) fmol/mg protein for total VEGF including VEGF₁₁₀ (n = 248). VEGF concentrations measured by the 3 ELISAs were highly correlated (r = 0.91-0.94). Median estimated VEGF₁₂₁ and VEGF₁₁₀ 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 VEGF (n = 217). In contrast, VEGF₁₆₅ constituted approximately half of the total circulating VEGF. CONCLUSION: VEGF ₁₆₅, VEGF₁₂₁, and VEGF₁₁₀ may be present at significant amounts in ovarian cancer tumors.