Quantitative real-time PCR. To assess expression of proangiogenic factors in the tumors, RNA extraction, RT-PCR, and first-strand cDNA synthesis for quantitative real-time PCR analysis (Q-PCR) were carried out as described previously (54, 55). Target gene sequences were from the National Center for Biotechnology Information GenBank databases. Q-PCR was performed using an ABI PRISM 7300 sequence detection system (Applied Biosystems). RNA expression was calculated based on a relative standard curve representing 4-fold dilutions of human cDNA. Q-PCR data were expressed as a relative quantity based on the ratio of the fluorescent change observed with the target gene to the fluorescent change observed with 18S ribosomal subunit. Hepatic endothelial cell and MEF RNA samples were isolated with the Qiagen RNeasy kit following the manufacturer’s directions, and Q-PCR was performed as described above, using the Applied Biosystems TaqMan Assay with prevalidated murine probes and primer sets. A dilution series was carried out for each gene, and the 18S ribosomal subunit was used as an internal control.