Serum interleukin 6, plasma VEGF, serum VEGF, and VEGF platelet load in breast cancer patients.

Serum and plasma concentrations of vascular endothelial growth factor (sVEGF and pVEGF), serum concentrations of interleukin 6 (IL-6), and VEGF platelet load (VEGF/pl) in the blood of healthy controls (n = 26), breast cancer patients with locoregional disease (n = 31), and patients with progressive advanced disease (n = 73) have been compared. The 95th percentile values for the control population were 250 pg/mL for sVEGF, 30 pg/mL for pVEGF, and 1.6 pg/mL for IL-6. The 95th percentile value of the calculated VEGF/pl was 1.0 pg/10(6) platelets in the control population. Serum VEGF concentrations correlated with platelet number in all the groups. Patients with thrombocytosis had a median sVEGF concentration of 833 pg/mL, compared to 249 pg/mL in other patients (P = 0.018). Serum IL-6 levels correlated with sVEGF levels and with the calculated VEGF/pl. Serum IL-6 concentration was significantly higher in patients with breast cancer compared to healthy controls (P < 0.0001). Median IL-6 serum levels were nearly 10 times higher in patients with metastatic breast cancer as compared to the those with locoregional disease (6.0 pg/mL versus 0.7 pg/mL, respectively). Plasma VEGF and the VEGF/pl were also significantly different in the 3 groups. The ratio between sVEGF and pVEGF tended to be smaller in the metastatic breast cancer group compared to the patients with locoregional disease (median, 7.5 versus 10.1, respectively; P = 0.066), suggestive of more intravasal platelet degranulation in the former group. Serum IL-6 level is the most discriminative factor separating healthy controls and the locoregional and metastatic breast cancer patient groups. These results suggest a role for tumor-derived IL-6 in regulating VEGF expression in platelets and their precursors and also confirm the role of circulating platelets in the storage of VEGF.