Decreased ADAMTS-1 induced increased VEGF levels in conditioned medium from MDA-MB-231 cells (A) and tubulogenesis in HUVECs (B). ELISAs were carried out to quantify the VEGF levels in conditioned medium from MDA-MB-231 or MCF7 cells treated with siRNA targeting ADAMTS-1. MDA-MB-231 cells with reduced ADAMTS-1 expression exhibited a statistically significant increase in VEGF in conditioned medium (A, right graph). Conversely, MCF7 cells with ADAMTS-1 silenced by siRNA showed a decrease in VEGF levels in conditioned medium (A, left graph). HUVECs were grown in conditioned medium derived from MDA-MB-231 cells transfected with ADAMTS-1 siRNA. In this situation, tubulogenesis was induced after 6 hours (B, right panel). The control cells (medium from cells transfected with control siRNA) showed no particular architecture (B, left panel), whereas tube length was increased in HUVECs treated with conditioned medium derived from MDA-MB-231 cells transfected with ADAMTS-1 siRNA (C). The immunoblot shows the difference in VEGFR expression between MDA-MB-231 and MCF7 cells (D). The asterisks indicate significant data in comparison to the control (*p < 0.05; ***p<0.001). The panels in (B) represent volumetric renderings from at least 10 confocal optical sections (software Imaris 7.1). The results in (C) represent the mean ± standard error of three experiments carried out at least three times. Scale bars: 50 μm.