Inhibition of GRO alpha-induced human endothelial cell proliferation by the alpha-chemokine inhibitor antileukinate

GRO alpha, an autocrine mitogenic factor for melanoma cell lines, belongs t o the superfamily of alpha-chemokines. Here, we report that GRO alpha stimu lates the growth of human umbilical vein endothelial cells (HUVEC) in vitro , with proliferation being significantly stimulated by 100 nM recombinant h uman (rh) GRO alpha, Proliferation was significantly inhibited by 100 mu g/ ml antihuman GRO alpha monoclonal antibody (mAb), while excess GRO alpha re stored the growth. The addition of rhIL-8, rhIP-10, anti-human IL-8 or anti -human ENA-78 ra;ibs did not alter HUVEC proliferation. [I-125]IL-8 binding to HUVEC was saturable and inhibited by nonradioactively iodinated IL-8, b ut not non-iodinated IL-8, [I-125]GRO alpha binding was also inhibited by i odinated IL-8. Since these data suggested specific binding sites for alpha- chemokines on HUVEC, me tested the effect of antileukinate, a potent alpha- chemokine receptor inhibitor, on [I-125]GRO alpha binding, Antileukinate in hibited GRO alpha binding and suppressed HUVEC proliferation in a dose-depe ndent manner, Antileukinate was not cytotoxic, with no decrease in cell via bility in the presence of 100 mu M antileukinate. These findings suggest th at GRO alpha is essential for HUVEC grow th factor and that antileukinate i nhibits growth by preventing autocrine GRO alpha receptor binding. This rai ses the interesting possibility of alpha-chemokine receptor inhibitors, suc h as antileukinate, in the treatment of cancer where angiogenesis is an imp ortant factor for tumour growth. (C) 1999 Academic Press.