Inhibition of GROα-induced human endothelial cell proliferation by the α-chemokine inhibitor antileukinate

GRO alpha, an autocrine mitogenic factor for melanoma cell lines, belongs to the superfamily of alpha-chemokines. Here, we report that GRO alpha stimulates the growth of human umbilical vein endothelial cells (HUVEC) in vitro, with proliferation being significantly stimulated by 100 nM recombinant human (rh) GRO alpha, Proliferation was significantly inhibited by 100 mu g/ml antihuman GRO alpha monoclonal antibody (mAb), while excess GRO alpha restored 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, but not non-iodinated IL-8, [I-125]GRO alpha binding was also inhibited by iodinated 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 inhibited GRO alpha binding and suppressed HUVEC proliferation in a dose-dependent manner, Antileukinate was not cytotoxic, with no decrease in cell viability in the presence of 100 mu M antileukinate. These findings suggest that GRO alpha is essential for HUVEC grow th factor and that antileukinate inhibits growth by preventing autocrine GRO alpha receptor binding. This raises the interesting possibility of alpha-chemokine receptor inhibitors, such as antileukinate, in the treatment of cancer where angiogenesis is an important factor for tumour growth. (C) 1999 Academic Press.