There have been a few studies of the biological activity of this cytokine; for instance, Yokoe et al. [32] measured serum IL-8 in 12 heavily pretreated patients with recurrent breast cancer, and reported that IL-8 levels were higher in patients with refractory progressive disease but were almost unchanged in patients showing a partial response or no change after systemic therapy. Here, CXCL8 is linked to breast cancer.