CXCR1 and breast cancer: Also, small molecule inhibitors for the CXCR1/CXCR2 receptors are already in clinical trials for liver metastasis in colon cancer (Varney et al. 2011), breast cancer (Campbell et al. 2013), and other indications (Citro et al. 2012; Holz et al. 2010; Moss et al. 2013; Nair et al. 2012).