BRAF and melanoma: Despite the presence of  approximately 30% CXCR2 positive melanoma cells in Braf/Pten/Cxcr2−/− tumors, we observed that tumor burden and incidence (Fig. 2A) were significantly reduced in mice with Braf/Pten/Cxcr2−/− tumors (271 ± 361mm3, n = 21) compared to mice with Braf/Pten/Cxcr2WT tumors (615 ± 609mm3, n = 24, p < 0.05) 36 days after 4HT administration.