NRAS and melanoma: Next, through the genetic ablation of cyclooxygenases (COX) in Braf(V600E) mouse melanoma cells or in N-Ras(G12D) melanoma or in breast or colorectal cancer cells, they demonstrated that those cells, with COX expression deleted and hence the biosynthesis of prostaglandins abolished, could not grow well in the immune-competent mice but that they grow equally well in the immunocompromised mice [14].