Böttcher et al. addressed this question using a melanoma tumor model previously reported to exclude T cells and CD103+ DC through the upregulation of cyclooxygenase enzymes COX-1 and COX-2 (encoded by ptgs1 and ptgs2) and their catalytic product, prostaglandin E2 (PGE2) [6]. The gene discussed is PTGS1; the disease is melanoma.