PTGS2 and cancer: However the expression of TREM-1 protein was abrogated in macrophages transfected with COX-2 siRNA that were co-cultured with cancer cells (A549, H23 or H838 cells) (Figure 5B, 5C). Expression of TREM-1 message was also abrogated in macrophages that were treated with siCOX-2 and co-cultured with tumor cells (Figure 5D).