PTGS2 and neoplasm: Another experiment showed that RAs can inhibit the activation of activator protein-1 (AP-1) and NF-κB and downregulate the expression of cyclooxygenase-2 (COX-2) and TNF by suppressing the expression of key transcription factors and proteins, thereby inhibiting the proliferation, invasion, metastasis, and angiogenesis of tumor cells [76].