AXL and melanoma: They also revealed that COX inhibitors enhance the efficacy of anti‐PD‐1 immunotherapy.[123] The AXL receptor tyrosine kinase (AXL), a downstream product of PGE2, its high expression is implicated in drug resistance, EMT, and enhanced survival of melanoma stem cells.[124, 125, 126] Moreover, NSAIDs have been shown to downregulate PKA activity via the PGE2/EP2/cAMP/PKA signaling pathway.