Additionally, the phagocytosis of A549 by macrophages was examined by flow cytometry in the concentration range of 0.001 nM~10 μM, and it was found that morphine concentration dependently inhibited the phagocytic effect of macrophages (EC50 (concentration producing half the efficacy) = 2.13 ± 0.16 nM, Figure 1C), which is the concentration required for morphine to activate MOR [33], indicating that direct inhibition of tumor phagocytosis by macrophages at nM levels of morphine is a possible phenomenon during clinical administration. Here, OPRM1 is linked to neoplasm.