The inhibitory effect of RCE on PD-1/PD-L1 interaction was further supported by in vivo data using a humanized PD-L1 knock-in MC38 tumor-bearing animal model, in which oral administration of RCE (50 and 100 mg/kg/day) exhibited tumor inhibition rates of 66.94% and 73.81%, respectively, on day 21. Here, PDCD1 is linked to neoplasm.