PD-L1-positive exosomes in mouse models enhanced tumor growth and suppressed antitumor immunity, while knockout of PD-L1 on exosomes led to reduced tumor growth and amplified immune responses [43]. The significance of exosomal PD-L1 is further illustrated in OSCC, where endoplasmic reticulum (ER) stress, which is a disturbance in the ER environment caused by factors such as nutrient deprivation, oxidative stress, or DNA damage, activates the unfolded protein response (UPR) [45,46]. Here, CD274 is linked to neoplasm.