Esophageal cancer (EC) is a prevalent malignancy associated with therapeutic resistance and poor prognosis. This study investigates the role of programmed death-ligand 1 (PD-L1) in esophageal cancer stem cell (ECSC) formation. ECSCs were enriched and characterized using various assays. We found that both PD-L1 and bromodomain-containing protein 4 (BRD4) were upregulated in ECSCs, promoting their stemness. Inhibiting BRD4 suppressed ECSC markers expression and sphere formation. Furthermore, BRD4 inhibitors downregulated membrane and nuclear PD-L1 levels, with knockdown of PD-L1 inhibiting ECSC formation. PD-L1 degraders also affected PD-L1 and its downstream effector RelB expression. Moreover, inhibiting RelB influenced sphere formation through interleukin-6 expression. This study reveals the critical role of the BRD4/nuclear PD-L1/RelB axis in ECSC formation, highlighting nuclear PD-L1 as a potential immunotherapeutic target for refractory EC.
Keywords: RelB; bromodomain-containing protein 4; cancer stem cell; esophageal cancer; programmed death-ligand 1; stemness.
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