In esophageal squamous cell carcinoma patients, high plasma lnc-POU3F3 levels are associated with resistance to chemoradiotherapy, suggesting that plasma exosomal lnc-POU3F3 expression can be used as a liquid biopsy marker predicting the prognosis of patients with esophageal squamous cell carcinoma cancer. Here, POU3F3 is linked to esophageal squamous cell carcinoma.