Data obtained from the GEPIA database and immunohistochemical results showed that RRM1 expression in most ESCC tissues was abnormally higher than that in adjacent tissues (Fig. S1; Fig. 1A, B), and a significantly negative correlation between the RRM1 expression and survival time was observed, and patients with high RRM1 expression exhibited a worse prognosis (Fig. 1C), suggesting that RRM1 could be used as an indicator for early diagnosis, a potential predictor to estimate patients' survival or a potential target of antitumor drugs. This evidence concerns the gene RRM1 and esophageal squamous cell carcinoma.