SOX2 and esophageal squamous cell carcinoma: More importantly, we analyzed the correlation index of CDP and SOX2 proteins after the combination analysis of their expression levels in these ESCC clinical samples [25], and we found that correlation index of these two proteins reached 1 in 72% of cytoplasm and 69.3% of nucleus in clinical samples, and more clinical samples with correlation index at 1 occurred in the advanced stage of ESCC, such as stage II, II-III and III (Fig. 1F).