YWHAZ-Mediated Modulation of Tumor Differentiation Impact on the Long-Term Prognosis in Esophageal Squamous Cell Carcinoma Patients Following Chemoradiotherapy

Abstract Objective To investigate the correlation between the expression of tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ) in esophageal squamous cell carcinoma (ESCC) tissues and tumor progression, and to analyze the mediating effect of YWHAZ on the association between the degree of tumor differentiation and prognosis in esophageal cancer patients. Method Expression of YWHAZ gene between 33 cancers and normal, overall survival (OS) between groups with low YWHAZ expression and high YWHAZ expression were analyzed by bioinformatic analysis with TCGA-GTEx dataset, comparison of YWHAZ expression between esophageal cancer (ESCA) and normal subjects, correlations between expression of YWHAZ and different cancer stages, survival in patients with ESCA were analyzed by bioinformatic analysis with TCGA-ESCA dataset. Then an immunohistochemical assay was used to detect the expression rate of YWHAZ in 75 cases with ESCC after chemoradiotherapy. Correlation between the expression of YWHAZ and tumor progression, including OS and progression-free survival (PFS), were analyzed using the rank sum test or chi-square test. Cox regression, general linear model (GLM) and mediation analyses were used to analyze the effect of YWHAZ expression on the long-term prognosis of ESCC patients. Results Bioinformatic analysis with TCGA-GTEx dataset found expression levels of YWHAZ in BRCA, CESC, COAD, LIHC, LUAD, LUSC, OV, PAAD, READ, STAD, THYM were higher than those in normal subjects (P < 0.05). OS in KIRP, LGG, LIHC, LUAD, PAAD and UVM with high expression of YWHAZ were shorter than those with low expression of YWHAZ(P < 0.05-0.0005), while it was longer in KIRC with high expression of YWHAZ than that with low expression of YWHAZ(P = 0.048). Expression level of YWHAZ was higher in ESCA than that in normal subjects in TCGA data (P < 0.0001), and it was higher in ESCC than that in esophageal adenocarcinoma (P < 0.0001). It was higher in Asian ESCA patients than that in Caucasian and Africa-american ESCA patients (P < 0.0001). There were no differences about expression level of YWHAZ among different cancer stages (P > 0.05). OS and PFS of ESCA in patients with low expression of YWHAZ were the same as patients with high expression of YWHAZ (P > 0.05), but effect of YWHAZ expression level interacted with tumor grade on ESCA patients survival differed from each other (P = 0.023). The expression rate of YWHAZ in carcinoma tissues with ESCC (0.59 vs 0.49) was significantly higher than that in anastomotic stomas (z = 2.692, P = 0.007). High expression of YWHAZ was a risk factor for long-term recurrence/disease progression (HR = 3.166, 95% CI: 1.623–6.176, P = 0.001) and death (HR = 6.321, 95% CI: 2.925–13.658, P < 0.001) in patients. GLM analysis found expression of YWHAZ interacted with tumor differentiation grade negatively correlated with OS in ESCC (B=-6.058, 95%CI:-9.233~-2.893, x² = 14.076, P < 0.001). YWHAZ expression served as a mediator of the association between the grade of tumor differentiation and OS or PFS in ESCC patients (P < 0.0001). The indirect effect (mediating role) of YWHAZ expression accounted for 62.15% of the total effect of the grade of tumor differentiation on OS, and accounted for 47.39% of the total effect of the grade of tumor differentiation on PFS. Conclusion High expression of YWHAZ, which mediates the grade of tumor differentiation, is a risk factor for long-term recurrence/disease progression and death in patients with ESCC after chemoradiotherapy.