ESR1 and esophageal squamous cell carcinoma: Correlation among 16 biological factors [p53, p21waf1, MIB-1 (Ki-67), p16INK4A, cyclin D1, E-cadherin, Bcl-2, TNF-α, NF-κB, TGF-β, MMP-7, COX-2, EGFR, HER2/neu, ER, and HIF-1α] and clinical outcomes following curative chemoradiation therapy in 10 patients with esophageal squamous cell carcinoma