SP1 and esophageal squamous cell carcinoma: Among 108 ESCC patients with tumor metastasis, 68 patients (62.9%) had high expression of HIF-1α, 69 patients (63.9%) had high expression of SP1; while among 74 patients without tumor metastasis, 34 patients (45.9%) were with high expression of HIF-1α and 27 patients (36.5%) had high expression of SP1 (Figure 4f).