HMBOX1 and esophageal squamous cell carcinoma: To confirm whether circCD44 targets the METTL3/HMBOX1 axis to promote ESCC progression in vitro, we examined phenotypic changes of ESCC cells transfected with OE‐circCD44, OE‐circCD44 + si‐METTL3, or OE‐circCD44 + si‐HMBOX1.