MAPK1 and esophageal squamous cell carcinoma: In summary, our study demonstrated that circUBE4B encoding circUBE4B-173aa ultimately promotes ESCC proliferation by interacting with MAPK1 protein and activating the MAPK/ERK pathway (Fig. 6E), which indicated that circUBE4B/circUBE4B-173aa can be used as a potential prognosis biomarker and new therapeutic targets for ESCC.