USP9X and neoplasm: We examined the expression and function of USP9X and PD‐L1 in human oral keratinocytes (HOK) and OSCC cell lines (HN4 and HN30) as the control and relevant cancer cells using western blotting, immunoprecipitation, immunohistochemistry (IHC), T‐cell‐mediated tumor cell killing assay, and liquid chromatography‐mass spectrometry.