CD274 and breast cancer: Ubiquitinspecific peptidase 9, X-linked (USP9X) was shown to directly deubiquitinate PD-L1 in oral squamous cell carcinoma [106]; moreover, CSN5 facilitates PD-L1 deubiquitination to enhance its stability in several malignancies, such as BC and GC [33, 107, 108], suggesting that targeting CSN5 might be globally effective across multiple tumors.