CD274 and melanoma: For example, HDACi can increase the levels of PD-1 ligands in melanoma, thereby enhancing the immunotherapeutic effects of PD-1 blockers.610 Moreover, HDACi can upregulate PD-L1 mRNA and protein expression in a time-dependent manner in TNBC cells and significantly enhance the in vivo response to PD-1/CTLA-4 blockade in the triple-negative 4T1 breast cancer mouse model.610 HDACi enhance the immunotherapy effect in TNBC by regulating tumor growth.