USP28 and cancer: To investigate whether the combinatorial treatment of USP28 inhibition and targeted kinase inhibitor therapy is also suitable for genetically complex cancer cells, next, we co‐cultured the BRAF mutant human cancer cell lines A375 and HT‐29, the EGFR mutant cell lines H1650 and A431, and the PIK3CA mutant lines HT‐29 and CaSki in the presence of the respective inhibitors at increasing concentrations for 72 h (Fig. S8G).