Figure 3b shows that with the depletion of UBR1 proteins, RFC11 entrapped in biotinylated liposome could not enhance the therapeutic efficacy of shikonin. However, usual drug synergism was observed in siRNA-untreated and scrambled siRNA-treated cells. Clearly, UBR1’s presence is required for the RFC11-assisted enhanced cytotoxicity in cancer cells. The depletion of UBR1 protein by siRNA was confirmed by western blot analysis as shown in Figure 3c. Here, UBR1 is linked to cancer.