As shown in Figure 3(A), GRP78 protein was highly expressed in MDA-MB-231 cells, but with little evidence of expression in L929 cells, indicating that GRP78 could be a binding site for l-CS-g-PNIPAM NPs in breast tumor therapy and that the l-peptide was able to perform its active targeting properties through interaction with GRP78. Here, HSPA5 is linked to breast neoplasm.