To confirm that cordycepin can effectively affect the proliferation and apoptosis of breast cancer, we first measured the effect of cordycepin on the expression of proliferation-related proteins (cyclin D, PCNA, and Ki67) and apoptosis-related proteins (Bcl-2, Bax, and caspase-3) in tumor tissues by immunohistochemistry and Western blot analysis (Figure 2). This evidence concerns the gene PCNA and breast cancer.