To examine the clinical relevance of the KLF4‐PARP1 axis to breast cancer development, we have measured the protein expression levels of KLF4 and PARP1 in various types of breast cancer cells as well as human breast tumor tissue specimens in comparison with adjacent normal tissues, by using Western blotting and immunohistochemistry (IHC). The gene discussed is KLF4; the disease is breast neoplasm.