Induction of osteoclastogenesis by Ac-KLF5-expressing tumor cells also indicates that Ac-KLF5 activates paracrine signaling in tumor cells to mediate tumor cells’ interaction with osteoclasts or osteoblasts, which also provides a mechanism for how Ac-KLF5 causes bone metastatic lesions. The gene discussed is KLF5; the disease is neoplasm.