Taken together with the reports that IL-11 binds to its receptors on osteoclasts or their precursors to regulate the formation and function of osteoclasts54,55, these findings suggest that the Ac-KLF5/CXCR4 axis in tumor cells induces osteoclast differentiation by increasing IL-11 secretion. The gene discussed is KLF5; the disease is neoplasm.