Tabe et al (2006) demonstrated in this context that the HDAC-inhibitor FK228 induces P-gp expression and prevents growth inhibition and apoptosis in acute promyelocytic leukaemia cells subsequently incubated with DOX. Okada et al (2006) observed resistance development in DOX-resistant clones of osteosarcoma and Ewing's family of tumours after exposure to FK228. Here, HDAC9 is linked to osteosarcoma.