DKK1 and Kaposi's sarcoma: Khakoo et al demonstrated that systemically injected MSCs reduced tumor growth in a model of Kaposi’s sarcoma through the inhibition of Akt (6), Zhu et al reported that human MSCs inhibited the proliferation of K562 cells by the secretion of Dickkopf-related protein 1 (DKK-1) (7).