We investigated how XMU-MP-1, the inhibitor of the serine/threonine kinases MST1/2, the key components of the Hippo pathway, affects hematopoietic tumors and demonstrated that the treatment of several hematopoietic tumor cell lines with XMU-MP-1 causes suppression of their growth and induces programmed cell death. The gene discussed is MST1; the disease is hematopoietic and lymphoid cell neoplasm.