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Blood, 1 November 2008, Vol. 112, No. 9, pp. 3856-3866. Prepublished online as a Blood First Edition Paper on June 18, 2008; DOI 10.1182/blood-2007-09-111773.
NEOPLASIA Kpm/Lats2 is linked to chemosensitivity of leukemic cells through the stabilization of p731 Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; 2 Laboratory of Signal Transduction and Proteomic Profiling, Weis Center for Research, Danville, PA; and 3 Department of Medicine, Mount Sinai School of Medicine, New York, NY Down-regulation of the Kpm/Lats2 tumor suppressor is observed in various malignancies and associated with poor prognosis in acute lymphoblastic leukemia. We documented that Kpm/Lats2 was markedly decreased in several leukemias that were highly resistant to conventional chemotherapy. Silencing of Kpm/Lats2 expression in leukemic cells did not change the rate of cell growth but rendered the cells more resistant to DNA damage–inducing agents. Expression of p21 and PUMA was strongly induced by these agents in control cells, despite defective p53, but was only slightly induced in Kpm/Lats2-knockdown cells. DNA damage–induced nuclear accumulation of p73 was clearly observed in control cells but hardly detected in Kpm/Lats2-knockdown cells. Chromatin immunoprecipitation (ChIP) assay showed that p73 was recruited to the PUMA gene promoter in control cells but not in Kpm/Lats2-knockdown cells after DNA damage. The analyses with transient coexpression of Kpm/Lats2, YAP2, and p73 showed that Kpm/Lats2 contributed the stability of YAP2 and p73, which was dependent on the kinase function of Kpm/Lats2 and YAP2 phosphorylation at serine 127. Our results suggest that Kpm/Lats2 is involved in the fate of p73 through the phosphorylation of YAP2 by Kpm/Lats2 and the induction of p73 target genes that underlie chemosensitivity of leukemic cells.
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