Kpm/Lats2 is linked to chemosensitivity of leukemic cells through the stabilization of p73

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 pS3, 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 coexpresslon 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.