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Neoplasia. 2015 May;17(5):449-62. doi: 10.1016/j.neo.2015.04.005.

STAT1: A Novel Target of miR-150 and miR-223 Is Involved in the Proliferation of HTLV-I-Transformed and ATL Cells.

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Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA.
Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA. Electronic address:


We have previously reported on the deregulation of cellular microRNAs involved in hematopoiesis and inflammation in human T-cell lymphotropic virus type 1 (HTLV-I)-transformed cells. In this study, we demonstrate that miR-150 and miR-223 specifically target the signal transducer and activator of transcription 1 (STAT1) 3' untranslated region, reducing STAT1 expression and dampening STAT1-dependent signaling in human T cells. The effects of miR-150 and miR-223 on endogenous STAT1 were confirmed using inducible cell lines. Our studies also showed that miR-150 expression is upregulated by interleukin-2 signaling in adult T cell leukemia/lymphoma (ATL) cells. HTLV-I-transformed and ATL-derived cells have reduced levels of miR150 and miR223 expression, which coincide with increased STAT1 expression and STAT1-dependent signaling. Knockdown of STAT1 by short hairpin RNA demonstrated that the constitutive activation of STAT1 is required for the continuous proliferation of HTLV-I-transformed cells. Our studies further demonstrate that increased expression of STAT1 in ATL cells is associated with higher levels of major histocompatibility complex class I expression. Previous studies have demonstrated that the pressure exerted by natural killer (NK) cells in vivo can edit leukemic tumor cells by forcing an increased expression of major histocompatibility complex class I to escape immune clearance. STAT1-expressing tumor cells produce more aggressive tumors because they cannot be eliminated by NK cells. Our results suggest that therapeutic approaches using combined targeting of STAT1 and MHC class I may be an effective approach to activate NK cell-mediated clearance of ATL tumor cells.

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