{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T15:02:24Z","timestamp":1785423744647,"version":"3.56.0"},"posted":{"date-parts":[[2026,7,15]]},"group-title":"Cancer Biology","reference-count":70,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T00:00:00Z","timestamp":1784073600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"award":["PO1 HL146372"],"award-info":[{"award-number":["PO1 HL146372"]}],"id":[{"id":"https:\/\/ror.org\/012pb6c26","id-type":"ROR","asserted-by":"publisher"}]},{"name":"National Cancer Institute","award":["RO1 CA204373"],"award-info":[{"award-number":["RO1 CA204373"]}]},{"name":"National Cancer Institute","award":["R21 CA263430"],"award-info":[{"award-number":["R21 CA263430"]}]},{"name":"National Cancer Institute","award":["P30 CA043703"],"award-info":[{"award-number":["P30 CA043703"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,7,15]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  Internal-tandem-duplication of the receptor tyrosine kinase\n                  <jats:italic>FLT3<\/jats:italic>\n                  (\n                  <jats:italic>FLT3-ITD<\/jats:italic>\n                  ) generates ligand-independent signaling and is highly recurrent in acute myeloid leukemias (AMLs). One way signaling pathways can quickly influence cell fates is by phosphorylating key fate-determining proteins to trigger their proteolysis. We investigated the master transcription factor (MTF) driver of granulo-monocytic lineage-fates, CEBPA, for regulation by this mechanism because we found high CEBPA mRNA but little CEBPA protein in\n                  <jats:italic>FLT3-ITD<\/jats:italic>\n                  versus\n                  <jats:italic>FLT3<\/jats:italic>\n                  -wildtype AML cells, and inhibiting FLT3-ITD signaling with tyrosine kinase inhibitors (TKI) rapidly rescued CEBPA protein. Mass spectrometry analyses of CEBPA and its interactome demonstrated prominent interactions with major ubiquitin-proteosome pathway (UPP) components UHRF1 and USP7. TKI treatments decreased CEBPA and USP7 phosphorylations at serine 21 and serine 18 respectively alongside shifts in CEBPA interactions from degradative ubiquitin-ligase UHRF1 toward protective deubiquitinase USP7. The rescued CEBPA activated granulocytic-differentiation. Supporting that the serine-phosphorylations were \u2018phospho-degrons\u2019, UPP-inhibitors (bortezomib, MG132) increased phosphorylated and total CEBPA and USP7. The MTF regulator of apoptosis p53 is a known USP7 client, therefore, we also evaluated p53 status: TKIs and UPP-inhibitors stabilized USP7 and p53, triggering apoptosis in addition to granulocytic-differentiation specifically in\n                  <jats:italic>FLT3-ITD<\/jats:italic>\n                  but not\n                  <jats:italic>FLT3<\/jats:italic>\n                  -wildtype AML cells. UPP-inhibitors produced these consequences in TKI-resistant\n                  <jats:italic>FLT3-ITD<\/jats:italic>\n                  AML cells also. These data predicted genetic loss-of-function to\n                  <jats:italic>CEBPA<\/jats:italic>\n                  or\n                  <jats:italic>TP53<\/jats:italic>\n                  is redundant in the\n                  <jats:italic>FLT3-ITD<\/jats:italic>\n                  context, borne out by mutual exclusivity of the mutations in clinical series. In summary, FLT3-ITD signals for CEBPA and p53 proteolysis to block lineage-maturation and apoptosis, positioning UPP-inhibitors as therapeutic candidates acting downstream of TKIs.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>KEY POINTS<\/jats:title>\n                  <jats:list list-type=\"bullet\">\n                    <jats:list-item>\n                      <jats:p>The oncoprotein kinase FLT3-ITD signals for CEBPA and p53 proteolysis and hence suppresses lineage-differentiation and apoptosis<\/jats:p>\n                    <\/jats:list-item>\n                    <jats:list-item>\n                      <jats:p>Proteosome-inhibitors are candidate remedies to restore CEBPA and p53, acting downstream of presently used FLT3-ITD kinase inhibitors<\/jats:p>\n                    <\/jats:list-item>\n                  <\/jats:list>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>GRAPHICAL ABSTRACT<\/jats:title>\n                  <jats:fig id=\"ufig1\" position=\"float\" orientation=\"portrait\" fig-type=\"figure\">\n                    <jats:graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"738455v1_ufig1\" position=\"float\" orientation=\"portrait\"\/>\n                  <\/jats:fig>\n                <\/jats:sec>","DOI":"10.64898\/2026.07.14.738455","type":"posted-content","created":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T11:50:13Z","timestamp":1784116213000},"source":"Crossref","is-referenced-by-count":0,"title":["FLT3-ITD signals for CEBPA and p53 proteolysis by the ubiquitin-proteosome pathway"],"prefix":"10.64898","author":[{"given":"Xiaorong","family":"Gu","sequence":"first","affiliation":[{"name":"Department of Translational Hematology and Oncology Research, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH 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