The antileukemic effect of inhibiting bromodomain and extra-terminal domain-containing (BET-containing) proteins (BETPs) such as BRD4 has largely been largely attributed to transcriptional downregulation of cellular anabolic and antiapoptotic processes, but its effect on the bone marrow microenvironment, a sanctuary favoring the persistence of leukemic stem/progenitor cells, is unexplored. Sustained degradation of BETP with the small-molecule BET proteolysis-targeting chimera (PROTAC) ARV-825 resulted in a marked downregulation of surface CXCR4 and CD44, key proteins in leukemia-microenvironment interactions, in acute myeloid leukemia (AML) cells. Abrogation of surface CXCR4 expression impaired SDF-1α–directed migration and was mediated through transcriptional downregulation of PIM1 kinase, which in turn phosphorylates CXCR4 and facilitates its surface localization. Downregulation of CD44, including isoforms CD44v8–10 impaired cystine uptake, lowered intracellular reduced glutathione, and increased oxidative stress. More important, BETP degradation markedly decreased the CD34+CD38–CD90–CD45RA+ leukemic stem cell population and, alone or in combination with cytarabine, prolonged survival in a mouse model of human leukemia that included AML patient-derived xenografts (AML-PDX). Gene expression profiling and single-cell proteomics confirmed a downregulation of the gene signatures associated with “stemness” in AML and Wnt/β-catenin and Myc pathways. Hence, BETP degradation by ARV-825 simultaneously targets cell-intrinsic signaling, stromal interactions, and metabolism in AML.
Sujan Piya, Hong Mu, Seemana Bhattacharya, Philip L. Lorenzi, R. Eric Davis, Teresa McQueen, Vivian Ruvolo, Natalia Baran, Zhiqiang Wang, Yimin Qian, Craig M. Crews, Marina Konopleva, Jo Ishizawa, M. James You, Hagop Kantarjian, Michael Andreeff, Gautam Borthakur
Usage data is cumulative from October 2019 through October 2020.
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.