Naphthol AS-E Phosphate Inhibits the Activity of the Transcription Factor Myb by Blocking the Interaction with the KIX Domain of the Coactivator p300

Abstract

The transcription factor c-Myb is highly expressed in hematopoietic progenitor cells and controls the transcription of genes important for lineage determination, cell proliferation, and differentiation. Deregulation of c-Myb has been implicated in the development of leukemia and certain other types of human cancer. c-Myb activity is highly dependent on the interaction of the c-Myb with the KIX domain of the coactivator p300, making the disruption of this interaction a reasonable strategy for the development of Myb inhibitors. Here, we have used bacterial Autodisplay to develop an in vitro binding assay that mimics the interaction of Myb and the KIX domain of p300. We have used this binding assay to investigate the potential of Naphthol AS-E phosphate, a compound known to bind to the KIX domain, to disrupt the interaction between Myb and p300. Our data show that Naphthol AS-E phosphate interferes with the Myb-KIX interaction in vitro and inhibits Myb activity in vivo. By using several human leukemia cell lines, we demonstrate that Naphthol AS-E phosphate suppresses the expression of Myb target genes and induces myeloid differentiation and apoptosis. Our work identifies Naphthol AS-E phosphate as the first low molecular weight compound that inhibits Myb activity by disrupting its interaction with p300, and suggests that inhibition of the Myb-KIX interaction might be a useful strategy for the treatment of leukemia and other tumors caused by deregulated c-Myb.

Targeting acute myeloid leukemia with a small molecule inhibitor of the Myb/p300 interaction

“…We have recently identified another compound, Naphthol AS-E phosphate, which inhibits Myb activity in a similar manner, underscoring the "druggability" of the Myb-KIX protein-protein interaction. 46 Our data show that Celastrol inhibits the expression of bona fide Myb-regulated genes and, depending on its concentration, induces differentiation or apoptosis of HL60 cells. Interestingly, the differentiation-inducing activity of Celastrol was further increased by other compounds, such as ATRA or the broad-spectrum histone deacetylase inhibitor LBH589, which synergistically induced differentiation of HL60 cells in combination with Celastrol.…”

“…1,38,46,60 Most acute myeloid and lymphoid leukemia cells express high levels of Myb and are more dependent on, or addicted to, Myb expression than normal hematopoietic progenitor cells. 28 This has raised the possibility that inhibitors of Myb might be able to eradicate the leukemic cells while leaving normal hematopoietic progenitors unaffected.…”

“…46 Bacterial autodisplay provides a powerful experimental platform for the analysis of protein-protein interactions and the development of inhibitors.…”

“…46 Bacterial autodisplay provides a powerful experimental platform for the analysis of protein-protein interactions and the development of inhibitors. 47,48 Figure 3B shows that bacteria, which express the KIX domain on their surface, were able to bind GFP-Myb but not GFP.…”

Understanding the role of the MYB oncogene in human breast cancer: targets and functions

“…Naphthol AS-E phosphate blocks the interaction between MYB and CBP/P300 in vitro (Kasper et al, 2013, Uttarkar et al, 2015. This requires further in vivo and clinical studies.…”