A small-molecule inhibitor of the aberrant transcription factor CBFβ-SMMHC delays leukemia in mice

This is the author’s version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science on 2015 February 13; 347(6223): 779–784, DOI: 10.1126/science.aaa0314.Acute myeloid leukemia (AML) is the most common form of adult leukemia. The transcription factor fusion CBFβ-SMMHC (core binding factor β and the smooth-muscle myosin heavy chain), expressed in AML with the chromosome inversion inv(16)(p13q22), outcompetes wild-type CBFβ for binding to the transcription factor RUNX1, deregulates RUNX1 activity in hematopoiesis, and induces AML. Current inv(16) AML treatment with nonselective cytotoxic chemotherapy results in a good initial response but limited long-term survival. Here, we report the development of a protein-protein interaction inhibitor, AI-10-49, that selectively binds to CBFβ-SMMHC and disrupts its binding to RUNX1. AI-10-49 restores RUNX1 transcriptional activity, displays favorable pharmacokinetics, and delays leukemia progression in mice. Treatment of primary inv(16) AML patient blasts with AI-10-49 triggers selective cell death. These data suggest that direct inhibition of the oncogenic CBFβ-SMMHC fusion protein may be an effective therapeutic approach for inv(16) AML, and they provide support for transcription factor targeted therapy in other cancers

One Bit Is Enough: a Framework for Deploying Explicit Feedback Congestion Control Protocols

In this paper we describe UNO, a framework for finegrain explicit feedback congestion control protocols that uses only 1 or 2 existing ECN bits, thus making algorithms that use more than 2 bits for encoding the load factor and the RTT immediately deployable. UNO accomplishes this task by changing the way load and RTT information is encoded in packets in a way that is similar to some existing schemes for encoding bottleneck link load. UNO leverages the values present in the IP identification field and trades-off a small amount of time (to send several packets) for space to emulate the existence of several extra bits within the IP header. The results from extensive ns2 simulations over various bandwidth and delay scenarios are encouraging. By using only one ECN bit we achieve substantially lower convergence times and better link utilization than the existing deployable protocols, with similar low queue size and negligible packet loss. With 2 ECN bits, we achieve very good fairness for flows with different RTTs, while keeping all the good characteristics of the 1-bit protocol and providing functionality that did not previously exist. I

Analysis of the Crack Initiation and Growth in Crystalline Materials Using Discrete Dislocations and the Modified Kitagawa–Takahashi Diagram

Crack growth kinetics in crystalline materials is examined both from the point of continuum mechanics and discrete dislocation dynamics. Kinetics ranging from the Griffith crack to continuous elastic-plastic cracks are analyzed. Initiation and propagation of incipient cracks require very high stresses and appropriate stress gradients. These can be obtained either by pre-existing notches, as is done in a typical American Society of Testing and Materials (ASTM) fatigue and fracture tests, or by in situ generated stress concentrations via dislocation pile-ups. Crack growth kinetics are also examined using the modified Kitagawa–Takahashi diagram to show the role of internal stresses and their gradients needed to sustain continuous crack growth. Incipient crack initiation and growth are also examined using discrete dislocation modeling. The analysis is supported by the experimental data available in the literature

Degree of Recruitment of DOT1L to MLL-AF9 Defines Level of H3K79 Di- and Tri-methylation on Target Genes and Transformation Potential

The MLL gene is a common target of chromosomal translocations found in human leukemia. MLL-fusion leukemia has a consistently poor outcome. One of the most common translocation partners is AF9 (MLLT3). MLL-AF9 recruits DOT1L, a histone 3 lysine 79 methyltransferase (H3K79me1/me2/me3), leading to aberrant gene transcription. We show that DOT1L has three AF9 binding sites and present the nuclear magnetic resonance (NMR) solution structure of a DOT1L-AF9 complex. We generate structure-guided point mutations and find that they have graded effects on recruitment of DOT1L to MLL-AF9. Chromatin immunoprecipitation sequencing (ChIP-seq) analyses of H3K79me2 and H3K79me3 show that graded reduction of the DOT1L interaction with MLL-AF9 results in differential loss of H3K79me2 and me3 at MLL-AF9 target genes. Furthermore, the degree of DOT1L recruitment is linked to the level of MLL-AF9 hematopoietic transformation

Chemical biology. A small-molecule inhibitor of the aberrant transcription factor CBFbeta-SMMHC delays leukemia in mice

Acute myeloid leukemia (AML) is the most common form of adult leukemia. The transcription factor fusion CBFbeta-SMMHC (core binding factor beta and the smooth-muscle myosin heavy chain), expressed in AML with the chromosome inversion inv(16)(p13q22), outcompetes wild-type CBFbeta for binding to the transcription factor RUNX1, deregulates RUNX1 activity in hematopoiesis, and induces AML. Current inv(16) AML treatment with nonselective cytotoxic chemotherapy results in a good initial response but limited long-term survival. Here, we report the development of a protein-protein interaction inhibitor, AI-10-49, that selectively binds to CBFbeta-SMMHC and disrupts its binding to RUNX1. AI-10-49 restores RUNX1 transcriptional activity, displays favorable pharmacokinetics, and delays leukemia progression in mice. Treatment of primary inv(16) AML patient blasts with AI-10-49 triggers selective cell death. These data suggest that direct inhibition of the oncogenic CBFbeta-SMMHC fusion protein may be an effective therapeutic approach for inv(16) AML, and they provide support for transcription factor targeted therapy in other cancers

Small Molecule Inhibitor of CBFβ-RUNX Binding for RUNX Transcription Factor Driven Cancers

Transcription factors have traditionally been viewed with skepticism as viable drug targets, but they offer the potential for completely novel mechanisms of action that could more effectively address the stem cell like properties, such as self-renewal and chemo-resistance, that lead to the failure of traditional chemotherapy approaches. Core binding factor is a heterodimeric transcription factor comprised of one of 3 RUNX proteins (RUNX1-3) and a CBFβ binding partner. CBFβ enhances DNA binding of RUNX subunits by relieving auto-inhibition. Both RUNX1 and CBFβ are frequently mutated in human leukemia. More recently, RUNX proteins have been shown to be key players in epithelial cancers, suggesting the targeting of this pathway could have broad utility. In order to test this, we developed small molecules which bind to CBFβ and inhibit its binding to RUNX. Treatment with these inhibitors reduces binding of RUNX1 to target genes, alters the expression of RUNX1 target genes, and impacts cell survival and differentiation. These inhibitors show efficacy against leukemia cells as well as basal-like (triple-negative) breast cancer cells. These inhibitors provide effective tools to probe the utility of targeting RUNX transcription factor function in other cancers