Direct inhibition of the NOTCH transcription factor complex.

Direct inhibition of transcription factor complexes remains a central challenge in the discipline of ligand discovery. In general, these proteins lack surface involutions suitable for high-affinity binding by small molecules. Here we report the design of synthetic, cell-permeable, stabilized alpha-helical peptides that target a critical protein-protein interface in the NOTCH transactivation complex. We demonstrate that direct, high-affinity binding of the hydrocarbon-stapled peptide SAHM1 prevents assembly of the active transcriptional complex. Inappropriate NOTCH activation is directly implicated in the pathogenesis of several disease states, including T-cell acute lymphoblastic leukaemia (T-ALL). The treatment of leukaemic cells with SAHM1 results in genome-wide suppression of NOTCH-activated genes. Direct antagonism of the NOTCH transcriptional program causes potent, NOTCH-specific anti-proliferative effects in cultured cells and in a mouse model of NOTCH1-driven T-ALL.

Vascular endothelial growth factor C is increased in endometrium and promotes endothelial functions, vascular permeability and angiogenesis and growth of endometriosis.

Endometriosis is an angiogenesis-dependent disease. Many studies demonstrated inhibition of angiogenesis leads to inhibition of endometriotic growth, however underlying mechanism is still not fully understood. Our previous study suggested vascular endothelial growth factor C (VEGF-C) as a target of anti-angiogenesis therapy for endometriosis. In this study, VEGF-C in endometrium and its role in angiogenesis of endometriosis were studied. Human endometrium were obtained from women with and without endometriosis for molecular studies. VEGF-A, VEGF-B, VEGF-C and VEGF-D mRNA and proteins in eutopic and ectopic endometrium were measured. Human endothelial cells were transfected with VEGF-C siRNA in vitro, effects of VEGF-C on endothelial cell migration, invasion and tube formation were investigated in vitro. Angiogenesis was inhibited in wild type mice, vascular permeability in dermal skin was determined in vivo. Transplanted endometrium were inhibited by VEGF-C siRNA in immunocompromised mice, development, growth and angiogenesis of the experimental endometriosis were compared in vivo. The results showed that VEGF-C mRNA and protein were increased in eutopic and ectopic endometrium of endometriosis patients. VEGF-C siRNA significantly inhibited endothelial cell migration and tube formation. VEGF-C siRNA significantly inhibited development and angiogenesis of the experimental endometriotic lesions in mice. Supplementation and over-expression of VEGF-C significantly reversed the inhibitory effects on the endothelial functions, vascular permeability and endometriotic growth. In conclusion, VEGF-C is increased in endometrium and it promotes endothelial functions, vascular permeability and development of experimental endometriosis. VEGF-C is important for angiogenesis in endometriosis.

Systematic in vivo structure-function analysis of p300 in hematopoiesis.

Cyclic adenosine monophosphate response element binding (CREB)-binding protein (CBP) and p300 are multidomain transcriptional coactivators that help assemble large regulatory complexes at sites of active transcription. Nullizygosity of CBP or p300 results in pervasive defects in hematopoiesis. To systematically assess the structural domains of p300 required for normal hematopoiesis, we used recombinase-mediated cassette exchange to create an allelic series of coisogenic embryonic stem cells, each expressing a different mutant of p300 from the endogenous locus. We found that deletion of either the KIX or CH1 domain caused profound and pervasive defects in hematopoiesis, whereas the loss of most other domains had only lineage-restricted effects. When expressed from the p300 locus, an extra copy of CBP largely compensated for a lack of p300. Surprisingly, mutation of the p300 histone acetyltransferase (HAT) domain had minimal effects on hematopoiesis, and actually increased progenitor and stem cell numbers and proliferative potential. Our results suggest that, in distinct contrast to other organ systems, HAT activity does not provide a critical function for hematopoietic development and emphasizes the importance of enzyme-independent functions of p300.

HOXA9 is required for survival in human MLL-rearranged acute leukemias.

Leukemias that harbor translocations involving the mixed lineage leukemia gene (MLL) possess unique biologic characteristics and often have an unfavorable prognosis. Gene expression analyses demonstrate a distinct profile for MLL-rearranged leukemias with consistent high-level expression of select Homeobox genes, including HOXA9. Here, we investigated the effects of HOXA9 suppression in MLL-rearranged and MLL-germline leukemias using RNA interference. Gene expression profiling after HOXA9 suppression demonstrated co-down-regulation of a program highly expressed in human MLL-AML and murine MLL-leukemia stem cells, including HOXA10, MEIS1, PBX3, and MEF2C. We demonstrate that HOXA9 depletion in 17 human AML/ALL cell lines (7 MLL-rearranged, 10 MLL-germline) induces proliferation arrest and apoptosis specifically in MLL-rearranged cells (P = .007). Similarly, assessment of primary AMLs demonstrated that HOXA9 suppression induces apoptosis to a greater extent in MLL-rearranged samples (P = .01). Moreover, mice transplanted with HOXA9-depleted t(4;11) SEMK2 cells revealed a significantly lower leukemia burden, thus identifying a role for HOXA9 in leukemia survival in vivo. Our data indicate an important role for HOXA9 in human MLL-rearranged leukemias and suggest that targeting HOXA9 or downstream programs may be a novel therapeutic option.

Green tea epigallocatechin-3-gallate inhibits angiogenesis and suppresses vascular endothelial growth factor C/vascular endothelial growth factor receptor 2 expression and signaling in experimental endometriosis in vivo.

OBJECTIVE: To investigate the antiangiogenesis mechanism of epigallocatechin-3-gallate (EGCG) in an endometriosis model in vivo. DESIGN: Animal studies. SETTING: University laboratory. ANIMAL(S): Human endometrium from women with endometriosis (n = 10) was transplanted into immunocompromised mice. INTERVENTION(S): Mice (n = 30) were randomly treated with EGCG, vitamin E (antioxidant control), or vehicle (negative control) for microvessel imaging. MAIN OUTCOME MEASURE(S): Endometriotic implants were collected for angiogenesis microarray and pathway analysis. Differentially expressed angiogenesis molecules were confirmed by quantitative polymerase chain reaction, Western blot, and immunohistochemistry. Effects of EGCG on angiogenesis signal transduction were further characterized in a human endothelial cell line. Microvessel parameters and the angiogenesis signaling pathway in endometriotic implants and endothelial cells were studied. RESULT(S): EGCG, but not vitamin E, inhibited microvessels in endometriotic implants. EGCG selectively suppressed vascular endothelial growth factor C (VEGFC) and tyrosine kinase receptor VEGF receptor 2 (VEGFR2) expression. EGCG down-regulated VEGFC/VEGFR2 signaling through c-JUN, interferon-γ, matrix metalloproteinase 9, and chemokine (C-X-C motif) ligand 3 pathways for endothelial proliferation, inflammatory response, and mobility. EGCG also suppressed VEGFC expression and reduced VEGFR2 and ERK activation in endothelial cells. VEGFC supplementation attenuated the inhibitory effects by EGCG. CONCLUSION(S): EGCG inhibited angiogenesis and suppressed VEGFC/VEGFR2 expression and signaling pathway in experimental endometriosis in vivo and endothelial cells in vitro.

A class of human proteins that deliver functional proteins into mammalian cells in vitro and in vivo.

We discovered a class of naturally occurring human proteins with unusually high net positive charge that can potently deliver proteins in functional form into mammalian cells both in vitro and also in murine retina, pancreas, and white adipose tissues in vivo. These findings represent diverse macromolecule delivery agents for in vivo applications, and also raise the possibility that some of these human proteins may penetrate cells as part of their native biological functions.

A stapled p53 helix overcomes HDMX-mediated suppression of p53.

Cancer cells neutralize p53 by deletion, mutation, proteasomal degradation, or sequestration to achieve a pathologic survival advantage. Targeting the E3 ubiquitin ligase HDM2 can lead to a therapeutic surge in p53 levels. However, the efficacy of HDM2 inhibition can be compromised by overexpression of HDMX, an HDM2 homolog that binds and sequesters p53. Here, we report that a stapled p53 helix preferentially targets HDMX, blocks the formation of inhibitory p53-HDMX complexes, induces p53-dependent transcriptional upregulation, and thereby overcomes HDMX-mediated cancer resistance in vitro and in vivo. Importantly, our analysis of p53 interaction dynamics provides a blueprint for reactivating the p53 pathway in cancer by matching HDM2, HDMX, or dual inhibitors to the appropriate cellular context.

In vivo pharmacodynamic imaging of proteasome inhibition.

Inhibiting the proteolytic activity of the 26S proteasome has been shown to have selective apoptotic effects on cancer cells and to be clinically efficacious in certain malignancies. There is an unmet medical need for additional proteasome inhibitors, and their development will be facilitated by surrogate markers of proteasome function. Toward this end, ectopic fusion of the destruction domain from ornithine decarboxylase (ODC) to reporter proteins is often used for assessing proteasome function. For luciferase-based reporters, we hypothesized that the oxygen-dependent destruction domain (ODD) from hypoxia-inducible factor 1 alpha (HIF-1 alpha) may provide improved sensitivity over luciferase-ODC, owing to its extremely rapid turnover by the proteasome (HIF-1 alpha has a half-life of less than 5 minutes). In the current study, we show that ODD-luciferase affords a greater dynamic range and faster kinetics than luciferase-ODC in sensing proteasome inhibition in vitro. Importantly, ODD-luciferase also serves as an effective in vivo marker of proteasome function in xenograft tumor models, with inhibition being detected by noninvasive imaging within 3 hours of bortezomib administration. These data establish ODD-luciferase as a surrogate marker of proteasome function that can be used both in vitro and in vivo for the development of novel proteasome inhibitors.

Proteomic and genetic approaches identify Syk as an AML target.

Cell-based screening can facilitate the rapid identification of compounds inducing complex cellular phenotypes. Advancing a compound toward the clinic, however, generally requires the identification of precise mechanisms of action. We previously found that epidermal growth factor receptor (EGFR) inhibitors induce acute myeloid leukemia (AML) differentiation via a non-EGFR mechanism. In this report, we integrated proteomic and RNAi-based strategies to identify their off-target, anti-AML mechanism. These orthogonal approaches identified Syk as a target in AML. Genetic and pharmacological inactivation of Syk with a drug in clinical trial for other indications promoted differentiation of AML cells and attenuated leukemia growth in vivo. These results demonstrate the power of integrating diverse chemical, proteomic, and genomic screening approaches to identify therapeutic strategies for cancer.