7 research outputs found
Pharmacological disruption of the Notch transcription factor complex.
Notch pathway signaling is implicated in several human cancers. Aberrant activation and mutations of Notch signaling components are linked to tumor initiation, maintenance, and resistance to cancer therapy. Several strategies, such as monoclonal antibodies against Notch ligands and receptors, as well as small-molecule γ-secretase inhibitors (GSIs), have been developed to interfere with Notch receptor activation at proximal points in the pathway. However, the use of drug-like small molecules to target the downstream mediators of Notch signaling, the Notch transcription activation complex, remains largely unexplored. Here, we report the discovery of an orally active small-molecule inhibitor (termed CB-103) of the Notch transcription activation complex. We show that CB-103 inhibits Notch signaling in primary human T cell acute lymphoblastic leukemia and other Notch-dependent human tumor cell lines, and concomitantly induces cell cycle arrest and apoptosis, thereby impairing proliferation, including in GSI-resistant human tumor cell lines with chromosomal translocations and rearrangements in Notch genes. CB-103 produces Notch loss-of-function phenotypes in flies and mice and inhibits the growth of human breast cancer and leukemia xenografts, notably without causing the dose-limiting intestinal toxicity associated with other Notch inhibitors. Thus, we describe a pharmacological strategy that interferes with Notch signaling by disrupting the Notch transcription complex and shows therapeutic potential for treating Notch-driven cancers
Hiv-1 Gp41 And Gp160 Are Hyperthermostable Proteins In A Mesophilic Environment - Characterization Of Gp41 Mutants
HIV gp41(24-157) unfolds cooperatively over the pH range of 1.0-4.0 with T(m)
values of > 100 degrees C. At pH 2.8, protein unfolding was 80% reversible and
the DeltaH(vH)/DeltaH(cal) ratio of 3.7 is indicative of gp41 being trimeric. No
evidence for a monomer-trimer equilibrium in the concentration range of 0.3-36
micro m was obtained by DSC and tryptophan fluorescence. Glycosylation of gp41
was found to have only a marginal impact on the thermal stability. Reduction of
the disulfide bond or mutation of both cysteine residues had only a marginal
impact on protein stability. There was no cooperative unfolding event in the DSC
thermogram of gp160 in NaCl/P(i), pH 7.4, over a temperature range of 8-129
degrees C. When the pH was lowered to 5.5-3.4, a single unfolding event at around
120 degrees C was noted, and three unfolding events at 93.3, 106.4 and 111.8
degrees C were observed at pH 2.8. Differences between gp41 and gp160, and
hyperthermostable proteins from thermophile organisms are discussed. A series of
gp41 mutants containing single, double, triple or quadruple point mutations were
analysed by DSC and CD. The impact of mutations on the protein structure, in the
context of generating a gp41 based vaccine antigen that resembles a fusion
intermediate state, is discussed. A gp41 mutant, in which three hydrophobic amino
acids in the gp41 loop were replaced with charged residues, showed an increased
solubility at neutral pH
MAFB enhances oncogenic Notch signaling in T cell acute lymphoblastic leukemia
Activating mutations in the gene encoding the cell-cell contact signaling protein Notch1 are common in human T cell acute lymphoblastic leukemias (T-ALLs). However, expressing Notch1 mutant alleles in mice fails to efficiently induce the develo