Down-regulation of the Notch pathway mediated by a gamma-secretase inhibitor induces anti-tumour effects in mouse models of T-cell leukaemia

BACKGROUND AND PURPOSE

gamma-Secretase inhibitors (GSIs) block NOTCH receptor cleavage and pathway activation and have been under clinical evaluation for the treatment of malignancies such as T-cell acute lymphoblastic leukaemia (T-ALL). The ability of GSIs to decrease T-ALL cell viability in vitro is a slow process requiring >8 days, however, such treatment durations are not well tolerated in vivo. Here we study GSI's effect on tumour and normal cellular processes to optimize dosing regimens for anti-tumour efficacy.

EXPERIMENTAL APPROACH

Inhibition of the Notch pathway in mouse intestinal epithelium was used to evaluate the effect of GSIs and guide the design of dosing regimens for xenograft models. Serum Abeta(40) and Notch target gene modulation in tumours were used to evaluate the degree and duration of target inhibition. Pharmacokinetic and pharmacodynamic correlations with biochemical, immunohistochemical and profiling data were used to demonstrate GSI mechanism of action in xenograft tumours.

KEY RESULTS

Three days of >70% Notch pathway inhibition was sufficient to provide an anti-tumour effect and was well tolerated. GSI-induced conversion of mouse epithelial cells to a secretory lineage was time- and dose-dependent. Anti-tumour efficacy was associated with cell cycle arrest and apoptosis that was in part due to Notch-dependent regulation of mitochondrial homeostasis.

CONCLUSIONS AND IMPLICATIONS

Intermittent but potent inhibition of Notch signalling is sufficient for anti-tumour efficacy in these T-ALL models. These findings provide support for the use of GSI in Notch-dependent malignancies and that clinical benefits may be derived from transient but potent inhibition of Notch.

Public talks and science listens: a community-based participatory approach to characterizing environmental health risk perceptions and assessing recovery needs in the wake of hurricanes katrina and rita

In response to the human health threats stemming from Hurricanes Katrina and Rita, inter-disciplinary working groups representing P30-funded Centers of the National Institute Environmental Health Sciences were created to assess threats posed by mold, harmful alga blooms, chemical toxicants, and various infectious agents at selected sites throughout the hurricane impact zone. Because of proximity to impacted areas, UTMB NIEHS Center in Environmental Toxicology was charged with coordinating direct community outreach efforts, primarily in south Louisiana. In early October 2005, UTMB/NIEHS Center Community Outreach and Education Core, in collaboration with outreach counterparts at The University of Texas MD Anderson Cancer Center @ Smithville TX/Center for Research in Environmental Disease sent two groups into southern Louisiana. One group used Lafourche Parish as a base to deliver humanitarian aid and assess local needs for additional supplies during local recovery/reclamation. A second group, ranging through New Iberia, New Orleans, Chalmette, rural Terrebonne, Lafourche and Jefferson Parishes and Baton Rouge met with community environmental leaders, emergency personnel and local citizens to 1) sample public risk perceptions, 2) evaluate the scope and reach of ongoing risk communication efforts, and 3) determine how the NIEHS could best collaborate with local groups in environmental health research and local capacity building efforts. This scoping survey identified specific information gaps limiting efficacy of risk communication, produced a community "wish list" of potential collaborative research projects. The project provided useful heuristics for disaster response and management planning and a platform for future collaborative efforts in environmental health assessment and risk communication with local advocacy groups in south Terrebonne-Lafourche parishes.

PNA openers as a tool for direct quantification of specific targets in duplex DNA

We report a new approach for target quantification directly within DNA duplex. Our assay is based on the formation of a new biomolecular structure, the PD-loop. The approach takes advantage of a selective hybridization of a probe to double-stranded DNA (dsDNA), which is locally opened by a pair of bis-PNA oligomers. To optimize the technique, several experimental formats are tested with the use of PNA and oligonucleotide probes. The highest sensitivity is achieved when the hybridized probe is extended and multiply labeled with 125I-dCTP by DNA polymerase via strand displacement in the presence of single-strand binding (SSB) protein. In this case, the PNA-assisted probe hybridization combined with the method of multiphoton detection (MPD) allows to monitor sub-attomolar amounts of the HIV-1 target on the background of unrelated DNA at sub-nCi level of radioactivity. The developed robust methodology is highly discriminative to single mutations, thus being of practical use for DNA analysis.