Préparations magistrales en radiopharmacie : contraintes liées à la mise en place

Use of radiopharmaceuticals in French nuclear medicine departments depends on marketing authorization and their development may be compromised by a limited return on investment. As an alternative, radiopharmaceuticals may also be prepared in the form of a magistral preparation, like in some European countries. In this case, these preparations are subjected to restrictions and requirements for radiopharmacies relating to quality assurance, facilities and equipment, quality of starting materials and final radiopharmaceutical products defined in French good preparation practice. Labelled tracers used as magistral preparations have to be prepared under the full responsibility of a radiopharmacist and used under the responsibility of the prescribing physician. Conditions of sufficient guarantees for the safety of the patient and adherence to pharmaceutical rules must be evaluated individually. However, this form of preparation intends to supply specific medical needs for an individual patient and is not an answer in the framework of development of radiopharmaceuticals.     

Lead optimization of 5,6-diarylpyridines as CB1 receptor inverse agonists

Optimization of the biological activity for 5,6-diarylpyridines as CB1 receptor inverse agonists is described. Food intake and pharmacokinetic evaluation of 3f and 15c indicate that these compounds are effective orally active modulators of CB1.     

MiR-7 Triggers Cell Cycle Arrest at the G1/S Transition by Targeting Multiple Genes Including Skp2 and Psme3

MiR-7 acts as a tumour suppressor in many cancers and abrogates proliferation of CHO cells in culture. In this study we demonstrate that miR-7 targets key regulators of the G1 to S phase transition, including Skp2 and Psme3, to promote increased levels of p27^KIP and temporary growth arrest of CHO cells in the G1 phase. Simultaneously, the down-regulation of DNA repair-specific proteins via miR-7 including Rad54L, and pro-apoptotic regulators such as p53, combined with the up-regulation of anti-apoptotic factors like p-Akt, promoted cell survival while arrested in G1. Thus miR-7 can co-ordinate the levels of multiple genes and proteins to influence G1 to S phase transition and the apoptotic response in order to maintain cellular homeostasis. This work provides further mechanistic insight into the role of miR-7 as a regulator of cell growth in times of cellular stress.     

Genetic engineering of self-assembled protein hydrogel based on elastin-like sequences with metal binding functionality

Recombinant DNA methods have been exploited to enable the creation of protein-based block copolymers with programmable sequences, desired properties, and predictable three-dimensional structures. These advantages over conventional polymer counterparts facilitate the utility of this new class of biomaterials in a wide range of applications. In this project, we exploited the environmental application of protein-based block copolymers based on elastin-like protein (ELP) sequences. Triblock copolymers containing charged and hydrophobic segments were synthesized. Chain lengths of each segment were manipulated in order to maintain a gelation point below room temperature. Polyhistidine sequences were successfully incorporated into the hydrophilic segment without disruption of the self-assembled hydrogel formation. The microscopic structure was further investigated using laser confocal microscopy. The metal binding capability and capacity of resulting hydrogel were studied to demonstrate the functionality of polyhistidine and its environmental application for heavy metal removal. Reversibility of metal binding was demonstrated, indicating the cost-effectiveness of this hydrogel. Significantly, we envision that this versatile strategy of incorporating functional groups within a 3-D protein network provides new possibilities in creation of biomaterials with great control over structure-property relationships.     

Two mutations impair the stability and function of ubiquitin-activating enzyme (E1)

Protein ubiquitination plays critical roles in the regulation of multiple cellular processes including cell proliferation, signal transduction, oncogenesis, and hypoxic response. TS20 is a Balb3T3-derived cell line in which ubiquitination is inhibited by restrictive temperature. While TS20 has been used to elucidate the degradation of many important proteins including p53, p27, HIF-1α, and ornithine decarboxylase, the molecular basis of its temperature sensitivity has not been fully determined. We cloned full-length E1 cDNA from TS20. Sequencing analysis revealed two point mutations (nt736G to A and nt2313G to C) that lead to substitution of aa189A to T and aa714W to C, respectively. Transient transfection assays revealed that mutant E1 was less stable than its wild-type counterpart, and restrictive temperature (39°C) accelerated its degradation. Under permissive temperature, reverting aa714C to W significantly improved E1 stability and activity. Under restrictive temperature, reverting of both substitutions was required to fully restore E1 stability. Similar results were observed when the mutants were expressed in non-TS20 cells, indicating the mutations are sufficient for its temperature sensitive degradation observed in TS20 cells. Functionally, reverting aa714C to W was sufficient to facilitate the monoubiquitination of H2A and to support TS20 growth at 39°C. It also significantly improved the ubiquitination-dependent disposal of HIF-1α. Our data conclusively demonstrate that mutations introgenic to UVBE1 cause E1 instability, which leads to deficiency of E1 function. Our data establish the molecular basis for unambiguous interpretation of experimental data based on TS20 cells, and provide new insight into the structural determinants of E1 stability.