Personalized synthetic lethality induced by targeting RAD52 in leukemias identified by gene mutation and expression profile.

Homologous recombination repair (HRR) protects cells from the lethal effect of spontaneous and therapy-induced DNA double-stand breaks. HRR usually depends on BRCA1/2-RAD51, and RAD52-RAD51 serves as back-up. To target HRR in tumor cells, a phenomenon called "synthetic lethality" was applied, which relies on the addiction of cancer cells to a single DNA repair pathway, whereas normal cells operate 2 or more mechanisms. Using mutagenesis and a peptide aptamer approach, we pinpointed phenylalanine 79 in RAD52 DNA binding domain I (RAD52-phenylalanine 79 [F79]) as a valid target to induce synthetic lethality in BRCA1- and/or BRCA2-deficient leukemias and carcinomas without affecting normal cells and tissues. Targeting RAD52-F79 disrupts the RAD52-DNA interaction, resulting in the accumulation of toxic DNA double-stand breaks in malignant cells, but not in normal counterparts. In addition, abrogation of RAD52-DNA interaction enhanced the antileukemia effect of already-approved drugs. BRCA-deficient status predisposing to RAD52-dependent synthetic lethality could be predicted by genetic abnormalities such as oncogenes BCR-ABL1 and PML-RAR, mutations in BRCA1 and/or BRCA2 genes, and gene expression profiles identifying leukemias displaying low levels of BRCA1 and/or BRCA2. We believe this work may initiate a personalized therapeutic approach in numerous patients with tumors displaying encoded and functional BRCA deficiency.

Evaluation of cancer dependence and druggability of PRP4 kinase using cellular, biochemical, and structural approaches.

PRP4 kinase is known for its roles in regulating pre-mRNA splicing and beyond. Therefore, a wider spectrum of PRP4 kinase substrates could be expected. The role of PRP4 kinase in cancer is also yet to be fully elucidated. Attaining specific and potent PRP4 inhibitors would greatly facilitate the study of PRP4 biological function and its validation as a credible cancer target. In this report, we verified the requirement of enzymatic activity of PRP4 in regulating cancer cell growth and identified an array of potential novel substrates through orthogonal proteomics approaches. The ensuing effort in structural biology unveiled for the first time unique features of PRP4 kinase domain and its potential mode of interaction with a low molecular weight inhibitor. These results provide new and important information for further exploration of PRP4 kinase function in cancer.

Reproducibility of placental volume and vasculature indices obtained by 3-dimensional power Doppler sonography.

OBJECTIVE: The purpose of this study was to evaluate the reproducibility of 3-dimensional (3D) power Doppler assessment of placental volumes and vascularization before adopting these in routine evaluation of normal and complicated pregnancies. METHODS: A prospective study was performed on 30 normal singleton pregnancies from 11 to 14 weeks. To evaluate placental vascularization, 3D power Doppler sonography was applied to obtain a placental volume, and the volume acquired was analyzed using virtual organ computer-aided analysis. Two consecutive measurements were taken from each patient by two observers blinded to each other's and the individual's previous measurement. This yielded a total of 60 data set pairs. The placental volume, vascularization index, flow index, and vascularization-flow index (VFI) were calculated. Normal distribution of the data was confirmed with the Kolmogorov-Smirnov test. Intraobserver and interobserver correlations were evaluated. Bland-Altman plots and statistics were used to compare the 95% limits of agreement between measurements. RESULTS: All 3D power Doppler placental volumes and vascular indices showed intraobserver correlations of 0.80 or higher. Similar excellent interobserver correlations were seen for all indices with the exception of the VFI, which showed a lower but acceptable correlation. The Bland-Altman analyses indicated good reproducibility of the evaluated placental indices. CONCLUSIONS: Our findings provide validation of the technique, showing good reproducibility of the 3D power Doppler parameters when applied to studies of the placental volume and vascular tree.

Does the combination of fronto-maxillary facial angle and nasal bone evaluation improve the detection of Down syndrome in the second trimester?

OBJECTIVE: To determine if the combination of fronto-maxillary facial (FMF) angle and nasal bone (NB) evaluation improves the detection of Down syndrome (DS) in the second trimester. STUDY DESIGN: We compared the FMF angle measurements in euploid and DS fetuses seen between 2005 and 2008. The FMF angles were measured from stored two-dimensional (2-D) images by investigators blinded to the DS status of the fetus. All NB measurements were obtained prospectively. Receiver operator characteristic curve plot was used to determine the optimal definition for abnormal FMF angle. The detection and false positive rates and likelihood ratios positive and negative for the DS markers and their combinations were compared. RESULTS: Of 22 fetuses with DS seen between 16 and 22 weeks over the study period, NB and FMF angle evaluation was available for 21. These were compared with a control group of 201 fetuses seen at similar gestational age ranges without DS. NB alone identified 10/21 (47.6%) of Down syndrome while FMF angle identified 2/21 (9.5%). The combination of FMF angle and NB identified only one additional case of Down syndrome. CONCLUSIONS: While FMF angle and NB are independent markers for DS, their combination resulted in a minimal but nonsignificant improvement in DS detection.

Identification of a Small Molecule Inhibitor of RAD52 by Structure-Based Selection.

It has been reported that inhibition of RAD52 either by specific shRNA or a small peptide aptamer induced synthetic lethality in tumor cell lines carrying BRCA1 and BRCA2 inactivating mutations. Molecular docking was used to screen two chemical libraries: 1) 1,217 FDA approved drugs, and 2) 139,735 drug-like compounds to identify candidates for interacting with DNA binding domain of human RAD52. Thirty six lead candidate compounds were identified that were predicted to interfere with RAD52 -DNA binding. Further biological testing confirmed that 9 of 36 candidate compounds were able to inhibit the binding of RAD52 to single-stranded DNA in vitro. Based on molecular binding combined with functional assays, we propose a model in which the active compounds bind to a critical "hotspot" in RAD52 DNA binding domain 1. In addition, one of the 9 active compounds, adenosine 5'-monophosphate (A5MP), and also its mimic 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) 5' phosphate (ZMP) inhibited RAD52 activity in vivo and exerted synthetic lethality against BRCA1 and BRCA2-mutated carcinomas. These data suggest that active, inhibitory RAD52 binding compounds could be further refined for efficacy and safety to develop drugs inducing synthetic lethality in tumors displaying deficiencies in BRCA1/2-mediated homologous recombination.

Molecular-modeling based design, synthesis, and activity of substituted piperidines as gamma-secretase inhibitors.

Alzheimer's disease (AD) is a debilitating disease widely thought to be associated with the accumulation of beta amyloid (Abeta) in the brain. Inhibition of gamma-secretase, one of the enzymes responsible for Abeta production, may be a useful strategy for the treatment of AD. Described below is a series of gamma-secretase inhibitors designed from a scaffold identified by a ROCS [J. Comput. Chem.1996, 17, 1653] search of the corporate database.