Discovery of potent antagonists of the antiapoptotic protein XIAP for the treatment of cancer

Inhibitor of apoptosis (IAP) proteins are overexpressed in many cancers and have been implicated in tumor growth, pathogenesis, and resistance to chemo- or radiotherapy. On the basis of the NMR structure of a SMAC peptide complexed with the BIR3 domain of X-linked IAP (XIAP), a novel series of XIAP antagonists was discovered. The most potent compounds in this series bind to the baculovirus IAP repeat 3 (BIR3) domain of XIAP with single-digit nanomolar affinity and promote cell death in several human cancer cell lines. In a MDA-MB-231 breast cancer mouse xenograft model, these XIAP antagonists inhibited the growth of tumors. Close structural analogues that showed only weak binding to the XIAP-BIR3 domain were inactive in the cellular assays and showed only marginal in vivo activity. Our results are consistent with a mechanism in which ligands for the BIR3 domain of XIAP induce apoptosis by freeing up caspases. The present study validates the BIR3 domain of XIAP as a target and supports the use of small molecule XIAP antagonists as a potential therapy for cancers that overexpress XIAP.     

Reduction of MTT by aqueous herbal extracts in the absence of cells

The tetrazolium salt 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) is used to determine cell viability in assays of cell proliferation and cytotoxicity. MTT is reduced in metabolically active cells to yield an insoluble purple formazon product. However, in the present study, we demonstrate that some botanical extracts can reduce MTT in the absence of living cells. Treatment of these extracts with iodoacetic acid (IAA) to alkylate free thiol groups inhibited their ability to reduce MTT, indicating that free thiols in the botanical extracts are responsible, at least in part, for the reduction of MTT to the formazon product. These results suggest that caution must be taken when interpreting the results of experiments using the MTT assay to measure the effects of botanical extracts on cell growth.     

Management of postirradiation infection: lessons learned from animal models

Ionizing radiation depresses host defenses and enhances susceptibility to local and systemic infection due to endogenous or exogenous microorganisms. Exposure of mice to a lethal dose of ionizing 60Co-gamma radiation induces a dose-related reduction in the number of both aerobic and anaerobic bacteria from 10(10-12) to 10(4-6) per gram of stool within 4 days. The number of anaerobic bacteria stays low, but the number of Enterobacteriaceae per gram of stool increases significantly up to 10(9) by the 12th day after irradiation. This increase is associated with bacterial translocation of these organisms and fatal bacteremia. The use of quinolones in the irradiated animals was effective in controlling systemic endogenous Gram-negative infection after irradiation. Supplementation with penicillin prevented treatment failures due to Streptococcus spp. and increased survival. Quinolones given for 21 days also were effective in management of systemic exogenous infections due to orally ingested Klebsiella pneumoniae and Pseudomonas aeruginosa. Effectiveness of quinolones may be attributed to inhibition of exogenous organism growth within the gut lumen while preserving the anaerobic gut flora as well as their systemic antibacterial activity. Based on these findings, antimicrobial agents recommended for therapy of infection after exposure to irradiation are: ciprofloxacin, levofloxacin, ceftriaxone, cefepime, gentamicin +/- amoxicillin, or vancomycin.     

Surface calcification of silicone plate intraocular lenses in patients with asteroid hyalosis

PURPOSE: To report three cases in which a silicone-plate lens was explanted because of whitish deposits on the posterior optic surface. DESIGN: Observational case series with clinicopathological correlation. PATIENTS AND METHODS: In the three instances, the deposits were observed at least 2 years after uneventful cataract surgery. All of the patients had unilateral mild asteroid hyalosis in the concerned eye. After explantation of the lenses, gross and light microscopic analyses were performed. The posterior optic surfaces of the lenses also underwent scanning electron microscopy coupled with energy dispersive x-ray spectroscopy for analysis of the elemental composition of the deposits. RESULTS: Gross and light microscopic analyses revealed well-demarcated areas of whitish deposits on the posterior optic surface of the lenses, as well as multiple pits caused by Neodymium:yttrium aluminum garnet laser treatments. The deposits formed an amorphous layer with a "crustlike" appearance, which was confirmed by scanning electron microscopy. X-ray spectroscopy analyses demonstrated the composition of the deposits to be similar to hydroxyapatite. CONCLUSIONS: The material opacifying the lenses was probably derived from the asteroid bodies or from a similar process that results in this vitreous condition. We were unaware of this association between asteroid hyalosis and late postoperative dystrophic calcification of silicone lenses.     

Establishing connections between microarray expression data and chemotherapeutic cancer pharmacology

We have investigated three different microarray datasets of approximately 6 K gene expressions across the National Cancer Institute's panel of 60 tumor cell lines. Initial assessments of reproducibility for gene expressions within each dataset, as derived from sequence analysis of full-length sequences as well as expressed sequence tags (EST), found statistically significant results for no more than 36% of those cases where at least one replicate of a gene appears on the array. Filtering the data based only on pairwise comparisons among these three datasets creates a list of approximately 400 significant concordant expression patterns. The expression profiles of these smaller sets of genes were used to locate similar expression profiles of synthetic agents screened against these same 60 tumor cell lines. A correspondence was found between mRNA expression patterns and 50% growth inhibition response patterns of screened agents for 11 cases that were subsequently verifiable from ligand-target crystallographic data. Notable amongst these cases are genes encoding a variety of kinases, which were also found to be targets of small drug-like molecules within the database of protein structures. These 11 cases lend support to the premise that similarities between expression patterns and chemical responses for the National Cancer Institute's tumor panel can be related to known cases of molecular structure and putative cellular function. The details of the 11 verifiable cases and the concordant gene subsets are provided. Discussions about the prospects of using this approach as a data mining tool are included.     

The epidemiology of tick-borne relapsing fever in the United States

Each year, many residents of and visitors to endemic regions of the western United States are exposed to the vector of tick-borne relapsing fever (TBRF), an underrecognized and underreported disease. Through review of report forms and literature review, we identified 450 cases of TBRF acquired in the United States in 11 western states (and in British Columbia by a U.S. resident) from January 1977 to January 2000. Exposure sites were in forested areas, at varying elevations, in mountainous regions (Cascade, Rocky Mountain, San Bernardino, and Sierra Nevada ranges) of the United States and Canada and in limestone caves in central Texas. Only 13 counties accounted for approximately 50% of all cases. Forty percent of the cases were not residents of the state where TBRF exposure occurred, including 7% from 11 states where TBRF is not endemic. TBRF is endemic in the United States and is a disease affecting travelers, who may return home with the disease to areas where physicians are not familiar with it.     

Analysis of 185 iliac vessel injuries: risk factors and predictors of outcome

HYPOTHESIS: Iliac vascular injuries incur high mortality. DESIGN: Retrospective 100-month study (January 1, 1992, through April 30, 2000). PATIENTS: One hundred forty-eight patients with 185 iliac vessel injuries. OUTCOME MEASURES: Survival and mortality, analyzed by univariate and logistic regression. RESULTS: Admission mean +/- SD systolic blood pressure was 81 +/- 42 mm Hg, mean Revised Trauma Score was 6.0 +/- 2.8, and mean Injury Severity Score was 20.0 +/- 9.5. The mechanism of injury was penetrating in 140 patients (95%) and blunt in 8 (5%). The mean estimated blood loss was 6246 +/- 6174 mL. Of the 185 injured vessels, 71 (99%) of 72 iliac arteries were repaired, 101 (89%) of 113 iliac veins were ligated, and 12 (11%) of 113 iliac veins were repaired. Overall survival was 51% (76/148). Mortality was 82% (49/72) in patients with exsanguination. Survival by vessel: iliac artery, 57% (20/35); iliac vein, 55% (42/76); and iliac artery and vein, 38% (14/37). Significant predictors of outcome were thoracotomy in the emergency department, associated aortic injury, inferior vena cava injuries, iliac artery and vein injury, intraoperative arrhythmia, and intraoperative coagulopathy. On logistic regression, independent risk factors for survival were absence of thoracotomy in the emergency department, surgical management, and arrhythmia. Mortality by grade on the Organ Injury Scale of the American Association for the Surgery of Trauma (AAST-OIS) was as follows: grade III, 35% (33/95); grade IV, 71% (24/34); and grade V, 79% (15/19). CONCLUSIONS: Mortality remains high. Associated vessel injuries and intraoperative complications predict mortality. AAST-OIS grade for abdominal vascular injuries correlates well with mortality.     

LC/MS/MS structure elucidation of reaction intermediates formed during the TiO2 photocatalysis of microcystin-LR

Microcystin-LR (MC-LR), a cyanotoxin and emerging drinking water contaminant, was treated with TiO₂ photocatalysts immobilized on stainless steel plates as an alternative to nanoparticles in slurry. The reaction intermediates of MC-LR were identified with mass spectrometry (MS) at pH of Milli-Q water (pH_sq=5.7). Eleven new [M+H]⁺ were observed in the liquid chromatography mass spectrometry (LC/MS) chromatogram with some of them giving multiple peaks. Most of these reaction intermediates have not been reported from previous studies employing TiO₂ nanoparticles at acidic conditions (pH=4.0). Investigating the effects of pH (for 3.02 photocatalytic films showed that acidic conditions are preferable for the degradation. Combined with the limited surface area of the films and the absence of additional oxidants (i.e., H₂O₂) the degradation was slower and more intermediate steps were identified. Possible structures of the intermediates (formed at neutral pH) after analyzing the corresponding MS/MS spectra are reported. The collision-induced dissociation of the [M+H]⁺ of MC-LR and the intermediates 1011.5 and 1029.5 are discussed and possible fragmentation pathways and mechanisms are also proposed. Analysis of the MS/MS spectra indicates that the fragmentation of some amino acids is less favorable because of internal interaction with free groups of adjacent amino acids. The MS/MS spectra assisted in determining hydroxylation sites, by the formation or alteration of specific product ions such as m/z 599.     

Community Health Workers: Examining the Helper Therapy Principle

A community approach to the integration of health and social services for low-income pregnant women is being addressed through Community Integrated Service System (CISS) initiatives of the Maternal Child Health Bureau. This particular CISS program model was designed to enable low-income mothers to function in a Community Health Worker (CHW) role providing social support for at-risk pregnant women. Using Riessman's notion of "helper therapy," the model was also developed to enhance the potential for CHWs to gain helper benefits. The purpose of this exploratory study was to describe perceived helper benefits and stressors associated with the CHW role and to examine the usefulness of an instrument developed to assess benefits and stressors. The study findings revealed that the majority of CHWs perceived helper benefits that included positive feelings about self, a sense of belonging, valuable work experience, and access to health information and skills through training or contact with program staff. Stressors such as feeling inadequate to help, however, were associated with the helper role for some CHWs. Preliminary analysis of the Helper's Perception Measure indicated that it may be an effective measure and should be tested with a larger sample of CHWs.