Cisplatin anti-tumour potentiation by tirapazamine results from a hypoxia-dependent cellular sensitization to cisplatin

Tirapazamine (TPZ) is a new anticancer drug that is activated specifically at the low oxygen level typically found in solid tumours. It exhibits preferential cytotoxicity towards hypoxic cells and has been shown in preclinical studies with transplanted tumours and in phase II and III clinical trials to potentiate the anti-tumour efficacy of cisplatin without increasing its systemic toxicity. At present, the mechanism for this potentiation is unknown. Here we show that there is a schedule-dependent enhancement of cisplatin cytotoxicity by TPZ for cells in vitro that is similar to that seen with transplanted murine tumours. This cisplatin potentiation depends on the TPZ exposure being at oxygen concentrations below 1%, which are typical of many cells in tumours but not in normal tissues. Also, the interaction between TPZ and cisplatin does not occur in cells mutant in ERCC4, a protein essential for repair of DNA interstrand cross-links. Incubation of the cells with TPZ under hypoxia prior to cisplatin treatment increases cisplatin-induced DNA interstrand cross-links with kinetics suggesting that TPZ inhibits or delays repair of the DNA cross-links. In conclusion, we show that the tumour-specific potentiation of cisplatin cytotoxicity is likely the result of an interaction between TPZ and cisplatin at the cellular level that requires the low oxygen levels typical of those in solid tumours. The mechanism of the interaction appears to be through a potentiation of cisplatin-induced DNA interstrand cross-links, possibly as a result of a diminished or delayed repair of these lesion

Application of Consensus Scoring and Principal Component Analysis for Virtual Screening against β-Secretase (BACE-1)

BACKGROUND: In order to identify novel chemical classes of β-secretase (BACE-1) inhibitors, an alternative scoring protocol, Principal Component Analysis (PCA), was proposed to summarize most of the information from the original scoring functions and re-rank the results from the virtual screening against BACE-1. METHOD: Given a training set (50 BACE-1 inhibitors and 9950 inactive diverse compounds), three rank-based virtual screening methods, individual scoring, conventional consensus scoring and PCA, were judged by the hit number in the top 1% of the ranked list. The docking poses were generated by Surflex, five scoring functions (Surflex_Score, D_Score, G_Score, ChemScore, and PMF_Score) were used for pose extraction. For each pose group, twelve scoring functions (Surflex_Score, D_Score, G_Score, ChemScore, PMF_Score, LigScore1, LigScore2, PLP1, PLP2, jain, Ludi_1, and Ludi_2) were used for the pose rank. For a test set, 113,228 chemical compounds (Sigma-Aldrich® corporate chemical directory) were docked by Surflex, then ranked by the same three ranking methods motioned above to select the potential active compounds for experimental test. RESULTS: For the training set, the PCA approach yielded consistently superior rankings compared to conventional consensus scoring and single scoring. For the test set, the top 20 compounds according to conventional consensus scoring were experimentally tested, no inhibitor was found. Then, we relied on PCA scoring protocol to test another different top 20 compounds and two low micromolar inhibitors (S450588 and 276065) were emerged through the BACE-1 fluorescence resonance energy transfer (FRET) assay. CONCLUSION: The PCA method extends the conventional consensus scoring in a quantitative statistical manner and would appear to have considerable potential for chemical screening applications

Clinical predictors of bacterial involvement in exacerbations of chronic obstructive pulmonary disease.

Contains fulltext : 57556.pdf (publisher's version ) (Open Access)BACKGROUND: The wide use of antibiotics for treatment of exacerbations of chronic obstructive pulmonary disease (COPD) lacks evidence. The efficacy is debatable, and bacterial involvement in exacerbation is difficult to verify. The aim of this prospective study was to identify factors that can help to estimate the probability that a microorganism is involved in exacerbation of COPD and, therefore, predict the success of antibiotic treatment. METHODS: Clinical data and sputum samples were obtained from 116 patients during exacerbation of COPD. Bacterial infection was defined by the abundant presence of >or=1 potential pathological microorganism in relation to the normal flora in sputum. RESULTS: Of 116 exacerbations, 22 (19%) had bacterial involvement. The combination of a negative result of a sputum Gram stain, a relevant nonclinical decrease in lung function (compared with baseline measurements), and occurrence of <2 exacerbations in the previous year were 100% predictive of a nonbacterial origin of the exacerbation. The presence of all 3 of these clinical characteristics yielded a positive predictive value of 67% for a bacterial exacerbation. CONCLUSIONS: Patients presenting with an exacerbation who have a negative result of a sputum Gram stain, do not have a clinically relevant decrease in lung function, and who have not experienced <2 exacerbations of COPD in the previous year do not require antibiotic treatment. A treatment protocol taking into account these variables might lead to a 5%-24% reduction in unnecessary treatment with antibiotics, depending on actual prescription rates

The analysis of DNA interstrand cross-links and their repair by the modified comet assay

DNA interstrand cross-links (ICLs) are an extremely toxic form of DNA damage that cells experience upon exposure to natural metabolites. Moreover, ICLs are cytotoxic lesions produced by a range of clinically important anticancer agents. Therefore, improving our understanding of ICL induction and processing has important implications in biology and medicine. The sensitive detection of ICLs in mammalian cells is challenging but has been aided by the development of a modified form of the single-cell gel electrophoresis (SCGE) assay, also known as the “comet assay.” Here we describe this method and how it can be used to sensitively monitor the induction and removal of ICLs in single mammalian cells

Exame do escarro no manejo clínico dos pacientes com pneumonia adquirida na comunidade Sputum examination in the clinical management of community-acquired pneumonia

OBJETIVO: Este estudo retrospectivo avaliou a freqüência do uso da bacteriologia do escarro no manejo clínico de pacientes com pneumonia adquirida na comunidade (PAC) em um hospital geral, e se a utilização deste método modificou a mortalidade. MÉTODOS: Os prontuários de pacientes internados no Hospital Nossa Senhora da Conceição, em Porto Alegre (RS) Brasil, para tratamento de PAC entre maio e novembro de 2004 foram revisados quanto aos seguintes aspectos: idade; sexo; gravidade da pneumonia (escore de Fine); presença de expectoração; bacteriologia do escarro; história de tratamento; resposta clínica; troca de tratamento; e mortalidade. RESULTADOS: Foram avaliados 274 pacientes com PAC, sendo 134 do sexo masculino. Dentre os 274 pacientes, 79 (28,8%) apresentavam, de acordo com o escore de Fine, classe II; 45 (16,4%), classe III; 97 (35,4%), classe IV; e 53 (19,3%), classe V. Em 92 pacientes (33,6%), uma amostra de escarro foi colhida para exame bacteriológico. Obtivemos amostra válida em 37 casos (13,5%) e diagnóstico etiológico em 26 (9,5%), o que resultou em modificação do tratamento em apenas 9 casos (3,3%). A mortalidade geral foi 18,6%. Idade acima de 65 anos, a gravidade da PAC e a ausência de escarro associaram-se à maior mortalidade. A bacteriologia do escarro não influenciou o desfecho clínico, nem a taxa de mortalidade. CONCLUSÃO: O exame do escarro foi uma ferramenta diagnóstica utilizada na minoria dos pacientes, e não trouxe benefício detectável no manejo clínico dos pacientes com PAC tratados em ambiente hospitalar.<br>OBJECTIVE: To evaluate the frequency of the use of sputum examination in the clinical management of community-acquired pneumonia (CAP) in a general hospital and to determine whether its use has an impact on mortality. METHODS: The medical records of CAP patients treated as inpatients between May and November of 2004 at the Nossa Senhora da Conceição Hospital, located in Porto Alegre, Brazil, were reviewed regarding the following aspects: age; gender; severity of pneumonia (Fine score); presence of sputum; sputum bacteriology; treatment history; change in treatment; and mortality. RESULTS: A total of 274 CAP patients (134 males and 140 females) were evaluated. Using the Fine score to quantify severity, we classified 79 (28.8%) of those 274 patients as class II, 45 (16.4%) as class III, 97 (35.4%) as class IV, and 53 (19.3%) as class V. Sputum examination was carried out in 92 patients (33.6%). A valid sample was obtained in 37 cases (13.5%), and an etiological diagnosis was obtained in 26 (9.5%), resulting in a change of treatment in only 9 cases (3.3%). Overall mortality was 18.6%. Advanced age (above 65), CAP severity, and dry cough were associated with an increase in the mortality rate. Sputum examination did not alter any clinical outcome or have any influence on mortality. CONCLUSION: Sputum examination was used in a minority of patients and was not associated with any noticeable benefit in the clinical management of patients with CAP treated in a hospital setting