instruction:
Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.
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Context: Most solid human tumors exist in an acidic microenvironment, due in part to inefficient vasculature and a higher intrinsic rate of glycolysis. This leads to a tumor-selective pH gradient, which can be exploited therapeutically with antitumor agents such as the camptothecins (CPTs). Previous work in this laboratory has shown that camptothecin activity is enhanced 40- to 60-fold in monolayer cell culture by reducing the extracellular pH to 6.8. Three-dimensional histoculture has been shown to be a technique that allows human tumor tissue to grow in an in vivo-like way with maintenance of tissue histology and function and drug sensitivity for long periods of time.', 'In the current study, we utilized these features of histoculture to study new analogues of camptothecin that have superior pharmacological properties.', 'We evaluated six CPT analogues in histocultures of human brain, neuroblastoma, breast, colon, and prostate tumors. Fragments were exposed to 10,11-methylenedioxy-CPT (MDC), 7-chloromethyl-MDC, SN-38, topotecan (TPT), 9-amino-CPT, 10-amino-CPT, paclitaxel, 5-fluorouracil, 4-hydroperoxycyclophosphamide and doxorubicin, and antitumor activity was assessed. For in vivo tumor outgrowth studies, fragments were treated in parallel, implanted into nude mice, and monitored for development of tumors. RESULTS. Against 15 of 16 tumor xenografts and all primary tumor samples tested, all compounds were cytotoxic at pH 7.4 (IC(50) range 13-921 microM). MDC, SN-38, TPT, and 9-amino-CPT achieved an average 5-fold increase in activity (range 3-14) at pH 6.8, while 7-chloromethyl-MDC was enhanced 8-fold (range 6-14). The most potentiated analogue was 10-amino-CPT at 27-fold (range 17-49). In contrast, the other agents were active against one or more tumor types but were not enhanced by acidic pH. Importantly, the toxicity of MDC in histoculture of D54 glioma xenografts strongly correlated with the outgrowth of treated fragments subsequently implanted in vivo.
Answer: Evaluation of anticancer drug activity in native-state histoculture supports the concept that pH modulation may be an important approach to improve the selectivity and antitumor effectiveness of camptothecin-based chemotherapy.
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Is the activity of camptothecin analogues enhanced in histocultures of human tumors and human tumor xenografts by modulation of extracellular pH?


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Context: In dialysis patients, volume overhydration is common and is related to increased risk of cardiovascular morbidity and mortality. However, it remains unclear whether volume overload imposes those detrimental effects through endothelial dysfunction.', 'In this cross-sectional study, 81 stable patients on continuous ambulatory peritoneal dialysis in a single center were recruited. Volume status was evaluated by extracellular water, assessed by bioimpedance analysis, and normalized to individual height (nECW). Endothelial function was estimated by endothelial-dependent flow-mediated dilatation (FMD) of the brachial artery and expressed as percentage change relative to baseline diameter.', 'There were 37 male and 44 female patients (mean age 61 +/- 12 years, dialysis vintage 20 +/- 23 months). FMD in female patients was significantly higher than that in male patients (9.17% +/- 6.23% vs 6.31% +/- 5.01%, p < 0.05). FMD was negatively correlated with weight (r = -0.308, p < 0.01), body mass index (r = -0.242, p < 0.05), systolic blood pressure (r = -0.228, p < 0.05), ECW (r = -0.404, p < 0.001), and nECW (r = -0.418, p < 0.001). No correlation was found between FMD and other variables. In multiple stepwise regression analysis, calcium x phosphate product (beta = 0.422, p < 0.001), nECW (beta = -0.343, p < 0.01), and dialysis vintage (beta = -0.237, p < 0.05) were independent determinants of FMD (adjusted R(2) = 0.327 for this model).
Answer: There was independent correlation between index of volume status and FMD, and higher nECW was related to worse endothelial function. The results of this study may help us understand the underlying mechanism of volume overhydration leading to increased cardiovascular morbidity and mortality in dialysis patients.
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Is volume overhydration related to endothelial dysfunction in continuous ambulatory peritoneal dialysis patients?


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Context: It is unknown whether hypoxia regulates aurora kinase A (AURKA), a serine/threonine kinase, in neuroblastoma to stimulate cell growth or migration. We sought to determine whether AURKA mediates hypoxia-induced regulation of neuroblastoma tumorigenicity.', 'Human neuroblastoma BE(2)-C cells were treated with CoCl2, a chemical hypoxia mimetic, and MLN8237, a pharmalogical inhibitor of AURKA, to assess cell viability, colony formation and transwell migration. Focal adhesion kinase (FAK) expression was analyzed after silencing of AURKA under normoxic vs. hypoxic conditions.', 'Hypoxia up-regulated expression of AURKA mRNA and protein. CoCl2 stimulated cell proliferation and migration, while inhibiting colony formation. MLN8237 reduced colony formation and cell migration. Silencing of AURKA reduced expression of FAK and pFAK under normoxia and hypoxia.
Answer: Hypoxia positively regulates AURKA expression. Hypoxia-induced stimulation of colony formation and migration is, in part, mediated by AURKA. These findings establish that AURKA is a critical regulator of hypoxia-mediated tumor progression in neuroblastoma.
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Does targeting aurora kinase A inhibit hypoxia-mediated neuroblastoma cell tumorigenesis?