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.

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.
Is the activity of camptothecin analogues enhanced in histocultures of human tumors and human tumor xenografts by modulation of extracellular pH?

Context: In mice, a subpopulation of gut dendritic cells (DCs) expressing CD103 drives the development of regulatory T (T(reg)) cells. Further, it was recently described that the cross-talk between human intestinal epithelial cells (IECs) and DCs helps in maintaining gut immune homeostasis via the induction of non-inflammatory DCs. In this study, an analysis was carried out to determine whether IECs could promote the differentiation of CD103+ tolerogenic DCs, and the function of primary CD103+ DCs isolated from human mesenteric lymph nodes (MLNs) was evaluated.', "Monocyte-derived DCs (MoDCs) and circulating CD1c+ DCs were conditioned or not with supernatants from Caco-2 cells or IECs isolated from healthy donors or donors with Crohn's disease and analysed for their ability to induce T(reg) cell differentiation. In some cases, transforming growth factor beta (TGFbeta), retinoic acid (RA) or thymic stromal lymphopoietin (TSLP) were neutralised before conditioning. CD103+ and CD103- DCs were sorted by fluorescence-activated cell sorting (FACS) from MLNs and used in T(reg) cell differentiation experiments.", "It was found that human IECs promoted the differentiation of tolerogenic DCs able to drive the development of adaptive Foxp3+ T(reg) cells. This control was lost in patients with Crohn's disease and paralleled a reduced expression of tolerogenic factors by primary IECs. MoDCs differentiated with RA or IEC supernatant upregulated the expression of CD103. Consistently, human primary CD103+ DCs isolated from MLNs were endowed with the ability to drive T(reg) cell differentiation. This subset of DCs expressed CCR7 and probably represents a lamina propria-derived migratory population.
Answer: A population of tolerogenic CD103+ DCs was identified in the human gut that probably differentiate in response to IEC-derived factors and drive T(reg) cell development.
Do human intestinal epithelial cells promote the differentiation of tolerogenic dendritic cells?

Context: Non-alcoholic steatohepatitis (NASH) is a subset of non-alcoholic fatty liver disease, the most common chronic liver disease in the U.S. Fibrosis, a common feature of NASH, results from the dysregulation of fibrogenesis in hepatic stellate cells (HSCs). In this study, we investigated whether astaxanthin (ASTX), a xanthophyll carotenoid, can inhibit fibrogenic effects of transforming growth factor β1 (TGFβ1), a key fibrogenic cytokine, in HSCs.', 'Reactive oxygen species (ROS) accumulation was measured in LX-2, an immortalized human HSC cell line. Quantitative realtime PCR, Western blot, immunocytochemical analysis, and in-cell Western blot were performed to determine mRNA and protein of fibrogenic genes, and the activation of Smad3 in TGFβ1-activated LX-2 cells and primary mouse HSCs.', 'In LX-2 cells, ROS accumulation induced by tert-butyl hydrogen peroxide and TGFβ1 was abolished by ASTX. ASTX significantly decreased TGFβ1-induced α-smooth muscle actin (α-SMA) and procollagen type 1, alpha 1 (Col1A1) mRNA as well as α-SMA protein levels. Knockdown of Smad3 showed the significant role of Smad3 in the expression of α-SMA and Col1A1, but not TGFβ1, in LX-2 cells. ASTX attenuated TGFβ1-induced Smad3 phosphorylation and nuclear translocation with a concomitant inhibition of Smad3, Smad7, TGFβ receptor I (TβRI), and TβRII expression. The inhibitory effect of ASTX on HSC activation was confirmed in primary mouse HSCs as evidenced by decreased mRNA and protein levels of α-SMA during activation.
Answer: Taken together, ASTX exerted anti-fibrogenic effects by blocking TGFβ1-signaling, consequently inhibiting the activation of Smad3 pathway in HSCs.

Does astaxanthin prevent TGFβ1-induced pro-fibrogenic gene expression by inhibiting Smad3 activation in hepatic stellate cells?