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.

[EX Q]: Context: Cysteine, a sulfur-containing amino acid, plays an important role in a variety of cellular functions such as protein biosynthesis, methylation, and polyamine and glutathione syntheses. In trypanosomatids, glutathione is conjugated with spermidine to form the specific antioxidant thiol trypanothione (T[SH]2) that plays a central role in maintaining intracellular redox homeostasis and providing defence against oxidative stress.', 'We cloned and characterised genes coding for a cystathionine β-synthase (CβS) and cysteine synthase (CS), key enzymes of the transsulfuration and assimilatory pathways, respectively, from the hemoflagellate protozoan parasite Trypanosoma rangeli.', 'Our results show that T. rangeli CβS (TrCβS), similar to its homologs in T. cruzi, contains the catalytic domain essential for enzymatic activity. Unlike the enzymes in bacteria, plants, and other parasites, T. rangeli CS lacks two of the four lysine residues (Lys26 and Lys184) required for activity. Enzymatic studies using T. rangeli extracts confirmed the absence of CS activity but confirmed the expression of an active CβS. Moreover, CβS biochemical assays revealed that the T. rangeli CβS enzyme also has serine sulfhydrylase activity.
Answer: These findings demonstrate that the RTS pathway is active in T. rangeli, suggesting that this may be the only pathway for cysteine biosynthesis in this parasite. In this sense, the RTS pathway appears to have an important functional role during the insect stage of the life cycle of this protozoan parasite.
[EX A]: Is transsulfuration an active pathway for cysteine biosynthesis in Trypanosoma rangeli?

[EX Q]: Context: Vessel formation is a crucial event in tissue repair after injury. Thus, one assumption of innovative therapeutic approaches is the understanding of its molecular mechanisms. Notwithstanding our knowledge of the role of Protein Kinase C epsilon (PKCε) in cardio-protection and vascular restenosis, its role in vessel progenitor differentiation remains elusive.', 'Given the availability of PKCε pharmacological modulators already tested in clinical trials, the specific aim of this study is to unravel the role of PKCε in vessel progenitor differentiation, with implications in vascular pathology and vasculogenesis.', 'Mouse Peri-Vascular Adipose Tissue (PVAT) was used as source of mesenchymal vessel progenitors. VEGF-induced differentiation of PVAT cells down-regulates both PKCε and p-PAK1 protein expression levels. PKCε overexpression and activation: i) reduced the expression levels of SMA and PECAM in endothelial differentiation of PVAT cells; ii) completely abrogated tubules formation in collagen gel assays; iii) increased the expression of p-PAK1.
Answer: PKCε negatively interferes with vessel progenitor differentiation via interaction with PAK-1.
[EX A]: Is pKCε a negative regulator of PVAT-derived vessel formation?

[EX Q]: Context: The cancer stem cell model links neoplastic cells with normal stem cell biology, but little is known on how normal stem cells are transformed into cancer stem cells.', 'To investigate the processes underlying the transformation of normal stem cells we developed in vitro a cancer stem cell model from human amniotic and chorionic placenta membranes. In this model we studied the expression of specific stem cell molecules by flow cytometry, and genes, by real time RT-PCR. Microscopy immunfluorescence was employed to investigate the proliferative and differentiation patterns. Fluorescence microscopy and FACS were employed to investigate the proliferative and differentiation patterns. To evaluate the tumorigenic potential of our model we injected the cells into NOD.CB17-Prkdcscid/NCrHsd mice.', 'Normal human stem cells from amniotic and chorionic placenta membranes were converted into neural cell lineages, under specific conditions, to form secondary neurospheres with a capacity for self-renewal. After extensive in vitro culture, these cells underwent spontaneous transformations and acquired a neuroblastoma (NB)-like phenotype with an elevated proliferative potential that is comparable to established neuroblastoma cell lines. The ability of these cells to transform their phenotype was evidenced by increased clonogenic ability in vitro; by augmented expression level of certain proliferation- and transformation-related genes (e.g., CCNA2, MYCN, ENPP2, GRIA3, and KIT); by the presence of multinucleated and hyperdiploid cells. We further demonstrated that the transformed phenotype is an NB by measuring the expression of NB-specific markers, disialoganglioside GD2 and N-Myc proteins.
Answer: We have developed a cancer stem cell model starting from normal human stem cells derived from amniotic and chorionic placenta membranes. These cells are able to differentiate into neural cell lineages and to undergo spontaneous transformations and acquire an NB-like phenotype.
[EX A]:
Are human placenta-derived neurospheres susceptible to transformation after extensive in vitro expansion?