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.
--------
Question: Context: Photodynamic therapy (PDT) is linked with oxidative damage of biomolecules causing significant impairment of essential cellular functions that lead to cell death. It is the reason why photodynamic therapy has found application in treatment of different oncological, cardiovascular, skin and eye diseases. Efficacy of PDT depends on combined action of three components; sensitizer, light and oxygen. In the present study, we examined whether higher partial pressure of oxygen increases lethality in HeLa cell lines exposed to light in the presence of chloraluminium phthalocyanine disulfonate (ClAlPcS2).', 'ClAlPcS2- sensitized HeLa cells incubated under different oxygen conditions were exposed to PDT. Production of singlet oxygen ((1)O2) and other forms of reactive oxygen species (ROS) as well as changes in mitochondrial membrane potential were determined by appropriately sensitive fluorescence probes. The effect of PDT on HeLa cell viability under different oxygen conditions was quantified using the standard methylthiazol tetrazolium (MTT) test.', 'At the highest oxygen concentration of 28 ± 2 mg/l HeLa cells were significantly more sensitive to light-activated ClAlPcS2 (EC50=0.29 ± 0.05 μM) in comparison to cells incubated at lower oxygen concentrations of 8 ± 0.5 and 0.5 ± 0.1 mg/l, where the half maximal effective concentration was 0.42 ± 0.06 μM and 0.94 ± 0.14 μM, respectively. Moreover, we found that the higher presence of oxygen is accompanied with higher production of singlet oxygen, a higher rate of type II photodynamic reactions, and a significant drop in the mitochondrial membrane potential.
Answer: These results demonstrate that the photodynamic effect in cervical cancer cells utilizing ClAlPcS2 significantly depends on oxygen level.

Answer: Does high oxygen partial pressure increase photodynamic effect on HeLa cell lines in the presence of chloraluminium phthalocyanine?


Question: Context: The authors previously described the complete regression of established neuroblastoma (NB) by the adoptive transfer of syngeneic interleukin-12 transduced dendritic cells (DC) from naive mice. However, some malignancies, like NB, abrogate DC immunostimulation. The authors hypothesize that IL-12 transduction of DC from NB-bearing mice will have the same antitumor properties.', 'A/J mice (n = 32) with established NB received peritumoral injection of 1 x 10(6) DC (DC, IL-12 DC, day 7 IL-12 DC or day 14 IL-12 DC) on day 7. Tumor growth, phenotype, and ability to induce NK and T cell activity were measured.', 'Vaccination with naive admIL-12 DC resulted in 100% tumor regression and prolonged survival. Transduced DC induced only partial responses in 75% (day 7) and 25% (day 14) of animals. No differences in phenotype or effector cell activation were noted between admIL-12DC in tumor-bearing or naive mice.
Answer: IL-12 DC from tumor-bearing animals have a decreased ability to induce antitumor activity against established murine NB. This decreased capacity appears to be related to the duration of exposure to tumor because day 14 transduced DC had less of an effect than day 7 DC, despite similar phenotypes and ability to activate immune effector cells.

Answer: Does advanced neuroblastoma impair dendritic cell function in adoptive immunotherapy?


Question: Context: PS-341 (bortezomib, Velcade), the first proteasome inhibitor approved by the Food and Drug Administration for the treatment of patients with relapsed multiple myeloma, induces apoptosis in human cancer cell lines. Vitamin C (ascorbic acid) is an essential water-soluble vitamin required for many normal physiologic functions and has to be obtained through diet or supplemental tablets in humans. Here we studied the potential effect of vitamin C on the anticancer activity of PS-341 in human cancer cell lines.', 'The effects of vitamin C on apoptosis induction by PS-341 alone and by PS-341 combined with tumor necrosis factor-related apoptosis-inducing ligand were studied. In addition, the effects of vitamin C and other antioxidants on PS-341-mediated proteasome inhibition were also examined. Finally, the direct chemical interaction between vitamin C and PS-341 was determined.', 'Vitamin C abrogated the ability of PS-341 to induce apoptosis in various human cancer cell lines, to induce G(2)-M arrest, and to augment apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand. Moreover, vitamin C suppressed PS-341-mediated inhibition of proteasome activity. PS-341 itself did not induce generation of intracellular reactive oxygen species whereas other antioxidants failed to abrogate its biological activity. Importantly, we detected a direct chemical interaction between vitamin C and PS-341.
Answer: Vitamin C directly binds to PS-431, thus inactivating PS-341 independent of its antioxidant activity. Our findings suggest that vitamin C may have a negative effect on PS-341-mediated anticancer activity.

Answer:
Does vitamin C inactivate the proteasome inhibitor PS-341 in human cancer cells?