Addresses course outcomes 1 and 4: use knowledge of biological principles and th
ID: 281968 • Letter: A
Question
Addresses course outcomes 1 and 4:
use knowledge of biological principles and the scientific method to ask and answer relevant questions about the human body
weigh and make health-related decisions based on an understanding of the value and limits of scientific knowledge and the scientific method
Before attempting this assignment, you might want to revisit the Scientific Method Tutorial in the Science Learning Center under the Course Content area.
Substance in Green Tea Inhibits Inflammatory Breast Cancer Cells
Inflammatory breast cancer (IBC) is a rare and often fatal form of breast cancer. In IBC, lymphatic vessels in the skin are blocked causing the breasts to appear swollen and red. Early in the disease process, patients with IBC usually do not have the classic “lump” in their breast; therefore the disease is frequently diagnosed at later stages. Diagnosis is often so delayed that the cancer has metastasized and patient prognosis is poor.
The underlying cause of IBC is unknown, but it is believed that like with other cancers cetain cell types have the abililty to transform into cells that can form malignant tumors. These aberrant cells are considered cancer stem cells, and populations of cancer stem cells have been identified in IBC.
In a recent, study researchers evaluated whether a metabolite found in green tea could inhibit the growth of certain stem cell types that have been identified in the breast tissue of patients with IBC. In this study, two IBC stem cell types, SUM-149 and SUM-190, were exposed epigallocatechin-3-gallate (EGCG- is a potent antioxidant found in green tea). Results from the study showed that EGCG treatment inhibited the growth, spread, and survival of the two stem cell types.
For the following questions, please refer to the original paper. The link to the paper is: http://www.plosone.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0073464&representation=PDF
What is the overall hypothesis of this experiment? (Reminder: a hypothesis is a statement that can be tested).
In the Materials and Methods section of the paper, the authors discuss the cell culture and treatment conditions. What was the control group treated with in this section (make sure to look only at the Cell Culture and Treatment section of the paper)? Why?
Again, looking only at the Cell Cuture and Treatment section, what was the experimental group treated with? Why?
In the Results section of the paper, the authors clearly summary their multiple findings. In the "EGCG Reduces Growth of Pre-existing Tumors Derived from SUM-149 Stem-like Cells" results sub-section, the authors report a specfic finding. What specific result do the researchers report?
Did the researchers follow the scientific method in their experimental design? Explain.
Based on the results, was the hypothesis supported, and what can you conclude from this experiment?
Mineva et al. (2013). Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells. PLoS ONE, 8(9): e73464. Doi:10.1371/journal.pone.0073464
Explanation / Answer
What is the overall hypothesis of this experiment? A metabolite in green tea (epigallocatechin-3-gallate) inhibits stem-like inflammatory breast cancer cells.
What was the control group treated with in this section (make sure to look only at the Cell Culture and Treatment section of the paper)? Why?
DMSO (Dimethyl sulfoxide) was added instead of epigallocatechin-3-gallate (EGCG), with everything else in the medium remaining the same, this is so the effect of EGCG can be observed on the cancer stem cells comparing against the results of the control group that lacks the EGCG metabolite.
In the Results section of the paper, the authors clearly summary their multiple findings. In the "EGCG Reduces Growth of Pre-existing Tumors Derived from SUM-149 Stem-like Cells" results sub-section, the authors report a specific finding. What specific result do the researchers report?
They found out that EGCG reduces the self-renewal capacity of SUM-149 cells (tumorsphere formation was decreased with 40 mg/ml of EGCG and completely inhibited with 80 mg/ml of EGCG) and the growth (formation of secondary and tertiary spheres was almost completely inhibited in the presence of EGCG), VEGF-D expression (EGCG reduced the levels of VEGFD RNA by 50%), and survival of the ALDH-positive stem-like subpopulation (treatment of ALDH-positive SUM-149 cells with the higher EGCG doses (80 and 160 mg/ml) induced cell death.
Did the researchers follow the scientific method in their experimental design? Explain.
Yes they did, as they first observed by previous reports that some metabolites in the green tea could inhibit inflammatory cancer cells, which make them formulate the hypothesis that epigallocatechin-3-gallate could inhibit them, later on, they did a lot of experiments to prove their hypothesis by measuring cell growth/cell death, self-renewal capacity by running in vitro tumorsphere assays, measuring expression levels of growth factors, etc.
Based on the results, was the hypothesis supported, and what can you conclude from this experiment?
Yes, it was true that the green tea epigallocatechin-3-gallate metabolite inhibits stem-like inflammatory breast cancer cells through a lot of different pathways, which makes us conclude that such metabolite is capable to decrease the growth of such cells.
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