A paper published in 2004 found that a drug that binds to microtubules (Apigenin

Question

A paper published in 2004 found that a drug that binds to microtubules (Apigenin) inhibited cell division and induced apoptosis in hormone refractory prostate cancer cells.

a. First, why would it be “good” for Apigenin to induce apoptosis in the prostate cancer cells?

Rubric (3): discuss benefits of a cell going through apoptosis (2)! Of course discuss why it would be good if prostate cancer cells did this (1)

b. In the figure below, the researchers monitored the amount of specific proteins using a western blot. In the experiment, cells were treated with Apigenin for 0, 24, 48, and 72 hours. In the figure, notice that the amount of Bcl2 protein is decreasing, while the amount of Bax protein is increasing. First, what are the normal functions of Bax and Bcl2 in the cell with regard to apoptosis? Why does an increase in Bax and decrease in Bcl2 indicate that the cells are entering apoptosis? Rubric (4): define the role for bax and Bcl2 in apoptosis (2). Relate the function to why there is an increase in Bax and decrease in Bcl2 in cells going through apoptosis (2).

c. The figure also shows that cells treated with Apigenin express increasing amounts of cytochrome c (cyt) and caspase-3 (panel A). They also show increased caspase-3 activity over time (panel B). First, explain how caspase-3 would become active. Second, why are the researchers measuring cytochrome C levels? Rubric (4): Explain what the researchers mean by active caspase, how do we turn this protein on? (2). Why is cytochrome C used to monitor apoptosis? (2).

d. OK, so the data provided shows increased Bax, decreased Bcl2, more cytochrome C and active caspase 9 in cells treated with Apigenin. Do all these results support the idea that the cells are going through apoptosis? Convince me! Rubric (4): Explanation of how the four results when linked together support the conclusion that apoptosis is occurring in cells treated with apigenin.

Explanation / Answer

Rubric (3): apoptosis is a form of cell regulation by means of programmed cell death. It is ued in times of cell damage, repair and also when the cell fails to go through the cell division in the correct fashion, which can lead to cancer. Therefore apoptosis is a molecular stopgap that prevents the cell turning cancerous.

(2) usually a cancer cell has some form of accumulated DNA damage whic prevents it from not undergoing cell cycle, these damaged cells continue to divide at an uncontrollable rate to become a cancer. Incancer cells the switches for apoptosis are usually turned off. So if this drug makes the prostrate cancer cells go back to being able to undergo apoptosis, the cancer cells will die.

Rubric (4) there are different types of apoptotic pathways such as extrinsic, intrinsic and FAs. In the Fas pathway the fas receptor binds to the fas ligand which then starts an apoptotic cascade called death inducing signalling complex (DISC) which leads to cell apoptosis. This is mainatined by a balance of pro-apoptotic (BAX) and anti-apoptotic proteins (BCL2). Since bax levels rise and BCL2 levels fall there is a shift towards proapoptotic factors incresing and leading the way to apoptosis

Rubric (4): Cytochome C presentinside the mitochondria act as caspase activators. Caspases have a central role in the transmission of apoptotic signals. There are two types effector and initiator. once activated initiator caspases bind to an activator protein and then activate effector caspases like caspase 3 which have proteolytic activity and then continue the DISC progarm. hence cytochrome C acts as an activator of caspases and is important for caspase mediated apoptosis

Rubric (4) since BAX which is proapoptotic is upregulated and BCL which is anti apoptotic is downregulated, and also caspase 3 which is an effector caspase is activated. We can infer that the apoptotic pathway in the prostrate cancer cells is getting activated using Apigenin.

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