Science Buddies: "Ask an Expert"

Hello, I need somebody's advice about a model for cancer cell growth.

I am using an extract from mango seeds to see if they have anti-cancer activity. I have read articles online of the potential anti-cancerous properties of mango seed extract. It apparently has the ability to arrest cell growth. I selected mangoes as they are one of the most abundant fruits in the world.

I am using Saccharoycmes Cerevisiae (yeast that I intend on getting from Boreal Laboratories) as a model for cancer cells. I have access to a microscope, so I would be able to observe them. Is there something that I am missing? Is there a better model organism than yeast? And how would I observe, record and measure the differences (under a microscope) between the control (no mango yeast cells) vs the esperimental group (yeast cells exposed to mango seed extract)? Thank you!

And Happy New Year!

Very interesting idea! I think it may be challenging to test this, but you're off to a good start!

A few thoughts- if you want to use yeast as a model eukaryotic cell, I don't think the microscope will let you observe the differences you care about. You'll probably need to purchase some YPD plates (here's a random website where you can get them- there may be better prices elsewhere). These are petri dishes containing agar for the yeast to grow on and nutrients to feed the cells. If you apply yeast to these plates (at room temp or slightly higher- optimal temp is 30˚C) and then wait a few days, you should see colonies (little round hills that are piles of many many cells) and/or lawns (continuous patches of yeast) appear. You can treat one plate (or better yet, sets of plates) with your mango extract just by pouring/dropping it onto the YPD plate and letting it dry. Then you add yeast to both control (non-mango treated) and experimental plates, and then compare the growth.

It may be a bit hard to dispense the same amount of yeast on each plate, and that sort of variation could affect your results. Do you have access to pipettes? If so, a very common test for growth inhibition is a spotting assay/dilution series (here is a guide I found online- there are probably better ones if you search around- and a fairly hard-to-see diagram). In a nutshell, you take yeast suspended in liquid, dilute them 1:10 (for example, 10 microliters yeast + 90 microliters water), dilute the diluted sample 1:10, and so on until you have a series of less and less concentrated samples. You then drop a small volume of each sample onto the plate in a row and let them grow. At some point in the series, there are too few cells left for colonies to grow, and the plate ends up looking like this. If you compare the same dilution series on a mango-treated plate vs. a control plate, the point in the dilution series at which growth stops may be different if there is an effect from the mango. Here's an example of a real spotting assay where many different conditions were tested.

That's pretty complicated, but I'm not quite sure how else to do this sort of experiment. Maybe another expert has an idea?

Alternatively, you could use planaria instead of yeast. These amazing creatures regenerate after being cut in half, so they could be a good model for cell growth. You could leave some intact, cut some up, and test how each fares in water vs. mango extract + water. Planaria are really fun, and this method could be much easier than using yeast. I don't know if the mango will end up having any effect at all, but a negative result is still a result!

That's a lot to digest, let me know if you want clarification on anything!
Megan

Hi, I agree with Megan's suggestions, but I'd also like to point out that this would not model cancer cell division. Cancer cells have unregulated cell division, whereas as yeast would model normal cell division, and planaria would model stem cell division/differentiation.

I hope this helps!
Jen

Hello,

Just wanted to share my thoughts as well. The best experiment would definitely be to use an actual cancer cell line, but these are obviously difficult to come by unless you have access to a university-level laboratory. Do you happen to have any connections through your school on how you might be able to do this?

Cancer cell lines are vastly different than cultures such as yeast and can have varying degrees of mutations and genetic alterations that make their cell cycle profiles much different. An experiment like this would be very interesting with the proper model because you could determine if your drug is not only slowing growth, but perhaps killing the cells.

Good luck, and please let us know if you have further questions,

Pharma

Thanks for responding!

I have a couple more questions:

1. Do you know of a mutated cell line that might be available online (preferably from Boreal Laboratories) for purchase? I am not sure that I will be able to obtain actual cancer cell lines, but I still will try. My plan is to contact Queen's University to see what I can find out, but I am not very hopeful.

2. The idea of the Planaria is interesting, but a stem cell line is not a mutant line. Any other thoughts on how I could use it as a model for cancer?

3. I have used Daphnia and Drosophila Melanogaster in the past as a model organism, is there any way I could make them have a cancer-like growth that I then try to inhibit?

4. Do you have any more thoughts!

Thanks

As Pharma says, the easiest way to test a compound for anticancer properties is to incubate several cancer cell lines with it and measure viability. Hopefully you can find a university cancer researcher who will let you work in their lab and test your extract under controlled conditions.

You said you have used fruit flies before and they could be a model organism for cancer or at least DNA damage because their mutations often show up as visible changes like eye color and wing shape. Irradiating flies or larvae with X-rays or ultraviolet light is one way to produce mutations in DNA and these can lead to cancer if there are enough mutations in certain control genes. Here's one example of such a project: http://www.education.com/science-fair/a ... uit-flies/

You can also do an experiment with yeast and UV light: http://www.education.com/science-fair/a ... uit-flies/
This project tests sunlight for UV and its affect on DNA damage and cell survival, but you could use a UV lamp to be sure you had a controllable amount of DNA damage. You would compare yeast cells with and without mango seed extract and measure survival. This is not technically cancer, but if DNA mutations are repaired then a cell won't become cancerous in the first place.

I hope this helps. Let us know what you decide to do.

Sybee