Blocking efflux pumps (Cyclosporin A)

[JulietteSV]

Hello,

I have a question regarding an experiment.
First, a quick introduction. I want to study resistance mechanisms of cancer cells to an antibody. My goal is to block the efflux pomps (major MDR effector) with cyclosporin A and so I am trying to determine a dose that will do this, without being "too toxic" for the cells.

In order to determine which dose to use, I performed an MTT test.
Let's say I have 100% cells to start. I want the drug dose corresponding to 90% of cell survival.
Do you know how I can do this? I tried drawing curves on excel and getting the equation...but its a "n" degre polynom that I remember seeing in high school but that I am incapable of solving at this point.

I'm thinking that there's got to be a simpler way of determining the dose concentration....right!?

If you have used cyclosporin A or any ideas on how to determine the dose please help me!!

Thank you!

[CharonY]

It depends on how precise you want/need to be, which is also dependent on how good your data is (i.e. having a very precise model to estimate 90% survival means little if your experimental variation is very high or if the curve has only few points).

In many cases for these values are estimated empirically.

 

That being said, normally dose-response curve follow the Hill Equation. Thus, you fit a curve through your data using regression methods. There is software around that may be able to do that for you (such as Matlab with the curve fitting toolbox). I vaguely recall a paper somewhere in which they even used Excel (I believe in Analytical Biochemistry, 2007?, not sure) to do that.