I guess I'm not understanding the concept well. If I treated cells (5000/well) with a range of doses from 6nM to 92nM (and this is an MTT assay and I've used Prism8), why is the IC50 only .9nM? I guess I'm not reconciling what I'm putting into the assay and what prism spits out. Are the values from Prism in the same units as my initial concentration? I also log transformed the values so Idk if that has anything to do with it.
It is hard to answer this without further information. Assuming your analysis in Graph pad prism is correct, I assume that your doses are not in the right concentration range.
If you plot your response (viability) on the y-axis and the log of your concentration on the x-axis you should first have a plateau then a decrease and then plateau again. So your cell should be very viable for some concentrations then the viability should be sunk and at the high concentrations should be not viable anymore.
Prism expects this shape of the dose response curve, if it doesn't look like this it still tries to fit your results and you can get IC50 way of your range.
If your dose response curve doesn't look like this you should increase the concentrations range of your drug.
If you want to shift from in-vitro to in-vivo expriment you must change IC50 to the Dose (Per Kg). you can use CurveExpert application to find exact ic50. In this app you can find the best curve ( closest regression to 1) Usually at the first try you should select wide range of concentration then repeat the MTT assay in a narrow range. So for the second assay I suggest prepare bellow concentration:
1.125, 2.25, 4.5, 9, 18, 36
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