I am currently examining the effect of paclitaxel on mda mb 231 and mcf-7 using alamar blue assay. Everytime I analyse the results, I get a straight line of growth inhibition at around 50-60%. I never get a sigmoidal curve. I tried changing everything including cell number per well, alamar blue concentration, incubation time , ptx concentration range and much more
What may be the reason for this?
I have done the same experiments using Curcumin and I got nice sigmoidal curve
Thanks
Have you tried increasing the number of datapoints ? The IC50 of Paclitaxel is in the lower nanomolar range. So a few readings at concentrations 50 nM, 100 and 150 nM higher and lower than the IC50 can help to define the slope close to the IC50 value. Then a few datapoints at the upper limit in the millimolar range (where all cells are most likely dead) and few concentrations in the micromolar range (building up to total death) and few more at picomolar concentrations (where all cells are most likely alive) and few readings building up to it should render a nice sigmoidal dose response curve. It is unlikely that Paclitaxel inhibition profile would follow a linear trend of dose-response in mammalian cells. Usually, increasing the number of datapoints (and including very high and very low datapoints) helps to bring out the sigmoidal trend on a Log scale.
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