I want to do combination studies of various wnt inhibitors with chemotherapeutic drugs. I have calculated their IC50 values by MTT assay. Now i am confused how to design combinations. I am thinking to add fixed dose (IC50) of inhibitor to various doses of chemotherapeutic drugs. can anyone help me in regarding this?
You can use the model established by Chou Talalay(2006). I used this model in my experiments. With this model, you can use data obtained with MTT assay. Calcusyn and Compusyn were the software used. For experimental design, you must first know the IC50 of each individual treatment. After, you should perform the treatments individually and combined at the follow concentrations: 4, 2, 1, 0.5, 0:25 and 0.125X the IC50 value of the treatments, combined and individually.
You cant use fixed dose because drugs may produce synergism at specific concentrations and antagonism at others . The correct way to do that is to is to take different concentrations for both drugs above and below their IC50 values then you calculate the IC50 of the combination. Finally you calculate the combination index if it is below 1 then you have synergism. see the following reference for further details:
Enhancement of Docetaxel Anti-cancer Activity by A Novel
Diindolylmethane (DIM) Compound in Human Non-Small Cell Lung
Cancer
Clin Cancer Res. 2009 January 15; 15(2): 543–552. doi:10.1158/1078-0432.CCR-08-1558.
You can use the model established by Chou Talalay(2006). I used this model in my experiments. With this model, you can use data obtained with MTT assay. Calcusyn and Compusyn were the software used. For experimental design, you must first know the IC50 of each individual treatment. After, you should perform the treatments individually and combined at the follow concentrations: 4, 2, 1, 0.5, 0:25 and 0.125X the IC50 value of the treatments, combined and individually.
All the answers mentioned above are the best. Just to add to it, even if you donot see any synergism, you can check if this wnt inhibitor can potentiate the cell killing mechanism in combination with cytotoxic drugs at very low dose. Refer Singh et al., 2014, cancer letters.
All the best
thanx lucas and urja. jst want to know one more thing.. i am adding 100 microlt of 1st drugs. do i need to add same volume of my 2nd drug or can i add less than 100 microlt
Generally according to my experience this volume of drug is so high and toxic for the cells even for all the studies.
You must try to reduce the volume of the drugs that you add to not more than 3.5 microliters to have a good results
I generally agree with Ayman. And one of the reasons for making combination studies is to be able to use the least concentrations that may produce synergism.
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