I perform real time PCR for a cancer patient to check the NIS expression levels where I use Gapdh as an reference gene. How can I calculate ddCT in this context as I do not have the tissue from the respective tumor sample. Or will relative expression be enough to give an explanation while writing a paper?
You can't obtain a ddCt from a single sample, if I am understanding your question correctly. The question you would use ddCt for is whether NIS expression changes (up or down) in one tissue/cell sample versus another, relative to a standard gene whose expression should not change (in your case GAPDH).
Dear Professor,
Thank you for your correction. Finally I found out one solution in which with the reference of three papers I followed this method.
Relative expression levels were calculated according to the formula 2 ((Ce-Re)/2 (Cn-Rn)) in which Ce is the Ct cycle number observed in the experimental sample for the control gene, Re is the Ct cycle number observed in the experimental sample for the target gene, Cn is the average Ct cycle number observed in the normal thyroid tissues for the control gene, and Rn is the average Ct cycle number observed in the normal thyroid tissues for the target gene (since I dont have normal tissue for all tumor tissue I considered 10 normal tissues and calculated the mean dCT of these samples).
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