Hi,

qPCR will give you quantitative data (if designed properly, it is very robust, especially when comparisons are needed), and this is extremely important, as most biological analyses are only semiquantitative, if at all. But qPCR is not enough, as you don't know how the protein behaves, so next thing will be doing Western, that will give you semiquantitative data on the protein of interest. I think immuhistochemistry is the least reliable method, the interpretation of the results could be subjective, and besides nice pictures, in many cases it will not give you really useful data, even w/o going into deeps like rounds of optimizations that could be required to get optimal staining (such as fixation procedures, antigen demasking, ab concentrations etc.). Good luck!