Will the target protein invariably be upregulated or downregulated following overexpression or knocking down of the target gene?

Owing to post-translational regulatory mechanisms，and the uncertainty regarding the specificity of the target antibody, it is not always possible to detect an upregulation or downregulation of the protein at the protein level after overexpression or interference regulation of the cell. If the target antibody fails to detect the overexpression or knocking down, attempting to use qPCR or a tag antibody for detection could be an option.