GAPDH is indeed the internal reference used in PCR and Western blot analysis, but GAPDH has also been shown to be dysregulated in the lung, kidney, breast, stomach, glioma, liver, colorectal, melanoma, prostate, pancreatic, and bladder cancers, and GAPDH is generally upregulated in many types of cancer. Here, GAPDH is linked to urinary bladder cancer.