However, previous studies shed light on possible GGT sources in tumor tissues based on the fact that various cultured human cancer cell lines of different origins, including PC, were found to release soluble GGT corresponding to a specific GGT fraction, namely big-GGT (eluting between 10.0 and 13.5 mL in gel filtration, the molecular weight > 2000 kDa), which occurs in the plasma of healthy individuals [72,73]. This evidence concerns the gene GGT1 and cancer.