GRN and prostate cancer: Our previous study investigating the serum GP88 levels in prostate cancer patients [19] reported that serum GP88 levels were different between tumor stage and age groups; i.e., low GP88 levels were more often observed in lower tumor stage groups (pT1/pT2) and in the early age group (≤66 years), and vice versa, increased GP88 levels were more often observed in the higher tumor stage group (pT3/pT4) and in the older age group (>66 years).