[Immunological and biochemical characterization of urinary carcinoembryonic antigen and its clinical significance]

The immunobiochemical properties of urinary carcinoembryonic antigen (U-CEA) purified from non-tumor-bearing patients with urinary tract infection were investigated. Moreover, immunohistochemical localization of CEA in the normal urothelium was studied and clinical significance of U-CEA was also analyzed statistically. The purified U-CEA showed a molecular weight of approximately 160,000 by the Western blotting and an antigenicity identical to the purified CEA (Calbiochem Corp.). Amino acids analysis of U-CEA revealed nearly the same values as the purified CEA or the theoretical values of CEA, except for several amino acids susceptible to hydrolysis and sugar chains. Therefore, it was assumed that the U-CEA was a new CEA-related antigen, different from nonspecific cross-reacting antigen (NCA) or even CEA itself. Immunohistochemically, CEA was found mainly at the cytoplasmic membrane in normal urothelial cells. The urine samples, collected from patients with various urological disorders, were divided into the inflammation group, showing 5 leukocytes/hpf or more in the urine, and the non-inflammation group, showing less than 5 leukocytes/hpf. The groups were subdivided and U-CEA levels were statistically studied; it was found that the U-CEA levels strongly reflected the presence of inflammation, rather than the presence of urothelial tumors. Consequently, it was considered that CEA was present in the normal urothelium and that destruction and regeneration of these cells due to tumor or inflammation might release CEA, not NCA, into the urine.