NONSPECIFIC CROSS-REACTING ANTIGEN 50 90 IS ELEVATED IN PATIENTS WITHBREAST, LUNG, AND COLON-CANCER/

A total of 22 genes have been identified in the carcinoembryonic antig en (CEA) gene family The protein products of this family are highly ho mologous and include CEA, biliary glycoprotein, nonspecific cross-reac ting antigen 50/90 (NCA 50/90), NCA 95, and pregnancy-specific beta-gl ycoprotein. We used a monoclonal antibody with high affinity to develo p a specific enzyme-linked immunosorbent assay (ELISA) method for NCA 50/90 in serum and plasma. Our calibrators were based on affinity-puri fied recombinant protein from a Baculovirus expression system. No sign ificant reactivity with purified CEA, recombinant NCA 95, or recombina nt biliary glycoprotein was found by Western blot analysis or in the E LISA method. Only 1 of 15 sera from pregnant women (chorionic gonadotr opin > 1000 ng/ml) was positive in the NCA 50/90 ELISA, suggesting tha t this method does not detect pregnancy-specific glycoprotein. A cutof f value of 18 ng/ml was established based on the 95% value of serum an d plasma from 147 healthy volunteers. Only 3 of 31 serum and plasma sa mples from patients with clinically inactive breast cancer were elevat ed above the cutoff value, but 44% of 136 samples from patients with c linically active breast cancer were positive. NCA 50/90 measurements w ere elevated in 7 of 25 patients with active breast cancer whose CEA a nd CA 15-3 values were below cutoff, and NCA 50/90 values do not corre late with CEA in breast cancer. In addition, we found sensitivities of 70, 39, and 42% for lung cancer, colon cancer, and leukemia, respecti vely. The sensitivity for non-small cell Lung cancer was 85%, however, compared to 50% for small cell lung cancer. Serum from Leukemia patie nts showed an overall sensitivity of 43%, but 71% (10 of 14) sera from patients with chronic myelogenous leukemia were positive compared to, for example, chronic lymphocytic leukemia where 0 of 7 sera had NCA 5 0/90 values above the cutoff. These studies suggest that NCA 50/90 may have clinical utility in the management of patients with a variety of cancers.