Lectin-reactive alpha-fetoprotein as a marker for testicular tumor activity

Abstract

Lens culinaris agglutin (LCA)-affinity electrophoresis resolves serum alpha-fetoprotein (AFP) into three isoforms, AFP-L1, -L2 and -L3. The ratio of AFP-L3 to total AFP (AFP-L3%) is frequently high in hepatocellular carcinoma (HCC) patients, and thus, it is widely used for early diagnosis of HCC. In the present study, we used the subfraction profile of LCA-binding AFP to diagnose and monitor testicular tumor activity. Serum samples were collected from 21 testicular tumor patients, and the LCA-reactive fractions were determined by LCA-affinity electrophoresis coupled with antibody-affinity blotting. The histological diagnosis was non-seminomatous germ cell tumor (NSGCT) in 15 patients and pure seminoma in six patients. Serum AFP levels were abnormally elevated (>20 ng/mL) in 10 of 15 NSGCT patients. One NSGCT patient and two seminoma patients showed borderline AFP levels between 10 and 20 ng/mL. LCA-reactive AFP was detected in all 11 NSGCT patients with serum AFP levels above 10 ng/mL, but not in the two seminoma patients with serum AFP levels above 10 ng/mL. In testicular tumor patients, the broad band of AFP-L2 could not be completely separated from AFP-L3. The mean ratio of AFP-L3 plus AFP-L2 (AFP-L2 + 3%) was as high as 94% (range 80-99%) in these patients. Serial determinations of LCA-reactive fractions were performed in eight of the 11 LCA-reactive AFP-positive patients. They included five patients who received chemotherapy, and three patients who underwent orchiectomy for stage I NSGCT. In three of eight patients, LCA-reactive AFP was detected even after normalization of total AFP levels. All three patients relapsed, with elevation of serum AFP within several months. Determination of LCA-reactive AFP might be a useful marker for testicular tumor activity in patients with lower AFP levels.