Multi-sequential surface plasmon resonance analysis of haptoglobin–lectin complex in sera of patients with malignant and benign prostate diseases

Screening for prostate cancer remains unsatisfactory. Recent studies have examined the cancer diagnostic/prognostic values of various acute phase proteins, such as haptoglobin. We describe here a novel method of surface plasmon resonance (SPR) based on multi-sequential analysis with SNA-1, AAL, and PHA-L4 lectin, to estimate the glycosylation status of haptoglobin in sera of patients with prostate cancer (n = 15), benign prostate disease (BPD) including benign prostatic hypertrophy (n = 20), and normal subjects (n = 11). The SPR-based analysis involves the use of anti-haptoglobin as ligand and dilution of the analyte to 1400-fold and filtration, followed by detection of the sugar chain by lectin solution. The normalized RU of lectin to haptoglobin represents the binding amount of lectin divided by that of haptoglobin. The normalized RU by SNA-1 of the prostate cancer group was significantly higher than those of the control and BPD group. SNA-1 detected NeuAcα2,6 in a biantennary sugar chain, whose content was the highest among the major glycoproteins in serum. Serum samples diluted about 7000-fold were subjected to microanalysis at 10 ng/μl and 10 μl/min for 4 min. The combination of SNA-1 and haptoglobin by SPR multi-sequential analysis offered the most accurate diagnosis of prostate cancer without any modification of serum glycoproteins.