Melanoma specific protein: detection and characterization of a tumour specific protein from melanotic urine

Circulating Immune Complexes in Human Malignant Melanoma

The sera from 34 patients with malignant melanoma at various clinical stages of the disease were examined for the presence of circulating immune complexes (CIC) by the C1q solid-phase assay. Their urine and serum samples had been previously examined for the presence of an urinary melanoma-specific protein (MSP) and the corresponding serum antibody. Low levels of CIC (only in the third stage of the disease) and no positive correlation with the presence of MSP were found. The discordance between our and other author's data stresses again the fact that the different laboratory methods for CIC evaluation reveal in a different way the various CIC populations occurring in several diseases.

Determination of incidence and partial characterization of tumor-associated antigens found in the urine of patients bearing solid tumors

Urine samples from patients with solid tumors and from donors without malignant disease were concentrated and tested for the presence of tumor-associated antigens. In the complement-fixation assay using serum from a source autologous with the source of the urine, 87.4% of cancer patients were positive, while only 6.9% of control donors were positive. When serum from an allogenic source was used, 94.7% of cancer patients and 35.1% of control donors were positive. Absorption of a cancer patient's serum with autologous tumor cells removed antibody activity to autologous and allogeneic urine samples. Normal lymphocytes, skin, or muscle-cell suspensions were ineffective as absorbents. The excretion of antigen into urine is dependent upon the presence of tumor. Surgical removal of tumor resulted in cessation of antigen excretion. The urine remained antigen-negative as long as the patient remained disease-free. The antigenic activity was heat-stable and comprised molecules of greater than 1,000,000 daltons which could be dissociated into smaller molecular weight active fractions by treatment with 6 M urea.

Further characterization of a melanoma-specific protein from human urine

Isolation of a melanoma-specific protein (MSP) from human urine has been achieved using antibody affinity chromatography. MSP migrates as a single homogeneous protein on SDS PAGE and comparison of these data and ultracentrifuge analyses indicates that MSP contains a single polypeptide chain. MSP, however, shows considerable charge heterogeneity on isoelectric focusing. The desialo form, alpha 2 MSP, is found predominantly in patients with advanced metastatic disease, whilst only the sialo form alpha 1 MSP, is obtained from the urine of patients with early-stage disease. MSP does not react with antisera raised to alpha 1 foetoprotein (AFP) or carcinoembryonic antigen (CEA) and hence is immunologically distinct from these other tumour-associated glycoproteins. Antisera raised to MSP do not react with normal skin melanocytes nor with any foetal tissue tested, and hence the origin of MSP remains unresolved.