Purification of PSA-ACT complex: characterization of PSA-ACT complex by various chromatographic procedures

Thiophilic interaction chromatography of prostate-specific antigen

Prostate-specific antigen (PSA) protein and complexes of PSA with alpha1-antichymotrypsin (PSA-ACT) or alpha2-macroglobulin (PSA-A2M) prepared in vitro, have strong affinity for different thiophilic gels (T-gel). Free PSA, and these PSA complexes can be isolated due to their affinity for T-gels. The average recovery of PSA from several of the T-gels, based upon ELISA measurements, was 84 to 94%. The data suggest that T-gel affinity can be explored for the purification of free and complexed PSA from various biologic fluids.

Advanced glycation end product (AGE): characterization of the products from the reaction between D-glucose and serum albumin

We incubated bovine serum albumin (BSA) with glucose in an attempt to study how the advanced glycation end products (AGEs) are formed and what methods can be used for their identification and isolation. The reaction was monitored by boronated affinity gel, size exclusion and ion exchange chromatography, and chromatofocusing. Reaction products were also characterized by fluorescence measurement, fructosamine assay, and polyacrylamide gel electrophoresis (PAGE). Based on the measurement of AGE-associated fluorescence (excitation, 370 nm; emission, 440 nm) we found that the AGEs could be detected as early as after 3 days incubation. The fluorescence was always associated with the larger molecules of cross-linking product resulting from the reaction between BSA and glucose. The overall fluorescence intensity increased with incubation time and fluorescence of the highest intensity was found with the AGE product largest in size. As with the Amadori product, AGEs also bind to the boronated gel column but with an even higher affinity. Compared to the original albumin monomer AGE molecules are not only larger in size but also have lower isoelectric points and carry more negative charges. Both the size and the negative charges of AGEs continue to increase over time during incubation. This results in a group of cross-linking molecules heterogeneous in size and charge. These results will aid in both the isolation and selection of appropriate AGE molecules for the preparation of anti-AGE antibodies, calibrator, and control in the development of an AGE immunoassay.

PSA immunoreactivity detected in LNCaP cell medium, breast tumor cytosol, and female serum

We made an effort to identify a reliable source for obtaining large quantities of both free (PSA) and PSA-ACT complex for the preparation of the calibrator for the PSA assay. Using size exclusion chromatography, we found both free PSA and PSA-ACT complex in the conditioned cell medium of the LNCaP cell line, which was derived from a human metastatic adenocarcinoma of the prostate. An assay specific for PSA-ACT reacted only with the PSA-ACT complex from cells grown in serum-free medium, and not with the complex from the cell medium grown in 10% calf serum. We also found both free PSA and PSA-ACT complex in 15% of cytosols prepared from breast tumor tissues; the cytosol PSA concentrations ranged from 0.1 to 110 ng/ml. No correlation was found between cytosol PSA and concentrations of estrogen receptor, progestin receptor, epidermal growth factor receptor, cathepsin D, or the ectodomain of c-erbB-2 protein. Based on chromatographic characterizations and the slope of their dose-response curves, it appears that both free PSA and PSA-ACT complex found in the cytosols are similar to PSA complex from the cell medium and the serum of prostate cancer patients. Ectopic PSA was also detected in pooled sera from patients with breast, ovarian, pancreatic, and colon carcinoma. The PSA concentrations in these serum pools increased with the level of their dominant tumor marker. In any event, the LNCaP cell medium appears to be a reliable source for obtaining both free and ACT-complexed PSA of human tumor origin for the preparation of PSA assay calibrators.