Colocalization of immunoglobulin binding factor and prostate specific antigen in human prostate gland

IgG gene expression and its possible significance in prostate cancers

BACKGROUND

In spite of recent advances in treatment strategies, prostate cancer (PCa) remains the second leading cause of cancer death in men with its genetic and biologic behaviors still poorly understood. Recently, accumulating evidence indicates that cancer cells, as well as some normal cells can secret IgG. This study was designed to evaluate IgG gene expression and its possible significance in PCa tissue samples and cell lines.

METHODS

IgG expression was assessed by immunohistochemistry, in situ hybridization, immunofluorescence, RT-PCR, and Western blot. The possible significance of IgG was evaluated on tissue array and cell lines. To assess cell viability and proliferation, MTS assay was carried out. Apoptosis was evaluated with propidium iodide and annexin-V staining.

RESULTS

Expressions of IgG and its related genes were detected in cell lines. Abundant gene expressions of Igγ and Igκ chain were detected in PCa tissue samples, but not in normal prostate tissues. In addition, IgG expression was significantly higher in PCa tissues than in the benign prostate hyperplasia tissues (P < 0.001). Igγ expression was positively correlated to Gleason score and histological grade (P < 0.05). Furthermore, in vitro experiments showed that anti-human monoclonal IgG antibody suppressed cell proliferation and increased apoptosis in cultured PCa cells.

CONCLUSION

IgG gene expression in PCa is related to cell differentiation and clinical status. PCa cell produced IgG is involved in the biological behavior of this cancer and may serve as a useful marker for cancer cell differentiation and prognosis. Locally produced IgG could be a potential target for therapy.

Human seminal plasma antibody-binding proteins

PROBLEM

The physiological role of antibody-binding proteins in human seminal plasma and the potential role of these proteins in infertility is relatively unknown.

METHOD OF STUDY

Literature on antibody-binding proteins.

RESULTS

Human seminal plasma has a diverse effect on immune function of the reproductive tracts. This review describes (1) the presence of receptors like proteins that can react with monoclonal antibodies against Fcgamma receptors III (Fcgamma RIII) but are distinctly different from Fcgamma RIII; (2) IgG binding factors (IgGBF), a group of low molecular weight proteins that are capable of binding human IgG; (3) other proteins that can bind antibodies, such as prolactin-inducible protein and three other novel proteins that we have discovered. These proteins potentially all have the ability to reduce the interactions between antisperm antibodies and effector components of the immune system, such as phagocytic cells.

CONCLUSIONS

Human seminal plasma contains proteins that can bind antibodies. However, to date our knowledge of these proteins especially, whether they have a physiological role in either the male and female reproductive tracts is limited.

PSP94 (or beta-microseminoprotein) is a secretory protein specifically expressed and synthesized in the lateral lobe of the rat prostate

BACKGROUND

Prostatic secretory protein of 94 amino acids (PSP94), also called beta-microseminoprotein, is a small, nonglycosylated protein, rich in cysteine residues. It was first isolated as a major protein from human seminal plasma. Subsequently, its homologous proteins were identified, and their cDNAs or genes have been cloned in primates, pigs, and rodents.

METHODS

The present study investigated the expression pattern of PSP94 in the normal Noble rat prostate gland by nonradioactive in situ hybridization, Northern blotting, RT-PCR, Western blotting, and immunohistochemistry. Its expression in the mouse prostate gland was also examined by in situ hybridization.

RESULTS

The results of in situ hybridization, and Northern and Western blot analyses, showed that the expression of rat PSP94 was prostate-specific. It was highly expressed in the lateral prostatic lobe, moderate in the dorsal lobe, weak in the coagulating gland, and negative in the ventral lobe and seminal vesicle. Its specific expression in the rat prostate gland was further confirmed by RT-PCR analysis of prostatic and nonprostatic organ tissues. Its mRNA transcripts were not detected in the urinary, digestive, and respiratory tracts, male and female reproductive organs, muscles, brain, and kidney. Its molecular mass was estimated to be 14.5 kDa by Western blotting. Similar prostate-specific expression of PSP94 was also observed by in situ hybridization in the lateral lobe, but not in the dorsal and ventral lobe, of the mouse prostate gland.

CONCLUSIONS

Rat PSP94 is a major secretory protein highly expressed and synthesized by the lateral lobe of both rat and mouse prostate glands, and moderately expressed in the dorsal lobe of the rat prostate gland.

beta-Microseminoprotein/prostatic secretory protein is a member of immunoglobulin binding factor family

Human seminal plasma contains a factor that binds human IgG, designated as immunoglobulin binding factor (IgBF). Under reducing condition IgBF interacts with anti-Leu-11b, a murine monoclonal antibody raised against human FcgammaRIII/CD16. IgBF shows no binding activity under non-reducing condition. Three components having IgBF activity were separated by HPLC and their amino acid sequences determined. The main IgBF showed structural identity to beta-microseminoprotein (beta-MSP), prostatic secretory protein of 94 amino acids (PSP94) and beta-inhibin. The slight variation in the reported sequences of these proteins has been attributed to analytical error. In the present study the molecular masses of main IgBF and beta-MSP/PSP94 were found to be identical by mass spectrometry. In addition, a large component of IgBF and a shorter beta-MSP consisting of 93 amino acids were identified. The binding of beta-MSP for human IgG and anti-Leu-11b antibody is demonstrable only under reducing condition, determined by Western blot analysis. The present data clearly show that IgBF is a family composed of at least three isoforms. One of the members is beta-MSP/PSP94. This family should be designated as IgBF.