Immunohistochemical evaluation of proliferating cell nuclear antigen, prostate-specific antigen and alpha 1-antichymotrypsin in human prostate cancer

PSA forms complexes with α1-antichymotrypsin in prostate

BACKGROUND

PSA is the most useful prostate cancer marker. However, its levels are increased also in some non-malignant conditions. In circulation, the majority of PSA is complexed with protease inhibitors, including α(1) -antichymotrypsin (ACT). The proportion of the PSA-ACT complex is higher in patients with prostate cancer than in controls without cancer. The expression of ACT has been shown to be higher in prostate cancer than in benign prostatic hyperplasia. However, results regarding the extent which PSA forms complexes within the prostate and whether there are differences in complex formation between normal and malignant prostatic tissue are inconsistent and limited.

METHODS

We studied complex formation of PSA secreted by cultured human prostate tissues and in the tissue by in situ proximity ligation assay (PLA). Free, total and active PSA, and the PSA-ACT complex were determined in tissue culture media by immunoassays, immunoblotting, and chromatographic methods.

RESULTS

The majority of PSA in tissue culture medium was free and enzymatically active. However, a significant proportion (1.6 ± 0.5%) of immunoreactive PSA was found to be complexed with ACT. Complex formation was confirmed by in situ PLA, which showed more intense staining of PSA-ACT in cancers with Gleason grade 3 than in adjacent benign tissues from the same patients.

CONCLUSIONS

These results show that PSA forms complexes already within the prostate and that PSA-ACT levels are increased in moderately differentiated prostate cancer tissue. This may explain, at least partially, why the ratio of serum PSA-ACT to total PSA is increased in prostate cancer.

Effect of castration on extracellular matrix remodeling and angiogenesis of the prostate gland

This study was conducted to evaluate the long term effect of castration on the prostate gland proliferation, extracellular matrix remodeling and angiogenesis. Prostate gland proliferation was assessed by immunolocalization of proliferating cell nuclear antigen (PCNA). The expression level of vascular endothelial growth factor (VEGF), transforming growth factor-beta (TGF-beta) and metaloprotenase-13 (MMP-13) by the prostate gland were assessed by immunohistochemistry and quantitative real-time PCR. The expression of the above mentioned parameters by the prostate gland of mature intact dogs were compared to that of castrated dogs six months post-castration. The results showed that castration induced a remarkable atrophy of the prostate gland which was associated with a highly significant decrease in the PCNA proliferation index. Although TGF-beta protein was immunolocalized to the epithelial and stroma cells of the prostate gland from both intact and castrated dogs, castration induced a significant up-regulation of TGF-beta mRNA expression. VEGF mRNA expression and its encoded protein immunolocalization were decreased significantly by the prostate gland from castrated dogs as compared to that of intact dogs. Castration, on the other hand, resulted in no significant change in MMP-13 mRNA expression despite an effect on its cellular immunolocalization which appeared to be localized to the epithelial and stromal cells of the prostate gland from castrated dogs as compared to epithelial cells of the prostate gland from intact dogs. These results indicated that castration-induced prostate gland regression continued to exert a potent suppressive effect on prostate gland proliferation which might be mediated by the elevated level of TGF-beta. Moreover, the low expression level of VEGF might reflect a reduced blood flow demand by the regressed and growth-dormant prostate after castration.

Prostatic manipulation has a minimal effect on complexed prostate-specific antigen levels

OBJECTIVE

To assess the effect of prostatic manipulation on complexed prostate-specific antigen (cPSA), as various forms of prostatic manipulation are known to increase the serum free and total PSA level.

PATIENTS AND METHODS

A series of 92 men (58 after prostatic biopsy, 16 after digital rectal examination and 18 after flexible cystoscopy) were assessed. Blood samples were taken from each patient before and 30 min after manipulation. Total and cPSA levels were measured using appropriate assays, respectively.

RESULTS

There was no significant increase in cPSA levels after flexible cystoscopy and digital rectal examination, but prostate biopsy caused a statistically significant although minimal rise in cPSA level. There was no statistically significant increase in cPSA level after prostate biopsy in patients with prostate cancer (P = 0. 35) although there was a statistically significant but minimal rise in cPSA level in patients with benign histology (P < 0.01, mean increase 2.13 ng/mL) compared with that of total PSA, which increased markedly (P < 0.01, mean increase 19.79 ng/mL).

CONCLUSION

Prostatic manipulation has minimal effects on cPSA levels.

Adenovirus-mediated suicide-gene therapy using the herpes simplex virus thymidine kinase gene in cell and animal models of human prostate cancer: changes in tumour cell proliferative activity

OBJECTIVES

To determine the feasibility and efficacy of suicide-gene therapy using adenovirus (Ad)-mediated herpes simplex virus thymidine kinase (HSV-TK) and the prodrug acyclovir, and to evaluate changes in the biological phenotype for tumour cell proliferative activity after suicide-gene therapy in animal models of human prostate cancer.

MATERIALS AND METHODS

Using a replication-defective adenoviral vector (cytomegalovirus, CMV) containing the beta-galactosidase gene (Ad-CMV-beta-gal) as a control and Ad-CMV-TK as the therapeutic vector under the transcriptional control of the CMV promoter, transduction efficiency was assessed in vitro by infecting LNCaP and PC-3 androgen-dependent and independent human prostate cancer cells with Ad-CMV-beta-gal, and using X-gal staining. The TK activity in prostate cancer cells infected with Ad-CMV-TK was determined by measuring TK-mediated [3H]-gancyclovir phosphorylation. The sensitivity of LNCaP and PC-3 cells to Ad-CMV-TK in vitro was determined after infection with the therapeutic vector with or without acyclovir. The inhibition of PC-3 tumour growth in vivo induced by the Ad-CMV-TK/acyclovir suicide-gene system was assessed in separate and controlled experiments using human prostate cancer mouse models. Ki-67 proliferative antigen and proliferating cell nuclear antigen (PCNA), both useful proliferative indices, were evaluated using immunohistochemical staining (MIB-1 monoclonal antibody and monoclonal anti-PCNA antibody) in formalin-fixed, paraffin-embedded tissues from gene therapy-treated and control animals.

RESULTS

The mean TK activity was significantly higher in LNCaP and PC-3 cells infected with Ad-CMV-TK than in cells infected with Ad-CMV-beta-gal, used as a control (P < 0.05). The growth of human prostate cancer cells with Ad-CMV-TK was significantly inhibited by adding acyclovir in vitro (P < 0.05). In the in vivo experiments using the PC-3 human prostate cancer mouse model, tumour volume and growth was lower in mice treated with Ad-CMV-TK/acyclovir than in those treated with Ad-CMV-TK only, acyclovir only or untreated (controls) (P < 0.05). Histochemical staining of tumour tissues showed that Ad-CMV-TK/acyclovir destroyed PC-3 tumours through tumour cell death and apoptosis, with local lymphatic infiltration. The mean PCNA labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was significantly lower than that in untreated controls (P < 0.05, Mann-Whitney U-test). The Ki-67 labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was also lower than that in untreated controls (P < 0.05, Student's t-test). Adenovirus-mediated suicide-gene therapy using the HSV-TK gene decreased the proliferative activity of PC-3 human prostatic cancer cells in vivo.

CONCLUSIONS

Adenovirus-mediated suicide-gene therapy using an HSV-TK/acyclovir system provided effective therapy in an experimental human prostate cancer mouse model, by significantly inhibiting tumour growth and decreasing the proliferative activity of human prostate cancer cells. Such therapy could be developed as a novel method for treating patients with androgen-independent prostate cancer.

Molecular Forms of Prostate-specific Antigen in Malignant and Benign Prostatic Tissue: Biochemical and Diagnostic Implications

Background: Patients with prostate cancer (PCa) show a lower ratio of free prostate-specific antigen (fPSA) to total PSA (tPSA) in serum than patients with benign prostatic hyperplasia (BPH). The patterns of the intracellular PSA isoforms in malignant and benign prostatic tissue have been studied as potential molecular reasons for this phenomenon.

Methods: Prostatic tissue samples were obtained after cystoprostatectomy from patients with bladder cancer (n = 10), from BPH patients (transurethral resection of the prostate, n = 10; adenomectomy, n = 10), and from the cancerous and noncancerous parts of the same prostates removed surgically by prostatectomy because of PCa (n = 20). PSA pattern was characterized by gel filtration, immunoblotting, and immunoassays for tPSA, fPSA, α1-antichymotrypsin-PSA (ACT-PSA), and complexed PSA (Bayer Immuno 1 assay). Comparisons were made with the PSA concentrations in serum.

Results: The major portion of tPSA in all tissue samples was fPSA; complexed PSA forms were &lt;2%. Samples from cystoprostatectomy patients had the lowest and those from adenomectomy patients the highest values of tPSA and fPSA. PSA concentrations were lower in cancerous than in the noncancerous parts of the prostate. No significant correlations were found between tumor stage or grade and the amounts of tPSA, fPSA, and ACT-PSA in tissue. Tissue PSA values were not correlated with the serum PSA concentrations nor with the ratios fPSA/tPSA and ACT-PSA/tPSA in sera.

Conclusions: The amounts of tPSA and the PSA isoforms in prostatic tissue explain neither the concentrations of tPSA and PSA isoforms in serum nor the behavior of the ratio fPSA/tPSA in patients with BPH and PCa.

Immunohistochemical finding of alpha-1-antichymotrypsin in tissues of benign prostatic hyperplasia and prostate cancer

BACKGROUND

Ratio of free to total (F/T) prostate-specific antigen (PSA) is higher in the blood of patients with benign prostatic hyperplasia than those with prostate cancer. To clarify the difference between ratios in these two, alpha-1-antichymotrypsin, the major component of the bound PSA in the blood, was immunohistochemically examined.

METHODS

Tissues were obtained surgically via a retropubic approach from patients with benign prostatic hyperplasia (nine cases) and prostate cancer (27 cases). These samples were processed in paraffin blocks, cut into 5 mm sections and stained with antibodies against alpha-1-antichymotrypsin and PSA.

RESULTS

The percentage of alpha-1-antichymotrypsin-stained cells in prostate cancer was higher than that in benign prostatic hyperplasia (P<0.05). Almost all of glandular and cancer cells were stained with PSA antibody. The percentage of alpha-1-antichymotrypsin-stained cells in prostate cancer did not correlate to histologic grade, although alpha-1-antichymotrypsin-stained cells were more widely scattered in high grade tissues. No correlation was found between alpha-1-antichymotrypsin-stained cells and ratio of F/T in the blood of cancer patients. In about 20% of cancer tissues, histiocytes with positive alpha-1-antichymotrypsin staining were found in stroma but not in that of benign prostatic hyperplasia.

CONCLUSIONS

Prostate cancer tissues are shown to have a richer environment of alpha-1-antichymotrypsin than those of benign prostatic hyperplasia. Some cancer tissues contained alpha-1-antichymotrypsin-stained histiocytes. These local events may correlate to a high amount of the bound form among total PSA in the blood of prostate cancer patients.