Chemoprevention for prostatic intraepithelial neoplasia

Persistence of Prostatic Intraepithelial Neoplasia After Effective Chemoprevention of Microscopic Prostate Cancer With Antiandrogen in a Rat Model

PURPOSE

We determined the chemopreventive effect of the antiandrogen bicalutamide (Zeneca Co., Ltd., Osaka, Japan) on Fisher 344 rat prostate carcinogenesis induced by DMAB (3,2'-dimethyl-4-aminobiphenyl) (Nard Co., Ltd., Osaka, Japan). We have previously reported that rat prostate microscopic carcinogenesis in this model was paradoxically enhanced when continuous treatment with bicalutamide was begun 20 weeks after the initiation of DMAB. In the current study we determined whether antiandrogen would promote or suppress the prostate carcinogenesis when administration was begun at a later period of carcinogenesis.

MATERIALS AND METHODS

DMAB at a dose of 50 mg/kg was injected subcutaneously into all animals 10 times at 2-week intervals. To clarify the target lesions of bicalutamide we used 2 control groups (groups 1 and 2). Animals in groups 1 and 2 were autopsied at 60 and 74 weeks, respectively, after the initiation of DMAB. Treatment with bicalutamide began in the 60th week in group 3 rats and continued for 14 weeks. They were sacrificed in the 74th week.

RESULTS

Microscopic cancer was revealed in 27% of group 1 rats and the incidence was increased to 42% in group 2 (statistically not significant). Delayed bicalutamide treatment significantly suppressed the cancer lesion. No cancerous lesion was detected in the ventral or other lobes of the prostate of the rats in group 3. In contrast, bicalutamide did not affect the incidence of PIN. The difference in the incidence of PIN in groups 2 and 3 (84% and 78%, respectively) was not significant.

CONCLUSIONS

The current investigation indicates that, if bicalutamide is started in the later period, it can efficiently eradicate existing microscopic cancer. Despite this suppressive effect on microscopic cancer bicalutamide permits the persistence of PIN. The latter finding suggests that the sensitivity of PIN to antiandrogen might be more complicated than previously recognized.

Effect of androgen deprivation therapy on prostatic intraepithelial neoplasia

There is a marked decrease in the prevalence and extent of high-grade prostatic intraepithelial neoplasia (PIN) in men with prostate cancer after androgen deprivation therapy (ADT) when compared with untreated cases. Basal cell hyperplasia, cytoplasmic clearing, and prominent atrophy of benign acini, with decreased ratio of acini to stroma, accompany this decrease. These findings indicate that the benign and dysplastic prostatic epithelium is androgen dependent. In the normal prostatic epithelium, luminal secretory cells are more sensitive to the absence of androgen than basal cells, and the proliferative cells of high-grade PIN share this androgen sensitivity. The loss of some normal, hyperplastic, and dysplastic epithelial cells with ADT is probably because of acceleration of programmed single-cell death. Remarkably little is known about the comparative effect of different forms of chemical ADT on PIN and cancer, although there appears to be a limited and consistent repertoire of morphologic responses to all forms of this therapy. Conversely, blockade of 5alpha-reductase with finasteride has little or no effect on PIN (or benign epithelium and cancer), unlike other forms of ADT. A recent international consensus conference sponsored by the World Health Organization concluded that identification of high-grade PIN offered the possibility of chemoprevention with hormonal therapy to block the development of clinical cancer. Multiple chemoprevention trials are planned or under way to address this hypothesis.

Chemoprevention for prostatic carcinoma: The role of flutamide in patients with prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (HGPIN) is believed to be a precursor for prostatic adenocarcinoma. The prevalence of prostatic intraepithelial neoplasia (PIN) increases with advancing age. Autopsy studies suggest that PIN may precede the development of prostatic adenocarcinoma by up to 10 years. As such, HGPIN is believed to be a marker of increased risk. This provides a potential opportunity for chemoprevention. Flutamide is 1 agent with potential activity and limited side effects that may act to prevent or delay the onset of prostatic adenocarcinoma in men with HGPIN. A clinical trial is currently underway to assess the efficacy of flutamide.

Inhibitory effect of silibinin on ligand binding to erbB1 and associated mitogenic signaling, growth, and DNA synthesis in advanced human prostate carcinoma cells

We recently showed the inhibitory effect of a flavonoid antioxidant, silymarin, on erbB1-Shc activation in prostate cancer (PCA) DU145 cells. In the present study, we performed more detailed mechanistic and molecular modeling studies with pure silibinin to assess and define its effect on membrane signaling related to erbB1 activation in human PCA LNCaP and DU145 cells. Studies also were performed to establish the biologic responses toward extracellular signal-regulated protein kinase 1/2 (ERK1/2) activation, cell growth, and DNA synthesis. Treatment of serum-starved cells with various doses of silibinin for 2 h followed by (125)I-epidermal growth factor (EGF) showed 30-75% inhibition in ligand binding and 55-95% inhibition in its internalization in LNCaP cells and 20-64% and 12-27% inhibition in these two events in DU145 cells. Time-response studies showed similar effects. In further studies, treatment of serum-starved cultures with silibinin followed by EGF showed strong inhibitory effects on membrane and cytoplasmic signaling molecules. In the case of erbB1 activation, silibinin showed a 58-75% decrease in LNCaP and a 40-100% decrease in DU145 cells at 50, 75, and 100-microg/mL doses. Inhibitory effects of silibinin also were evident on ERK1/2 activation (20-80% inhibition) in both cell lines. Treatment of serum-starved cultures with silibinin resulted in 20-40% and 30-55% inhibition of LNCaP and DU145 cell growth, respectively, at similar doses after 1-3 d of treatment, and 10-50% cell death in both cell lines. Under 10% serum conditions, identical silibinin treatments resulted in 20-65% inhibition of cell growth in LNCaP and DU145 cells but did not cause any cell death. Similar doses of silibinin treatments for 24 h also resulted in 25-60%, 35-40%, and 36-50% inhibition of DNA synthesis when cells were cultured in 10% serum, totally serum starved, and serum starved plus stimulated with EGF, respectively. Molecular modeling of silibinin showed that it is a highly lipophilic compound, suggesting that it interacts with lipid-rich plasma membrane, including binding with erbB1, thereby competing with the EGF-erbB1 interaction. Because the ligand-erbB1 autocrine-loop is causally involved in advanced and androgen-independent PCA, the observed effects of silibinin and its strong lipophilic nature could be useful in developing this agent for the prevention and therapy of PCA.

[Prostatic intraepithelial neoplasm diagnosed with transrectal biopsy. Overall review]

OBJECTIVE

To review the incidence, clinical features and management guidelines for patients with isolated prostatic intraepithelial neoplasia (PIN) diagnosed through prostate transrectal biopsy.

METHODS AND RESULTS

Search in Medline database for papers published between 1990 and 2000 based on the following key words: "prostatic intraepithelial neoplasia and needle biopsy". Nineteen papers fulfilling the search criteria were selected.

CONCLUSIONS

The incidence of PIN in patients seen as part of an early diagnosis program is much lower than in patients attending standard Urology practices. PSA level and ultrasound changes are poor predictors of PIN presence in the biopsy. Prostate cancer incidence in successive biopsies ranges between 13.3% and 100%. None of the clinical variables used to diagnose prostate cancer (DRE, PSA and transrectal ultrasound) can predict accurately the existence of cancer associated to PIN, and only prostatic intraepithelial neoplasia grading is considered a good cancer predictor. There is no consensus with regard to diagnostic and therapeutic management in these patients.

Prevalence and distribution of prostatic intraepithelial neoplasia in salvage radical prostatectomy specimens after radiation therapy

High-grade prostatic intraepithelial neoplasia (PIN) is the most likely precursor of prostate cancer. The effect of radiation therapy (RT) on the prevalence of PIN is uncertain. We studied 86 patients who underwent salvage radical prostatectomy after irradiation failure at the Mayo Clinic. The prevalence, volume, multicentricity, spatial proximity to cancer, and architectural patterns of PIN were evaluated. High-grade PIN was identified in 53 (62%) of 86 prostatectomy specimens. Multiple architectural patterns were usually observed, including tufting in 87%, micropapillary in 66%, cribriform in 38%, and flat in 17%. The mean volume of PIN was 0.12 cm3 (range, 0.05-1.20 cm3). PIN was usually multicentric (70%), with a mean number of PIN foci of 2.5 (range, 1-10). Ninety-four percent of PIN foci were located within 2 mm of invasive cancer. There was no correlation between PIN and pathologic stage, surgical margin, tumor size, DNA ploidy, post-RT Gleason score, time interval from RT to biopsy-proven recurrence, postoperative prostate-specific antigen level, distant metastasis-free survival, or cancer-specific survival. Our examination of salvage radical prostatectomy specimens indicated that the prevalence and extent of PIN appeared to be reduced after RT compared to published studies of prostatectomies without prior RT.

Relation between Bcl-2, cell proliferation, and the androgen receptor status in prostate tissue and precursors of prostate cancer

BACKGROUND

Several recent studies have suggested an important role of the apoptosis suppressing Bcl-2 gene product in prostate cancer progression to an androgen-insensitive disease.

METHODS

Using double-labeling techniques, we have investigated the nuclear androgen receptor (AR) status and the proliferation-associated MIB-1 antigen immunoprofile of Bcl-2 expressing cell types in benign prostate tissue, and high-grade prostatic intraepithelial neoplasia (HGPIN).

RESULTS

In the peripheral and transition zone of the prostate gland, 77% of cycling (MIB-1 positive) epithelial cells coexpressed the Bcl-2 product and were phenotypically basal cells. Bcl-2 immunoreactive basal cells showed markedly reduced levels of the nuclear AR. In the central zone of the gland, increasing Bcl-2 immunoreactivity was detected in secretory luminal cell types that expressed the nuclear AR at low levels. 22% of HGPIN lesions (47 of 216 cases) overexpressed Bcl-2 in secretory luminal cell types, while most of HGPIN lesions (78%) showed the normal Bcl-2 phenotype restricted to the basal cell layer. No correlation was found between the Bcl-2 status and proliferative activity (P > 0.05). Conversely, markedly reduced levels of nuclear AR were detected in HGPIN overexpressing the Bcl-2 gene product.

CONCLUSIONS

The present data suggest that Bcl-2 prevents the proliferation compartment from apoptotic cell death. The aberrant expression of the Bcl-2 gene product in subsets of HGPIN is associated with decreasing levels of the nuclear AR and may confer resistance to the androgen-dependent apoptotic cell death in the dysplastic epithelium.