ELL基因在前列腺癌组织中的表达及其意义

目的分析 ELL基因在人类前列腺癌组织中的表达情况,探讨其在前列腺癌发生发展中的作用.方法收集45例前列腺癌组织、15例良性前列腺增生组织和15例正常前列腺组织,提取总 RNA,应用 qRT-PCR检测 ELL mRNA的表达情况,分析其与前列腺癌分级的关系.结果前列腺癌组织中 ELL mRNA 的表达量明显低于良性前列腺增生组织和正常前列腺组织(P＜0．05),而良性前列腺增生组织与正常前列腺组织间差异无统计学意义.随着前列腺癌Gleason评分的升高,ELL mRNA的表达呈下降趋势(P＜0．05).结论 ELL 基因在前列腺癌组织中呈低表达,其表达与前列腺癌的分级密切相关,提示其可能在前列腺癌的发生发展中发挥重要作用.     

Canine prostatic intraepithelial neoplasia: Is the comparative model relevant?

BACKGROUND: Histologic sections from an archival collection of a veterinary teaching hospital were examined to determine the likelihood of detection of canine high-grade prostatic intraepithelial neoplasms (HGPIN), as a prelude to use of the canine model of prostatic carcinogenesis for chemopreventive strategies. METHODS: Tissue specimens representing clinically healthy (normal) prostate glands, benign prostatic hyperplasia, and prostatic carcinoma were examined in one tissue plane for histological evidence of HGPIN. RESULTS: No histological evidence of HGPIN was detected in 20 normal prostate glands or 95 prostate glands with benign prostatic hyperplasia. Seven of 20 prostatic carcinomas had synchronous HGPIN. CONCLUSIONS: Histological evidence of HGPIN is unlikely to be detected in the healthy or hyperplastic canine prostate gland with the clinically-procured biopsy. This might diminish the usefulness of canine HGPIN in temporal studies of chemoprevention of prostate cancer. HGPIN was found simultaneously with prostatic carcinoma in more than one-third of the carcinomas examined.     

Overexpression of the EphA2 tyrosine kinase in prostate cancer.

BACKGROUND: Molecules that are highly expressed by human prostate cancers may serve as therapeutically relevant targets or tumor markers. Tyrosine kinases are frequently overexpressed in metastatic tumor cells and this prompted us to screen for tyrosine kinases that are overexpressed in prostate cancer cells. METHODS: Expression levels of the EphA2 receptor tyrosine kinase were determined by Western blot analysis in canine and human prostate cancer cell lines and in immortalized and transformed variants of 267B1 prostatic epithelial cells. EphA2 levels in benign human prostate and prostate cancers were also determined in formalin-fixed, paraffin-embedded tissues using immunohistochemical staining. RESULTS: Metastatic prostate cancer cells overexpressed EphA2 by 10-100 fold as compared with non-invasive prostatic epithelial cells. EphA2 immunoreactivity in vivo was also significantly greater in human prostate cancers as compared with benign prostate epithelium. CONCLUSIONS: The EphA2 receptor tyrosine kinase is differentially expressed in human and canine prostate cancer cell lines and overexpressed in human prostate cancers as compared with benign prostate tissues. Metastasis-derived canine prostate carcinoma cell lines overexpress EphA2 and may provide pre-clinical models to further evaluate the role of EphA2 in prostate carcinogenesis. Further investigations are needed to determine the utility of EphA2 as a tumor marker and a novel target in human prostate cancer.     

ATF3在前列腺癌中的表达及意义

目的：探讨激活转录因子3（ATF3）在前列腺癌的表达和意义。方法：采用免疫组化和Western Blot检测正常前列腺、良性前列腺增生及前列腺癌组织中ATF3的表达。结果：ATF3在前列腺癌组织中的表达较正常前列腺组织和前列腺增生组织高（P〈0．05）。ATF3的表达与临床分期、病理分级、是否伴有转移有关。结论：ATF3可能与前列腺癌的发生、发展、侵袭和转移有关，可以作为预测前列腺癌的恶性程度和预后的指标。     

Analysis on chromosome 8 heterozygosity loss in humanprostate carcinoma and high grade prostaticintraepithelial neoplasia

Objective: To analysis the chromosome 8 heterozygosity loss in human prostate carcinoma and high grade prostatic intraepithelial neoplasia. Methods: Pure DNA was obtained from prostate neoplasms and normal tissues by tissue microdissection. The chromosome 8 heterozygosity loss was detected by PCR based micro-satellite polymorphism analysis technique using 14 pairs of microsatellite primers in 10 samples of prostate carcinoma and 10 samples of high grade prostatic intraepithelial neoplasia. Results: There were different frequencies of chromosome 8 heterozygosity loss in 10 samples of prostate carcinoma. 8p23.1-p23.2 and p21-p22 were two high frequency heterozygosity loss regions. Chromosome 8 heterozygosity loss was detected in 3 samples of high grade prostatic intraepithelial neoplasia. Conclusion: There were high frequency heterozygosity loss regions on chromosome 8 of prostate carcinoma, located at 8p23.1-p23.2 and p21-p22. The high grade prostatic intraepithelial neoplasia and prostate carcinoma share     

Immunohistochemical evaluation of prostatic carcinoma before and after radiotherapy

Immunohistochemical procedures were applied to the examination of human tissues for prostatic acid phosphatase. With antisera against purified human prostatic acid phosphatase 173 normal and neoplastic tissues were tested. Samples of 45 non-prostatic carcinomas and their respective normal tissues were negative. Of 4 seminal vesicles studied 2 showed weak reactivity. The epithelial cells of normal prostatic acini were uniformly positive in 25 patients studied. In contrast to normal prostatic tissue the malignant acini in 53 of 55 patients with prostatic carcinoma had variable but positive reactivity. Of 27 patients receiving radiotherapy for adenocarcinoma of the prostate variable staining was observed in the neoplastic cells of 24, 8 to 52 months after treatment. The continued production of prostatic acid phosphatase in the malignant cells after radiotherapy suggests that they also may maintain metabolic activities necessary for growth and metastasis.     

Detection of human papillomavirus in the prostate by polymerase chain reaction and in situ hybridization.

Human papillomavirus is associated with a variety of anogenital lesions, including genital warts, precancers and cancers. In male patients human papillomavirus has been identified in proliferative lesions ranging from penile and urethral warts to penile and prostatic cancers. We examined the association of human papillomavirus deoxyribonucleic acid (DNA) in 84 prostate tissue specimens. Specimens were selected from radical prostatectomy, transurethral resection or transrectal biopsy procedures. A total of 60 formalin-fixed, paraffin-embedded tissues (24 prostate cancer specimens, 16 benign prostatic hyperplasia specimens and 20 normal specimens) was examined by polymerase chain reaction and in situ hybridization. Also, 24 gelatin-embedded frozen prostate cancer specimens were examined for human papillomavirus DNA by polymerase chain reaction. Of the specimens 69 were deemed adequate for polymerase chain reaction analysis, whereas all 60 paraffin-embedded tissues were sufficient for in situ hybridization. Human papillomavirus DNA was detected in 2 normal tissues and 6 prostate cancers using polymerase chain reaction. None of the benign prostatic hyperplasia specimens was positive for human papillomavirus. Human papillomavirus typing results indicated that virus type 16 was present in each of the 8 positive specimens. Confirmation of the presence of human papillomavirus was obtained for 1 of the prostate cancers by nonisotopic in situ hybridization with biotinylated human papillomavirus genomic probes. The low prevalence of human papillomavirus in this study population does not strongly support an etiological role for the virus in prostate cancer.     

Flow cytometric analysis of DNA aneuploidy in adrenal tumors]

Nuclear DNA content of paraffin-embedded tissue from 38 adrenal neoplasms and 9 histologically normal adrenal glands was analyzed using flow cytometry. Histological diagnosis of thirty-eight adrenal neoplasms were 3 adrenocortical carcinomas, 20 adrenocortical adenomas and 15 pheochromocytomas. In 33 cases (87%) of the 38 tumors the determination of DNA ploidy was possible. All 9 control specimens showed DNA diploid pattern in DNA histogram. In adrenocortical neoplasms the incidence of DNA aneuploidy was 0% (0 of 17) in adenomas and 100% (2 of 2) in carcinomas. All 17 adrenocortical adenomas which showed DNA diploid pattern are clinically benign. On the other hand, both 2 cases of adrenocortical carcinoma which showed DNA aneuploidy died within 1 year. These data suggest that DNA aneuploidy may be useful as a prognostic factor in adrenocortical neoplasm. With regard to pheochromocytoma, DNA aneuploidy was detected in 4 of 14 patients (29%). However, all 14 cases were clinically benign. In pheochromocytoma DNA aneuploidy was not found to be correlated with prognosis.     

PAP and PSA in prostatic carcinoma cell lines and aspiration biopsies: relation to hormone sensitivity and to cytological grading

Because a change from hormone-sensitive to hormone-resistant carcinoma of the prostate often occurs concomitantly with genetic changes or as a result of the latter, the markers specific for prostatic tissues might also be affected. We therefore first studied the presence of prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA) in LNCaP and LNCaP-r human prostatic carcinoma cell lines. Since both markers were found in these cell lines, we proceeded to quantitate PAP and PSA in aspiration biopsies from patients with prostate tumors. The amounts of these markers were compared with cytological findings. PAP and PSA were analyzed in the biopsy material from 120 patients using commercial radioimmunoassay (RIA) kits. DNA was determined using Riedel H33258 stain. Cytological grading was performed according to the Uropathological Study Group of Prostatic Carcinoma. Significant correlations were found between PAP/DNA or PSA/DNA values and grade of differentiation of the prostate tumor. In view of earlier reports and the results presented here, the amounts of markers or the protein pattern of tumor tissue may be a useful complement to the morphological findings and for selecting optimal therapy for patients with prostatic tumors.     

High prevalence of human papillomavirus in prostate tissues.

Specific human papillomavirus (HPV) types are associated with benign and malignant lesions of the anogenital region including the prostate gland. Using polymerase chain reaction (PCR) amplification of type-specific HPV sequences, we have assessed the prevalence of HPV DNA in prostate tissue from 88 individuals. Amplified sequences specific for HPV 16 were found in 34 of 56 benign prostatic hyperplasias and in 14 of 27 prostatic carcinomas. In contrast, HPV 18 was identified in only three benign hyperplasias and one carcinoma, all of which also contained HPV 16 DNA. Four of five normal prostates obtained at autopsy had no detectable HPV infection; one contained HPV 16 sequences. No significant difference in the prevalence of HPV DNA is observed between patients with benign disease and those with evidence of malignancy when fragments of surgical material are analyzed. Surgical method (transurethral resection or suprapubic prostatectomy) had no effect on the frequency of HPV detection. The prevalence of HPV DNA in the small number of normal prostates analyzed was not significantly different from that in the surgical samples. The presence of HPV in prostate tissues suggests a possible reservoir for sexual transmission of types with oncogenic potential. A role for the virus in the etiology of prostatic neoplasia remains to be demonstrated.     

Distribution of cathepsin D granules in normal and pathologic conditions in human prostate

Although cathepsin D has been implicated in prostate cancer invasion and metastasis, the distribution of this enzyme in normal human prostate is unknown. We investigated immunohistochemically the distribution of cathepsin D granules in normal prostatic tissues with or without androgen ablation. We also examined the cancer tissues after androgen ablation and the hyperplastic tissues. Changes in the distribution pattern of the larger cathepsin D-positive granules (apoptotic bodies) were observed in the normal prostate as well as in the normal tissue of the anti-androgen-treated cancer specimens. While the apoptotic bodies were denser in the proximal duct of the normal adult prostate, they were more abundant in the normal peripheral acini of the anti-androgen-treated cases. There were few apoptotic bodies in the adenoma tissues, but many in the hormonally treated cancer tissues. These results showed that the distribution pattern and density of cathepsin D granules well reflected the status of the human prostatic cells in relation to age, hormonal environment and hyperplastic or neoplastic change.     

Selection toward diploid cells in prostatic carcinoma derived cell cultures

For elucidation of the growth-regulatory mechanisms in prostatic carcinoma, in vitro investigations on prostatic cell cultures are required. However, one major problem of cell culturing is the selection of particular cell types such that the cell lines representing only some of the features as compared with the tumor of origin. We studied the chromosomal composition of 20 prostatic tissue-derived cell cultures and 12 original (fresh) tissue specimens that were obtained from 13 patients with prostatic adenocarcinoma. Using fluorescence in situ DNA hybridization (FISH), evident clonal abnormalities were detected in 78% of the fresh cancer samples and in 47% of the cultured cancer samples. Of the seven cases revealing clonal abnormalities in the fresh cancer specimen, aneuploidy was detected in only two samples after cell culturing at the earliest passage studied. The aneuploid cell populations in the cultured samples were all lost during progressive subcultivation (after passage 4). Interestingly, by performing FISH on cytogenetic preparations aneuploidy was confined to the interphases, with the metaphases being found to be diploid. This finding indicates that the aneuploid cells have a proliferation disadvantage in cell culture resulting in an overgrowth of diploid cells. © 1996 Wiley-Liss, Inc.     

Expression of a human cell adhesion molecule, MUC18, in prostate cancer cell lines and tissues

BACKGROUND: Over expression of huMUC18, a cell adhesion molecule in the immunoglobulin gene superfamily, causes a non-metastatic human melanoma cell line to become metastatic in a nude mouse system. To determine if MUC18 expression correlates with the malignant progression of prostate cancer, we investigated differential expression of human MUC18 (huMUC18) in normal prostate epithelial cells, prostate cancer cell lines, and prostatic normal and cancer tissues. METHODS: RT-PCR and Western blot analyses were used to analyze the expression of MUC18 mRNA and protein in four human prostate cancer cell lines, cultured primary normal prostate epithelial cells, normal prostate and malignant prostate tissues. Immunohistochemistry was used to determine the expression of MUC18 antigen in prostatic tissues at different stages of malignancy. RESULTS: Human MUC18 mRNA and protein was expressed in three different prostate cancer cell lines (TSU-PR1, DU145, and PC-3), but not in one prostate cancer cell line (LNCaP.FGC). HuMUC18 protein was also expressed at high levels in extracts prepared from tissue sample sections containing high grade prostatic intraepithelial neoplasia (PIN), but weakly expressed in extracts prepared from either cultured primary normal prostatic epithelial cells or the normal prostate gland. Immunohistochemical analysis showed that huMUC18 was expressed at higher levels in the epithelial cells of high-grade PIN and prostatic carcinomas and in cells of a lymph node metastasis compared to that in normal or benign hyperplastic epithelium (BPH). CONCLUSIONS: We therefore conclude that MUC18 is expressed at higher levels in pre-malignant and malignant prostatic epithelium, including metastasis. We suggest that over-expression of MUC18 may be a new marker of human prostate cancer and also implicates its possible role in development and progression of prostate cancer.     

Differential expression of specific cytokeratin polypeptides in the basal and luminal epithelia of the human prostate.

The purpose of the present study was to identify cytokeratin polypeptides that are specifically associated with the basal and luminal epithelia of the human prostate. This aim was accomplished by immunohistochemical and immunoblot analysis of human prostate using cytokeratin-specific monoclonal antibodies. In immunohistochemical studies, monoclonal anticytokeratin 8.12 exhibited immunoreactivity with the basal, but not luminal, epithelial cells of fetal, juvenile, normal adult, and hyperplastic prostate. The 8.12 antibody did not stain prostate cancer tissues. Epithelia of 30 and 36 week fetal prostate contained only basal cells whereas both luminal and basal cells were noted in 7 month and 1 year old juvenile prostate. This finding suggests a stem cell function for the prostatic basal cells. Immunoblot analysis of proteins separated by two-dimensional electrophoresis showed that cytokeratins 5 and 15 were basal-cell-specific cytokeratins that were absent from prostatic carcinoma while cytokeratins 8 and 18 appear to be luminal-cell-specific. These results indicate that antibodies to specific cytokeratin polypeptides can be used not only to differentiate between prostatic basal and luminal cells but also to study the biological processes of prostatic organogenesis and carcinogenesis.     

Cytochemistry and biochemistry of acid phosphatases VII: Immunohistochemistry of canine prostatic acid phosphatase

Acid phosphatase (E.C. 3.1.3.2.) has been isolated from canine prostatic gland homogenates by gel permeation chromatography (AcA34 or G150), by affinity chromatography (con A-Sepharose), or by using fluid phase liquid chromatography (FPLC) using Superose 12 and Mono P columns. Acid phosphatase-enriched fractions were submitted to analytical SDS-PAGE or to analytical isoelectric focusing. A protein with a molecular weight of 30 kD (on SDS gels) was used for immunization of rabbits. The antiserum produced was cross-reactive with prostatic acid phosphatase (canine and human) as shown by immunoblotting. When applied to paraffin or plastic sections of normal canine prostate, a positive immunoreaction was found exclusively in the secretory cells. In experimentally altered glands (castration and/or hormone treatment), a varying pattern of immunoreactive cells was found. In canine prostatic carcinomas, intensively reacting cell clusters were found along with nonreactive cells. The antiserum was also slightly cross-reactive with the respective human antigen, but the cross-reactivity of an antiserum prepared against human prostatic secretory acid phosphatase with canine prostatic acid phosphatase was far more pronounced.     

Epidermal growth factor modulates the expression of vascular endothelial growth factor in the human prostate

The growth and dissemination of tumors in the body has been associated with angiogenesis. Vascular endothelial growth factor (VEGF) is an angiogenic factor that stimulates endothelial cell growth and enhances vascular permeability. VEGF exerts its action by binding to specific cell surface receptors. Three receptors, VEGFR-1 (flt-1), VEGFR-2 (flk-1), and VEGFR-3 (flt-4) have been identified. Very little information on the coordinated expression of VEGF and its receptors in normal prostate, benign prostatic hyperplasia (BPH), and prostate carcinoma is available. Therefore, we examined the immunohistochemical localization of VEGF and its receptors in tissues derived from normal human prostate, BPH, and prostatic carcinoma. Immunostaining for VEGF was absent in the normal prostate. Epithelium lining the glands of prostate derived from patients with BPH exhibited strong immunostaining. The intensity of staining was relatively less in prostate carcinoma. It is interesting that VEGFR-1 and VEGFR-3 were strongly expressed in both stromal and epithelial tissues in normal prostate, BPH, and carcinoma. In comparison, VEGFR-2 was not localized to normal prostate and its expression in the stroma of BPH and epithelium of carcinoma was very weak. Because progression of prostate cancer is accompanied by altered expression of epidermal growth factor (EGF) and its receptor (EGFR) in malignant cells, we investigated the effect of EGF on VEGF gene expression by Northern blot analysis in 2 human prostate cancer cell lines that express EGFR. EGF greatly enhanced the expression of VEGF messenger RNA in DU145 and PC3 cell lines in a dose-dependent manner. The EGF induction of VEGF gene expression suggests a mechanism by which angiogenesis could be accelerated in BPH and prostate carcinoma.     

Cathepsin D cytosolic assay and immunohistochemical quantification in human prostate tumors

We quantified cathepsin D by immunoradiometric assay (IRMA) and quantitative immunohistochemistry in fifteen human prostate cancers, seventeen BPH, and nine normal prostates. The cytosolic cathepsin D concentration was higher in prostatic carcinoma (mean: 31.5 pmol/mg cytosol proteins; range: 10.2-66.2) than in normal prostate (16.0 pmol/mg cytosol proteins; 7.2-25.5; P = 0.01). Prostatic hyperplasia showed intermediate values (20.2 pmol/mg cytosol proteins; 7.6-33.9). Immunostaining of cathepsin D and prostatic acid phosphatase on serial frozen sections of prostate tissues was only observed in glandular epithelial cells. Immunostaining was quantified by computer-assisted image analysis as an quantitative immuno-cytochemical score (QIC score) expressed in arbitrary units (A.U.). QIC scores for cathepsin D were dispersed and had a tendency to be higher in benign prostatic hyperplasia (mean: 178.3 A.U.; range: 95-297) compared to normal prostate (85.2 A.U.; 2-173 P < 0.01) and prostatic carcinoma (90.0 A.U.; 21-179 P = 0.0002). Prostatic cathepsin D levels in cytosols or immunostaining sections were independent of other clinicobiological parameters. © 1994 Wiley-Liss, Inc.     

Role of canine basal cells in postnatal prostatic development, induction of hyperplasia, and sex hormone-stimulated growth; and the ductal origin of carcinoma

BACKGROUND: The canine prostate has often been proposed as a model for abnormal growth of the human gland. Hyperplasia of the prostate is common in aging men and has been estimated to be present in 100% of old intact dogs. While prostatic carcinoma is common in older men, it appears to be rare in dogs and unlike the disease in humans, it occurs with relatively high frequency in castrated animals. Since basal cells are thought to be key participants in normal and abnormal growth of the human gland, we used immunohistochemistry to investigate the role that they may play in canine prostatic development, the evolution of hyperplasia and carcinoma, and the effects of sex hormones on these cells. METHODS: Prostate specimens were obtained at autopsy from seven sexually immature dogs, autopsy and biopsy samples from 14 sexually mature intact animals, from four castrates, and from19 dogs with prostatic carcinoma. In addition, we also studied the prostates from two intact dogs treated with 5alpha-dihydrotestosterone (DHT) for 6 months and two castrated dogs that were subsequently treated with 5alpha-androstane-3alpha diol and estradiol-17alpha, as well as specimens from two sexually ablated animals given DHT for 2 weeks. All specimens were immunostained for high molecular weight cytokeratin (HMC), pancytokeratin, androgen receptor (AR), and the proliferative marker KI-67. RESULTS: We find that basal cells are the major proliferative cell type in the neonatal and adult canine prostate and that the expression of HMC staining, which defines these cells, may be regulated by androgens. In the adult gland, ductal basal cells formed a contiguous layer, whereas those lining acini were discontinuous. Populations of both basal cell types were variably AR positive, but while HMC immunostaining was abolished in acinar cells following long-term castration, staining remained in ductal cell counterparts. Paralleling the histological development of hyperplasia, the acinar basal cell population increased with age and were the major cell type that expressed KI-67. In contrast, ductal basal cell populations did not expand in the prostates of older dogs and were seldom positively stained for KI-67. The numbers of HMC and KI-67-stained acinar basal cells were dramatically increased in the prostates of intact dogs treated with DHT when compared with glands of untreated controls. This was not the case with ductal basal cells. Androgens given alone or together with estrogen to castrated dogs induced widespread HMC and KI-67 immunostaining in both populations of basal cells. In addition, our results indicate that the majority of canine prostatic carcinomas likely arise exclusively from ductal epithelium. Only one of the 19 cases of carcinoma contained cells that expressed AR, which suggests that androgens may not be required for the initiation or progression of these cancers. CONCLUSIONS: Our findings indicate that two biologically distinct populations of basal cells may exist in the canine prostate. In this regard, the age-related expansion of proliferating acinar basal cell populations, probably mediated by sex steroids, is a key factor in the pathogenesis of canine prostatic hyperplasia. Additionally, we find that prostatic carcinoma in the dog likely arises from ductal cells. Taken together, these findings may indicate that canine acinar basal cells and ductal epithelium have separate susceptibilities to factors that promote hyperplastic or neoplastic development.     

Role of canine basal cells in prostatic post natal development, induction of hyperplasia, sex hormone-stimulated growth; and the ductal origin of carcinoma

BACKGROUND: The canine prostate has often been proposed as a model for abnormal growth of the human gland. Hyperplasia of the prostate is common in aging men and has been estimated to be present in 100% of old intact dogs. While prostatic carcinoma is common in older men it appears to be rare in dogs and unlike the disease in humans it occurs with relatively high frequency in castrated animals. Since basal cells are thought to be key participants in normal and abnormal growth of the human gland, we used immunohistochemistry to investigate the role that they may play in canine prostatic development, the evolution of hyperplasia and carcinoma, and the effects of sex hormones on these cells. METHODS: Prostate specimens were obtained at autopsy from seven sexually immature dogs, autopsy and biopsy samples from 14 sexually mature intact animals, from four castrates, and from 19 dogs with prostatic carcinoma. In addition, we also studied the prostates from two intact dogs treated with 5 alpha-dihydrotestosterone (DHT) for 6 months and two castrated dogs that were subsequently treated with 5 alpha-androstane-3 alpha diol and estradiol-17 alpha as well as specimens from two sexually ablated animals given DHT for 2 weeks. All specimens were immunostained for high molecular weight cytokeratin (HMC), Pancytokeratin, androgen receptor (AR), and the proliferative marker KI-67. RESULTS: We find that basal cells are the major proliferative cell type in the neonatal and adult canine prostate and that the expression of HMC staining, which defines these cells, may be regulated by androgens. In the adult gland, ductal basal cells formed a contiguous layer whereas those lining acini were discontinuous. Populations of both basal cell types were variably AR positive but while HMC immunostaining was abolished in acinar cells following long-term castration, staining remained in ductal cell counterparts. Paralleling the histological development of hyperplasia, the acinar basal cell population increased with age and were the major cell type that expressed KI-67. In contrast, ductal basal cell populations did not expand in the prostates of older dogs and were seldom positively stained for KI-67. The numbers of HMC and KI-67-stained acinar basal cells were dramatically increased in the prostates of intact dogs treated with DHT when compared with glands of untreated controls. This was not the case with ductal basal cells. Androgens given alone or together with estrogen to castrated dogs induced widespread HMC and KI-67 immunostaining in both populations of basal cells. In addition, our results indicate that the majority of canine prostatic carcinomas likely arise exclusively from ductal epithelium. Only one of the 19 cases of carcinoma contained cells that expressed AR which suggests that androgens may not be required for the initiation or progression of these cancers. CONCLUSIONS: Our findings indicate that two biologically distinct populations of basal cells may exist in the canine prostate. In this regard the age-related expansion of proliferating acinar basal cell populations, probably mediated by sex steroids, is a key factor in the pathogenesis of canine prostatic hyperplasia. Additionally we find that prostatic carcinoma in the dog likely arises from ductal cells. Taken together these findings may indicate that canine acinar basal cells and ductal epithelium have separate susceptibilities to factors that promote hyperplastic or neoplastic development. Prostate 47:149-163, 2001.