Establishing the distribution of satellite lesions in intermediate- and high-risk prostate cancer: implications for focused radiotherapy.

BACKGROUND: In focused radiotherapy for prostate cancer (PC), a full dose of radiation is delivered to the index lesion while reduced dose is delivered to the remaining prostate to reduce morbidity. As PC is commonly multifocal, we investigated whether baseline clinical characteristics or multiparametric magnetic resonance imaging (mpMRI) may be useful to predict the actual pathologic distribution of PC in men with intermediate- or high-risk PC, which may better inform how to deliver focused radiotherapy. METHODS: A retrospective single-institutional study was performed on 71 consecutive men with clinically localized, intermediate- or high-risk PC who underwent mpMRI followed by radical prostatectomy (RP) from January 2012 to December 2012. Logistic regression analysis was performed to evaluate preoperative predictors for satellite lesions. Performance characteristics of mpMRI to detect satellite lesions and the extent of prostate disease (one hemi-gland vs both) were also evaluated. RESULTS: In all, 50.7% had satellite lesions on mpMRI. On RP specimen analysis, 66.2% had satellite lesions and 55.3% of these satellite lesions had pathologic Gleason score (pGS)⩾3+4. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for mpMRI detecting a satellite lesion being present in the RP specimen were 59.6%, 66.7%, 77.8%, 45.7% and 62.0%, respectively. The presence of MRI satellite lesions was the only preoperative predictor significantly associated with finding satellite lesions on final pathology (hazard ratio (HR), 2.95, P=0.040). There was agreement in 76.1% of the entire cohort for unilateral vs bilateral disease when incorporating both biopsy and mpMRI information and comparing with the RP specimen. CONCLUSIONS: In intermediate risk or greater PC, only the presence of mpMRI satellite lesions could predict for pathologic satellite lesions. While combining biopsy and mpMRI information may improve preoperative disease localization, the relatively high incidence of bilateral hemi-gland involvement with pGS ⩾7 satellite lesions makes it challenging to appropriately select men eligible for hemi-gland therapy.

Novel technique for characterizing prostate cancer utilizing MRI restriction spectrum imaging: proof of principle and initial clinical experience with extraprostatic extension.

BACKGROUND: Standard magnetic resonance imaging (MRI) of the prostate lacks sensitivity in the diagnosis and staging of prostate cancer (PCa). To improve the operating characteristics of prostate MRI in the detection and characterization of PCa, we developed a novel, enhanced MRI diffusion technique using restriction spectrum imaging (RSI-MRI). METHODS: We compared the efficacy of our novel RSI-MRI technique with standard MRI for detecting extraprostatic extension (EPE) among 28 PCa patients who underwent MRI and RSI-MRI prior to radical prostatectomy, 10 with histologically proven pT3 disease. RSI cellularity maps isolating the restricted isotropic water fraction were reconstructed based on all b-values and then standardized across the sample with z-score maps. Distortion correction of the RSI maps was performed using the alternating phase-encode technique. RESULTS: 27 patients were evaluated, excluding one patient where distortion could not be performed. Preoperative standard MRI correctly identified extraprostatic the extension in two of the nine pT3 (22%) patients, whereas RSI-MRI identified EPE in eight of nine (89%) patients. RSI-MRI correctly identified pT2 disease in the remaining 18 patients. CONCLUSIONS: In this proof of principle study, we conclude that our novel RSI-MRI technology is feasible and shows promise for substantially improving PCa imaging. Further translational studies of prostate RSI-MRI in the diagnosis and staging of PCa are indicated.

Discovery of new markers of cancer through serial analysis of gene expression: prostate stem cell antigen is overexpressed in pancreatic adenocarcinoma.

Serial analysis of gene expression (SAGE) can be used to quantify gene expression in human tissues. Comparison of gene expression levels in neoplastic tissues with those seen in nonneoplastic tissues can, in turn, identify novel tumor markers. Such markers are urgently needed for highly lethal cancers like pancreatic adenocarcinoma, which typically presents at an incurable, advanced stage. The results of SAGE analyses of a large number of neoplastic and nonneoplastic tissues are now available online, facilitating the rapid identification of novel tumor markers. We searched an online SAGE database to identify genes preferentially expressed in pancreatic cancers as compared with normal tissues. SAGE libraries derived from pancreatic adenocarcinomas were compared with SAGE libraries derived from nonneoplastic tissues. Three promising tags were identified. Two of these tags corresponded to genes (lipocalin and trefoil factor 2) previously shown to be overexpressed in pancreatic carcinoma, whereas the third tag corresponded to prostate stem cell antigen (PSCA), a recently discovered gene thought to be largely restricted to prostatic basal cells and prostatic adenocarcinomas. PSCA was expressed in four of the six pancreatic cancer SAGE libraries, but not in the libraries derived from normal pancreatic ductal cells. We confirmed the overexpression of the PSCA mRNA transcript in 14 of 19 pancreatic cancer cell lines by reverse transcription-PCR, and using immunohistochemistry, we demonstrated PSCA protein overexpression in 36 of 60 (60%) primary pancreatic adenocarcinomas. In 59 of 60 cases, the adjacent nonneoplastic pancreas did not label for PSCA. PSCA is a novel tumor marker for pancreatic carcinoma that has potential diagnostic and therapeutic implications. These results establish the validity of analyses of SAGE databases to identify novel tumor markers.

Prostate stem cell antigen is overexpressed in human transitional cell carcinoma.

Prostate stem cell antigen (PSCA), a homologue of the Ly-6/Thy-1 family of cell surface antigens, is expressed by a majority of human prostate cancers and is a promising target for prostate cancer immunotherapy. In addition to its expression in normal and malignant prostate, we recently reported that PSCA is expressed at low levels in the transitional epithelium of normal bladder. In the present study, we compared the expression of PSCA in normal and malignant urothelial tissues to assess its potential as an immunotherapeutic target in transitional cell carcinoma (TCC). Immunohistochemical analysis of PSCA protein expression was performed on tissue sections from 32 normal bladder specimens, as well as 11 cases of low-grade transitional cell dysplasia, 21 cases of carcinoma in situ (CIS), 38 superficial transitional cell tumors (STCC, stages T(a)-T(1)), 65 muscle-invasive TCCs (ITCCs, stages T(2)-T(4)), and 7 bladder cancer metastases. The level of PSCA protein expression was scored semiquantitatively by assessing both the intensity and frequency (i.e., percentage of positive tumor cells) of staining. We also examined PSCA mRNA expression in a representative sample of normal and malignant human transitional cell tissues. In normal bladder, PSCA immunostaining was weak and confined almost exclusively to the superficial umbrella cell layer. Staining in CIS and STCC was more intense and uniform than that seen in normal bladder epithelium (P < 0.001), with staining detected in 21 (100%) of 21 cases of CIS and 37 (97%) of 38 superficial tumors. PSCA protein was also detected in 42 (65%) of 65 of muscle-invasive and 4 (57%) of 7 metastatic cancers, with the highest levels of PSCA expression (i.e., moderate-strong staining in >50% of tumor cells) seen in 32% of invasive and 43% of metastatic samples. Higher levels of PSCA expression correlated with increasing tumor grade for both STCCs and ITCCs (P < 0.001). Northern blot analysis confirmed the immunohistochemical data, showing a dramatic increase in PSCA mRNA expression in two of five muscle-invasive transitional cell tumors when compared with normal samples. Confocal microscopy demonstrated that PSCA expression in TCC is confined to the cell surface. These data demonstrate that PSCA is overexpressed in a majority of human TCCs, particularly CIS and superficial tumors, and may be a useful target for bladder cancer diagnosis and therapy.

Alternative pathways to prostate carcinoma activate prostate stem cell antigen expression.

Prostate Stem Cell Antigen (PSCA) is a glycosylphosphatidylinositol-anchored cell surface protein that is expressed in normal human prostate and overexpressed in human prostate cancers. To test whether different pathways that generate prostate cancer would affect PSCA expression, a murine model system was developed. Monoclonal antibodies were generated against murine PSCA (mPSCA). mPSCA is expressed on approximately 20% of cells in normal prostate epithelium, and this number decreases with increasing age. In the transgenic adenocarcinoma of the mouse prostate (TRAMP) model of prostate cancer, tumors develop between 19 and 25 weeks of age. Murine PSCA was strongly expressed on approximately 60% of the cells of TRAMP tumors, at an age where the number of PSCA+ cells and the level of expression of PSCA is very low in the normal prostate. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) +/- mice develop a number of different cancers, including prostate cancer. The incidence of prostate cancer is low and occurs after a relatively long latency. Fluorescence-activated cell sorter analysis of prostatic tissue from 11-18-month-old PTEN +/- mice showed elevated numbers of PSCA+ cells in the prostate, and immunohistochemical analysis showed high mPSCA expression in the tumors of these mice. Together, these results show that two distinct mechanisms of carcinogenesis lead to expression of a common target antigen.

Anti-PSCA mAbs inhibit tumor growth and metastasis formation and prolong the survival of mice bearing human prostate cancer xenografts.

Prostate stem-cell antigen (PSCA) is a cell-surface antigen expressed in normal prostate and overexpressed in prostate cancer tissues. PSCA expression is detected in over 80% of patients with local disease, and elevated levels of PSCA are correlated with increased tumor stage, grade, and androgen independence, including high expression in bone metastases. We evaluated the therapeutic efficacy of anti-PSCA mAbs in human prostate cancer xenograft mouse models by using the androgen-dependent LAPC-9 xenograft and the androgen-independent recombinant cell line PC3-PSCA. Two different anti-PSCA mAbs, 1G8 (IgG1kappa) and 3C5 (IgG2akappa), inhibited formation of s.c. and orthotopic xenograft tumors in a dose-dependent manner. Furthermore, administration of anti-PSCA mAbs led to retardation of established orthotopic tumor growth and inhibition of metastasis to distant sites, resulting in a significant prolongation in the survival of tumor-bearing mice. These studies suggest PSCA as an attractive target for immunotherapy and demonstrate the therapeutic potential of anti-PSCA mAbs for the treatment of local and metastatic prostate cancer.

Preoperative prostate needle biopsy p27 correlates with subsequent radical prostatectomy p27, Gleason grade and pathological stage.

PURPOSE: Loss of p27 protein expression in radical prostatectomy specimens has been shown to be an adverse prognostic factor in patients with clinically localized prostate cancer. To our knowledge no studies have examined p27 expression in prostate needle biopsies. To test the potential predictive power of p27 in prostate biopsies we compared p27 expression in preoperative biopsies and matched prostatectomy specimens of patients with clinically localized prostate cancer. MATERIALS AND METHODS: Matched biopsies and radical prostatectomy specimens from 44 patients were examined. Mean followup was 22.7 months (range 1 to 46). Tumors expressing less than 30% positive nuclei were classified as low expressors and tumors expressing greater than 30% positive nuclei were classified as high expressors of p27 protein. RESULTS: Expression of p27 in prostate biopsies correlated significantly with subsequent p27 expression in radical prostatectomy specimens (p = 0.002). Sensitivity and specificity of biopsy p27 for predicting subsequent prostatectomy p27 were 87.5% and 88.9%, respectively (p <0.001). Univariate analysis showed that low expression of p27 in the biopsy correlated significantly with biopsy and prostatectomy Gleason score (p = 0.000 and 0.001, respectively), and final pathological stage (p = 0.028). Despite the small sample size and short followup, 36.4% of patients with low p27 expression had a biochemical recurrence compared to only 12.1% with high expression (hazards ratio 3.56). In addition, Kaplan-Meier analysis suggested that low p27 expression in prostate biopsies may be associated with a shorter time to recurrence, although this did not reach statistical significance (p = 0.081). CONCLUSIONS: Expression of p27 in prostate biopsies can be used to predict the degree of expression in radical prostatectomy specimens. As loss of p27 protein expression in prostatectomy specimens has been shown to correlate with biochemical recurrence and shortened prostate specific survival, these results suggest that biopsy p27 may help identify high risk patients preoperatively.

Prostate stem cell antigen (PSCA) expression increases with high gleason score, advanced stage and bone metastasis in prostate cancer.

Prostate stem cell antigen (PSCA) is a recently defined homologue of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. PSCA mRNA is expressed in the basal cells of normal prostate and in more than 80% of prostate cancers. The purpose of the present study was to examine PSCA protein expression in clinical specimens of human prostate cancer. Five monoclonal antibodies were raised against a PSCA-GST fusion protein and screened for their ability to recognize PSCA on the cell surface of human prostate cancer cells. Immunohistochemical analysis of PSCA expression was performed on paraffin-embedded sections from 25 normal tissues, 112 primary prostate cancers and nine prostate cancers metastatic to bone. The level of PSCA expression in prostate tumors was quantified and compared with expression in adjacent normal glands. The antibodies detect PSCA expression on the cell surface of normal and malignant prostate cells and distinguish three extracellular epitopes on PSCA. Prostate and transitional epithelium reacted strongly with PSCA. PSCA staining was also seen in placental trophoblasts, renal collecting ducts and neuroendocrine cells in the stomach and colon. All other normal tissues tested were negative. PSCA protein expression was identified in 105/112 (94%) primary prostate tumors and 9/9 (100%) bone metastases. The level of PSCA expression increased with higher Gleason score (P=0.016), higher tumor stage (P=0.010) and progression to androgen-independence (P=0. 021). Intense, homogeneous staining was seen in all nine bone metastases. PSCA is a cell surface protein with limited expression in extraprostatic normal tissues. PSCA expression correlates with tumor stage, grade and androgen independence and may have prognostic utility. Because expression on the surface of prostate cancer cells increases with tumor progression, PSCA may be a useful molecular target in advanced prostate cancer.

Quality of life outcomes after brachytherapy for early stage prostate cancer.

PURPOSE: We compare general and disease specific health related quality of life in men undergoing brachytherapy for early stage prostate cancer to those undergoing radical prostatectomy and age matched healthy controls. MATERIALS AND METHODS: Cohorts consisted of 48 men treated with brachytherapy with and without pretreatment external beam radiation therapy (brachytherapy group), 74 who underwent radical prostatectomy (prostatectomy group) and age matched healthy controls from the literature. The RAND 36-item general health survey, University of California Los Angeles Prostate Cancer Index, American Urological Association symptom index, validated Cancer Interference with Life and Family Scales, and sociodemographic and co-morbidity questionnaires were completed 3 to 17 months after treatment. RESULTS: General health related quality of life did not differ greatly among the 3 groups. Urinary function (leakage) was worse in the brachytherapy group than in controls but better than in the prostatectomy group. Brachytherapy group patients had more irritative urinary symptoms and worse bowel function than controls. Sexual function and bother were worse in prostatectomy and brachytherapy groups than in healthy controls. Physical function, bodily pain, urinary function, and bother and American Urological Association symptom index scores improved with time after brachytherapy. Patients who underwent brachytherapy after external beam radiation performed worse in all general and disease specific health related quality of life domains compared to those who did not undergo pretreatment radiation therapy. CONCLUSIONS: At an average of 7.5 months after treatment the general health related quality of life of patients undergoing brachytherapy with and without pretreatment external beam radiation was similar to age matched controls, although urinary, bowel and sexual problems were reported. These problems appeared to improve during the first year after treatment. Much of the impairment in disease specific health related quality of life among patients undergoing brachytherapy may be attributed to pretreatment radiation.

Coamplification of prostate stem cell antigen (PSCA) and MYC in locally advanced prostate cancer.

Gain of sequences on chromosome arm 8q is a common feature of prostate cancer that may correlate with metastatic and androgen-independent progression. The target gene(s) for this gain is not known, although MYC is amplified in a subset of advanced tumors and is one potential candidate. Prostate stem cell antigen (PSCA) is a prostate-specific cell surface protein that maps to chromosome region 8q24.2 and is overexpressed in prostate cancer. Our aim in this study was to test the hypothesis that PSCA overexpression may result from overrepresentation of chromosome arm 8q. Twenty locally advanced prostate cancers were analyzed by dual-probe fluorescence in situ hybridization (FISH) for alterations of MYC and PSCA. Extra copies of MYC were found in 12/20 (60%) tumors, including 5 (25%) with simple gain (no increase in MYC copy number relative to the chromosome 8 centromere) and 7 (35%) with an additional increase (AI or overrepresentation) in MYC copy number relative to the centromere. In the five cases with simple gain of MYC, there was a concomitant gain of PSCA. PSCA was overrepresented in 5/7 (71%) cases with AI of MYC. Immunohistochemical staining of the 20 tumors with monoclonal antibodies specific for PSCA showed a high degree of correlation between PSCA gene overrepresentation and protein overexpression. Four of 5 tumors with AI of PSCA overexpressed PSCA protein, compared with only 2/15 tumors with a normal PSCA copy number or simple gain of PSCA (P = 0.014). These results demonstrate that PSCA is co-overrepresented with MYC in a majority of cases, but may not be a necessary part of the 8q amplicon. PSCA protein overexpression can result from AI of PSCA and might be useful as a cell surface marker on prostate cancer cells with 8q overrepresentation. Genes Chromosomes Cancer 27:95-103, 2000.

Evidence for clonal outgrowth of androgen-independent prostate cancer cells from androgen-dependent tumors through a two-step process.

Prostate cancers require androgen for growth but progress to an androgen-independent stage under the selective pressure of androgen ablation therapy. Here we describe a novel human prostate cancer xenograft (LAPC-9) propagated by serial passage in male severe combined immunodeficient mice that expresses prostate-specific antigen and wild-type androgen receptor. In response to castration, LAPC-9 cells undergo growth arrest and persist in a dormant, androgen-responsive state for at least 6 months. After prolonged periods of androgen deprivation, spontaneous androgen-independent outgrowths develop. Thus, prostate cancers progress to androgen independence through two distinct stages, initially escaping dependence on androgen for survival and, subsequently, for growth. Through the use of serial dilution and fluctuation analysis, we provide evidence that the latter stage of androgen independence results from clonal expansion of androgen-independent cells that are present at a frequency of about 1 per 10(5)-10(6) androgen-dependent cells. We conclude that prostate cancers contain heterogeneous mixtures of cells that vary in their dependence on androgen for growth and survival and that treatment with antiandrogen therapy provides selective pressure and alters the relative frequency of these cells, thereby leading to outgrowths of androgen-independent cancers.

Caveolin expression is decreased following androgen deprivation in human prostate cancer cell lines.

BACKGROUND: Increased expression of caveolin has been associated with prostate cancer progression. In a mouse reconstitution model of prostate cancer, expression of caveolin was inversely related to androgen sensitivity: androgen independent clones had high caveolin expression; low caveolin expression was associated with sensitivity to androgen withdrawal. In contrast, several independent observations support the hypothesis that caveolin functions as a tumor suppressor. METHODS: Caveolin expression was studied by Western blot analysis and/or immunohistochemistry in three androgen-sensitive human prostate cancer cell lines LNCaP, LAPC-4 and LAPC-9, and following acute and chronic androgen deprivation, and in benign prostate epithelial cells. Expression of caveolin, androgen receptor (AR) and prostate specific antigen (PSA) was also examined after reintroduction of androgen. RESULTS: LNCaP grown continuously under androgen-depleted conditions for 6 to 42 months produced several androgen-independent and tumorigenic clones: tumors formed in 13/15 castrate and 7/15 intact male athymic nu/nu mice, but no tumors formed in wildtype LNCaP-bearing animals. Caveolin expression was decreased in every androgen-deprived LNCaP clone and following 150 days of androgen deprivation in LAPC-4. Caveolin expression by LAPC-9 was very low. Following exposure to dihydrotestosterone in vitro, caveolin and PSA expression increased within three days in the androgen-deprived clones of LNCaP. Benign prostate epithelial cells have high caveolin expression. CONCLUSIONS: Unlike the mouse reconstitution model of prostate cancer, the pattern of caveolin expression in benign prostatic epithelium and androgen-sensitive human prostate cancer is consistent with tumor suppressive activity.

Target antigens for prostate cancer immunotherapy.

The detection and treatment of prostate cancer has been markedly improved by the use of Prostate-Specific Antigen (PSA) as a serological biomarker for disease. However, even after surgical intervention and hormone ablation therapy, a significant proportion of patients progress to advanced metastatic disease, for which there is no cure. An important goal has become the identification of antigens in advanced stage prostate cancer that represent targets for therapy. Recently, great progress has been made to utilize immunological therapies to treat cancer. Monoclonal antibody therapy has been successfully approved for the treatment of breast cancer and B-cell lymphoma, and multiple clinical trails are currently in progress in a variety of cancers, including prostate cancer. Pre-clinical and clinical studies are also underway to evaluate cancer vaccine approaches directed against antigens that are highly expressed in prostate and other cancers. This article describes several target antigens expressed in prostate cancer and immunological approaches directed against them that may be effective for treating prostate cancer patients.

Inactivation of the tumor suppressor PTEN/MMAC1 in advanced human prostate cancer through loss of expression.

The recently identified PTEN/MMAC1 gene is a candidate tumor suppressor implicated in multiple tumor types based on mutations or homozygous deletions of the gene in certain human cancers. No studies of PTEN/MMAC1 mRNA or protein expression in cancer cells have been reported, primarily because of significant numbers of normal cells contaminating most tumor samples and because of the lack of antibody reagents. We examined PTEN/MMAC1 in advanced prostate cancer for gene mutations or abnormalities in expression by using a series of recently derived xenografts free of normal human cells and a PTEN/MMAC1-specific antibody. Only 1 of 10 tumors contained a homozygous deletion of PTEN/MMAC1, and no mutations were detected in the entire coding region of the remaining nine xenografts. However, five of these showed reduced or absent PTEN/MMAC1 expression by Northern analysis and reverse transcription-PCR of mRNA. PTEN/MMAC1 mRNA expression was restored in nonexpressing prostate cancer cells by in vitro treatment with the demethylating agent 5-azadeoxycytidine. Alterations in PTEN/MMAC1 expression were confirmed at the protein level by immunoblot analysis, and immunohistochemical studies show that the endogenous wild-type PTEN/MMAC1 protein is localized exclusively in the cytoplasm. These results demonstrate that loss of PTEN/MMAC1 expression occurs frequently in advanced prostate cancer.

Prostate stem cell antigen: a cell surface marker overexpressed in prostate cancer.

The identification of cell surface antigens is critical to the development of new diagnostic and therapeutic modalities for the management of prostate cancer. Prostate stem cell antigen (PSCA) is a prostate-specific gene with 30% homology to stem cell antigen 2, a member of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. PSCA encodes a 123-aa protein with an amino-terminal signal sequence, a carboxyl-terminal GPI-anchoring sequence, and multiple N-glycosylation sites. PSCA mRNA expression is prostate-specific in normal male tissues and is highly up-regulated in both androgen-dependent and -independent prostate cancer xenografts. In situ mRNA analysis localizes PSCA expression in normal prostate to the basal cell epithelium, the putative stem cell compartment of the prostate. There is moderate to strong PSCA expression in 111 of 126 (88%) prostate cancer specimens examined by in situ analysis, including high-grade prostatic intraepithelial neoplasia and androgen-dependent and androgen-independent tumors. Flow cytometric analysis demonstrates that PSCA is expressed predominantly on the cell surface and is anchored by a GPI linkage. Fluorescent in situ hybridization analysis localizes the PSCA gene to chromosome 8q24.2, a region of allelic gain in more than 80% of prostate cancers. A mouse homologue with 70% amino acid identity and similar genomic organization to human PSCA has also been identified. These results support PSCA as a target for prostate cancer diagnosis and therapy.

Low p27 expression predicts poor disease-free survival in patients with prostate cancer.

PURPOSE: p27 is an inhibitor of the cell cycle with potential tumor suppressor function. Decreased levels of p27 protein expression have been correlated with poor prognosis in patients with breast and colorectal carcinomas. Although as many as a third of patients with clinically localized prostate cancer will have relapse after radical prostatectomy, predicting who will have recurrence remains enigmatic. We examined the ability of p27 protein levels to predict outcome in patients with clinically localized disease who underwent radical prostatectomy. MATERIALS AND METHODS: p27 protein expression was evaluated in 86 patients with clinical stage T1-2 prostate cancer who were treated with radical prostatectomy. Archived paraffin embedded specimens were sectioned and immunostained with p27 antibody, and scored by 2 independent observers in a blinded fashion. The absence or presence of p27 protein was then correlated with biochemical relapse in univariate and multivariate analyses. RESULTS: In a multivariate analysis that included age, preoperative prostate specific antigen, Gleason score and pathological stage p27 was a strong independent predictor of disease-free survival (p = 0.0184, risk ratio 3.04), second only to pathological stage (p = 0.0001, risk ratio 6.73). Even more strikingly, multivariate analysis demonstrated that p27 was the strongest predictor of biochemical recurrence (p = 0.0081, risk ratio 4.99) among factors studied in patients with pathological T2a-T3b disease. CONCLUSIONS: Absent or low levels of p27 protein expression appear to be an adverse prognostic factor in patients with clinically organ confined disease treated by radical prostatectomy. This marker appears to be especially useful in those patients in whom surgery is believed to be potentially curative, that is patients with pathological T2-T3b disease. Patients with low or absent p27 protein expression may be candidates for novel adjuvant therapies.

Stem cell genes in androgen-independent prostate cancer.

Despite recent advances in the detection and treatment of early stage prostate cancer, there remains little effective therapy for patients with locally advanced and/or metastatic disease. Although the majority of patients with advanced disease respond initially to androgen ablation therapy, most go on to develop androgen-independent tumors that are inevitably fatal. Therefore, understanding the mechanisms by which a hormone-sensitive tumor escapes hormonal control is critical to the development of effective therapeutic modalities. The study of the differentiation pathways of normal and abnormal prostate growth has led to the development of a stem cell model for prostate cancer [1-3]. Recent work discussed in this commentary suggests that prostate tumors resist apoptosis and proliferate by adopting features of normal prostatic stem/progenitor cells. Basal cells, the putative stem/progenitor cells of the prostate, possess the phenotype of androgen-independence as do most advanced prostate cancers. Therefore, the study of basal cells may prove critical to understanding prostate carcinogenesis and to the development of novel strategies for preventing and managing prostate cancer.

Progression of metastatic human prostate cancer to androgen independence in immunodeficient SCID mice.

Prostate cancer mortality results from metastasis to bone and hormone-independent tumor growth. Models to study these progressive changes are lacking. Here we describe the propagation of advanced human prostate cancer by direct transfer of surgical samples from patients into immune-deficient male SCID mice. Explants from six of eight patients formed prostate tumors and two showed unique cytogenetic, biologic and molecular features that were retained through six or more passages. One grew in an androgen-independent fashion, whereas the second formed tumors that regressed following castration then regrew. Micrometastatic disease was detected in the hematopoietic tissues of half of the recipient mice. Thus selected specimens of advanced human prostate cancer can be propagated in SCID mice in a manner that recapitulates the clinical transition from androgen-sensitive to androgen-independent growth, accompanied by micrometastasis.