TempEasy 3D Hydrogel Coculture System Provides Mechanistic Insights into Prostate Cancer Bone Metastasis.

Patients diagnosed with advanced prostate cancer (PCa) often experience incurable bone metastases; however, a lack of relevant experimental models has hampered the study of disease mechanisms and the development of therapeutic strategies. In this study, we employed the recently established Temperature-based Easy-separable (TempEasy) 3D cell coculture system to investigate PCa bone metastasis. Through coculturing PCa and bone cells for 7 days, our results showed a reduction in PCa cell proliferation, an increase in neovascularization, and an enhanced metastasis potential when cocultured with bone cells. Additionally, we observed increased cell proliferation, higher stemness, and decreased bone matrix protein expression in bone cells when cocultured with PCa cells. Furthermore, we demonstrated that the stiffness of the extracellular matrix had a negligible impact on molecular responses in both primary (PCa cells) and distant malignant (bone cells) sites. The TempEasy 3D hydrogel coculture system is an easy-to-use and versatile coculture system that provides valuable insights into the mechanisms of cell-cell communication and interaction in cancer metastasis.

Precision oncology using organoids of a secretory carcinoma of the salivary gland treated with TRK-inhibitors.

The use of anticancer drugs targeting specific molecular tumor characteristics is rapidly increasing in clinical practice, but selecting patients to benefit from these remains a challenge. It has been suggested that organoid cultures would be ideally suited to test drug responses in vitro. Here we describe and characterize in depth a case of ETV6-NTRK3 gene fusion-positive secretory carcinoma of the salivary glands and corresponding organoid cultures that responded and subsequently acquired resistance to TRK targeting therapy with larotrectinib. This case-culture-characterization illustrates the advances made in precision oncology, but also exposes important caveats in using organoids to predict treatment response.

Development and characterization of patient-derived salivary gland cancer organoid cultures.

OBJECTIVE: Three-dimensional organoid cell cultures have been established for a variety of human cancers. For most rare cancers, including salivary gland cancer (SGC), these models are lacking, despite the great unmet need to study cancer biology in these diseases. Therefore, we aimed to develop patient-derived organoid (PDO) models for different subtypes of SGC. METHODS: Tumor samples of SGC patients were processed and embedded in Matrigel. Successful PDOs (expandable > 1*106 cells) were phenotypically characterized using immunohistochemistry (IHC) and genotypically by gene fusion analysis and by targeted and whole-exome sequencing. Successfully established PDOs were subjected to small-scale drug screening. RESULTS: Out of 37 attempts, 7 viable short-term PDOs were established (19 % success rate; 3 salivary duct carcinoma, 3 adenoid cystic carcinoma and 1 mucoepidermoid carcinoma). Each PDO showed close phenotypical mimicry to parental tissue. Genotypic characterization revealed that in each PDO > 97.6 % of all COSMIC annotated variants and all MYB, MYBL1 and NFIB gene rearrangements were retained. Drug screening was proven feasible in all PDOs. CONCLUSION: We present the first comprehensively characterized short-term SGC PDO models for three subtypes of SGC with close phenotypic and genotypic resemblance to parental tissue, which can be used for drug screening applications.

Reovirus mutant jin-3 exhibits lytic and immune-stimulatory effects in preclinical human prostate cancer models.

Treatment of castration-resistant prostate cancer remains a challenging clinical problem. Despite the promising effects of immunotherapy in other solid cancers, prostate cancer has remained largely unresponsive. Oncolytic viruses represent a promising therapeutic avenue, as oncolytic virus treatment combines tumour cell lysis with activation of the immune system and mounting of effective anti-tumour responses. Mammalian Orthoreoviruses are non-pathogenic human viruses with a preference of lytic replication in human tumour cells. In this study, we evaluated the oncolytic efficacy of the bioselected oncolytic reovirus mutant jin-3 in multiple human prostate cancer models. The jin-3 reovirus displayed efficient infection, replication, and anti-cancer responses in 2D and 3D prostate cancer models, as well as in ex vivo cultured human tumour slices. In addition, the jin-3 reovirus markedly reduced the viability and growth of human cancer cell lines and patient-derived xenografts. The infection induced the expression of mediators of immunogenic cell death, interferon-stimulated genes, and inflammatory cytokines. Taken together, our data demonstrate that the reovirus mutant jin-3 displays tumour tropism, and induces potent oncolytic and immunomodulatory responses in human prostate cancer models. Therefore, jin-3 reovirus represents an attractive candidate for further development as oncolytic agent for treatment of patients with aggressive localised or advanced prostate cancer.

Molecular Phenotyping of AR Signaling for Predicting Targeted Therapy in Castration Resistant Prostate Cancer.

Castration-resistant prostate cancer (CRPC) is defined by resistance of the tumor to androgen deprivation therapy (ADT). Several molecular changes, particularly in the AR signaling cascade, have been described that may explain ADT resistance. The variety of changes may also explain why the response to novel therapies varies between patients. Testing the specific molecular changes may be a major step towards personalized treatment of CRPC patients. The aim of our study was to evaluate the molecular changes in the AR signaling cascade in CRPC patients. We have developed and validated several methods which are easy to use, and require little tissue material, for exploring AR signaling pathway changes simultaneously. We found that the AR signaling pathway is still active in the majority of our CRPC patients, due to molecular changes in AR signaling components. There was heterogeneity in the molecular changes observed, but we could classify the patients into 4 major subgroups which are: AR mutation, AR amplification, active intratumoral steroidogenesis, and combination of AR amplification and active intratumoral steroidogenesis. We suggest characterizing the AR signaling pathway in CRPC patients before beginning any new treatment, and a recent fresh tissue sample from the prostate or a metastatic site should be obtained for the purpose of this characterization.

Partial Adrenalectomy Carries a Considerable Risk of Incomplete Cure in Primary Aldosteronism.

PURPOSE: Laparoscopic adrenalectomy is standard treatment for patients with unilateral aldosterone-producing adenomas, but surgeons are increasingly tempted to perform partial adrenalectomy, disregarding potential multinodularity of the adrenal. We assess the diagnostic value of endoscopic ultrasound for differentiating solitary adenomas from multinodularity by examining in-depth adrenal pathology with ex vivo 11.7 T magnetic resonance imaging and immunohistochemistry. MATERIALS AND METHODS: In 15 primary aldosteronism patients, we performed intraoperative endoscopic ultrasound, ex vivo magnetic resonance imaging and histopathological examination. Every adrenal was intraoperatively and postoperatively assessed for solitary adenomas or multinodular hyperplasia. After unblinding for ex vivo magnetic resonance imaging results a second detailed histopathological examination, including immunohistochemistry analysis with CYP11B2 (aldosterone synthase) and chemokine receptor 4 (CXCR4), a new marker for aldosterone-producing adenomas, was performed. Finally, presence of somatic mutations linked to aldosterone-producing adenomas was assessed. RESULTS: The sensitivity and specificity of endoscopic ultrasound to identify multinodularity were 46% and 50%, respectively. We found multinodular hyperplasia in 87% of adrenals with ex vivo magnetic resonance imaging combined with detailed histopathology, and 6 adrenals contained multiple CYP11B2-producing nodules. Every CYP11B2 positive nodule and 61% of CYP11B2 negative nodules showed CXCR4 staining. Finally, in 4 adrenals (27%) we found somatic mutations. In multinodular glands, only 1 nodule harbored this mutation. CONCLUSIONS: Intraoperative endoscopic ultrasound in primary aldosteronism patients has low accuracy to identify multinodularity. Ex vivo magnetic resonance imaging can serve as a tool to direct detailed histopathological examination, which frequently shows CYP11B2 production in multiple nodules. Therefore, partial adrenalectomy is inappropriate in primary aldosteronism as multiple aldosterone-producing nodules easily stay behind.

Polyisocyanide Hydrogels as a Tunable Platform for Mammary Gland Organoid Formation.

In the last decade, organoid technology has developed as a primary research tool in basic biological and clinical research. The reliance on poorly defined animal-derived extracellular matrix, however, severely limits its application in regenerative and translational medicine. Here, a well-defined, synthetic biomimetic matrix based on polyisocyanide (PIC) hydrogels that support efficient and reproducible formation of mammary gland organoids (MGOs) in vitro is presented. Only decorated with the adhesive peptide RGD for cell binding, PIC hydrogels allow MGO formation from mammary fragments or from purified single mammary epithelial cells. The cystic organoids maintain their capacity to branch for over two months, which is a fundamental and complex feature during mammary gland development. It is found that small variations in the 3D matrix give rise to large changes in the MGO: the ratio of the main cell types in the MGO is controlled by the cell-gel interactions via the cell binding peptide density, whereas gel stiffness controls colony formation efficiency, which is indicative of the progenitor density. Simple hydrogel modifications will allow for future introduction and customization of new biophysical and biochemical parameters, making the PIC platform an ideal matrix for in depth studies into organ development and for application in disease models.

Label retention and stem cell marker expression in the developing and adult prostate identifies basal and luminal epithelial stem cell subpopulations.

BACKGROUND: Prostate cancer is the second most frequent cancer among males worldwide, and most patients with metastatic disease eventually develop therapy-resistant disease. Recent research has suggested the existence of cancer stem-like cells, and that such cells are behind the therapy resistance and progression. METHODS: Here, we have taken advantage of the relatively quiescent nature of stem cells to identify the slow-cycling label-retaining stem cell (LRC) populations of the prostate gland. Mice were pulsed with bromodeoxyuridine (BrdU) during prostate organogenesis, and the LRC populations were then identified and characterized in 5-day-old and in 6-month-old adult animals using immunohistochemistry and immunofluorescence. RESULTS: Quantification of LRCs in the adult mouse prostate showed that epithelial LRCs were significantly more numerous in prostatic ducts (3.7 ± 0.47% SD) when compared to the proximal (1.4 ± 0.83%) and distal epithelium (0.48 ± 0.08%) of the secretory lobes. LRCs were identified in both the basal and epithelial cell layers of the prostate, and LRCs co-expressed several candidate stem cell markers in a developmental and duct/acini-specific manner, including Sca-1, TROP-2, CD133, CD44, c-kit, and the novel prostate progenitor marker cytokeratin-7. Importantly, a significant proportion of LRCs were localized in the luminal cell layer, the majority in ducts and the proximal prostate, that co-expressed high levels of androgen receptor in the adult prostate. CONCLUSIONS: Our results suggest that there are separate basal and luminal stem cell populations in the prostate, and they open up the possibility that androgen receptor-expressing luminal stem-like cells could function as cancer-initiating and relapse-responsible cells in prostate cancer.

Identification of potential bladder progenitor cells in the trigone.

Urothelial cells are specialized epithelial cells in the bladder that serve as a barrier toward excreted urine. The urothelium consists of superficial cells (most differentiated cells), intermediate cells, and basal cells; the latter have been considered as urothelium progenitor cells. In this study, BrdU or EdU was administrated to pregnant mice during E8-E13 for 2 consecutive days when bladder development occurs. The presence of label retaining cells was investigated in bladders from offspring. In 6 months old mice ~1% of bladder cells retained labeling. Stem cell markers as defined for other tissues (e.g., p63, CD44, CD117, trop2) co-localized or were in close vicinity to label retaining cells, but they were not uniquely limited to these cells. Remarkably, label retaining cells were distributed in all three cell layers (p63+, CK7+, and CK20+) of the urothelium and concentrated in the bladder trigone. This study demonstrates that bladder progenitor cells are present in all cell layers and reside mostly in the trigone. Understanding the geographic location of slow cycling cells provides crucial information for tissue regenerative purposes in the future.

Rational basis for the combination of PCA3 and TMPRSS2:ERG gene fusion for prostate cancer diagnosis.

BACKGROUND: The prostate cancer gene 3 (PCA3) and TMPRSS2:ERG gene fusion are promising prostate cancer (PCa) specific biomarkers. Our aim was to simultaneously quantify the expression levels of PCA3 and TMPRSS2:ERG in a panel of benign prostatic hyperplasia (BPH), normal prostate adjacent to PCa (NP) and PCa tissue samples, to provide a rational basis for the understanding of the false-positive and false-negative results of the urine assays. METHODS: The tissue samples were carefully histopathologically characterized to obtain homogeneous groups. The mRNA was isolated, transcribed into cDNA and the relative expressions of PCA3 and TMPRSS2:ERG were measured using a quantitative real-time polymerase chain reaction. The expression levels of PCA3 and TMPRSS2:ERG were compared between the different groups. RESULTS: We included 48 BPH, 32 NP, and 48 PCa. The PCA3 expression levels progressively increased from BPH to NP (3 times) and finally to PCa (30 times). There were one false-positive sample and seven false-negative samples. The TMPRSS2:ERG gene fusion was found in 8.3% of the BPH, 15.6% of the NP, and 50% of the PCa samples. The use of TMPRSS2:ERG in the PCA3 negative cases allowed diagnosis of four of the seven false-negative samples and added one false-positive, but we had to define a cut-off value to avoid eight false-positive results. CONCLUSIONS: Considering tissue expression of the markers, most of the false-negative results of the PCA3 test were corrected by TMPRSS2:ERG (57%) and the combination of both had a higher sensitivity for PCa diagnosis. Some of the control samples did express TMPRSS2:ERG and a cut-off value had to be defined to avoid false-positive results.

DC-SCRIPT: AR and VDR regulator lost upon transformation of prostate epithelial cells.

BACKGROUND: Nuclear receptors (NR), including the Androgen Receptor (AR) and the Vitamin D Receptor (VDR), play an important role in prostate cancer etiology. We recently found that DC-SCRIPT is a prognostic marker in breast cancer and a unique NR coregulator differentially regulating different classes of NRs. Here we investigated the importance of DC-SCRIPT in prostate cancer. METHODS: DC-SCRIPT mRNA expression was measured by qPCR. Immunohistochemistry was used to detect DC-SCRIPT protein expression. The functional effects of DC-SCRIPT on the transcriptional activity of AR and VDR were assessed by luciferase reporter assays and qPCR assays on well-known AR and VDR target genes. RESULTS: DC-SCRIPT mRNA was higher in normal than in corresponding malignant prostate tissue but could not be related to disease stage. DC-SCRIPT protein was found in morphologically normal prostate glands and in infiltrating immune cells. Strikingly, DC-SCRIPT protein expression was absent in malignant prostate epithelial tissue and prostate carcinoma cell lines. DC-SCRIPT protein expression appears to be lost prior to the basal cell marker HMW cytokeratin used in prostate carcinoma diagnostics. In addition, our data demonstrated that DC-SCRIPT repressed transcription mediated by wild-type and mutated AR while enhancing VDR mediated transcription. In addition, transient expression of DC-SCRIPT expression in prostate carcinoma cells strongly repressed cell growth. CONCLUSIONS: DC-SCRIPT is a key regulator of nuclear receptors AR and VDR that play an opposite role in prostate cancer etiology and loss of DC-SCRIPT may be involved in the onset of prostate cancer.

Biomarkers for the diagnosis of prostatic inflammation in benign prostatic hyperplasia.

BACKGROUND: Chronic prostatic inflammation could be a central mechanism in benign prostatic hyperplasia (BPH) progression. Currently, the histological examination of prostate biopsies remains the only way to diagnose prostatic inflammation. Our objective was to find new noninvasive biomarkers for the diagnosis of prostatic inflammation. METHODS: Ninety BPH samples were investigated in two steps. First, a hypothesis was generated using a profiling procedure with a panel of 96 genes on an initial set of 30 samples. Then, the candidate biomarkers were validated on a large number of samples (n = 90). Gene expression was compared with the histological prostatic inflammation score based on the density and the confluence of lymphoid nodules. Finally, protein transcripts of the candidate biomarkers were investigated in urine samples and compared with clinical data. RESULTS: Of the 96 genes, nine were significantly correlated with the inflammation score on the initial set of patients. Four of them were validated on the complete set of patients: CCR7, CD40LG, CTLA4, and ICOS. ICOS and CTLA4 protein levels were readily measured in urine samples using a conventional ELISA procedure. High-ICOS expression in urine was associated with a higher post-void residual and a lower maximum urinary flow rate. CONCLUSIONS: Four genes were significantly upregulated at the mRNA level in the prostate tissue of patients with severe inflammation score. Two proteins were measured in urine samples, and were associated with maximum uroflowmetry and post-void residual. A prospective clinical study is needed to confirm their clinical relevance.

Components of the plasminogen activator system and their complexes in renal cell and bladder cancer: comparison between normal and matched cancerous tissues.

OBJECTIVE: To analyse and compare the concentration of plasminogen activator (PA), urokinase-type PA (uPA), tissue-type PA (tPA), PA inhibitor (PAI)-1 and PAI-2, and the complexes uPA-PAI-1 and tPA-PAI-1 and calculated uPA and tPA uncomplexed with PAI-1 ('free') in urothelial cell carcinoma and matched benign urothelium, and in renal cell carcinoma (RCC) and matched benign renal tissue. PATIENTS AND METHODS: Tissue samples were obtained during cystectomy (33 patients) and nephrectomy (55), and specific enzyme-linked immunosorbent assays were used to assess the PA components in extracts of these tissues. RESULTS: Tissue levels of uPA-PAI-1 and tPA-PAI-1, but also PAI-1 itself, were greater in tumorous bladder and kidney tissue than in matched normal tissue (by 1.5-7.8 times). Free tPA was clearly lower in tumour tissue (by 0-0.12-fold). In bladder cancer, but not in RCC, levels of uPA (15.8-fold) and free uPA (16.4-fold) were greater in tumour tissue. Free uPA levels were less in RCC (0.41-fold). For both normal bladder and kidney tissue, there was no clear correlation between uPA-PAI-1 complex and either component. However, the formation of tPA-PAI-1 complexes in normal bladder and kidney tissue was primarily determined by PAI-1. Interestingly, in tumour tissues there was a strong, significant correlation between complex levels and both components. CONCLUSION: RCC and bladder cancer show distinct profiles of components of the PA system. This study provides a basis for further studies into both the (patho)physiological role of the PA system in these tumours, and into a possible relation with tumour progression and prognosis, and as target for therapy.

hTERT-immortalized prostate epithelial and stromal-derived cells: an authentic in vitro model for differentiation and carcinogenesis.

Prostate cancer is the most commonly diagnosed type of cancer in men, and there is no available cure for patients with advanced disease. In vitro model systems are urgently required to permit the study of human prostate cell differentiation and malignant transformation. Unfortunately, human prostate cells are particularly difficult to convert into continuously growing cultures. We report here the successful immortalization without viral oncogenes of prostate epithelial cells and, for the first time, prostate stromal cells. These cells exhibit a significant pattern of authentic prostate-specific features. In particular, the epithelial cell culture is able to differentiate into glandular buds that closely resemble the structures formed by primary prostate epithelial cells. The stromal cells have typical characteristics of prostate smooth muscle cells. These immortalized cultures may serve as a unique experimental platform to permit several research directions, including the study of cell-cell interactions in an authentic prostate microenvironment, prostate cell differentiation, and most significantly, the complex multistep process leading to prostate cell transformation.

Identification of androgen-responsive genes that are alternatively regulated in androgen-dependent and androgen-independent rat prostate tumors.

The vast majority of androgen-dependent prostate tumors progress toward incurable, androgen-independent tumors. The identification of androgen-responsive genes, which are still actively transcribed in the tumors of patients who have undergone androgen ablation, may shed light on the molecular mechanisms underlying this phenomenon. To address this question, we chose the Dunning R3327 rat model system, in which the progression from androgen-dependent to -independent tumors is represented by several transplantable prostate-derived tumors. Gene expression profiles were analyzed in normal rat prostates and in the prostates of rats 14 days after castration by use of microarrays containing approximately 5,000 oligonucleotides, together representing more than 4,800 known rat genes. These expression profiles were compared with similarly obtained expression profiles of androgen-dependent and androgen-independent rat prostate tumors. By doing so, a series of known and novel prostate cancer-associated androgen-responsive genes was identified. Within this series, we were able to identify several clusters of genes that are differentially regulated in the various prostate tumors. These genes may serve as (i) novel prognostic identifiers and (ii) novel therapeutic targets.

Intermediate cells in human prostate epithelium are enriched in proliferative inflammatory atrophy.

Within the human prostate epithelium four cell populations can be discriminated based on their expression of keratins (K). Basal cells express high levels of K5 and K14, as well as p63, whereas they have very low levels of androgen receptor, prostate-specific antigen (PSA), K8, and K18. Luminal secretory cells lack p63, K5, and K14 but express high levels of K8, K18, androgen receptor, and PSA. Additionally, cells have been identified with a keratin phenotype intermediate between basal and luminal cells that co-express high levels of K5 and K18 (K5/18) as well as hepatocyte growth factor receptor c-MET. Although intermediate cells have been proposed as precursor cells of prostate cancer, their biology is ill defined. Epithelial cells in proliferative inflammatory atrophy (PIA) appear to be cycling rapidly as indicated by expression of Ki-67, and morphological transitions have been identified between PIA and high-grade prostate intraepithelial neoplasia. Many of the atrophic epithelial luminal cells in PIA are candidates for intermediate cells based in part on weak expression of PSA and androgen receptor, high levels of K8/18, and lack of p63. The objective of this study was to further clarify the phenotype of the proposed intermediate cells in PIA and to quantitatively determine the level in which these intermediate cells preferentially occur in PIA lesions. Intermediate cells were immunohistochemically demonstrated using antibodies to K5, K14, K18, and c-MET. Using radical prostatectomy specimens (n = 15) the area fraction of intermediate cells in normally differentiated prostate epithelium and PIA were quantified by a grid point counting method. Atrophic luminal cells of PIA lesions expressed K5 in 39.2 +/- 7.4% of cells compared to 2.4 +/- 2.3% in normal epithelium (P < 0.00001). By contrast, K14 was only expressed in 3.0 +/- 3.2% of the luminal cells. Previous studies have shown that virtually 100% of these atrophic luminal cells are strongly positive for K8/18. c-MET was present in 44.1 +/- 14.1% of luminal cells in PIA but only in 2.1 +/- 2.8% of luminal cells in normal epithelium (P < 0.00001). To unambiguously determine whether intermediate luminal cells in PIA show increased proliferative activity and decreased p27(kip1) expression, double-staining immunofluorescence of Ki-67 and K5, as well as p27(Kip1) and K5 was performed. Luminal cells in PIA often co-expressed K5 and Ki-67. Although p27(Kip1) was strongly expressed in K5-negative differentiated cells in normal epithelium, p27(Kip1) staining was absent in many of the K5-positive cells in the luminal compartment of PIA. We conclude that cells phenotypically intermediate between basal and secretory cells are enriched in PIA lesions. The finding of a large number of highly proliferating intermediate cells in PIA provides further support that these cells may serve as preferred target cells in prostate carcinogenesis.

DD3(PCA3), a very sensitive and specific marker to detect prostate tumors.

We identified DD3(PCA3) as one of the most prostate cancer-specific genes at present (M. J. Bussemakers et al. Cancer Res., 59: 5975-5979, 1999). Consequently, DD3(PCA3) is an interesting candidate for use as a diagnostic and/or prognostic marker. In this study we developed a method for the accurate quantification of DD3(PCA3) mRNA, using real-time quantitative reverse transcription-PCR. DD3(PCA3) was expressed at low levels in normal prostate but not in 21 selected other normal tissues, blood, or 39 tumor samples other than prostate. The diagnostic and prognostic value of DD3(PCA3) in normal, hyperplastic, and malignant prostate tissues was determined and compared with another promising tumor marker for prostate cancer, telomerase reverse transcriptase (hTERT gene), the expression of which is related to telomerase activity. Sensitivity and specificity estimates for both genes were calculated as the area under the receiver-operating characteristics curve (AUC-ROC). DD3(PCA3) (AUC-ROC, 0.98) demonstrated better diagnostic efficacy than hTERT (AUC-ROC, 0.88). Moreover, the median increase in mRNA expression in tumor tissues compared with nonmalignant prostate tissues was much higher for DD3(PCA3) (34-fold) than for hTERT (6-fold). In tumor tissues, the median expression of DD3(PCA3) was much higher than hTERT (5849 versus 10 normalized mRNA copies). A significant relationship was observed only between tumor stage and hTERT gene expression. We conclude that expression of the DD3(PCA3) gene is a very sensitive and specific marker for the detection of prostate tumor cells in a high background of normal (prostate) cells. Consequently, DD3 measurements may be used for clinical application in prostate needle biopsies or bodily fluids such as blood, ejaculate, urine, or prostate massage fluid.

Intermediate cells in normal and malignant prostate epithelium express c-MET: implications for prostate cancer invasion.

BACKGROUND: Analysis of keratin (K) expression discriminates luminal (K18) and intermediate (K5/18) cells in prostate carcinoma, while basal (K5/14) cells are absent. Intermediate cells have been proposed as targets of malignant transformation in prostate cancer and precursors of androgen-independent tumor progression. We demonstrate localization of hepatocyte growth factor (HGF) receptor c-MET in intermediate cells in both normal and malignant prostate epithelium. METHODS: Receptor localization was analyzed using triple staining for c-MET, K5, K14, and K18. The percentage of strongly c-MET positive cells was determined in 15 prostate cancer patients undergoing androgen-deprivation and 14 patients without neo-adjuvant treatment. Effects of HGF were investigated on prostate cancer cell line DU145. RESULTS: c-MET expression in non-malignant epithelium was strong in intermediate cells absent in differentiated cells, and heterogeneous in basal cells. In prostate cancer, intermediate cells displayed high c-MET levels coupled with mild expression in differentiated cells. During androgen-deprivation, 7.6% of tumor cells revealed high c-MET expression compared to 1.7% without treatment (P = 0.02). Matrigel penetration of DU145 was 8.2 +/- 1.7 mm(2) after HGF stimulation compared to 3.6 +/- 2.4 mm(2) in controls (P < 0.02). CONCLUSIONS: Intermediate cells in normal and malignant prostate epithelium express high c-MET levels, indicating that they are prone to stromal invasion in prostate carcinoma.