Prostate Basal Cells Research Articles

Epcam, CD44, and CD49f distinguish sphere-forming human prostate basal cells from a subpopulation with predominant tubule initiation capability.

BackgroundHuman prostate basal cells expressing alpha-6 integrin (CD49fHi) and/or CD44 form prostaspheres in vitro. This functional trait is often correlated with stem/progenitor (S/P) activity, including the ability to self-renew and induce differentiated tubules in vivo. Antigenic profiles that distinguish tubule-initiating prostate stem cells (SCs) from progenitor cells (PCs) and mature luminal cells (LCs) with less regenerative potential are unknown.Methodology/Principle FindingsProstasphere assays and RT-PCR analysis was performed following FACS separation of total benign prostate cells based upon combinations of Epcam, CD44, and/or CD49f expression. Epithelial cell fractions were isolated, including Epcam+CD44+ and Epcam+CD44+CD49fHi basal cells that formed abundant spheres. When non-sphere-forming Epcam+CD44− cells were fractionated based upon CD49f expression, a distinct subpopulation (Epcam+CD44−CD49fHi) was identified that possessed a basal profile similar to Epcam+CD44+CD49fHi sphere-forming cells (p63+ARLoPSA−). Evaluation of tubule induction capability of fractionated cells was performed, in vivo, via a fully humanized prostate tissue regeneration assay. Non-sphere-forming Epcam+CD44− cells induced significantly more prostate tubular structures than Epcam+CD44+ sphere-forming cells. Further fractionation based upon CD49f co-expression identified Epcam+CD44−CD49fHi (non-sphere-forming) basal cells with significantly increased tubule induction activity compared to Epcam+CD44−CD49fLo (true) luminal cells.Conclusions/SignificanceOur data delineates antigenic profiles that functionally distinguish human prostate epithelial subpopulations, including putative SCs that display superior tubule initiation capability and induce differentiated ductal/acini structures, sphere-forming PCs with relatively decreased tubule initiation activity, and terminally differentiated LCs that lack both sphere–forming and tubule-initiation activity. The results clearly demonstrate that sphere-forming ability is not predictive of tubule-initiation activity. The subpopulations identified are of interest because they may play distinct roles as cells of origin in the development of prostatic diseases, including cancer.

Bladder expression of CD cell surface antigens and cell-type-specific transcriptomes

Many cell types have no known functional attributes. In the bladder and prostate, basal epithelial and stromal cells appear similar in cytomorphology and share several cell surface markers. Their total gene expression (transcriptome) should provide a clear measure of the extent to which they are alike functionally. Since urologic stromal cells are known to mediate organ-specific tissue formation, these cells in cancers might exhibit aberrant gene expression affecting their function. For transcriptomes, cluster designation (CD) antigens have been identified for cell sorting. The sorted cell populations can be analyzed by DNA microarrays. Various bladder cell types have unique complements of CD molecules. CD9(+) urothelial, CD104(+) basal and CD13(+) stromal cells of the lamina propria were therefore analyzed, as were CD9(+) cancer and CD13(+) cancer-associated stromal cells. The transcriptome datasets were compared by principal components analysis for relatedness between cell types; those with similarity in gene expression indicated similar function. Although bladder and prostate basal cells shared CD markers such as CD104, CD44 and CD49f, they differed in overall gene expression. Basal cells also lacked stem cell gene expression. The bladder luminal and stromal transcriptomes were distinct from their prostate counterparts. In bladder cancer, not only the urothelial but also the stromal cells showed gene expression alteration. The cancer process in both might thus involve defective stromal signaling. These cell-type transcriptomes provide a means to monitor in vitro models in which various CD-isolated cell types can be combined to study bladder differentiation and bladder tumor development based on cell-cell interaction.

Suppressor role of androgen receptor in proliferation of prostate basal epithelial and progenitor cells

Early studies have reported the differential roles of androgen receptor (AR) in different types (luminal, basal intermediate, and stromal) of prostate cancer cells. In vivo mouse model tumor studies using the total prostate epithelial knockout mice (pes-ARKO) also revealed that AR played a suppressive role in proliferation of the CK5(+)/CK8(+) progenitor/intermediate cells but a positive role in the CK5(-)/CK8(+) luminal epithelial cells. Using three different resources (one human basal epithelial cell line, one mouse basal epithelial originated progenitor cell line, and a basal epithelium-specific ARKO mouse model), we here demonstrated that the AR in basal epithelial cells of normal prostate plays a suppressive role in their proliferation but a positive role in differentiation into luminal epithelial cells. These results led us to conclude that ARs may play a negative role to suppress CK5(+) basal epithelial and progenitor cell proliferation, yet play an essential role to drive basal epithelial cells into more differentiated states. These results may explain why differential AR expression in different cell types within normal prostate is needed and suggest that ARs in prostate basal epithelial cells, although expressed at a very low level, are necessary to maintain the balance between progenitor cells and differentiated luminal epithelial cells.

Abstract C64: Adult murine prostate basal and luminal cells are self-sustained lineages that can both serve as targets for prostate cancer initiation

Abstract The prostate epithelial lineage hierarchy and the cellular origin for prostate cancer remain inadequately defined. We sought to utilize a lineage tracing approach to define the epithelial lineage hierarchy in the prostate. A previously reported K14-CreER transgenic mouse line was bred with a fluorescent reporter line to specifically label the prostate basal cell lineage. In parallel, the prostate luminal cell lineage was labeled with fluorescence using a novel K8-CreERT2 transgenic mouse line generated in our own lab. Using this lineage tracing approach, we show that adult rodent prostate basal and luminal cells are independently self-sustained in vivo. We then sought to characterize the cells of origin for prostate cancer in the context of loss of function of Pten, which occurs frequently in primary and advanced human prostate cancer. We bred the K14-CreER and K8-CreERT2 mouse lines with Ptenfl/fl mice separately so that Pten expression can be disrupted specifically in prostate basal and luminal cells, respectively. Disrupting Pten in either lineage led to prostate cancer initiation. However, the cellular composition and onset dynamics of the resulting tumors are distinctive. Prostate luminal cells are more responsive to Pten null-induced mitogenic signaling. In contrast, basal cells are resistant to direct transformation. Instead, loss of Pten activity induces the capability of basal cells to differentiate into transformation-competent luminal cells. These studies suggest that deregulation of the normal prostate epithelial differentiation program is a critical step for initiation of human prostate cancer with a basal cell origin. Furthermore, suppressing signaling pathways that induce basal-luminal differentiation may provide an efficient approach to prevent prostate cancer initiation. Citation Format: Nahyun Choi, Boyu Zhang, Li Zhang, Michael Ittmann, Li Xin. Adult murine prostate basal and luminal cells are self-sustained lineages that can both serve as targets for prostate cancer initiation [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C64.

Adult Murine Prostate Basal and Luminal Cells Are Self-Sustained Lineages that Can Both Serve as Targets for Prostate Cancer Initiation

The prostate epithelial lineage hierarchy and the cellular origin for prostate cancer remain inadequately defined. Using a lineage-tracing approach, we show that adult rodent prostate basal and luminal cells are independently self-sustained in vivo. Disrupting the tumor suppressor Pten in either lineage led to prostate cancer initiation. However, the cellular composition and onset dynamics of the resulting tumors are distinctive. Prostate luminal cells are more responsive to Pten null-induced mitogenic signaling. In contrast, basal cells are resistant to direct transformation. Instead, loss of Pten activity induces the capability of basal cells to differentiate into transformation-competent luminal cells. Our study suggests that deregulation of epithelial differentiation is a critical step for the initiation of prostate cancers of basal cell origin.

Activation of Wnt Signaling by Chemically Induced Dimerization of LRP5 Disrupts Cellular Homeostasis

Wnt signaling is crucial for a variety of biological processes, including body axis formation, planar polarity, stem cell maintenance and cellular differentiation. Therefore, targeted manipulation of Wnt signaling in vivo would be extremely useful. By applying chemical inducer of dimerization (CID) technology, we were able to modify the Wnt co-receptor, low-density lipoprotein (LDL)-receptor-related protein 5 (LRP5), to generate the synthetic ligand inducible Wnt switch, iLRP5. We show that iLRP5 oligomerization results in its localization to disheveled-containing punctate structures and sequestration of scaffold protein Axin, leading to robust β-catenin-mediated signaling. Moreover, we identify a novel LRP5 cytoplasmic domain critical for its intracellular localization and casein kinase 1-dependent β-catenin signaling. Finally, by utilizing iLRP5 as a Wnt signaling switch, we generated the Ubiquitous Activator of β-catenin (Ubi-Cat) transgenic mouse line. The Ubi-Cat line allows for nearly ubiquitous expression of iLRP5 under control of the H-2Kb promoter. Activation of iLRP5 in isolated prostate basal epithelial stem cells resulted in expansion of p63+ cells and development of hyperplasia in reconstituted murine prostate grafts. Independently, iLRP5 induction in adult prostate stroma enhanced prostate tissue regeneration. Moreover, induction of iLRP5 in male Ubi-Cat mice resulted in prostate tumor progression over several months from prostate hyperplasia to adenocarcinoma. We also investigated iLRP5 activation in Ubi-Cat-derived mammary cells, observing that prolonged activation results in mammary tumor formation. Thus, in two distinct experimental mouse models, activation of iLRP5 results in disruption of tissue homeostasis, demonstrating the utility of iLRP5 as a novel research tool for determining the outcome of Wnt activation in a precise spatially and temporally determined fashion.

Basaloid carcinoma of the prostate: A literature review with case report

Basal cell carcinoma of the prostate (BCP) is a neoplasm composed of prostatic basal cells. There are only a few publications outlining the diagnosis, treatment, prognosis and outcome for BCP. Traditionally surgery has been used but these tumors also respond to concomitant chemo-radiotherapy. Using a BCP case report treated with radical chemo-radiotherapy from a chemotherapy regimen used in anal cancers, we propose an alternative management to the traditional options of radical surgery and radical radiotherapy.

TP53INP1 overexpression in prostate cancer correlates with poor prognostic factors and is predictive of biological cancer relapse

Tumor protein 53-induced nuclear protein 1 (TP53INP1) is a proapoptotic protein involved in cell stress response. Whereas there is an overexpression of TP53INP1 in numerous tissues submitted to stress agents, TP53INP1 is down-expressed in stomach, pancreatic, and inflammation-mediated colic carcinomas. In medullary thyroid carcinomas, TP53INP1 overexpression correlates with poor prognosis. TP53INP1 expression has never been reported in Prostate Cancer (PC). Our aim was to investigate variations of TP53INP1 expression and their correlation to clinicopathological parameters in PC. Quantitative measurements of immunohistochemical expression of TP53INP1 using high-throughput densitometry, assessed on digitized microscopic tissue micro-array images, were correlated with clinicopathological parameters in 91 human PC. Treatment of LNCaP tumor cells in vitro with cytokines and with TP53INP1 antisense oligonucleotide (ASO) was also analyzed. In normal prostate tissues, TP53INP1 is only expressed in prostate basal cells. There is a de novo TP53INP1 expression in prostate luminal cells in inflammatory prostate tissues, high grade PIN lesions and in PC. Stimulation of LNCaP cells with inflammatory cytokines enhances the level of TP53INP1 mRNA. In PC, TP53INP1 overexpression correlates with high Gleason grade, unfavorable D'Amico score and lymph node invasion, and is an independent factor of biological cancer relapse. Moreover, treatment of LNCaP cells with a TP53INP1 ASO down-regulates TP53INP1 protein level, inhibits proliferation, and induces apoptosis. TP53INP1 overexpression in PC seems to be a worse prognostic factor, particularly predictive of biological cancer relapse. Results in vitro suggest that TP53INP1 could be considered as a relevant target for potential specific therapy.

Prostatic Basal Cell Carcinoma: A Case Report and Review of the Literature

Prostatic Basal Cell Carcinoma: A Case Report and Review of the Literature

ROCK Inhibitor Y-27632 Suppresses Dissociation-Induced Apoptosis of Murine Prostate Stem/Progenitor Cells and Increases Their Cloning Efficiency

Activation of the RhoA/ROCK signaling pathway has been shown to contribute to dissociation-induced apoptosis of embryonic and neural stem cells. We previously demonstrated that approximately 1 out of 40 Lin−Sca-1+CD49fhigh (LSC) prostate basal epithelial cells possess the capacities of stem cells for self-renewal and multi-lineage differentiation. We show here that treating LSC cells with the ROCK kinase inhibitor Y-27632 increases their cloning efficiency by 8 fold in an in vitro prostate colony assay. Y-27632 treatment allows prostate colony cells to replate efficiently, which does not occur otherwise. Y-27632 also increases the cloning efficiency of prostate stem cells in a prostate sphere assay and a dissociated prostate cell regeneration assay. The increased cloning efficiency is due to the suppression of the dissociation-induced, RhoA/ROCK activation-mediated apoptosis of prostate stem cells. Dissociation of prostate epithelial cells from extracellular matrix increases PTEN activity and attenuates AKT activity. Y-27632 treatment alone is sufficient to suppress cell dissociation-induced activation of PTEN activity. However, this does not contribute to the increased cloning efficiency, because Y-27632 treatment increases the sphere-forming unit of wild type and Pten null prostate cells to a similar extent. Finally, knocking down expression of both ROCK kinases slightly increases the replating efficiency of prostate colony cells, corroborating that they play a major role in the Y-27632 mediated increase in cloning efficiency. Our study implies that the numbers of prostate cells with stem/progenitor activity may be underestimated based on currently employed assays, supports that dissociation-induced apoptosis is a common feature of embryonic and somatic stem cells with an epithelial phenotype, and highlights the significance of environmental cues for the maintenance of stem cells.

168 DEFINING CONDITIONS TO GENERATE AND MAINTAIN PROSTATE CANCER STEM CELLS

You have accessJournal of UrologyStem Cell Research1 Apr 2011168 DEFINING CONDITIONS TO GENERATE AND MAINTAIN PROSTATE CANCER STEM CELLS Adrian Rybak, Anil Kapoor, Lizhi He, and Damu Tang Adrian RybakAdrian Rybak Hamilton, Canada More articles by this author , Anil KapoorAnil Kapoor Hamilton, Canada More articles by this author , Lizhi HeLizhi He Hamilton, Canada More articles by this author , and Damu TangDamu Tang Hamilton, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.237AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Cancer stem cells (CSCs) play critical roles in cancer metastasis and chemoresistance. In vitro, CSCs can be cultured in defined serum-free media (SFM) as suspension spheres. While accumulating evidence demonstrates the existence of prostate cancer stem cells (PCSCs), PCSCs have not been isolated from human primary prostate cancer (PC) tissues. This is largely due to limited primary PC tissues available clinically, as well as the heterogeneous nature of primary PC. These limitations have directly hindered the isolation of PCSCs from human primary PC tissues using classical methods that have been utilized to isolate CSCs from brain and breast cancers. These classical methods involved affinity purification of CSCs using specific markers for the respective tissue stem cells. Therefore, finding methods to propagate PCSCs may serve as an alternative means of isolating and enriching for this sub-population of cells from primary PC. To overcome these limitations, we have developed a unique condition to culture stem-like cells from the DU145 PC cell line. METHODS DU145 PC cells were plated under defined serum-free conditions, allowing a sub-population of stem-like cells to propagate as suspended spheroid colonies, or ‘spheres'. Immunofluorescent staining of spheres was carried out to identify potential cell surface markers, and to aid in the identification of the prospective tumor cell of origin. Furthermore, subcutaneous implantations were carried out in NOD/SCID mice in order to study the in vivo tumorigenic properties of sphere cells. RESULTS A sub-population of PC stem-like cells have been isolated and cultured long-term as spheres without any apparent reduction in their stem cell-like properties. These cells express prostate basal cell markers (CD44+34βE12+integrin-α2β1+) and have been shown to initiate tumorigenesis when implanted in NOD/SCID mice. Consistent with these reports, sphere cells displayed 100-fold increases in tumor-forming ability compared to monolayer cells in NOD/SCID mice, as 103, 104, and 105 sphere cells generated xenograft tumors as efficient as 105, 106, and 107 monolayer cells, respectively. Furthermore, stem-like cells can be re-isolated from xenograft tumors using our culture conditions. CONCLUSIONS We have defined culture conditions for long-term maintenance of sphere-forming cells which display stem-like properties from the DU145 cell line. Our defined serum-free culture conditions may serve as an alternative method to isolating and enriching for PCSCs from primary PC tissues. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e70-e71 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Adrian Rybak Hamilton, Canada More articles by this author Anil Kapoor Hamilton, Canada More articles by this author Lizhi He Hamilton, Canada More articles by this author Damu Tang Hamilton, Canada More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

High-throughput fluorescence polarization assay to identify inhibitors of Cbl(TKB)–protein tyrosine kinase interactions

The casitas B-lineage lymphoma (Cbl) proteins play an important role in regulating signal transduction pathways by functioning as E3 ubiquitin ligases. The Cbl proteins contain a conserved tyrosine kinase binding (TKB) domain that binds more than a dozen proteins, including protein tyrosine kinases (PTKs), in a phosphorylation-dependent manner. The cell surface expression levels of the PTKs are regulated by Cbl-mediated ubiquitination, internalization, and degradation. Dysfunction in this signaling cascade has resulted in prolonged activation of the PTKs and, therefore, has been implicated in inflammatory diseases and various cancers. Due to this negative regulatory function, Cbl has been largely ignored as a therapeutic target. However, recent studies, such as the identification of (i) gain of function c-Cbl mutations in subsets of myeloid cancer and (ii) c-Cbl as a prostate basal cell marker that correlates with poor clinical outcome, suggest otherwise. Here we report the development of a competitive high-throughput fluorescence polarization assay in a 384-well format to identify inhibitors of Cbl(TKB). The high-throughput screen readiness of the assay was demonstrated by screening the Prestwick Chemical Library.

A Tale of Two Cells: Discovering the Origin of Prostate Cancer

I n July, researchers in the lab of Owen Witte, M.D., at the University of California, Los Angeles, reported in Science that human prostate basal cells, transformed and then transplanted into mice, could form tumors. But in September 2009, a different group reported in Nature that prostate cancer in mice originated from a rare population of luminal cells. Basal versus luminal: irreconcilable? Apparently not. “Neither of them contradicts each other at all,” said Lynette Wilson, Ph.D., a professor in the departments of cell biology and urology at New York University. It’s possible that there are different prostate cancer cells of origin, she said. And the two papers are together a big step forward for a fi eld badly lacking such basic knowledge. That’s because the cellular origins of prostate cancer are still largely unknown. “The prostate cancer fi eld is struggling because, unlike [for] the breast, there is not a clear consensus about prostatic cell lineage,” said Gail Risbridger, Ph.D., a professor in the department of anatomy and developmental biology at Monash University in Melbourne, Australia. In breast cancer, six different subtypes have been mapped out, each arising from a distinct step in the differentiation of breast tissue from a common precursor cell. But we do not yet have such a map for prostate cancer. “This whole fi eld is still in its infancy,” Wilson said. Closing this knowledge gap could be the key to distinguishing between aggressive and indolent cancers and in developing individualized treatments — research that’s much further along in some other cancers. “It is conceivable that by identifying cell types of origin, you could distinguish different types of prostate cancer that differ in terms of their prognosis and/or treatment response,” said Michael Shen, Ph.D., a professor of medicine and genetics and development at Columbia University in New York. Shen led the group that reported in Nature last year that a rare population of luminal cells in mice gave rise to prostate cancer. That study and the recent report in Science open the door to new experiments that should pin down the exact cell types in which human prostate cancer originates.

Global Reactivation of Epigenetically Silenced Genes in Prostate Cancer

Transcriptional silencing associated with aberrant promoter hypermethylation is a common mechanism of inactivation of tumor suppressor genes in cancer cells. To globally profile the genes silenced by hypermethylation in prostate cancer, we screened a whole genome expression microarray for genes reactivated in the LNCaP, DU-145, PC-3, and MDA2b prostate tumor cell lines after treatment with the demethylating drug 5-aza-2-deoxycytidine and the histone deacetylation-inhibiting drug trichostatin A. A total of 2,997 genes showed at least 2-fold upregulation of expression after drug treatment in at least one prostate tumor cell line. For validation, we examined the first 45 genes, ranked by upregulation of expression, which had a typical CpG island and were known to be expressed in the normal cell counterpart. Two important findings were, first, that several genes known to be frequently hypermethylated in prostate cancer were apparent, and, second, that validation studies revealed eight novel genes hypermethylated in the prostate tumor cell lines, four of which were unmethylated in normal prostate cells and hypermethylated in primary prostate tumors (SLC15A3, 66%; KRT7, 54%; TACSTD2, 17%; GADD45b, 3%). Thus, we established the utility of our screen for genes hypermethylated in prostate cancer cells. One of the novel genes was TACSTD2/TROP2, a marker of human prostate basal cells with stem cell characteristics. TACSTD2 was unmethylated in prostatic intraepithelial neoplasia and may have utility in emerging methylation-based prostate cancer tests. Further study of the hypermethylome will provide insight into the biology of the disease and facilitate translational studies in prostate cancer.

Prominin‐1 (CD133) is not restricted to stem cells located in the basal compartment of murine and human prostate

Rodent and human prominin-1 are expressed in numerous adult epithelia and somatic stem cells. A report has shown that human PROMININ-1 carrying the AC133 epitope can be used to identify rare prostate basal stem cells (Richardson et al., J Cell Sci 2004; 117:3539–3545). Here we re-investigated its general expression in male reproductive tract including mouse and human prostate and in prostate cancer samples using various anti-prominin-1 antibodies. The expression was monitored by immunohistochemistry and blotting. Murine tissues were stained with 13A4 monoclonal antibody (mAb) whereas human samples were examined either with the AC133 mAb recognizing the AC133 glycosylation-dependent epitope or 80B258 mAb directed against the PROMININ-1 polypeptide. Mouse prominin-1 was detected at the apical domain of epithelial cells of ductus deferens, seminal vesicles, ampullary glands, and all prostatic lobes. In human prostate, immunoreactivity for 80B258, but not AC133 was revealed at the apical side of some epithelial (luminal) cells, in addition to the minute population of AC133/80B258-positive cells found in basal compartment. Examination of prostate adenocarcinoma revealed the absence of 80B258 immunoreactivity in the tumor regions. However, it was found to be up-regulated in luminal cells in the vicinity of the cancer areas. Mouse prominin-1 is widely expressed in prostate whereas in human only some luminal cells express it, demonstrating nevertheless that its expression is not solely associated with basal stem cells. In pathological samples, our pilot evaluation shows that PROMININ-1 is down-regulated in the cancer tissues and up-regulated in inflammatory regions.

Human prostate basal cell–generated mouse model of prostate cancer

Human prostate basal cell–generated mouse model of prostate cancer

The root of prostate cancer

UCLA researchers have identified prostatic basal cells as the originators of prostate cancer and have developed a mouse model based on these findings, which could help identify new treatments that attack the root of the disease and prevent recurrence.

Attenuated Proliferation and Trans-Differentiation of Prostatic Stromal Cells Indicate Suitability of Phosphodiesterase Type 5 Inhibitors for Prevention and Treatment of Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH) is characterized by tissue overgrowth and stromal reorganization primarily due to cellular proliferation and fibroblast-to-myofibroblast trans-differentiation. To evaluate the potential of phosphodiesterase type 5 (PDE5) inhibitors like tadalafil for prevention and treatment of BPH, we analyzed the role of the nitric oxide/cyclic GMP (cGMP)/PDE5 pathway for cellular proliferation and TGFbeta1-induced fibroblast-to-myofibroblast trans-differentiation in primary prostate stromal cells. Inhibition by tadalafil of PDE5, which is mainly expressed in the stromal compartment of the prostate, reduced proliferation of primary prostate stromal cells and to a lesser extent of primary prostate basal epithelial cells. Attenuated proliferation due to elevated intracellular cGMP levels was confirmed by inhibition of the cGMP-dependent protein kinase G by its inhibitor KT2358. Moreover, tadalafil strongly attenuated TGFbeta1-induced fibroblast-to-myofibroblast trans-differentiation. The inhibitory effect on trans-differentiation was also observed after small interfering RNA-mediated PDE5 knockdown. As confirmed by the MAPK kinase 1 inhibitor PD98059, this effect was mediated via MAPK kinase 1 signaling. We conclude that BPH patients might benefit from adjuvant therapies with PDE5 inhibitors that inhibit stromal enlargement due to cell proliferation, as well as TGFbeta1-induced trans-differentiation processes.

Critical Role of Smad2 in Tumor Suppression and Transforming Growth Factor-β–Induced Apoptosis of Prostate Epithelial Cells

Transforming growth factor-beta (TGF-beta) functions as a tumor suppressor of the prostate through mechanisms that remain unresolved. Although TGF-beta receptors directly activate both Smads 2 and 3, to date, Smad3 has been shown to be the essential mediator of most Smad-dependent TGF-beta responses, including control of gene expression, cell growth, apoptosis, and tumor suppression. Using a robust lentiviral short hairpin RNA system to silence Smads 2 and/or 3 in the NRP-152 nontumorigenic rat prostate basal epithelial cell line, we provide the first evidence for Smad2 as a critical mediator of TGF-beta-induced apoptosis and gene expression. Parallel analyses revealed that Smad3 is the major mediator of TGF-beta-induced transcriptional and apoptotic responses in the NRP-154 rat prostate carcinoma cell line. Remarkably, silencing Smad2 alone caused malignant transformation of NRP-152 cells, as assayed by s.c. tumor growth in athymic mice, whereas silencing Smad3 alone did not induce tumors. Nevertheless, tumors induced by silencing both Smads 2 and 3 were larger than those from silencing Smad2 alone. Given previous reports that NRP-152 cells have a stem cell phenotype, we speculate a critical role for Smad2 as a tumor suppressor in the basal epithelial or stem cell compartment of the prostate.

The Transcription Factor LMO2 Is a Robust Marker of Vascular Endothelium and Vascular Neoplasms and Selected Other Entities

The transcription factor LMO2 is involved in vascular and hematopoietic development and hematolymphoid neoplasia. We have demonstrated that LMO2 is expressed nearly ubiquitously in native and neoplastic vasculature, including lymphatics. LMO2 reactivity is otherwise virtually absent in nonhematolymphoid tissues except in breast myoepithelium, prostatic basal cells, and secretory phase endometrial glands. Vasculature is LMO2- in adult and fetal heart, brain of older adults, hepatic sinusoids, and hepatocellular carcinoma. LMO2 is uniformly expressed in benign vascular and lymphatic neoplasms and in most malignant vascular neoplasms with the exception of epithelioid vascular neoplasms of pleura and bone. Among nonvascular neoplasms, LMO2 reactivity is present in giant cell tumor of tendon sheath, juvenile xanthogranuloma, a subset of gastrointestinal stromal tumors, small round blue cell tumors, and myoepithelial-derived neoplasms. The restricted expression pattern, nuclear localization, and crisp staining of LMO2 in paraffin blocks make it an attractive candidate for the diagnostic immunohistochemistry laboratory.