Role of p63 and basal cells in the prostate

DNA methylation of E-cadherin is a priming mechanism for prostate development

In prostate and other epithelial cancers, E-cadherin (CDH1) is downregulated inappropriately by DNA methylation to promote an invasive phenotype. Though cancer frequently involves a reawakening of developmental signaling pathways, whether DNA methylation of Cdh1 occurs during organogenesis has not been determined. Here we show that DNA methylation of Cdh1 mediates outgrowth of developing prostate ducts. During the three-day gestational window leading up to and including prostate ductal initiation, Cdh1 promoter methylation increases and its mRNA and protein abundance decreases in epithelium giving rise to prostatic buds. DNA methylation is required for prostate specification, ductal outgrowth, and branching morphogenesis. All three endpoints are impaired by a DNA methylation inhibitor, which also decreases Cdh1 promoter methylation and increases Cdh1 mRNA and protein abundance. A CDH1 function-blocking antibody restores prostatic identity, bud outgrowth, and potentiates epithelial differentiation in the presence of the DNA methylation inhibitor. This is the first study to mechanistically link acquired changes in DNA methylation to the normal process of prostate organogenesis. We propose a novel mechanism whereby Cdh1 promoter methylation restricts Cdh1 abundance in developing prostate epithelium to create a permissive environment for prostatic bud outgrowth. Thus, DNA methylation primes the prostate primordium to respond to developmental cues mediating outgrowth, differentiation and maturation of the ductal network.

Cytokeratin 18 is not required for morphogenesis of developing prostates but contributes to adult prostate regeneration

Cytokeratin 18 (CK18) is a key component of keratin-containing intermediate filaments and has long been used as a classic luminal cell marker in prostatic tissue. However, the in vivo function of CK18 in prostate is not known so far. We reported in this study, unexpectedly, that deletion of CK18 in a mouse model did not affect the morphological or the histological structures of adult prostate, as the CK18 knockout prostate displayed a normal glandular ductal structure, branching pattern, and composition of both luminal and basal cells. However, CK18 loss compromised the regenerative tubular branching in dorsolateral prostate after castration and androgen replacement. Therefore, in contrast to its importance as luminal cell marker, CK18 is dispensable for the prostate morphogenesis but contributes to adult prostate regeneration.

Maturation of the developing human fetal prostate in a rodent xenograft model

BACKGROUND

Prostate cancer is the most commonly diagnosed nonskin cancer in men. The etiology of prostate cancer is unknown, although both animal and epidemiologic data suggest that early life exposures to various toxicants, may impact DNA methylation status during development, playing an important role.

METHODS

We have developed a xenograft model to characterize the growth and differentiation of human fetal prostate implants (gestational age 12-24 weeks) that can provide new data on the potential role of early life stressors on prostate cancer. The expression of key immunohistochemical markers responsible for prostate maturation was evaluated, including p63, cytokeratin 18, α-smooth muscle actin, vimentin, caldesmon, Ki-67, prostate-specific antigen, estrogen receptor-α, and androgen receptor. Xenografts were separated into epithelial and stromal compartments using laser capture microdissection (LCM), and the DNA methylation status was assessed in >480,000 CpG sites throughout the genome.

RESULTS

Xenografts demonstrated growth and maturation throughout the 200 days of post-implantation evaluation. DNA methylation profiles of laser capture microdissected tissue demonstrated tissue-specific markers clustered by their location in either the epithelium or stroma of human prostate tissue. Differential methylated promoter region CpG-associated gene analysis revealed significantly more stromal than epithelial DNA methylation in the 30- and 90-day xenografts. Functional classification analysis identified CpG-related gene clusters in methylated epithelial and stromal human xenografts.

CONCLUSION

This study of human fetal prostate tissue establishes a xenograft model that demonstrates dynamic growth and maturation, allowing for future mechanistic studies of the developmental origins of later life proliferative prostate disease.

Activation of FGF2-FGFR signaling in the castrated mouse prostate stimulates the proliferation of basal epithelial cells

The prostate gland is unique in that it undergoes rapid regression following castration but regenerates completely once androgens are replaced. Residual ductal components play an important role in the regeneration of a fully functional prostate. In this study, to examine how androgen status affects prostate structure and components, we conducted histopathological studies of the involuted and regenerated mouse dorsolateral prostate (DLP). In the castrated mouse DLP, the number of luminal epithelial cells decreased in a time-dependent manner. On Day 14 postandrogen replacement, the number of luminal epithelial cells was completely restored to the baseline level. In contrast, the number of basal epithelial cells gradually increased in the castrated mouse prostate. The Ki67-labeling index of prostate basal epithelial cells was significantly increased after castration. The number of basal epithelial cells decreased to baseline after androgen replacement. After castration, mRNA expression levels of specific growth factors, such as Fgf2, Fgf7, Hgf, Tgfa, and Tgfb, were relatively abundant in whole mouse DLPs. In organ culture experiments, basal epithelial proliferation was recapitulated in the absence of dihydrotestosterone (DHT). The proliferation of basal epithelial cells in the absence of DHT was suppressed by treatment with an FGF receptor inhibitor (PD173074). Moreover, FGF2 treatment directly stimulated the proliferation of basal epithelial cells. Taken together, these data indicated that the FGF2-FGF receptor signal cascade in the prostate gland may be one of the pathways stimulating the proliferation of basal epithelial cells in the absence of androgens.

Surface CD24 distinguishes between low differentiated and transit-amplifying cells in the basal layer of human prostate

BACKGROUND

Benign prostatic hyperplasia (BPH) and prostate cancer (PCa) are common abnormalities in elderly men. It is considered that epithelial stem cells are involved in the etiology and development of both diseases. To distinguish aberrant from normal cells, the knowledge about primary epithelial stem/progenitor cells (ES/P) is essential. The aim of this study was to examine the role of surface markers to distinguish between different subsets of prostate basal epithelium.

METHODS

The expression pattern of prostate tissue single cell suspensions was analyzed by flow cytometry using different markers. Sorted cell populations were examined for their clonogenic capacity and the resulted colonies were analyzed with flow cytometry, Western blot, and qPCR for stem cell, basal, and luminal epithelium markers. Additionally, the histological localization of the examined markers was determined using immunofluorescence.

RESULTS

Using the combination of CD49f, Trop-2, and surface CD24, basal cell subsets with distinct differentiation capacities were dissected (CD49f(+) Trop-2(+) CD24(-) and CD49f(+) Trop-2(+) CD24(+) ). Although cells from the two subsets gave rise to similar basal colonies, qPCR of primary tissue revealed that higher levels of basal marker expression were detected in the CD49f(+) Trop-2(+) CD24(-) subset. Immunofluorescence analysis showed a prominent expression of CD24 by luminal and basal cells.

CONCLUSIONS

Subsets with distinct differentiation capacities within the basal epithelium (CD49f(+) Trop-2(+) CD24(-) and CD49f(+) Trop-2(+) CD24(+) ) can be distinguished in human prostate. CD24 is a marker expressed on the basal transit-amplifying cells (transition cells) and may play a role in the differentiation and migration of ES/P cells to the luminal layer. The knowledge of this mechanism is of relevance for treatment of both diseases.

p63-expressing cells are the stem cells of developing prostate, bladder, and colorectal epithelia

The tumor protein p63 (p63), and more specifically the NH2-terminal truncated (ΔN) p63 isoform, is a marker of basal epithelial cells and is required for normal development of several epithelial tissues, including the bladder and prostate glands. Although p63-expressing cells are proposed to be the stem cells of the developing prostate epithelium and bladder urothelium, cell lineages in these endoderm-derived epithelia remain highly controversial, and rigorous lineage tracing studies are warranted. Here, we generated knock-in mice expressing Cre recombinase (Cre) under the control of the endogenous ΔNp63 promoter. Heterozygote ΔNp63(+/Cre) mice were phenotypically normal and fertile. Cre-mediated recombination in ΔNp63(+/Cre);ROSA26(EYFP) reporter mice faithfully recapitulated the pattern of ΔNp63 expression and were useful for genetic lineage tracing of ΔNp63-expressing cells of the caudal endoderm in vivo. We found that ΔNp63-positive cells of the urogenital sinus generated all epithelial lineages of the prostate and bladder, indicating that these cells represent the stem/progenitor cells of those epithelia during development. We also observed ΔNp63 expression in caudal gut endoderm and the contribution of ΔNp63-positive cells to the stem/progenitor compartment of adult colorectal epithelium. Because p63 is a master regulator of stratified epithelial development, this finding provides a unique developmental insight into the cell of origin of squamous cell metaplasia and squamous cell carcinoma of the colon.

Genetically engineered mouse models of prostate cancer

Despite major improvement in treatment of early stage localised prostate cancer, the distinction between indolent tumors and those that will become aggressive, as well as the lack of efficient therapies of advanced prostate cancer, remain major health problems. Genetically engineered mice (GEM) have been extensively used to investigate the molecular and cellular mechanisms underlying prostate tumor initiation and progression, and to evaluate new therapies. Moreover, the recent development of conditional somatic mutagenesis in the mouse prostate offers the possibility to generate new models that more faithfully reproduce the human disease, and thus should contribute to improve diagnosis and treatments. The strengths and weaknesses of various models will be discussed, as well as future opportunities.

Beta-catenin (CTNNB1) induces Bmp expression in urogenital sinus epithelium and participates in prostatic bud initiation and patterning

Fetal prostate development is initiated by androgens and patterned by androgen dependent and independent signals. How these signals integrate to control epithelial cell differentiation and prostatic bud patterning is not fully understood. To test the role of beta-catenin (Ctnnb1) in this process, we used a genetic approach to conditionally delete or stabilize Ctnnb1 in urogenital sinus (UGS) epithelium from which the prostate derives. Two opposing mechanisms of action were revealed. By deleting Ctnnb1, we found it is required for separation of UGS from cloaca, emergence or maintenance of differentiated UGS basal epithelium and formation of prostatic buds. By genetically inducing a patchy subset of UGS epithelial cells to express excess CTNNB1, we found its excess abundance increases Bmp expression and leads to a global impairment of prostatic bud formation. Addition of NOGGIN partially restores prostatic budding in UGS explants with excess Ctnnb1. These results indicate a requirement for Ctnnb1 in UGS basal epithelial cell differentiation, prostatic bud initiation and bud spacing and suggest some of these actions are mediated in part through activation of BMP signaling.

Recent advances in prostate development and links to prostatic diseases

The prostate is a branched ductal-acinar gland that is part of the male reproductive tract. Prostate development depends upon the integration of steroid hormone signals, paracrine interactions between the stromal and epithelial tissue layers, and the actions of cell autonomous factors. Several genes and signaling pathways are known to be required for one or more steps of prostate development including epithelial budding, duct elongation, branching morphogenesis, and/or cellular differentiation. Recent progress in the field of prostate development has included the application of genome-wide technologies including serial analysis of gene expression, expression profiling microarrays, and other large-scale approaches to identify new genes and pathways that are essential for prostate development. The aggregation of experimental results into online databases by organized multilab projects including the Genitourinary Developmental Molecular Atlas Project has also accelerated the understanding of molecular pathways that function during prostate development and identified links between prostate anatomy and molecular signaling. Rapid progress has also recently been made in understanding the nature and role of candidate stem cells in the developing and adult prostate. This has included the identification of putative prostate stem cell markers, lineage tracing, and organ reconstitution studies. However, several issues regarding their origin, precise nature, and possible role(s) in disease remain unresolved. Nevertheless, several links between prostatic developmental mechanisms and the pathogenesis of prostatic diseases including benign prostatic hyperplasia and prostate cancer have led to recent progress on targeting developmental pathways as therapeutic strategies for these diseases.

Sox9 is required for prostate development and prostate cancer initiation

Prostate cancer is one of the most common malignancies and the second leading cause of death from cancer in men. The molecular mechanisms driving prostate carcinogenesis are complex; with several lines of evidence suggesting that the re-expression of conserved developmental programs plays a key role. In this study, we used conditional gene targeting and organ grafting, to describe conserved roles for the transcription factor Sox9 in the initiation of both prostate organogenesis and prostate carcinogenesis in murine models. Abrogation of Sox9 expression prior to the initiation of androgen signaling blocks the initiation of prostate development. Similarly, Sox9 deletion in two genetic models of prostate cancer (TRAMP and Hi-Myc) prevented cancer initiation. Expression profiling of Sox9-null prostate epithelial cells revealed that the role of Sox9 in the initiation of prostate development may relate to its regulation of multiple cytokeratins and cell adherence/polarity. Due to its essential role in cancer initiation, manipulation of Sox9 targets in at-risk men may prove useful in the chemoprevention of prostate cancer.

Multipotent and unipotent progenitors contribute to prostate postnatal development

The prostate is a glandular epithelium composed of basal, luminal and neuroendocrine cells that originate from the urogenital sinus during embryonic development. After birth, the prostate keeps developing until the end of puberty. Here, we used inducible genetic lineage tracing experiments in mice to investigate the cellular hierarchy that governs prostate postnatal development. We found that prostate postnatal development is mediated by basal multipotent stem cells that differentiate into basal, luminal and neuroendocrine cells, as well as by unipotent basal and luminal progenitors. Clonal analysis of basal cells revealed the existence of bipotent and unipotent basal progenitors as well as basal cells already committed to the luminal lineage with intermediate cells co-expressing basal and luminal markers associated with this commitment step. The existence of multipotent basal progenitors during prostate postnatal development contrasts with the distinct pools of unipotent basal and luminal stem cells that mediate adult prostate regeneration. Our results uncover the cellular hierarchy acting during prostate development and will be instrumental in defining the cellular origin and the mechanisms underlying prostate cancer initiation.

Identification of CD166 as a surface marker for enriching prostate stem/progenitor and cancer initiating cells

New therapies for late stage and castration resistant prostate cancer (CRPC) depend on defining unique properties and pathways of cell sub-populations capable of sustaining the net growth of the cancer. One of the best enrichment schemes for isolating the putative stem/progenitor cell from the murine prostate gland is Lin^-;Sca1⁺;CD49f^hi (LSC^hi), which results in a more than 10-fold enrichment for in vitro sphere-forming activity. We have shown previously that the LSC^hi subpopulation is both necessary and sufficient for cancer initiation in the Pten-null prostate cancer model. To further improve this enrichment scheme, we searched for cell surface molecules upregulated upon castration of murine prostate and identified CD166 as a candidate gene. CD166 encodes a cell surface molecule that can further enrich sphere-forming activity of WT LSC^hi and Pten null LSC^hi. Importantly, CD166 could enrich sphere-forming ability of benign primary human prostate cells in vitro and induce the formation of tubule-like structures in vivo. CD166 expression is upregulated in human prostate cancers, especially CRPC samples. Although genetic deletion of murine CD166 in the Pten null prostate cancer model does not interfere with sphere formation or block prostate cancer progression and CRPC development, the presence of CD166 on prostate stem/progenitors and castration resistant sub-populations suggest that it is a cell surface molecule with the potential for targeted delivery of human prostate cancer therapeutics.

β1 integrin deletion enhances progression of prostate cancer in the TRAMP mouse model

β1 integrin regulates the response of both normal and cancer cells to their local environment. Although mis-localised in prostate cancer, the role β1 integrin plays in prostate development and carcinogenesis remains unknown. To assess the role of β1 integrin in vivo, we conditionally deleted β1 integrin from prostate epithelium and subsequently crossed these mice to the TRAMP prostate carcinogenesis model. Deletion of β1 integrin following castration and subsequent androgen supplementation resulted in an expansion of the p63-positive basal cell population and decreased differentiation. Consistent with these findings, deletion of β1 integrin in TRAMP mice decreased animal survival, decreased retention of normal prostate morphology, increased the percentage of tissue with poorly differentiated carcinoma, and increased cell proliferation. This study demonstrates that β1 integrin regulates several aspects of normal prostate development and in contrast to its role in several other tissues, its loss is associated with increased rates of prostate tumour progression.

Estrogen receptor β activation impairs prostatic regeneration by inducing apoptosis in murine and human stem/progenitor enriched cell populations

Androgen depletion is the primary treatment for prostate disease; however, it fails to target residual castrate-resistant cells that are regenerative and cells of origin of prostate cancer. Estrogens, like androgens, regulate survival in prostatic cells, and the goal of this study was to determine the advantages of selective activation of estrogen receptor β (ERβ) to induce cell death in stem cells that are castrate-resistant. Here we show two cycles of short-term ERβ agonist (8β-VE2) administration this treatment impairs regeneration, causing cystic atrophy that correlates with sustained depletion of p63+ basal cells. Furthermore, agonist treatment attenuates clonogenicity and self-renewal of murine prostatic stem/progenitor cells and depletes both murine (Lin(-)Sca1(+)CD49f(hi)) and human (CD49f(hi)Trop2(hi)) prostatic basal cells. Finally, we demonstrate the combined added benefits of selective stimulation of ERβ, including the induction of cell death in quiescent post-castration tissues. Subsequent to castration ERβ-induces further apoptosis in basal, luminal and intermediate cells. Our results reveal a novel benefit of ERβ activation for prostate disease and suggest that combining selective activation of ERβ with androgen-deprivation may be a feasible strategy to target stem cells implicated in the origin of prostatic disease.

Prostate cancer stem cells

Stem cells have long been implicated in prostate gland formation. The prostate undergoes regression after androgen deprivation and regeneration after testosterone replacement. Regenerative studies suggest that these cells are found in the proximal ducts and basal layer of the prostate. Many characteristics of prostate cancer indicate that it originates from stem cells. For example, the putative androgen receptor-negative (AR(-)) status of prostate stem cells renders them inherently insensitive to androgen blockade therapy. The androgen-regulated gene fusion TMPRSS2-ERG could be used to clarify both the cells of origin and the evolution of prostate cancer cells. In this review, we show that the hypothesis that distinct subtypes of cancer result from abnormalities within specific cell types-the stem cell theory of cancer-may instigate a major paradigm shift in cancer research and therapy. Ultimately, the stem cell theory of cancers will affect how we practice clinical oncology: our diagnosis, monitoring, and therapy of prostate and other cancers.

Morphologic manifestations of gene-specific molecular alterations ("genetic addictions") in mouse models of disease

Neoplasia in both animals and humans results in part from lasting activation of tumor-promoting genes ("oncogenes") or diminished function of genes responsible for preventing neoplastic induction ("tumor suppressor genes"). The concept of "genetic addiction" has emerged to indicate that neoplastic cells cannot maintain a malignant phenotype without sustained genotypic abnormalities related to aberrant activity of oncogene(s) and/or inactivity of tumor suppressor gene(s). Interestingly, some genetic abnormalities reliably produce distinct morphologic patterns that can be used as structural signatures indicating the presence of a specific molecular alteration. Examples of such consistent genetic/microanatomic pairings have been identified for mutated oncogenes, such as rising mucin-producing capacity with RAS overexpression, and mutated tumor suppressor genes-including PTEN eliciting cell hypertrophy, RB1 dictating neuroendocrine differentiation, and TRP53 encouraging sarcomatous transformation. Familiarity with the concept of genetic addiction, as well as the ability to recognize such regular genomic-phenotypic relationships, are of paramount importance for comparative pathologists who are engaged in phenotyping genetically engineered mice to help unravel genomic intricacies in both health and disease.

Prostate cancer stem cells

The Cancer Stem Cells (CSCs) hypothesis postulates that a minute subpopulation of cells is accountable for cancer initiation and progression. Unlike the stochastic and clonal evolution models, the CSC theory proposes that tumours are hierarchical and only the rare subset of cells at the top of the 'stemness hierarchy tree’ are adequately ‘equipped’ biologically to initiate and drive tumourigenesis. CSCs have been implicated in various solid malignancies including prostate cancer (PCa), where their existence seems to provide an explanation for the failure of tumour eradicating therapies. As CSCs are thought to share many properties with normal stem cells, understanding normal stem cells should shed light on the pathomechanisms of cancer and, importantly, on potential therapeutic interventions. The purpose of this paper is to review the existing data on CSCs in PCa, their putative phenotypic markers, potential role in tumour biology and relevance to therapy.

Prostate cancer stem cells: do they have a basal or luminal phenotype?

The prostate is a luminal secretory tissue whose function is regulated by male sex hormones. Castration produces involution of the prostate to a reversible basal state, and as the majority of prostate cancers also have a luminal phenotype, drug-induced castration is a front line therapy. It has therefore been assumed that the tumor arises from transformation of a luminal progenitor cell. Here, we demonstrate that a minority basal "cancer stem cell" (CSC) population persists in primary human prostate cancers, as in normal prostate, serving as a reservoir for tumor recurrence after castration therapy. While the CSCs exhibit a degree of phenotypic fluidity from different patients, the tumor-initiating cells in immunocompromised mice express basal markers (such as p63), but do not express androgen receptor (AR) or markers of luminal differentiation (PSA, PAP) when freshly fractionated from human tissues or following culture in vitro. Estrogen receptors α and β and AR are transcriptionally active in the transit amplifying (TA) cell (the progeny of SC). However, AR protein is consistently undetectable in TA cells. The prostate-specific TMPRSS2 gene, while upregulated by AR activity in luminal cells, is also transcribed in basal populations, confirming that AR acts as an expression modulator. Selected cells with basal phenotypes are tumor initiating, but the resultant tumors are phenotypically intermediate, with focal expression of AR, AMACR, and p63. In vitro differentiation experiments, employing lentivirally transduced SCs with a luminal (PSA-probasin) promoter regulating a fluorescent indicator gene, confirm that the basal SCs are the source of luminal progeny.

In situ lineage tracking of human prostatic epithelial stem cell fate reveals a common clonal origin for basal and luminal cells

Stem cells accumulate mitochondrial DNA (mtDNA) mutations resulting in an observable respiratory chain defect in their progeny, allowing the mapping of stem cell fate. There is considerable uncertainty in prostate epithelial biology where both basal and luminal stem cells have been described, and in this study the clonal relationships within the human prostate epithelial cell layers were explored by tracing stem cell fate. Fresh-frozen and formalin-fixed histologically-benign prostate samples from 35 patients were studied using sequential cytochrome c oxidase (COX)/succinate dehydrogenase (SDH) enzyme histochemistry and COX subunit I immunofluorescence to identify areas of respiratory chain deficiency; mtDNA mutations were identified by whole mitochondrial genome sequencing of laser-captured areas. We demonstrated that cells with respiratory chain defects due to somatic mtDNA point mutations were present in prostate epithelia and clonally expand in acini. Lineage tracing revealed distinct patterning of stem cell fate with mtDNA mutations spreading throughout the whole acinus or, more commonly, present as mosaic acinar defects. This suggests that individual acini are typically generated from multiple stem cells, and the presence of whole COX-deficient acini suggests that a single stem cell can also generate an entire branching acinar subunit of the gland. Significantly, a common clonal origin for basal, luminal and neuroendocrine cells is demonstrated, helping to resolve a key area of debate in human prostate stem cell biology.

Regenerated luminal epithelial cells are derived from preexisting luminal epithelial cells in adult mouse prostate

Determining the source of regenerated luminal epithelial cells in the adult prostate during androgen deprivation and replacement will provide insights into the origin of prostate cancer cells and their fate during androgen deprivation therapy. Prostate stem cells in the epithelial layer have been suggested to give rise to luminal epithelium. However, the extent of stem cell participation to prostate regrowth is not clear. In this report, using prostate-specific antigen-CreER(T2)-based genetic lineage marking/tracing in mice, preexisting luminal epithelial cells were shown to be a source of regenerated luminal epithelial cells in the adult prostate. Prostatic luminal epithelial cells could survive androgen deprivation and were capable of proliferating upon androgen replacement. Prostate cancer cells, typically exhibiting a luminal epithelial phenotype, may retain this intrinsic capability to survive and regenerate in response to changes in androgen signaling, providing part of the mechanism for the ultimate failure of androgen deprivation therapy in prostate cancer.

Epithelial Bmp (Bone morphogenetic protein) signaling for bulbourethral gland development: a mouse model for congenital cystic dilation

The bulbourethral gland (BUG) is a male-specific organ, which secretes part of the semen fluid. As the BUG is located in the deep pelvic floor, its developmental process is still unclear. Bone morphogenetic protein (Bmp) signaling plays pivotal roles in various organs. However, the function of Bmp signaling for BUG development is still unclear. The present study aimed to elucidate the role of Bmp signaling in the development of the BUG. We observed the prominent nuclear accumulation of phosphorylated (p) SMAD1/5/8, the downstream molecules of Bmp signaling, during BUG epithelial development. These results suggest that Bmp signaling contributes to BUG development. Bmp receptor1a (Bmpr1a) is known as the major type 1 signal transducer in some organogeneses. To analyze the Bmp signaling function for BUG development, we examined epithelial cell-specific Bmpr1a gene conditional mutant mice utilizing the tamoxifen-inducible Cre recombinase system. We observed cystic dilation and epithelial hyperplasia of the BUG in the Bmpr1a conditional knockout mice. The mutant cystic BUG specimens also showed inflammatory lesions. These BUG abnormalities resembled some of the BUG malformations observed in human congenital syndromes. The current study suggests that Bmp signaling possesses an essential role in BUG development and homeostasis. This would be the first report showing that the mutation of the Bmpr1a gene in the BUG epithelia phenocopied some abnormalities of human congenital syndromes affecting the BUG duct.

Smooth muscle cell-specific knockout of androgen receptor: a new model for prostatic disease

Androgen-driven stromal-epithelial interactions play a key role in normal prostate development and function as well as in the progression of common prostatic diseases such as benign prostatic hyperplasia and prostate cancer. However, exactly how, and via which cell type, androgens mediate their effects in the adult prostate remains unclear. This study investigated the role for smooth muscle (SM) androgen signaling in normal adult prostate homeostasis and function using mice in which androgen receptor was selectively ablated from prostatic SM cells. In adulthood the knockout (KO) mice displayed a 44% reduction in prostate weight and exhibited histological abnormalities such as hyperplasia, inflammation, fibrosis, and reduced expression of epithelial, SM, and stem cell identify markers (e.g. p63 reduced by 27% and Pten by 31%). These changes emerged beyond puberty and were not explained by changes in serum hormones. Furthermore, in response to exogenous estradiol, adult KO mice displayed an 8.5-fold greater increase in prostate weight than controls and developed urinary retention. KO mice also demonstrated a reduced response to castration compared with controls. Together these results demonstrate that prostate SM cells are vital in mediating androgen-driven stromal-epithelial interactions in adult mouse prostates, determining cell identity and function and limiting hormone-dependent epithelial cell proliferation. This novel mouse model provides new insight into the possible role for SM androgen action in prostate disease.

Clonal architecture of human prostatic epithelium in benign and malignant conditions

The location of stem cells in the epithelium of the prostatic acinus remains uncertain, as does the cellular origin of prostatic neoplasia. Here, we apply lineage tracing to visualize the clonal progeny of stem cells in benign and malignant human prostates and understand the clonal architecture of this epithelium. Cells deficient for the mitochondrially-encoded enzyme cytochrome c oxidase (CCO) were identified in 27 frozen prostatectomy specimens using dual colour enzyme histochemistry and individual CCO-normal and -deficient cell areas were laser-capture microdissected. PCR-sequencing of the entire mitochondrial genome (mtDNA) of cells from CCO-deficient areas found to share mtDNA mutations not present in adjacent CCO-normal cells, thus proving a clonal origin. Immunohistochemistry was performed to visualize the three cell lineages normally present in the prostatic epithelium. Entire CCO-deficient acini, and part-deficient acini were found. Deficient patches spanned either basal or luminal cells, but sometimes also both epithelial cell types in normal, hyperplastic or atrophic epithelium, and prostatic intraepithelial neoplasia (PIN). Patches comprising both PIN and invasive cancer were observed. Each cell area within a CCO-deficient patch contained an identical mtDNA mutation, defining the patch as a clonal unit. CCO-deficient patches in benign epithelium contained basal, luminal and endocrine cells, demonstrating multilineage differentiation and therefore the presence of a stem cell. Our results demonstrate that the normal, atrophic, hypertrophic and atypical (PIN) epithelium of human prostate contains stem cell-derived clonal units that actively replenish the epithelium during ageing. These deficient areas usually included the basal compartment indicating the basal layer as the location of the stem cell. Importantly, single clonal units comprised both PIN and invasive cancer, supporting PIN as the pre-invasive lesion for prostate cancer.

Differentiation of the ductal epithelium and smooth muscle in the prostate gland are regulated by the Notch/PTEN-dependent mechanism

We have shown previously that during branching morphogenesis of the mouse prostate gland, Bone morphogenetic protein 7 functions to restrict Notch1-positive progenitor cells to the tips of the prostate buds. Here, we employed prostate-specific murine bi-genic systems to investigate the effects of gain and loss of Notch function during prostate development. We show that Nkx3.1(Cre) and Probasin(Cre) alleles drive expression of Cre recombinase to the prostate epithelium and periepithelial stroma. We investigated the effects of gain of Notch function using the Rosa(NI1C) conditional allele, which carries a constitutively active intracellular domain of Notch1 receptor. We carried out the analysis of loss of Notch function in Nkx3.1(Cre/+);RBP-J(flox/flox) prostates, where RBP-J is a ubiquitous transcriptional mediator of Notch signaling. We found that gain of Notch function resulted in inhibition of the tumor suppressor PTEN, and increase in cell proliferation and progenitor cells in the basal epithelium and smooth muscle compartments. In turn, loss of Notch/RBP-J function resulted in decreased cell proliferation and loss of epithelial and smooth muscle progenitors. Gain of Notch function resulted in an early onset of benign prostate hyperplasia by three months of age. Loss of Notch function also resulted in abnormal differentiation of the prostate epithelium and stroma. In particular, loss of Notch signaling and increase in PTEN promoted a switch from myoblast to fibroblast lineage, and a loss of smooth muscle. In summary, we show that Notch signaling is necessary for terminal differentiation of the prostate epithelium and smooth muscle, and that during normal prostate development Notch/PTEN pathway functions to maintain patterned progenitors in the epithelial and smooth muscle compartments. In addition, we found that both positive and negative modulation of Notch signaling results in abnormal organization of the prostate tissue, and can contribute to prostate disease in the adult organ.

Essential roles of androgen signaling in Wolffian duct stabilization and epididymal cell differentiation

The epididymis is a male accessory organ and functions for sperm maturation and storage under the control of androgen. The development of the epididymis is also androgen dependent. The Wolffian duct (WD), anlagen of the epididymis, is formed in both male and female embryos; however, it is stabilized only in male embryos by testicular androgen. Androgen drives subsequent differentiation of the WD into the epididymis. Although the essential roles of androgen in WD masculinization and epididymal function have been established, little is known about cellular events regulated precisely by androgen signaling during these processes. It is also unclear whether androgen signaling, especially in the epithelia, has further function for epididymal epithelial cell differentiation. In this study we examined the cellular death and proliferation controlled by androgen signaling via the androgen receptor (AR) in WD stabilization. Analyses using AR knockout mice revealed that androgen signaling inhibits epithelial cell death in this process. Analysis of AP2α-Cre;AR(flox/Y) mice, in which AR function is deleted in the WD epithelium, revealed that epithelial AR is not required for the WD stabilization but is required for epithelial cell differentiation in the epididymis. Specifically, loss of epithelial AR significantly reduced expression of p63 that is essential for differentiation of basal cells in the epididymal epithelium. We also interrogated the possibility of regulation of the p63 gene (Trp63) by AR in vitro and found that p63 is a likely direct target of AR regulation.

Hedgehog overexpression leads to the formation of prostate cancer stem cells with metastatic property irrespective of androgen receptor expression in the mouse model

Background

Hedgehog signalling has been implicated in prostate tumorigenesis in human subjects and mouse models, but its effects on transforming normal basal/stem cells toward malignant cancer stem cells remain poorly understood.

Methods

We produced pCX-shh-IG mice that overexpress Hedgehog protein persistently in adult prostates, allowing for elucidation of the mechanism during prostate cancer initiation and progression. Various markers were used to characterize and confirm the transformation of normal prostate basal/stem cells into malignant cancer stem cells under the influence of Hedgehog overexpression.

Results

The pCX-shh-IG mice developed prostatic intraepithelial neoplasia (PIN) that led to invasive and metastatic prostate cancers within 90 days. The prostate cancer was initiated through activation of P63⁺ basal/stem cells along with simultaneous activation of Hedgehog signalling members, suggesting that P63⁺/Patch1⁺ and P63⁺/Smo⁺ cells may serve as cancer-initiating cells and progress into malignant prostate cancer stem cells (PCSCs). In the hyperplastic lesions and tumors, the progeny of PCSCs differentiated into cells of basal-intermediate and intermediate-luminal characteristics, whereas rare ChgA⁺ neuroendocrine differentiation was seen. Furthermore, in the metastatic loci within lymph nodes, kidneys, and lungs, the P63⁺ PCSCs formed prostate-like glandular structures, characteristic of the primitive structures during early prostate development. Besides, androgen receptor (AR) expression was detected heterogeneously during tumor progression. The existence of P63⁺/AR^-, CK14⁺/AR^- and CD44⁺/AR^- progeny indicates direct procurement of AR^- malignant cancer trait.

Conclusions

These data support a cancer stem cell scenario in which Hedgehog signalling plays important roles in transforming normal prostate basal/stem cells into PCSCs and in the progression of PCSCs into metastatic tumor cells.

Tumour-initiating stem-like cells in human prostate cancer exhibit increased NF-κB signalling

Androgen depletion is a key strategy for treating human prostate cancer, but the presence of hormone-independent cells escaping treatment remains a major therapeutic challenge. Here, we identify a minor subset of stem-like human prostate tumour-initiating cells (TICs) that do not express prostate cancer markers, such as androgen receptor or prostate specific antigen. These TICs possess stem cell characteristics and multipotency as demonstrated by in vitro sphere-formation and in vivo tumour-initiation, respectively. The cells represent an undifferentiated subtype of basal cells and can be purified from prostate tumours based on coexpression of the human pluripotent stem cell marker TRA-1-60 with CD151 and CD166. Such triple-marker-positive TICs recapitulate the original parent tumour heterogeneity in serial xeno-transplantations indicating a tumour cell hierarchy in human prostate cancer development. These TICs exhibit increased nuclear factor-κB activity. These findings are important in understanding the molecular basis of human prostate cancer.

Tumours consist of heterogeneous cell types that respond differently to treatment. Here, on the basis of the expression of three different proteins, the authors describe a subset of prostate cancer cells that have stem cell-like properties that are able to initiate tumour formation in vivo.

Epithelial cell-targeted transgene expression enables isolation of cyan fluorescent protein (CFP)-expressing prostate stem/progenitor cells

To establish a method for efficient and relatively easy isolation of a cell population containing epithelial prostate stem cells, we developed two transgenic mouse models, K5/CFP and K18/RFP. In these models, promoters of the cytokeratin 5 (Krt5) and the cytokeratin 18 (Krt18) genes regulate cyan and red fluorescent proteins (CFP and RFP), respectively. CFP and RFP reporter protein fluorescence allows for visualization of K5(+) and K18(+) epithelial cells within the cellular spatial context of the prostate gland and for their direct isolation by FACS. Using these models, it is possible to test directly the stem cell properties of prostate epithelial cell populations that are positively selected based on expression of cytoplasmic proteins, K5 and K18. After validating appropriate expression of the K5/CFP and K18/RFP transgenes in the developing and adult prostate, we demonstrate that a subset of CFP-expressing prostate cells exhibits stem cell proliferation potential and differentiation capabilities. Then, using prostate cells sorted from double transgenic mice (K5/CFP + K18/RFP), we compare RNA microarrays of sorted K5(+)K18(+) basal and K5(-)K18(+) luminal epithelial cells, and identify genes that are differentially expressed. Several genes that are over-expressed in K5(+) cells have previously been identified as potential stem cell markers. These results suggest that FACS isolation of prostate cells from these mice based on combining reporter gene fluorescence with expression of potential stem cell surface marker proteins will yield populations of cells enriched for stem cells to a degree that has not been attained by using cell surface markers alone.

Development of thyroid gland and ultimobranchial body cyst is independent of p63

The ultimobranchial body (UBB) and thyroid primordium are the origins of the thyroid gland that fuse around embryonic day 14.5 of mouse gestation, ultimately giving rise to calcitonin-producing C cells and thyroglobulin-producing follicular cells, respectively. A homeodomain transcription factor NKX2-1 is expressed both in the UBB and the thyroid primordium, and is critical for development of the thyroid gland. In this study, the role of p63 in development of UBB and the thyroid gland was analyzed by histological, immunohistochemical, and electron microscopic analyses using mice with various combinations of Nkx2-1 and p63 wild-type, heterozygous, and null alleles. In the absence of p63, a normal thyroid gland develops, as revealed by expression of thyroglobulin and calcitonin, thus showing that p63 is not required for thyroid development. However, in mice carrying the Nkx2-1-null allele, the UBB remains as a cystic vesicular structure and/or in nested patterns consisting of p63-positive cells surrounding the vesicle and undifferentiated immature cells with occasional cilia lying inside. The cystic UBB was present even in the Nkx2-1;p63 double-null mice. The structure and p63 expression pattern of the UBB cyst strikingly resemble the solid cell nest. These results show that in the absence of NKX2-1, UBB becomes cystic independent of p63, which is likely the origin of SCN.

Revisiting the concept of cancer stem cells in prostate cancer

The cancer stem cell (CSC) model proposes that cells within a tumor are organized in a hierarchical lineage relationship and display different tumorigenic potential, suggesting that effective therapeutics should target rare CSCs that sustain tumor malignancy. Here we review the current status of studies to identify CSCs in human prostate cancer as well as mouse models, with an emphasis on discussing different functional assays and their advantages and limitations. We also describe current controversies regarding the identification of prostate epithelial stem cells and cell types of origin for prostate cancer, and present potential resolutions of these issues. Although definitive evidence for the existence of CSCs in prostate cancer is still lacking, future directions pursuing the identification of tumor-initiating stem cells in the mouse may provide important advances in evaluating the CSC model for prostate cancer.

Molecular genetics of prostate cancer: new prospects for old challenges

Despite much recent progress, prostate cancer continues to represent a major cause of cancer-related mortality and morbidity in men. Since early studies on the role of the androgen receptor that led to the advent of androgen deprivation therapy in the 1940s, there has long been intensive interest in the basic mechanisms underlying prostate cancer initiation and progression, as well as the potential to target these processes for therapeutic intervention. Here, we present an overview of major themes in prostate cancer research, focusing on current knowledge of principal events in cancer initiation and progression. We discuss recent advances, including new insights into the mechanisms of castration resistance, identification of stem cells and tumor-initiating cells, and development of mouse models for preclinical evaluation of novel therapuetics. Overall, we highlight the tremendous research progress made in recent years, and underscore the challenges that lie ahead.

Effect of transforming growth factor α overexpression on urogenital organ development in mouse

Transforming growth factor-α (TGFα) promotes cell proliferation by binding to the epidermal growth factor receptor (EGFR). TGFα and EGFR overexpression have been reported in various human cancers. However, whether TGFα induces cancer by itself is unknown in urogenital organs. To investigate whether TGFα overexpression induces carcinogenesis in urogenital organs, we analyzed the phenotypes of urogenital organs in male TGFα transgenic (TG) mice of the CD1 strain. Urogenital organs including the kidney, bladder, prostate, seminal vesicles, testes, and epididymis were isolated from 4- to 48-week-old TGFα TG and wild-type (WT) CD1 mice. Prostates were separated into anterior prostate (AP), dorsolateral prostate (DLP), and ventral prostate (VP). Neither tumor formation nor epithelial hyperplasia was observed in the TGFα TG mouse urogenital organs that we have investigated. Histopathologically, in prostate, we found an increased number of p63-positive basal epithelial cells in the TGFα TG mice AP and DLP. There was no morphological change in the stromal component, such as hypercellular stroma or fibrosis. However, bladder weight was greater in TGFα TG mice than that in WT mice, and distended bladders were observed macroscopically in 19 of 20 TGFα TG mice over 20 weeks of age. Ki67 labeling index was increased significantly in the TGFα TG mouse urethral epithelium, whereas neither epithelial hyperplasia nor hypertrophy was observed. In conclusion, our results suggest that TGFα overexpression in mouse urogenital organs alone may not be responsible for tumor formation and epithelial hyperplasia, but is involved in bladder outlet obstruction.

A constitutively activated form of the p110beta isoform of PI3-kinase induces prostatic intraepithelial neoplasia in mice

Recent work has shown that ablation of p110beta, but not p110alpha, markedly impairs tumorigenesis driven by loss of phosphatase and tensin homolog (PTEN) in the mouse prostate. Other laboratories have reported complementary data in human prostate tumor lines, suggesting that p110beta activation is necessary for tumorigenesis driven by PTEN loss. Given the multiple functions of PTEN, we wondered if p110beta activation also is sufficient for tumorigenesis. Here, we report that transgenic expression of a constitutively activated p110beta allele in the prostate drives prostate intraepithelial neoplasia formation. The resulting lesions are similar to, but are clearly distinct from, the ones arising from PTEN loss or Akt activation. Array analyses of transcription in multiple murine prostate tumor models featuring PI3K/AKT pathway activation allowed construction of a pathway signature that may be useful in predicting the prognosis of human prostate tumors.

Epithelial stem/progenitor cells in the embryonic mouse submandibular gland

Salivary gland organogenesis involves the specification, maintenance, lineage commitment, and differentiation of epithelial stem/progenitor cells. Identifying how stem/progenitor cells are directed along a series of cell fate decisions to form a functional salivary gland will be necessary for future stem cell regenerative therapy. The identification of stem/progenitor cells within the salivary gland has focused on their role in postnatal glands and little is known about them in embryonic glands. Here, we have reviewed the information available for other developing organ systems and used it to determine whether similar cell populations exist in the mouse submandibular gland. Additionally, using growth factors that influence salivary gland epithelial morphogenesis during development, we have taken a simple experimental approach asking whether any of these growth factors influence early developmental lineages within the salivary epithelium on a transcriptional level. These preliminary findings show that salivary epithelial stem/progenitor populations exist within the gland, and that growth factors that are reported to control epithelial morphogenesis may also impact cell fate decisions. Further investigation of the signaling networks that influence stem/progenitor cell behavior will allow us to hypothesize how we might induce autologous stem cells to regenerate damaged salivary tissue in a therapeutic context.

Neoplastic stem cells: current concepts and clinical perspectives

Neoplastic stem cells have initially been characterized in myeloid leukemias where NOD/SCID mouse-repopulating progenitors supposedly reside within a CD34+/Lin- subset of the malignant clone. These progenitors are considered to be self-renewing cells responsible for the in vivo long-term growth of neoplastic cells in leukemic patients. Therefore, these cells represent an attractive target of therapy. In some lymphoid leukemias, NOD/SCID mouse-repopulating cells were also reported to reside within the CD34+/Lin- subfraction of the clone. More recently, several attempts have been made to transfer the cancer stem cell concept to solid tumors and other non-hematopoietic neoplasms. In several of these tumors, the cell surface antigens AC133 (CD133) and CD44 are considered to indicate the potential of a cell to initiate permanent tumor formation in vivo. However, several questions concerning the phenotype, self-renewal capacity, stroma-dependence, and other properties of cancer- or leukemia-initiating cells remain to be solved. The current article provides a summary of our current knowledge on neoplastic (cancer) stem cells, with special emphasis on clinical implications and therapeutic options as well as a discussion about conceptual and technical limitations.

Proliferation and apoptotic rates and increased frequency of p63-positive cells in the prostate acinar epithelium of alloxan-induced diabetic rats

The effects of experimental type 1 diabetes were investigated in the acinar epithelium of rat ventral prostate, focusing on the rates of cell proliferation and the frequency of apoptosis and p63-positive cells. Type 1 diabetes was induced in adult male Wistar rats by a single alloxan administration (42 mg/kg b.w.) and its effects were analysed for 1 week and 3 months after the establishment of the disease. A group of diabetic rats was treated daily with 5 IU of insulin during 1 week after diabetes had been diagnosed. Immunocytochemical methods for the localization of cell proliferation antigen (PCNA), androgen receptor (AR) and p63 protein were carried out, and apoptotic cells were identified by TUNEL essay. In diabetic rats, testosterone levels reduced drastically after 1 week and in a lower degree after 3 months. In short-term diabetic rats, cell proliferation decreased, and in medium-term, epithelial apoptotic rates increased. In both periods after the onset of diabetes, the frequency of p63-positive cells doubled. Insulin treatment was effective in preventing testosterone decrease, p63-positive cell increase and apoptotic rates, but did not interfere in cell proliferation. This investigation shows that, soon after diabetes onset, there are important modifications in cell proliferation within the acinar prostatic epithelium, and in longer term, there is a marked impact on kinetics of differentiation and cell death, which may initially be attributable to an androgenic fall, but is probably also because of other factors related to diabetes, as changes are considerably different from those resulting from castration.

Modulação androgênica e estrogênica na próstata: uma abordagem em modelos experimentais de roedores com enfoque na biologia estrutural

O sistema endócrino é uma complexa rede de glândulas e hormônios que regulam muitas das funções do corpo, incluindo crescimento, desenvolvimento e maturação, como as vias de ação de muitos órgãos. A próstata é um importante alvo dos hormônios e sua maturidade funcional e seu desenvolvimento são influenciados pelos níveis de esteroides. O presente grupo de pesquisa tem estudado os potenciais efeitos dos agentes esteroides sobre a próstata masculina e feminina do gerbilo da Mongólia (Meriones unguiculatus), utilizando métodos morfológicos e imuno-histoquímicos. Os resultados têm revelado a próstata do gerbilo da Mongólia como uma importante ferramenta para estudos da ação dos hormônios esteroides e seus antagonistas.

A luminal epithelial stem cell that is a cell of origin for prostate cancer

In epithelial tissues, the lineage relationship between normal progenitor cells and cell type(s) of origin for cancer has been poorly understood. Here we show that a known regulator of prostate epithelial differentiation, the homeobox gene Nkx3.1, marks a stem cell population that functions during prostate regeneration. Genetic lineage-marking demonstrates that rare luminal cells which express Nkx3.1 in the absence of testicular androgens (castration-resistant Nkx3.1-expressing cells, CARNs) are bipotential and can self-renew in vivo, while single-cell transplantation assays show that CARNs can reconstitute prostate ducts in renal grafts. Functional assays of Nkx3.1 mutant mice in serial prostate regeneration assays suggest that Nkx3.1 is required for stem cell maintenance. Finally, targeted deletion of the Pten tumor suppressor gene in CARNs results in rapid formation of carcinoma following androgen-mediated regeneration. These observations indicate that CARNs represent a novel luminal stem cell population that is an efficient target for oncogenic transformation in prostate cancer.

The expression and diagnostic utility of p63 in the female genital tract

p63 plays a key role in epithelial development in various organs, being expressed in myoepithelial cells and in basal cells of stratified epithelia. In the female genital tract, p63 is expressed in the basal and parabasal cells of mature cervical, vaginal and vulval squamous epithelium, and also in cervical reserve cells at the transformation zone and in immature metaplastic and atrophic cervical squamous epithelium. In this review, the diagnostic utility of p63 immunohistochemical staining in various pathologic scenarios within the female genital tract is discussed. Cervical microglandular hyperplasia is p63 positive with a characteristic subcolumnar location due to expression in reserve cells. There is increased expression in cervical intraepithelial neoplasia, in accordance with the degree of dysplasia. One of the most useful applications of p63 is in the evaluation of problematic cervical carcinomas; most squamous carcinomas exhibit diffuse nuclear immunoreactivity whereas most adenocarcinomas and neuroendocrine carcinomas are negative or focally positive. In conjunction with neuroendocrine markers, p63 is useful in distinguishing between a squamous carcinoma and a small cell or large cell neuroendocrine carcinoma. In the normal endometrium, a population of p63-positive cells is present which may act as a stem cell population and which is increased in various forms of metaplasia. Placental site nodule and epithelioid trophoblastic tumor (lesions derived from chorionic-type intermediate trophoblast) are usually p63 positive whereas placental site reaction and placental site trophoblastic tumor (lesions derived from implantation site intermediate trophoblast) are usually negative; thus, p63 may be useful in the diagnostic algorithm of trophoblastic lesions. p63 positivity in ovarian epithelial tumors is uncommon and largely restricted to squamous and transitional neoplasms, including benign and borderline Brenner tumor. p63 is also positive in cervical transitional metaplasia, Walthard rests, vulval Paget disease secondary to an underlying urothelial malignancy, tubulosquamous polyp of the vagina, and ectopic prostatic tissue in the cervix.

Comprehensive mutational analysis and mRNA isoform quantification of TP63 in normal and neoplastic human prostate cells

BACKGROUND

The role of TP63 in cancer remains controversial since both oncogenic and tumor suppressive actions have been reported. p63 protein is found in the nuclei of basal cells of the normal prostate, yet it is absent in the vast majority of prostate cancer nuclei. Since a complex array of TP63 mRNA transcripts encode polypeptides with distinct functional properties, it is important to determine which forms are expressed in normal and prostate cancer tissue.

METHODS

We used real-time RT-PCR to distinguish TP63 mRNA isoforms in prostate cancer cell lines (n = 7), and samples from prostate cancer patients. We sequenced all TP63 exons from 20 primary tumors, 20 metastases, 28 tumor xenografts, and 7 prostate cancer cell lines.

RESULTS

TP63 mRNA isoforms were present in all tumors, albeit at levels lower than in normal prostate. The most abundant N-terminal variant was DeltaN; the most abundant C-terminal variant was the alpha form. The prostate tumor cell line CWR22Rv1 contained a single G to T substitution in exon 8 that is identical to a dominant-negative DNA binding inactivation mutation occurring in patients with a congenital TP63 deficiency syndrome. One patient tumor contained a somatic mutation in exon 11.

CONCLUSIONS

The pattern of TP63 mRNA expression in normal prostate tissue is retained in reduced amounts in prostate cancer, and a potentially functional TP63 mutation was identified in one prostate tumor. Thus, if TP63 is a prostate cancer gene it likely functions as a tumor suppressor. Further study of the role of TP63 isoforms in regulating stem cell functions of normal and neoplastic prostate epithelial cells is needed. Prostate 69:559-569, 2009. (c) 2009 Wiley-Liss, Inc.

Correlated alterations in prostate basal cell layer and basement membrane

Our recent studies revealed that focal basal cell layer disruption (FBCLD) induced auto-immunoreactions represented a contributing factor for human prostate tumor progression and invasion. As the basement membrane surrounds and attaches to the basal cell layer, our current study assessed whether FBCLD would impact the physical integrity of the associated basement membrane. Paraffin sections from 25-human prostate tumors were subjected to double immunohistochemistry to simultaneously elucidate the basal cell layer and the basement membrane with corresponding biomarkers. The physical integrity of the basement membrane overlying FBCLD was examined to determine the extent of correlated alterations. Of a total of 89 FBCLD encountered, 76 (85 %) showed correlated alterations in the overlying basement membrane, which included distinct focal disruptions or fragmentations. In the remaining 13 (15%) FBCLD, the overlying basement membrane showed significant attenuation or reduction of the immunostaining intensity. The basement membrane in all or nearly all ducts or acini with p63 positive basal cells was substantially thicker and more uniform than that in ducts or acini without p63 positive basal cells, and also, a vast majority of the focal disruptions occurred near basal cells that lack p63 expression. These findings suggest that focal disruptions in the basal cell layer and alterations in the basement membrane are correlated events and that the physical and functional status of the basal cells could significantly impact the physical integrity of the overlying basement membrane. As the degradation of both the basal cell layer and the basement membrane is a pre-requisite for prostate tumor invasion or progression, ducts or acini with focally disrupted basal cell layer and basement membrane are likely at greater risk to develop invasive lesions. Thus, further elucidation of the specific molecules and mechanism associated with these events may lead to the development of a more effective alternative for repeat biopsy to monitor tumor progression and invasion.

The alpha/beta carboxy-terminal domains of p63 are required for skin and limb development. New insights from the Brdm2 mouse which is not a complete p63 knockout but expresses p63 gamma-like proteins

p63, an ancestral transcription factor of the p53 family, has three C-terminal isoforms whose relative in vivo functions are elusive. The p63 gene is essential for skin and limb development, as vividly shown by two independent global knockout mouse models. Both strains, although constructed differently, have identical and severe phenotypes, characterized by absent epidermis and hindlimbs and only rudimentary forelimbs at birth. Here we show that mice from one model, Brdm2, express normal levels of truncated p63 proteins that contain the DNA binding and oligomerization domain but lack the long carboxy-terminal SAM (sterile alpha-motif) and post-SAM domains that are specific for the alpha and beta isoforms. As such, transcriptionally active p63 proteins from Brdm2 mice resemble the naturally occurring p63gamma isoforms, which of all the p63 isoforms most closely resemble p53. Thus, Brdm2 mice are p63alpha/beta isoform-specific knockout mice, gaining unexpected new importance. Our studies identify that p63alpha/beta but not p63gamma are absolutely required for proper skin and limb development.

Oct4A is expressed by a subpopulation of prostate neuroendocrine cells

BACKGROUND

Cancer stem cells are defined by their self-renewal and multi-potential capabilities and are hypothesized to be the source of primary and recurrent cancers. The stem cell properties of self-renewal and pluripotency in embryonic stem cells and germ cells are regulated by Oct4A, a splice variant of the POU5F1 (Oct3/4) gene, while the function of the alternative splice variant, Oct4B, is unknown. Rare cells that express Oct4 were identified in several somatic cancers, however, the differential contributions of the Oct4A and Oct4B variants were not determined.

METHODS

Oct4A expression and co-localization with lineage markers was performed with PCR and immunohistochemistry.

RESULTS

Rare Oct4A expressing cells are present in human benign and malignant prostate glands and the number of Oct4A expressing cells increases in prostate cancers with high Gleason scores. Oct4A expressing cells were non-proliferative, and did not co-express markers of basal epithelial cell or luminal epithelial cell differentiation, or AMACR, a marker of prostate cancer epithelial cells. A subpopulation of the Oct4A expressing cells co-expressed Sox2, an embryonic stem cell marker, but did not express other putative stem cell markers, such as ABCG2, NANOG or CD133. The majority of Oct4A expressing cells co-expressed chromogranin A, and a subset of Oct4A expressing cells co-expressed synaptophysin, both markers of neuroendocrine differentiation.

CONCLUSION

The increased number of cells that expressed Oct4A in prostate cancer compared to benign prostate, and in cancers of increasing grade, suggests that Oct4A/Chromogranin A co-expressing cells represent neuroendocrine cells in prostate cancer.

K-ras and Wnt signaling synergize to accelerate prostate tumorigenesis in the mouse

Aberrant Ras and Wnt signaling are emerging as key events in the multistep nature of prostate tumorigenesis and progression. Here, we report the generation of a compound model of prostate cancer to define the synergism of activated K-ras (K-ras(+/V12)) and dominant stabilized beta-catenin (Catnb(+/lox(ex3))) in the murine prostate. Recombination of floxed alleles and subsequent expression of oncogenic transgenes was mediated by Cre recombinase expression governed by the composite Probasin (PB) promoter (termed PBCre). Concomitant with elevated mitogen-activated protein kinase (MAPK) signaling, PBCre(+)K-ras(+/V12) mice developed AH at 100 days (100% incidence) and low-grade prostate intraepithelial neoplasia and adenocarcinoma (60% and 7% incidence) by 500 days. PBCre(+)Catnb(+/lox(ex3)) mice showed reduced longevity (average 428 days) and were predisposed to PIN-like keratinized squamous metaplasia at 100 days (100% incidence) and adenocarcinoma (100% incidence) at end-point. These lesions displayed elevated Wnt signaling and basal levels of MAPK signaling. Synchronous activation of K-ras and beta-catenin significantly reduced survival (average 189 days), reflecting accelerated tumorigenesis and the development of invasive carcinoma that displayed activated Wnt and MAPK signaling. Notably, expression of the basal cell marker p63 negatively correlated with tumor grade, resembling human prostate adenocarcinoma. Taken together, our data show that combinatorial oncogenic mutations of K-ras and beta-catenin drive rapid progression of prostate tumorigenesis to invasive carcinoma, characterized by the synergistic elevation of androgen receptor, cyclooxygenase-2, and c-Myc.

The path toward identifying prostatic stem cells

The concept that stem cells reside in prostate epithelia is well accepted and has led to significant efforts aimed at isolating and characterizing adult prostate stem/progenitor cells from both human and rodent prostate tissues. Understanding how prostatic stem and/or progenitor cells give rise to prostate epithelia during development and maintain homeostasis of the prostate gland in adulthood is a major research focus. Furthermore, the ability to identify and manipulate prostatic stem cells (PSCs) holds enormous promise for the development of new approaches to manage and treat prostate cancer. This review maps the pathways to identifying, isolating, characterizing, and understanding the differentiation capacity of PSCs.

Prostate cancer stem cells

Despite the discovery over 60 years ago by Huggins and Hodges that prostate cancers respond to androgen deprivation therapy, hormone-refractory prostate cancer remains a major clinical challenge. There is now mounting evidence that solid tumours originate from undifferentiated stem cell-like cells coexisting within a heterogeneous tumour mass that drive tumour formation, maintain tumour homeostasis and initiate metastases. This review focuses upon current evidence for prostate cancer stem cells, addressing the identification and properties of both normal and transformed prostate stem cells.