Activation of Wnt/β-catenin signaling in a subpopulation of murine prostate luminal epithelial cells induces high grade prostate intraepithelial neoplasia

Diverse landscape of genetically engineered mouse models: Genomic and molecular insights into prostate cancer

Prostate cancer (PCa) is a significant health concern for men worldwide and is particularly prevalent in the United States. It is a complex disease presenting different molecular subtypes and varying degrees of aggressiveness. Transgenic/genetically engineered mouse models (GEMMs) greatly enhanced our understanding of the intricate molecular processes that underlie PCa progression and have offered valuable insights into potential therapeutic targets for this disease. The integration of whole-exome and whole-genome sequencing, along with expression profiling, has played a pivotal role in advancing GEMMs by facilitating the identification of genetic alterations driving PCa development. This review focuses on genetically modified mice classified into the first and second generations of PCa models. We summarize whether models created by manipulating the function of specific genes replicate the consequences of genomic alterations observed in human PCa, including early and later disease stages. We discuss cases where GEMMs did not fully exhibit the expected human PCa phenotypes and possible causes of the failure. Here, we summarize the comprehensive understanding, recent advances, strengths and limitations of the GEMMs in advancing our insights into PCa, offering genetic and molecular perspectives for developing novel GEMM models.

Paracrine Wnt signaling is necessary for prostate epithelial proliferation

INTRODUCTION

The Wnt proteins play key roles in the development, homeostasis, and disease progression of many organs including the prostate. However, the spatiotemporal expression patterns of Wnt proteins in prostate cell lineages at different developmental stages and in prostate cancer remain inadequately characterized.

METHODS

We isolated the epithelial and stromal cells in the developing and mature mouse prostate by flow cytometry and determined the expression levels of Wnt ligands. We used Visium spatial gene expression analysis to determine the spatial distribution of Wnt ligands in the mouse prostatic glands. Using laser-capture microscopy in combination with gene expression analysis, we also determined the expression patterns of Wnt signaling components in stromal and cancer cells in advanced human prostate cancer specimens. To investigate how the stroma-derived Wnt ligands affect prostate development and homeostasis, we used a Col1a2-CreERT2 mouse model to disrupt the Wnt transporter Wntless specifically in prostate stromal cells.

RESULTS

We showed that the prostate stromal cells are a major source of several Wnt ligands. Visium spatial gene expression analysis revealed a distinct spatial distribution of Wnt ligands in the prostatic glands. We also showed that Wnt signaling components are highly expressed in the stromal compartment of primary and advanced human prostate cancer. Blocking stromal Wnt secretion attenuated prostate epithelial proliferation and regeneration but did not affect cell survival and lineage maintenance.

DISCUSSION

Our study demonstrates a critical role of stroma-derived Wnt ligands in prostate development and homeostasis.

Exploring the Wnt Pathway as a Therapeutic Target for Prostate Cancer

Aberrant activation of the Wnt pathway is emerging as a frequent event during prostate cancer that can facilitate tumor formation, progression, and therapeutic resistance. Recent discoveries indicate that targeting the Wnt pathway to treat prostate cancer may be efficacious. However, the functional consequence of activating the Wnt pathway during the different stages of prostate cancer progression remains unclear. Preclinical work investigating the efficacy of targeting Wnt signaling for the treatment of prostate cancer, both in primary and metastatic lesions, and improving our molecular understanding of treatment responses is crucial to identifying effective treatment strategies and biomarkers that help guide treatment decisions and improve patient care. In this review, we outline the type of genetic alterations that lead to activated Wnt signaling in prostate cancer, highlight the range of laboratory models used to study the role of Wnt genetic drivers in prostate cancer, and discuss new mechanistic insights into how the Wnt cascade facilitates prostate cancer growth, metastasis, and drug resistance.

miR-425-5p suppresses tumorigenesis and DDP resistance in human-prostate cancer by targeting GSK3β and inactivating the Wnt/β-catenin signaling pathway

Prostate cancer (PCa) represents the most frequently diagnosed cancer in men. Cisplatin, also known as cis-diamminedichloroplatinum (DDP), is a standard chemotherapeutic agent used to treat PCa, and DDP resistance remains one important obstacle in DDP-based chemotherapy. In our research, we found miR-425-5p was down-regulated in PCa and even lower in DDP-resistant PCa determined by quantitative polymerase chain reaction; in contrast, GSK3β mRNA expression was upregulated in PCa and even higher in DDP-resistant PCa. Moreover, there was a modest but significant inverse correlation between the expression of GSK3β mRNA and miR-425-5p. Functional experiments showed that miR-425-5p mimic inhibited DDP resistance as evidenced by a promoted apoptosis rate (flow cytometry) and suppressed cell viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay) and expressions of MDR1 andMRP1 (western blotting) in DU145/DDP and PC3/DDP cells. Luciferase reporter assay and RNA immunoprecipitation identifiedGSK3β was a potential target of miR-425-5p. The effect ofmiR-425-5pmimic on DDP resistance was partially reversed by pcDNA-GSK3β. Mechanically, miR-425-5p mimic reduced expression of β-catenin, cyclin D1 and C-myc, which was further blocked when GSK3β overexpressed. In vivo experiments, recovery of GSK3β prevented xenograft tumor growth and DDP resistance in the presence of miR-425-5p mimic. To sum up, miR-425-5p upregulation might sensitize human PCa to DDP by targeting GSK3β and inactivating the Wnt/β-catenin signaling pathway.

Interplay Between SOX9, Wnt/β-Catenin and Androgen Receptor Signaling in Castration-Resistant Prostate Cancer

Androgen receptor (AR) signaling plays a key role not only in the initiation of prostate cancer (PCa) but also in its transition to aggressive and invasive castration-resistant prostate cancer (CRPC). However, the crosstalk of AR with other signaling pathways contributes significantly to the emergence and growth of CRPC. Wnt/β-catenin signaling facilitates ductal morphogenesis in fetal prostate and its anomalous expression has been linked with PCa. β-catenin has also been reported to form complex with AR and thus augment AR signaling in PCa. The transcription factor SOX9 has been shown to be the driving force of aggressive and invasive PCa cells and regulate AR expression in PCa cells. Furthermore, SOX9 has also been shown to propel PCa by the reactivation of Wnt/β-catenin signaling. In this review, we discuss the critical role of SOX9/AR/Wnt/β-catenin signaling axis in the development and progression of CRPC. The phytochemicals like sulforaphane and curcumin that can concurrently target SOX9, AR and Wnt/β-catenin signaling pathways in PCa may thus be beneficial in the chemoprevention of PCa.

Genetically Engineered Mouse Models of Prostate Cancer in the Postgenomic Era

Recent genomic sequencing analyses have unveiled the spectrum of genomic alterations that occur in primary and advanced prostate cancer, raising the question of whether the corresponding genes are functionally relevant for prostate tumorigenesis, and whether such functions are associated with particular disease stages. In this review, we describe genetically engineered mouse models (GEMMs) of prostate cancer, focusing on those that model genomic alterations known to occur in human prostate cancer. We consider whether the phenotypes of GEMMs based on gain or loss of function of the relevant genes provide reliable counterparts to study the predicted consequences of the corresponding genomic alterations as occur in human prostate cancer, and we discuss exceptions in which the GEMMs do not fully emulate the expected phenotypes. Last, we highlight future directions for the generation of new GEMMs of prostate cancer and consider how we can use GEMMs most effectively to decipher the biological and molecular mechanisms of disease progression, as well as to tackle clinically relevant questions.

Deregulation of E-cadherin, β-catenin, APC and Caveolin-1 expression occurs in canine prostate cancer and metastatic processes

Prostate cancer is a heterogeneous disease with high levels of clinical and gene heterogeneity, consequently offering several targets for therapy. Dogs with naturally occurring prostate cancer are useful models for molecular investigations and studying new treatment efficacy. Three genes and proteins associated with the WNT pathway (β-catenin, APC and E-cadherin) and Caveolin-1 (CAV-1) were evaluated in canine pre-neoplastic proliferative inflammatory atrophy (PIA), prostate cancer and metastatic disease. The APC gene methylation status was also investigated. As in human prostate cancer, cytoplasmic and nuclear β-catenin, which are fundamental for activating the canonical WNT pathway, were found in canine prostate cancer and metastasis. Membranous E-cadherin was also lost in these lesions, allowing cellular migration to the stroma and nuclear localization of β-catenin. In contrast to human prostate tumours, no APC downregulation or hypermethylation was found in canine prostate cancer. The CAV-1 gene and protein overexpression were found in canine prostate cancer, and as in humans, the highest levels were found in Gleason scores ≥8. In conclusion, as with human prostate cancer, β-catenin and E-cadherin in the WNT pathway, as well as Caveolin-1, are molecular drivers in canine prostate cancer. These findings provide additional evidence that dogs are useful models for studying new therapeutic targets in prostate cancer.

Deletion of tumor suppressors adenomatous polyposis coli and Smad4 in murine luminal epithelial cells causes invasive prostate cancer and loss of androgen receptor expression

Prostate cancer is the most diagnosed non-skin cancer in the US and kills approximately 27,000 men per year in the US. Additional genetic mouse models are needed that recapitulate the heterogeneous nature of human prostate cancer. The Wnt/beta-catenin signaling pathway is important for human prostate tumorigenesis and metastasis, and also drives tumorigenesis in mouse models. Loss of Smad4 has also been found in human prostate cancer and drives tumorigenesis and metastasis when coupled with other genetic aberrations in mouse models. In this work, we concurrently deleted Smad4 and the tumor suppressor and endogenous Wnt/beta-catenin inhibitor adenomatous polyposis coli (Apc) in luminal prostate cells in mice. This double conditional knockout model produced invasive castration-resistant prostate carcinoma with no evidence of metastasis. We observed mixed differentiation phenotypes, including basaloid and squamous differentiation. Interestingly, tumor cells in this model commonly lose androgen receptor expression. In addition, tumors disappear in these mice during androgen cycling (castration followed by testosterone reintroduction). These mice model non-metastatic castration resistant prostate cancer and should provide novel information for tumors that have genetic aberrations in the Wnt pathway or Smad4.

Type II transmembrane serine proteases as potential targets for cancer therapy

Carcinogenesis is accompanied by increased protein and activity levels of extracellular cell-surface proteases that are capable of modifying the tumor microenvironment by directly cleaving the extracellular matrix, as well as activating growth factors and proinflammatory mediators involved in proliferation and invasion of cancer cells, and recruitment of inflammatory cells. These complex processes ultimately potentiate neoplastic progression leading to local tumor cell invasion, entry into the vasculature, and metastasis to distal sites. Several members of the type II transmembrane serine protease (TTSP) family have been shown to play critical roles in cancer progression. In this review the knowledge collected over the past two decades about the molecular mechanisms underlying the pro-cancerous properties of selected TTSPs will be summarized. Furthermore, we will discuss how these insights may facilitate the translation into clinical settings in the future by specifically targeting TTSPs as part of novel cancer treatment regimens.

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.

Murine Prostate Micro-dissection and Surgical Castration

Mouse models are used extensively to study prostate cancer and other diseases. The mouse is an excellent model with which to study the prostate and has been used as a surrogate for discoveries in human prostate development and disease. Prostate micro-dissection allows consistent study of lobe-specific prostate anatomy, histology, and cellular characteristics in the absence of contamination of other tissues. Testosterone affects prostate development and disease. Androgen deprivation therapy is a common treatment for prostate cancer patients, but many prostate tumors become castration-resistant. Surgical castration of mouse models allows for the study of castration resistance and other facets of hormonal biology on the prostate. This procedure can be coupled with testosterone reintroduction, or hormonal regeneration of the prostate, a powerful method to study stem cell lineages in the prostate. Together, prostate micro-dissection and surgical castration opens up a multitude of opportunities for robust and consistent research of prostate development and disease. This manuscript describes the protocols for prostate micro-dissection and surgical castration in the laboratory mouse.

Concurrent Hepsin overexpression and adenomatous polyposis coli deletion causes invasive prostate carcinoma in mice

BACKGROUND

A clinical need to better categorize patients with prostate cancer exists. The Wnt/β-catenin signaling pathway plays important roles in human prostate cancer progression. Deletion of the endogenous Wnt antagonist adenomatous polyposis coli (Apc) in mice causes high grade prostate intraepithelial neoplasia, widely thought to be the precursor to prostate cancer. However, no metastasis occurrs in this model. New mouse models are needed to determine molecular causes of tumorigenesis, progression, and metastasis.

METHODS

To determine whether the overexpression of the prostate oncogene Hepsin could cause prostate cancer progression, we crossed a prostate-specific Hepsin overexpression model to a prostate-specific Apc-deletion model and classified the observed phenotype.

RESULTS

When Apc was deleted and Hepsin overexpressed concurrently, mice displayed invasive carcinoma, with loss of membrane characteristics and increase of fibrosis. These tumors had both luminal and basaloid characteristics. Though no metastasis was observed, there was evidence of adenomas and lung necrosis, inflammation, and chronic hemorrhage.

CONCLUSIONS

This work indicates that the Wnt/β-catenin pathway and the Hepsin pathway act in concert to promote prostate cancer progression. Both of these pathways are up-regulated in human prostate cancer and could represent chemotherapeutic targets.

Frequency of PTEN alterations, TMPRSS2-ERG fusion and their association in prostate cancer

BACKGROUND

Phosphatase and tensin homolog (PTEN) gene aberration and trans membrane protease, serine 2 (TMPRSS2)-v-ets avian erythroblastosis virus E26 oncogene homolog (ERG) fusion are the most prevalent genomic events in prostate cancer. In this study we aimed to evaluate the frequency of PTEN alteration and TMPRSS2-ERG fusion and possible link between these two biomarkers in Iranian men.

METHODS

We assessed 42 fresh frozen tissue samples of prostate cancer (PCA) obtained by radical prostatectomy, interrogating the TMPRSS2-ERG fusion gene along with PTEN gene status using Real Time PCR and FISH methods.

RESULTS

Using Real Time PCR we identified the TMPRSS2-ERG fusion in 64% (27/42) of tumor samples, which was confirmed by FISH technique, giving 21 positive samples with deletion, suggesting the presence of TMPRSS2-ERG fusion gene. By contrast, PTEN deletion was detected in 52% (11/21) of PCA samples, which all showed low expression in Real Time. Concomitance of PTEN deletion or low expression and TMPRSS2-ERG fusion was present in PCA samples (P=0.005). All of the PTEN deletion samples showed TMPRSS2-ERG fusion, (11/11, 100%) while not all of the TMPRSS2-ERG fusion positive samples showed PTEN deletion. None of 29 cases of BPH and 8 cases of normal zone of tumor tissue showed TMPRSS2-ERG fusion.

CONCLUSIONS

These results indicate that PTEN loss occurs in cooperation with TMPRSS2-ERG fusion in PCA. While the majority of PCA samples harbor TMPRSS2-ERG fusion as well as PTEN gene deletion, normal tissues do not show these molecular aberrations.

Drug discovery in prostate cancer mouse models

INTRODUCTION

The mouse is an important, though imperfect, organism with which to model human disease and to discover and test novel drugs in a preclinical setting. Many experimental strategies have been used to discover new biological and molecular targets in the mouse, with the hopes of translating these discoveries into novel drugs to treat prostate cancer in humans. Modeling prostate cancer in the mouse, however, has been challenging, and often drugs that work in mice have failed in human trials.

AREAS COVERED

The authors discuss the similarities and differences between mice and men; the types of mouse models that exist to model prostate cancer; practical questions one must ask when using a mouse as a model; and potential reasons that drugs do not often translate to humans. They also discuss the current value in using mouse models for drug discovery to treat prostate cancer and what needs are still unmet in field.

EXPERT OPINION

With proper planning and following practical guidelines by the researcher, the mouse is a powerful experimental tool. The field lacks genetically engineered metastatic models, and xenograft models do not allow for the study of the immune system during the metastatic process. There remain several important limitations to discovering and testing novel drugs in mice for eventual human use, but these can often be overcome. Overall, mouse modeling is an essential part of prostate cancer research and drug discovery. Emerging technologies and better and ever-increasing forms of communication are moving the field in a hopeful direction.

Mini-review: Does Notch promote or suppress cancer? New findings and old controversies

Notch signaling in tumorigenesis and cancer progression presents a certain enigma. Numerous experimental studies reported significant effects in cancer, yet of varying magnitude and opposite sign. This mini review is aimed to streamline our understanding of the Notch role in tumor progression, and outline future experiments to clarify the modality of Notch function and perspectives of the Notch-based anticancer treatments.