Initiation of prostate cancer in mice by Tp53R270H: evidence for an alternative molecular progression

Regulation of Kinase Signaling Pathways by α6β4-Integrins and Plectin in Prostate Cancer

Hemidesmosomes (HDs) are adhesive structures that ensure stable anchorage of cells to the basement membrane. They are formed by α6β4-integrin heterodimers and linked to intermediate filaments via plectin. It has been reported that one of the most common events during the pathogenesis of prostate cancer (PCa) is the loss of HD organization. While the expression levels of β4-integrins are strongly reduced, the expression levels of α6-integrins and plectin are maintained or even elevated, and seem to promote tumorigenic properties of PCa cells, such as proliferation, invasion, metastasis, apoptosis- and drug-resistance. In this review, we discuss the potential mechanisms of how HD components might contribute to various cellular signaling pathways to promote prostate carcinogenesis. Moreover, we summarize the current knowledge on the involvement of α6β4-integrins and plectin in PCa initiation and progression.

Urine- and Blood-Based Molecular Profiling of Human Prostate Cancer

Objective

Prostate cancer (PCa) is one of the most common malignant tumors, accounting for 20% of total tumors ranked first in males. PCa is usually asymptomatic at the early stage and the specificity of the current biomarkers for the detection of PCa is low. The present study evaluates circulating tumor DNA (ctDNA) in blood or urine, which can be used as biomarkers of PCa and the combination of these markers may increase the sensitivity and specificity of the detection of PCa.

Methods

Tissue, blood, and urine samples were collected from patients with PCa. All prostate tissue specimens underwent pathological examination. A hybrid-capture-based next-generation sequencing assay was used for plasma and urinary ctDNA profiling. Sequencing data were analyzed by an in-house pipeline for mutation calling. Mutational profiles of PCa and BPH were compared in both plasma and urine samples. Associations of detected mutations and clinical characteristics were statistically analyzed.

Results

A significant association of mutation allele frequencies (MAFs) in the blood samples with patients with metastatic PCa rather than patients with primary PCa, and MAFs are changed after treatment in patients with PCa. Further, the number of mutations in urine is not associated with clinical characteristics of PCa patients, but the frequencies of mutation alleles in the urine are associated with patient age. Comparison of cfDNA aberration profiles between urine and blood reveals more alterations in urine than in blood, including TP53, AR, ATM, MYC, and SPOP mutations.

Conclusion

This work provides the potential clinical application of urine, in addition to blood, as a powerful and convenient non-invasive approach in personalized medicine for patients with PCa.

Use of RNA-Seq and a Transgenic Mouse Model to Identify Genes Which May Contribute to Mutant p53-Driven Prostate Cancer Initiation

Simple Summary

We use RNA-seq analysis to identify genes that may contribute to mutant p53-mediated prostate cancer initiation in a genetically engineered mouse model (B6.129S4-Trp53tm3.1Tyj/J). A total of 1378 differentially expressed genes, including wildtype p53 target genes (e.g. Cdkn1a, Bax, Bcl2, Kras, Mdm2), p53 gain-of-function-related genes (Mgmt, Id4), and prostate cancer-related genes (Cav-1, Raf1, Kras), were identified. Mice that were homozygous or heterozygous for the Trp53 R270H mutation developed grade one PIN lesions at 3 months and 5 months, respectively, whereas wildtype mice did not develop PIN. Immunohistochemical analysis revealed decreased levels of irradiation-mediated apoptosis in homozygous and heterozygous mice when compared to wildtype counterparts, and this aligned with observed differences in apoptosis-related gene expression.

Abstract

We previously demonstrated that the Trp53-R270H mutation can drive prostate cancer (CaP) initiation using the FVB.129S4 (Trp53^tm3Tyj/wt); FVB.129S (Nkx3-1^{tm3(cre)Mmswt}) genetically engineered mouse model (GEM). We now validate this finding in a different model (B6.129S4-Trp53^tm3.1Tyj/J mice) and use RNA-sequencing (RNA-Seq) to identify genes which may contribute to Trp53 R270H-mediated prostate carcinogenesis. Wildtype (Trp53^WT/WT), heterozygous (Trp53^R270H/WT), and homozygous mice (Trp53^R270H/R270H) were exposed to 5 Gy irradiation to activate and stabilize p53, and thereby enhance our ability to identify differences in transcriptional activity between the three groups of mice. Mouse prostates were harvested 6 h post-irradiation and processed for histological/immunohistochemistry (IHC) analysis or were snap-frozen for RNA extraction and transcriptome profiling. IHC analyses determined that presence of the Trp53-R270H mutation impacts apoptosis (lower caspase 3 activity) but not cell proliferation (Ki67). RNA-Seq analysis identified 1378 differentially expressed genes, including wildtype p53 target genes (E.g., Cdkn1a, Bax, Bcl2, Kras, Mdm2), p53 gain-of-function (GOF)-related genes (Mgmt, Id4), and CaP-related genes (Cav-1, Raf1, Kras). Further understanding the mechanisms which contribute to prostate carcinogenesis could allow for the development of improved preventive methods, diagnostics, and treatments for CaP.

RASAL2 suppresses the proliferative and invasive ability of PC3 prostate cancer cells

The RAS protein activator like 2 (RASAL2) negatively regulates RAS proto-oncogene which is activated by high mutation rate in cancer. Thus, RASAL2 expression could potentially limit the function of RAS in prostate cancer (PCa). Genome-wide DNA methylation analysis demonstrated that RASAL2 is differentially hypermethylated in PCa tissues compared to benign prostate tissues. The PCR analysis of RASAL2 mRNA transcript showed differential expression in a panel of prostate cell lines with most PCa showing lower RASAL2 expression compared to benign prostatic epithelial cells. In PCa PC3 cells, the ectopic expression of RASAL2 significantly inhibited cell proliferation and invasion and induced an S phase plus G2/M phase cell cycle arrest. Ingenuity Pathway Analysis (IPA) demonstrated a cross talk between RASAL2 and TNFα, a key cytokine in immune signaling pathway that is relevant in PCa. Over-expression of RASAL2 downregulated TNFα expression whereas the knockdown of RASAL2 caused increased expression of TNFα. Taken together, our data demonstrates tumor suppressor role for RASAL2 in human PCa cells, despite increased RAS oncogenic activity. Our observation provides a new mechanistic insight of RASAL2 expression in aberrant Ras expression and immune signaling in PCa cells suggesting a potential novel therapeutic target for PCa.

From genomics to functions: preclinical mouse models for understanding oncogenic pathways in prostate cancer

Next-generation sequencing has revealed numerous genomic alterations that induce aberrant signaling activities in prostate cancer (PCa). Among them are pathways affecting multiple cancer types, including the PI3K/AKT/mTOR, p53, Rb, Ras/Raf/MAPK, Myc, FGF, and Wnt signaling pathways, as well as ones that are prominent in PCa, including alterations in genes of AR signaling, the ETS family, NKX3.1, and SPOP. Cross talk among the oncogenic pathways can confer PCa resistance to therapy, particularly in advanced tumors, which are castration-resistant or show neuroendocrine features. Various experimental models, such as cancer cell lines, animal models, and patient-derived xenografts and organoids have been utilized to dissect PCa progression mechanisms. Here, we review the current preclinical mouse models for studying the most commonly altered pathways in PCa, with an emphasis on their interplays. We highlight the power of genetically engineered mouse models (GEMMs) in translating genomic discoveries into understanding of the functions of these oncogenic events in vivo. Developing and analyzing PCa mouse models will undoubtedly continue to offer new insights into tumor biology and guide novel rationalized therapy.

p53 mutant-type in human prostate cancer cells determines the sensitivity to phenethyl isothiocyanate induced growth inhibition

Background

We reported previously that phenethyl isothiocyanate (PEITC), a dietary compound, can reactivate p53^R175H mutant in vitro and in SK-BR-3 (p53^R175H) breast xenograft model resulting in tumor inhibition. Because of the diversity of human cancers with p53 mutations, these findings raise important questions whether this mechanism operates in different cancer types with same or different p53 mutations. In this study, we investigated whether PEITC recuses mutant p53 in prostate cancer cells harboring different types of p53 mutants, structural and contact, in vitro and in vivo.

Methods

Cell proliferation, cell apoptosis and cell cycle arrest assays were performed to examine the effects of PEITC on prostate cancer cell lines with p53 mutation(s), wild-type p53, p53 null or normal prostate cells in vitro. Western blot analysis was used to monitor the expression levels of p53 protein, activation of ATM and upregulation of canonical p53 targets. Immunoprecipitation, subcellular protein fraction and qRT-PCR was performed to determine change in conformation and restoration of transactivation functions/ inhibition of gain-of-function (GOF) activities to p53 mutant(s). Mice xenograft models were established to evaluate the antitumor efficacy of PEITC and PEITC-induced reactivation of p53 mutant(s) in vivo. Immunohistochemistry of xenograft tumor tissues was performed to determine effects of PEITC on expression of Ki67 and mutant p53 in vivo.

Results

We demonstrated that PEITC inhibits the growth of prostate cancer cells with different “hotspot” p53 mutations (structural and contact), however, preferentially towards structural mutants. PEITC inhibits proliferation and induces apoptosis by rescuing mutant p53 in p53^R248W contact (VCaP) and p53^R175H structural (LAPC-4) mutant cells with differential potency. We further showed that PEITC inhibits the growth of DU145 cells that co-express p53^P223L (structural) and p53^V274F (contact) mutants by targeting p53^P223L mutant selectively, but not p53^V274F. The mutant p53 restored by PEITC induces apoptosis in DU145 cells by activating canonical p53 targets, delaying cells in G1 phase and phosphorylating ATM. Importantly, PEITC reactivated p53^R175H and p53^P223L/V274F mutants in LAPC-4 and DU145 prostate xenograft models, respectively, resulting in significant tumor inhibition.

Conclusion

Our studies provide the first evidence that PEITC’s anti-cancer activity is cancer cell type-independent, but p53 mutant-type dependent.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1267-z) contains supplementary material, which is available to authorized users.

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.

Combined Loss of EAF2 and p53 Induces Prostate Carcinogenesis in Male Mice

Mutations in the p53 tumor suppressor are frequent in patients with castration-resistant prostate cancer but less so in patients with localized disease, and patients who have Li-Fraumeni with germline p53 mutations do not have an increased incidence of prostate cancer, suggesting that additional molecular and/or genetic changes are required for p53 to promote prostate carcinogenesis. ELL-associated factor 2 (EAF2) is a tumor suppressor that is frequently downregulated in advanced prostate cancer. Previous studies have suggested that p53 binds to EAF2, providing a potential mechanism for their functional interactions. In this study, we tested whether p53 and EAF2 could functionally interact in prostate cancer cells and whether concurrent inactivation of p53 and EAF2 could promote prostate carcinogenesis in a murine knockout model. Endogenous p53 coprecipitated with EAF2 in prostate cancer cells, and deletion mutagenesis indicated that this interaction was mediated through the C terminus of EAF2 and the DNA binding domain of p53. Concurrent knockdown of p53 and EAF2 induced an increase in proliferation and migration in cultured prostate cancer cells, and conventional p53 and EAF2 knockout mice developed prostate cancer. In human prostate cancer specimens, concurrent p53 nuclear staining and EAF2 downregulation was associated with high Gleason score. These findings suggest that EAF2 and p53 functionally interact in prostate tumor suppression and that simultaneous inactivation of EAF2 and p53 can drive prostate carcinogenesis.

Suppression of Akt1-β-catenin pathway in advanced prostate cancer promotes TGFβ1-mediated epithelial to mesenchymal transition and metastasis

Akt1 is essential for the oncogenic transformation and tumor growth in various cancers. However, the precise role of Akt1 in advanced cancers is conflicting. Using a neuroendocrine TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model, we first show that the genetic ablation or pharmacological inhibition of Akt1 in mice blunts oncogenic transformation and prostate cancer (PCa) growth. Intriguingly, triciribine (TCBN)-mediated Akt inhibition in 25-week old, tumor-bearing TRAMP mice and Akt1 gene silencing in aggressive PCa cells enhanced epithelial to mesenchymal transition (EMT) and promoted metastasis to the lungs. Mechanistically, Akt1 suppression leads to increased expression of EMT markers such as Snail1 and N-cadherin and decreased expression of epithelial marker E-cadherin in TRAMP prostate, and in PC3 and DU145 cells. Next, we identified that Akt1 knockdown in PCa cells results in increased production of TGFβ1 and its receptor TGFβ RII, associated with a decreased expression of β-catenin. Furthermore, treatment of PCa cells with ICG001 that blocks nuclear translocation of β-catenin promoted EMT and N-cadherin expression. Together, our study demonstrates a novel role of the Akt1-β-catenin-TGFβ1 pathway in advanced PCa.

Roles of TP53 in determining therapeutic sensitivity, growth, cellular senescence, invasion and metastasis

TP53 is a critical tumor suppressor gene that regulates cell cycle progression, apoptosis, cellular senescence and many other properties critical for control of normal cellular growth and death. Due to the pleiotropic effects that TP53 has on gene expression and cellular physiology, mutations at this tumor suppressor gene result in diverse physiological effects. T53 mutations are frequently detected in numerous cancers. The expression of TP53 can be induced by various agents used to treat cancer patients such as chemotherapeutic drugs and ionizing radiation. Radiation will induce Ataxia telangiectasia mutated (ATM) and other kinases that results in the phosphorylation and activation of TP53. TP53 is also negatively regulated by other mechanisms, such as ubiquitination by ligases such as MDM2. While TP53 has been documented to control the expression of many "classical" genes (e.g., p21^Cip-1, PUMA, Bax) by transcriptional mechanisms for quite some time, more recently TP53 has been shown to regulate microRNA (miR) gene expression. Different miRs can promote oncogenesis (oncomiR) whereas others act to inhibit tumor progression (tumor suppressor miRs). Targeted therapies to stabilize TP53 have been developed by various approaches, MDM2/MDM4 inhibitors have been developed to stabilize TP53 in TP53-wild type (WT) tumors. In addition, small molecules have been isolated that will reactivate certain mutant TP53s. Both of these types of inhibitors are in clinical trials. Understanding the actions of TP53 may yield novel approaches to suppress cancer, aging and other health problems.

Novel roles of androgen receptor, epidermal growth factor receptor, TP53, regulatory RNAs, NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, and matrix metalloproteinase-9 in prostate cancer and prostate cancer stem cells

Approximately one in six men will be diagnosed with some form of prostate cancer in their lifetime. Over 250,000 men worldwide die annually due to complications from prostate cancer. While advancements in prostate cancer screening and therapies have helped in lowering this statistic, better tests and more effective therapies are still needed. This review will summarize the novel roles of the androgen receptor (AR), epidermal growth factor receptor (EGFR), the EGFRvIII variant, TP53, long-non-coding RNAs (lncRNAs), microRNAs (miRs), NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, (NGAL), matrix metalloproteinase-9 (MMP-9), the tumor microenvironment and cancer stem cells (CSC) have on the diagnosis, development and treatment of prostate cancer.

ERG Activates the YAP1 Transcriptional Program and Induces the Development of Age-Related Prostate Tumors

The significance of ERG in human prostate cancer is unclear because mouse prostate is resistant to ERG-mediated transformation. We determined that ERG activates the transcriptional program regulated by YAP1 of the Hippo signaling pathway and found that prostate-specific activation of either ERG or YAP1 in mice induces similar transcriptional changes and results in age-related prostate tumors. ERG binds to chromatin regions occupied by TEAD/YAP1 and transactivates Hippo target genes. In addition, in human luminal-type prostate cancer cells, ERG binds to the promoter of YAP1 and is necessary for YAP1 expression. These results provide direct genetic evidence of a causal role for ERG in prostate cancer and reveal a connection between ERG and the Hippo signaling pathway.

Mouse models of prostate cancer: picking the best model for the question

When the National Institutes of Health Mouse Models of Human Cancer Consortium initiated the Prostate Steering Committee 15 years ago, there were no genetically engineered mouse (GEM) models of prostate cancer (PCa). Today, a PubMed search for "prostate cancer mouse model" yields 3,200 publications and this list continues to grow. The first generation of GEM utilized the newly discovered and characterized probasin promoter driving viral oncogenes such as Simian virus 40 large T antigen to yield the LADY and TRAMP models. As the PCa research field has matured, the second generation of models has incorporated the single and multiple molecular changes observed in human disease, such as loss of PTEN and overexpression of Myc. Application of these models has revealed that mice are particularly resistant to developing invasive PCa, and once they achieve invasive disease, the PCa rarely resembles human disease. Nevertheless, these models and their application have provided vital information on human PCa progression. The aim of this review is to provide a brief primer on mouse and human prostate histology and pathology, provide descriptions of mouse models, as well as attempt to answer the age old question: Which GEM model of PCa is the best for my research question?

The omega-3 polyunsaturated fatty acid DHA induces simultaneous apoptosis and autophagy via mitochondrial ROS-mediated Akt-mTOR signaling in prostate cancer cells expressing mutant p53

Docosahexaenoic acid (DHA) induces autophagy-associated apoptotic cell death in wild-type p53 cancer cells via regulation of p53. The present study investigated the effects of DHA on PC3 and DU145 prostate cancer cell lines harboring mutant p53. Results show that, in addition to apoptosis, DHA increased the expression levels of lipidated form LC3B and potently stimulated the autophagic flux, suggesting that DHA induces both autophagy and apoptosis in cancer cells expressing mutant p53. DHA led to the generation of mitochondrial reactive oxygen species (ROS), as shown by the mitochondrial ROS-specific probe mitoSOX. Similarly, pretreatment with the antioxidant N-acetyl-cysteine (NAC) markedly inhibited both the autophagy and the apoptosis triggered by DHA, indicating that mitochondrial ROS mediate the cytotoxicity of DHA in mutant p53 cells. Further, DHA reduced the levels of phospho-Akt and phospho-mTOR in a concentration-dependent manner, while NAC almost completely blocked that effect. Collectively, these findings present a novel mechanism of ROS-regulated apoptosis and autophagy that involves Akt-mTOR signaling in prostate cancer cells with mutant p53 exposed to DHA.

The current and future role of sequence-based analysis in prostate cancer treatment

Prostate cancer is the most commonly diagnosed, nondermatologic malignancy in US men. Localized disease can be managed through active surveillance or curative, locally directed therapies, but 30% of men treated with surgery or radiation will need additional (often systemic) treatment for relapsed disease. While spectacular advances in medical treatment of advanced prostate cancer have improved the quality and duration of patients' lives, metastatic prostate cancer remains an incurable, lethal disease that requires additional therapies and better treatment strategies. The advent of ultra-high-throughput sequencing technology provides an opportunity to comprehensively assess the constellation of genetic and molecular events underlying each patient's tumor, and promises to enhance our ability to deliver specifically tailored personalized treatment to men with prostate cancer. The known biological and clinical heterogeneity of prostate cancer presents both opportunities and challenges to the application and utilization of sequence-based analysis to guide prostate cancer treatment.

Wild-type p53 suppresses the epithelial-mesenchymal transition and stemness in PC-3 prostate cancer cells by modulating miR‑145

The principal problem arising from prostate cancer (PCa) is its propensity to metastasize to bone and the mechanism(s) need to be further elucidated. The tumor suppressor p53 plays an important role in regulating the epithelial-mesenchymal transition (EMT) and cancer cell stemness, which have been proposed to play critical roles in cancer metastasis. MiR-145, a direct target of p53, represses bone metastasis of PCa and is involved in regulating EMT and cancer cell stemness. However, it is unknown whether wild‑type p53 (WT-p53) plays a role in regulating invasion, EMT and cancer cell stemness of PCa cells and whether miR-145 mediates the function of WT-p53. In the present study, we found that ectopic expression of WT-p53 inhibited the migration and invasion, and enhanced the adhesion of p53-null PC-3 cells derived from PCa bone metastasis. Furthermore, WT-p53 suppressed the expression of the mesenchymal markers fibronectin, vimentin, N-cadherin, ZEB2 and upregulated the expression of the epithelial marker E-cadherin in PC-3 cells. Moreover, WT-p53 also suppressed colony formation, tumor sphere formation and expression of CSC markers and stemness factors including CD44, Oct4, c-Myc and Klf4 in PC-3 cells. Importantly, WT-p53 upregulated the expression of miR-145, and the inhibitory effects of WT-p53 on migration, invasion, EMT and stemness of PC-3 cells were reversed by anti-miR-145. Together, our findings demonstrate that WT-p53 suppresses migration, invasion, EMT and stemness in PC-3 cells at least partially through modulating miR-145. These results suggest that loss of WT-p53 may promote the bone metastasis of PCa at least partially through repressing miR-145 to elevate EMT and stemness of cancer cells.

Diagnostic value of DNA alteration: loss of heterozygosity or allelic imbalance-promising for molecular staging of prostate cancers

The biological behavior of prostate cancer is uncertain, and therefore, search for molecular prognostic markers associated with disease progression seems to be essential. We performed microsatellite allelotyping of DNA isolated from primary prostate tumors biopsies (prostate adenocarcinoma, PCa). We evaluated the frequency of allelic imbalance (AI), including loss of heterozygosity and/or microsatellite imbalance (LOH/MSI) as well as the association of these DNA alterations with clinicopathological variables. We assessed the significance of LOH/MSI alterations in selected imprinted and non-imprinted chromosomal regions (IR and NIR) in PCa. A total of 50 biopsies of prostate tumor (containing >75 % tumor cells) were histologically examined confirming prostate carcinoma. Microsatellite allelotyping using 16 microsatellite markers linked to the following chromosomal regions: 1p31.2, 3p21.3–25.3, 7q32.2, 9p21.3, 11p15.5, 12q23.2, and 16q22.1 was performed. The incidence of LOH/MSI alterations in prostate tumor cells was the highest for chromosomal regions 7q32.2 and 16q22.1 (31.25 and 26.60 %, respectively), followed by 1p31.2 and 3p21.3–25.3 (26.50 and 17.40 %, respectively). Statistically significant increase in LOH/MSI alterations has been observed for markers: D1S2137 (1p region; p = 0.00032), D9S974 (9p region; p = 0.0017), and D16S3025 (16q region; p = 0.0017). Statistically significant differences in frequency of LOH/MSI alterations in particular chromosomal regions have been found for 1p31.2, 7q32.2 and 16q22.1 (p = 0.027, p = 0.012 and p = 0.031, respectively). We documented statistically significant association between Fractional Allele Loss (FAL) index and advanced tumor stage (p < 0.05). We suggest that genomic instability of LOH/MSI type is a frequent event in prostate carcinogenesis and assessed as FAL index has clinical value for the molecular staging of prostate cancer in (TRUS)-guided prostate biopsy material.