Increased Notch signalling inhibits anoikis and stimulates proliferation of prostate luminal epithelial cells

Targeting anoikis resistance as a strategy for cancer therapy

Anoikis, known as matrix detachment-induced apoptosis or detachment-induced cell death, is crucial for tissue development and homeostasis. Cancer cells develop means to evade anoikis, e.g. anoikis resistance, thereby allowing for cells to survive under anchorage-independent conditions. Uncovering the mechanisms of anoikis resistance will provide details about cancer metastasis, and potential strategies against cancer cell dissemination and metastasis. Here, we summarize the principal elements and core molecular mechanisms of anoikis and anoikis resistance. We discuss the latest progress of how anoikis and anoikis resistance are regulated in cancers. Furthermore, we summarize emerging data on selective compounds and nanomedicines, explaining how inhibiting anoikis resistance can serve as a meaningful treatment modality against cancers. Finally, we discuss the key limitations of this therapeutic paradigm and possible strategies to overcome them. In this review, we suggest that pharmacological modulation of anoikis and anoikis resistance by bioactive compounds could surmount anoikis resistance, highlighting a promising therapeutic regimen that could be used to overcome anoikis resistance in cancers.

Identification and validation of a novel anoikis-related prognostic model for prostate cancer

BACKGROUND

Anoikis resistance is a hallmark characteristic of oncogenic transformation, which is crucial for tumor progression and metastasis. The aim of this study was to identify and validate a novel anoikis-related prognostic model for prostate cancer (PCa).

METHODS

We collected a gene expression profile, single nucleotide polymorphism mutation and copy number variation (CNV) data of 495 PCa patients from the TCGA database and 140 PCa samples from the MSKCC dataset. We extracted 434 anoikis-related genes and unsupervised consensus cluster analysis was used to identify molecular subtypes. The immune infiltration, molecular function, and genome alteration of subtypes were evaluated. A risk signature was developed using Cox regression analysis and validated with the MSKCC dataset. We also identify potential drugs for high-risk group patients.

RESULTS

Two subtypes were identified. C1 exhibited a higher level of CNV amplification, immune score, stromal score, aneuploidy score, homologous recombination deficiency, intratumor heterogeneity, single-nucleotide variant neoantigens, and tumor mutational burden compared to C2. C2 showed a better survival outcome and had a high level of gamma delta T cell and activated B cell infiltration. The risk signature consisting of four genes (HELLS, ZWINT, ABCC5, and TPSB2) was developed (area under the curve = 0.780) and was found to be an independent prognostic factor for overall survival in PCa patients. Four CTRP-derived and four PRISM-derived compounds were identified for high-risk patients.

CONCLUSIONS

The anoikis-related prognostic model developed in this study could be a useful tool for clinical decision-making. This study may provide a new perspective for the treatment of anoikis-related PCa.

Drivers of cancer metastasis - Arise early and remain present

Cancer and its metastases arise from mutations of genes, drivers that promote a tumor's growth. Analyses of driver events provide insights into cancer cell history and may lead to a better understanding of oncogenesis. We reviewed 27 metastatic research studies, including pan-cancer studies, individual cancer studies, and phylogenetic analyses, and summarized our current knowledge of metastatic drivers. All of the analyzed studies had a high level of consistency of driver mutations between primary tumors and metastasis, indicating that most drivers appear early in cancer progression and are maintained in metastatic cells. Additionally, we reviewed data from around 50,000 metastatic cancer patients and compiled a list of genes altered in metastatic lesions. We performed Gene Ontology analysis and confirmed that the most significantly enriched processes in metastatic lesions were the epigenetic regulation of gene expression, signal transduction, cell cycle, programmed cell death, DNA damage, hypoxia and EMT. In this review, we explore the most recent discoveries regarding genetic factors in the advancement of cancer, specifically those that drive metastasis.

Anoikis-related signature identifies tumor microenvironment landscape and predicts prognosis and drug sensitivity in colorectal cancer

Background: Anoikis, a mechanism of programmed apoptosis, plays an important role in growth and metastasis of tumors. However, there are still few available comprehensive reports on the impact of anoikis on colorectal cancer. Method: A clustering analysis was done on 133 anoikis-related genes in GSE39582, and we compared clinical features between clusters, the tumor microenvironment was analyzed with algorithms such as "Cibersort" and "ssGSEA". We investigated risk scores of clinical feature groups and anoikis-associated gene mutations after creating a predictive model. We incorporated clinical traits to build a nomogram. Additionally, the quantitative real-time PCR was employed to investigate the mRNA expression of selected anoikis-associated genes. Result: We identified two anoikis-related clusters with distinct prognoses, clinical characteristics, and biological functions. One of the clusters was associated with anoikis resistance, which activated multiple pathways encouraging tumor metastasis. In our prognostic model, oxaliplatin may be a sensitive drug for low-risk patients. The nomogram showed good ability to predict survival time. And SIRT3, PIK3CA, ITGA3, DAPK1, and CASP3 increased in CRC group through the PCR assay. Conclusion: Our study identified two distinct modes of anoikis in colorectal cancer, with active metastasis-promoting pathways inducing an anti-anoikis subtype, which has a stronger propensity for metastasis and a worse prognosis than an anoikis-activated subtype. Massive immune cell infiltration may be an indicator of anoikis resistance. Anoikis' role in the colorectal cancer remains to be investigated.

Prognostic analyses of genes associated with anoikis in breast cancer

Breast cancer (BRCA) is the most diagnosed cancer worldwide and is responsible for the highest cancer-associated mortality among women. It is evident that anoikis resistance contributes to tumour cell metastasis, and this is the primary cause of treatment failure for BRCA. However, anoikis-related gene (ARG) expression profiles and their prognostic value in BRCA remain unclear. In this study, a prognostic model of ARGs based on The Cancer Genome Atlas (TCGA) database was established using a least absolute shrinkage and selection operator analysis to evaluate the prognostic value of ARGs in BRCA. The risk factor graph demonstrated that the low-risk group had longer survival than the high-risk group, implying that the prognostic model had a good performance. We identified 11 ARGs that exhibited differential expression between the two risk groups in TCGA and Gene Expression Omnibus databases. Through Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analyses, we revealed that the screened ARGs were associated with tumour progression and metastasis. In addition, a protein-protein interaction network showed potential interactions among these ARGs. Furthermore, gene set enrichment analysis suggested that the Notch and Wnt signalling pathways were overexpressed in the high-risk group, and gene set variation analysis revealed that 38 hallmark genes differed between the two groups. Moreover, Kaplan-Meier survival curves and receiver operating characteristic curves were used to identify five ARGs (CD24, KRT15, MIA, NDRG1, TP63), and quantitative polymerase chain reaction was employed to assess the differential expression of these ARGs. Univariate and multivariate Cox regression analyses were then performed for the key ARGs, with the best prediction of 3 year survival. In conclusion, ARGs might play a crucial role in tumour progression and serve as indicators of prognosis in BRCA.

Identification and verification of a novel anoikis-related gene signature with prognostic significance in clear cell renal cell carcinoma

PURPOSE

Clear cell renal cell carcinomas (ccRCCs) are the most common form of renal cancer in the world. The loss of extracellular matrix (ECM) stimulates cell apoptosis, known as anoikis. A resistance to anoikis in cancer cells is believed to contribute to tumor malignancy, particularly metastasis; however, the potential influence of anoikis on the prognosis of ccRCC patients is not fully understood.

METHODS

In this study, anoikis-related genes (ARGs) with discrepant expression were selected from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The anoikis-related gene signature (ARS) was built using a combination of the univariate Cox and least absolute shrinkage and selection operator (LASSO) analyses. ARS was also evaluated for their prognostic value. We explored the tumor microenvironment and enrichment pathways between different clusters of ccRCC. We also examined differences in clinical characteristics, immune cell infiltration and drug sensitivity between the high- and low-risk sets. In addition, we utilized three external databases and quantitative real-time polymerase chain reaction (qRT-PCR) to validate the expression and prognosis of ARGs.

RESULTS

Eight ARGs (PLAUR, HMCN1, CDKN2A, BID, GLI2, PLG, PRKCQ and IRF6) were identified as anoikis-related prognostic factors. According to Kaplan-Meier (KM) analysis, ccRCC patients with high-risk ARGs have a worse prognosis. The risk score was found to be a significant independent prognostic indicator. According to tumor microenvironment (TME) scores, stromal score, immune score, and estimated score of the high-risk group were superior to those of the low-risk group. There were significant differences between the two groups regarding the amount of infiltrated immune cells, immune checkpoint expression as well as drug sensitivity. A nomogram was constructed using ccRCC clinical features and risk scores. The signature and the nomogram both performed well in predicting overall survival (OS) for ccRCC patients. According to a decision curve analysis (DCA), clinical treatment options for patients with ccRCC could be improved using this model.

CONCLUSION

The results of validation from external databases and qRT-PCR were basically agreement with findings in TCGA and GEO databases. The ARS serving as biomarkers may provide an important reference for individual therapy of ccRCC patients.

Obesity and prostate cancer - microenvironmental roles of adipose tissue

Obesity is known to have important roles in driving prostate cancer aggressiveness and increased mortality. Multiple mechanisms have been postulated for these clinical observations, including effects of diet and lifestyle, systemic changes in energy balance and hormonal regulation and activation of signalling by growth factors and cytokines and other components of the immune system. Over the past decade, research on obesity has shifted towards investigating the role of peri-prostatic white adipose tissue as an important source of locally produced factors that stimulate prostate cancer progression. Cells that comprise white adipose tissue, the adipocytes and their progenitor adipose stromal cells (ASCs), which proliferate to accommodate white adipose tissue expansion in obesity, have been identified as important drivers of obesity-associated cancer progression. Accumulating evidence suggests that adipocytes are a source of lipids that are used by adjacent prostate cancer cells. However, results of preclinical studies indicate that ASCs promote tumour growth by remodelling extracellular matrix and supporting neovascularization, contributing to the recruitment of immunosuppressive cells, and inducing epithelial-mesenchymal transition through paracrine signalling. Because epithelial-mesenchymal transition is associated with cancer chemotherapy resistance and metastasis, ASCs are considered to be potential targets of therapies that could be developed to suppress cancer aggressiveness in patients with obesity.

YAP is required for prostate development, regeneration, and prostate stem cell function

Prostate development and regeneration depend on prostate stem cell function, the delicate balance of stem cell self-renewal and differentiation. However, mechanisms modulating prostate stem cell function remain poorly identified. Here, we explored the roles of Yes-associated protein 1 (YAP) in prostate stem cells, prostate development and regeneration. Using YAPfl/fl, CD133-CreER mice, we found that stem cell-specific YAP-deficient mice had compromised branching morphogenesis and epithelial differentiation, resulting in damaged prostate development. YAP inhibition also significantly affected the regeneration process of mice prostate, leading to impaired regenerated prostate. Furthermore, YAP ablation in prostate stem cells significantly reduced its self-renewal activity in vitro, and attenuated prostate regeneration of prostate grafts in vivo. Further analysis revealed a decrease in Notch and Hedgehog pathways expression in YAP inhibition cells, and treatment with exogenous Shh partially restored the self-renewal ability of prostate sphere cells. Taken together, our results revealed the roles of YAP in prostate stem cell function and prostate development and regeneration through regulation of the Notch and Hedgehog signaling pathways.

The roles of proteases in prostate cancer

Since the proposition of the pro-invasive activity of proteolytic enzymes over 70 years ago, several roles for proteases in cancer progression have been established. About half of the 473 active human proteases are expressed in the prostate and many of the most well-characterized members of this enzyme family are regulated by androgens, hormones essential for development of prostate cancer. Most notably, several kallikrein-related peptidases, including KLK3 (prostate-specific antigen, PSA), the most well-known prostate cancer marker, and type II transmembrane serine proteases, such as TMPRSS2 and matriptase, have been extensively studied and found to promote prostate cancer progression. Recent findings also suggest a critical role for proteases in the development of advanced and aggressive castration-resistant prostate cancer (CRPC). Perhaps the most intriguing evidence for this role comes from studies showing that the protease-activated transmembrane proteins, Notch and CDCP1, are associated with the development of CRPC. Here, we review the roles of proteases in prostate cancer, with a special focus on their regulation by androgens.

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

Cancer stem cell in prostate cancer progression, metastasis and therapy resistance

Prostate cancer (PCa) is the most diagnosed malignancy in the men worldwide. Cancer stem cells (CSCs) are the sub-population of cells present in the tumor which possess unique properties of self-renewal and multilineage differentiation thus thought to be major cause of therapy resistance, disease relapse, and mortality in several malignancies including PCa. CSCs have also been shown positive for the common stem cells markers such as ALDH EZH2, OCT4, SOX2, c-MYC, Nanog etc. Therefore, isolation and characterization of CSCs specific markers which may discriminate CSCs and normal stem cells are critical to selectively eliminate CSCs. Rapid advances in the field offers a theoretical explanation for many of the enduring uncertainties encompassing the etiology and an optimism for the identification of new stem-cell targets, development of reliable and efficient therapies in the future. The emerging reports have also provided unprecedented insights into CSCs plasticity, quiescence, renewal, and therapeutic response. In this review, we discuss the identification of PCa stem cells, their unique properties, stemness-driving pathways, new diagnostics, and therapeutic interventions.

View from the Biological Property: Insight into the Functional Diversity and Complexity of the Gut Mucus

Due to mucin's important protective effect on epithelial tissue, it has garnered extensive attention. The role played by mucus in the digestive tract is undeniable. On the one hand, mucus forms "biofilm" structures that insulate harmful substances from direct contact with epithelial cells. On the other hand, a variety of immune molecules in mucus play a crucial role in the immune regulation of the digestive tract. Due to the enormous number of microorganisms in the gut, the biological properties of mucus and its protective actions are more complicated. Numerous pieces of research have hinted that the aberrant expression of intestinal mucus is closely related to impaired intestinal function. Therefore, this purposeful review aims to provide the highlights of the biological characteristics and functional categorization of mucus synthesis and secretion. In addition, we highlight a variety of the regulatory factors for mucus. Most importantly, we also summarize some of the changes and possible molecular mechanisms of mucus during certain disease processes. All these are beneficial to clinical practice, diagnosis, and treatment and can provide some potential theoretical bases. Admittedly, there are still some deficiencies or contradictory results in the current research on mucus, but none of this diminishes the importance of mucus in protective impacts.

Anoikis in phenotypic reprogramming of the prostate tumor microenvironment

Prostate cancer is one of the most common malignancies in males wherein 1 in 8 men are diagnosed with this disease in their lifetime. The urgency to find novel therapeutic interventions is associated with high treatment resistance and mortality rates associated with castration-resistant prostate cancer. Anoikis is an apoptotic phenomenon for normal epithelial or endothelial cells that have lost their attachment to the extracellular matrix (ECM). Tumor cells that lose their connection to the ECM can die via apoptosis or survive via anoikis resistance and thus escaping to distant organs for metastatic progression. This review discusses the recent advances made in our understanding of the signaling effectors of anoikis in prostate cancer and the approaches to translate these mechanistic insights into therapeutic benefits for reducing lethal disease outcomes (by overcoming anoikis resistance). The prostate tumor microenvironment is a highly dynamic landscape wherein the balance between androgen signaling, cell lineage changes, epithelial-mesenchymal transition (EMT), extracellular matrix interactions, actin cytoskeleton remodeling as well as metabolic changes, confer anoikis resistance and metastatic spread. Thus, these mechanisms also offer unique molecular treatment signatures, exploitation of which can prime prostate tumors to anoikis induction with a high translational significance.

Single-cell RNA-Seq identifies factors necessary for the regenerative phenotype of prostate luminal epithelial progenitors

Benign prostate hyperplasia and prostate cancer are common diseases that involve the overgrowth of prostatic tissue. Although their pathologies and symptoms differ, both diseases show aberrant activation of prostate progenitor cell phenotypes in a tissue that should be relatively quiescent. This phenomenon prompts a need to better define the normal prostate progenitor cell phenotype and pursue the discovery of causal networks that could yield druggable targets to combat hyperplastic prostate diseases. We used single-cell (sc) RNA-Seq analysis to confirm the identity of a luminal progenitor cell population in both the hormonally intact and castrated mouse prostate. Using marker genes from our scRNA-Seq analysis, we identified factors necessary for the regeneration phenotype of prostate organoids derived from mice and humans in vitro. These data outline potential factors necessary for prostate regeneration and utilization of scRNA-Seq approaches for the identification of pharmacologic strategies targeting critical cell populations that drive prostate disease.

Reevaluating the relationship between EGL-43 (EVI1) and LIN-12 (Notch) during C. elegans anchor cell invasion

Development of the Caenorhabditis elegans reproductive tract is orchestrated by the anchor cell (AC). This occurs in part through a cell invasion event that connects the uterine and vulval tissues. Several key transcription factors regulate AC invasion, such as EGL-43, HLH-2, and NHR-67. Specifically, these transcription factors function together to maintain the post-mitotic state of the AC, a requirement for AC invasion. Recently, a mechanistic connection has been made between loss of EGL-43 and AC cell-cycle entry. The current model states that EGL-43 represses LIN-12 (Notch) expression to prevent AC proliferation, suggesting that Notch signaling has mitogenic effects in the invasive AC. To reexamine the relationship between EGL-43 and LIN-12, we first designed and implemented a heterologous co-expression system called AIDHB that combines the auxin-inducible degron (AID) system of plants with a live cell-cycle sensor based on human DNA helicase B (DHB). After validating AIDHB using AID-tagged GFP, we sought to test it by using AID-tagged alleles of egl-43 and lin-12. Auxin-induced degradation of either EGL-43 or LIN-12 resulted in the expected AC phenotypes. Lastly, we seized the opportunity to pair AIDHB with RNAi to co-deplete LIN-12 and EGL-43, respectively, which revealed that LIN-12 is not required for AC proliferation following loss of EGL-43.

Critical Review on Physiological and Molecular Features during Bovine Mammary Gland Development: Recent Advances

The mammary gland is a unique organ with the ability to undergo repeated cyclic changes throughout the life of mammals. Among domesticated livestock species, ruminants (cattle and buffalo) constitute a distinct class of livestock species that are known milk producers. Cattle and buffalo contribute to 51 and 13% of the total milk supply in the world, respectively. They also play an essential role in the development of the economy for farming communities by providing milk, meat, and draft power. The development of the ruminant mammary gland is highly dynamic and multiphase in nature. There are six developmental stages: embryonic, prepubertal, pubertal, pregnancy, lactation, and involution. There has been substantial advancement in our understanding of the development of the mammary gland in both mouse and human models. Until now, there has not been a thorough investigation into the molecular processes that underlie the various stages of cow udder development. The current review sheds light on the morphological and molecular changes that occur during various developmental phases in diverse species, with a particular focus on the cow udder. It aims to explain the physiological differences between cattle and non-ruminant mammalian species such as humans, mice, and monkeys. Understanding the developmental biology of the mammary gland in molecular detail, as well as species-specific variations, will facilitate the researchers working in this area in further studies on cellular proliferation, differentiation, apoptosis, organogenesis, and carcinogenesis. Additionally, in-depth knowledge of the mammary gland will promote its use as a model organ for research work and promote enhanced milk yield in livestock animals without affecting their health and welfare.

Targeting aldehyde dehydrogenase for prostate cancer therapies

Prostate cancer (PCa) is the most common cancer in men in the United States. About 10 – 20% of PCa progress to castration-resistant PCa (CRPC), which is accompanied by metastasis and therapeutic resistance. Aldehyde dehydrogenase (ALDH) is famous as a marker of cancer stem-like cells in different cancer types, including PCa. Generally, ALDHs catalyze aldehyde oxidation into less toxic carboxylic acids and give cancers a survival advantage by reducing oxidative stress caused by aldehyde accumulation. In PCa, the expression of ALDHs is associated with a higher tumor stage and more lymph node metastasis. Functionally, increased ALDH activity makes PCa cells gain more capabilities in self-renewal and metastasis and reduces the sensitivity to castration and radiotherapy. Therefore, it is promising to target ALDH or ALDH^high cells to eradicate PCa. However, challenges remain in moving the ALDH inhibitors to PCa therapy, potentially due to the toxicity of pan-ALDH inhibitors, the redundancy of ALDH isoforms, and the lack of explicit understanding of the metabolic signaling transduction details. For targeting PCa stem-like cells (PCSCs), different regulators have been revealed in ALDH^high cells to control cell proliferation and tumorigenicity. ALDH rewires essential signaling transduction in PCa cells. It has been shown that ALDHs produce retinoic acid (RA), bind with androgen, and modulate diverse signaling. This review summarizes and discusses the pathways directly modulated by ALDHs, the crucial regulators that control the activities of ALDH^high PCSCs, and the recent progress of ALDH targeted therapies in PCa. These efforts will provide insight into improving ALDH-targeted treatment.

Machine learning assisted analysis of breast cancer gene expression profiles reveals novel potential prognostic biomarkers for triple-negative breast cancer

Tumor heterogeneity and the unclear metastasis mechanisms are the leading cause for the unavailability of effective targeted therapy for Triple-negative breast cancer (TNBC), a breast cancer (BrCa) subtype characterized by high mortality and high frequency of distant metastasis cases. The identification of prognostic biomarker can improve prognosis and personalized treatment regimes. Herein, we collected gene expression datasets representing TNBC and Non-TNBC BrCa. From the complete dataset, a subset reflecting solely known cancer driver genes was also constructed. Recursive Feature Elimination (RFE) was employed to identify top 20, 25, 30, 35, 40, 45, and 50 gene signatures that differentiate TNBC from the other BrCa subtypes. Five machine learning algorithms were employed on these selected features and on the basis of model performance evaluation, it was found that for the complete and driver dataset, XGBoost performs the best for a subset of 25 and 20 genes, respectively. Out of these 45 genes from the two datasets, 34 genes were found to be differentially regulated. The Kaplan-Meier (KM) analysis for Distant Metastasis Free Survival (DMFS) of these 34 differentially regulated genes revealed four genes, out of which two are novel that could be potential prognostic genes (POU2AF1 and S100B). Finally, interactome and pathway enrichment analyses were carried out to investigate the functional role of the identified potential prognostic genes in TNBC. These genes are associated with MAPK, PI3-AkT, Wnt, TGF-β, and other signal transduction pathways, pivotal in metastasis cascade. These gene signatures can provide novel molecular-level insights into metastasis.

Metastasis Model to Test the Role of Notch Signaling in Prostate Cancer

Distant metastasis is the main cause of death in prostate cancer patients. Notch signaling plays an important role in driving prostate cancer aggressiveness and metastasis. In this chapter, we describe a protocol to measure prostate cancer metastatic colonization, incidences of metastasis, accurately quantify the burden of metastasis, and test the role of NOTCH1 receptor on prostate cancer metastatic colonization and homing to distant sites. The metastasis model presented here is established by intracardiac injection of control human prostate cancer cells and NOTCH1 downregulated cells. The cells are engineered to express both red fluorescent protein (RFP) and luciferase. In this model, whole body bioluminescence imaging, high-resolution, and quantitative fluorescence imaging are utilized for quantitative assessment of metastatic colonization and metastasis burden. Further, histopathology analyses of diverse metastatic organs are performed. This model is a powerful and versatile tool to investigate the mechanisms underlying the function of NOTCH receptors in metastatic colonization in prostate cancer.

The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

The ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ‘‘tumor debulking’’ rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting ‘natural agents’ that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

In Silico Logical Modelling to Uncover Cooperative Interactions in Cancer

The multistep development of cancer involves the cooperation between multiple molecular lesions, as well as complex interactions between cancer cells and the surrounding tumour microenvironment. The search for these synergistic interactions using experimental models made tremendous contributions to our understanding of oncogenesis. Yet, these approaches remain labour-intensive and challenging. To tackle such a hurdle, an integrative, multidisciplinary effort is required. In this article, we highlight the use of logical computational models, combined with experimental validations, as an effective approach to identify cooperative mechanisms and therapeutic strategies in the context of cancer biology. In silico models overcome limitations of reductionist approaches by capturing tumour complexity and by generating powerful testable hypotheses. We review representative examples of logical models reported in the literature and their validation. We then provide further analyses of our logical model of Epithelium to Mesenchymal Transition (EMT), searching for additional cooperative interactions involving inputs from the tumour microenvironment and gain of function mutations in NOTCH.

Systematic Evaluation for the Influences of the SOX17/Notch Receptor Family Members on Reversing Enzalutamide Resistance in Castration-Resistant Prostate Cancer Cells

The treatment of castration-resistant prostate cancer (CRPC) remains challenging due to the failure of androgen deprivation therapy (ADT); hence the search for other molecular therapeutic targets besides androgen receptor signaling is ongoing. This study systematically investigated the expression of SOX17 and Notch receptors in CRPC tissues and cells in vitro, showing that consistent clinical CRPC, SOX17/Notch1, and Notch4 were responsible for enzalutamide resistance in CRPC cells. The γ secretase inhibitors, BMS-708163, GSI-IX, PF-3084014, and RO4929097 abrogated the enzalutamide resistance by inhibiting Notch1 or/and Notch4 in vitro, with GSI-IX and RO4929097 being more effective than BMS-708163 and PF-3084014 in reliving bone metastasis in vivo. In conclusion, the Notch1 and Notch4 inhibitors GSI-IX and RO4929097 are promising therapeutic agents for the treatment of CRPC.

Molecular tracing of prostate cancer lethality

Prostate cancer is diagnosed mostly in men over the age of 50 years, and has favorable 5-year survival rates due to early cancer detection and availability of curative surgical management. However, progression to metastasis and emergence of therapeutic resistance are responsible for the majority of prostate cancer mortalities. Recent advancement in sequencing technologies and computational capabilities have improved the ability to organize and analyze large data, thus enabling the identification of novel biomarkers for survival, metastatic progression and patient prognosis. Large-scale sequencing studies have also uncovered genetic and epigenetic signatures associated with prostate cancer molecular subtypes, supporting the development of personalized targeted-therapies. However, the current state of mainstream prostate cancer management does not take full advantage of the personalized diagnostic and treatment modalities available. This review focuses on interrogating biomarkers of prostate cancer progression, including gene signatures that correspond to the acquisition of tumor lethality and those of predictive and prognostic value in progression to advanced disease, and suggest how we can use our knowledge of biomarkers and molecular subtypes to improve patient treatment and survival outcomes.

Activity-Based Screening Assay for Mono-ADP-Ribosylhydrolases

ADP-ribosylation is a post-translational modification involved in the regulation of many vital cellular processes. This posttranslational modification is carried out by ADP-ribosyltransferases converting β-NAD⁺ into nicotinamide and a protein-linked ADP-ribosyl group or a chain of PAR. The reverse reaction, release of ADP-ribose from the acceptor molecule, is catalyzed by ADP-ribosylhydrolases. Several hydrolases contain a macrodomain fold, and activities of human macrodomain protein modules vary from reading or erasing mono- and poly-ADP-ribosylation. Macrodomains have been linked to diseases such as cancer, making them potential drug targets. Discovery of inhibitors requires robust biochemical tools mostly lacking for hydrolases, and here we describe an inhibitor screening assay against mono-ADP-ribosylhydrolyzing enzymes. The activity-based assay uses an α-NAD⁺, anomer of β-NAD⁺, which is accepted as a substrate by MacroD1, MacroD2, and ARH3 due to its resemblance to the protein-linked ADP-ribose. The amount of α-NAD⁺ present after hydrolysis is measured by chemically converting it on a microtiter plate to a fluorescent compound. We optimized the assay for MacroD2 and performed a proof-of-concept compound screening. Three compounds were identified as screening hits with micromolar potency. However, further characterization of the compounds identified them as protein destabilizers, excluding further follow-up studies. Validation and screening demonstrated the usability of the in vitro assay for MacroD2, and we also demonstrate the applicability of the assay as a tool for other human ADP-ribosylhydrolases.

FOXP3 promotes colorectal carcinoma liver metastases by evaluating MMP9 expression via regulating S-adenosylmethionine metabolism

Background

Growing evidence has proved that Forkhead box protein 3 (FOXP3), which is a master regulatory gene in the development and function of regulatory T-cells, is expressed in human cancer cells. This expression indicates the crucial role FOXP3 takes up as the disease progresses. However, its role in colorectal cancer (CRC) liver metastasis is still mostly unknown. This study set out to explore the molecular characteristics of FOXP3 in driving the liver metastasis within CRC.

Methods

We downloaded the RNA-seq data from the GSE50760. Weighted gene co-expression network analysis (WGCNA)WGCNA and RNA-Seq analysis were applied to find the key gene network associated with colorectal cancer liver metastasis. Then we performed pathway enrichment analysis on liver metastasis-associated gene set. Immunohistochemistry, in vitro and in vivo studies were conducted to test expression and function of FOXP3 in CRC tissues and liver metastasis tissues. Non-targeted metabolomics analysis was performed to identify the alteration of FOXP3 expression in metabolites of colorectal cancer liver metastasis. Western blot was performed to confirm changes of matrix metalloproteinase 9MMP9 expression were downstream events of S-adenosyl-methionine (SAM).

Results

We found that FOXP3 and MMP9 exhibited co-expression relationships and affected liver metastasis in CRC. Upregulation of FOXP3 promotes cell migration and invasion in CRC, which suggests a pro-cancer effect. Moreover, metabolomics analysis showed that knockdown of FOXP3 significantly reduced SAM levels, and changes of MMP9 expression were downstream events of SAM, which is concentration-dependent. Besides, The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Western blot analysis confirmed that overexpression of FOXP3 activates the Wnt pathway to promote colon cancer metastasis.

Conclusions

Our results altogether suggested that FOXP3 expression inhibited the SAM cycle to reduce SAMe levels, resulting in altered MMP9 expression and helped CRC liver metastasis.

Klf5 acetylation regulates luminal differentiation of basal progenitors in prostate development and regeneration

Prostate development depends on balanced cell proliferation and differentiation, and acetylated KLF5 is known to alter epithelial proliferation. It remains elusive whether post-translational modifications of transcription factors can differentially determine adult stem/progenitor cell fate. Here we report that, in human and mouse prostates, Klf5 is expressed in both basal and luminal cells, with basal cells preferentially expressing acetylated Klf5. Functionally, Klf5 is indispensable for maintaining basal progenitors, their luminal differentiation, and the proliferation of their basal and luminal progenies. Acetylated Klf5 is also essential for basal progenitors' maintenance and proper luminal differentiation, as deacetylation of Klf5 causes excess basal-to-luminal differentiation; attenuates androgen-mediated organoid organization; and retards postnatal prostate development. In basal progenitor-derived luminal cells, Klf5 deacetylation increases their proliferation and attenuates their survival and regeneration following castration and subsequent androgen restoration. Mechanistically, Klf5 deacetylation activates Notch signaling. Klf5 and its acetylation thus contribute to postnatal prostate development and regeneration by controlling basal progenitor cell fate.

Effects of 4% paraformaldehyde and modified Davidson's fluid on the morphology and immunohistochemistry of Xiang pig testes

Modified Davidson’s fluid (mDF) is a good fixative for morphological and antigen preservation. However, recent studies have shown that 4% paraformaldehyde (PFA) can better preserve the actin structure in rodent testes. It remains controversial which of these fixatives is best for testicular tissue. This study investigated the effects of both mDF and 4% PFA on the morphology and antigen preservation of Xiang pig testes using hematoxylin-eosin (HE) staining and immunohistochemistry (IHC). The stronger testis penetration of mDF compared with that of 4% PFA was primarily manifested as testicular color change and decrease in tissue weight loss. Testes fixed with 4% PFA displayed a severe shrinkage of both the tubular and interstitial compartments and the seminiferous tubule area decreased by 12.02% compared with that in mDF-fixed tissues. In contrast, IHC results showed that 4% PFA fixation achieved better IHC-positive performance than mDF fixation for antigens specifically expressed in germ cells, Leydig cells and Sertoli cells. Due to this improved antigen preservation by 4% PFA fixation, the relative immunoreactions intensity significantly increased by 39.8%, 27.8%, and 76.4%, respectively, compared with that in mDF fixation. In summary, fixation of Xiang pig testes with mDF was suitable for HE staining, while fixation with 4% PFA was more suitable for IHC.

Notch3 promotes prostate cancer-induced bone lesion development via MMP-3

Prostate cancer metastases primarily localize in the bone where they induce a unique osteoblastic response. Elevated Notch activity is associated with high-grade disease and metastasis. To address how Notch affects prostate cancer bone lesions, we manipulated Notch expression in mouse tibia xenografts and monitored tumor growth, lesion phenotype, and the bone microenvironment. Prostate cancer cell lines that induce mixed osteoblastic lesions in bone expressed 5–6 times more Notch3, than tumor cells that produce osteolytic lesions. Expression of active Notch3 (NICD3) in osteolytic tumors reduced osteolytic lesion area and enhanced osteoblastogenesis, while loss of Notch3 in osteoblastic tumors enhanced osteolytic lesion area and decreased osteoblastogensis. This was accompanied by a respective decrease and increase in the number of active osteoclasts and osteoblasts at the tumor-bone interface, without any effect on tumor proliferation. Conditioned medium from NICD3-expressing cells enhanced osteoblast differentiation and proliferation in vitro, while simultaneously inhibiting osteoclastogenesis. MMP-3 was specifically elevated and secreted by NICD3-expressing tumors, and inhibition of MMP-3 rescued the NICD3-induced osteoblastic phenotypes. Clinical osteoblastic bone metastasis samples had higher levels of Notch3 and MMP-3 compared to patient matched visceral metastases or osteolytic metastasis samples. We identified a Notch3-MMP-3 axis in human prostate cancer bone metastases that contributes to osteoblastic lesion formation by blocking osteoclast differentiation, while also contributing to osteoblastogenesis. These studies define a new role for Notch3 in manipulating the tumor microenvironment in bone metastases.

Cellular and Molecular Mechanisms Underlying Prostate Cancer Development: Therapeutic Implications

Prostate cancer is the most frequent nonskin cancer and second most common cause of cancer-related deaths in man. Prostate cancer is a clinically heterogeneous disease with many patients exhibiting an aggressive disease with progression, metastasis, and other patients showing an indolent disease with low tendency to progression. Three stages of development of human prostate tumors have been identified: intraepithelial neoplasia, adenocarcinoma androgen-dependent, and adenocarcinoma androgen-independent or castration-resistant. Advances in molecular technologies have provided a very rapid progress in our understanding of the genomic events responsible for the initial development and progression of prostate cancer. These studies have shown that prostate cancer genome displays a relatively low mutation rate compared with other cancers and few chromosomal loss or gains. The ensemble of these molecular studies has led to suggest the existence of two main molecular groups of prostate cancers: one characterized by the presence of ERG rearrangements (~50% of prostate cancers harbor recurrent gene fusions involving ETS transcription factors, fusing the 5' untranslated region of the androgen-regulated gene TMPRSS2 to nearly the coding sequence of the ETS family transcription factor ERG) and features of chemoplexy (complex gene rearrangements developing from a coordinated and simultaneous molecular event), and a second one characterized by the absence of ERG rearrangements and by the frequent mutations in the E3 ubiquitin ligase adapter SPOP and/or deletion of CDH1, a chromatin remodeling factor, and interchromosomal rearrangements and SPOP mutations are early events during prostate cancer development. During disease progression, genomic and epigenomic abnormalities accrued and converged on prostate cancer pathways, leading to a highly heterogeneous transcriptomic landscape, characterized by a hyperactive androgen receptor signaling axis.

Estrogen receptor α-NOTCH1 axis enhances basal stem-like cells and epithelial-mesenchymal transition phenotypes in prostate cancer

Background

Prostate cancer (PCa) is the second leading cause of mortality and a leading cause of malignant tumors in males. Prostate cancer stem cells (PCSCs) are likely the responsible cell types for cancer initiation, clinical treatment failure, tumor relapse, and metastasis. Estrogen receptor alpha (ERα) is mainly expressed in the basal layer cells of the normal prostate gland and has key roles in coordinating stem cells to control prostate organ development. Here, we investigated the roles of the estrogen-ERα signaling pathway in regulating PCSCs.

Methods

Correlation of CD49f and ERα/NOTCH1 was analyzed in human clinical datasets and tissue samples. Flow cytometry was used to sort CD49f^Hi and CD49f^Low cells. EZH2 recruitment by ERα and facilitation of ERα binding to the NOTCH1 promoter was validated by Co-IP and ChIP. Primary tumor growth, tumor metastasis and sensitivity to 17β-estradiol (E2) inhibitor (tamoxifen) were evaluated in castrated mice.

Results

ERα expression was significantly higher in CD49f^Hi prostate cancer basal stem-like cells (PCBSLCs), which showed basal and EMT features with susceptibility to E2 treatment. ERα-induced estrogen effects were suggested to drive the NOTCH1 signaling pathway activity via binding to the NOTCH1 promoter. Moreover, EZH2 was recruited by ERα and acted as a cofactor to assist ERα-induced estrogen effects in regulating NOTCH1 in PCa. In vivo, E2 promoted tumor formation and metastasis, which were inhibited by tamoxifen.

Conclusions

Our results implicated CD49f+/ERα + prostate cancer cells associated with basal stem-like and EMT features, named EMT-PCBSLCs, in heightened potential for promoting metastasis. NOTCH1 was regulated by E2 in CD49f^Hi EMT-PCBSLCs. These results contribute to insights into the metastatic mechanisms of EMT-PCBSLCs in PCa.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0367-x) contains supplementary material, which is available to authorized users.

Transcriptional Reprogramming and Novel Therapeutic Approaches for Targeting Prostate Cancer Stem Cells

Prostate cancer is the most common malignancy in men and the second cause of cancer-related deaths in western countries. Despite the progress in the treatment of localized prostate cancer, there is still lack of effective therapies for the advanced forms of the disease. Most patients with advanced prostate cancer become resistant to androgen deprivation therapy (ADT), which remains the main therapeutic option in this setting, and progress to lethal metastatic castration-resistant prostate cancer (mCRPC). Current therapies for prostate cancer preferentially target proliferating, partially differentiated, and AR-dependent cancer cells that constitute the bulk of the tumor mass. However, the subpopulation of tumor-initiating or tumor-propagating stem-like cancer cells is virtually resistant to the standard treatments causing tumor relapse at the primary or metastatic sites. Understanding the pathways controlling the establishment, expansion and maintenance of the cancer stem cell (CSC) subpopulation is an important step toward the development of more effective treatment for prostate cancer, which might enable ablation or exhaustion of CSCs and prevent treatment resistance and disease recurrence. In this review, we focus on the impact of transcriptional regulators on phenotypic reprogramming of prostate CSCs and provide examples supporting the possibility of inhibiting maintenance and expansion of the CSC pool in human prostate cancer along with the currently available methodological approaches. Transcription factors are key elements for instructing specific transcriptional programs and inducing CSC-associated phenotypic changes implicated in disease progression and treatment resistance. Recent studies have shown that interfering with these processes causes exhaustion of CSCs with loss of self-renewal and tumorigenic capability in prostate cancer models. Targeting key transcriptional regulators in prostate CSCs is a valid therapeutic strategy waiting to be tested in clinical trials.

A pivotal role of androgen signaling in Notch-responsive cells in prostate development, maturation, and regeneration

Androgen signaling is essential for prostate development, morphogenesis, and regeneration. Emerging evidence also indicates a regulatory role of Notch signaling in prostate development, differentiation, and growth. However, the collaborative regulatory mechanisms of androgen and Notch signaling during prostate development, growth, and regeneration are largely unknown. Hairy and Enhancer of Split 1 (Hes1) is a transcriptional regulator of Notch signaling pathways, and its expression is responsive to Notch signaling. Hes1-expressing cells have been shown to possess the regenerative capability to repopulate a variety of adult tissues. In this study, we developed new mouse models to directly assess the role of the androgen receptor in prostatic Hes1-expressing cells. Selective deletion of AR expression in embryonic Hes1-expressing cells impeded early prostate development both in vivo and in tissue xenograft experiments. Prepubescent deletion of AR expression in Hes1-expressing cells resulted in prostate glands containing abnormalities in cell morphology and gland architecture. A population of castration-resistant Hes1-expressing cells was revealed in the adult prostate, with the ability to repopulate prostate epithelium following androgen supplementation. Deletion of AR in Hes1-expressing cells diminishes their regenerative ability. These lines of evidence demonstrate a critical role for the AR in Notch-responsive cells during the course of prostate development, morphogenesis, and regeneration, and implicate a mechanism underlying interaction between the androgen and Notch signaling pathways in the mouse prostate.

Sox2 Expression Marks Castration-Resistant Progenitor Cells in the Adult Murine Prostate

Identification of defined epithelial cell populations with progenitor properties is critical for understanding prostatic development and disease. Here, we demonstrate that Sox2 expression is enriched in the epithelial cells of the proximal prostate adjacent to the urethra. We use lineage tracing of Sox2-positive cells during prostatic development, homeostasis, and regeneration to show that the Sox2 lineage is capable of self-renewal and contributes to prostatic regeneration. Persisting luminal cells express Sox2 after castration, highlighting a potential role for Sox2 in cell survival and castration-resistance. In addition to revealing a novel progenitor population in the prostate, these data implicate Sox2 as a regulatory factor of adult prostate epithelial stem cells. Stem Cells 2019;37:690-700.

Cells of Origin for Prostate Cancer

Comprehensive knowledge of the normal prostate epithelial lineage hierarchy is a prerequisite to investigate the identity of the cells of origin for prostate cancer. The basal and luminal cells constitute most of the prostate epithelium and have been the major focuses of the study on the cells of origin for prostate cancer. Much progress has been made during the past few decades, mainly using mouse models, to understand the inter-lineage relationship and intra-lineage heterogeneity in adults as well as the lineage plasticity during conditions of stress. These studies have concluded that the adult mouse prostate basal and luminal cells are largely independently sustained under physiological conditions, but both types of cells possess the capacity for bipotent differentiation under stress or artificial experimental conditions. However, the existence or the identity of the putative progenitors within each lineage warrants further investigation. Whether the human prostate lineage hierarchy is completely the same as that of the mouse remains uncertain. Experiments from independent groups have demonstrated that both types of cells in mice and humans can serve as targets for transformation. But controversies remain whether the disease from distinct cells of origin display different clinical behaviors. Further investigation of the intra-lineage heterogeneity will provide new insights into this issue. Understanding the identity of the cells of origin for prostate cancer will help identify novel prognostic markers for early detection of aggressive prostate cancers, provide insights into the therapeutic vulnerability of these tumors, and inspire novel therapeutic strategies.

Single-Cell Analysis Identifies LY6D as a Marker Linking Castration-Resistant Prostate Luminal Cells to Prostate Progenitors and Cancer

The exact identity of castrate-resistant (CR) cells and their relation to CR prostate cancer (CRPC) is unresolved. We use single-cell gene profiling to analyze the molecular heterogeneity in basal and luminal compartments. Within the luminal compartment, we identify a subset of cells intrinsically resistant to castration with a bi-lineage gene expression pattern. We discover LY6D as a marker of CR prostate progenitors with multipotent differentiation and enriched organoid-forming capacity. Lineage tracing further reveals that LY6D+ CR luminal cells can produce LY6D- luminal cells. In contrast, in luminal cells lacking PTEN, LY6D+ cells predominantly give rise to LY6D+ tumor cells, contributing to high-grade PIN lesions. Gene expression analyses in patients' biopsies indicate that LY6D expression correlates with early disease progression, including progression to CRPC. Our studies thus identify a subpopulation of luminal progenitors characterized by LY6D expression and intrinsic castration resistance. LY6D may serve as a prognostic maker for advanced prostate cancer.

Prostate Luminal Progenitor Cells in Development and Cancer

Prostate cancer (PCa) has a predominantly luminal phenotype. Basal cells were previously identified as a cell of origin for PCa, but increasing evidence implicates luminal cells as a preferred cell of origin for PCa, as well as key drivers of tumor development and progression. Prostate luminal cells are understudied compared with basal cells. In this review, we describe the contribution of prostate luminal progenitor (LP) cells to luminal cell development and their role in prostate development, androgen-mediated regeneration of castrated prostate, and tumorigenesis. We also discuss the potential value of LP transcriptomics to identify new targets and therapies to treat aggressive PCa. Finally, we propose future research directions focusing on molecular mechanisms underlying LP cell biology and heterogeneity in normal and diseased prostate.

SPDEF is overexpressed in gastric cancer and triggers cell proliferation by forming a positive regulation loop with FoxM1

The SAM-pointed domain-containing ETS transcription factor (SPDEF) is an epithelial-specific transcription factor of the E26 transformation-specific (ETS) family, which binds the target gene through the high-affinity sequence of GGAT. It is suggested that SPDEF targets the promoter activity of Forkhead Box M1 (FoxM1), which has been proven to be highly expressed in gastric cancer. We found that SPDEF was overexpressed both at the messenger RNA (mRNA) and at the protein level in human gastric cancer species. The gastric cancer cells transfected with the SPDEF expression plasmid or SPDEF small interfering RNA (siRNA) led to observations on the clone genetics assay that indicated the promotion or the inhibition of gastric cancer cell proliferation, respectively. Both mRNA and protein levels of FoxM1 were regulated by SPDEF in gastric cancer cells and FoxM1 was also overexpressed in the corresponding human gastric cancer species. The overexpression and inhibition of FoxM1 could upregulate and downregulate the mRNA and protein levels of SPDEF expression, respectively. The recovery experiments verified that the overexpression of FoxM1 could at least partially revert both the expression of SPDEF and the proliferation of the cell lines even with the siRNA inhibition of SPDEF. The result of the dual luciferase activity assay showed that SPDEF bound to the promoter of FoxM1 and activated it. FoxM1 might also bind to the promoter of SPDEF to affect its expression. The results were checked in vivo. In conclusion, SPDEF is overexpressed in gastric cancer, which can form a positive regulation loop with FoxM1 to promote gastric carcinogenesis.

Preclinical Models of Prostate Cancer: Patient-Derived Xenografts, Organoids, and Other Explant Models

Prostate cancer remains a lethal disease. Preclinical cancer models that accurately represent the tumors of the patients they are intended to help are necessary to test potential therapeutic approaches and to better translate research discoveries. However, research in the prostate cancer field is hampered by the limited number of human cell lines and xenograft models, most of which do not recapitulate the human disease seen in the clinic today. This work reviews the recent advances in human patient-derived xenograft, organoid, and other explant models to address this need. In contrast to other tumor streams, the prostate cancer field is challenged by this approach, yet despite the limitations, patient-derived models remain an integral component of the preclinical testing pathway leading to better treatments for men with prostate cancer.

HepaCAM inhibits the malignant behavior of castration-resistant prostate cancer cells by downregulating Notch signaling and PF-3084014 (a γ-secretase inhibitor) partly reverses the resistance of refractory prostate cancer to docetaxel and enzalutamide in vitro

Castration-resistant prostate cancer (CRPC) continues to be a major challenge in the treatment of prostate cancer (PCa). The expression of hepatocyte cell adhesion molecule (HepaCAM), a novel tumor suppressor, is frequently downregulated or lost in PCa. Overactivated Notch signaling is involved in the development and progression of PCa, including CRPC. In this study, we found that the activities of Notch signaling were elevated, while HepaCAM expression was decreased in CRPC tissues compared with matched primary prostate cancer (PPC) tissues. In addition, HepaCAM negativity was found to be associated with a worse progression-free survival (PFS). Furthermore, the overexpression of HepaCAM induced by transfection with a HepaCAM overexpression vector (Ad-HepaCAM) exerted antitumor effects by decreasing the proliferation, and suppressing the invasion and migration of bicalutamide-resistant (Bica-R) cells and enzalutamide-resistant (Enza-R) cells. Importantly, we found that the antitumor effects of HepaCAM on the resistant cells were associated with the downregulation of Notch signaling. Moreover, we revealed that PF-3084014 (a γ-secretase inhibitor) re-sensitized Enza-R cells to enzalutamide, and sequential dual-resistant (E+D-R) cells to docetaxel. Additionally, the findings of this study demonstrated that the use of PF-3084014 alone exerted potent antitumor effect on the resistant cells in vitro. On the whole, this study indicates that HepaCAM potentially represents a therapeutic target and PF-3084014 may prove to a promising agent for use in the treatment of refractory PCa.

Cancer Stem Cells (CSCs) in Drug Resistance and their Therapeutic Implications in Cancer Treatment

Cancer stem cells (CSCs), also known as tumor-initiating cells (TICs), are suggested to be responsible for drug resistance and cancer relapse due in part to their ability to self-renew themselves and differentiate into heterogeneous lineages of cancer cells. Thus, it is important to understand the characteristics and mechanisms by which CSCs display resistance to therapeutic agents. In this review, we highlight the key features and mechanisms that regulate CSC function in drug resistance as well as recent breakthroughs of therapeutic approaches for targeting CSCs. This promises new insights of CSCs in drug resistance and provides better therapeutic rationales to accompany novel anticancer therapeutics.

Histone 2B-GFP Label-Retaining Prostate Luminal Cells Possess Progenitor Cell Properties and Are Intrinsically Resistant to Castration

The existence of slow-cycling luminal cells in the prostate has been suggested, but their identity and functional properties remain unknown. Using a bigenic mouse model to earmark, isolate, and characterize the quiescent stem-like cells, we identify a label-retaining cell (LRC) population in the luminal cell layer as luminal progenitors. Molecular and biological characterizations show that these luminal LRCs are significantly enriched in the mouse proximal prostate, exhibit relative dormancy, display bipotency in both in vitro and in vivo assays, and express a stem/progenitor gene signature with resemblance to aggressive prostate cancer. Importantly, these LRCs, compared with bulk luminal cells, maintain a lower level of androgen receptor (AR) expression and are less androgen dependent and also castration resistant in vivo. Finally, analysis of phenotypic markers reveals heterogeneity within the luminal progenitor cell pool. Our study establishes luminal LRCs as progenitors that may serve as a cellular origin for castration-resistant prostate cancer.

•

A bigenic mouse model to study prostatic slow-cycling luminal epithelial cells

•

Prostate label-retaining cells (LRCs) exhibit stem/progenitor cell activities

•

Luminal LRCs are developmentally bipotent and display a progenitor gene signature

•

Luminal LRCs resist castration and molecularly resemble aggressive prostate cancer

SOX2 boosts major tumor progression genes in prostate cancer and is a functional biomarker of lymph node metastasis

Critical issues in prostate cancer (PC) are a. identification of molecular drivers of the highly aggressive neuroendocrine differentiation (NED) in adenocarcinoma, and b. early assessment of disease progression.

The SRY (sex determining region Y)-box 2 gene, SOX2, is an essential embryonic stem cell gene involved in prostate tumorigenesis. Here we assessed its implications in NED and progression of PC and its diagnostic and prognostic value.

Laser microdissection, qRT-PCR, quantitative Methylation-Specific PCR and immunohistochemistry were used to analyze SOX2 gene expression and regulation in 206 PC samples. Results were examined according to the patient's clinical pathological profile and follow-ups. Functional studies were performed using PC cells transfected to overexpress or silence SOX2.

SOX2 was consistently downregulated in PC, except in cell clusters lying within lymph node (LN)-positive PC. Multivariate analysis revealed that SOX2 mRNA expression in the primary tumor was significantly associated with LN metastasis. When SOX2 mRNA levels were ≥1.00, relative to (XpressRef) Universal Total RNA, adjusted Odds Ratio was 24.4 (95% CI: 7.54–79.0), sensitivity 0.81 (95% CI: 0.61–0.93) and specificity 0.87 (95% CI: 0.81–0.91). Patients experiencing biochemical recurrence had high median levels of SOX2 mRNA.

In both PC and LN metastasis, SOX2 and NED marker, Chromogranin-A, were primarily co-expressed. In PC cells, NED genes were upregulated by SOX2 overexpression and downregulated by its silencing, which also abolished SNAI2/Slug dependent NED. Moreover, SOX2 upregulated neural CAMs, neurotrophins/neurotrophin receptors, pluripotency and epithelial-mesenchymal transition transcription factors, growth, angiogenic and lymphangiogenic factors, and promoted PC cell invasiveness and motility.

This study discloses novel SOX2 target genes driving NED and spread of PC and proposes SOX2 as a functional biomarker of LN metastasization for PC.

Multipotent Basal Stem Cells, Maintained in Localized Proximal Niches, Support Directed Long-Ranging Epithelial Flows in Human Prostates

Sporadic mitochondrial DNA mutations serve as clonal marks providing access to the identity and lineage potential of stem cells within human tissues. By combining quantitative clonal mapping with 3D reconstruction of adult human prostates, we show that multipotent basal stem cells, confined to discrete niches in juxta-urethral ducts, generate bipotent basal progenitors in directed epithelial migration streams. Basal progenitors are then dispersed throughout the entire glandular network, dividing and differentiating to replenish the loss of apoptotic luminal cells. Rare lineage-restricted luminal stem cells, and their progeny, are confined to proximal ducts and provide only minor contribution to epithelial homeostasis. In situ cell capture from clonal maps identified delta homolog 1 (DLK1) enrichment of basal stem cells, which was validated in functional spheroid assays. This study establishes significant insights into niche organization and function of prostate stem and progenitor cells, with implications for disease.

Pro-invasive properties of Snail1 are regulated by sumoylation in response to TGFβ stimulation in cancer

Transforming growth factor β (TGFβ) is a key regulator of epithelial-to-mesenchymal transition (EMT) during embryogenesis and in tumors. The effect of TGFβ, on ΕΜΤ, is conveyed by induction of the pro-invasive transcription factor Snail1. In this study, we report that TGFβ stimulates Snail1 sumoylation in aggressive prostate, breast and lung cancer cells. Sumoylation of Snail1 lysine residue 234 confers its transcriptional activity, inducing the expression of classical EMT genes, as well as TGFβ receptor I (TβRI) and the transcriptional repressor Hes1. Mutation of Snail1 lysine residue 234 to arginine (K234R) abolished sumoylation of Snail1, as well as its migratory and invasive properties in human prostate cancer cells. An increased immunohistochemical expression of Snail1, Sumo1, TβRI, Hes1, and c-Jun was observed in aggressive prostate cancer tissues, consistent with their functional roles in tumorigenesis.

Human prostate luminal cell differentiation requires NOTCH3 induction by p38-MAPK and MYC

Many pathways dysregulated in prostate cancer are also involved in epithelial differentiation. To better understand prostate tumor initiation, we sought to investigate specific genes and mechanisms required for normal basal to luminal cell differentiation. Utilizing human prostate basal epithelial cells and an in vitro differentiation model, we tested the hypothesis that regulation of NOTCH3 by the p38 MAPK family (hereafter p38-MAPK), via MYC, is required for luminal differentiation. Inhibition (SB202190 and BIRB796) or knockdown of p38α (also known as MAPK14) and/or p38δ (also known as MAPK13) prevented proper differentiation. Additionally, treatment with a γ-secretase inhibitor (RO4929097) or knockdown of NOTCH1 and/or NOTCH3 greatly impaired differentiation and caused luminal cell death. Constitutive p38-MAPK activation through MKK6(CA) increased NOTCH3 (but not NOTCH1) mRNA and protein levels, which was diminished upon MYC inhibition (10058-F4 and JQ1) or knockdown. Furthermore, we validated two NOTCH3 enhancer elements through a combination of enhancer (e)RNA detection (BruUV-seq) and luciferase reporter assays. Finally, we found that the NOTCH3 mRNA half-life increased during differentiation or upon acute p38-MAPK activation. These results reveal a new connection between p38-MAPK, MYC and NOTCH signaling, demonstrate two mechanisms of NOTCH3 regulation and provide evidence for NOTCH3 involvement in prostate luminal cell differentiation.

Activation of Notch pathway is linked with epithelial-mesenchymal transition in prostate cancer cells

Notch signaling has been reported to play an essential role in tumorigenesis. Several studies have suggested that Notch receptors could be oncoproteins or tumor suppressors in different types of human cancers. Emerging evidence has suggested that Notch pathway regulates cell growth, apoptosis, cell cycle, and metastasis. In the current study, we explore whether Notch-1 could regulate the cell invasion and migration as well as EMT (epithelial-mesenchymal transition) in prostate cancer cells. We found that overexpression of Notch-1 enhanced cell migration and invasion in PC-3 cells. However, downregulation of Notch-1 retarded cell migration and invasion in prostate cancer cells. Importantly, we observed that overexpression of Notch-1 led to EMT in PC-3 cells. Notably, we found that EMT-type cells are associated with EMT markers change and cancer stem cell phenotype. Taken together, we concluded that downregulation of Notch-1 could be a promising approach for inhibition of invasion in prostate cancer cells, which could be useful for the treatment of metastatic prostate cancer.

Developmental pathways associated with cancer metastasis: Notch, Wnt, and Hedgehog

Master developmental pathways, such as Notch, Wnt, and Hedgehog, are signaling systems that control proliferation, cell death, motility, migration, and stemness. These systems are not only commonly activated in many solid tumors, where they drive or contribute to cancer initiation, but also in primary and metastatic tumor development. The reactivation of developmental pathways in cancer stroma favors the development of cancer stem cells and allows their maintenance, indicating these signaling pathways as particularly attractive targets for efficient anticancer therapies, especially in advanced primary tumors and metastatic cancers. Metastasis is the worst feature of cancer development. This feature results from a cascade of events emerging from the hijacking of epithelial-mesenchymal transition, angiogenesis, migration, and invasion by transforming cells and is associated with poor survival, drug resistance, and tumor relapse. In the present review, we summarize and discuss experimental data suggesting pivotal roles for developmental pathways in cancer development and metastasis, considering the therapeutic potential. Emerging targeted antimetastatic therapies based on Notch, Wnt, and Hedgehog pathways are also discussed.

Activation of Notch1 synergizes with multiple pathways in promoting castration-resistant prostate cancer

Metastatic castration-resistant prostate cancer (CRPC) is the primary cause of prostate cancer-specific mortality. Defining new mechanisms that can predict recurrence and drive lethal CRPC is critical. Here, we demonstrate that localized high-risk prostate cancer and metastatic CRPC, but not benign prostate tissues or low/intermediate-risk prostate cancer, express high levels of nuclear Notch homolog 1, translocation-associated (Notch1) receptor intracellular domain. Chronic activation of Notch1 synergizes with multiple oncogenic pathways altered in early disease to promote the development of prostate adenocarcinoma. These tumors display features of epithelial-to-mesenchymal transition, a cellular state associated with increased tumor aggressiveness. Consistent with its activation in clinical CRPC, tumors driven by Notch1 intracellular domain in combination with multiple pathways altered in prostate cancer are metastatic and resistant to androgen deprivation. Our study provides functional evidence that the Notch1 signaling axis synergizes with alternative pathways in promoting metastatic CRPC and may represent a new therapeutic target for advanced prostate cancer.

Context dependent regulatory patterns of the androgen receptor and androgen receptor target genes

BACKGROUND

Expression of the androgen receptor (AR) is associated with androgen-dependent proliferation arrest and terminal differentiation of normal prostate epithelial cells. Additionally, activation of the AR is required for survival of benign luminal epithelial cells and primary cancer cells, thus androgen deprivation therapy (ADT) leads to apoptosis in both benign and cancerous tissue. Escape from ADT is known as castration-resistant prostate cancer (CRPC). In the course of CRPC development the AR typically switches from being a cell-intrinsic inhibitor of normal prostate epithelial cell proliferation to becoming an oncogene that is critical for prostate cancer cell proliferation. A clearer understanding of the context dependent activation of the AR and its target genes is therefore desirable.

METHODS

Immortalized human prostate basal epithelial EP156T cells and progeny cells that underwent epithelial to mesenchymal transition (EMT), primary prostate epithelial cells (PrECs) and prostate cancer cell lines LNCaP, VCaP and 22Rv1 were used to examine context dependent restriction and activation of the AR and classical target genes, such as KLK3. Genome-wide gene expression analyses and single cell protein analyses were applied to study the effect of different contexts.

RESULTS

A variety of growth conditions were tested and found unable to activate AR expression and transcription of classical androgen-dependent AR target genes, such as KLK3, in prostate epithelial cells with basal cell features or in mesenchymal type prostate cells. The restriction of androgen- and AR-dependent transcription of classical target genes in prostate basal epithelial cells was at the level of AR expression. Exogenous AR expression was sufficient for androgen-dependent transcription of AR target genes in prostate basal epithelial cells, but did not exert a positive feedback on endogenous AR expression. Treatment of basal prostate epithelial cells with inhibitors of epigenetic gene silencing was not efficient in inducing androgen-dependent transcription of AR target genes, suggesting the importance of missing cofactor(s).

CONCLUSIONS

Regulatory mechanisms of AR and androgen-dependent AR target gene transcription are insufficiently understood and may be critical for prostate cancer initiation, progression and escape from standard therapy. The present model is useful for the study of context dependent activation of the AR and its transcriptome.