Identification of a cell of origin for human prostate cancer

Human intermediate prostate cancer stem cells contribute to the initiation and development of prostate adenocarcinoma

BACKGROUND

Intermediate cells are present in the early stages of human prostate development and adenocarcinoma. While primary cells isolated from benign human prostate tissues or tumors exhibit an intermediate phenotype in vitro, they cannot form tumors in vivo unless genetically modified. It is unclear about the stem cell properties and tumorigenicity of intermediate cells.

METHODS

We developed a customized medium to culture primary human intermediate prostate cells, which were transplanted into male immunodeficient NCG mice to examine tumorigenicity in vivo. We treated the cells with different concentrations of dihydrotestosterone (DHT) and enzalutamide in vitro and surgically castrated the mice after cell transplantation in vivo. Immunostaining, qRT-PCR, RNA sequencing, and western blotting were performed to characterize the cells in tissues and 2D and 3D cultures.

RESULTS

We found intermediate cells expressing AR+PSA+CK8+CK5+ in the luminal compartment of human prostate adenocarcinoma by immunostaining. We cultured the primary intermediate cells in vitro, which expressed luminal (AR+PSA+CK8+CK18+), basal (CK5+P63+), intermediate (IVL+), and stem cell (CK4+CK13+PSCA+SOX2+) markers. These cells resisted castration in vitro by upregulating the expression of AR, PSA, and proliferation markers KI67 and PCNA. The intermediate cells had high tumorigenicity in vivo, forming tumors in immunodeficient NCG mice in a month without any genetic modification or co-transplantation with embryonic urogenital sinus mesenchyme (UGSM) cells. We named these cells human castration-resistant intermediate prostate cancer stem cells or CriPCSCs and defined the xenograft model as patient primary cell-derived xenograft (PrDX). Human CriPCSCs resisted castration in vitro and in vivo by upregulating AR expression. Furthermore, human CriPCSCs differentiated into amplifying adenocarcinoma cells of luminal phenotype in PrDX tumors in vivo, which can dedifferentiate into CriPCSCs in vitro.

CONCLUSIONS

Our study identified and established methods for culturing human CriPCSCs, which had high tumorigenicity in vivo without any genetic modification or UGSM co-transplantation. Human CriPCSCs differentiated into amplifying adenocarcinoma cells of luminal phenotype in the fast-growing tumors in vivo, which hold the potential to dedifferentiate into intermediate stem cells. These cells resisted castration by upregulating AR expression. The human CriPCSC and PrDX methods hold significant potential for advancing prostate cancer research and precision medicine.

Hippo signaling modulation and its biological implications in urological malignancies

Although cancer diagnosis and treatment have rapidly advanced in recent decades, urological malignancies, which have high morbidity and mortality rates, are among the most difficult diseases to treat. The Hippo signaling is an evolutionarily conserved pathway in organ size control and tissue homeostasis maintenance. Its downstream effectors, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), are key modulators of numerous physiological and pathological processes. Recent work clearly indicates that Hippo signaling is frequently altered in human urological malignancies. In this review, we discuss the disparate viewpoints on the upstream regulators of YAP/TAZ and their downstream targets and systematically summarize the biological implications. More importantly, we highlight the molecular mechanisms involved in Hippo-YAP signaling to improve our understanding of its role in every stage of prostate cancer, bladder cancer and kidney cancer progression. A better understanding of the biological outcomes of YAP/TAZ modulation will contribute to the establishment of future therapeutic approaches.

Clonal tracking in cancer and metastasis

The eradication of many cancers has proven challenging due to the presence of functionally and genetically heterogeneous clones maintained by rare cancer stem cells (CSCs), which contribute to disease progression, treatment refractoriness, and late relapse. The characterization of functional CSC activity has necessitated the development of modern clonal tracking strategies. This review describes viral-based and CRISPR-Cas9-based cellular barcoding, lineage tracing, and imaging-based approaches. DNA-based cellular barcoding technology is emerging as a powerful and robust strategy that has been widely applied to in vitro and in vivo model systems, including patient-derived xenograft models. This review also highlights the potential of these methods for use in the clinical and drug discovery contexts and discusses the important insights gained from such approaches.

An improved epigenetic counter to track mitotic age in normal and precancerous tissues

The cumulative number of stem cell divisions in a tissue, known as mitotic age, is thought to be a major determinant of cancer-risk. Somatic mutational and DNA methylation (DNAm) clocks are promising tools to molecularly track mitotic age, yet their relationship is underexplored and their potential for cancer risk prediction in normal tissues remains to be demonstrated. Here we build and validate an improved pan-tissue DNAm counter of total mitotic age called stemTOC. We demonstrate that stemTOC's mitotic age proxy increases with the tumor cell-of-origin fraction in each of 15 cancer-types, in precancerous lesions, and in normal tissues exposed to major cancer risk factors. Extensive benchmarking against 6 other mitotic counters shows that stemTOC compares favorably, specially in the preinvasive and normal-tissue contexts. By cross-correlating stemTOC to two clock-like somatic mutational signatures, we confirm the mitotic-like nature of only one of these. Our data points towards DNAm as a promising molecular substrate for detecting mitotic-age increases in normal tissues and precancerous lesions, and hence for developing cancer-risk prediction strategies.

The intricate interplay between cancer stem cells and cell-of-origin of cancer: implications for therapeutic strategies

Background

Cancer stem cells (CSCs) have emerged as pivotal players in tumorigenesis, disease progression, and resistance to therapies.

Objective

This comprehensive review delves into the intricate relationship between CSCs and the cell-of-origin in diverse cancer types.

Design

Comprehensive review of thematically-relevant literature.

Methods

We explore the underlying molecular mechanisms that drive the conversion of normal cells into CSCs and the impact of the cell-of-origin on CSC properties, tumor initiation, and therapeutic responses. Moreover, we discuss potential therapeutic interventions targeting CSCs based on their distinct cell-of-origin characteristics.

Results

Accruing evidence suggest that the cell-of-origin, the cell type from which the tumor originates, plays a crucial role in determining the properties of CSCs and their contribution to tumor heterogeneity.

Conclusion

By providing critical insights into the complex interplay between CSCs and their cellular origins, this article aims to enhance our understanding of cancer biology and pave the way for more effective and personalized cancer treatments.

ERG activates a stem-like proliferation-differentiation program in prostate epithelial cells with mixed basal-luminal identity

To gain insight into how ERG translocations cause prostate cancer, we performed single cell transcriptional profiling of an autochthonous mouse model at an early stage of disease initiation. Despite broad expression of ERG in all prostate epithelial cells, proliferation was enriched in a small, stem-like population with mixed-luminal basal identity (called intermediate cells). Through a series of lineage tracing and primary prostate tissue transplantation experiments, we find that tumor initiating activity resides in a subpopulation of basal cells that co-express the luminal genes Tmprss2 and Nkx3.1 (called BasalLum) but not in the larger population of classical Krt8+ luminal cells. Upon ERG activation, BasalLum cells give rise to the highly proliferative intermediate state, which subsequently transitions to the larger population of Krt8+ luminal cells characteristic of ERG-positive human cancers. Furthermore, this proliferative population is characterized by an ERG-specific chromatin state enriched for NFkB, AP-1, STAT and NFAT binding, with implications for TF cooperativity. The fact that the proliferative potential of ERG is enriched in a small stem-like population implicates the chromatin context of these cells as a critical variable for unmasking its oncogenic activity.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type-specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by 2 orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

The Relationship between Trop-2, Chemotherapeutic Drugs, and Chemoresistance

Trop-2 is a highly conserved one-pass transmembrane mammalian glycoprotein that is normally expressed in tissues such as the lung, intestines, and kidney during embryonic development. It is overexpressed in many epithelial cancers but is absent in non-epithelial tumors. Trop-2 is an intracellular calcium signal transducer that participates in the promotion of cell proliferation, migration, invasion, metastasis, and probably stemness. It also has some tumor suppressor effects. The pro-tumoral actions have been thoroughly investigated and reported. However, Trop-2's activity in chemoresistance is less well known. We review a possible relationship between Trop-2, chemotherapy, and chemoresistance. We conclude that there is a clear role for Trop-2 in some specific chemoresistance events. On the other hand, there is no clear evidence for its participation in multidrug resistance through direct drug transport. The development of antibody conjugate drugs (ACD) centered on anti-Trop-2 monoclonal antibodies opened the gates for the treatment of some tumors resistant to classic chemotherapies. Advanced urothelial tumors and breast cancer were among the first malignancies for which these ACDs have been employed. However, there is a wide group of other tumors that may benefit from anti-Trop-2 therapy as soon as clinical trials are completed.

BMP signaling in cancer stemness and differentiation

The BMP (Bone morphogenetic protein) signaling pathway plays a central role in metazoan biology, intricately shaping embryonic development, maintaining tissue homeostasis, and influencing disease progression. In the context of cancer, BMP signaling exhibits context-dependent dynamics, spanning from tumor suppression to promotion. Cancer stem cells (CSCs), a modest subset of neoplastic cells with stem-like attributes, exert substantial influence by steering tumor growth, orchestrating therapy resistance, and contributing to relapse. A comprehensive grasp of the intricate interplay between CSCs and their microenvironment is pivotal for effective therapeutic strategies. Among the web of signaling pathways orchestrating cellular dynamics within CSCs, BMP signaling emerges as a vital conductor, overseeing CSC self-renewal, differentiation dynamics, and the intricate symphony within the tumor microenvironment. Moreover, BMP signaling's influence in cancer extends beyond CSCs, intricately regulating cellular migration, invasion, and metastasis. This multifaceted role underscores the imperative of comprehending BMP signaling's contributions to cancer, serving as the foundation for crafting precise therapies to navigate multifaceted challenges posed not only by CSCs but also by various dimensions of cancer progression. This article succinctly encapsulates the diverse roles of the BMP signaling pathway across different cancers, spanning glioblastoma multiforme (GBM), diffuse intrinsic pontine glioma (DIPG), colorectal cancer, acute myeloid leukemia (AML), lung cancer, prostate cancer, and osteosarcoma. It underscores the necessity of unraveling underlying mechanisms and molecular interactions. By delving into the intricate tapestry of BMP signaling's engagement in cancers, researchers pave the way for meticulously tailored therapies, adroitly leveraging its dualistic aspects-whether as a suppressor or promoter-to effectively counter the relentless march of tumor progression.

Unveiling novel insights in prostate cancer through single-cell RNA sequencing

Single-cell RNA sequencing (scRNA-seq) is a cutting-edge technology that provides insights at the individual cell level. In contrast to traditional bulk RNA-seq, which captures gene expression at an average level and may overlook important details, scRNA-seq examines each individual cell as a fundamental unit and is particularly well-suited for identifying rare cell populations. Analogous to a microscope that distinguishes various cell types within a tissue sample, scRNA-seq unravels the heterogeneity and diversity within a single cell species, offering great potential as a leading sequencing method in the future. In the context of prostate cancer (PCa), a disease characterized by significant heterogeneity and multiple stages of progression, scRNA-seq emerges as a powerful tool for uncovering its intricate secrets.

Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment

Membrane trafficking and organelle contact sites are important for regulating cell metabolism and survival; processes often deregulated in cancer. Prostate cancer is the second leading cause of cancer-related death in men in the developed world. While early-stage disease is curable by surgery or radiotherapy there is an unmet need to identify prognostic biomarkers, markers to treatment response and new therapeutic targets in intermediate-late stage disease. This study explored the morphology of organelles and membrane contact sites in tumor tissue from normal, low and intermediate histological grade groups. The morphology of organelles in secretory prostate epithelial cells; including Golgi apparatus, ER, lysosomes; was similar in prostate tissue samples across a range of Gleason scores. Mitochondrial morphology was not dramatically altered, but the number of membrane contacts with the ER notably increased with disease progression. A three-fold increase of tight mitochondria-ER membrane contact sites was observed in the intermediate Gleason score group compared to normal tissue. To investigate whether these changes were concurrent with an increased androgen signaling in the tissue, we investigated whether an anti-androgen used in the clinic to treat advanced prostate cancer (enzalutamide) could reverse the phenotype. Patient-derived explant tissues with an intermediate Gleason score were cultured ex vivo in the presence or absence of enzalutamide and the number of ER-mitochondria contacts were quantified for each matched pair of tissues. Enzalutamide treated tissue showed a significant reduction in the number and length of mitochondria-ER contact sites, suggesting a novel androgen-dependent regulation of these membrane contact sites. This study provides evidence for the first time that prostate epithelial cells undergo adaptations in membrane contact sites between mitochondria and the ER during prostate cancer progression. These adaptations are androgen-dependent and provide evidence for a novel hormone-regulated mechanism that support establishment and extension of MAMs. Future studies will determine whether these changes are required to maintain pro-proliferative signaling and metabolic changes that support prostate cancer cell viability.

Basal epithelial cells in prostate development, tumorigenesis, and cancer progression

The prostate epithelium is composed of two predominant cell populations: luminal and basal epithelial cells. Luminal cells have a secretory function that supports male fertility while basal cells function in regeneration and maintenance of epithelial tissue. Recent studies in humans and mice have expanded our knowledge of the role and regulation of luminal and basal cells in prostate organogenesis, development, and homeostasis. The insights from healthy prostate biology can inform studies focused on the origins of prostate cancer, progression of the disease, and development of resistance to targeted hormonal therapies. In this review, we discuss a critical role for basal cells in the development and maintenance of healthy prostate tissue. Additionally, we provide evidence supporting a role for basal cells in oncogenesis and therapeutic resistance mechanisms of prostate cancer. Finally, we describe basal cell regulators that may promote lineage plasticity and basal cell identity in prostate cancers that have developed therapeutic resistance. These regulators could serve as therapeutic targets to inhibit or delay resistance and thereby improve outcomes for prostate cancer patients.

The Molecular Biology of Prostate Cancer Stem Cells: From the Past to the Future

Prostate cancer (PCa) continues to rank as the second leading cause of cancer-related mortality in western countries, despite the golden treatment using androgen deprivation therapy (ADT) or anti-androgen therapy. With decades of research, scientists have gradually realized that the existence of prostate cancer stem cells (PCSCs) successfully explains tumor recurrence, metastasis and therapeutic failure of PCa. Theoretically, eradication of this small population may improve the efficacy of current therapeutic approaches and prolong PCa survival. However, several characteristics of PCSCs make their diminishment extremely challenging: inherent resistance to anti-androgen and chemotherapy treatment, over-activation of the survival pathway, adaptation to tumor micro-environments, escape from immune attack and being easier to metastasize. For this end, a better understanding of PCSC biology at the molecular level will definitely inspire us to develop PCSC targeted approaches. In this review, we comprehensively summarize signaling pathways responsible for homeostatic regulation of PCSCs and discuss how to eliminate these fractional cells in clinical practice. Overall, this study deeply pinpoints PCSC biology at the molecular level and provides us some research perspectives.

Overview of Trop-2 in Cancer: From Pre-Clinical Studies to Future Directions in Clinical Settings

Trophoblast cell surface antigen-2 (Trop-2) is a glycoprotein that was first described as a membrane marker of trophoblast cells and was associated with regenerative abilities. Trop-2 overexpression was also described in several tumour types. Nevertheless, the therapeutic potential of Trop-2 was widely recognized and clinical studies with drug-antibody conjugates have been initiated in various cancer types. Recently, these efforts have been rewarded with the approval of sacituzumab govitecan from both the Food and Drug Administration (FDA) and European Medicines Agency (EMA), for metastatic triple-negative breast cancer patients. In our work, we briefly summarize the various characteristics of cancer cells overexpressing Trop-2, the pre-clinical activities of specific inhibitors, and the role of anti-Trop-2 therapy in current clinical practice. We also review the ongoing clinical trials to provide a snapshot of the future developments of these therapies.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

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.

Innate Immune Program in Formation of Tumor-Initiating Cells from Cells-of-Origin of Breast, Prostate, and Ovarian Cancers

Tumor-initiating cells (TICs), also known as cancer stem cells (CSCs), are cancer cells that can initiate a tumor, possess self-renewal capacity, and can contribute to tumor heterogeneity. TICs/CSCs are developed from their cells-of-origin. In breast, prostate, and ovarian cancers, progenitor cells for mammary alveolar cells, prostate luminal (secretory) cells, and fallopian tube secretory cells are the preferred cellular origins for their corresponding cancer types. These luminal progenitors (LPs) express common innate immune program (e.g., Toll-like receptor (TLR) signaling)-related genes. Microbes such as bacteria are now found in breast, prostate, and fallopian tube tissues and their corresponding cancer types, raising the possibility that their LPs may sense the presence of microbes and trigger their innate immune/TLR pathways, leading to an inflammatory microenvironment. Crosstalk between immune cells (e.g., macrophages) and affected epithelial cells (e.g., LPs) may eventually contribute to formation of TICs/CSCs from their corresponding LPs, in part via STAT3 and/or NFκB pathways. As such, TICs/CSCs can inherit expression of innate-immunity/TLR-pathway-related genes from their cells-of-origin; the innate immune program may also represent their unique vulnerability, which can be explored therapeutically (e.g., by enhancing immunotherapy via augmenting TLR signaling).

Single-cell RNA sequencing reveals intratumoral heterogeneity and potential mechanisms of malignant progression in prostate cancer with perineural invasion

Background: Prostate cancer (PCa) is the second most common cancer among men worldwide. Perineural invasion (PNI) was a prominent characteristic of PCa, which was recognized as a key factor in promoting PCa progression. As a complex and heterogeneous disease, its true condition is difficult to explain thoroughly with conventional bulk RNA sequencing. Thus, an improved understanding of PNI-PCa progression at the single-cell level is needed. Methods: In this study, we performed scRNAseq on tumor tissues of three PNI-PCa patients. Principal component analysis (PCA) and Uniform manifold approximation and projection (UMAP) were used to reduce dimensionality and visualize the cellular composition of tumor tissues. The differently expressed genes among each cluster were identified by EdgeR. GO enrichment analysis was used to understand the roles of genes within the clusters. Pseudotime cell trajectory was used to reveal the molecular pathways underlying cell fate decisions and identify genes whose expression changed as the cells underwent transition. We applied CellPhoneDB to identify cell-cell interactions among the epithelial and neural cells in PNI-PCa. Results: Analysis of the ∼17,000 single-cell transcriptomes in three PNI prostate cancer tissues, we identified 12 major cell clusters, including neural cells and two epithelial subtypes with different expression profiles. We found that basal/intermediate epithelial cell subtypes highly expressed PCa progression-related genes, including PIGR, MMP7, and AGR2. Pseudotime trajectory analysis showed that luminal epithelial cells could be the initiating cells and transition to based/intermediate cells. Gene ontology (GO) enrichment analysis showed that pathways related to cancer progressions, such as lipid catabolic and fatty acid metabolic processes, were significantly enriched in basal/intermediate cells. Our analysis also suggested that basal/intermediate cells communicate closely with neural cells played a potential role in PNI-PCa progression. Conclusion: These results provide our understanding of PNI-PCa cellular heterogeneity and characterize the potential role of basal/intermediate cells in the PNI-PCa progression.

Translational Research for Identifying Potential Early-stage Prostate Cancer Biomarkers

BACKGROUND/AIM

Prostate cancer (PCa) is one of the most common types of cancer in men. Prostate-specific antigen (PSA) is currently the only biomarker used to screen for the risk of developing PCa. Because PSA tests may show false positives, identifying novel PCa-specific biomarkers would improve prediction and diagnosis at an early stage. Previously, we identified a number of genes/microRNAs (miRNAs) in prostate tissue as potential biomarkers of chronic prostatitis in a rat model of chemical-induced prostatitis. The current study aimed to evaluate their potential for use as translational, diagnostic markers in humans.

MATERIALS AND METHODS

We performed quantitative polymerase chain reaction analysis using pathologically clear (normal) or confirmed PCa tissue samples from the same patients (N=18 per group).

RESULTS

Levels (relative fold changes) of bone morphogenetic protein 7 (BMP7) transcripts were significantly lower in PCa tissues, compared with clear tissues, in a paired t-test (p=0.0075). Although neural cell adhesion molecule 1 (NCAM1) transcripts tended to be altered in PCa tissues, statistically insignificant differences were observed (p=0.0521). No statistically significant differences were observed for the other genes/miRNAs analyzed in PCa tissues due to a high degree of individual variance in expression.

CONCLUSION

Similar to the results previously observed in rats, changes in the levels of BMP7 and NCAM1 transcripts were evident in human PCa tissues, suggesting that these genes may serve as potential diagnostic biomarkers during the early stages of PCa. Further studies are needed to determine the potential use of these molecules as biomarkers.

Genomic Characterization of Prostatic Basal Cell Carcinoma

Basal cell carcinoma (BCC) of the prostate is a rare tumor. Compared with the more common acinar adenocarcinoma (AAC) of the prostate, BCCs show features of basal cell differentiation and are thought to be biologically distinct from AAC. The spectrum of molecular alterations of BCC has not been comprehensively described, and genomic studies are lacking. Herein, whole genome sequencing was performed on archival formalin-fixed, paraffin-embedded specimens of two cases with BCC. Prostatic BCCs were characterized by an overall low copy number and mutational burden. Recurrent copy number loss of chromosome 16 was observed. In addition, putative driver gene alterations in KIT, DENND3, PTPRU, MGA, and CYLD were identified. Mechanistically, depletion of the CYLD protein resulted in increased proliferation of prostatic basal cells in vitro. Collectively, these studies show that prostatic BCC displays distinct genomic alterations from AAC and highlight a potential role for loss of chromosome 16 in the pathogenesis of this rare tumor type.

Defining cellular population dynamics at single-cell resolution during prostate cancer progression

Advanced prostate malignancies are a leading cause of cancer-related deaths in men, in large part due to our incomplete understanding of cellular drivers of disease progression. We investigate prostate cancer cell dynamics at single-cell resolution from disease onset to the development of androgen independence in an in vivo murine model. We observe an expansion of a castration-resistant intermediate luminal cell type that correlates with treatment resistance and poor prognosis in human patients. Moreover, transformed epithelial cells and associated fibroblasts create a microenvironment conducive to pro-tumorigenic immune infiltration, which is partially androgen responsive. Androgen-independent prostate cancer leads to significant diversification of intermediate luminal cell populations characterized by a range of androgen signaling activity, which is inversely correlated with proliferation and mRNA translation. Accordingly, distinct epithelial populations are exquisitely sensitive to translation inhibition, which leads to epithelial cell death, loss of pro-tumorigenic signaling, and decreased tumor heterogeneity. Our findings reveal a complex tumor environment largely dominated by castration-resistant luminal cells and immunosuppressive infiltrates.

Single-cell RNA-sequencing technology demonstrates the heterogeneity between aged prostate peripheral and transitional zone

BACKGROUND

Identifying cellular and functional heterogeneity within aged prostate is critical for understanding the spatial distribution of prostate diseases.

METHODS

Aged human prostate peripheral zone (PZ) and transitional zone (TZ) tissues were used for single-cell RNA-sequencing. Results were validated by immunofluorescence staining.

RESULTS

We found that club/hillock epithelial cells, compared with other epithelial cells, had significantly higher NOTCH signaling activity and expressed higher levels of neuro-stems but lower androgen-related genes. These cells were primarily found in the TZ and provided a stem-like niche around the proximal prostate ducts. Significant heterogeneity was observed in the aged luminal population. A novel TFF3+ luminal subtype with elevated MYC and E2F pathway activities was observed, primarily in the PZ. Further analysis revealed that epithelial cells in the TZ had higher levels of stem- and inflammation-related pathway activities but lower androgen/lineage-related pathway activities than those in the PZ. Notably, the activation of MYC, E2F and DNA repair pathways significantly increased in PZ luminal cells. In the immune landscape, we found that the immune microenvironment in the TZ is more complex and disordered with more infiltration of NK and Treg cells. CD8 T cell and macrophage in the TZ exhibit both inflammation activation and suppression phenotypes. In the stroma, the TZ had a higher fibroblast density, and fibroblasts in the TZ exhibited stronger transcriptome activity in immunity and proliferation. Ligand-receptor interaction analysis revealed that fibroblasts could contribute to a NOTCH signaling niche for club/hillock cells in the TZ and balance the prostate immune microenvironment. The activation of stem properties, inflammatory infiltration and loss of androgen/lineage activity are prominent features distinguishing the TZ from PZ.

CONCLUSIONS

Our study explains the heterogeneity between the TZ and PZ of aged prostate, which may help understand the spatial distribution of prostate diseases and establish a foundation for novel target discovery.

Prostate Cancer Stem Cells: Clinical Aspects and Targeted Therapies

Despite decades of research and successful improvements in diagnosis and therapy, prostate cancer (PC) remains a major challenge. In recent years, it has become clear that PC stem cells (PCSCs) are the driving force in tumorigenesis, relapse, metastasis, and therapeutic resistance of PC. In this minireview, we discuss the impact of PCSCs in the clinical practice. Moreover, new therapeutic approaches to combat PCSCs are presented with the aim to achieve an improved outcome for patients with PC.

ETS factors in prostate cancer

The ETS family of proteins consists of 28 transcription factors, many of which play critical roles in both normal tissue development and homeostasis and have been implicated in development and progression of a variety of cancers. In prostate cancer, gene fusion and overexpression of ETS factors ERG, FLI1, ETV1, ETV4 and ETV5 have been found in half of prostate cancer patients in Caucasian men and define the largest genetic subtype of prostate cancer. This review summarizes the data on the discovery, modeling, molecular taxonomy, lineage plasticity and therapeutic targeting of ETS family members in prostate cancer.

Single-cell analysis of human primary prostate cancer reveals the heterogeneity of tumor-associated epithelial cell states

Prostate cancer is the second most common malignancy in men worldwide and consists of a mixture of tumor and non-tumor cell types. To characterize the prostate cancer tumor microenvironment, we perform single-cell RNA-sequencing on prostate biopsies, prostatectomy specimens, and patient-derived organoids from localized prostate cancer patients. We uncover heterogeneous cellular states in prostate epithelial cells marked by high androgen signaling states that are enriched in prostate cancer and identify a population of tumor-associated club cells that may be associated with prostate carcinogenesis. ERG-negative tumor cells, compared to ERG-positive cells, demonstrate shared heterogeneity with surrounding luminal epithelial cells and appear to give rise to common tumor microenvironment responses. Finally, we show that prostate epithelial organoids harbor tumor-associated epithelial cell states and are enriched with distinct cell types and states from their parent tissues. Our results provide diagnostically relevant insights and advance our understanding of the cellular states associated with prostate carcinogenesis.

Experimental challenges to modeling prostate cancer heterogeneity

Tumor heterogeneity plays a key role in prostate cancer prognosis, therapy selection, relapse, and acquisition of treatment resistance. Prostate cancer presents a heterogeneous diversity at inter- and intra-tumor and inter-patient levels which are influenced by multiple intrinsic and/or extrinsic factors. Recent studies have started to characterize the complexity of prostate tumors and these different tiers of heterogeneity. In this review, we discuss the most common factors that contribute to tumoral diversity. Moreover, we focus on the description of the in vitro and in vivo approaches, as well as high-throughput technologies, that help to model intra-tumoral diversity. Further understanding tumor heterogeneities and the challenges they present will guide enhanced patient risk stratification, aid the design of more precise therapies, and ultimately help beat this chameleon-like disease.

Recent advances in tissue stem cells

Stem cells are undifferentiated cells capable of self-renewal and differentiation, giving rise to specialized functional cells. Stem cells are of pivotal importance for organ and tissue development, homeostasis, and injury and disease repair. Tissue-specific stem cells are a rare population residing in specific tissues and present powerful potential for regeneration when required. They are usually named based on the resident tissue, such as hematopoietic stem cells and germline stem cells. This review discusses the recent advances in stem cells of various tissues, including neural stem cells, muscle stem cells, liver progenitors, pancreatic islet stem/progenitor cells, intestinal stem cells, and prostate stem cells, and the future perspectives for tissue stem cell research.

Exosomal long noncoding RNA HOXD-AS1 promotes prostate cancer metastasis via miR-361-5p/FOXM1 axis

Development of distant metastasis is the main cause of deaths in prostate cancer (PCa) patients. Understanding the mechanism of PCa metastasis is of utmost importance to improve its prognosis. The role of exosomal long noncoding RNA (lncRNA) has been reported not yet fully understood in the metastasis of PCa. Here, we discovered an exosomal lncRNA HOXD-AS1 is upregulated in castration resistant prostate cancer (CRPC) cell line derived exosomes and serum exosomes from metastatic PCa patients, which correlated with its tissue expression. Further investigation confirmed exosomal HOXD-AS1 promotes prostate cancer cell metastasis in vitro and in vivo by inducing metastasis associated phenotype. Mechanistically exosomal HOXD-AS1 was internalized directly by PCa cells, acting as competing endogenous RNA (ceRNA) to modulate the miR-361-5p/FOXM1 axis, therefore promoting PCa metastasis. In addition, we found that serum exosomal HOXD-AS1 was upregulated in metastatic PCa patients, especially those with high volume disease. And it is correlated closely with Gleason Score, distant and nodal metastasis, Prostatic specific antigen (PSA) recurrence free survival, and progression free survival (PFS). This sheds a new insight into the regulation of PCa distant metastasis by exosomal HOXD-AS1 mediated miR-361-5p/FOXM1 axis, and provided a promising liquid biopsy biomarker to guide the detection and treatment of metastatic PCa.

Live cell molecular analysis of primary prostate cancer organoids identifies persistent androgen receptor signaling

Prostate Cancer (PC) is a disease with remarkable tumor heterogeneity that often manifests in significant intra-patient variability with regards to clinical outcomes and treatment response. Commonly available PC cell lines do not accurately reflect the complexity of this disease and there is critical need for development of new models to recapitulate the intricate hierarchy of tumor pathogenesis. In current study, we established ex vivo primary patient-derived cancer organoid (PDCO) cultures from prostatectomy specimens of patients with locally advanced PC. We then performed a comprehensive multi-parameter characterization of the cellular composition utilizing a novel approach for live-cell staining and direct imaging in the integrated microfluidic Stacks device. Using orthogonal flow cytometry analysis, we demonstrate that primary PDCOs maintain distinct subsets of epithelial cells throughout culture and that these cells conserve expression of androgen receptor (AR)-related elements. Furthermore, to confirm the tumor-origin of the PDCOs we have analyzed the expression of PC-associated epigenetic biomarkers including promoter methylation of the GSTP1, RASSF1 and APC and RARb genes by employing a novel microfluidic rare-event screening protocol. These results demonstrate that this ex vivo PDCO model recapitulates the complexity of the epithelial tumor microenvironment of multifocal PC using orthogonal analyses. Furthermore, we propose to leverage the Stacks microfluidic device as a high-throughput, translational platform to interrogate phenotypic and molecular endpoints with the capacity to incorporate a complex tumor microenvironment.

MicroRNA-regulated transcriptome analysis identifies four major subtypes with prognostic and therapeutic implications in prostate cancer

MicroRNA (miRNA) deregulation plays a critical role in the heterogeneous development of prostate cancer (PCa) by tuning mRNA levels. Herein, we aimed to characterize the molecular features of PCa by clustering the miRNA-regulated transcriptome with non-negative matrix factorization. Using 478 PCa samples from The Cancer Genome Atlas, four molecular subtypes (S-I, S-II, S-III, and S-IV) were identified and validated in two merged microarray and RNAseq datasets with 656 and 252 samples, respectively. Interestingly, the four subtypes showed distinct clinical and biological features after comprehensive analyses of clinical features, multiomic profiles, immune infiltration, and drug sensitivity. S-I is basal/stem/mesenchymal-like and immune-excluded with marked transforming growth factor β, epithelial-mesenchymal transition and hypoxia signals, increased sensitivity to olaparib, and intermediate prognosis. S-II is luminal/metabolism-active and responsive to androgen deprivation therapy with frequent TMPRSS2-ERG fusion and a good prognosis. S-III is characterized by moderate proliferative and metabolic activity, sensitivity to taxane-based chemotherapy, and intermediate prognosis. S-IV is highly proliferative with moderate EMT and stemness, frequent deletions of TP53, PTEN and RB, and the poorest prognosis; it is also immune-inflamed and sensitive to anti-PD-L1 therapy. Overall, based on miRNA-regulated gene profiles, this study identified four distinct PCa subtypes that could improve risk stratification at diagnosis and provide therapeutic guidance.

Virtual screening and biological evaluation of PPARγ antagonists as potential anti-prostate cancer agents

The peroxisome proliferator-activated receptor gamma (PPARγ) was identified as an oncogene and it plays a key role in prostate cancer (PC) development and progression. PPARγ antagonists have been shown to inhibit PC cell growth. Herein, we describe a virtual screening-based approach that led to the discovery of novel PPARγ antagonist chemotypes that bind at the allosteric pocket. Arg288, Lys367, and His449 appear to be important for PPARγ antagonist binding.

Aging of the progenitor cells that initiate prostate cancer

Many organs experience a loss of tissue mass and a decline in regenerative capacity during aging. In contrast, the prostate continues to grow in volume. In fact, age is the most important risk factor for prostate cancer. However, the age-related factors that influence the composition, morphology and molecular features of prostate epithelial progenitor cells, the cells-of-origin for prostate cancer, are poorly understood. Here, we review the evidence that prostate luminal progenitor cells are expanded with age. We explore the age-related changes to the microenvironment that may influence prostate epithelial cells and risk of transformation. Finally, we raise a series of questions about models of aging and regulators of prostate aging which need to be addressed. A fundamental understanding of aging in the prostate will yield critical insights into mechanisms that promote the development of age-related prostatic disease.

Discovery and 3D imaging of a novel ΔNp63-expressing basal cell type in human pancreatic ducts with implications in disease

OBJECTIVE

The aggressive basal-like molecular subtype of pancreatic ductal adenocarcinoma (PDAC) harbours a ΔNp63 (p40) gene expression signature reminiscent of a basal cell type. Distinct from other epithelia with basal tumours, ΔNp63+ basal cells reportedly do not exist in the normal pancreas.

DESIGN

We evaluated ΔNp63 expression in human pancreas, chronic pancreatitis (CP) and PDAC. We further studied in depth the non-cancerous tissue and developed a three-dimensional (3D) imaging protocol (FLIP-IT, Fluorescence Light sheet microscopic Imaging of Paraffin-embedded or Intact Tissue) to study formalin-fixed paraffin-embedded samples at single cell resolution. Pertinent mouse models and HPDE cells were analysed.

RESULTS

In normal human pancreas, rare ΔNp63+ cells exist in ducts while their prevalence increases in CP and in a subset of PDAC. In non-cancer tissue, ΔNp63+ cells are atypical KRT19+ duct cells that overall lack SOX9 expression while they do express canonical basal markers and pertain to a niche of cells expressing gastrointestinal stem cell markers. 3D views show that the basal cells anchor on the basal membrane of normal medium to large ducts while in CP they exist in multilayer dome-like structures. In mice, ΔNp63 is not found in adult pancreas nor in selected models of CP or PDAC, but it is induced in organoids from larger Sox9low ducts. In HPDE, ΔNp63 supports a basal cell phenotype at the expense of a classical duct cell differentiation programme.

CONCLUSION

In larger human pancreatic ducts, basal cells exist. ΔNp63 suppresses duct cell identity. These cells may play an important role in pancreatic disease, including PDAC ontogeny, but are not present in mouse models.

Ras/ERK and PI3K/AKT signaling differentially regulate oncogenic ERG mediated transcription in prostate cells

The TMPRSS2/ERG gene rearrangement occurs in 50% of prostate tumors and results in expression of the transcription factor ERG, which is normally silent in prostate cells. ERG expression promotes prostate tumor formation and luminal epithelial cell fates when combined with PI3K/AKT pathway activation, however the mechanism of synergy is not known. In contrast to luminal fates, expression of ERG alone in immortalized normal prostate epithelial cells promotes cell migration and epithelial to mesenchymal transition (EMT). Migration requires ERG serine 96 phosphorylation via endogenous Ras/ERK signaling. We found that a phosphomimetic mutant, S96E ERG, drove tumor formation and clonogenic survival without activated AKT. S96 was only phosphorylated on nuclear ERG, and differential recruitment of ERK to a subset of ERG-bound chromatin associated with ERG-activated, but not ERG-repressed genes. S96E did not alter ERG genomic binding, but caused a loss of ERG-mediated repression, EZH2 binding and H3K27 methylation. In contrast, AKT activation altered the ERG cistrome and promoted expression of luminal cell fate genes. These data suggest that, depending on AKT status, ERG can promote either luminal or EMT transcription programs, but ERG can promote tumorigenesis independent of these cell fates and tumorigenesis requires only the transcriptional activation function.

ERG is the most common oncogene in prostate cancer. The ERG protein can bind DNA and can activate some genes and repress others. Previous studies indicated that ERG cannot promote cancer by itself, but that ERG works together with mutations that activate the protein AKT. In this study we found that activation of AKT changes the genes that ERG regulates, leading to luminal epithelial differentiation, which is a hallmark of most prostate tumors. However, we also found that a mutant version of ERG that can activate, but cannot repress genes, can drive prostate tumorigenesis without activation of AKT, but this mutant ERG cannot promote luminal differentiation. Our findings suggest that ERG mediated tumorigenesis only requires ERG’s activation function and can occur independent of luminal cell differentiation.

An overview of the latest in state-of-the-art murine models for prostate cancer

INTRODUCTION

Prostate cancer (PCa) is a complex, heterogenous and multifocal disease, which is debilitating for patients and often fatal - due to bone metastasis and castration-resistant cancer. The use of murine models that mimic human disease has been crucial in the development of innovative therapies and for better understanding the mechanisms associated with initiation and progression of PCa.

AREAS COVERED

This review presents a critical analysis of murine models for the study of PCa, highlighting their strengths, weaknesses and applications.

EXPERT OPINION

In animal models, disease may not occur exactly as it does in humans, and sometimes the levels of efficacy that certain treatments obtain in animal models cannot be translated into clinical practice. To choose the most appropriate animal model for each research work, it is crucial to understand the anatomical and physiological differences between the mouse and the human prostate, while it is also important to identify biological similarities and differences between murine and human prostate tumors. Although significant progress has already been made, thanks to many years of research and study, the number of new challenges and obstacles to overcome mean there is a long and difficult road still to travel.

Chromatin and Epigenetic Dysregulation of Prostate Cancer Development, Progression, and Therapeutic Response

The dysregulation of chromatin and epigenetics has been defined as the overarching cancer hallmark. By disrupting transcriptional regulation in normal cells and mediating tumor progression by promoting cancer cell plasticity, this process has the ability to mediate all defined hallmarks of cancer. In this review, we collect and assess evidence on the contribution of chromatin and epigenetic dysregulation in prostate cancer. We highlight important mechanisms leading to prostate carcinogenesis, the emergence of castration-resistance upon treatment with androgen deprivation therapy, and resistance to antiandrogens. We examine in particular the contribution of chromatin structure and epigenetics to cell lineage commitment, which is dysregulated during tumorigenesis, and cell plasticity, which is altered during tumor progression.

Prostate cancer cell heterogeneity and plasticity: Insights from studies of genetically-engineered mouse models

Although prostate adenocarcinoma lacks distinguishable histopathological subtypes, prostate cancer displays significant inter- and intratumor heterogeneity at the molecular level and with respect to disease prognosis and treatment response. In principle, understanding the basis for prostate cancer heterogeneity can help distinguish aggressive from indolent disease, and help overcome castration-resistance in advanced prostate cancer. In this review, we will discuss recent advances in understanding the cell types of origin, putative cancer stem cells, and tumor plasticity in prostate cancer, focusing on insights from studies of genetically engineered mouse models (GEMMs). We will also outline future directions for investigating tumor heterogeneity using mouse models of prostate cancer.

Normal Basal Epithelial Cells Stimulate the Migration and Invasion of Prostate Cancer Cell RM-1 by TGF-β1/STAT3 Axis in vitro

Aim

Basal epithelial cells are absent in distant prostate cancer. This study aimed to investigate whether basal epithelial cells could suppress migration and invasion of prostate cancer cells to become a new treatment strategy for prostate cancer.

Main Methods

Basal epithelial cells were identified by immunofluorescence with anti-p63. Wound healing assays or transwell assays were used to explore the effects of basal epithelial cells, TGF-β1, SB431542 (inhibitor of TGF-β type I receptor) or stattic (inhibitor of phosphorylated STAT3) on migration or invasion of mouse prostate cancer cell (RM-1). Concentration of TGF-β1 was measured by ELISA assay. HE staining was used to investigate cell morphology. Immunocytochemistry with anti-p63 was used to identify basal epithelial cells. Levels of STAT3, p-STAT3 (Ser727) and proteins associated with EMT were measured with Western blot assay. Cell proliferation was measured with MTT or CCK8 assay.

Results

Normal basal epithelial cells acquired from mouse prostate were specific to anti-p63 and more than 90%. Basal epithelial cells and RM-1 could both secrete TGF-β1. Basal epithelial cells and TGF-β1 promoted the migration and invasion of RM-1 through changing the cell morphology and up-regulating expression of ZEB1, N-cadherin, vimentin, snail and p-STAT3 (Ser727), at the same time down-regulating E-cadherin of RM-1. SB431542 strongly suppressed migration, invasion as well as the expressions of EMT relevant proteins and p-STAT3 (Ser727) of co-cultured RM-1. In addition, stattic suppressed proliferation, migration and invasion of non-treated RM-1 and co-cultured RM-1.

Conclusion

Our study suggests that normal basal epithelial cells might stimulate the migration and invasion of RM-1 by TGF-β1/STAT3 axis which could be suppressed by inhibitor of TGF-β receptor and inhibitor of p-STAT3. So, basal epithelial cells might not become a treatment strategy for prostate cancer, but our results could provide some researching references for other diseases which include basal epithelial cells such as prostatic intraepithelial neoplasia, prostatic hyperplasia, cervical cancer, or urinary bladder cancer.

Resistance to androgen receptor signaling inhibition does not necessitate development of neuroendocrine prostate cancer

Resistance to AR signaling inhibitors (ARSis) in a subset of metastatic castration-resistant prostate cancers (mCRPCs) occurs with the emergence of AR^– neuroendocrine prostate cancer (NEPC) coupled with mutations/deletions in PTEN, TP53, and RB1 and the overexpression of DNMTs, EZH2, and/or SOX2. To resolve whether the lack of AR is the driving factor for the emergence of the NE phenotype, molecular, cell, and tumor biology analyses were performed on 23 xenografts derived from patients with PC, recapitulating the full spectrum of genetic alterations proposed to drive NE differentiation. Additionally, phenotypic response to CRISPR/Cas9-mediated AR KO in AR⁺ CRPC cells was evaluated. These analyses document that (a) ARSi-resistant NEPC developed without androgen deprivation treatment; (b) ARS in ARSi-resistant AR⁺/NE⁺ double-positive “amphicrine” mCRPCs did not suppress NE differentiation; (c) the lack of AR expression did not necessitate acquiring a NE phenotype, despite concomitant mutations/deletions in PTEN and TP53, and the loss of RB1 but occurred via emergence of an AR^–/NE^– double-negative PC (DNPC); (d) despite DNPC cells having homogeneous genetic driver mutations, they were phenotypically heterogeneous, expressing basal lineage markers alone or in combination with luminal lineage markers; and (e) AR loss was associated with AR promoter hypermethylation in NEPCs but not in DNPCs.

The role of Trop2 in prostate cancer: an oncogene, biomarker, and therapeutic target

Prostate cancer remains the second leading cause of cancer-associated deaths amongst American men. Trop2, a cell surface glycoprotein, correlates with poor clinical outcome and is highly expressed in metastatic, treatment-resistant prostate cancer. High levels of Trop2 are prognostic for biochemical recurrence. Trop2 regulates tumor growth and metastatic ability of prostate cancer. Moreover, overexpression of Trop2 drives the transdifferentiation to neuroendocrine phenotype in prostate cancer. In addition, Trop2 is overexpressed across epithelial cancers and has emerged as a promising therapeutic target in various solid epithelial cancers. The FDA (Food and Drug Administration) recently approved the use of a Trop2-targeting ADC (antibody-drug conjugate), Sacituzumab Govitecan (IMMU-132), for metastatic, triple-negative breast cancer with at least two prior therapies. Here, we review the role of Trop2 in prostate tumorigenesis and its potential as a promising biomarker and therapeutic target for prostate cancer.

Prostate cancer

Prostate cancer is a complex disease that affects millions of men globally, predominantly in high human development index regions. Patients with localized disease at a low to intermediate risk of recurrence generally have a favourable outcome of 99% overall survival for 10 years if the disease is detected and treated at an early stage. Key genetic alterations include fusions of TMPRSS2 with ETS family genes, amplification of the MYC oncogene, deletion and/or mutation of PTEN and TP53 and, in advanced disease, amplification and/or mutation of the androgen receptor (AR). Prostate cancer is usually diagnosed by prostate biopsy prompted by a blood test to measure prostate-specific antigen levels and/or digital rectal examination. Treatment for localized disease includes active surveillance, radical prostatectomy or ablative radiotherapy as curative approaches. Men whose disease relapses after prostatectomy are treated with salvage radiotherapy and/or androgen deprivation therapy (ADT) for local relapse, or with ADT combined with chemotherapy or novel androgen signalling-targeted agents for systemic relapse. Advanced prostate cancer often progresses despite androgen ablation and is then considered castration-resistant and incurable. Current treatment options include AR-targeted agents, chemotherapy, radionuclides and the poly(ADP-ribose) inhibitor olaparib. Current research aims to improve prostate cancer detection, management and outcomes, including understanding the fundamental biology at all stages of the disease.

Prostate cancer

Prostate cancer is a complex disease that affects millions of men globally, predominantly in high human development index regions. Patients with localized disease at a low to intermediate risk of recurrence generally have a favourable outcome of 99% overall survival for 10 years if the disease is detected and treated at an early stage. Key genetic alterations include fusions of TMPRSS2 with ETS family genes, amplification of the MYC oncogene, deletion and/or mutation of PTEN and TP53 and, in advanced disease, amplification and/or mutation of the androgen receptor (AR). Prostate cancer is usually diagnosed by prostate biopsy prompted by a blood test to measure prostate-specific antigen levels and/or digital rectal examination. Treatment for localized disease includes active surveillance, radical prostatectomy or ablative radiotherapy as curative approaches. Men whose disease relapses after prostatectomy are treated with salvage radiotherapy and/or androgen deprivation therapy (ADT) for local relapse, or with ADT combined with chemotherapy or novel androgen signalling-targeted agents for systemic relapse. Advanced prostate cancer often progresses despite androgen ablation and is then considered castration-resistant and incurable. Current treatment options include AR-targeted agents, chemotherapy, radionuclides and the poly(ADP-ribose) inhibitor olaparib. Current research aims to improve prostate cancer detection, management and outcomes, including understanding the fundamental biology at all stages of the disease.

Progenitors in prostate development and disease

The prostate develops by epithelial budding and branching processes that occur during fetal and postnatal stages. The adult prostate demonstrates remarkable regenerative capacity, with the ability to regrow to its original size over multiple cycles of castration and androgen administration. This capacity for controlled regeneration prompted the search for an androgen-independent epithelial progenitor in benign prostatic hyperplasia (BPH) and prostate cancer (PCa). BPH is hypothesized to be a reawakening of ductal branching, resulting in the formation of new proximal glands, all while androgen levels are decreasing in the aging male. Advanced prostate cancer can be slowed with androgen deprivation, but resistance eventually occurs, suggesting the existence of an androgen-independent progenitor. Recent studies indicate that there are multiple castration-insensitive epithelial cell types in the proximal area of the prostate, but not all act as progenitors during prostate development or regeneration. This review highlights how recent cellular and anatomical studies are changing our perspective on the identity of the prostate progenitor.

Cell of origin in biliary tract cancers and clinical implications

Biliary tract cancers (BTCs) are aggressive epithelial malignancies that can arise at any point of the biliary tree. Albeit rare, their incidence and mortality rates have been rising steadily over the past 40 years, highlighting the need to improve current diagnostic and therapeutic strategies. BTCs show high inter- and intra-tumour heterogeneity both at the morphological and molecular level. Such complex heterogeneity poses a substantial obstacle to effective interventions. It is widely accepted that the observed heterogeneity may be the result of a complex interplay of different elements, including risk factors, distinct molecular alterations and multiple potential cells of origin. The use of genetic lineage tracing systems in experimental models has identified cholangiocytes, hepatocytes and/or progenitor-like cells as the cells of origin of BTCs. Genomic evidence in support of the distinct cell of origin hypotheses is growing. In this review, we focus on recent advances in the histopathological subtyping of BTCs, discuss current genomic evidence and outline lineage tracing studies that have contributed to the current knowledge surrounding the cell of origin of these tumours.

HAND1 and BARX1 Act as Transcriptional and Anatomic Determinants of Malignancy in Gastrointestinal Stromal Tumor

PURPOSE

Gastrointestinal stromal tumor (GIST) arises from interstitial cells of Cajal (ICC) or their precursors, which are present throughout the gastrointestinal tract. Although gastric GIST is commonly indolent and small intestine GIST more aggressive, a molecular understanding of disease behavior would inform therapy decisions in GIST. Although a core transcription factor (TF) network is conserved across GIST, accessory TFs HAND1 and BARX1 are expressed in a disease state-specific pattern. Here, we characterize two divergent transcriptional programs maintained by HAND1 and BARX1, and evaluate their association with clinical outcomes.

EXPERIMENTAL DESIGN

We evaluated RNA sequencing and TF chromatin immunoprecipitation with sequencing in GIST samples and cultured cells for transcriptional programs associated with HAND1 and BARX1. Multiplexed tissue-based cyclic immunofluorescence and IHC evaluated tissue- and cell-level expression of TFs and their association with clinical factors.

RESULTS

We show that HAND1 is expressed in aggressive GIST, modulating KIT and core TF expression and supporting proliferative cellular programs. In contrast, BARX1 is expressed in indolent and micro-GISTs. HAND1 and BARX1 expression were superior predictors of relapse-free survival, as compared with standard risk stratification, and they predict progression-free survival on imatinib. Reflecting the developmental origins of accessory TF programs, HAND1 was expressed solely in small intestine ICCs, whereas BARX1 expression was restricted to gastric ICCs.

CONCLUSIONS

Our results define anatomic and transcriptional determinants of GIST and molecular origins of clinical phenotypes. Assessment of HAND1 and BARX1 expression in GIST may provide prognostic information and improve clinical decisions on the administration of adjuvant therapy.

Establishment of a novel anti-TROP2 monoclonal antibody TrMab-29 for immunohistochemical analysis

TROP2 is a type I transmembrane glycoprotein originally identified in human trophoblast cells that is overexpressed in several types of cancer. To better understand the role of TROP2 in cancer, we herein aimed to develop a sensitive and specific anti-TROP2 monoclonal antibody (mAb) for use in flow cytometry, Western blot, and immunohistochemistry using a Cell-Based Immunization and Screening (CBIS) method. Two mice were immunized with N-terminal PA-tagged and C-terminal RAP/MAP-tagged TROP2-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/PA-TROP2-RAP-MAP), and hybridomas showing strong signals from PA-tagged TROP2-overexpressed CHO-K1 cells (CHO/TROP2-PA) and weak-to-no signals from CHO-K1 cells were selected using flow cytometry. We demonstrated using flow cytometry that the established anti-TROP2 mAb, TrMab-29 (mouse IgG₁ kappa), detected TROP2 in MCF7 breast cancer cell line as well as CHO/TROP2-PA cells. Western blot analysis showed a 40 kDa band in lysates prepared from both CHO/TROP2-PA and MCF7 cells. Furthermore, TROP2 was strongly detected by immunohistochemical analysis using TrMab-29, indicating that TrMab-29 may be a valuable tool for the detection of TROP2 in cancer.

Single-cell analysis supports a luminal-neuroendocrine transdifferentiation in human prostate cancer

Neuroendocrine prostate cancer is one of the most aggressive subtypes of prostate tumor. Although much progress has been made in understanding the development of neuroendocrine prostate cancer, the cellular architecture associated with neuroendocrine differentiation in human prostate cancer remain incompletely understood. Here, we use single-cell RNA sequencing to profile the transcriptomes of 21,292 cells from needle biopsies of 6 castration-resistant prostate cancers. Our analyses reveal that all neuroendocrine tumor cells display a luminal-like epithelial phenotype. In particular, lineage trajectory analysis suggests that focal neuroendocrine differentiation exclusively originate from luminal-like malignant cells rather than basal compartment. Further tissue microarray analysis validates the generality of the luminal phenotype of neuroendocrine cells. Moreover, we uncover neuroendocrine differentiation-associated gene signatures that may help us to further explore other intrinsic molecular mechanisms deriving neuroendocrine prostate cancer. In summary, our single-cell study provides direct evidence into the cellular states underlying neuroendocrine transdifferentiation in human prostate cancer.

Development and characterization of TrMab‑6, a novel anti‑TROP2 monoclonal antibody for antigen detection in breast cancer

Trophoblast cell-surface antigen 2 (TROP2) is a type I transmembrane glycoprotein that is overexpressed in a number of cancer types, including triple-negative breast cancer. The current study aimed to develop a highly sensitive and specific monoclonal antibody (mAb) targeting TROP2, which could be used to evaluate TROP2 expression using flow cytometry, western blot analysis and immunohistochemistry by employing the Cell-Based Immunization and Screening (CBIS) method. The established anti-TROP2 mAb, TrMab-6 (mouse IgG_2b, κ), detected TROP2 on PA-tagged TROP2-overexpressing Chinese hamster ovary-K1 (CHO/TROP2-PA) and breast cancer cell lines, including MCF7 and BT-474 using flow cytometry. Western blot analysis indicated a 40 kDa band in lysates prepared from CHO/TROP2-PA, MCF7 and BT-474 cells. Furthermore, TROP2 in 57/61 (93.4%) of the breast cancer specimens was strongly detected using immunohistochemical analysis with TrMab-6. In conclusion, the current study demonstrated that TrMab-6 may be a valuable tool for the detection of TROP2 in a wide variety of breast cancer types.