The Stromal Niche for Epithelial Stem Cells: A Template for Regeneration and a Brake on Malignancy

Targeting Tumor Heterogeneity by Breaking a Stem Cell and Epithelial Niche Interaction Loop

Tumor heterogeneity, the presence of multiple distinct subpopulations of cancer cells between patients or among the same tumors, poses a major challenge to current targeted therapies. The way these different subpopulations interact among themselves and the stromal niche environment, and how such interactions affect cancer stem cell behavior has remained largely unknown. Here, it is shown that an FGF-BMP7-INHBA signaling positive feedback loop integrates interactions among different cell populations, including mammary gland stem cells, luminal epithelial and stromal fibroblast niche components not only in organ regeneration but also, with certain modifications, in cancer progression. The reciprocal dependence of basal stem cells and luminal epithelium is based on basal-derived BMP7 and luminal-derived INHBA, which promote their respective expansion, and is regulated by stromal-epithelial FGF signaling. Targeting this interaction loop, for example, by reducing the function of one or more of its components, inhibits organ regeneration and breast cancer progression. The results have profound implications for overcoming drug resistance because of tumor heterogeneity in future targeted therapies.

Specifics of Cryopreservation of Hydrogel Biopolymer Scaffolds with Encapsulated Mesenchymal Stem Cells

The demand for regenerative medicine products is growing rapidly in clinical practice. Unfortunately, their use has certain limitations. One of these, which significantly constrains the widespread distribution and commercialization of such materials, is their short life span. For products containing suspensions of cells, this issue can be solved by using cryopreservation. However, this approach is rarely used for multicomponent tissue-engineered products due to the complexity of selecting appropriate cryopreservation protocols and the lack of established criteria for assessing the quality of such products once defrosted. Our research is aimed at developing a cryopreservation protocol for an original hydrogel scaffold with encapsulated MSCs and developing a set of criteria for assessing the quality of their functional activity in vitro. The scaffolds were frozen using two alternative types of cryocontainers and stored at either -40 °C or -80 °C. After cryopreservation, the external state of the scaffolds was evaluated in addition to recording the cell viability, visible changes during subsequent cultivation, and any alterations in proliferative and secretory activity. These observations were compared to those of scaffolds cultivated without cryopreservation. It was shown that cryopreservation at -80 °C in an appropriate type of cryocontainer was optimal for the hydrogels/adipose-derived stem cells (ASCs) tested if it provided a smooth temperature decrease during freezing over a period of at least three hours until the target values of the cryopreservation temperature regimen were reached. It was shown that evaluating a set of indicators, including the viability, the morphology, and the proliferative and secretory activity of the cells, enables the characterization of the quality of a tissue-engineered construct after its withdrawal from cryopreservation, as well as indicating the effectiveness of the cryopreservation protocol.

Helicobacter pylori-activated fibroblasts as a silent partner in gastric cancer development

The discovery of Helicobacter pylori (Hp) infection of gastric mucosa leading to active chronic gastritis, gastroduodenal ulcers, and MALT lymphoma laid the groundwork for understanding of the general relationship between chronic infection, inflammation, and cancer. Nevertheless, this sequence of events is still far from full understanding with new players and mediators being constantly identified. Originally, the Hp virulence factors affecting mainly gastric epithelium were proposed to contribute considerably to gastric inflammation, ulceration, and cancer. Furthermore, it has been shown that Hp possesses the ability to penetrate the mucus layer and directly interact with stroma components including fibroblasts and myofibroblasts. These cells, which are the source of biophysical and biochemical signals providing the proper balance between cell proliferation and differentiation within gastric epithelial stem cell compartment, when exposed to Hp, can convert into cancer-associated fibroblast (CAF) phenotype. The crosstalk between fibroblasts and myofibroblasts with gastric epithelial cells including stem/progenitor cell niche involves several pathways mediated by non-coding RNAs, Wnt, BMP, TGF-β, and Notch signaling ligands. The current review concentrates on the consequences of Hp-induced increase in gastric fibroblast and myofibroblast number, and their activation towards CAFs with the emphasis to the altered communication between mesenchymal and epithelial cell compartment, which may lead to inflammation, epithelial stem cell overproliferation, disturbed differentiation, and gradual gastric cancer development. Thus, Hp-activated fibroblasts may constitute the target for anti-cancer treatment and, importantly, for the pharmacotherapies diminishing their activation particularly at the early stages of Hp infection.

Fibulin-1 Regulates Initiation of Successional Dental Lamina

In humans, teeth are replaced only once, and the successional dental lamina (SDL) of the permanent tooth is maintained in a quiescent state until adolescence. Recently, we showed that biomechanical stress generated by the rapid growth of the deciduous tooth inhibits SDL development via integrin β1-RUNX2 signaling at embryonic day 60 (E60) in miniature pigs. However, the mechanism by which RUNX2 regulates SDL initiation within the SDL stem cell niche remains unclear. In the current study, we transcriptionally profiled single cells from SDL and surrounding mesenchyme at E60 and identified the landscape of cellular heterogeneity. We then identified a specific fibroblast subtype in the dental follicle mesenchyme between the deciduous tooth and the SDL of the permanent tooth (DFDP), which constitutes the inner part of the niche (deciduous tooth side). Compared with traditional dental follicle cells, the specific expression profile of DFDP was identified and found to be related to biomechanical stress. Subsequently, we found that RUNX2 could bind to the enhancer regions of Fbln1 (gene of fibulin-1), one of the marker genes for DFDP. Through gain- and loss-of-function experiments, we proved that the biomechanical stress-mediated RUNX2-fibulin-1 axis inhibits the initiation of SDL by maintaining SDL niche homeostasis.

Cellular and molecular mechanisms of Hedgehog signalling

The Hedgehog signalling pathway has crucial roles in embryonic tissue patterning, postembryonic tissue regeneration, and cancer, yet aspects of Hedgehog signal transmission and reception have until recently remained unclear. Biochemical and structural studies surprisingly reveal a central role for lipids in Hedgehog signalling. The signal - Hedgehog protein - is modified by cholesterol and palmitate during its biogenesis, thereby necessitating specialized proteins such as the transporter Dispatched and several lipid-binding carriers for cellular export and receptor engagement. Additional lipid transactions mediate response to the Hedgehog signal, including sterol activation of the transducer Smoothened. Access of sterols to Smoothened is regulated by the apparent sterol transporter and Hedgehog receptor Patched, whose activity is blocked by Hedgehog binding. Alongside these lipid-centric mechanisms and their relevance to pharmacological pathway modulation, we discuss emerging roles of Hedgehog pathway activity in stem cells or their cellular niches, with translational implications for regeneration and restoration of injured or diseased tissues.

What's old is new again: The anatomical studies of Franklin P. Mall and the fascial-interstitial spaces

Franklin Mall was one of the foremost scientists of the turn of the 19th century, an exemplary mentor as well as researcher, and his revolutionary contributions are still relevant today. Mall's early training in Leipzig with Wilhelm His and Carl Ludwig provided him with an unusual perspective on the integration of anatomy and physiology, and his interest in the links between structure and function guided the work he carried out after joining the faculty of the new Johns Hopkins University School of Medicine. Mall carried out innovative studies on the one hand using dye injection to trace blood and lymphatic supplies to different organs and on the other hand using "putrefaction" to digest tissues and study the organization of the reticular space, demonstrating that it was the underlying source of support for all the organs. These two studies of Mall's, carried out independently, provide the basis for modern studies integrating the understanding of fascia and interstitial spaces.

Reduced smooth muscle-fibroblasts transformation potentially decreases intestinal wound healing and colitis-associated cancer in ageing mice

Cancer and impaired tissue wound healing with ageing are closely related to the quality of life of the elderly population. Given the increased incidence of cancer and the population ageing trend globally, it is very important to explore how ageing impairs tissue wound healing and spontaneous cancer. In a murine model of DSS-induced acute colitis and AOM/DSS-induced colitis-associated cancer (CAC), we found ageing significantly decreases intestinal wound healing and simultaneous CAC initiation, although ageing does not affect the incidence of AOM-induced, sporadic non-inflammatory CRC. Mechanistically, reduced fibroblasts were observed in the colitis microenvironment of ageing mice. Through conditional lineage tracing, an important source of fibroblasts potentially derived from intestinal smooth muscle cells (ISMCs) was identified orchestrating intestinal wound healing and CAC initiation in young mice. However, the number of transformed fibroblasts from ISMCs significantly decreased in ageing mice, accompanied by decreased intestinal wound healing and decreased CAC initiation. ISMCs-fibroblasts transformation in young mice and reduction of this transformation in ageing mice were also confirmed by ex-vivo intestinal muscular layer culture experiments. We further found that activation of YAP/TAZ in ISMCs is required for the transformation of ISMCs into fibroblasts. Meanwhile, the reduction of YAP/TAZ activation in ISMCs during intestinal wound healing was observed in ageing mice. Conditional knockdown of YAP/TAZ in ISMCs of young mice results in reduced fibroblasts in the colitis microenvironment, decreased intestinal wound healing and decreased CAC initiation, similar to the phenotype of ageing mice. In addition, the data from intestine samples derived from inflammatory bowel disease (IBD) patients show that activation of YAP/TAZ also occurs in ISMCs from these patients. Collectively, our work reveals an important role of the ageing stromal microenvironment in intestinal wound healing and CAC initiation. Furthermore, our work also identified a potential source of fibroblasts involved in colitis and CAC.

Sensory nerve niche regulates mesenchymal stem cell homeostasis via FGF/mTOR/autophagy axis

Mesenchymal stem cells (MSCs) reside in microenvironments, referred to as niches, which provide structural support and molecular signals. Sensory nerves are niche components in the homeostasis of tissues such as skin, bone marrow and hematopoietic system. However, how the sensory nerve affects the behavior of MSCs remains largely unknown. Here we show that the sensory nerve is vital for mesenchymal tissue homeostasis and maintenance of MSCs in the continuously growing adult mouse incisor. Loss of sensory innervation leads to mesenchymal disorder and a decrease in MSCs. Mechanistically, FGF1 from the sensory nerve directly acts on MSCs by binding to FGFR1 and activates the mTOR/autophagy axis to sustain MSCs. Modulation of mTOR/autophagy restores the MSCs and rescues the mesenchymal tissue disorder of Fgfr1 mutant mice. Collectively, our study provides insights into the role of sensory nerves in the regulation of MSC homeostasis and the mechanism governing it.

Distinct niche structures and intrinsic programs of fallopian tube and ovarian surface epithelial cells

Epithelial ovarian cancer (EOC) can originate from either fallopian tube epithelial (FTE) or ovarian surface epithelial (OSE) cells, but with different latencies and disease outcomes. To address the basis of these differences, we performed single cell RNA-sequencing of mouse cells isolated from the distal half of fallopian tube (FT) and surface layer of ovary. We find at the molecular level, FTE secretory stem/progenitor cells and OSE cells resemble mammary luminal progenitors and basal cells, respectively. An FT stromal subpopulation, enriched with Pdgfra ⁺ and Esr1 ⁺ cells, expresses multiple secreted factor (e.g., IGF1) and Hedgehog pathway genes and may serve as a niche for FTE cells. In contrast, Lgr5 ⁺ OSE cells express similar genes largely by themselves, raising a possibility that they serve as their own niche. The differences in intrinsic expression programs and niche organizations of FTE and OSE cells may contribute to their different courses toward the development of EOCs.

The hedgehog pathway in hematopoiesis and hematological malignancy

The Hedgehog (HH) pathway is a promising therapeutic target in hematological malignancies. Activation of the pathway has been tied to greater chances of relapse and poorer outcomes in several hematological malignancies and inhibiting the pathway has improved outcomes in several clinical trials. One inhibitor targeting the pathway via the protein Smoothened (SMO), glasdegib, has been approved by the FDA for use with a low dose cytarabine regiment in some high-risk acute myeloid leukemia patients (AML). If further clinical trials in glasdegib produce positive results, there may soon be more general use of HH inhibitors in the treatment of hematological malignancies.While there is clinical evidence that HH inhibitors may improve outcomes and help prevent relapse, a full understanding of any mechanism of action remains elusive. The bulk of AML cells exhibit primary resistance to SMO inhibition (SMOi), leading some to hypothesize that that clinical activity of SMOi is mediated through modulation of self-renewal and chemoresistance in rare cancer stem cells (CSC). Direct evidence that CSC are being targeted in patients by SMOi has proven difficult to produce, and here we present data to support the alternative hypothesis that suggests the clinical benefit observed with SMOi is being mediated through stromal cells in the tumor microenvironment.This paper's aims are to review the history of the HH pathway in hematopoiesis and hematological malignancy, to highlight the pre-clinical and clinical evidence for its use a therapeutic target, and to explore the evidence for stromal activation of the pathway acting to protect CSCs and enable self-renewal of AML and other diseases. Finally, we highlight gaps in the current data and present hypotheses for new research directions.

Canonical Hedgehog Pathway and Noncanonical GLI Transcription Factor Activation in Cancer

The Hedgehog signaling pathway is one of the fundamental pathways required for development and regulation of postnatal regeneration in a variety of tissues. The pathway has also been associated with cancers since the identification of a mutation in one of its components, PTCH, as the cause of Basal Cell Nevus Syndrome, which is associated with several cancers. Our understanding of the pathway in tumorigenesis has expanded greatly since that initial discovery over two decades ago. The pathway has tumor-suppressive and oncogenic functions depending on the context of the cancer. Furthermore, noncanonical activation of GLI transcription factors has been reported in a number of tumor types. Here, we review the roles of canonical Hedgehog signaling pathway and noncanonical GLI activation in cancers, particularly epithelial cancers, and discuss an emerging concept of the distinct outcomes that these modes have on cancer initiation and progression.

Long-Noncoding RNA ANCR Activates the Hedgehog Signaling Pathway to Promote Basal Cell Carcinoma Progression by Binding to PTCH

Purpose

The long non-coding RNA (lncRNA) anti-differentiation noncoding RNA (ANCR) is closely related to the occurrence and development of various malignancies. However, its expression and potential role in basal cell carcinoma (BCC) have not been established. In this study, we characterized the effects of ANCR in BCC and its underlying mechanism.

Methods

The expression of ANCR in BCC tissues and cells was detected by qRT-PCR. Proliferation, invasion, migration and apoptosis of ANCR overexpressed or knock down TE354.T and A431 cells were examined by CCK8, transwell assay, wound healing assay and flow cytometry analysis, respectively. Western blot was performed to measure the expression of apoptosis-related proteins (BAX, BCL2 and Cleaved-caspase3), epithelial-mesenchymal transformation-related proteins (E-cadherin, N-cadherin, vimentin and β-catenin), and Hedgehog-pathway-related proteins (PTCH, GLI1 and SMO). RNA pull-down assay was used to analyze the relationship between ANCR and PTCH. The effect of ANCR on BCC growth in vivo was analyzed using xenograft model. TUNEL assay was used to determine the cell apoptosis.

Results

ANCR and Hedgehog pathway were more highly expressed in BCC tissues than in adjacent normal tissues. ANCR overexpression substantially promoted BCC cell proliferation, invasion, and migration, inhibited apoptosis, and up-regulated BCL2 and decreased the expression of BAX and Cleaved-caspase3 proteins. Additionally, the upregulation of N-cadherin, vimentin, β-catenin, PTCH, GLI1, and SMO expression, and downregulation of E-cadherin expression were observed after ANCR overexpression. Moreover, ANCR knockdown had the opposite effects. An RNA pull-down assay further revealed that ANCR is specifically bound to PTCH. In vivo experiments also showed that ANCR overexpression significantly increased tumor growth and decreased apoptosis, which was reversed by cyclopamine, a specific inhibitor of the Hedgehog signaling pathway.

Conclusion

ANCR activates the Hedgehog signaling pathway by binding to PTCH, thereby promoting BCC progression; accordingly, ANCR could be a candidate therapeutic target in BCC.

Cancer-Associated Fibroblasts Regulate Kinase Activity in Mesothelioma Cell Lines via Paracrine Signaling and Thereby Dictate Cell Faith and Behavior

BACKGROUND

Malignant pleural mesothelioma (MPM) has an infaust prognosis due to resistance to systemic treatment with platin-analoga. MPM cells modulate the immune response to their benefit. They release proinflammatory cytokines, such as TGF-ß, awakening resting fibrocytes that switch their phenotype into activated fibroblasts. Signaling interactions between cancer cells and cancer-associated fibroblasts (CAFs) play an integral part in tumor progression. This study aimed to investigate the role CAFs play in MPM progression, analyzing the impact this complex, symbiotic interaction has on kinase-related cell signaling in vitro.

METHODS

We simulated paracrine signaling in vitro by treating MPM cell lines with conditioned medium (CM) from fibroblasts (FB) and vice versa. NCI-H2052, MSTO-211H, and NCI-H2452 cell lines representing the three mayor MPM subtypes, while embryonal myofibroblast cell lines, IMR-90 and MRC-5, provide a CAFs-like phenotype. Subsequently, differences in proliferation rates, migratory behavior, apoptosis, necrosis, and viability were used as covariates for data analysis. Kinase activity of treated samples and corresponding controls were then analyzed using the PamStation12 platform (PamGene); Results: Treatment with myofibroblast-derived CM revealed significant changes in phosphorylation patterns in MPM cell lines. The observed effect differs strongly between the analyzed MPM cell lines and depends on the origin of CM. Overall, a much stronger effect was observed using CM derived from IMR-90 than MRC-5. The phosphorylation changes mainly affected the MAPK signaling pathway.; Conclusions: The factors secreted by myofibroblasts in fibroblasts CM significantly influence the phosphorylation of kinases, mainly affecting the MAPK signaling cascade in tested MPM cell lines. Our in vitro results indicate promising therapeutic effects by the use of MEK or ERK inhibitors and might have synergistic effects in combination with cisplatin-based treatment, improving clinical outcomes for MPM patients.

The cancer-inhibitory effects of proliferating tumor-residing fibroblasts

Initiation, local progression, and metastasis of cancer are associated with specific morphological, molecular, and functional changes in the extracellular matrix and the fibroblasts within the tumor microenvironment (TME). In the early stages of tumor development, fibroblasts are an obstacle that cancer cells must surpass or nullify to progress. Thus, in early tumor progression, specific signaling from cancer cells activates bio-pathways, which abolish the innate anticancer properties of fibroblasts and convert a high proportion of them to tumor-promoting cancer-associated fibroblasts (CAFs). Following this initial event, a wide spectrum of gene expression changes gradually leads to the development of a stromal fibroblast population with complex heterogeneity, creating fibroblast subtypes with characteristic profiles, which may alternate between being tumor-promotive and tumor-suppressive, topologically and chronologically in the TME. These fibroblast subtypes form the tumor's histological landscape including areas of cancer growth, inflammation, angiogenesis, invasion fronts, proliferating and non-proliferating fibroblasts, cancer-cell apoptosis, fibroblast apoptosis, and necrosis. These features reflect general deregulation of tissue homeostasis within the TME. This review discusses fundamental and current knowledge that has established the existence of anticancer fibroblasts within the various interacting elements of the TME. It is proposed that the maintenance of fibroblast proliferation is an essential parameter for the activation of their anticancer capacity, similar to that by which normal fibroblasts would be activated in wound repair, thus maintaining tissue homeostasis. Encouragement of research in this direction may render new means of cancer therapy and a greater understanding of tumor progression.

Proteomics as a Complementary Technique to Characterize Bladder Cancer

Simple Summary

Although immunohistochemistry is a routine technique in clinics, and genomics has been rapidly incorporated, proteomics is a step behind. This general situation is also the norm in bladder cancer research. This review shows the contributions of proteomics to the molecular classification of bladder cancer, and to the study of histopathology due to tissue insults caused by tumors. Furthermore, the importance of proteomics for understanding the cellular and molecular changes as a consequence of the therapy of bladder cancer cannot be neglected.

Abstract

Bladder cancer (BC) is the most common tumor of the urinary tract and is conventionally classified as either non-muscle invasive or muscle invasive. In addition, histological variants exist, as organized by the WHO-2016 classification. However, innovations in next-generation sequencing have led to molecular classifications of BC. These innovations have also allowed for the tracing of major tumorigenic pathways and, therefore, are positioned as strong supporters of precision medicine. In parallel, immunohistochemistry is still the clinical reference to discriminate histological layers and to stage BC. Key contributions have been made to enlarge the panel of protein immunomarkers. Moreover, the analysis of proteins in liquid biopsy has also provided potential markers. Notwithstanding, their clinical adoption is still low, with very few approved tests. In this context, mass spectrometry-based proteomics has remained a step behind; hence, we aimed to develop them in the community. Herein, the authors introduce the epidemiology and the conventional classifications to review the molecular classification of BC, highlighting the contributions of proteomics. Then, the advances in mass spectrometry techniques focusing on maintaining the integrity of the biological structures are presented, a milestone for the emergence of histoproteomics. Within this field, the review then discusses selected proteins for the comprehension of the pathophysiological mechanisms of BC. Finally, because there is still insufficient knowledge, this review considers proteomics as an important source for the development of BC therapies.

Metastatic pancreatic cancer: Mechanisms and detection (Review)

Pancreatic cancer (PC) is a lethal malignancy. Its prevalence rate remains low but continues to grow each year. Among all stages of PC, metastatic PC is defined as late-stage (stage IV) PC and has an even higher fatality rate. Patients with PC do not have any specific clinical manifestations. Most cases are inoperable at the time-point of diagnosis. Prognosis is also poor even with curative-intent surgery. Complications during surgery, postoperative pancreatic fistula and recurrence with metastatic foci make the management of metastatic PC difficult. While extensive efforts were made to improve survival outcomes, further elucidation of the molecular mechanisms of metastasis poses a formidable challenge. The present review provided an overview of the mechanisms of metastatic PC, summarizing currently known signaling pathways (e.g. epithelial-mesenchymal transition, NF-κB and KRAS), imaging that may be utilized for early detection and biomarkers (e.g. carbohydrate antigen 19-9, prostate cancer-associated transcript-1, F-box/LRR-repeat protein 7 and tumor stroma), giving insight into promising therapeutic targets.

A resident stromal cell population actively restrains innate immune response in the propagation phase of colitis pathogenesis in mice

Inflammatory bowel disease (IBD) affects 0.3% of the global population, yet the etiology remains poorly understood. Anti-inflammation therapy has shown great success, but only 60% of patients with IBD benefit from it, indicating that new targets are needed. Here, we report the discovery of an intrinsic counter regulatory mechanism in colitis pathogenesis that may be targeted for IBD treatment. In response to microbial invasion, resident Vimentin⁺ stromal cells, connective tissue cells genetically marked by Twist2, are activated during the propagation phase of the disease, but not during initiation and resolution phases, and become a primary source of prostaglandin E₂ (PGE₂). PGE₂ induction requires a nuclear factor κB-independent, TLR4-p38MAPK-Cox2 pathway activation. Ablation of each of the pathway genes, but not Rela or Tgfb1, in Twist2 cells enhanced M1 macrophage polarization and granulocyte/T helper 1 (T_H1)/T_H17 infiltration and aggravated colitis development. PGE₂ administration ameliorated colitis in mouse models with defective PGE₂ production but not in animals with normal PGE₂ induction. Analysis of clinical samples and public domain data revealed increased expression of Cox2, the rate-limiting enzyme of PGE₂ biosynthesis, in inflamed tissues, and especially in colon Vimentin⁺Twist2⁺ stromal cells, in about 60% of patients with active Crohn's disease or ulcerative colitis. Moreover, Cox2 protein expression was negatively correlated with disease severity, suggesting an involvement of stromal cells in IBD pathogenesis. Thus, the study uncovers an active immune pathway in colitic inflammation that may be targeted to treat patients with IBD with defects in PGE₂ production.

Tumour heterogeneity and evolutionary dynamics in colorectal cancer

Colorectal cancer (CRC) has a global burden of disease. Our current understanding of CRC has progressed from initial discoveries which focused on the stepwise accumulation of key driver mutations, as encapsulated in the Vogelstein model, to one in which marked heterogeneity leads to a complex interplay between clonal populations. Current evidence suggests that an initial explosion, or “Big Bang”, of genetic diversity is followed by a period of neutral dynamics. A thorough understanding of this interplay between clonal populations during neutral evolution gives insights into the roles in which driver genes may participate in the progress from normal colonic epithelium to adenoma and carcinoma. Recent advances have focused not only on genetics, transcriptomics, and proteomics but have also investigated the ecological and evolutionary processes which transform normal cells into cancer. This review first describes the role which driver mutations play in the Vogelstein model and subsequently demonstrates the evidence which supports a more complex model. This article also aims to underscore the significance of tumour heterogeneity and diverse clonal populations in cancer progression.

Hedgehog signaling and the primary cilium: implications for spatial and temporal constraints on signaling

The mechanisms of vertebrate Hedgehog signaling are linked to the biology of the primary cilium, an antenna-like organelle that projects from the surface of most vertebrate cell types. Although the advantages of restricting signal transduction to cilia are often noted, the constraints imposed are less frequently considered, and yet they are central to how Hedgehog signaling operates in developing tissues. In this Review, we synthesize current understanding of Hedgehog signal transduction, ligand secretion and transport, and cilia dynamics to explore the temporal and spatial constraints imposed by the primary cilium on Hedgehog signaling in vivo.

Smoothened transduces Hedgehog signals via activity-dependent sequestration of PKA catalytic subunits

The Hedgehog (Hh) pathway is essential for organ development, homeostasis, and regeneration. Dysfunction of this cascade drives several cancers. To control expression of pathway target genes, the G protein-coupled receptor (GPCR) Smoothened (SMO) activates glioma-associated (GLI) transcription factors via an unknown mechanism. Here, we show that, rather than conforming to traditional GPCR signaling paradigms, SMO activates GLI by binding and sequestering protein kinase A (PKA) catalytic subunits at the membrane. This sequestration, triggered by GPCR kinase (GRK)-mediated phosphorylation of SMO intracellular domains, prevents PKA from phosphorylating soluble substrates, releasing GLI from PKA-mediated inhibition. Our work provides a mechanism directly linking Hh signal transduction at the membrane to GLI transcription in the nucleus. This process is more fundamentally similar between species than prevailing hypotheses suggest. The mechanism described here may apply broadly to other GPCR- and PKA-containing cascades in diverse areas of biology.

Portrait of Cancer Stem Cells on Colorectal Cancer: Molecular Biomarkers, Signaling Pathways and miRNAome

Colorectal cancer (CRC) is a leading cause of cancer death worldwide, and about 20% is metastatic at diagnosis and untreatable. Increasing evidence suggests that the heterogeneous nature of CRC is related to colorectal cancer stem cells (CCSCs), a small cells population with stemness behaviors and responsible for tumor progression, recurrence, and therapy resistance. Growing knowledge of stem cells (SCs) biology has rapidly improved uncovering the molecular mechanisms and possible crosstalk/feedback loops between signaling pathways that directly influence intestinal homeostasis and tumorigenesis. The generation of CCSCs is probably connected to genetic changes in members of signaling pathways, which control self-renewal and pluripotency in SCs and then establish function and phenotype of CCSCs. Particularly, various deregulated CCSC-related miRNAs have been reported to modulate stemness features, controlling CCSCs functions such as regulation of cell cycle genes expression, epithelial-mesenchymal transition, metastasization, and drug-resistance mechanisms. Primarily, CCSC-related miRNAs work by regulating mainly signal pathways known to be involved in CCSCs biology. This review intends to summarize the epigenetic findings linked to miRNAome in the maintenance and regulation of CCSCs, including their relationships with different signaling pathways, which should help to identify specific diagnostic, prognostic, and predictive biomarkers for CRC, but also develop innovative CCSCs-targeted therapies.

Cancer-Associated Fibroblasts Suppress Cancer Development: The Other Side of the Coin

Cancer-associated fibroblasts (CAFs) are the main stromal components of cancer, representing a group of heterogeneous cells. Many studies indicate that CAFs promote tumor development. Besides, evidence of the tumor suppression effects of CAFs keeps on merging. In the tumor microenvironment, multiple stimuli can activate fibroblasts. Notably, this does not necessarily mean the activated CAFs become strong tumor promoters immediately. The varying degree of CAFs activation makes quiescent CAFs, tumor-restraining CAFs, and tumor-promoting CAFs. Quiescent CAFs and tumor-restraining CAFs are more present in early-stage cancer, while comparatively, more tumor-promoting CAFs present in advanced-stage cancer. The underlying mechanism that balances tumor promotion or tumor inhibition effects of CAFs is mostly unknown. This review focus on the inhibitory effects of CAFs on cancer development. We describe the heterogeneous origin, markers, and metabolism in the CAFs population. Transgenetic mouse models that deplete CAFs or deplete CAFs activation signaling in the tumor stroma present direct evidence of CAFs protective effects against cancer. Moreover, we outline CAFs subpopulation and CAFs derived soluble factors that act as a tumor suppressor. Single-cell RNA-sequencing on CAFs population provides us new insight to classify CAFs subsets. Understanding the full picture of CAFs will help translate CAFs biology from bench to bedside and develop new strategies to improve precision cancer therapy.

The Role of the Microenvironment and Immune System in Regulating Stem Cell Fate in Cancer

Despite gains in knowledge of the intrinsic signals governing cancer progression, effective clinical management of cancer remains a challenge. Drug resistance and relapse, pose the greatest barriers to cancer care, and are often driven by the co-option of stem cell programs by subpopulations of aggressive cancer cells. Here, we focus on the role of the microenvironment in the acquisition and/ or maintenance of stem cell states in cancer in the context of resistance and metastasis. We further discuss the role of cancer stem cells in immune evasion through the course of metastasis, dormancy, and relapse. Understanding the niche in which cancer stem cells live and the signals that sustain them may lead to new strategies that target them by disrupting microenvironmental support.

Rapid bioprinting of conjunctival stem cell micro-constructs for subconjunctival ocular injection

Ocular surface diseases including conjunctival disorders are multifactorial progressive conditions that can severely affect vision and quality of life. In recent years, stem cell therapies based on conjunctival stem cells (CjSCs) have become a potential solution for treating ocular surface diseases. However, neither an efficient culture of CjSCs nor the development of a minimally invasive ocular surface CjSC transplantation therapy has been reported. Here, we developed a robust in vitro expansion method for primary rabbit-derived CjSCs and applied digital light processing (DLP)-based bioprinting to produce CjSC-loaded hydrogel micro-constructs for injectable delivery. Expansion medium containing small molecule cocktail generated fast dividing and highly homogenous CjSCs for more than 10 passages in feeder-free culture. Bioprinted hydrogel micro-constructs with tunable mechanical properties enabled the 3D culture of CjSCs while supporting viability, stem cell phenotype, and differentiation potency into conjunctival goblet cells. These hydrogel micro-constructs were well-suited for scalable dynamic suspension culture of CjSCs and were successfully delivered to the bulbar conjunctival epithelium via minimally invasive subconjunctival injection. This work integrates novel cell culture strategies with bioprinting to develop a clinically relevant injectable-delivery approach for CjSCs towards the stem cell therapies for the treatment of ocular surface diseases.

Cancer Stem Cells in the Immune Microenvironment

Cancer stem cells are a subpopulation of cancer cells responsible for the most demanding and aggressive cancer cell phenotypes: therapy resistance, a self-protective feature of stem cells; distant metastasis, requiring anchorage independence for survival in the circulation; and recurrence, which is related to the dormant-active cycling of stem cells. Normal tissues are composed of parenchymal cells, supportive connective components, and cellular disposal systems for removing the products of physiological wear and tear. Cancer stem cells develop from normal counterparts and progressively interact with their microenvironments, modifying and conditioning the cancer microenvironment. Cancer-associated myeloid cells constitute a major element of the cancer microenvironment. During the process of carcinogenesis, cancer stem cells and their intimately associated myeloid cells mutually interact and evolve, such that the cancer cells potentiate the activity of the myeloid cells and, in return, the myeloid cells increase cancer stem cell characteristics. Normal myeloid cells function as key accessory cells to maintain homeostasis in normal tissues and organs; in cancers, these cells co-evolve with the malignant parenchymal cells and are involved in every aspect of cancer cell biology, including proliferation, invasion, distant metastasis, and the development of resistance to therapy. In this way, cancer-associated myeloid cells provide two of the key hallmarks of cancer: evasion of immune destruction and cancer-promoting inflammation.

Hedgehog produced by the Drosophila wing imaginal disc induces distinct responses in three target tissues

Hedgehog (Hh) is an evolutionarily conserved signaling protein that has essential roles in animal development and homeostasis. We investigated Hh signaling in the region of the Drosophila wing imaginal disc that produces Hh and is near the tracheal air sac primordium (ASP) and myoblasts. Hh distributes in concentration gradients in the anterior compartment of the wing disc, ASP and myoblasts, and activates genes in each tissue. Some targets of Hh signal transduction are common to the disc, ASP and myoblasts, whereas others are tissue-specific. Signaling in the three tissues is cytoneme-mediated and cytoneme-dependent. Some ASP cells project cytonemes that receive both Hh and Branchless (Bnl), and some targets regulated by Hh signaling in the ASP are also dependent on Bnl signal transduction. We conclude that the single source of Hh in the wing disc regulates cell type-specific responses in three discreet target tissues.

Hedgehog pathway activation through nanobody-mediated conformational blockade of the Patched sterol conduit

Activation of the Hedgehog pathway may have therapeutic value for improved bone healing, taste receptor cell regeneration, and alleviation of colitis or other conditions. Systemic pathway activation, however, may be detrimental, and agents amenable to tissue targeting for therapeutic application have been lacking. We have developed an agonist, a conformation-specific nanobody against the Hedgehog receptor Patched1 (PTCH1). This nanobody potently activates the Hedgehog pathway in vitro and in vivo by stabilizing an alternative conformation of a Patched1 "switch helix," as revealed by our cryogenic electron microscopy structure. Nanobody-binding likely traps Patched in one stage of its transport cycle, thus preventing substrate movement through the Patched1 sterol conduit. Unlike the native Hedgehog ligand, this nanobody does not require lipid modifications for its activity, facilitating mechanistic studies of Hedgehog pathway activation and the engineering of pathway activating agents for therapeutic use. Our conformation-selective nanobody approach may be generally applicable to the study of other PTCH1 homologs.

Biopolymer Hydrogel Scaffold as an Artificial Cell Niche for Mesenchymal Stem Cells

The activity of stem cell processes is regulated by internal and external signals of the cell "niche". In general, the niche of stem cells can be represented as the microenvironment of the cells, providing a signal complex, determining the properties of the cells. At the same time, the "niche" concept implies feedback. Cells can modify their microenvironment, supporting homeostasis or remodeling the composition and structure of the extracellular matrix. To ensure the regenerative potential of tissue engineering products the "niche" concept should be taken into account. To investigate interactions in an experimental niche, an original hydrogel biopolymer scaffold with encapsulated mesenchymal adipose-derived stem cells (ASCs) was used in this study. The scaffold provides for cell adhesion, active cell growth, and proliferative activity. Cells cultured within a scaffold are distinguished by the presence of a developed cytoskeleton and they form a cellular network. ASCs cultured within a scaffold change their microenvironment by secreting VEGF-A and remodeling the scaffold structure. Scaffold biodegradation processes were evaluated after previous culturing of the ASCs in the scaffolds for periods of either 24 h or six days. The revealed differences confirmed that changes had occurred in the properties of scaffolds remodeled by cells during cultivation. The mechanisms of the identified changes and the possibility of considering the presented scaffold as an appropriate artificial niche for ASCs are discussed.

Stroma-Targeting Therapy in Pancreatic Cancer: One Coin With Two Sides?

Pancreatic ductal adenocarcinoma (PDAC) is a malignancy with one of the worst prognoses worldwide and has an overall 5-year survival rate of only 9%. Although chemotherapy is the recommended treatment for patients with advanced PDAC, its efficacy is not satisfactory. The dense dysplastic stroma of PDAC is a major obstacle to the delivery of chemotherapy drugs and plays an important role in the progression of PDAC. Therefore, stroma-targeting therapy is considered a potential treatment strategy to improve the efficacy of chemotherapy and patient survival. While several preclinical studies have shown encouraging results, the anti-tumor potential of the PDAC stroma has also been revealed, and the extreme depletion might promote tumor progression and undermine patient survival. Therefore, achieving a balance between stromal abundance and depletion might be the further of stroma-targeting therapy. This review summarized the current progress of stroma-targeting therapy in PDAC and discussed the double-edged sword of its therapeutic effects.

Fibroblasts direct differentiation of human breast epithelial progenitors

BACKGROUND

Breast cancer arises within specific regions in the human breast referred to as the terminal duct lobular units (TDLUs). These are relatively dynamic structures characterized by sex hormone driven cyclic epithelial turnover. TDLUs consist of unique parenchymal entities embedded within a fibroblast-rich lobular stroma. Here, we established and characterized a new human breast lobular fibroblast cell line against its interlobular counterpart with a view to assessing the role of region-specific stromal cues in the control of TDLU dynamics.

METHODS

Primary lobular and interlobular fibroblasts were transduced to express human telomerase reverse transcriptase (hTERT). Differentiation of the established cell lines along lobular and interlobular pathways was determined by immunocytochemical staining and genome-wide RNA sequencing. Their functional properties were further characterized by analysis of mesenchymal stem cell (MSC) differentiation repertoire in culture and in vivo. The cells' physiological relevance for parenchymal differentiation was examined in heterotypic co-culture with fluorescence-activated cell sorting (FACS)-purified normal breast primary luminal or myoepithelial progenitors. The co-cultures were immunostained for quantitative assessment of epithelial branching morphogenesis, polarization, growth, and luminal epithelial maturation. In extension, myoepithelial progenitors were tested for luminal differentiation capacity in culture and in mouse xenografts. To unravel the significance of transforming growth factor-beta (TGF-β)-mediated crosstalk in TDLU-like morphogenesis and differentiation, fibroblasts were incubated with the TGF-β signaling inhibitor, SB431542, prior to heterotypic co-culture with luminal cells.

RESULTS

hTERT immortalized fibroblast cell lines retained critical phenotypic traits in culture and linked to primary fibroblasts. Cell culture assays and transplantation to mice showed that the origin of fibroblasts determines TDLU-like and ductal-like differentiation of epithelial progenitors. Whereas lobular fibroblasts supported a high level of branching morphogenesis by luminal cells, interlobular fibroblasts supported ductal-like myoepithelial characteristics. TDLU-like morphogenesis, at least in part, relied on intact TGF-β signaling.

CONCLUSIONS

The significance of the most prominent cell type in normal breast stroma, the fibroblast, in directing epithelial differentiation is largely unknown. Through establishment of lobular and interlobular fibroblast cell lines, we here demonstrate that epithelial progenitors are submitted to stromal cues for site-specific differentiation. Our findings lend credence to considering stromal subtleties of crucial importance in the development of normal breast and, in turn, breast cancer.

Prostaglandin E1 Inhibits GLI2 Amplification-Associated Activation of the Hedgehog Pathway and Drug Refractory Tumor Growth

Aberrant activation of the Hedgehog (HH) signaling pathway underlines the initiation and progression of a multitude of cancers. The effectiveness of the leading drugs vismodegib (GDC-0449) and sonidegib (LDE225), both Smoothened (SMO) antagonists, is compromised by acquisition of mutations that alter pathway components, notably secondary mutations in SMO and amplification of GLI2, a transcriptional mediator at the end of the pathway. Pharmacologic blockade of GLI2 activity could ultimately overcome these diversified refractory mechanisms, which would also be effective in a broader spectrum of primary tumors than current SMO antagonists. To this end, we conducted a high-content screening directly analyzing the ciliary translocation of GLI2, a key event for GLI2 activation in HH signal transduction. Several prostaglandin compounds were shown to inhibit accumulation of GLI2 within the primary cilium (PC). In particular, prostaglandin E1 (PGE1), an FDA-approved drug, is a potent GLI2 antagonist that overcame resistance mechanisms of both SMO mutagenesis and GLI2 amplification. Consistent with a role in HH pathway regulation, EP4 receptor localized to the PC. Mechanistically, PGE1 inhibited HH signaling through the EP4 receptor, enhancing cAMP-PKA activity, which promoted phosphorylation and degradation of GLI2 via the ubiquitination pathway. PGE1 also effectively inhibited the growth of drug refractory human medulloblastoma xenografts. Together, these results identify PGE1 and other prostaglandins as potential templates for complementary therapeutic development to circumvent resistance to current generation SMO antagonists in use in the clinic. SIGNIFICANCE: These findings show that PGE1 exhibits pan-inhibition against multiple drug refractory activities for Hedgehog-targeted therapies and elicits significant antitumor effects in xenograft models of drug refractory human medulloblastoma mimicking GLI2 amplification.

Adult Pancreatic Acinar Progenitor-like Populations in Regeneration and Cancer

The bulk of the pancreas primarily comprises long-lived acinar cells that are not considered a bona fide source for stem cells. However, certain acinar subpopulations have a repopulating capacity during regeneration, raising the hypothesis as to the presence of regenerative progenitor-like populations in the adult pancreas. Here, we describe recent discoveries based on fate-mapping techniques that support the existence of progenitor-like acinar subpopulations, including active progenitor-like cells that maintain tissue homeostasis and facultative progenitor-like cells that drive tissue regeneration. A possible link between progenitor-like acinar cells and cancer initiators is proposed. Further analysis of these cellular components is needed, because it would help uncover possible cellular sources for regeneration and cancer, as well as potential targets for therapy.

The life cycle of cancer-associated fibroblasts within the tumour stroma and its importance in disease outcome

The tumour microenvironment (TME) determines vital aspects of tumour development, such as tumour growth, metastases and response to therapy. Cancer-associated fibroblasts (CAFs) are abundant and extremely influential in this process and interact with cellular and matrix TME constituents such as endothelial and immune cells and collagens, fibronectin and elastin, respectively. However, CAFs are also the recipients of signals—both chemical and physical—that are generated by the TME, and their phenotype effectively evolves alongside the tumour mass during tumour progression. Amid a rising clinical interest in CAFs as a crucial force for disease progression, this review aims to contextualise the CAF phenotype using the chronological framework of the CAF life cycle within the evolving tumour stroma, ranging from quiescent fibroblasts to highly proliferative and secretory CAFs. The emergence, properties and clinical implications of CAF activation are discussed, as well as research strategies used to characterise CAFs and current clinical efforts to alter CAF function as a therapeutic strategy.

Loss of androgen signaling in mesenchymal sonic hedgehog responsive cells diminishes prostate development, growth, and regeneration

Prostate embryonic development, pubertal and adult growth, maintenance, and regeneration are regulated through androgen signaling-mediated mesenchymal-epithelial interactions. Specifically, the essential role of mesenchymal androgen signaling in the development of prostate epithelium has been observed for over 30 years. However, the identity of the mesenchymal cells responsible for this paracrine regulation and related mechanisms are still unknown. Here, we provide the first demonstration of an indispensable role of the androgen receptor (AR) in sonic hedgehog (SHH) responsive Gli1-expressing cells, in regulating prostate development, growth, and regeneration. Selective deletion of AR expression in Gli1-expressing cells during embryogenesis disrupts prostatic budding and impairs prostate development and formation. Tissue recombination assays showed that urogenital mesenchyme (UGM) containing AR-deficient mesenchymal Gli1-expressing cells combined with wildtype urogenital epithelium (UGE) failed to develop normal prostate tissue in the presence of androgens, revealing the decisive role of AR in mesenchymal SHH responsive cells in prostate development. Prepubescent deletion of AR expression in Gli1-expressing cells resulted in severe impairment of androgen-induced prostate growth and regeneration. RNA-sequencing analysis showed significant alterations in signaling pathways related to prostate development, stem cells, and organ morphogenesis in AR-deficient Gli1-expressing cells. Among these altered pathways, the transforming growth factor β1 (TGFβ1) pathway was up-regulated in AR-deficient Gli1-expressing cells. We further demonstrated the activation of TGFβ1 signaling in AR-deleted prostatic Gli1-expressing cells, which inhibits prostate epithelium growth through paracrine regulation. These data demonstrate a novel role of the AR in the Gli1-expressing cellular niche for regulating prostatic cell fate, morphogenesis, and renewal, and elucidate the mechanism by which mesenchymal androgen-signaling through SHH-responsive cells elicits the growth and regeneration of prostate epithelium.

Prostate formation, growth, and regeneration, as well as tumorigenesis, depend on androgens and androgen receptor (AR)-mediated signaling pathways. Tissue recombination assays done more than 30 years ago demonstrated a decisive role for stromal androgen signaling in prostatic epithelium development. However, in the intervening time, the identity of the mesenchymal cells in the urogenital sinus mesenchyme that convey androgen signaling and control prostate epithelium development, morphogenesis, and regeneration has not been determined. In this study, using mouse genetic tools, we demonstrate for the first time that selective deletion of AR in mesenchymal Gli1-expressing cells abolishes early development of prostate tissue and normal prostate formation, and diminishes prostate pubertal growth and regeneration. In addition, using tissue recombination assays, we directly determined an essential requirement for AR expression in mesenchymal Gli1-expressing cells during prostate epithelium development. Our results not only resolve a 30-year-old scientific puzzle by identifying the mesenchymal cell properties of androgen-responsive cells that elicit development of the embryonic prostate epithelium, but also explore a new regulatory mechanism for androgen and Shh signaling-mediated cellular niches in regulating prostatic cell fate, growth, and renewal through paracrine regulation. Given the importance of sex hormone and hedgehog signaling pathways in human development and tumorigenesis, this study extends beyond the field of prostate biology, raising new questions underlying sex hormone and SHH signaling in development and tumorigenesis.

Hedgehog pathway inhibition causes primary follicle atresia and decreases female germline stem cell proliferation capacity or stemness

Background

Follicle depletion is one of the causes of premature ovarian failure (POF) and primary ovarian insufficiency (POI). Hence, maintenance of a certain number of female germline stem cells (FGSCs) is optimal to produce oocytes and replenish the primordial follicle pool. The mechanism that regulates proliferation or stemness of FGSCs could contribute to restoring ovarian function, but it remains uncharacterized in postnatal mammalian ovaries. This study aims to investigate the mechanism by which inhibiting the activity of the hedgehog (Hh) signaling pathway regulates follicle development and FGSC proliferation.

Methods and results

To understand the role of the Hh pathway in ovarian aging, we measured Hh signaling activity at different reproductive ages and the correlation between them in physiological and pathological mice. Furthermore, we evaluated the follicle number and development and the changes in FGSC proliferation or stemness after blocking the Hh pathway in vitro and in vivo. In addition, we aimed to explain one of the mechanisms for the FGSC phenotype changes induced by treatment with the Hh pathway-specific inhibitor GANT61 via oxidative stress and apoptosis. The results show that the activity of Hh signaling is decreased in the ovaries in physiological aging and POF models, which is consistent with the trend of expression levels of the germline stem cell markers Mvh and Oct4. In vitro, blocking the Hh pathway causes follicular developmental disorders and depletes ovarian germ cells and FGSCs after treating ovaries with GANT61. The proliferation or stemness of cultured primary FGSCs is reduced when Hh activity is blocked. Our results show that the antioxidative enzyme level and the ratio of Bcl-2/Bax decrease, the expression level of caspase 3 increases, the mitochondrial membrane potential is abnormal, and ROS accumulate in this system.

Conclusions

We observed that the inhibition of the Hh signaling pathway with GANT61 could reduce primordial follicle number and decrease FGSC reproductive capacity or stemness through oxidative damage and apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1299-5) contains supplementary material, which is available to authorized users.

A Longitudinal Study of the Association between Mammographic Density and Gene Expression in Normal Breast Tissue

High mammographic density (MD) is associated with a 4-6 times increase in breast cancer risk. For post-menopausal women, MD often decreases over time, but little is known about the underlying biological mechanisms. MD reflects breast tissue composition, and may be associated with microenvironment subtypes previously identified in tumor-adjacent normal tissue. Currently, these subtypes have not been explored in normal breast tissue. We obtained biopsies from breasts of healthy women at two different time points several years apart and performed microarray gene expression analysis. At time point 1, 65 samples with both MD and gene expression were available. At time point 2, gene expression and MD data were available from 17 women, of which 11 also had gene expression data available from the first time point. We validated findings from our previous study; negative correlation between RBL1 and MD in post-menopausal women, indicating involvement of the TGFβ pathway. We also found that breast tissue samples from women with a large decrease in MD sustained higher expression of genes in the histone family H4. In addition, we explored the previously defined active and inactive microenvironment subtypes and demonstrated that normal breast samples of the active subtype had characteristics similar to the claudin-low breast cancer subtype. Breast biopsies from healthy women are challenging to obtain, but despite a limited sample size, we have identified possible mechanisms relevant for changes in breast biology and MD over time that may be of importance for breast cancer risk and tumor initiation.

Exosomes, metastases, and the miracle of cancer stem cell markers

Cancer-initiating cells (CIC) are the driving force in tumor progression. There is strong evidence that CIC fulfill this task via exosomes (TEX), which modulate and reprogram stroma, nontransformed cells, and non-CIC. Characterization of CIC, besides others, builds on expression of CIC markers, many of which are known as metastasis-associated molecules. We here discuss that the linkage between CIC/CIC-TEX and metastasis-associated molecules is not fortuitously, but relies on the contribution of these markers to TEX biogenesis including loading and TEX target interactions. In addition, CIC markers contribute to TEX binding- and uptake-promoted activation of signaling cascades, transcription initiation, and translational control. Our point of view will be outlined for pancreas and colon CIC highly expressing CD44v6, Tspan8, EPCAM, claudin7, and LGR5, which distinctly but coordinately contribute to tumor progression. Despite overwhelming progress in unraveling the metastatic cascade and the multiple tasks taken over by CIC-TEX, there remains a considerable gap in linking CIC biomarkers, TEX, and TEX-initiated target modulation with metastasis. We will try to outline possible bridges, which could allow depicting pathways for new and expectedly powerful therapeutic interference with tumor progression.

Collagen-rich airway smooth muscle cells are a metastatic niche for tumor colonization in the lung

Metastases account for the majority of cancer deaths. While certain steps of the metastatic cascade are well characterized, identification of targets to block this process remains a challenge. Host factors determining metastatic colonization to secondary organs are particularly important for exploration, as those might be shared among different cancer types. Here, we showed that bladder tumor cells expressing the collagen receptor, CD167a, responded to collagen I stimulation at the primary tumor to promote local invasion and utilized the same receptor to preferentially colonize at airway smooth muscle cells (ASMCs)—a rich source of collagen III in lung. Morphologically, COL3-CD167a-driven metastatic foci are uniquely distinct from typical lung alveolar metastatic lesions and exhibited activation of the CD167a-HSP90-Stat3 axis. Importantly, metastatic lung colonization could be abrogated using an investigational drug that attenuates Stat3 activity, implicating this seed-and-soil interaction as a therapeutic target for eliminating lung metastasis.

Collagen is a dynamic component of both the tumor and metastatic niche. Here, the authors show that airway smooth muscle cells are a collagen III rich niche bladder cancer cells expressing CD167a, and Stat3 is a downstream target for abrogating  these collagen III/CD167a-driven metastatic foci.

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.

Cancer-associated fibroblasts in gastrointestinal cancer

The tumour microenvironment, also termed the tumour stroma or tumour mesenchyme, includes fibroblasts, immune cells, blood vessels and the extracellular matrix and substantially influences the initiation, growth and dissemination of gastrointestinal cancer. Cancer-associated fibroblasts (CAFs) are one of the critical components of the tumour mesenchyme and not only provide physical support for epithelial cells but also are key functional regulators in cancer, promoting and retarding tumorigenesis in a context-dependent manner. In this Review, we outline the emerging understanding of gastrointestinal CAFs with a particular emphasis on their origin and heterogeneity, as well as their function in cancer cell proliferation, tumour immunity, angiogenesis, extracellular matrix remodelling and drug resistance. Moreover, we discuss the clinical implications of CAFs as biomarkers and potential targets for prevention and treatment of patients with gastrointestinal cancer.

Disparate cell proliferation and p53 overexpression in colonic crypts with normal epithelial lining found below the neoplastic canopy of conventional adenomas

We previously found colonic crypts with normal epithelial lining but with corrupted shapes (NECS) beneath the adenomatous tissue of conventional adenomas (CoAs). Here we assessed the distribution of proliferating cells (PCs) and explored the possible occurrence of p53‐upregulated cells in the NECS in a cohort of CoAs. Sections from 70 CoAs and from 12 normal colon segments were immunostained with the proliferation marker Ki67. In 60 of the 70 CoAs, additional sections were immunostained for the tumor suppressor p53 protein. NECS with asymmetric, haphazardly distributed single PC or PC clusters were recorded in 80% of the CoAs, with a continuous PC domain in one or both slopes of the crypts in 17%, and with haphazardly distributed single PCs in the remaining 3% of the CoAs. In the 12 normal segments (controls), the colon crypts demonstrated normal shapes with symmetric PC domains limited to the lower third portion of the crypts. In 30% of the 60 CoAs immunostained with p53 the NECS revealed haphazardly distributed p53‐upregulated cells, singly or in clusters. In sum, the apparently normal epithelium of the NECS beneath the adenomatous tissue of CoAs revealed an unprecedented relocation of the normal PC domains. This unexpected event and the occurrence of p53‐upregulated cells strongly suggest that the crypts beneath the neoplastic tissue of CoAs harbor somatic mutations. The accretion of putative mutated NECS beneath the neoplastic canopy of CoA emerges as a previously unaddressed major event, an event that might play an important role in the histogenesis of CoA in the human colon.

Reflections on depletion of tumor stroma in pancreatic cancer

Pancreatic cancer characteristically has an extremely dense stroma, which facilitates chemoresistance by creating physical and biological barriers to therapeutic agents. Thus, stroma-depleting agents may enhance the delivery and efficacy of chemotherapy drugs. However, stroma-targeting therapy for pancreatic cancer is a double-edged sword, as the stroma can also inhibit tumor metastasis and malignancy. In-depth understanding of the critical role of the stroma in cancer metastasis may improve therapeutic approaches by allowing them to harness specific features of the stroma to treat pancreatic cancer.

Immunoreactivity for prostate specific antigen and Ki67 differentiates subgroups of prostate cancer related to outcome

Based on gene-expression profiles, prostate tumors can be subdivided into subtypes with different aggressiveness and response to treatment. We investigated if similar clinically relevant subgroups can be identified simply by the combination of two immunohistochemistry markers: one for tumor cell differentiation (prostate specific antigen, PSA) and one for proliferation (Ki67). This was analyzed in men with prostate cancer diagnosed at transurethral resection of the prostate 1975-1991 (n = 331) where the majority was managed by watchful waiting. Ki67 and PSA immunoreactivity was related to outcome and to tumor characteristics previously associated with prognosis. Increased Ki67 and decreased PSA were associated with poor outcome, and they provided independent prognostic information from Gleason score. A combinatory score for PSA and Ki67 immunoreactivity was produced using the median PSA and Ki67 levels as cut-off (for Ki67 the upper quartile was also evaluated) for differentiation into subgroups. Patients with PSA low/Ki67 high tumors showed higher Gleason score, more advanced tumor stage, and higher risk of prostate cancer death compared to other patients. Their tumor epithelial cells were often ERG positive and expressed higher levels of ErbB2, phosphorylated epidermal growth factor receptor (pEGF-R) and protein kinase B (pAkt), and their tumor stroma showed a reactive response with type 2 macrophage infiltration, high density of blood vessels and hyaluronic acid, and with reduced levels of caveolin-1, androgen receptors, and mast cells. In contrast, men with PSA high/Ki67 low tumors were characterized by low Gleason score, and the most favorable outcome amongst PSA/Ki67-defined subgroups. Men with PSA low/Ki67 low tumors showed clinical and tumor characteristics intermediate of the two groups above. A combinatory PSA/Ki67 immunoreactivity score identifies subgroups of prostate cancers with different epithelial and stroma phenotypes and highly different outcome but the clinical usefulness of this approach needs to be validated in other cohorts.

Potential protective effect of ALDH-1 stromal expression against early recurrence of operable breast cancers

Background

The emerging cancer stem cell (CSC) model proposes that the stem cell niche plays a major role in the risk of cancer recurrence. Enzymatic activity of aldehydes, including aldehyde dehydrogenase 1 (ALDH-1), has been used as a marker of normal and malignant breast stem cells (BSCs). However, the clinical implications of the expression of stem cell markers in the stroma have not yet been investigated.

Methods

To determine the relationships of ALDH-1 expression, the currently reliable BSCs marker, with clinical characteristics and survival, we used immunohistochemical staining of tissue microarrays from 180 stroma and epithelial cancer tissues in patients diagnosed with operable early breast cancer (stage 0-III).

Results

ALDH-1 expression was observed in 93.4% of the stromal cells and in 37.2% of the epithelial cells, and the expression levels between the two cell types were significantly correlated (P=0.001). The stromal expression of ALDH-1 was not correlated with any clinical factors, whereas epithelial expression was significantly correlated with a negative estrogen-receptor status (P<0.001), high proliferation based on Ki-67 expression (P<0.001), and younger age (P=0.04). After 27.8 months of follow up, negative stromal expression of ALDH-1 was significantly correlated with shorter overall survival (positive, 56.9±3.0 months vs. negative, 30.5±3.0 months; P=0.01).

Conclusions

Stromal ALDH-1 expression was not directly correlated with known clinical factors, but its expression may play a protective role against early recurrence. Further observation and large-scale studies are needed to validate the clinical implications of ALDH-1 in breast cancer.

Signaling in the stem cell niche: regulating cell fate, function and plasticity

Stem cells have the ability to self-renew and differentiate along multiple lineages, driving tissue homeostasis and regeneration. Paradigms of unidirectional, hierarchical differentiation trajectories observed in embryonic and hematopoietic stem cells have traditionally been applied to tissue-resident stem cells. However, accumulating evidence implicates stemness as a bidirectional, dynamic state that is largely governed by the niche, which facilitates plasticity and adaptability to changing conditions. In this Review, we discuss mechanisms of cell fate regulation through niche-derived cues, with a particular focus on epithelial stem cells of the mammalian skin, intestine and lung. We discuss a spectrum of niche-derived biochemical, mechanical and architectural inputs that define stem cell states during morphogenesis, homeostasis and regeneration, and highlight how these diverse inputs influence stem cell plasticity.

Therapeutic developments in pancreatic cancer: current and future perspectives

The overall 5-year survival for pancreatic cancer has changed little over the past few decades, and pancreatic cancer is predicted to be the second leading cause of cancer-related mortality in the next decade in Western countries. The past few years, however, have seen improvements in first-line and second-line palliative therapies and considerable progress in increasing survival with adjuvant treatment. The use of biomarkers to help define treatment and the potential of neoadjuvant therapies also offer opportunities to improve outcomes. This Review brings together information on achievements to date, what is working currently and where successes are likely to be achieved in the future. Furthermore, we address the questions of how we should approach the development of pancreatic cancer treatments, including those for patients with metastatic, locally advanced and borderline resectable pancreatic cancer, as well as for patients with resected tumours. In addition to embracing newer strategies comprising genomics, stromal therapies and immunotherapies, conventional approaches using chemotherapy and radiotherapy still offer considerable prospects for greater traction and synergy with evolving concepts.