Cell density regulates cancer metastasis via the Hippo pathway

CCL2 signaling promotes skeletal muscle wasting in non-tumor and breast tumor models

Despite advancements in treatment, approximately 25% of patients with breast cancer experience long-term skeletal muscle wasting (SMW), which limits mobility, reduces drug tolerance and adversely impacts survival. By understanding the underlying molecular mechanisms of SMW, we may be able to develop new strategies to alleviate this condition and improve the lives of patients with breast cancer. Chemokines are small soluble factors that regulate homing of immune cells to tissues during inflammation. In breast cancers, overexpression of C-C chemokine ligand 2 (CCL2) correlates with unfavorable prognosis. Elevated levels of CCL2 in peripheral blood indicate possible systemic effects of this chemokine in patients with breast cancer. Here, we investigated the role of CCL2 signaling on SMW in tumor and non-tumor contexts. In vitro, increasing concentrations of CCL2 inhibited myoblast and myotube function through C-C chemokine receptor 2 (CCR2)-dependent mechanisms involving JNK, SMAD3 and AMPK signaling. In healthy mice, delivery of recombinant CCL2 protein promoted SMW in a dose-dependent manner. In vivo knockdown of breast tumor-derived CCL2 partially protected against SMW. Overall, chronic, upregulated CCL2-CCR2 signaling positively regulates SMW, with implications for therapeutic targeting.

Automatic diagnosis and classification of breast surgical samples with dynamic full-field OCT and machine learning

Purpose

The adoption of emerging imaging technologies in the medical community is often hampered when they provide a new unfamiliar contrast that requires experience to be interpreted. Dynamic full-field optical coherence tomography (D-FF-OCT) microscopy is such an emerging technique. It provides fast, high-resolution images of excised tissues with a contrast comparable to H&E histology but without any tissue preparation and alteration.

Approach

We designed and compared two machine learning approaches to support interpretation of D-FF-OCT images of breast surgical specimens and thus provide tools to facilitate medical adoption. We conducted a pilot study on 51 breast lumpectomy and mastectomy surgical specimens and more than 1000 individual 1.3 × 1.3    mm 2 images and compared with standard H&E histology diagnosis.

Results

Using our automatic diagnosis algorithms, we obtained an accuracy above 88% at the image level (1.3 × 1.3    mm 2 ) and above 96% at the specimen level (above cm 2 ).

Conclusions

Altogether, these results demonstrate the high potential of D-FF-OCT coupled to machine learning to provide a rapid, automatic, and accurate histopathology diagnosis with minimal sample alteration.

Cell density modulates chemoresistance in breast cancer cells through differential expression of ABC transporters

BACKGROUND

Breast cancer patients undergoing chemotherapy encounter a significant challenge of chemoresistance because of drug efflux by ATP-binding cassette (ABC) transporters. Breast cancer cell density alters considerably throughout the early stages of primary and secondary tumor development. Although cell density in culture influences kinetics, the effects of varying cell densities on the chemoresistance of breast cancer cells remains largely unexplored.

METHODS AND RESULTS

We observed chemotherapeutics-induced differential gene and protein expression of ABC transporters in luminal and basal breast cancer cells cultured at low and high seeding densities. Low-density cultures depicted a significant increase in the mRNA expression of ABC transporters-ABCG2, ABCG1, ABCC4, ABCA2, ABCA3, ABCC2, ABCC3, ABCC6, ABCC7, and ABCC9 as compared with high-density cultures. Next, cells at both low and high seeding densities when pre-treated with cyclosporine A (CsA), a pan-inhibitor of ABC transporters, resulted in increased sensitization to chemotherapeutics-doxorubicin and tamoxifen at markedly low IC50 concentrations suggesting the role of ABC transporters. Finally, markedly high doxorubicin-drug accumulation, significantly increased expression of N-cadherin, and a significant decrease in chemotherapeutics-induced in vitro tumorigenesis was observed in low-density seeded breast cancer cells when pre-treated with CsA suggesting ABC transporters inhibition-mediated increased efficacy of chemotherapeutics.

CONCLUSION

These findings suggest that breast cancer cells grown at low seeding density imparts chemoresistance towards doxorubicin or tamoxifen by a differential increase in the expression of ABC transporters. Thus, a combinatorial treatment strategy including ABC transporter inhibitors and chemotherapeutics can be a way forward for overcoming the breast cancer chemoresistance.

A synthetic cell density signal can drive proliferation in chick embryonic tendon cells and tendon cells from a full size rooster can produce high levels of procollagen in cell culture

Cell density signaling drives tendon morphogenesis by regulating both procollagen production and cell proliferation. The signal is composed of a small, highly conserved protein (SNZR P) tightly bound to a tissue-specific, unique lipid (SNZR L). This allows the complex (SNZR PL) to bind to the membrane of the cell and locally diffuse over a radius of ~1 mm. The cell produces low levels of this signal but the binding to the membrane increases with the number of tendon cells in the local environment. In this article SNZR P was produced in E.coli and SNZR L was chemically synthesized. The two bind together when heated to 60 °C in the presence of Ca⁺⁺ and Mg⁺⁺ and the synthesized SNZR PL at ng/ml levels can replace serum. Adding SNZR PL to the medium was also tested on primary tendon cells from adult roosters. The older cells were in a maintenance state in vivo and in cell culture they proliferate more slowly than embryonic cells. Nevertheless, after reaching a moderately high cell density, they produced high levels of procollagen similar to the embryonic cells. This data was not expected from older cells but suggests that adult tendon cells can regenerate the tissue after injury when given the correct signals.

The Hippo signalling pathway and its implications in human health and diseases

As an evolutionarily conserved signalling network, the Hippo pathway plays a crucial role in the regulation of numerous biological processes. Thus, substantial efforts have been made to understand the upstream signals that influence the activity of the Hippo pathway, as well as its physiological functions, such as cell proliferation and differentiation, organ growth, embryogenesis, and tissue regeneration/wound healing. However, dysregulation of the Hippo pathway can cause a variety of diseases, including cancer, eye diseases, cardiac diseases, pulmonary diseases, renal diseases, hepatic diseases, and immune dysfunction. Therefore, therapeutic strategies that target dysregulated Hippo components might be promising approaches for the treatment of a wide spectrum of diseases. Here, we review the key components and upstream signals of the Hippo pathway, as well as the critical physiological functions controlled by the Hippo pathway. Additionally, diseases associated with alterations in the Hippo pathway and potential therapies targeting Hippo components will be discussed.

Cross-regulation between microRNAs and key proteins of signaling pathways in hepatocellular carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is a subtype of primary liver cancer and a major cause of death. Although miRNA plays an important role in hepatocellular carcinoma, the specific regulatory network remains unclear. Therefore, this paper comprehensively describes the miRNA-related signaling pathways in HCC and the possible interactions among different signaling pathways. The aim is to lay the foundation for the discovery of new molecular targets and multi-target therapy.

AREAS COVERED

Based on miRNA, HCC, and signaling pathways, the literature was searched on Web of Science and PubMed. Then, common targets between different signaling pathways were found from KEGG database, and possible cross-regulation mechanisms were further studied. In this review, we elaborated from two aspects, respectively, laying a foundation for studying the regulatory mechanism and potential targets of miRNA in HCC.

EXPERT OPINION

Non-coding RNAs have become notable molecules in cancer research in recent years, and many types of targeted drugs have emerged. From the outset, molecular targets and signal pathways are interlinked, which suggests that signal pathways and regulatory networks should be concerned in basic research, which also provides a strong direction for future mechanism research.

Construction and evaluation of detachable bone-targeting MOF carriers for the delivery of proteasome inhibitors

Tumor bone metastasis is an important cause of tumor recurrence and death. Although bone-targeting nanoparticles decorated with targeting ligands have shown good affinity for bone tissues with the properties of adhesion to the bone matrix, it is not easy to detach from the surface of the bone matrix in the tumor-bone microenvironment, attributed to the robust coordination force between the targeting ligands, such as bisphosphates with bone-deposited calcium. This may hinder the transport of nanoparticles from bone tissue to bone metastatic tumors. In this research, we designed a bone-targeting nanocarrier with detachable bone-targeting character for the therapy of bone metastases. The nanoparticles were constructed by using ZIF-8 and bone-targeting and MMP enzyme sensitive polypeptide-modified hyaluronic acid as a carrier and proteasome inhibitor Bortezomib (BTZ) as cargo. The results show that the constructed D8-M3-HA-ZIF8@BTZ nanoparticles possessed several favorable properties such as good colloidal stability, acid-sensitive drug release, D8 peptide mediated bone targeting and MMP enzyme-responsive desorption. Besides, nanoparticle endocytosis and cytotoxicity were enhanced through HA-mediated targeting to CD44 over-expressing tumor cells. Altogether, this study provides a potential cascade targeting strategy for improving the delivery effects of bone targeted nanoparticles for the delivery of proteasome inhibitors.

Tumor bone metastasis is an important cause of tumor recurrence and death.

Lappaol F, an anticancer agent, inhibits YAP via transcriptional and post-translational regulation

CONTEXT

Lappaol F (LAF), a natural lignan from Arctium lappa Linné (Asteraceae), inhibits tumour cell growth by inducing cell cycle arrest. However, its underlying anticancer mechanism remains unclear.

OBJECTIVE

The effects of LAF on the Hippo-Yes-associated protein (YAP) signalling pathway, which plays an important role in cancer progression, were explored in this study.

MATERIALS AND METHODS

Cervical (HeLa), colorectal (SW480), breast (MDA-MB-231) and prostate (PC3) cancer cell lines were treated with LAF at different concentrations and different durations. BALB/c nude mice bearing colon xenografts were intravenously injected with vehicle, LAF (10 or 20 mg/kg) or paclitaxel (10 mg/kg) for 15 days. The expression and nuclear localisation of YAP were analysed using transcriptome sequencing, quantitative PCR, western blotting and immunofluorescence.

RESULTS

LAF suppressed the proliferation of HeLa, MDA-MB-231, SW480 and PC3 cells (IC₅₀ values of 41.5, 26.0, 45.3 and 42.9 μmol/L, respectively, at 72 h), and this was accompanied by significant downregulation in the expression of YAP and its downstream target genes at both the mRNA and protein levels. The expression of 14-3-3σ, a protein that causes YAP cytoplasmic retention and degradation, was remarkably increased, resulting in a decrease in YAP nuclear localisation. Knockdown of 14-3-3σ with small interfering RNA partially blocked LAF-induced YAP inhibition and anti-proliferation effects. In colon xenografts, treatment with LAF led to reduced YAP expression, increased tumour cell apoptosis and tumour growth inhibition.

CONCLUSION

LAF was shown to be an inhibitor of YAP. It exerts anticancer activity by inhibiting YAP at the transcriptional and post-translational levels.

Mechanical coordination is sufficient to promote tissue replacement during metamorphosis in Drosophila

During development, cells coordinate to organize in coherent structures. Although it is now well established that physical forces are essential for implementing this coordination, the instructive roles of mechanical inputs are not clear. Here, we show that the replacement of the larval epithelia by the adult one in Drosophila demands the coordinated exchange of mechanical signals between two cell types, the histoblasts (adult precursors) organized in nests and the surrounding larval epidermal cells (LECs). An increasing stress gradient develops from the center of the nests toward the LECs as a result of the forces generated by histoblasts as they proliferate and by the LECs as they delaminate (push/pull coordination). This asymmetric radial coordination of expansive and contractile activities contributes to epithelial replacement. Our analyses support a model in which cell-cell mechanical communication is sufficient for the rearrangements that implement epithelial morphogenesis.

Yes-associated protein 1 is required for proliferation and function of bovine granulosa cells in vitro†

Yes-associated protein 1 (YAP1) is a major component of the Hippo signaling pathway. Although the exact extracellular signals that control the Hippo pathway are currently unknown, increasing evidence supports a critical role for the Hippo pathway in embryonic development, regulation of organ size, and carcinogenesis. Granulosa cells (GCs) within the ovarian follicle proliferate and produce steroids and growth factors, which facilitate the growth of follicle and maturation of the oocyte. We hypothesize that YAP1 plays a role in proliferation and estrogen secretion of GCs. In the current study, we examined the expression of the Hippo signaling pathway in bovine ovaries and determined whether it was important for GC proliferation and estrogen production. Mammalian STE20-like protein kinase 1 (MST1) and large tumor suppressor kinase 2 (LATS2) were identified as prominent upstream components of the Hippo pathway expressed in granulosa and theca cells of the follicle and large and small cells of the corpus luteum. Immunohistochemistry revealed that YAP1 was localized to the nucleus of growing follicles. In vitro, nuclear localization of the downstream Hippo signaling effector proteins YAP1 and transcriptional co-activator with PDZ-binding motif (TAZ) was inversely correlated with GC density, with greater nuclear localization under conditions of low cell density. Treatment with verteporfin and siRNA targeting YAP1 or TAZ revealed a critical role for these transcriptional co-activators in GC proliferation. Furthermore, knockdown of YAP1 in GCs inhibited follicle-stimulating hormone (FSH)-induced estradiol biosynthesis. The data indicate that Hippo pathway transcription co-activators YAP1/TAZ play an important role in GC proliferation and estradiol synthesis, two processes necessary for maintaining normal follicle development.

A Cell Density-Dependent Reporter in the Drosophila S2 Cells

Cell density regulates many aspects of cell properties and behaviors including metabolism, growth, cytoskeletal structure and locomotion. Importantly, the responses by cultured cells to density signals also uncover key mechanisms that govern animal development and diseases in vivo. Here we characterized a density-responsive reporter system in transgenic Drosophila S2 cells. We show that the reporter genes are strongly induced in a cell density-dependent and reporter-independent fashion. The rapid and reversible induction occurs at the level of mRNA accumulation. We show that multiple DNA elements within the transgene sequences, including a metal response element from the metallothionein gene, contribute to the reporter induction. The reporter induction correlates with changes in multiple cell density and growth regulatory pathways including hypoxia, apoptosis, cell cycle and cytoskeletal organization. Potential applications of such a density-responsive reporter will be discussed.

Cooperativity between stromal cytokines drives the invasive migration of human breast cancer cells

The cross-talk between cancer cells and the stromal microenvironment plays a key role in regulating cancer invasion. Here, we employed an ex vivo invasion model system for exploring the regulation of breast cancer cells infiltration into a variety of stromal fibroblast monolayers. Our results revealed considerable variability in the stromal induction of invasiveness, with some lines promoting and others blocking invasion. It was shown that conditioned medium (CM), derived from invasion-promoting fibroblasts, can induce epithelial-mesenchymal transition-like process in the cancer cells, and trigger their infiltration into a monolayer of invasion-blocking fibroblasts. To identify the specific invasion-promoting molecules, we analysed the cytokines in stimulatory CM, screened a library of purified cytokines for invasion-promoting activity and tested the effect of specific inhibitors of selected cytokine receptors on the CM-induced invasion. Taken together, these experiments indicated that the invasiveness of BT-474 is induced by the combined action of IL1 and IL6 and that IL1 can induce IL6 secretion by invasion-blocking fibroblasts, thereby triggering cancer cell invasion into the stroma. This unexpected observation suggests that stromal regulation of cancer invasion may involve not only cross-talk between stromal and cancer cells, but also cooperation between different stromal subpopulations. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.

SOX9 promotes epithelial-mesenchymal transition via the Hippo-YAP signaling pathway in gastric carcinoma cells

SRY-box 9 (SOX9) is overexpressed in a number of human tumors, including gastric cancer (GC). However, the function of SOX9 in the development of GC remains unknown. In the present study, SOX9 activated the Hippo-yes-associated protein (YAP) signaling pathway to enhance the epithelial-mesenchymal transition in GC cell lines. The results suggested that SOX9 knockdown inhibited invasion, proliferation and migration of GC cells. Furthermore, SOX9 silencing upregulated the expression of E-cadherin, an epithelial marker, and downregulated the expression of mesenchymal markers, including snail family transcriptional repressor 1, vimentin and N-cadherin. SOX9 overexpression increased the expression of the aforementioned markers. SOX9 significantly affected YAP phosphorylation and total YAP protein levels, suggesting that SOX9 is involved in the Hippo-YAP signaling pathway. The current study revealed that SOX9 may be involved in the pathogenesis of GC, and further elucidation of the pathways involved may support the development of novel therapeutic options for the treatment of GC.

Mechanotransduction and Cytoskeleton Remodeling Shaping YAP1 in Gastric Tumorigenesis

The essential role of Hippo signaling pathway in cancer development has been elucidated by recent studies. In the gastrointestinal tissues, deregulation of the Hippo pathway is one of the most important driving events for tumorigenesis. It is widely known that Yes-associated protein 1 (YAP1) and WW domain that contain transcription regulator 1 (TAZ), two transcriptional co-activators with a PDZ-binding motif, function as critical effectors negatively regulated by the Hippo pathway. Previous studies indicate the involvement of YAP1/TAZ in mechanotransduction by crosstalking with the extracellular matrix (ECM) and the F-actin cytoskeleton associated signaling network. In gastric cancer (GC), YAP1/TAZ functions as an oncogene and transcriptionally promotes tumor formation by cooperating with TEAD transcription factors. Apart from the classic role of Hippo-YAP1 cascade, in this review, we summarize the current investigations to highlight the prominent role of YAP1/TAZ as a mechanical sensor and responder under mechanical stress and address its potential prognostic and therapeutic value in GC.

Ecological feedback on diffusion dynamics

Spatial patterns are ubiquitous across different scales of organization in ecological systems. Animal coat pattern, spatial organization of insect colonies and vegetation in arid areas are prominent examples from such diverse ecologies. Typically, pattern formation has been described by reaction-diffusion equations, which consider individuals dispersing between subpopulations of a global pool. This framework applied to public goods game nicely showed the endurance of populations via diffusion and generation of spatial patterns. However, how the spatial characteristics, such as diffusion, are related to the eco-evolutionary process as well as the nature of the feedback from evolution to ecology and vice versa, has been so far neglected. We present a thorough analysis of the ecologically driven evolutionary dynamics in a spatially extended version of ecological public goods games. Furthermore, we show how these evolutionary dynamics feed back into shaping the ecology, thus together determining the fate of the system.

Downregulation of NDR1 contributes to metastasis of prostate cancer cells via activating epithelial-mesenchymal transition

The 5‐year survival rate decreases rapidly once the prostate cancer has invaded distant organs, although patients with localized prostate cancer have a good prognosis. In recent years, increasing numbers of reports showed that circulating tumor cells (CTCs) may play an important role in tumor metastasis and they have stronger potential of invasion and migration compared with their parental cells. In our previous investigation, we isolated CTCs from prostate cancer cell lines PC3. In this study, we found a novel antimetastasis gene NDR1 by analyzing different gene expression between CTCs and PC3. Lower NDR1 gene and protein expression were found in both prostate cancer cell lines and clinical specimens. Besides, NDR1 function acting as metastasis inhibitor was discovered both in vitro and in vivo. Further, we also discovered that several epithelial‐mesenchymal transition (EMT)‐related genes were upregulated when decreased NDR1 in PC3 cell lines. Therefore, our results revealed a role of NDR1 in the suppression of prostate cancer cell metastasis and provided a potential mechanism of action, thus offering new therapeutic strategies against prostate cancer metastasis.

Suppression of YAP by DDP disrupts colon tumor progression

Colon cancer is a commonly diagnosed cancer that often has a poor prognosis. Combined with the development of drug resistance to cancer treatment agents the treatment efficacy of colon cancer can be limited. Activation of the oncogene YAP has been shown to be related to colon cancer progression and is associated with poor prognosis, drug resistance and metastasis, even under treatment. Cisplatin (DDP) is a commonly used drug that can control carcinoma progression, although its mechanisms are poorly understood. In the present study, we examined whether DDP specifically suppressed YAP in order to inhibit colon carcinoma progression. Our data revealed that Mst/Yap signaling was unusually activated in colon cancers, promoting cell proliferation and invasion. DDP treatment decreased the expression of YAP at both the transcriptional and post-translational levels, leading to cell cycle arrest, apoptosis and senescence in cancer cells, in addition to decreasing epithelial-to-mesenchymal transition, cell motility and in vitro cell invasion and migration. Ultimately, DDP increased the expression of E-cadherin and decreased the expression of vimentin. The present study also revealed that post-translational regulation of YAP phosphorylation controlled the subcellular distribution between the nucleus and the cytoplasm. In conclusion, the findings of the present study revealed that DDP was a suitable therapeutic candidate for colon cancer that specifically targets the Mst/Yap signaling pathway.

Mammalian Eps15 homology domain 1 promotes metastasis in non-small cell lung cancer by inducing epithelial-mesenchymal transition

The identification of the earliest molecular events responsible for the metastatic dissemination of non-small cell lung cancer (NSCLC) remains critical for early detection, prevention, and treatment interventions. In this study, we hypothesized that Mammalian Eps15 homology domain 1 (EHD1) might be responsible for the metastatic behavior of cells in NSCLC. We demonstrated that upregulation of EHD1 is associated with lymph nodes metastasis and unfavorable survival in patients with NSCLC. EHD1 knockdown inhibited the invasion and migration of human NSCLC cells, and overexpression of EHD1 increased the metastatic potential of lung cancer cells. Using the Affymetrix Human Gene 1.0 ST platform, microarray analysis revealed that an association between EHD1 and epithelial-mesenchymal transition (EMT), supported by downregulation of mesenchymal markers and upregulation of epithelial markers following knockdown of EHD1 in cell lines. Moreover, overexpression of EHD1 induced the EMT and increased the metastatic potential of lung cancer cells in vitro and in vivo. These results provide a model to illustrate the relationship between EHD1 expression and lung cancer metastasis, opening up new avenues for the prognosis and therapy of lung cancer.