Overcoming anoikis--pathways to anchorage-independent growth in cancer

The Dual Role of Autophagy in Cancer Development and a Therapeutic Strategy for Cancer by Targeting Autophagy

Autophagy is a delicate intracellular degradation process that occurs due to diverse stressful conditions, including the accumulation of damaged proteins and organelles as well as nutrient deprivation. The mechanism of autophagy is initiated by the creation of autophagosomes, which capture and encapsulate abnormal components. Afterward, autophagosomes assemble with lysosomes to recycle or remove degradative cargo. The regulation of autophagy has bipolar roles in cancer suppression and promotion in diverse cancers. Furthermore, autophagy modulates the features of tumorigenesis, cancer metastasis, cancer stem cells, and drug resistance against anticancer agents. Some autophagy regulators are used to modulate autophagy for anticancer therapy but the dual roles of autophagy limit their application in anticancer therapy, and present as the main reason for therapy failure. In this review, we summarize the mechanisms of autophagy, tumorigenesis, metastasis, cancer stem cells, and resistance against anticancer agents. Finally, we discuss whether targeting autophagy is a promising and effective therapeutic strategy in anticancer therapy.

Tumor Hypoxia and Circulating Tumor Cells

Circulating tumor cells (CTCs) are a rare tumor cell subpopulation induced and selected by the tumor microenvironment's extreme conditions. Under hypoxia and starvation, these aggressive and invasive cells are able to invade the lymphatic and circulatory systems. Escaping from the primary tumor, CTCs enter into the bloodstream to form metastatic deposits or re-establish themselves in cancer's primary site. Although radiotherapy is widely used to cure solid malignancies, it can promote metastasis. Radiation can disrupt the primary tumor vasculature, increasing the dissemination of CTCs. Radiation also induces epithelial-mesenchymal transition (EMT) and eliminates suppressive signaling, causing the proliferation of existent, but previously dormant, disseminated tumor cells (DTCs). In this review, we collect the results and evidence underlying the molecular mechanisms of CTCs and DTCs and the effects of radiation and hypoxia in developing these cells.

EMT, cancer stem cells and autophagy; The three main axes of metastasis

Epithelial-mesenchymal transition (EMT) and Cancer stem-like cells (CSCs) are major factors contributing to the metastasis of cancer cells. Consequently, the signaling pathways involved in both processes are appropriate therapeutic targets in the treatment of metastasis. Autophagy is another process that has recently attracted the attention of many researchers; depending on the type of cancer and tissue and the stage of cancer, this process can play a dual role in the development of cancer cells. Studies on cancer cells have shown that different signaling pathways are involved in all three processes, namely, cancer stem cells, autophagy, and EMT. The purpose of this study was to investigate and elucidate the relationship between the effective signaling pathways in all three processes, which could play an effective role in determining appropriate therapeutic goals.

Development of a High-throughput Agar Colony Formation Assay to Identify Drug Candidates against Medulloblastoma

Medulloblastoma (MB) is the most common malignant childhood brain cancer. High-risk MB tumours have a high incidence of metastasis and result in poor patient survival. Drug screens, commonly used to identify potential novel therapeutic agents against MB, focus on 2D cell proliferation and viability assays given that these assays are easily adaptable to high-throughput regimes. However, 2D models fail to address invasive characteristics that are crucial to MB metastasis and are thus not representative of tumour growth in vivo. In this study, we developed a 3D 384-well agar colony formation assay using MB cells of molecular subgroup 3 that is associated with the highest level of metastasis. Two fluorescence substrates, resazurin and glycyl-phenylalanyl-aminofluorocoumarin (GF-AFC) that measure cell viability via distinct mechanisms were used to assess the growth of MB cells in the agar matrix. The assay was optimised for seeding density, growth period, substrate incubation time and homogeneity of the fluorescent signals within individual wells. Our data demonstrate the feasibility to multiplex the two fluorescent substrates without detectable signal interference. This assay was validated by assessing the concentration-dependent effect of two commonly used chemotherapeutic agents clinically used for MB treatment, vincristine and lomustine. Subsequently, a panel of plasma membrane calcium channel modulators was screened for their effect on the 3D growth of D341 MB cells, which identified modulators of T-type voltage gated and ORAI calcium channels as selective growth modulators. Overall, this 3D assay provides a reproducible, time and cost-effective assay for high-throughput screening to identify potential drugs against MB.

Soft Microenvironments Induce Chemoresistance by Increasing Autophagy Downstream of Integrin-Linked Kinase

Breast cancer relapse can develop over the course of years as a result of dormant cancer cells that disseminate to secondary sites. These dormant cells are often resistant to conventional hormone and chemotherapy. Although recurrence is the main cause of death from cancer, microenvironmental factors that may influence resistance to therapy and duration of dormancy are largely unknown. Breast cancer relapse is often detected in tissues that are softer than the normal mammary gland or the primary breast tumor, such as bone marrow, brain, and lung. We therefore explored how stiffness of the microenvironment at secondary sites regulates tumor dormancy and the response of breast cancer cells to hormone and chemotherapy. In soft microenvironments reminiscent of metastatic sites, breast cancer cells were more resistant to the estrogen receptor modulator tamoxifen as a result of increased autophagy and decreased expression of estrogen receptor-α. Consistently, pharmacologic inhibition or genetic downregulation of autophagy increased the response of breast cancer cells to tamoxifen on soft substrata. In addition, autophagy was decreased downstream of integrin-linked kinase on stiff substrata. Altogether, our data show that tissue mechanics regulates therapeutic outcome and long-term survival of breast cancer cells by influencing autophagy. SIGNIFICANCE: These findings characterize the persistence of dormant cells at metastatic sites, where soft microenvironments downregulate estrogen receptor expression and upregulate autophagy, thereby promoting therapy resistance in breast cancer cells. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/19/4103/F1.large.jpg.

Protein kinase A inhibitor proteins (PKIs) divert GPCR-Gαs-cAMP signaling toward EPAC and ERK activation and are involved in tumor growth

The PKA-inhibitor (PKI) family members PKIα, PKIβ, and PKIγ bind with high affinity to PKA and block its kinase activity, modulating the extent, and duration of PKA-mediated signaling events. While PKA is a well-known regulator of physiological and oncogenic events, the role of PKI proteins in these pathways has remained elusive. Here, by measuring activation of the MAPK pathway downstream of GPCR-Gαs-cAMP signaling, we show that the expression levels of PKI proteins can alter the balance of activation of two major cAMP targets: PKA and EPAC. Our results indicate that PKA maintains repressive control over MAPK signaling as well as a negative feedback on cAMP concentration. Overexpression of PKI and its subsequent repression of PKA dysregulates these signaling pathways, resulting in increased intracellular cAMP, and enhanced activation of EPAC and MAPK. We also find that amplifications of PKIA are common in prostate cancer and are associated with reduced progression free survival. Depletion of PKIA in prostate cancer cells leads to reduced migration, increased sensitivity to anoikis and reduced tumor growth. By altering PKA activity PKI can act as a molecular switch, driving GPCR-Gαs-cAMP signaling toward activation of EPAC-RAP1 and MAPK, ultimately modulating tumor growth.

Indomethacin can induce cell death in rat gastric parietal cells through alteration of some apoptosis- and autophagy-associated molecules

In clinical medicine, indomethacin (IND, a non-steroidal anti-inflammatory drug) is used variously in the treatment of severe osteoarthritis, rheumatoid arthritis, gouty arthritis or ankylosing spondylitis. A common complication found alongside the therapeutic characteristics is gastric mucosal damage. This complication is mediated through apoptosis and autophagy of the gastrointestinal mucosal epithelium. Apoptosis and autophagy are critical homeostatic pathways catalysed by caspases downstream of the gastrointestinal mucosal epithelial injury. Both act through molecular signalling pathways characterized by the initiation, mediation, execution and regulation of the cell regulatory cycle. In this study we hypothesized that dysregulated apoptosis and autophagy are associated with IND-induced gastric damage. We examined the spectra of in vivo experimental gastric ulcers in male Sprague-Dawley rats through gastric gavage of IND. Following an 18-hour fast, IND was administered to experimental rats. They were sacrificed at 3-, 6- and 12-hour intervals. Parietal cells (H⁺ , K⁺ -ATPase β-subunit assay) and apoptosis (TUNEL assay) were determined. The expression of apoptosis-signalling caspase (caspases 3, 8, 9 and 12), DNA damage (anti-phospho-histone H2A.X) and autophagy (MAP-LC3, LAMP-1 and cathepsin B)-related molecules in gastric mucosal cells was examined. The administration of IND was associated with gastric mucosal erosions and ulcerations mainly involving the gastric parietal cells (PCs) of the isthmic and upper neck regions and a time-dependent gradual increase in the number of apoptotic PCs with the induction of both apoptotic (upregulation of caspases 3 and 8) cell death and autophagic (MAP-LC3-II, LAMP-1 and cathepsin B) cell death. Autophagy induced by fasting and IND 3 hours initially prompted the degradation of caspase 8. After 6 and 12 hours, damping down of autophagic activity occurred, resulting in the upregulation of active caspase 8 and its nuclear translocation. In conclusion we report that IND can induce time-dependent apoptotic and autophagic cell death of PCs. Our study provides the first indication of the interactions between these two homeostatic pathways in this context.

Metabolic reprogramming sustains cancer cell survival following extracellular matrix detachment

Epithelial cells require attachment to a support, such as the extracellular matrix, for survival. During cancer progression and metastasis, cancerous epithelial cells must overcome their dependence on adhesion signals. Dependence on glucose metabolism is a hallmark of cancer cells, but the nutrient requirements of cancer cells under anchorage-deficient conditions remain uncharacterized. Here, we report that cancer cells prioritize glutamine-derived tricarboxylic acid cycle energy metabolism over glycolysis to sustain anchorage-independent survival. Moreover, glutamine-dependent metabolic reprogramming is required not only to maintain ATP levels but also to suppress excessive oxidative stress through interaction with cystine. Mechanistically, AMPK, a central regulator of cellular responses to metabolic stress, participates in the induction of the expression of ASCT2, a glutamine transporter, and enhances glutamine consumption. Most interestingly, AMPK activation induces Nrf2 and its target proteins, allowing cancer cells to maintain energy homeostasis and redox status through glutaminolysis. Treatment with an integrin inhibitor was used to mimic the alterations in cell morphology and metabolic reprogramming caused by detachment. Under these conditions, cells were vulnerable to glutamine starvation or glutamine metabolism inhibitors. The observed preference for glutamine over glucose was more pronounced in aggressive cancer cell lines, and treatment with the glutaminase inhibitor, CB839, and cystine transporter inhibitor, sulfasalazine, caused strong cytotoxicity. Our data clearly show that anchorage-independent survival of cancer cells is supported mainly by glutaminolysis via the AMPK-Nrf2 signal axis. The discovery of new vulnerabilities along this route could help slow or prevent cancer progression.

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AMPK-Nrf2 signaling is crucial in metabolic reprogramming during cancer progression.

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Cancer metabolism does not preeminently depend on glycolysis.

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Glutaminolysis mainly supports anchorage-independent cancer cell survival.

Molecular mediators of peritoneal metastasis in pancreatic cancer

Pancreatic cancer is the third leading cause of cancer death in the USA, and pancreatic ductal adenocarcinoma (PDA) constitutes 85% of pancreatic cancer diagnoses. PDA frequently metastasizes to the peritoneum, but effective treatment of peritoneal metastasis remains a clinical challenge. Despite this unmet need, understanding of the biological mechanisms that contribute to development and progression of PDA peritoneal metastasis is sparse. By contrast, a vast number of studies have investigated mechanisms of peritoneal metastasis in ovarian and gastric cancers. Here, we contrast similarities and differences between peritoneal metastasis in PDA as compared with those in gastric and ovarian cancer by outlining molecular mediators involved in each step of the peritoneal metastasis cascade. This review aims to provide mechanistic insights that could be translated into effective targeted therapies for patients with peritoneal metastasis from PDA.

Effects of Cancer Stem Cells in Triple-Negative Breast Cancer and Brain Metastasis: Challenges and Solutions

A higher propensity of developing brain metastasis exists in triple-negative breast cancer (TNBC). Upon comparing the metastatic patterns of all breast cancer subtypes, patients with TNBC exhibited increased risks of the brain being the initial metastatic site, early brain metastasis development, and shortest brain metastasis-related survival. Notably, the development of brain metastasis differs from that at other sites owing to the brain-unique microvasculature (blood brain barrier (BBB)) and intracerebral microenvironment. Studies of brain metastases from TNBC have revealed the poorest treatment response, mostly because of the relatively backward strategies to target vast disease heterogeneity and poor brain efficacy. Moreover, TNBC is highly associated with the existence of cancer stem cells (CSCs), which contribute to circulating cancer cell survival before BBB extravasation, evasion from immune surveillance, and plasticity in adaptation to the brain-specific microenvironment. We summarized recent literature regarding molecules and pathways and reviewed the effects of CSC biology during the formation of brain metastasis in TNBC. Along with the concept of individualized cancer therapy, certain strategies, namely the patient-derived xenograft model to overcome the lack of treatment-relevant TNBC classification and techniques in BBB disruption to enhance brain efficacy has been proposed in the hope of achieving treatment success.

Rapha Myr®, a Blend of Sulforaphane and Myrosinase, Exerts Antitumor and Anoikis-Sensitizing Effects on Human Astrocytoma Cells Modulating Sirtuins and DNA Methylation

Brain and other nervous system cancers are the 10th leading cause of death worldwide. Genome instability, cell cycle deregulation, epigenetic mechanisms, cytoarchitecture disassembly, redox homeostasis as well as apoptosis are involved in carcinogenesis. A diet rich in fruits and vegetables is inversely related with the risk of developing cancer. Several studies report that cruciferous vegetables exhibited antiproliferative effects due to the multi-pharmacological functions of their secondary metabolites such as isothiocyanate sulforaphane deriving from the enzymatic hydrolysis of glucosinolates. We treated human astrocytoma 1321N1 cells for 24 h with different concentrations (0.5, 1.25 and 2.5% v/v) of sulforaphane plus active myrosinase (Rapha Myr®) aqueous extract (10 mg/mL). Cell viability, DNA fragmentation, PARP-1 and γH2AX expression were examined to evaluate genotoxic effects of the treatment. Cell cycle progression, p53 and p21 expression, apoptosis, cytoskeleton morphology and cell migration were also investigated. In addition, global DNA methylation, DNMT1 mRNA levels and nuclear/mitochondrial sirtuins were studied as epigenetic biomarkers. Rapha Myr® exhibited low antioxidant capability and exerted antiproliferative and genotoxic effects on 1321N1 cells by blocking the cell cycle, disarranging cytoskeleton structure and focal adhesions, decreasing the integrin α5 expression, renewing anoikis and modulating some important epigenetic pathways independently of the cellular p53 status. In addition, Rapha Myr® suppresses the expression of the oncogenic p53 mutant protein. These findings promote Rapha Myr® as a promising chemotherapeutic agent for integrated cancer therapy of human astrocytoma.

Proteomic and transcriptomic profiling identifies mediators of anchorage-independent growth and roles of inhibitor of differentiation proteins in invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is a histological subtype of breast cancer with distinct molecular and clinical features from the more common subtype invasive ductal carcinoma (IDC). ILC cells exhibit anchorage-independent growth in ultra-low attachment (ULA) suspension cultures, which is largely attributed to the loss of E-cadherin. In addition to anoikis resistance, herein we show that human ILC cell lines exhibit enhanced cell proliferation in ULA cultures as compared to IDC cells. Proteomic comparison of ILC and IDC cell lines identified induction of PI3K/Akt and p90-RSK pathways specifically in ULA culture in ILC cells. Further transcriptional profiling uncovered unique upregulation of the inhibitors of differentiation family transcription factors ID1 and ID3 in ILC ULA culture, the knockdown of which diminished the anchorage-independent growth of ILC cell lines through cell cycle arrest. We find that ID1 and ID3 expression is higher in human ILC tumors as compared to IDC, correlated with worse prognosis uniquely in patients with ILC and associated with upregulation of angiogenesis and matrisome-related genes. Altogether, our comprehensive study of anchorage independence in human ILC cell lines provides mechanistic insights and clinical implications for metastatic dissemination of ILC and implicates ID1 and ID3 as novel drivers and therapeutic targets for lobular breast cancer.

A PI3K- and GTPase-independent Rac1-mTOR mechanism mediates MET-driven anchorage-independent cell growth but not migration

Receptor tyrosine kinases (RTKs) are often overexpressed or mutated in cancers and drive tumor growth and metastasis. In the current model of RTK signaling, including that of MET, downstream phosphatidylinositol 3-kinase (PI3K) mediates both cell proliferation and cell migration, whereas the small guanosine triphosphatase (GTPase) Rac1 mediates cell migration. However, in cultured NIH3T3 and glioblastoma cells, we found that class I PI3K mediated oncogenic MET-induced cell migration but not anchorage-independent growth. In contrast, Rac1 regulated both processes in distinct ways. Downstream of PI3K, Rac1 mediated cell migration through its GTPase activity, whereas independently of PI3K, Rac1 mediated anchorage-independent growth in a GTPase-independent manner through an adaptor function. Through its RKR motif, Rac1 formed a complex with the kinase mTOR to promote its translocation to the plasma membrane, where its activity promoted anchorage-independent growth of the cell cultures. Inhibiting mTOR with rapamycin suppressed the growth of subcutaneous MET-mutant cell grafts in mice, including that of MET inhibitor-resistant cells. These findings reveal a GTPase-independent role for Rac1 in mediating a PI3K-independent MET-to-mTOR pathway and suggest alternative or combined strategies that might overcome resistance to RTK inhibitors in patients with cancer.

Cox2-mediated PGE2 production via p38/JNK-c-fos signaling inhibits cell apoptosis in 3D floating culture clumps of mesenchymal stem cell/extracellular matrix complexes

Mesenchymal stem cells (MSCs), a class of adult stem cells, have attracted scientific and medical attention due to their self-renewing properties, multipotency, and trophic factor production. Although MSCs were originally studied on classical two-dimensional (2D) plastic plates, extensive scientific efforts have developed three-dimensional (3D) MSC culture systems, including MSCs spheroids and organoids that can mimic physical conditions. Moreover, we have recently developed 3D culture clumps of MSCs/extracellular matrix (ECM) complexes (C-MSCs) for novel bone regenerative cell therapy. Of note, even though it is widely accepted that cell detachment from the culture plate causes cell apoptosis, so called anoikis, these 3D MSCs constructs can be maintained in floating culture conditions. Currently, it is unclear why 3D floating-cultured MSCs constructs can escape from anoikis. To answer this question, the present study explored trophic factor production in 3D floating-cultured C-MSCs that play a cytoprotective role against anoikis and clarified the underlying molecular mechanism in vitro. Compared with cells cultured on 2D plastic plates, PGE2 production mediated by COX2 was significantly increased, and its inhibition drastically induced cell apoptosis in 3D floating-cultured C-MSCs. In the process of C-MSCs preparation, detachment of the cell sheet from culture plate activated the p38/JNK-c-Fos signaling pathway. Moreover, blockage of this signaling by chemical inhibitors abrogated COX2/PGE2 expressions and induced severe apoptosis. These results demonstrated that cell detachment facilitates cytoprotective COX2-mediated PGE2 synthesis via p38/JNK-c-Fos signaling, revealing a possible mechanism that allows resistance against anoikis in floating-cultured 3D MSCs constructs.

Competitive Cell Death Interactions in Pulmonary Infection: Host Modulation Versus Pathogen Manipulation

In the context of pulmonary infection, both hosts and pathogens have evolved a multitude of mechanisms to regulate the process of host cell death. The host aims to rapidly induce an inflammatory response at the site of infection, promote pathogen clearance, quickly resolve inflammation, and return to tissue homeostasis. The appropriate modulation of cell death in respiratory epithelial cells and pulmonary immune cells is central in the execution of all these processes. Cell death can be either inflammatory or anti-inflammatory depending on regulated cell death (RCD) modality triggered and the infection context. In addition, diverse bacterial pathogens have evolved many means to manipulate host cell death to increase bacterial survival and spread. The multitude of ways that hosts and bacteria engage in a molecular tug of war to modulate cell death dynamics during infection emphasizes its relevance in host responses and pathogen virulence at the host pathogen interface. This narrative review outlines several current lines of research characterizing bacterial pathogen manipulation of host cell death pathways in the lung. We postulate that understanding these interactions and the dynamics of intracellular and extracellular bacteria RCD manipulation, may lead to novel therapeutic approaches for the treatment of intractable respiratory infections.

STIM1 is a metabolic checkpoint regulating the invasion and metastasis of hepatocellular carcinoma

Background: Cancer cells undergoing invasion and metastasis possess a phenotype with attenuated glycolysis, but enhanced fatty acid oxidation (FAO). Calcium (Ca²⁺)-mediated signaling pathways are implicated in tumor metastasis and metabolism regulation. Stromal-interaction molecule 1 (STIM1) triggered store-operated Ca²⁺ entry (SOCE) is the major route of Ca²⁺ influx for non-excitable cells including hepatocellular carcinoma (HCC) cells. However, whether and how STIM1 regulates the invasion and metastasis of HCC via metabolic reprogramming is unclear.

Methods: The expressions of STIM1 and Snail1 in the HCC tissues and cells were measured by immunohistochemistry, Western-blotting and quantitative PCR. STIM1 knockout-HCC cells were generated by CRISPR-Cas9, and gene-overexpression was mediated via lentivirus transfection. Besides, the invasive and metastatic activities of HCC cells were assessed by transwell assay, anoikis rate in vitro and lung metastasis in vivo. Seahorse energy analysis and micro-array were used to evaluate the glucose and lipid metabolism.

Results: STIM1 was down-regulated in metastatic HCC cells rather than in proliferating HCC cells, and low STIM1 levels were associated with poor outcome of HCC patients. During tumor growth, STIM1 stabilized Snail1 protein by activating the CaMKII/AKT/GSK-3β pathway. Subsequently, the upregulated Snail1 suppressed STIM1/SOCE during metastasis. STIM1 restoration significantly diminished anoikis-resistance and metastasis induced by Snail1. Mechanistically, the downregulated STIM1 shifted the anabolic/catabolic balance, i.e., from aerobic glycolysis towards AMPK-activated fatty acid oxidation (FAO), which contributed to Snail1-driven metastasis and anoikis-resistance.

Conclusions: Our data provide the molecular basis that STIM1 orchestrates invasion and metastasis via reprogramming HCC metabolism.

Synergies in exosomes and autophagy pathways for cellular homeostasis and metastasis of tumor cells

Background

Eukaryotic cells demonstrate two tightly linked vesicular transport systems, comprising intracellular vesicle transport and extracellular vesicle transport system. Intracellular transport vesicles can translocate biomolecules between compartments inside the cell, for example, proteins from the rough endoplasmic reticulum to the Golgi apparatus. Whereas, the secreted vesicles so-called extracellular vesicles facilitate the transport of biomolecules, for example, nucleic acids, proteins and lipids between cells. Vesicles can be formed during the process of endocytosis or/and autophagy and not only act as mediators of intra- and inter-cellular communication but also represent pathological conditions of cells or tissues.

Methods

In this review, we searched articles in PubMed, published between 2000 and 2020, with following terms: autophagy, autophagocytosis, transport vesicles, lysosomes, endosomes, exocytosis, exosomes, alone or in different combinations. The biological functions that were selected based on relevancy to our topic include cellular homeostasis and tumorigenesis.

Results

The searched literature shows that there is a high degree of synergies between exosome biogenesis and autophagy, which encompass endocytosis and endosomes, lysosomes, exocytosis and exosomes, autophagocytosis, autophagosomes and amphisomes. These transport systems not only maintain cellular homeostasis but also operate synergically against fluctuations in the external and internal environment such as during tumorigenesis and metastasis. Additionally, exosomal and autophagic proteins may serve as cancer diagnosis approaches.

Conclusion

Exosomal and autophagy pathways play pivotal roles in homeostasis and metastasis of tumor cells. Understanding the crosstalk between endomembrane organelles and vesicular trafficking may expand our insight into cooperative functions of exosomal and autophagy pathways during disease progression and may help to develop effective therapies against lysosomal diseases including cancers and beyond.

Involvement of MicroRNA-296 in the Inhibitory Effect of Epigallocatechin Gallate against the Migratory Properties of Anoikis-Resistant Nasopharyngeal Carcinoma Cells

Short noncoding endogenous RNAs, including microRNAs (miRNAs), are associated with the development and metastasis of multiple cancers. Epigallocatechin gallate (EGCG), the most active and abundant polyphenol in green tea, plays a crucial role in the modulation of miRNA expression, which is related to changes in cancer progression. In the present study, we explore whether EGCG exerts its suppressive effects on nasopharyngeal carcinoma (NPC) cells through miRNA regulation. The anoikis-resistant sphere-forming NPC cells grown under anchorage-independent conditions exhibit enhanced migratory properties, which were inhibited by EGCG treatment. The miR-296 level was lower in the anoikis-resistant cells than in the monolayer parental cells; however, miR-296 was significantly upregulated after EGCG treatment. We demonstrate that miR-296 is involved in the inhibitory effects of EGCG on the anoikis-resistant NPC cells through the downregulation of signal transducer and activator of transcription 3 (STAT3) activation. Our study is the first to demonstrate that EGCG inhibited the migratory properties of anoikis-resistant cells by modulating the expression of miRNA in NPC cells. Our results indicate the novel effects of EGCG on miRNA regulation to inhibit an invasive phenotype of NPC as well as the regulatory role of miR-296.

The rise of T-type channels in melanoma progression and chemotherapeutic resistance

Hyperactivation of the Mitogen Activated Protein Kinase (MAPK) pathway is prevalent in melanoma, principally due to mutations in the BRAF and NRAS genes. MAPK inhibitors are effective only short-term, and recurrence occurs due to functional redundancies or intertwined pathways. The remodeling of Ca²⁺ signaling is also common in melanoma cells, partly through the increased expression of T-type channels (TTCCs). Here we summarize current knowledge about the prognostic value and molecular targeting of TTCCs. Furthermore, we discuss recent evidence pointing to TTCCs as molecular switches for melanoma chemoresistance, which set the grounds for novel combined therapies against the advanced disease.

SPIB promotes anoikis resistance via elevated autolysosomal process in lung cancer cells

Anoikis (detachment-induced cell death) is a specific type of programmed cell death which occurs in response to the loss of the correct extracellular matrix connections. Anoikis resistance is an important mechanism in cancer invasiveness and metastatic behavior. Autophagy, on the other hand, involves the degradation of damaged organelles and the recycling of misfolded proteins and intracellular components. However, the intersection of these two cellular responses in lung cancer cells has not been extensively studied. Here, we identified that upon matrix deprivation, the lymphocyte lineage-specific Ets transcription factor SPIB was activated and directly enhanced SNAP47 transcription in certain lung cancer cells. Loss of attachment-induced autophagy significantly increased anoikis resistance by SPIB activation. Consistent with this function, SPIB depletion by short hairpin RNA abrogated SNAP47 transcriptional activation upon matrix deprivation. Therefore, these data delineate an important role of SPIB in autophagy-mediated anoikis resistance in lung cancer cells. Accordingly, these findings suggest that manipulating SPIB-regulated pathways in vivo and evaluating the impact of anoikis resistance warrant further investigation. DATABASE: RNA sequencing and ChIP sequencing data are available in Gene Expression Omnibus database under the accession numbers GSE106592 and GSE125561, respectively.

Identification of Deregulated Pathways, Key Regulators, and Novel miRNA-mRNA Interactions in HPV-Mediated Transformation

Next to a persistent infection with high-risk human papillomavirus (HPV), molecular changes are required for the development of cervical cancer. To identify which molecular alterations drive carcinogenesis, we performed a comprehensive and longitudinal molecular characterization of HPV-transformed keratinocyte cell lines. Comparative genomic hybridization, mRNA, and miRNA expression analysis of four HPV-containing keratinocyte cell lines at eight different time points was performed. Data was analyzed using unsupervised hierarchical clustering, integrated longitudinal expression analysis, and pathway enrichment analysis. Biological relevance of identified key regulatory genes was evaluated in vitro and dual-luciferase assays were used to confirm predicted miRNA-mRNA interactions. We show that the acquisition of anchorage independence of HPV-containing keratinocyte cell lines is particularly associated with copy number alterations. Approximately one third of differentially expressed mRNAs and miRNAs was directly attributable to copy number alterations. Focal adhesion, TGF-beta signaling, and mTOR signaling pathways were enriched among these genes. PITX2 was identified as key regulator of TGF-beta signaling and inhibited cell growth in vitro, most likely by inducing cell cycle arrest and apoptosis. Predicted miRNA-mRNA interactions miR-221-3p_BRWD3, miR-221-3p_FOS, and miR-138-5p_PLXNB2 were confirmed in vitro. Integrated longitudinal analysis of our HPV-induced carcinogenesis model pinpointed relevant interconnected molecular changes and crucial signaling pathways in HPV-mediated transformation.

Novel HDAC11 inhibitors suppress lung adenocarcinoma stem cell self-renewal and overcome drug resistance by suppressing Sox2

Non-small cell lung cancer (NSCLC) is known to have poor patient outcomes due to development of resistance to chemotherapy agents and the EGFR inhibitors, which results in recurrence of highly aggressive lung tumors. Even with recent success in immunotherapy using the checkpoint inhibitors, additional investigations are essential to identify novel therapeutic strategies for efficacious treatment for NSCLC. Our finding that high levels of histone deacetylase 11 (HDAC11) in human lung tumor tissues correlate with poor patient outcome and that depletion or inhibition of HDAC11 not only significantly reduces self-renewal of cancer stem cells (CSCs) from NSCLC but also decreases Sox2 expression that is essential for maintenance of CSCs, indicates that HDAC11 is a potential target to combat NSCLC. We find that HDAC11 suppresses Sox2 expression through the mediation of Gli1, the Hedgehog pathway transcription factor. In addition, we have used highly selective HDAC11 inhibitors that not only target stemness and adherence independent growth of lung cancer cells but these inhibitors could also efficiently ablate the growth of drug-insensitive stem-like cells as well as therapy resistant lung cancer cells. These inhibitors were found to be efficacious even in presence of cancer associated fibroblasts which have been shown to contribute in therapy resistance. Our study presents a novel role of HDAC11 in lung adenocarcinoma progression and the potential use of highly selective inhibitors of HDAC11 in combating lung cancers.

Caspase-8: The double-edged sword

Caspase-8 is a cysteine - aspartate specific protease that classically triggers the extrinsic apoptotic pathway, in response to the activation of cell surface Death Receptors (DRs) like FAS, TRAIL-R and TNF-R. Besides it's roles in triggering death receptor-mediated apoptosis, Caspase-8 has also been implicated in the onsets of anoikis, autophagy and pyroptosis. Furthermore, Caspase-8 also plays a crucial pro-survival function by inhibiting an alternative form of programmed cell death called necroptosis. Low expression levels of pro-Caspase-8 is therefore associated with the malignant transformation of cancers. However, the long-held notion that pro-Caspase-8 expression/activity is generally lost in most cancers, thereby contributing to apoptotic escape and enhanced resistance to anti-cancer therapeutics, has been found to be true for only a minority of cancers types. In the majority of cases, pro-Caspase-8 expression is maintained and sometimes elevated, while it's apoptotic activity is regulated through different mechanisms. This supports the notion that the non-apoptotic functions of Caspase-8 offer growth advantage in these cancer types and have, therefore, gained renewed interest in the recent years. In light of these reasons, a number of therapeutic approaches have been employed, with the intent of targeting pro-Caspase-8 in cancer cells. In this review, we would attempt to discuss - the classic roles of Caspase-8 in initiating apoptosis; it's non-apoptotic functions; it's the clinical significance in different cancer types; and the therapeutic applications exploiting the ability of pro-Caspase-8 to regulate various cellular functions.

Changes in the Surface Expression of Intercellular Adhesion Molecule 3, the Induction of Apoptosis, and the Inhibition of Cell-Cycle Progression of Human Multidrug-Resistant Jurkat/A4 Cells Exposed to a Random Positioning Machine

Experiments from flight- and ground-based model systems suggest that unexpected alterations of the human lymphoblastoid cell line Jurkat, as well as effects on cell growth, metabolism, and apoptosis, can occur in altered gravity conditions. Using a desktop random positioning machine (RPM), we investigated the effects of simulated microgravity on Jurkat cells and their multidrug-resistant subline, Jurkat/A4 cells. The viability of Jurkat/A4 cells decreased after simulated microgravity in contrast with the Jurkat cells. At the same time, the viability between the experimental Jurkat cells and control Jurkat cells was not significantly different. Of note, Jurkat cells appeared as less susceptible to apoptosis than their multidrug-resistant clone Jurkat/A4 cells, whereas cell-cycle analysis showed that the percentage of Jurkat/A4 cells in the S-phase was increased after 72 and 96 h of RPM-simulated microgravity relative to their static counterparts. The differences in Jurkat cells at all phases between static and simulated microgravity were not significant. The surface expression of the intercellular adhesion molecule 3 (ICAM-3)-also known as cluster of differentiation (CD)50-protein was changed for Jurkat/A4 cells following exposure to the RPM. Changes in cell morphology were observed in the Jurkat/A4 cells after 96 h of RPM-simulated microgravity. Thus, we concluded that Jurkat/A4 cells are more sensitive to RPM-simulated microgravity as compared with the parental Jurkat cell line. We also suggest that intercellular adhesion molecule 3 may be an important adhesion molecule involved in the induction of leukocyte apoptosis. The Jurkat/A4 cells with an acquired multidrug resistance phenotype could be a useful model for studying the effects of simulated microgravity and testing anticancer drugs.

miR-9-5p Exerts a Dual Role in Cervical Cancer and Targets Transcription Factor TWIST1

Squamous cell carcinoma (SCC) and adenocarcinoma (AC) represent the major cervical cancer histotypes. Both histotypes are caused by infection with high-risk HPV (hrHPV) and are associated with deregulated microRNA expression. Histotype-dependent expression has been observed for miR-9-5p, showing increased expression in SCC and low expression in AC. Here, we studied the regulation and functionality of miR-9-5p in cervical SCCs and ACs using cervical tissue samples and hrHPV-containing cell lines. Expression and methylation analysis of cervical tissues revealed that low levels of miR-9-5p in ACs are linked to methylation of its precursor genes, particularly miR-9-1. Stratification of tissue samples and hrHPV-containing cell lines suggested that miR-9-5p depends on both histotype and hrHPV type, with higher expression in SCCs and HPV16-positive cells. MiR-9-5p promoted cell viability and anchorage independence in cervical cancer cell lines SiHa (SCC, HPV16) and CaSki (metastasized SCC, HPV16), while it played a tumor suppressive role in HeLa (AC, HPV18). TWIST1, a transcription factor involved in epithelial-to-mesenchymal transition (EMT), was established as a novel miR-9-5p target. Our results show that miR-9-5p plays a dual role in cervical cancer in a histotype- and hrHPV type-dependent manner. MiR-9-5p mediated silencing of TWIST1 suggests two distinct mechanisms towards EMT in cervical cancer.

KRAS and BRAF mutations induce anoikis resistance and characteristic 3D phenotypes in Caco‑2 cells

In a number of types of cancer, anoikis, a form of apoptosis induced by loss of extracellular matrix (ECM) attachment, is disturbed. Anoikis resistance is essential in the formation of metastases. A recent study identified carcinoma cell subpopulations surviving without ECM contact in pathological specimens of colorectal cancer. The occurrence of these subpopulations indicated anoikis resistance. In the present study, it is demonstrated that KRAS and BRAF mutations induce anoikis resistance in colon cancer (Caco-2) cells. In 3D cultures, Caco-2 cells transfected with mutated KRAS or BRAF formed multicellular structures analogous to anoikis-resistant subpopulations in actual carcinomas, and serve as an in vitro model for anoikis resistance. Caco-2 cell lines were constructed, with KRAS or BRAF mutations, using retroviral delivery. The current study investigated anoikis resistance using an Annexin V apoptosis test from suspension cultures. 3D in vitro cultures, which were generated in collagen-matrigel mixtures, were assessed using confocal microscopy. 3D cultures embedded in paraffin were analyzed using conventional histopathology. In suspension cultures, Caco-2 cells with KRAS or BRAF mutations indicated a significantly lower proportion of Annexin positivity than the native Caco-2 cells, indicating that these mutations induce anoikis resistance in Caco-2 cells. 3D cultures displayed native Caco-2 cells forming polarized cysts with a single layer thick epithelium, whereas Caco-2 cells with KRAS or BRAF mutations formed partially filled cystic structures or solid round structures where only the outermost layer was in contact with the ECM. Additionally, KRAS mutations induced reversed polarity to Caco-2 cells along with the emergence of solid growth. The present study demonstrated that KRAS and BRAF mutations induce anoikis resistance in Caco-2 colorectal cancer cells. The growth patterns generated from the KRAS and BRAF mutated cells in 3D cultures revealed a resemblance to the putative anoikis-resistant subpopulations in actual carcinomas, including micropapillary structures and solid tumor cell islands. Additionally, KRAS mutation induced the emergence of inverted polarity. In conclusion, 3D cultures with modified Caco-2 cells serve as a valid in vitro model for anoikis resistance and inverted polarity.

The double inhibition of PDK1 and STAT3-Y705 prevents liver metastasis in colorectal cancer

As a key glycolysis enzyme, the significance of pyruvate dehydrogenase kinase 1 (PDK1) in the development of colorectal cancer (CRC) remains unknown. This study revealed that the prognosis of CRC patients with high levels of PDK1 was poor, and PDK1 knockdown significantly reduced liver metastasis of CRC in both nude mice and immune competent BALB/C mice. When combined with cryptotanshinone (CPT), an inhibitor of STAT3-p-Y705, the liver metastasis was further inhibited. PDK1 knockdown obviously increased reactive oxygen species level in anoikis conditions and subsequently resulted in an elevated anoikis, but the combination of PDK1 knockdown and CPT showed a reduced effect on anoikis. Based on this discrepancy, the adherence ability of CRC cells to matrix protein fibronectin was further detected. It showed that PDK1 knockdown significantly decreased the adherence of CRC cells to fibronectin when combined with CPT. These results suggest that inhibition of PDK1 can decrease the surviving CRC cells in blood circulation via up-regulation of anoikis, and inhibition of STAT3-p-Y705 can prevent it to settle down on the liver premetastatic niche, which ultimately reduces liver metastasis.

Metastatic Melanoma Cells Rely on Sestrin2 to Acquire Anoikis Resistance via Detoxifying Intracellular ROS

Distant metastases are responsible for the majority of melanoma mortalities. As a critical barrier against metastasis, anoikis is a distinct programmed cell death induced by the integrated stress from extracellular matrix (ECM) detachment. In order to survive, tumor cells employ various strategies for overcoming this barrier. Recently, Sesn2 has been reported to play a protective role against integrated stress. In this study, we found that ECM detachment triggered the upregulation of Sesn2 in metastatic melanoma cells. The knockdown of Sesn2 impaired not only the cell viability but also the tumor sphere formation of melanoma cells in suspension cultures. Moreover, an elevated oxidative stress level was detected in Sesn2-silencing melanoma cells in suspension cultures, accompanied with an increased apoptosis rate. Finally, in vivo studies indicated that the Sesn2-knockdown reduced the formation of distant metastasis remarkably. Taken together, our findings illustrated that the upregulation of Sesn2 in response to suspension stress plays a protective role in melanoma against anoikis by detoxifying oxidative stress.

Alphavbeta3 integrin blocking inhibits apoptosis and induces autophagy in murine breast tumor cells

Integrins are cell receptors that mediate adhesion to the extracellular matrix (ECM) and regulate cell migration, a crucial process in tumor invasion. The α_vβ₃ integrin recognizes the arginine-glycine-aspartic acid (RGD) motif in ECM proteins and it can be antagonized by RGD-peptides, resulting in decreased cell migration and invasion. RGD-based drugs have shown disappointing results in clinical trials; however, the reasons for their lack of activity are still obscure. Aiming to contribute to a better understanding of the molecular consequences of integrin inhibition, we tested a recombinant RGD-disintegrin (DisBa-01) in two types of murine cell lines, breast tumor 4T1BM2 cells and L929 fibroblasts. Only tumor cells showed decreased motility and adhesion, as well as morphologic alterations upon DisBa-01 treatment (100 and 1000 nM). This result was attributed to the higher levels of α_vβ₃ integrin in 4T1BM2 cells compared to L929 fibroblasts making the former more sensitive to DisBa-01 blocking. DisBa-01 induced cell cycle arrest at the S phase in 4T1BM2 cells, but it did not induce apoptosis, which was consistent with the decrease in caspase-3, 8 and 9 expression at mRNA and protein levels. DisBa-01 increases PI3K, Beclin-1 and LC3B expression in tumor cells, indicators of autophagic induction. In conclusion, α_vβ₃ integrin blocking by DisBa-01 results in inhibition of adhesion and migration and in the activation of an autophagy program, allowing prolonged survival and avoiding immediate apoptotic death. These observations suggest new insights into the effects of RGD-based inhibitors considering their importance in drug development for human health.

Effects of Black Raspberries and Their Constituents on Rat Prostate Carcinogenesis and Human Prostate Cancer Cell Growth In Vitro

Prostate cancer patients often use dietary supplements, such as black raspberries, which are a rich source of compounds with antioxidant and anticancer activity, particularly on gastrointestinal cancers. Feeding black raspberries inhibited mammary cancer induction in rats and growth of cancer cells in nude mice, indicating systemic bioavailability of bioactive compounds. We tested whether feeding black raspberries and its constituents would inhibit prostate cancer development. However, we did not find preventive effects in two rat prostate carcinogenesis models, even though the berry anthocyanin metabolite protocatechuic acid was detectable in their prostates. Black raspberry extract, the anthocyanin cyanidin-3-rutinoside and protocatechuic acid did not inhibit prostate cancer cell growth in vitro, but ellagic acid and its urolithin A metabolite did at high concentrations. Prostate cancer cell migration was not affected by these agents nor was growth in soft agar, except that ellagic acid reduced colony formation at physiological concentrations and protocatechuic acid at high concentrations. Low bioavailability of bioactive berry compounds and metabolites may limit exposure of tissues such as the prostate, since we found that cyanidin-3-rutinoside was not bioavailable to prostate cancer cells, but its aglycone cyanidin was and inhibited their growth. Thus, black raspberries are unlikely to prevent prostate cancer.

Valosin-containing protein promotes metastasis of osteosarcoma through autophagy induction and anoikis inhibition via the ERK/NF-κβ/beclin-1 signaling pathway

Valosin-containing protein (VCP) promotes the development of metastasis in osteosarcoma (OS) via the PI3K/Akt signaling pathway. However, inhibition of the PI3K/Akt pathway does not completely reverse VCP-mediated invasion and migration of OS, suggesting that VCP-mediated OS invasion and migration involves additional mechanisms. In the present study, a positive correlation between the expression of VCP and cell autophagy was observed among OS tissues. Inhibiting VCP may decrease the survival of malignant cells; however, an autophagy stimulator may compensate for VCP inhibition and promote malignant cell survival. Altering the level of autophagy did not affect cell invasiveness or migration. ERK, NF-κβ and beclin-1 protein expression levels were markedly decreased following VCP inhibition. These findings indicated that VCP may induce autophagy and enhance anoikis resistance without affecting cell invasiveness or migration. Via anoikis resistance, VCP may promote metastasis in OS. Therefore, targeting of the ERK/NF-κβ/beclin-1 signaling pathway may be an effective therapeutic strategy for the management of OS.

Jorunnamycin A from Xestospongia sp. Suppresses Epithelial to Mesenchymal Transition and Sensitizes Anoikis in Human Lung Cancer Cells

Metastasis is a key driving force behind the high mortality rate associated with lung cancer. Herein, we report the first study revealing the antimetastasis activity of jorunnamycin A, a bistetrahydroisoquinolinequinone isolated from a Thai blue sponge Xestospongia sp. evidenced by its inhibition of epithelial to mesenchymal transition (EMT), sensitization of anoikis, and suppression of anchorage-independent survival in human lung cancer cells. Treatment with jorunnamycin A (0.05-0.5 μM) altered the expression of p53 and Bcl-2 family proteins, particularly causing the down-regulation of antiapoptosis Bcl-2 and Mcl-1 proteins. Under detachment conditions for 12 h, jorunnamycin A-treated cells exhibited diminution of pro-survival proteins p-Akt and p-Erk as well as the survival-promoting factor caveolin-1. Corresponding with the inhibition on the Akt and Erk pathway as well as activation of p53, there was an increase in the epithelial marker E-cadherin and a remarkable decrease of EMT markers and associated proteins including vimentin, snail, and claudin-1. As the loss of anchorage dependence is an important barrier to metastasis, the observed inhibitory effects of jorunnamycin A on the coordinating networks of EMT and anchorage-independent growth emphasize the potential development of jorunnamycin A as an effective agent against lung cancer metastasis.

Sleeping beauty genetic screen identifies miR-23b::BTBD7 gene interaction as crucial for colorectal cancer metastasis

Background

Metastatic colorectal cancer (CRC) remains a deadly disease. Identifying locally advanced CRC patients with high risk of developing metastasis and improving outcome of metastatic CRC patients require discovering master regulators of metastasis. In this context, the non-coding part of the human genome is still largely unexplored.

Methods

To interrogate the non-coding part of the human genome and disclose regulators of CRC metastasis, we combined a transposon-based forward genetic screen with a novel in vitro assay, which forces cells to grow deprived of cell-substrate and cell-cell contacts (i.e. forced single cell suspension assay - fSCS).

Findings

We proved that fSCS selects CRC cells with mesenchymal and pro-metastatic traits. Moreover, we found that the transposon insertions conferred CRC cells resistance to fSCS and thus metastatic advantage. Among the retrieved transposon insertions, we demonstrated that the one located in the 3′UTR of BTBD7 disrupts miR-23b::BTBD7 interaction and contributes to pro-metastatic traits. In addition, miR-23b and BTBD7 correlate with CRC metastasis both in preclinical experiments and in clinical samples.

Interpretation

fSCS is a simple and scalable in vitro assay to investigate pro-metastatic traits and transposon-based genetic screens can interrogate the non-coding part of the human genome (e.g. miRNA::target interactions). Finally, both Btbd7 and miR-23b represent promising prognostic biomarkers and therapeutic targets in CRC.

Fund

This work was supported by Marie Curie Actions (CIG n. 303877) and Friuli Venezia Giulia region (Grant Agreement n°245574), Italian Association for Cancer Research (AIRC, MFAG n°13589), Italian Ministry of Health (GR-2010-2319387 and PE-2016-02361040) and 5x1000 to CRO Aviano.

The Role of Epithelial-to-Mesenchymal Plasticity in Ovarian Cancer Progression and Therapy Resistance

Ovarian cancer is the most lethal of all gynecologic malignancies and the eighth leading cause of cancer-related deaths among women worldwide. The main reasons for this poor prognosis are late diagnosis; when the disease is already in an advanced stage, and the frequent development of resistance to current chemotherapeutic regimens. Growing evidence demonstrates that apart from its role in ovarian cancer progression, epithelial-to-mesenchymal transition (EMT) can promote chemotherapy resistance. In this review, we will highlight the contribution of EMT to the distinct steps of ovarian cancer progression. In addition, we will review the different types of ovarian cancer resistance to therapy with particular attention to EMT-mediated mechanisms such as cell fate transitions, enhancement of cancer cell survival, and upregulation of genes related to drug resistance. Preclinical studies of anti-EMT therapies have yielded promising results. However, before anti-EMT therapies can be effectively implemented in clinical trials, more research is needed to elucidate the mechanisms leading to EMT-induced therapy resistance.

The expression of S100A8/S100A9 is inducible and regulated by the Hippo/YAP pathway in squamous cell carcinomas

Background

S100A8 and S100A9, two heterodimer-forming members of the S100 family, aberrantly express in a variety of cancer types. However, little is known about the mechanism that regulates S100A8/S100A9 co-expression in cancer cells.

Methods

The expression level of S100A8/S100A9 measured in three squamous cell carcinomas (SCC) cell lines and their corresponding xenografts, as well as in 257 SCC tissues. The correlation between S100A8/S100A9, Hippo pathway and F-actin cytoskeleton were evaluated using western blot, qPCR, ChIP and Immunofluorescence staining tests. IncuCyte ZOOM long time live cell image monitoring system, qPCR and Flow Cytometry measured the effects of S100A8/S100A9 and YAP on cell proliferation, cell differentiation and apoptosis.

Results

Here, we report that through activation of the Hippo pathway, suspension and dense culture significantly induce S100A8/S100A9 co-expression and co-localization in SCC cells. Furthermore, these expressional characteristics of S100A8/S100A9 also observed in the xenografts derived from the corresponding SCC cells. Importantly, Co-expression of S100A8/S100A9 detected in 257 SCC specimens derived from five types of SCC tissues. Activation of the Hippo pathway by overexpression of Lats1, knockdown of YAP, as well as disruption of F-actin indeed obviously results in S100A8/S100A9 co-expression in attached SCC cells. Conversely, inhibition of the Hippo pathway leads to S100A8/S100A9 co-expression in a manner opposite of cell suspension and dense. In addition, we found that TEAD1 is required for YAP-induced S100A8/S100A9-expressions. The functional studies provide evidence that knockdown of S100A8/S100A9 together significantly inhibit cell proliferation but promote squamous differentiation and apoptosis.

Conclusions

Our findings demonstrate for the first time that the expression of S100A8/S100A9 is inducible by changes of cell shape and density through activation of the Hippo pathway in SCC cells. Induced S100A8/S100A9 promoted cell proliferation, inhibit cell differentiation and apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5784-0) contains supplementary material, which is available to authorized users.

SupraCells: Living Mammalian Cells Protected within Functional Modular Nanoparticle-Based Exoskeletons

Creating a synthetic exoskeleton from abiotic materials to protect delicate mammalian cells and impart them with new functionalities could revolutionize fields like cell-based sensing and create diverse new cellular phenotypes. Herein, the concept of "SupraCells," which are living mammalian cells encapsulated and protected within functional modular nanoparticle-based exoskeletons, is introduced. Exoskeletons are generated within seconds through immediate interparticle and cell/particle complexation that abolishes the macropinocytotic and endocytotic nanoparticle internalization pathways that occur without complexation. SupraCell formation is shown to be generalizable to wide classes of nanoparticles and various types of cells. It induces a spore-like state, wherein cells do not replicate or spread on surfaces but are endowed with extremophile properties, for example, resistance to osmotic stress, reactive oxygen species, pH, and UV exposure, along with abiotic properties like magnetism, conductivity, and multifluorescence. Upon decomplexation cells return to their normal replicative states. SupraCells represent a new class of living hybrid materials with a broad range of functionalities.

Lumichrome Inhibits Human Lung Cancer Cell Growth and Induces Apoptosis via a p53-Dependent Mechanism

Lumichrome, a major derivative of riboflavin, may exhibit pharmacological activity against cancer cells. Riboflavin is a vitamin found in food, however, certain evidence has suggested its possible potentiating effects on cancer progression. Here, we have shown for the first time that unlike riboflavin, lumichrome can suppress lung cancer cell growth and reduce survival in both normal and anchorage-independent conditions. In addition, lumichrome induced apoptosis in lung cancer cells via a p53-dependent mitochondrial mechanism with substantial selectivity, shown by its lesser toxicity to the normal primary dermal papilla cells. The potency of lumichrome in killing lung cancer cells was found to be comparable to that of cisplatin, a standard chemotherapeutic drug for lung cancer treatment. With regard to the mechanism, lumichrome significantly upregulated p53 and decreased its downstream target BCL-2. Such a shift of BCL-2 family protein balance further activated caspase-9 and -3 and finally executed apoptosis. Furthermore, lumichrome potentially suppressed cancer stem cells (CSCs) in lung cancer by dramatically suppressing CSC markers together with the CSC-maintaining cell signaling namely protein kinase B (AKT) and β-catenin. To conclude, the present study has unraveled a novel role and mechanism of lumichrome against lung cancer that may benefit the development of the compound for management of the disease.

The Root Bark of Morus alba L. Suppressed the Migration of Human Non-Small-Cell Lung Cancer Cells through Inhibition of Epithelial⁻Mesenchymal Transition Mediated by STAT3 and Src

The root bark of Morus alba L. (MA) has been traditionally used for the treatment of various lung diseases in Korea. Although recent research has demonstrated its anticancer effects in several cancer cells, it is still unclear whether MA inhibits the migratory ability of lung cancer cells. The present study investigated the effects of MA on the migration of lung cancer cells and explored the underlying mechanism. Results from a transwell assay and wound-healing assay demonstrated that methylene chloride extracts of MA (MEMA) suppressed the migration and invasion of H1299, H460, and A549 human non-small-cell lung cancer (NSCLC) cells in a concentration-dependent manner. Results from Western blot analyses showed that MEMA reduced the phosphorylation of STAT3 and Src. In addition, MEMA downregulated the expression of epithelial–mesenchymal transition (EMT) marker proteins including Slug, Snail, Vimentin, and N-cadherin, while upregulating the expression of Occludin—a tight-junction protein. The regulation of EMT markers and the decrease of migration by MEMA treatment were reversed once phospho-mimetic STAT3 (Y705D) or Src (Y527F) was transfected into H1299 cells. In conclusions, MEMA inhibited the migratory activity of human NSCLC cells through blocking Src/STAT3-mediated EMT.

Heparan sulfate proteoglycans as trastuzumab targets in anoikis-resistant endothelial cells

Anoikis is a form of programmed cell death induced by loss of contact from neighboring cells or from their extracellular matrix (ECM). Many tumorigenic cells are anoikis resistant, facilitating cancer progression and metastasis. Trastuzumab is a monoclonal antibody used for the treatment of breast and gastric cell cancer, but its mechanism of action is not well elucidated and its target molecules not well defined. Heparan sulfate proteoglycans (HSPGs) and glycosaminoglycans (GAGs) play important roles in tumor development and in response of cancer cells to drugs. This study investigates the effect of trastuzumab on the expression of HSPGs and sulfated glycosaminoglycans (SGAGs) in anoikis-resistant endothelial cells. After trastuzumab treatment, endothelial cells resistant to anoikis show an increase in adhesion to fibronectin followed by a decrease in invasion, proliferation, and angiogenic capacity. In addition, a significant increase in the number of cells in the S phase of the cell cycle was also observed. In relation to HSPGs and SGAGs expression, we observed a decrease in syndecan-4 and perlecan expression, as well as in the heparan sulfate biosynthesis in anoikis-resistant endothelial cells after exposure to trastuzumab. Our results suggest that trastuzumab interacts with GAGs and proteoglycans of the cell surface and ECM and through this interaction controls cellular events in anoikis-resistant endothelial cells.

Placenta-conditioned extracellular matrix (ECM) activates breast cancer cell survival mechanisms: A key for future distant metastases

The extracellular matrix (ECM) affects cancer cell characteristics. Inability of normal epithelial cells to attach to the ECM induces apoptosis (anoikis). Cancer cells are often anoikis resistant, a prerequisite for their metastatic spread. Previously we demonstrated that the placenta manipulates its surrounding ECM in a way that prevents breast cancer cells (BCCL) attachment and induces their motility and aggregation. This fits with the fact that although breast cancer during pregnancy is often advanced, metastasis to the placenta is rarely observed. Placental intervillous space provides suitable conditions for cancer cell arrival. Yet, the outcome of the short communication between the placental ECM to the BCCL and its effect on BCCL malignant potential are unknown, and are the focus of our study. In the current study we analyzed the effect of placental ECM on BCCL survival pathways and drug resistance. Microarray analysis suggested activation of the NF-κB and stress response pathways. Indeed, the placenta-conditioned ECM induced autophagy in ERα + BCCL, inactivated the NF-κB inhibitor (IκB) and increased integrin α5 in the BCCL. The autophagy mediated MCF-7 and T47D migration and the placental ECM-BCCL interactions reduced the BCCL sensitivity to Taxol. We also demonstrated by using siRNA that integrin α5 was responsible for the MCF-7 autophagy and suggest this molecule as a suitable target for therapy.

Autophagy: Supporting cellular and organismal homeostasis by self-eating

Autophagy is a conserved catabolic process that delivers cytoplasmic components and organelles to lysosomes for degradation and recycling. This pathway serves to degrade nonfunctional organelles and aggregate-prone proteins, as well as to produce substrates for energy production and biosynthesis. Autophagy is especially important for the maintenance of stem cells, and for the survival and homeostasis of post-mitotic cells like neurons. Functional autophagy promotes longevity in several model organisms. Autophagy regulates immunity and inflammation at several levels and has both anti- and pro-tumorigenic roles in cancer. This review provides a concise overview of autophagy and its importance in cellular and organismal homeostasis, with emphasis on aging, stem cells, neuronal cells, immunity, inflammation, and cancer.

Predicting cancer cell invasion by single-cell physical phenotyping

The physical properties of cells are promising biomarkers for cancer diagnosis and prognosis. Here we determine the physical phenotypes that best distinguish human cancer cell lines, and their relationship to cell invasion. We use the high throughput, single-cell microfluidic method, quantitative deformability cytometry (q-DC), to measure six physical phenotypes including elastic modulus, cell fluidity, transit time, entry time, cell size, and maximum strain at rates of 102 cells per second. By training a k-nearest neighbor machine learning algorithm, we demonstrate that multiparameter analysis of physical phenotypes enhances the accuracy of classifying cancer cell lines compared to single parameters alone. We also discover a set of four physical phenotypes that predict invasion; using these four parameters, we generate the physical phenotype model of invasion by training a multiple linear regression model with experimental data from a set of human ovarian cancer cells that overexpress a panel of tumor suppressor microRNAs. We validate the model by predicting invasion based on measured physical phenotypes of breast and ovarian human cancer cell lines that are subject to genetic or pharmacologic perturbations. Taken together, our results highlight how physical phenotypes of single cells provide a biomarker to predict the invasion of cancer cells.

Silencing of EPHB2 promotes the epithelial-mesenchymal transition of skin squamous cell carcinoma-derived A431 cells

Erythropoietin-producing hepatocellular (Eph) receptors and their ligand ephrins serve crucial roles in the interactions among epithelial cells. Eph receptor/ephrin signaling regulates cell functions, including proliferation, differentiation and migration, via these cell-cell interactions. We reported previously that EPHB2, a member of the Eph receptor family, was highly expressed in chemically induced cutaneous squamous cell carcinoma (cSCC) tissues in mice. Although the higher expression level of EPHB2 has been observed in various human cancers, its roles in the development and progression of cancers are still unclear. In the present study, the functional implications of EPHB2 in the acquisition of malignant phenotypes of cSCC cells was investigated. Silencing of EPHB2 in the human cSCC cell line A431 induced epithelial-mesenchymal transition (EMT)-like morphological changes accompanied by a significant upregulation of epithelial-mesenchymal transition-associated genes such as zinc finger E-box binding homeobox 1/2. In addition, silencing of EPHB2 suppressed anchorage-independent cell growth under 3D culture conditions. Consistent with these observations, EPHB2 exhibited higher levels of expression in tumor spheres formed under 3D culture conditions than in cells cultured in adherent form, and the expression pattern of EMT markers indicated that EMT was suppressed in tumor spheres. The results of the present study indicated that EPHB2 serves a pivotal role in promoting the anchorage-independent growth of A431 cells through the suppression of EMT.

Exosomes Derived from Human Primary and Metastatic Colorectal Cancer Cells Contribute to Functional Heterogeneity of Activated Fibroblasts by Reprogramming Their Proteome

Cancer-associated fibroblasts (CAFs) are a heterogeneous population of activated fibroblasts that constitute a dominant cellular component of the tumor microenvironment (TME) performing distinct functions. Here, the role of tumor-derived exosomes (Exos) in activating quiescent fibroblasts into distinct functional subtypes is investigated. Proteomic profiling and functional dissection reveal that early- (SW480) and late-stage (SW620) colorectal cancer (CRC) cell-derived Exos both activated normal quiescent fibroblasts (α-SMA^- , CAV⁺ , FAP⁺ , VIM⁺ ) into CAF-like fibroblasts (α-SMA⁺ , CAV^- , FAP⁺ , VIM⁺ ). Fibroblasts activated by early-stage cancer-exosomes (SW480-Exos) are highly pro-proliferative and pro-angiogenic and display elevated expression of pro-angiogenic (IL8, RAB10, NDRG1) and pro-proliferative (SA1008, FFPS) proteins. In contrast, fibroblasts activated by late-stage cancer-exosomes (SW620-Exos) display a striking ability to invade through extracellular matrix through upregulation of pro-invasive regulators of membrane protrusion (PDLIM1, MYO1B) and matrix-remodeling proteins (MMP11, EMMPRIN, ADAM10). Conserved features of Exos-mediated fibroblast activation include enhanced ECM secretion (COL1A1, Tenascin-C/X), oncogenic transformation, and metabolic reprogramming (downregulation of CAV-1, upregulation of glycogen metabolism (GAA), amino acid biosynthesis (SHMT2, IDH2) and membrane transporters of glucose (GLUT1), lactate (MCT4), and amino acids (SLC1A5/3A5)). This study highlights the role of primary and metastatic CRC tumor-derived Exos in generating phenotypically and functionally distinct subsets of CAFs that may facilitate tumor progression.

Methods for Assessing Apoptosis and Anoikis in Normal Intestine/Colon and Colorectal Cancer

Caspase-dependent apoptosis, including its distinct cell death subroutine known as anoikis, perform essential roles during organogenesis, as well as in the maintenance and repair of tissues. To this effect, the continuous renewal of the human intestinal/colon epithelium is characterized by the exfoliation by anoikis of differentiated cells, whereas immature/undifferentiated cells may occasionally undergo apoptosis in order to evacuate daughter cells that are damaged or defective. Dysregulated epithelial apoptosis is a significant component of inflammatory bowel diseases. Conversely, the acquisition of a resistance to apoptosis represents one of the hallmarks of cancer initiation and progression, including for colorectal cancer (CRC). Furthermore, the emergence of anoikis resistance constitutes a critical step in cancer progression (including CRC), as well as a limiting one that enables invasion and metastasis.Considering the implications of apoptosis/anoikis dysregulation in gut physiopathology, it therefore becomes incumbent to understand the functional determinants that underlie such dysregulation-all the while having to monitor, assess, or evidence apoptosis and/or anoikis. In this chapter, methodologies that are typically used to assess caspase-dependent apoptosis and anoikis in intestinal/colonic normal and CRC cells, whether in vivo, ex vivo, or in cellulo, are provided.

ADAM9 contributes to vascular invasion in pancreatic ductal adenocarcinoma

A disintegrin and a metalloprotease (ADAM)‐9 is a metzincin cell‐surface protease with strongly elevated expression in solid tumors, including pancreatic ductal adenocarcinoma (PDAC). In this study, we performed immunohistochemistry (IHC) of a tissue microarray (TMA) to examine the expression of ADAM9 in a cohort of >100 clinically annotated PDAC cases. We report that ADAM9 is prominently expressed by PDAC tumor cells, and increased ADAM9 expression levels correlate with poor tumor grading (P = 0.027) and the presence of vasculature invasion (P = 0.017). We employed gene expression silencing to generate a loss‐of‐function system for ADAM9 in two established PDAC cell lines. In vitro analysis showed that loss of ADAM9 does not impede cellular proliferation and invasiveness in basement membrane. However, ADAM9 plays a crucial role in mediating cell migration and adhesion to extracellular matrix substrates such as fibronectin, tenascin, and vitronectin. This effect appears to depend on its catalytic activity. In addition, ADAM9 facilitates anchorage‐independent growth. In AsPC1 cells, but not in MiaPaCa‐2 cells, we noted a pronounced yet heterogeneous impact of ADAM9 on the abundance of various integrins, a process that we characterized as post‐translational regulation. Sprout formation of human umbilical vein endothelial cells (HUVECs) is promoted by ADAM9, as examined by transfer of cancer cell conditioned medium; this finding further supports a pro‐angiogenic role of ADAM9 expressed by PDAC cancer cells. Immunoblotting analysis of cancer cell conditioned medium highlighted that ADAM9 regulates the levels of angiogenic factors, including shed heparin‐binding EGF‐like growth factor (HB‐EGF). Finally, we carried out orthotopic seeding of either wild‐type AsPC‐1 cells or AsPC‐1 cells with silenced ADAM9 expression into murine pancreas. In this in vivo setting, ADAM9 was also found to foster angiogenesis without an impact on tumor cell proliferation. In summary, our results characterize ADAM9 as an important regulator in PDAC tumor biology with a strong pro‐angiogenic impact.

Engineered In Vitro Models of Tumor Dormancy and Reactivation

Metastatic recurrence is a major hurdle to overcome for successful control of cancer-associated death. Residual tumor cells in the primary site, or disseminated tumor cells in secondary sites, can lie in a dormant state for long time periods, years to decades, before being reactivated into a proliferative growth state. The microenvironmental signals and biological mechanisms that mediate the fate of disseminated cancer cells with respect to cell death, single cell dormancy, tumor mass dormancy and metastatic growth, as well as the factors that induce reactivation, are discussed in this review. Emphasis is placed on engineered, in vitro, biomaterial-based approaches to model tumor dormancy and subsequent reactivation, with a focus on the roles of extracellular matrix, secondary cell types, biochemical signaling and drug treatment. A brief perspective of molecular targets and treatment approaches for dormant tumors is also presented. Advances in tissue-engineered platforms to induce, model, and monitor tumor dormancy and reactivation may provide much needed insight into the regulation of these processes and serve as drug discovery and testing platforms.

Aggregatibacter actinomycetemcomitans leukotoxin causes activation of lymphocyte function-associated antigen 1

Repeats-in-toxin leukotoxin (LtxA) produced by the oral bacterium Aggregatibacter actinomycetemcomitans kills human leukocytes in a lymphocyte function-associated antigen 1 (LFA-1, integrin α_L /β₂ )-dependent manner, although the mechanism for this interaction has not been identified. The LtxA internalisation by LFA-1-expressing cells was explored with florescence resonance energy transfer (FRET) microscopy using a cell line that expresses LFA-1 with a cyan fluorescent protein-tagged cytosolic α_L domain and a yellow fluorescent protein-tagged β₂ domain. Phorbol 12-myristate 13-acetate activation of LFA-1 caused transient cytosolic domain separation. However, addition of LtxA resulted in an increase in FRET, indicating that LtxA brings the cytosolic domains closer together, compared with the inactive state. Unlike activation, this effect was not transient, lasting more than 30 min. Equilibrium constants of LtxA binding to the cytoplasmic domains of both α_L and β₂ were determined using surface plasmon resonance. LtxA has a strong affinity for the cytosolic domains of both the α_L and β₂ subunits (K_d  = 15 and 4.2 nM, respectively) and a significantly lower affinity for the cytoplasmic domains of other integrin α_M , α_X , and β₃ subunits (K_d  = 400, 180, and 230 nM, respectively), used as controls. Peptide fragments of α_L and β₂ show that LtxA binds membrane-proximal domain of α_L and intermediate domain of β₂ .