Excessive hyaluronan production promotes acquisition of cancer stem cell signatures through the coordinated regulation of Twist and the transforming growth factor β (TGF-β)-Snail signaling axis

Etoposide loaded layered double hydroxide nanoparticles reversing chemoresistance and eradicating human glioma stem cells in vitro and in vivo

Glioblastoma (GBM) is the most malignant and lethal glioma in human brain tumors and contains self-renewing, tumorigenic glioma stem cells (GSCs) that contribute to tumor initiation, therapeutic resistance and further recurrence. In this study, we combined in vitro cellular efficacy with in vivo antitumor performance to evaluate the outcome of an etoposide (VP16) loaded layered double hydroxide (LDH) nanocomposite (L-V) on human GSCs. The effects on GSC proliferation and apoptosis showed that loading with LDH could significantly sensitize GSCs to VP16 and enhance the GSC elimination. Further qPCR and western blot assays demonstrated that L-V could effectively attenuate GSC related pluripotency gene expression and reduce the cancer stemness. An in vivo GSC xenograft mice model showed that L-V can overcome drug resistance, eradicate GSCs, sharply decrease the stemness and reverse the epithelial-mesenchymal transition (EMT). RNA-seq analysis elucidated that L-V plays a vital role by down-regulating the PI3K/AKt/mTOR expression and activating the Wnt/GSK3β/β-catenin signaling pathway, hence leading to GSC stemness loss and greatly enhancing the GSC targeting effect. Taken together, this study demonstrated the outstanding performance of L-V reversing the drug resistance of GSCs, thus providing a novel strategy for clinical translation application of nanomedicine in malignant glioma chemotherapy.

Virtual screening-driven repositioning of etoposide as CD44 antagonist in breast cancer cells

CD44 is a receptor for hyaluronan (HA) that promotes epithelial-to-mesenchymal transition (EMT), induces cancer stem cell (CSC) expansion, and favors metastasis. Thus, CD44 is a target for the development of antineoplastic agents. In order to repurpose drugs as CD44 antagonists, we performed consensus-docking studies using the HA-binding domain of CD44 and 11,421 molecules. Drugs that performed best in docking were examined in molecular dynamics simulations, identifying etoposide as a potential CD44 antagonist. Ligand competition and cell adhesion assays in MDA-MB-231 cells demonstrated that etoposide decreased cell binding to HA as effectively as a blocking antibody. Etoposide-treated MDA-MB-231 cells developed an epithelial morphology; increased their expression of E-cadherin; and reduced their levels of EMT-associated genes and cell migration. By gene expression analysis, etoposide reverted an EMT signature similarly to CD44 knockdown, whereas other topoisomerase II (TOP2) inhibitors did not. Moreover, etoposide decreased the proportion of CD44⁺/CD24⁻ cells, lowered chemoresistance, and blocked mammosphere formation. Our data indicate that etoposide blocks CD44 activation, impairing key cellular functions that drive malignancy, thus rendering it a candidate for further translational studies and a potential lead compound in the development of new CD44 antagonists.

Regulation of hyaluronan biosynthesis and clinical impact of excessive hyaluronan production

The tightly regulated biosynthesis and catabolism of the glycosaminoglycan hyaluronan, as well as its role in organizing tissues and cell signaling, is crucial for the homeostasis of tissues. Overexpression of hyaluronan plays pivotal roles in inflammation and cancer, and markedly high serum and tissue levels of hyaluronan are noted under such pathological conditions. This review focuses on the complexity of the regulation at transcriptional and posttranslational level of hyaluronan synthetic enzymes, and the outcome of their aberrant expression and accumulation of hyaluronan in clinical conditions, such as systemic B-cell cancers, aggressive breast carcinomas, metabolic diseases and virus infection.

TGF‑β signaling: A complex role in tumorigenesis (Review)

Tumor progression can be affected by various cellular components of tumor cells and/or by tumor microenvironmental factors. The tumor microenvironment comprises a variety of nonmalignant stromal cells and inflammatory cytokines, which are pivotal in tumor promotion and progression. The transforming growth factor‑β (TGF‑β) ligands (TGF‑β1, 2 and 3) are secreted inflammatory cytokines, which are known to be involved in various aspects of tumor development through two transmembrane serine‑threonine kinase receptors, TGFβR1 and TGFβR2. TGF‑β promotes or inhibits tumorigenesis depending on the concurrent gene mutations and tissue microenvironment present through the small mothers against decapentaplegic (Smad) and non‑Smad pathways. This review aims to provide a comprehensive overview of the role of the TGF‑β pathway in tumor initiation and progression.

Role of Pericellular Matrix in the Regulation of Cancer Stemness

Cancer stem cells (CSC) are a prominent component of the tumor bulk and extensive research has now identified them as the subpopulation responsible for tumor relapse and resistance to anti-cancer treatments. Surrounding the bulk formed of tumor cells, an extracellular matrix contributes to cancer growth; the main component of the tumor micro-environment is hyaluronan, a large disaccharide forming a molecular network surrounding the cells. The hyaluronan-dependent coat can regulate cell division and motility in cancer progression and metastasis. One of the receptors of hyaluronan is CD44, a surface protein frequently used as a CSC marker. Indeed, tumor cells with high levels of CD44 appear to exhibit CSC properties and are characterized by elevated relapse rate. The CD44-hyaluronan-dependent interactions are Janus-faced: on one side, they have been shown to be crucial in both malignancy and resistance to therapy; on the other, they represent a potential value for future therapies, as disturbing the CD44-hyaluronan axis would not only impair the pericellular matrix but also the subpopulation of self-renewing oncogenic cells. Here, we will review the key roles of HA and CD44 in CSC maintenance and propagation and will show that CSC-like spheroids from a rabdhomyosarcoma cell line, namely RD, have a prominent pericellular coat necessary for sphere formation and for elevated migration. Thus, a better understanding of the hyaluronan-CD44 interactions holds the potential for ameliorating current cancer therapies and eradicating CSC.

A novel ZEB1/HAS2 positive feedback loop promotes EMT in breast cancer

Cancer metastasis is the main reason for poor patient survival. Tumor cells delaminate from the primary tumor by induction of epithelial-mesenchymal transition (EMT). EMT is mediated by key transcription factors, including ZEB1, activated by tumor cell interactions with stromal cells and the extracellular matrix (ECM). ZEB1-mediated EMT and motility is accompanied by substantial cell reprogramming and the acquisition of a stemness phenotype. However, understanding of the underlying mechanism is still incomplete. We identified hyaluronic acid (HA), one major ECM proteoglycan and enriched in mammary tumors, to support EMT and enhance ZEB1 expression in cooperation with CD44s. In breast cancer cell lines HA is synthesized mainly by HAS2, which was already shown to be implicated in cancer progression. ZEB1 and HAS2 expression strongly correlates in various cancer entities and high HAS2 levels associate with an early relapse. We identified HAS2, tumor cell-derived HA and ZEB1 to form a positive feedback loop as ZEB1, elevated by HA, directly activates HAS2 expression. In an in vitro differentiation model HA-conditioned medium of breast cancer cells is enhancing osteoclast formation, an indicator of tumor cell-induced osteolysis that facilitates formation of bone metastasis. In combination with the previously identified ZEB1/ESRP1/CD44s feedback loop, we found a novel autocrine mechanism how ZEB1 is accelerating EMT.

Epithelial-mesenchymal transition and cancer stem cell-like phenotype induced by Twist1 contribute to acquired resistance to irinotecan in colon cancer

Inherent and acquired chemoresistance reduce the effectiveness of irinotecan in the treatment of metastatic colorectal cancer (CRC). However, the molecular mechanisms underlying this resistance process are still unclear. Twist1 is one of the master transcription factors of epithelial-mesenchymal transition (EMT). Our previous study indicated that Twist1 is overexpressed in colon cancer tissues, and demonstrated that Twist1 plays a crucial role in the chemoresistance of CRC. In the present study, we further investigated how Twist1 contribute to acquired resistance to irinotecan in colon cancer. The irinotecan-resistant cells were established by gradual adaptation of increasing irinotecan concentrations in LoVo cells, named LoVo/CPT-11R cells. Results showed that cell viabilities to different anticancer drugs were markedly increased in LoVo/CPT-11R cells compared to LoVo cells. Moreover, LoVo/CPT-11R cells displayed EMT, CSC-like cellular morphology and relative biomarkers were also significantly increased. In addition, overexpressed Twist1 LoVo cells were established by lentivirus transfection assay, named LoVo/Twist1 cells. Results showed that the LoVo/Twist1 cells perform a distinctly decreased sensitivity to irinotecan, downregulated expression of E-cadherin, upregulated expression of cluster of differentiation 44 (CD44), and a significant enhancement of invasion and migration potential by regulation of MMP2 compared with control cells. In contrast, the inhibition of Twist1 transfected with siRNA could enhance the irinotecan sensitivity in LoVo/CPT-11R cells and downregulate the expression of vimentin and CD44. Our data provide evidence that EMT and CSC-like phenotype induced by Twist1 contribute to acquire resistance to irinotecan and enhanced migration and invasion in colon cancer.

The deubiquitinating enzymes USP4 and USP17 target hyaluronan synthase 2 and differentially affect its function

The levels of hyaluronan, a ubiquitous glycosaminoglycan prominent in the extracellular matrix, is balanced through the actions of hyaluronan-synthesizing enzymes (HAS1, 2 and 3) and degrading hyaluronidases (Hyal 1, 2, 3 and PH20). Hyaluronan accumulates in rapidly remodeling tissues, such as breast cancer, due to deregulated expression of the HAS2 gene and/or alterations of HAS2 activity. The activity of HAS2 is regulated by post-translational modifications, including ubiquitination. In order to identify deubiquitinating enzymes (DUBs) that are involved in de-ubiquitination of HAS2, a complementary (cDNA) library of 69 Flag-HA-tagged human DUBs cloned into retroviral vectors was screened in human embryonic kidney (HEK) 293T cells for their ability to de-ubiquitinate myc-tagged HAS2. Several DUBs were found to decrease the ubiquitination of 6myc-HAS2, among which, the most effective were USP17 and USP4. USP17 efficiently removed polyubiquitination, whereas USP4 preferentially removed monoubiquitination of 6myc-HAS2. Co-immunoprecipitation studies revealed interactions between HAS2 and USP17, as well as between HAS2 and USP4, in membrane preparations of HEK293T cells. USP17 significantly stabilized 6myc-HAS2 protein levels, whereas USP4 did not. The silencing of USP17 led to decreased hyaluronan production, whereas the suppression of USP4 increased hyaluronan synthesis. Importantly, high levels of USP17 and HAS2 were detected in a panel of cancer cell lines compared to normal cells, and immunohistochemical stainings revealed higher expression of USP17 and HAS2 in tissues of lung cancer patients compared to normal tissue. In conclusion, USP17 and USP4 differently affect HAS2 ubiquitination, and the stability and function of HAS2.

Long noncoding RNA HAS2-AS1 mediates hypoxia-induced invasiveness of oral squamous cell carcinoma

A hypoxic microenvironment plays important roles in the progression of solid tumors, including oral squamous cell carcinoma (OSCC). Long noncoding RNAs (lncRNAs) have gained much attention in the past few years. However, it is not clear whether lncRNAs can regulate hypoxia adaptation of OSCC or which lncRNAs participate in this process. Using a lncRNA microarray, we analyzed the aberrant lncRNA expression profiles in OSCC tissues compared with paired normal oral mucosa and in hypoxic OSCC cells compared with normoxic OSCC cells. The top 10 lncRNAs that had more than threefold increase with P-value <0.01 in both microarray data were validated by qRT-PCR. Among the top 10 lncRNAs, hyaluronan synthase 2 antisense 1 (HAS2-AS1) was the only one that has a hypoxia-responsive element (HRE) on its promoter region and has been validated to increase in OSCC tissues and in cells cultured under hypoxia. Tumor HAS2-AS1 levels were closely associated with lymph node metastasis and hypoxic tumor status in patients with OSCC. Moreover, the hypoxia-induced HAS2-AS1 expression is dependent on HIF-1α which directly binds to and activates the transcription of HAS2-AS1. In addition, HAS2-AS1 mediates hypoxia-induced epithelial mesenchymal transition of OSCC cells via stabilizing HAS2. In conclusion, our results suggest that hypoxia would induce an overexpression of HAS2-AS1 in an HIF-1α dependent manner. The increase of HAS2-AS1 plays important roles mediating the hypoxia-regulated EMT and invasiveness of OSCC.

Akt Signaling Is Sustained by a CD44 Splice Isoform-Mediated Positive Feedback Loop

Tumor cells nearly invariably evolve sustained PI3K/Akt signaling as an effective means to circumvent apoptosis and maintain survival. However, for those tumor cells that do not acquire PI3K/Akt mutations to achieve this end, the underlying mechanisms have remained obscure. Here, we describe the discovery of a splice isoform-dependent positive feedback loop that is essential to sustain PI3K/Akt signaling in breast cancer. Splice isoform CD44s promoted expression of the hyaluronan synthase HAS2 by activating the Akt signaling cascade. The HAS2 product hyaluronan further stimulated CD44s-mediated Akt signaling, creating a feed-forward signaling circuit that promoted tumor cell survival. Mechanistically, we identified FOXO1 as a bona fide transcriptional repressor of HAS2. Akt-mediated phosphorylation of FOXO1 relieved its suppression of HAS2 transcription, with FOXO1 phosphorylation status maintained by operation of the positive feedback loop. In clinical specimens of breast cancer, we established that the expression of CD44s and HAS2 was positively correlated. Our results establish a positive feedback mechanism that sustains PI3K/Akt signaling in tumor cells, further illuminating the nearly universal role of this pathway in cancer cell survival. Cancer Res; 77(14); 3791-801. ©2017 AACR.

HYAL-2-WWOX-SMAD4 Signaling in Cell Death and Anticancer Response

Hyaluronidase HYAL-2 is a membrane-anchored protein and also localizes, in part, in the lysosome. Recent study from animal models revealed that both HYAL-1 and HYAL-2 are essential for the metabolism of hyaluronan (HA). Hyal-2 deficiency is associated with chronic thrombotic microangiopathy with hemolytic anemia in mice due to over accumulation of high molecular size HA. HYAL-2 is essential for platelet generation. Membrane HYAL-2 degrades HA bound by co-receptor CD44. Also, in a non-canonical signal pathway, HYAL-2 serves as a receptor for transforming growth factor beta (TGF-β) to signal with downstream tumor suppressors WWOX and SMAD4 to control gene transcription. When SMAD4 responsive element is overly driven by the HYAL-2–WWOX–SMAD4 signaling complex, cell death occurs. When rats are subjected to traumatic brain injury, over accumulation of a HYAL-2–WWOX complex occurs in the nucleus to cause neuronal death. HA induces the signaling of HYAL-2–WWOX–SMAD4 and relocation of the signaling complex to the nucleus. If the signaling complex is overexpressed, bubbling cell death occurs in WWOX-expressing cells. In addition, a small synthetic peptide Zfra (zinc finger-like protein that regulates apoptosis) binds membrane HYAL-2 of non-T/non-B spleen HYAL-2⁺ CD3⁻ CD19⁻ Z lymphocytes and activates the cells to generate memory anticancer response against many types of cancer cells in vivo. Whether the HYAL-2–WWOX–SMAD4 signaling complex is involved is discussed. In this review and opinion article, we have updated the current knowledge of HA, HYAL-2 and WWOX, HYAL-2–WWOX–SMAD4 signaling, bubbling cell death, and Z cell activation for memory anticancer response.

Reengineering the Tumor Microenvironment to Alleviate Hypoxia and Overcome Cancer Heterogeneity

Solid tumors consist of cancer cells and stromal cells, including resident and transiting immune cells-all ensconced in an extracellular matrix (ECM)-nourished by blood vessels and drained by lymphatic vessels. The microenvironment constituents are abnormal and heterogeneous in morphology, phenotype, and physiology. Such irregularities include an inefficient tumor vascular network comprised of leaky and compressed vessels, which impair blood flow and oxygen delivery. Low oxygenation in certain tumor regions-or focal hypoxia-is a mediator of cancer progression, metastasis, immunosuppression, and treatment resistance. Thus, repairing an abnormal and heterogeneous microenvironment-and hypoxia in particular-can significantly improve treatments of solid tumors. Here, we summarize two strategies to reengineer the tumor microenvironment (TME)-vessel normalization and decompression-that can alleviate hypoxia. In addition, we discuss how these two strategies alone and in combination with each other-or other therapeutic strategies-may overcome the challenges posed by cancer heterogeneity.

Roles and targeting of the HAS/hyaluronan/CD44 molecular system in cancer

Synthesis, deposition, and interactions of hyaluronan (HA) with its cellular receptor CD44 are crucial events that regulate the onset and progression of tumors. The intracellular signaling pathways initiated by HA interactions with CD44 leading to tumorigenic responses are complex. Moreover, HA molecules may perform dual functions depending on their concentration and size. Overexpression of variant isoforms of CD44 (CD44v) is most commonly linked to cancer progression, whereas their loss is associated with inhibition of tumor growth. In this review, we highlight that the regulation of HA synthases (HASes) by post-translational modifications, such as O-GlcNAcylation and ubiquitination, environmental factors and the action of microRNAs is important for HA synthesis and secretion in the tumor microenvironment. Moreover, we focus on the roles and interactions of CD44 with various proteins that reside extra- and intracellularly, as well as on cellular membranes with particular reference to the CD44-HA axis in cancer stem cell functions, and the importance of CD44/CD44v6 targeting to inhibit tumorigenesis.

Hyaluronan Production Regulates Metabolic and Cancer Stem-like Properties of Breast Cancer Cells via Hexosamine Biosynthetic Pathway-coupled HIF-1 Signaling

Cancer stem cells (CSCs) represent a small subpopulation of self-renewing oncogenic cells. As in many other stem cells, metabolic reprogramming has been implicated to be a key characteristic of CSCs. However, little is known about how the metabolic features of cancer cells are controlled to orchestrate their CSC-like properties. We recently demonstrated that hyaluronan (HA) overproduction allowed plastic cancer cells to revert to stem cell states. Here, we adopted stable isotope-assisted tracing and mass spectrometry profiling to elucidate the metabolic features of HA-overproducing breast cancer cells. These integrated approaches disclosed an acceleration of metabolic flux in the hexosamine biosynthetic pathway (HBP). A metabolic shift toward glycolysis was also evident by quantitative targeted metabolomics, which was validated by the expression profiles of key glycolytic enzymes. Forced expression of glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), an HBP rate-limiting enzyme, resembled the results of HA overproduction with regard to HIF-1α accumulation and glycolytic program, whereas GFAT1 inhibition significantly decreased HIF-1α protein level in HA-overproducing cancer cells. Moreover, inhibition of the HBP-HIF-1 axis abrogated HA-driven glycolytic enhancement and reduced the CSC-like subpopulation. Taken together, our results provide compelling evidence that HA production regulates the metabolic and CSC-like properties of breast cancer cells via HBP-coupled HIF-1 signaling.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Mechanisms of TGFβ-Induced Epithelial-Mesenchymal Transition

Transitory phenotypic changes such as the epithelial–mesenchymal transition (EMT) help embryonic cells to generate migratory descendants that populate new sites and establish the distinct tissues in the developing embryo. The mesenchymal descendants of diverse epithelia also participate in the wound healing response of adult tissues, and facilitate the progression of cancer. EMT can be induced by several extracellular cues in the microenvironment of a given epithelial tissue. One such cue, transforming growth factor β (TGFβ), prominently induces EMT via a group of specific transcription factors. The potency of TGFβ is partly based on its ability to perform two parallel molecular functions, i.e. to induce the expression of growth factors, cytokines and chemokines, which sequentially and in a complementary manner help to establish and maintain the EMT, and to mediate signaling crosstalk with other developmental signaling pathways, thus promoting changes in cell differentiation. The molecules that are activated by TGFβ signaling or act as cooperating partners of this pathway are impossible to exhaust within a single coherent and contemporary report. Here, we present selected examples to illustrate the key principles of the circuits that control EMT under the influence of TGFβ.

Hyaluronan synthase 2 is an adverse prognostic marker in androgen receptor-negative breast cancer

AIMS

The important role of hyaluronan synthase 2 (HAS2), an isozyme responsible for hyaluronan synthesis, in cancer has been increasingly recognised. However, only a few studies with inconsistent results have been reported in breast cancers. With a large cohort, we aim to determine the clinical significance of HAS2 in breast cancers.

METHODS

We examined HAS2 expression in 1142 breast cancers using immunohistochemistry.

RESULTS

HAS2 was associated with both prognostically favourable (androgen receptor (AR), p<0.001) and unfavourable (basal and epithelial mesenchymal transition markers, p≤0.039) biomarkers. In addition, HAS2 showed differential associations with various features and outcome between AR+ and AR- subgroups. HAS2+AR- breast cancers showed significantly worse outcome than other subgroups, and HAS2+AR- subgroup was an independent adverse prognostic factor for disease-free survival (HR 1.309, p=0.046). Interestingly, HAS2 was associated with many poor prognostic features (including higher grade, lymphovascular invasion, basal-like breast cancer subtype, high Ki67 and basal marker expression) only in AR-, but not AR+ breast cancers.

CONCLUSIONS

HAS2 has been proposed to be a target for therapeutic intervention in cancer. Our findings suggested a possible antagonistic role of AR pathway on HAS2 function. It will be interesting to further investigate their precise interaction, which may have important implication in HAS2 targeting.

A Histone Deacetylase Inhibitor Suppresses Epithelial-Mesenchymal Transition and Attenuates Chemoresistance in Biliary Tract Cancer

Epithelial-mesenchymal transition (EMT) is involved in the characteristics of malignancy, such as invasion, metastasis, and chemoresistance. In biliary tract cancer (BTC), EMT is induced by transforming growth factor-beta 1 (TGF-β1). The EMT is reversible; therefore, it is conceivable that it could be related to some epigenetic changes. We focused on histone deacetylase (HDAC) inhibitors as regulators of TGF-β1 signaling, and investigated their effect on EMT and chemoresistance. We employed four BTC cell lines (MzChA-1, gemcitabine-resistant MzChA-1, TFK-1, and gemcitabine-resistant TFK-1) and used vorinostat as the HDAC inhibitor. The relative mRNA expression of an epithelial marker (CDH1) and mesenchymal markers (CDH2, vimentin, SNAI1) were measured by qRT-PCR to evaluate factors associated with EMT. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was performed to evaluate the chemoresistance of each cell line. In addition, NOD/SCID mice were used to evaluate the effect of vorinostat in vivo. In the parent MzChA-1 and TFK-1 cell lines, TGF-β1 induced EMT and chemoresistance; while vorinostat inhibited the EMT and chemoresistance induced by TGF-β1. In gemcitabine-resistant cell lines that highly expressed TGF-β1, vorinostat inhibited EMT and attenuated chemoresistance. We showed that vorinostat inhibits nuclear translocation of SMAD4 which is a signaling factor of TGF-β1, and this is one of the mechanisms by which vorinostat regulates EMT. We also showed that vorinostat attenuates the binding affinity of SMAD4 to the CDH1-related transcription factors SNAI1, SNAI2, ZEB1, ZEB2, and TWIST. Furthermore, combination therapy with vorinostat and gemcitabine improved survival time in the mice xenografted with gemcitabine resistant MzChA-1 cells. In conclusion, vorinostat regulated TGF-β1-induced EMT and chemoresistance through inhibition of SMAD4 nuclear translocation.

Hyaluronan synthase 2 overexpression is correlated with the tumorigenesis and metastasis of human breast cancer

Extracellular matrix (ECM) is closely correlated with the malignant behavior of breast cancer cells. Hyaluronan (HA) is one of the main components of ECM, and actively regulates cell adhesion, migration and proliferation by interacting with specific cell surface receptors such as CD44 and RHAMM. HA synthase 2 (HAS2) catalyzes the synthesis of HA, but its role in breast tumorigenesis remains unclear. This study assessed the roles of HAS2 in malignant behavior of human breast cancer and sought to provide mechanistic insights into the biological and pivotal roles of HAS2. We observed HAS2 was overexpressed in breast cancer cell lines and invasive duct cancer tissues, compared with the nonmalignant breast cell lines and normal breast tissues. In addition, a high level of HAS2 expression was statistically correlated with lymph node metastasis. Functional assays showed that knockdown of HAS2 expression inhibited breast tumor cell proliferation in vivo and in vitro, through the induction of apoptosis or cell cycle arrest. Further studies showed that the HA were elevated in breast cancer, and HAS2 could upregulate HA expression. In conclusion, HAS2-HA system influences the biological characteristics of human breast cancer cells, and HAS2 may be a potential prognostic marker and therapeutic target in breast cancer.

Key Roles of Hyaluronan and Its CD44 Receptor in the Stemness and Survival of Cancer Stem Cells

Cancer stem cells (CSCs) represent a unique subpopulation of self-renewing oncogenic cells that drive cancer initiation and progression. CSCs often acquire multidrug and oxidative stress resistance and are thereby thought to be responsible for tumor recurrence following treatment and remission. Although the mechanisms responsible for CSC generation, maintenance, and expansion have become a major focus in cancer research, the molecular characteristics of CSCs remain poorly understood. The stemness and subsequent expansion of CSCs are believed to be highly influenced by changes in microenvironmental signals as well as genetic and epigenetic alterations. Hyaluronan (HA), a major component of the extracellular matrix, has recently been demonstrated to provide a favorable microenvironment for the self-renewal and maintenance of stem cells. HA directly and indirectly affects CSC self-renewal by influencing the behavior of both cancer and stromal cells. For instance, HA in the tumor microenvironment modulates the function of tumor-associated macrophages to support CSC self-renewal, and excessive HA production promotes the acquisition of CSC signatures through epithelial-to-mesenchymal transition. The importance of HA in mediating CSC self-renewal has been strengthened by the finding that interactions between HA and its receptor, CD44, propagate the stemness of CSCs. HA–CD44 interactions evoke a wide range of signals required for CSC self-renewal and maintenance. CD44 also plays a critical role in the preservation and multidrug resistance (MDR) of CSCs by transmitting survival and anti-apoptotic signals. Thus, a better understanding of the molecular mechanisms involved in HA and CD44 control of CSC stemness may help in the design of more effective therapies for cancer patients. In this review, we address the key roles of HA and CD44 in CSC self-renewal and maintenance. We also discuss the involvement of CD44 in the oxidative stress and MDR of CSCs.

Hyaluronan - a functional and structural sweet spot in the tissue microenvironment

Transition from homeostatic to reactive matrix remodeling is a fundamental adaptive tissue response to injury, inflammatory disease, fibrosis, and cancer. Alterations in architecture, physical properties, and matrix composition result in changes in biomechanical and biochemical cellular signaling. The dynamics of pericellular and extracellular matrices, including matrix protein, proteoglycan, and glycosaminoglycan modification are continually emerging as essential regulatory mechanisms underlying cellular and tissue function. Nevertheless, the impact of matrix organization on inflammation and immunity in particular and the consequent effects on tissue healing and disease outcome are arguably under-studied aspects of adaptive stress responses. Herein, we review how the predominant glycosaminoglycan hyaluronan (HA) contributes to the structure and function of the tissue microenvironment. Specifically, we examine the evidence of HA degradation and the generation of biologically active smaller HA fragments in pathological settings in vivo. We discuss how HA fragments versus nascent HA via alternate receptor-mediated signaling influence inflammatory cell recruitment and differentiation, resident cell activation, as well as tumor growth, survival, and metastasis. Finally, we discuss how HA fragmentation impacts restoration of normal tissue function and pathological outcomes in disease.