Exosome-delivered CD44v6/C1QBP complex drives pancreatic cancer liver metastasis by promoting fibrotic liver microenvironment.

OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) shows a remarkable predilection for liver metastasis. Pro-oncogenic secretome delivery and trafficking via exosomes are crucial for pre-metastatic microenvironment formation and metastasis. This study aimed to explore the underlying mechanisms of how PDAC-derived exosomes (Pex) modulate the liver microenvironment and promote metastasis. DESIGN: C57BL/6 mice were 'educated' by tail vein Pex injection. The intrasplenic injection liver metastasis and PDAC orthotopic transplantation models were used to evaluate liver metastasis. Stable cell lines CD44v6 (CD44 variant isoform 6) or C1QBP (complement C1q binding protein) knockdown or overexpression was established using lentivirus transfection or gateway systems. A total of 142 patients with PDAC in Huashan Hospital were retrospectively enrolled. Prognosis and liver metastasis were predicted using Kaplan-Meier survival curves and logistic regression models. RESULTS: Pex tail vein injection induced the deposition of liver fibrotic extracellular matrix, which promoted PDAC liver metastasis. Specifically, the exosomal CD44v6/C1QBP complex was delivered to the plasma membrane of hepatic satellite cells (HSCs), leading to phosphorylation of insulin-like growth factor 1 signalling molecules, which resulted in HSC activation and liver fibrosis. Expression of Pex CD44v6 and C1QBP in PDAC patients with liver metastasis was significantly higher than in PDAC patients without liver metastasis, and simultaneous high expression of exosomal CD44v6 and C1QBP correlated with a worse prognosis and a higher risk of postoperative PDAC liver metastasis. CONCLUSION: The Pex-derived CD44v6/C1QBP complex is essential for the formation of a fibrotic liver microenvironment and PDAC liver metastasis. Highly expressed exosomal CD44v6 and C1QBP are promising biomarkers for predicting prognosis and liver metastasis in patients with PDAC.

CD147 mediates the CD44s-dependent differentiation of myofibroblasts driven by transforming growth factor-ß1.

Progressive fibrosis leads to loss of organ function and affects many organs as a result of excessive extracellular matrix production. The ubiquitous matrix polysaccharide hyaluronan (HA) is central to this through association with its primary receptor, CD44, which exists as standard CD44 (CD44s) or multiple splice variants. Mediators such as profibrotic transforming growth factor (TGF)-ß1 and proinflammatory interleukin (IL)-1ß are widely associated with fibrotic progression. TGF-ß1 induces myofibroblast differentiation, while IL-1ß induces a proinflammatory fibroblast phenotype that promotes fibroblast binding to monocyte/macrophages. CD44 expression is essential for both responses. Potential CD44 splice variants involved, however, are unidentified. The TGF-ß1-activated CD44/epidermal growth factor receptor complex induces differentiation of metastatic cells through interactions with the matrix metalloproteinase inducer, CD147. This study aimed to determine the CD44 variants involved in TGF-ß1- and IL-1ß-mediated responses and to investigate the potential profibrotic role of CD147. Using immunocytochemistry and quantitative PCR, standard CD44s were shown to be essential for both TGF-ß1-induced fibroblast/myofibroblast differentiation and IL-1ß-induced monocyte binding. Co-immunoprecipitation identified that CD147 associated with CD44s. Using CD147-siRNA and confocal microscopy, we also determined that incorporation of the myofibroblast marker, αSMA, into F-actin stress fibers was prevented in the absence of CD147 and myofibroblast-dependent collagen gel contraction was inhibited. CD147 did not associate with HA, but removal of HA prevented the association of CD44s with CD147 at points of cell-cell contact. Taken together, our data suggest that CD44s/CD147 colocalization is essential in regulating the mechanical tension required for the αSMA incorporation into F-actin stress fibers that regulates myofibroblast phenotype.

EGFR inhibition blocks cancer stem cell clustering and lung metastasis of triple negative breast cancer.

Triple-negative breast cancer (TNBC) is one of the most aggressive and metastatic breast cancer subtypes lacking targeted therapy. Our recent work demonstrated that circulating tumor cell (CTC) clusters and polyclonal metastasis of TNBC are driven by aggregation of CD44+ cancer stem cells (CSC) and associated with an unfavorable prognosis, such as low overall survival. However, there is no existing therapeutic that can specifically block CTC or CSC cluster formation. Methods: Using patient-derived xenograft (PDX) models, we established an ex vivo tumor cell clustering assay for a pilot screening of blockade antibodies. After identifying EGFR as a target candidate, we modulated the gene expression and inhibited its kinase activity to determine its functional importance in tumor cell clustering and therapeutic inhibition of lung metastasis. We also examined the molecular regulation network of EGFR and a potential connection to CSC marker CD44 and microRNAs, which regulate CTC clustering. Results: We report here that EGFR inhibition successfully blocks circulating CSC (cCSC) clustering and lung metastasis of TNBC. EGFR enhances CD44-mediated tumor cell aggregation and CD44 stabilizes EGFR. Importantly, blocking EGFR by a novel anti-EGFR monoclonal antibody (clone LA1) effectively blocked cell aggregation in vitro and reduced lung metastasis in vivo. Furthermore, our data demonstrated that the tumor suppressor microRNA-30c serves as another negative regulator of cCSC clustering and lung metastasis by targeting CD44 as well as its downstream effector EGFR. Conclusion: Our studies identify a novel anti-EGFR therapeutic strategy to inhibit cCSC aggregation and therefore abolish cCSC cluster-mediated metastasis of TNBC.

Association of beta-catenin and CD44 in the development of renal cell carcinoma.

INTRODUCTION AND OBJECTIVE: Renal cell carcinoma (RCC) accounts for approximately 3% of all cancers. Approximately 25%-30% of patients present with metastatic disease at the time of diagnosis, and metastatic RCC is a treatment-resistant malignancy. Altered expression of cell adhesion molecules such as CD44 on tumor cells suggests a pathogenetic mechanism for tumor metastasis and may provide prognostic information for particular tumors. These cell matrix interactions of CD44 play a role in tumor cell invasion and metastasis. The Wnt/beta-catenin pathway turned out to be a promising target as it is involved in the regulation of cell proliferation, differentiation and apoptosis induction. METHOD: In this study, the expression of beta-catenin and CD44 was analyzed in primary renal cell carcinoma (RCC) samples to understand their association with development of the disease. For this purpose, immunohistochemical expression analysis of beta-catenin and CD44 was performed in 30 primary RCC histological samples and normal kidney tissues in different subtypes at different clinical stages of Indian patients (year: 2017-2019). RESULT: Most of the patients who presented were diagnosed as clear cell carcinoma and it was observed that expression of CD44 was high in patients with high stage tumors. Also beta-catenin was increased in advanced grade tumors, but there was insignificant correlation between high expression of molecules and survival or recurrence of disease. CONCLUSION: Both cd44 and beta-catenin activation was noted in patients with clear cell carcinoma, more in advanced tumors. Both can be promising targets for treatment in clear cell RCCs.

Role of A Novel Angiogenesis FKBPL-CD44 Pathway in Preeclampsia Risk Stratification and Mesenchymal Stem Cell Treatment.

CONTEXT: Preeclampsia is a leading cardiovascular complication in pregnancy lacking effective diagnostic and treatment strategies. OBJECTIVE: To investigate the diagnostic and therapeutic target potential of the angiogenesis proteins, FK506-binding protein like (FKBPL) and CD44. DESIGN AND INTERVENTION: FKBPL and CD44 plasma concentration or placental expression were determined in women pre- or postdiagnosis of preeclampsia. Trophoblast and endothelial cell function was assessed following mesenchymal stem cell (MSC) treatment and in the context of FKBPL signaling. SETTINGS AND PARTICIPANTS: Human samples prediagnosis (15 and 20 weeks of gestation; n ≥ 57), or postdiagnosis (n = 18 for plasma; n = 4 for placenta) of preeclampsia were used to determine FKBPL and CD44 levels, compared to healthy controls. Trophoblast or endothelial cells were exposed to low/high oxygen, and treated with MSC-conditioned media (MSC-CM) or a FKBPL overexpression plasmid. MAIN OUTCOME MEASURES: Preeclampsia risk stratification and diagnostic potential of FKBPL and CD44 were investigated. MSC treatment effects and FKBPL-CD44 signaling in trophoblast and endothelial cells were assessed. RESULTS: The CD44/FKBPL ratio was reduced in placenta and plasma following clinical diagnosis of preeclampsia. At 20 weeks of gestation, a high plasma CD44/FKBPL ratio was independently associated with the 2.3-fold increased risk of preeclampsia (odds ratio = 2.3, 95% confidence interval [CI] 1.03-5.23, P = 0.04). In combination with high mean arterial blood pressure (>82.5 mmHg), the risk further increased to 3.9-fold (95% CI 1.30-11.84, P = 0.016). Both hypoxia and MSC-based therapy inhibited FKBPL-CD44 signaling, enhancing cell angiogenesis. CONCLUSIONS: The FKBPL-CD44 pathway appears to have a central role in the pathogenesis of preeclampsia, showing promising utilities for early diagnostic and therapeutic purposes.

New function of the CD44 gene: Lipid metabolism regulation in bovine mammary epithelial cells.

The CD44 gene encodes a cell-surface glycoprotein that participates in a variety of biological processes such as cell interactions, adhesion, hematopoiesis, and tumor metastasis. We compared the transcriptome in bovine mammary epithelial cells (bMEC) of Chinese Holstein dairy cows producing milk of high and low fat contents. Our results suggest that CD44 might be a candidate gene affecting milk fat synthesis. In the present study, the overexpression of the CD44 gene increased the contents of intracellular triglycerides (TG) and cholesterol (CHOL), whereas knockdown of the CD44 gene decreased bMEC CHOL and TG contents. Gas chromatography analysis of fatty acid composition showed that the contents of α-linolenic acid, palmitic acid, and cis-8,11,14-eicosatrienoic acid were altered due to changes in the level of expression of the CD44 gene. Additionally, elaidic acid, palmitoleic acid, tridecanoic acid, and oleic acid were markedly reduced in the CD44 gene overexpression group compared with the control group. On the contrary, cis-5,8,11,14-eicosatetraenoic acid and stearic acid were markedly increased in the CD44 knockdown group compared with the control group. And RT2 Profiler PCR array (Qiagen, CLAB24070A Frankfurt, Germany) further suggested that overexpression or knockdown of the CD44 gene altered expression levels of functional genes associated with lipid metabolism. The present data indicate that CD44 plays a key regulatory role in lipid metabolism in bMEC.

Regulation of Macrophage and Dendritic Cell Function by Chondroitin Sulfate in Innate to Antigen-Specific Adaptive Immunity.

Chondroitin sulfate (CS), a type of glycosaminoglycan (GAG), is a linear acidic polysaccharide comprised of repeating disaccharides, modified with sulfate groups at various positions. Except for hyaluronan (HA), GAGs are covalently bound to core proteins, forming proteoglycans (PGs). With highly negative charges, GAGs interact with a variety of physiologically active molecules, including cytokines, chemokines, and growth factors, and control cell behavior during development and in the progression of diseases, including cancer, infections, and inflammation. Heparan sulfate (HS), another type of GAG, and HA are well reported as regulators for leukocyte migration at sites of inflammation. There have been many reports on the regulation of immune cell function by HS and HA; however, regulation of immune cells by CS has not yet been fully understood. This article focuses on the regulatory function of CS in antigen-presenting cells, including macrophages and dendritic cells, and refers to CSPGs, such as versican and biglycan, and the cell surface proteoglycan, syndecan.

Increased Regeneration Following Stress-Induced Lung Injury in Bleomycin-Treated Chimeric Mice with CD44 Knockout Mesenchymal Cells.

CD44, an adhesion-molecule promoting cell-migration, is shown here to increase in stress conditions following bleomycin-induced apoptosis in alveolar epithelial cells (AECs), a main target of lung injury. In vivo, it inhibits tissue regeneration and leads to fibrosis. We show that some AECs survive by the ataxia-telangiectasia mutated kinase/ATM pathway, and undergo a CD44-mediated epithelial-mesenchymal transdifferentiation (EMT) with migratory capacities in vitro, and in vivo. We assessed apoptosis vs. proliferation of AECs following bleomycin, ATM/P53 signaling pathway in AECs, and CD44 involvement in EMT, cell motility and tissue regeneration in vitro and in vivo. Expression of survival genes, CD44, and ATM/p53 pathway was elevated in AECs surviving bleomycin injury, as were the markers of EMT (downregulation of E-cadherin, upregulation of N-cadherin and vimentin, nuclear translocation of ß-catenin). Inhibition of CD44 decreased AECs transdifferentiation. Bleomycin-treated chimeric CD44KO-mice had decreased EMT markers, ATM, and mesenchymal cells (α-SMA+) accumulation in lung, increased surfactant-b, diminished lung mesenchymal cell motility, and increased lung tissue regenerative capacity following bleomycin injury, as indicated by lung collagen content and semiquantitave morphological index scoring. Thus, AECs surviving lung injury are plastic and undergo ATM-mediated, CD44-dependent transdifferentiation, preventing tissue regeneration and promoting fibrosis. Synthetic or natural compounds that downregulate CD44 may improve tissue regeneration following injury.

Hyaluronan-CD44 axis orchestrates cancer stem cell functions.

The prominent role of CD44 in tumor cell signaling together with its establishment as a cancer stem cell (CSC) marker for various tumor entities imply a key role for CD44 in CSC functional properties. Hyaluronan, the main ligand of CD44, is a major constituent of CSC niche and, therefore, the hyaluronan-CD44 signaling axis is of functional importance in this special microenvironment. This review aims to provide recent advances in the importance of hyaluronan-CD44 interactions in the acquisition and maintenance of a CSC phenotype. Hyaluronan-CD44 axis has a substantial impact on stemness properties of CSCs and drug resistance through induction of EMT program, oxidative stress resistance, secretion of extracellular vesicles/exosomes and epigenetic control. Potential therapeutic approaches targeting CSCs based on the hyaluronan-CD44 axis are also presented.

Osteopontin in Vascular Disease.

Inflammatory cytokines are necessary for an acute response to injury and the progressive healing process. However, when this acute response does not resolve and becomes chronic, the same proteins that once promoted healing then contribute to chronic inflammatory pathologies, such as atherosclerosis. OPN (Osteopontin) is a secreted matricellular cytokine that signals through integrin and CD44 receptors, is highly upregulated in acute and chronic inflammatory settings, and has been implicated in physiological and pathophysiologic processes. Evidence from the literature suggests that OPN may fit within the Goldilocks paradigm with respect to cardiovascular disease, where acute increases are protective, attenuate vascular calcification, and promote postischemic neovascularization. In contrast, chronic increases in OPN are clinically associated with an increased risk for a major adverse cardiovascular event, and OPN expression is a strong predictor of cardiovascular disease independent of traditional risk factors. With the recent finding that humans express multiple OPN isoforms as the result of alternative splicing and that these isoforms have distinct biologic functions, future studies are required to determine what OPN isoform(s) are expressed in the setting of vascular disease and what role each of these isoforms plays in vascular disease progression. This review aims to discuss our current understanding of the role(s) of OPN in vascular disease pathologies using evidence from in vitro, animal, and clinical studies. Where possible, we discuss what is known about OPN isoform expression and our understanding of OPN isoform contributions to cardiovascular disease pathologies.

Homophilic CD44 Interactions Mediate Tumor Cell Aggregation and Polyclonal Metastasis in Patient-Derived Breast Cancer Models.

Circulating tumor cells (CTC) seed cancer metastases; however, the underlying cellular and molecular mechanisms remain unclear. CTC clusters were less frequently detected but more metastatic than single CTCs of patients with triple-negative breast cancer and representative patient-derived xenograft models. Using intravital multiphoton microscopic imaging, we found that clustered tumor cells in migration and circulation resulted from aggregation of individual tumor cells rather than collective migration and cohesive shedding. Aggregated tumor cells exhibited enriched expression of the breast cancer stem cell marker CD44 and promoted tumorigenesis and polyclonal metastasis. Depletion of CD44 effectively prevented tumor cell aggregation and decreased PAK2 levels. The intercellular CD44-CD44 homophilic interactions directed multicellular aggregation, requiring its N-terminal domain, and initiated CD44-PAK2 interactions for further activation of FAK signaling. Our studies highlight that CD44+ CTC clusters, whose presence is correlated with a poor prognosis of patients with breast cancer, can serve as novel therapeutic targets of polyclonal metastasis. SIGNIFICANCE: CTCs not only serve as important biomarkers for liquid biopsies, but also mediate devastating metastases. CD44 homophilic interactions and subsequent CD44-PAK2 interactions mediate tumor cluster aggregation. This will lead to innovative biomarker applications to predict prognosis, facilitate development of new targeting strategies to block polyclonal metastasis, and improve clinical outcomes.See related commentary by Rodrigues and Vanharanta, p. 22.This article is highlighted in the In This Issue feature, p. 1.

cd44 deletion suppresses atypia in the precancerous mouse testis.

Loss-of-function of RHAMM causes hypofertility and testicular atrophy in young mice, followed by germ cell neoplasia in situ (GCNIS) of the testis, cellular atypia, and development of the testicular germ cell tumor (TGCT) seminoma. These pathologies reflect the risk factors and phenotypes that precede seminoma development in humans and-given the high prevalence of RHAMM downregulation in human seminoma-link RHAMM dysfunction with the aetiology of male hypofertility and GCNIS-related TGCTs. The initiating event underlying these pathologies, in RHAMM mutant testis, is premature displacement of undifferentiated progenitors from the basal compartment. We hypothesized that cd44 (both cancer initiating cell- and oncogenic progression marker) will drive GCNIS development, induced by RHAMM-loss-of-function in the mouse. We report that cd44 is expressed in a specific subset of GCNIS testes. Its genetic deletion has no effect on GCNIS onset, but it ameliorates oncogenic progression. We conclude that cd44 expression, combined with RHAMM dysfunction, promotes oncogenic progression in the testis.

RHAMM induces progression of rheumatoid arthritis by enhancing the functions of fibroblast-like synoviocytes.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic and refractory autoimmune joint disease. Fibroblast-like synoviocytes (FLS) produce inflammatory cytokines and are involved in the migration and invasion of panuus tissue, which leads to the destruction of joints in RA. Receptor for hyaluronan mediated motility (RHAMM), is known to be one of the important receptors for hyaluronic acid. It has the ability to regulate migration of fibrocytes and infiltration of inflammatory cells. Here,we explored the mechanisms of RHAMM in RAFs. METHODS: Quantitative PCR and western blot were performed to test the expression of RHAMM in synoviocytes of RA patients and osteoarthritis (OA) controls. Collagen antibody-induced arthritis (CAIA) was used to investigate the RHAMM expression in mouse synovial issues. RHAMM siRNA was used to detect the function of RHAMM in FLS. RESULTS: RA-FLS has a significantly higher expression of RHAMM than OA-FLS. Expression of RHAMM in joint synovial tissue was markedly increased in the CAIA mice compared with the controls. RHAMM silencing using SiRNA was not only decreased the production of IL-6 and IL-8, but also inhibited the migration and invasion of RA-FLS. CONCLUSIONS: RHAMM has an important role in the FLS induced modulation of inflammation and destruction of joints in RA.

High molecular weight hyaluronan protects cartilage from degradation by inhibiting aggrecanase expression.

Hyaluronan (HA) is an extracellular matrix (ECM) component of articular cartilage and has been used to treat patients with osteoarthritis (OA). A disintegrin and metalloproteinases with thrombospondin motifs (ADAMTSs) play an important role in cartilage degradation in OA. We have previously reported that ADAMTS4 and ADAMTS9 were induced by cytokine stimulation. However, the effect of HA on the cytokine-inducible ADAMTS9 has never been investigated. Moreover, it is unclear whether HA protects cartilage by suppressing aggrecan degradation. Here, we examined the effects of HA on ADAMTS expression in vitro and on cartilage degradation in vivo. ADAMTS9 expression was higher than that of the other aggrecanases (ADAMTS4 and 5) in human chondrocytes, chondrocytic cells, and rat cartilage. ADAMTS4 and 9 mRNA levels were upregulated in cytokine-stimulated chondrocytes and chondrocytic cells. Pre-incubation with HA significantly inhibited ADAMTS9 mRNA expression in cytokine-stimulated cells. In a rat OA model, Adamts5 and 9 mRNA levels were transiently increased after surgery; intra-articular HA injections attenuated the induction of Adamts5 and 9 mRNA. HA also blocked aggrecan cleavage by aggrecanase in OA rats in a molecular size-dependent manner. These results demonstrate that HA attenuates induced aggrecanases expression in OA and thereby protects articular cartilage degradation by this enzyme. Our findings provide insight into the molecular basis for the beneficial effects of HA in OA. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:3247-3255, 2018.

High expression of CD44v9 and xCT in chemoresistant hepatocellular carcinoma: Potential targets by sulfasalazine.

CD44v9 is expressed in cancer stem cells (CSC) and stabilizes the glutamate-cystine transporter xCT on the cytoplasmic membrane, thereby decreasing intracellular levels of reactive oxygen species (ROS). This mechanism confers ROS resistance to CSC and CD44v9-expressing cancer cells. The aims of the present study were to assess: (i) expression status of CD44v9 and xCT in hepatocellular carcinoma (HCC) tissues, including those derived from patients treated with hepatic arterial infusion chemoembolization (HAIC) therapy with cisplatin (CDDP); and (ii) whether combination of CDDP with sulfasalazine (SASP), an inhibitor of xCT, was more effective on tumor cells than CDDP alone by inducing ROS-mediated apoptosis. Twenty non-pretreated HCC tissues and 7 HCC tissues administered HAIC therapy with CDDP before surgical resection were subjected to immunohistochemistry analysis of CD44v9 and xCT expression. Human HCC cell lines HAK-1A and HAK-1B were used in this study; the latter was also used for xenograft experiments in nude mice to assess in vivo efficacy of combination treatment. CD44v9 positivity was significantly higher in HAIC-treated tissues (5/7) than in non-pretreated tissues (2/30), suggesting the involvement of CD44v9 in the resistance to HAIC. xCT was significantly expressed in poorly differentiated HCC tissues. Combination treatment effectively killed the CD44v9-harboring HAK-1B cells through ROS-mediated apoptosis and significantly decreased xenografted tumor growth. In conclusion, the xCT inhibitor SASP augmented ROS-mediated apoptosis in CDDP-treated HCC cells, in which the CD44v9-xCT system functioned. As CD44v9 is typically expressed in HAIC-resistant HCC cells, combination treatment with SASP with CDDP may overcome such drug resistance.

CD44 targeted PLGA nanomedicines for cancer chemotherapy.

In recent years scientific community has drawn a great deal of attention towards understanding the enigma of cluster of differentiation-44 (CD44) in order to deliver therapeutic agents more selectively towards tumor tissues. Moreover, its over-expression in variety of solid tumors has attracted drug delivery researchers to target this receptor with nanomedicines. Conventional nanomedicines based on biodegradable polymers such as poly(lactide-co-glycolide) (PLGA) are often associated with insufficient cellular uptake by cancer cells, due to lack of active targeting moiety on their surface. Therefore, to address this limitation, CD44 targeted PLGA nanomedicines has gained considerable interest for enhancing the efficacy of chemotherapeutic agents. In this review, we have elaborately discussed the recent progress in the design and synthesis of CD44 targeted PLGA nanomedicines used to improve tumor-targeted drug delivery. We have also discussed strategies based on co-targeting of CD44 with other targeting moieties such as folic acid, human epidermal growth factor 2 (HER2), monoclonal antibodies using PLGA based nanomedicines.

Clinicopathological significance of cancer stem cell markers CD44 and ALDH1 expression in breast cancer.

BACKGROUND: CD44 and aldehyde dehydrogenase 1 (ALDH1) has been reputed to be cancer stem cell (CSC) markers in breast cancer. Yet, the clinicopathologic and prognostic significance of these markers remain unclear. In this study, we have investigated the expression of these markers and their relation with conventional clinicopathologic tumor characteristic including molecular subtype. METHODS: CD44 and ALDH1 expression were investigated by immunohistochemistry in a series of 157 formalin-fixed paraffin-embedded breast cancer tissues. RESULTS: Overall, CD44 and ALDH1 are, respectively, detected in 33% (52 of 157) and 7% (10 of 157) of breast cancer cases. We also observed that CD44 expression was associated with histological grade (p = 0.005). For ALDH1, we found that its expression is more frequent with elderly women (> 50 years, p = 0.03). The investigation of relationship between the stem cell phenotype and breast cancer molecular subtype, revealed that CD44 and ALDH1 expression was more frequent in basal-like tumors (p = 0.005). Among the two cancer stem cell markers tested, ALDH1 showed a strong association with the basal marker EGFR (p = 0.05). CONCLUSIONS: These findings suggest that CD44 and ALDH1 play a role in the clinical behavior in breast cancer and might be interesting biomarkers and therapeutic targets.

Metabolism and mechanisms of action of hyaluronan in human biology.

Hyaluronan is a ubiquitous high-molecular weight polymer of repeated disaccharides of glucuronic acid and N-acetylglucosamine. It is a membrane-bound, viscous material extruded into the extracellular matrix after being synthesized in the cytoplasm by hyaluronan synthases complex and a regulated degradation by a group of enzymes called hyaluronidases. Hyaluronan has varied biological roles on many vital organismal functions, such as cellular and tissue development, migration and repair after injury or inflammation and cancer genesis. Hyaluronan in the tissue microenvironment is regulated by its concentration as well as the chain length of the polysaccharide. Many functions of hyaluronan are mediated by specific receptors at the cellular level, though its general physiochemical properties facilitate and coordinate many organ functions as well as in development. These fundamental characteristics of hyaluronan are reviewed, focusing on human biological context.

Sphingosine-1-phosphate mediates the therapeutic effects of bone marrow mesenchymal stem cell-derived microvesicles on articular cartilage defect.

Microvesicles (MVs) are emerging as a new mechanism of intercellular communication by transferring cellular components to target cells, yet their function in disease is just being explored. However, the therapeutic effects of MVs in cartilage injury and degeneration remain unknown. We found MVs contained high levels of sphingosine-1-phosphate (S1P) compared with the original bone marrow mesenchymal stem cells (MSCs). The enrichment of S1P in MVs was mediated by sphingosine kinase 1 (SphK1), but not by sphingosine kinase 2 (SphK2). Co-culture of human chondrocytes with MVs resulted in increased proliferation of chondrocytes in vitro, which was mediated by activation of S1P receptor 1 (S1PR1) expressed on chondrocytes. Meanwhile, MVs inhibited interleukin 1 beta-induced human chondrocytes apoptosis in a dose dependent manner. Furthermore, uptake of MVs by primary cultures of human chondrocytes was mediated by CD44 expressed by MVs. Anti-CD44 antibody significantly reduced the uptake of fluorescent protein-labeled MVs by chondrocytes. Further, blocking S1P by its neutralizing antibody significantly inhibited the therapeutic effects of MVs in vivo. Taken together, MVs showed therapeutic potential for treatment of clinical cartilage injury. This therapeutic potential is due to CD44-mediated uptake of MVs by chondrocytes and the S1P/S1PR1 axis-mediated proliferative effects of MVs on chondrocytes.

Differential recruitment of CD44 isoforms by ErbB ligands reveals an involvement of CD44 in breast cancer.

Members of the CD44 family of transmembrane glycoproteins control cell signaling pathways from numerous cell surface receptors, including receptor tyrosine kinases (RTKs). The decisive factor (ligand, RTKs or both) that controls the recruitment of specific CD44 isoforms is still unknown. We investigated this question by using the EGFR signaling pathway, in which one receptor can be activated by a broad range of ligands. By means of siRNA-mediated downregulation of CD44 expression and blocking experiments, we identified CD44v6 as a co-receptor for EGF- and ER-induced ErbB1 activation and for NRG1-induced ErbB3 and ErbB4 activation. In contrast, TGFα is independent of all CD44 isoforms, even though it addresses the same receptor pairs as EGF. Moreover, the heparin-sulfated CD44v3 isoform is required for HB-EGF-induced EGFR signaling. These data suggest that specific CD44 isoforms are recruited in a ligand-dependent manner as co-receptors in the EGFR signaling pathways and that the specificity is determined by the ligand and not by the receptors themselves. The in vivo relevance of this interplay between CD44 isoforms and EGFR ligands is underlined by the decreased metastatic spreading of mammary carcinomas in mice treated with a CD44v6-specific peptide. Most importantly, we found a clear correlation between the presence of CD44v6/ErbB1 complexes in breast cancer patients and lymph node metastases.