Osteopontin Induction of Hyaluronan Synthase 2 Expression Promotes Breast Cancer Malignancy

The membrane receptor CD44: novel insights into metabolism

CD44, a cell-surface glycoprotein, has long been studied as a cancer molecule due to its essential role in physiological activities in normal cells and pathological activities in cancer cells, such as cell proliferation, adhesion, and migration; angiogenesis; inflammation; and cytoskeleton rearrangement. Yet, recent evidence suggests a role of CD44 in metabolism, especially insulin resistance in obesity and diabetes. In line with the current concept of fibroinflammation in obesity and insulin resistance, CD44 as the main receptor of the extracellular matrix component, hyaluronan (HA), has been shown to regulate diet-induced insulin resistance in muscle and other insulin-sensitive tissues. In this review, we integrate current evidence for a role of CD44 in regulating glucose and lipid homeostasis and speculate about its involvement in the pathogenesis of chronic metabolic diseases, including obesity and diabetes. We summarize the current development of CD44-targeted therapies and discuss its potential for the use in treating metabolic diseases.

Differential sensitivity of inbred mouse strains to ovarian damage in response to low-dose total body irradiation†

Radiation induces ovarian damage and accelerates reproductive aging. Inbred mouse strains exhibit differential sensitivity to lethality induced by total body irradiation (TBI), with the BALB/cAnNCrl (BALB/c) strain being more sensitive than the 129S2/SvPasCrl (129) strain. However, whether TBI-induced ovarian damage follows a similar pattern of strain sensitivity is unknown. To examine this possibility, female BALB/c and 129 mice were exposed to a single dose of 1 Gy (cesium-137 γ) TBI at 5 weeks of age, and ovarian tissue was harvested for histological and gene expression analyses 2 weeks post exposure. Sham-treated mice served as controls. 1 Gy radiation nearly eradicated the primordial follicles and dramatically decreased the primary follicles in both strains. In contrast, larger growing follicles were less affected in the 129 relative to BALB/c strain. Although this TBI paradigm did not induce detectable ovarian fibrosis in either of the strains, we did observe strain-dependent changes in osteopontin (Spp1) expression, a gene involved in wound healing, inflammation, and fibrosis. Ovaries from BALB/c mice exhibited higher baseline Spp1 expression that underwent a significant decrease in response to radiation relative to ovaries from the 129 strain. A correspondingly greater change in the ovarian matrix, as evidenced by reduced ovarian hyaluronan content, was also observed following TBI in BALB/c mice relative to 129 mice. These early changes in the ovary may predispose BALB/c mice to more pronounced late effects of TBI. Taken together, our results demonstrate that aspects of ovarian damage mirror other organ systems with respect to overall strain-dependent radiation sensitivity.

Isoform-specific promotion of breast cancer tumorigenicity by TBX3 involves induction of angiogenesis

TBX3 is a member of the highly conserved family of T-box transcription factors involved in embryogenesis, organogenesis and tumor progression. While the functional role of TBX3 in tumorigenesis has been widely studied, less is known about the specific functions of the different isoforms (TBX3iso1 and TBX3iso2) which differ in their DNA-binding domain. We therefore sought to investigate the functional consequence of this highly conserved splice event as it relates to TBX3-induced tumorigenesis. By utilizing a nude mouse xenograft model, we have identified differential tumorigenic potential between TBX3 isoforms, with TBX3iso1 overexpression more commonly associated with invasive carcinoma and high tumor vascularity. Transcriptional analysis of signaling pathways altered by TBX3iso1 and TBX3iso2 overexpression revealed significant differences in angiogenesis-related genes. Importantly, osteopontin (OPN), a cancer-associated secreted phosphoprotein, was significantly up-regulated with TBX3iso1 (but not TBX3iso2) overexpression. This pattern was observed across three non/weakly-tumorigenic breast cancer cell lines (21PT, 21NT, and MCF7). Up-regulation of OPN in TBX3iso1 overexpressing cells was associated with induction of hyaluronan synthase 2 (HAS2) expression and increased retention of hyaluronan in pericellular matrices. These transcriptional changes were accompanied by the ability to induce endothelial cell vascular channel formation by conditioned media in vitro, which could be inhibited through addition of an OPN neutralizing antibody. Within the TCGA breast cancer cohort, we identified an 8.1-fold higher TBX3iso1 to TBX3iso2 transcript ratio in tumors relative to control, and this ratio was positively associated with high-tumor grade and an aggressive molecular subtype. Collectively, the described changes involving TBX3iso1-dependent promotion of angiogenesis may thus serve as an adaptive mechanism within breast cancer cells, potentially explaining differences in tumor formation rates between TBX3 isoforms in vivo. This study is the first of its kind to report significant functional differences between the two TBX3 isoforms, both in vitro and in vivo.

Hyaluronan concentration and molecular mass in psoriatic arthritis: biomarkers of disease severity, resistance to treatment, and outcome

Objective: Low molecular mass hyaluronan causes inflammatory processes and can act as a pro-inflammatory cytokine in skin and other sites of activity in psoriatic arthritis (PsA). This study investigated whether the molecular mass distribution of hyaluronan (HA) in skin and the quantity of circulating HA are related to the clinical inflammatory picture in PsA with active disease and to the effect of treatment with anti-tumour necrosis factor-α (anti-TNF-α) adalimumab. Methods: Twenty patients with TNF-α-naïve active polyarticular PsA were included in this prospective clinical trial of treatment with 40 mg s.c. adalimumab according to standard procedure. Clinical activity, patients' assessments, and skin biopsies were captured at inclusion and at the 12 week follow-up. Ten healthy individuals were recruited for comparison of HA analyses. Histochemistry of skin inflammation, serum HA, and molecular mass of HA were determined. Results: Overall improvements in clinical parameters were observed. Eight of 18 patients reached minimum disease activity after 12 weeks and disease activity was significantly reduced (p < 0.0001). Patients with elevated serum HA values were significantly older, had later onset of arthritis and more deformed joints, still had swollen joints after treatment, and had more circulating inflammatory biomarkers. More severe disease pathology showed a wide spectrum of high-molecular-mass HA accompanied by low mass HA. The treatment appears partly to normalize the HA mass distribution. Conclusion: HA concentration and mass seem to be two possible factors in the inflammatory pathology of PsA acting as biomarkers for disease severity, resistance to treatment, and worse outcome.

The cancer-related transcription factor RUNX2 modulates expression and secretion of the matricellular protein osteopontin in osteosarcoma cells to promote adhesion to endothelial pulmonary cells and lung metastasis

Osteosarcomas are bone tumors that frequently metastasize to the lung. Aberrant expression of the transcription factor, runt-related transcription factor 2 (RUNX2), is a key pathological feature in osteosarcoma and associated with loss of p53 and miR-34 expression. Elevated RUNX2 may transcriptionally activate genes mediating tumor progression and metastasis, including the RUNX2 target gene osteopontin (OPN/SPP1). This gene encodes a secreted matricellular protein produced by osteoblasts to regulate bone matrix remodeling and tissue calcification. Here we investigated whether and how the RUNX2/OPN axis regulates lung metastasis of osteosarcoma. Importantly, RUNX2 depletion attenuates lung metastasis of osteosarcoma cells in vivo. Using next-generation RNA-sequencing, protein-based assays, as well as the loss- and gain-of-function approaches in selected osteosarcoma cell lines, we show that osteopontin messenger RNA levels closely correlate with RUNX2 expression and that RUNX2 controls the levels of secreted osteopontin. Elevated osteopontin levels promote heterotypic cell-cell adhesion of osteosarcoma cells to human pulmonary microvascular endothelial cells, but not in the presence of neutralizing antibodies. Collectively, these findings indicate that the RUNX2/OPN axis regulates the ability of osteosarcoma cells to attach to pulmonary endothelial cells as a key step in metastasis of osteosarcoma cells to the lung.

Elevated expression of hyaluronan synthase 2 associates with decreased survival in diffusely infiltrating astrocytomas

Background

Diffusely infiltrating astrocytomas originate from astrocytic glial cells or their precursor cells and are the most common type of brain tumors in adults. In this retrospective study, we investigated the content of hyaluronan, its cell surface receptor, CD44 and the expression of hyaluronan metabolizing enzymes, in these aggressive tumors. Hyaluronan is the main component of extracellular matrix in the brain. In many tumors, aberrant hyaluronan metabolism implicates aggressive disease progression and metastatic potential.

Methods

Our material consisted of 163 diffusely infiltrating astrocytomas (WHO grades II-IV). Tumor samples were processed into tissue microarray (TMA) blocks. The TMA sections were stained for hyaluronan, CD44, hyaluronan synthases 1–3 (HAS1–3) and hyaluronidase 2 (HYAL2). The immunostaining results were compared with χ2 –test or with Kruskal-Wallis test for correlation with clinicopathological parameters and survival analyses were done with Kaplan-Meier log rank test and Cox regression.

Results

Hyaluronan and CD44 were strongly expressed in astrocytic gliomas but their expression did not correlate with WHO grade or any other clinicopathological parameters whereas high HAS2 staining intensity was observed in IDH1 negative tumors (p = 0.003). In addition, in non-parametric tests increased HAS2 staining intensity correlated with increased cell proliferation (p = 0.013) and in log rank test with decreased overall survival of patients (p = 0.001). In the Cox regression analysis HAS2 expression turned out to be a significant independent prognostic factor (p = 0.008).

Conclusions

This study indicates that elevated expression of HAS2 is associated with glioma progression and suggests that HAS2 has a prognostic significance in diffusely infiltrating astrocytomas.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4569-1) contains supplementary material, which is available to authorized users.

Sorafenib controls the epithelial‑mesenchymal transition of ovarian cancer cells via EGF and the CD44‑HA signaling pathway in a cell type‑dependent manner

Cluster of differentiation (CD) 44 and epidermal growth factor (EGF) are closely involved in cellular migration and have been used as stem cell markers. Although the hyaluronan (HA)‑binding CD44 is responsible for enhanced cellular motility, the mechanism underlying its actions in various cell types and clinical conditions have yet to be elucidated. In the present study, the multikinase inhibitor sorafenib was used to investigate the diverse effects of EGF stimulation on epithelial‑mesenchymal transition (EMT) in ovarian cancer cells using immunoblotting and reverse transcription‑polymerase chain reaction. In addition, the association between EGF and CD44/HA signaling pathways in the control of mesenchymal phenotype was determined by gene silencing with small interfering RNA transfection. EGF stimulation of ovarian cancer cells increased cellular migration, mesenchymal transition, CD44 expression and the activation of matrix metalloproteinase (MMP)‑2 and MMP‑9. Sorafenib effectively suppressed the loss of epithelial characteristics in EGF‑treated SK‑OV‑3 ovarian cancer cells, via targeting the mitogen‑activated protein kinase (MAPK)/extracellular signal‑regulated kinase (ERK) pathway. Although treatment of Caov‑3 ovarian cancer cells with sorafenib blocked the expression of mesenchymal phenotypes following EGF stimulation, EGF‑activated Caov‑3 cells exhibited reduced MAPK/ERK signaling. Furthermore, EGF‑activated Caov‑3 cells increased the expression of hyaluronan synthase 2 and HA‑CD44 ligation in EGF‑exposed Caov‑3 cells, which resulted in the activation of the Ras/Raf/MEK signaling pathway, amplification of migratory activity and the expression of mesenchymal markers, including N‑cadherin and vimentin. Furthermore, silencing EGFR in SK‑OV‑3 cells and CD44 in Caov‑3 cells suppressed their migratory activity, through inhibition of the MAPK/ERK pathway. The present results suggested that EGF‑mediated signaling may regulate metastasis and invasion of ovarian cancer cells, in a cancer cell type‑dependent manner.

Inhibition of hyaluronic acid formation sensitizes chronic myelogenous leukemia to treatment with doxorubicin

In the current study we examined the ability of 4-methylumbelliferone (4-MU), which can inhibit hyaluronic acid synthesis, to sensitize K562 chronic myelogenous leukemia (CML) cells to doxorubicin therapy. Exposure of K562 cells to doxorubicin led to increased hyaluronic acid synthase (HAS) gene expression and increased levels of cell surface hyaluronic acid. Furthermore, exposure of K562 cells to exogenous HA caused resistance to doxorubicin-induced cell death. The combination of low dose 4-MU and doxorubicin led to increased apoptosis when compared to higher doses of any agent alone. Additionally, treatment with 4-MU led to a significant reduction in doxorubicin-induced increase in HA cell surface expression. Mechanistically, 4-MU treatment led to an increase in p38 activation and PARP cleavage. The role of p38 in 4-MU/doxorubicin-treated K562 cells was confirmed when p38 inhibitors led to protection from 4-MU/doxorubicin-induced apoptosis. Together, results from this study suggest that treatment with 4-MU increases the sensitivity of CML to chemotherapeutics by decreasing their HA-mediated resistance to apoptosis.

Hyaluronan synthesis is necessary for autoreactive T-cell trafficking, activation, and Th1 polarization

The extracellular matrix polysaccharide hyaluronan (HA) accumulates at sites of autoimmune inflammation, including white matter lesions in multiple sclerosis (MS), but its functional importance in pathogenesis is unclear. We have evaluated the impact of 4-methylumbelliferone (4-MU), an oral inhibitor of HA synthesis, on disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Treatment with 4-MU decreases the incidence of EAE, delays its onset, and reduces the severity of established disease. 4-MU inhibits the activation of autoreactive T cells and prevents their polarization toward a Th1 phenotype. Instead, 4-MU promotes polarization toward a Th2 phenotpye and induction of Foxp3(+) regulatory T cells. Further, 4-MU hastens trafficking of T cells through secondary lymphoid organs, impairs the infiltration of T cells into the CNS parenchyma, and limits astrogliosis. Together, these data suggest that HA synthesis is necessary for disease progression in EAE and that treatment with 4-MU may be a potential therapeutic strategy in CNS autoimmunity. Considering that 4-MU is already a therapeutic, called hymecromone, that is approved to treat biliary spasm in humans, we propose that it could be repurposed to treat MS.

Effect of osteopontin on the mRNA expression of ADAMTS4 and ADAMTS5 in chondrocytes from patients with knee osteoarthritis

Previous studies have demonstrated that osteopontin (OPN) levels are elevated in the synovial fluid and articular cartilage, and are associated with the severity of knee osteoarthritis (OA). However, the role of OPN in the pathogenesis of OA has yet to be elucidated. The present study aimed to investigate the effects of OPN on the expression of the aggrecanases, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4 and ADAMTS5, in human OA chondrocytes, as they serve a key function in aggrecan degradation. Human OA chondrocytes were obtained from the knees of 16 patients with OA, and subsequently cultured in a monolayer. The chondrocytes were divided into three groups, which included the control (no treatment), N-OPN (treated with 100 ng/ml OPN, the normal circulating OPN concentration) and the H-OPN groups (treated with 1 µg/ml OPN, a high OPN concentration). Reverse transcription-quantitative polymerase chain reaction was performed to quantify the relative mRNA expression levels of ADAMTS4, ADAMTS5 and aggrecan in the chondrocytes. The mRNA expression levels of ADAMTS4 were significantly reduced in the N-OPN and H-OPN groups when compared with the control group (P<0.0001). In addition, the mRNA expression levels of ADAMTS4 were lower in the H-OPN group when compared with the N-OPN group (P<0.001). However, no statistically significant difference was observed in the relative mRNA expression levels of ADAMTS5 among the three groups (P>0.05). Furthermore, the mRNA expression levels of aggrecan were higher in the N-OPN and H-OPN groups when compared with the control group (P<0.0001), and a statistically significant difference was observed between the N-OPN and H-OPN groups with regard to the mRNA expression of aggrecan (P<0.0001). These results demonstrated that OPN may exert a protective effect in human OA chondrocytes against aggrecan degradation by suppressing the expression of ADAMTS4.

Role of osteopontin in the pathophysiology of cancer

Osteopontin (OPN) is a multifunctional cytokine that impacts cell proliferation, survival, drug resistance, invasion, and stem like behavior. Due to its critical involvement in regulating cellular functions, its aberrant expression and/or splicing is functionally responsible for undesirable alterations in disease pathologies, specifically cancer. It is implicated in promoting invasive and metastatic progression of many carcinomas. Due to its autocrine and paracrine activities OPN has been shown to be a crucial mediator of cellular cross talk and an influential factor in the tumor microenvironment. OPN has been implicated as a prognostic and diagnostic marker for several cancer types. It has also been explored as a possible target for treatment. In this article we hope to provide a broad perspective on the importance of OPN in the pathophysiology of cancer.

Effect of a 12-month exercise intervention on serum biomarkers of angiogenesis in postmenopausal women: a randomized controlled trial

BACKGROUND

Increased physical activity is associated with decreased risk of several types of cancer, but underlying mechanisms are poorly understood. Angiogenesis, in which new blood vessels are formed, is common to adipose tissue formation/remodeling and tumor vascularization.

METHODS

We examined effects of a 12-month 45 minutes/day, 5 days/week moderate-intensity aerobic exercise intervention on four serum markers of angiogenesis in 173 sedentary, overweight, postmenopausal women, 50 to 75 years, randomized to intervention versus stretching control. Circulating levels of positive regulators of angiogenesis [VEGF, osteopontin (OPN), plasminogen activator inhibitor-1 (PAI-1)], and the negative regulator pigment epithelium-derived factor (PEDF), were measured by immunoassay at baseline and 12 months. Changes were compared using generalized estimating equations, adjusting for baseline levels of analytes and body mass index (BMI).

RESULTS

VEGF, OPN, or PAI-1 levels did not differ by intervention arm. Participants randomized to exercise significantly reduced PEDF (-3.7%) versus controls (+3.0%; P = 0.009). Reductions in fat mass were significantly associated with reductions in PAI-1 (Ptrend = 0.03; Ptrend = 0.02) and PEDF (Ptrend = 0.002; Ptrend = 0.01) compared with controls, or to those who gained any fat mass respectively. There was a significant association between decreases in VO2max, and increased reductions in PEDF (Ptrend = 0.03), compared with participants who increased their level of fitness.

CONCLUSIONS

Fat loss reduces circulating PAI-1 and PEDF. Changes in VO2max are associated with alterations in PEDF, but these associations are complex.

IMPACT

Unexpected reductions in PEDF with decreasing fat mass, and with decreasing VO2max, warrant further study, including examining the effects of different types and intensities of exercise; and role of dietary weight-loss with and without exercise.

Inhibition of HAS2 induction enhances the radiosensitivity of cancer cells via persistent DNA damage

Hyaluronan synthase 2 (HAS2), a synthetic enzyme for hyaluronan, regulates various aspects of cancer progression, including migration, invasion and angiogenesis. However, the possible association of HAS2 with the response of cancer cells to anticancer radiotherapy, has not yet been elucidated. Here, we show that HAS2 knockdown potentiates irradiation-induced DNA damage and apoptosis in cancer cells. Upon exposure to radiation, all of the tested human cancer cell lines exhibited marked (up to 10-fold) up-regulation of HAS2 within 24h. Inhibition of HAS2 induction significantly reduced the survival of irradiated radioresistant and -sensitive cells. Interestingly, HAS2 depletion rendered the cells to sustain irradiation-induced DNA damage, thereby leading to an increase of apoptotic death. These findings indicate that HAS2 knockdown sensitizes cancer cells to radiation via persistent DNA damage, further suggesting that the irradiation-induced up-regulation of HAS2 contributes to the radioresistance of cancer cells. Thus, HAS2 could potentially be targeted for therapeutic interventions aimed at radiosensitizing cancer cells.

Hepatocellualar carcinoma serum markers

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in some areas of the world. In most cases, HCC is diagnosed at a late stage. Therefore, the prognosis of patients with HCC is generally poor. The recommended screening strategy for patients with cirrhosis includes the determination of serum α-fetoprotein (AFP) levels and an abdominal ultrasound every 6 months to detect HCC at an earlier stage. AFP, however, is a marker characterized by poor sensitivity and specificity, and abdominal ultrasound is highly dependent on the operator's experience. In addition to AFP, Lens culinaris agglutinin-reactive AFP (AFP-L3), des-γ-carboxy prothrombin (DCP), glypican-3 (GPC-3), osteopontin (OPN), and several other biomarkers (such as squamous cell carcinoma antigen-immunoglobulin M complexes [SCCA-IgM], alpha-1-fucosidase [AFU], chromogranin A [CgA], human hepatocyte growth factor, insulin-like growth factor) have been proposed as markers for the early detection of HCC. For these markers, we describe the mechanisms of production, and their diagnostic and prognosis roles. None of them is optimal; however, when used together, their sensitivity in detecting HCC is increased. Recent research has shown that some biomarkers have mitogenic and migratory activities in the angiogenesis of HCC and are a factor of tumor growth.

The effect of hyaluronic acid on osteopontin and CD44 mRNA of fibroblast-like synoviocytes in patients with osteoarthritis of the knee

The aim of this study was to investigate the effect of hyaluronic acid (HA) on the expression of osteopontin (OPN) and CD44 mRNA of fibroblast-like synoviocytes (FLS) in the patients with osteoarthritis (OA) of the knee. FLS were obtained from the knees of 10 patients with OA. Real-time quantitative polymerase chain reaction (Q-PCR) was used to assess the expression of the OPN mRNA and CD44 mRNA. The relative OPN mRNA expression in HA group (6.47 ± 2.30-fold) was significantly higher than in the control group (P = 0.045, P < 0.05), while in HYL group (0.65 ± 0.21-fold) it was lower than in the control group (P = 0.037, P < 0.05), and the difference in OPN mRNA expression between HA group and HYL group also showed statistically significant (P = 0.001, P < 0.05); however, there was no significant difference between each group of the relative CD44 mRNA expression (P > 0.05). Our study showed that HA can upregulate OPN mRNA expression in OA fibroblast-like synoviocytes, and the high expression of OPN mRNA in OA may be a result of increased HA level of OA synovitis; however, HA cannot affect the CD44 mRNA expression in OA fibroblast-like synoviocytes, and the high expression of CD44 mRNA in OA may be not a result of increased HA level of OA synovitis.

Hyaluronan synthase HAS2 promotes tumor progression in bone by stimulating the interaction of breast cancer stem-like cells with macrophages and stromal cells

The molecular mechanisms that operate within the organ microenvironment to support metastatic progression remain unclear. Here, we report that upregulation of hyaluronan synthase 2 (HAS2) occurs in highly metastatic breast cancer stem-like cells (CSC) defined by CD44(+)/CD24(-)/ESA(+) phenotype, where it plays a critical role in the generation of a prometastatic microenvironment in breast cancer. HAS2 was critical for the interaction of CSCs with tumor-associated macrophages (TAM), leading to enhanced secretion of platelet-derived growth factor-BB from TAMs, which then activated stromal cells and enhanced CSC self-renewal. Loss of HAS2 in CSCs or treatment with 4-methylumbelliferone, an inhibitor of HAS, which blocks hyaluronan production, drastically reduced the incidence and growth of metastatic lesions in vitro or in vivo, respectively. Taken together, our findings show a critical role of HAS2 in the development of a prometastatic microenvironment and suggest that HAS2 inhibitors can act as antimetastatic agents that disrupt a paracrine growth factor loop within this microenvironment.

Osteopontin, asbestos exposure and pleural plaques: a cross-sectional study

Background

Osteopontin (OPN) is a plasma protein/cytokine produced in excess in several malignancies. In a recent study OPN was reported as being related to the duration of asbestos exposure and presence of benign asbestos-related diseases; however, it was unclear whether this protein was an indicator of exposure or effect.

Methods

In 193 workers, 50 with pleural plaques (PP), in whom different indicators of past asbestos exposure were estimated, OPN plasma levels were assessed using commercial quantitative sandwich enzyme immunoassays according to the manufacturer's instructions.

Results

Osteopontin increased with increasing age and several aspects of asbestos exposure, without differences related to the presence of pleural plaques. At multivariable regression analysis, the explanatory variables with a significant independent influence on OPN were length of exposure (positive correlation) and time elapsed since last exposure (positive correlation).

Conclusions

Since asbestos in lung tissue tends to wane over time, OPN should decrease (rather than increase) with time since last exposure. Therefore, OPN cannot be a reliable biomarker of exposure nor effect (presence of pleural plaques).

Specific expression of osteopontin and S100A6 in hepatocellular carcinoma

BACKGROUND

Our aim was to identify differential expression of genes in hepatocellular carcinoma (HCC) with the ultimate goal of discovering novel diagnostic and therapeutic targets.

METHODS

We examined differences in gene expression between HCC and noncancerous liver tissue using a cDNA array with probes for 15,843 genes/clones. Two genes, osteopontin (OPN) and S100A6, were found to be >10-fold differentially expressed, and were selected for further immunohistochemical staining in 51 HCC and 10 nonmalignant liver specimens. The relation between OPN and S100A6 alterations and various clinicopathologic parameters was also evaluated.

RESULTS

We found a total of 219 genes that were differentially expressed >3-fold. Of these, 109 were upregulated and 110 downregulated. Within this group, 123 genes, including 59 upregulated and 64 downregulated, had been identified previously. These known genes were mainly involved in cell migration, cytoskeleton dynamics, the signaling pathway and cell cycle, and metabolism. OPN expression and S100A6 expression were seen in 26 of 51 (51.0 %) and 16 of 51 (31.4 %) HCC samples, respectively. More importantly, proteins coded by these genes were not found in any noncancerous liver specimen by immunohistochemical analysis. Expression of these genes correlated with poor differentiation (OPN: P = .013; S100A6: P = .008).

CONCLUSION

OPN, a secreted phosphoprotein that has been increasingly implicated in the progression and metastasis of cancer, and S100A6, a member of the S100 protein family that can perform cell proliferation, differentiation, migration, and cytoskeletal dynamics, may be promising diagnostic markers and therapeutic targets for HCC. In addition, the results encourage future studies involving the roles of these proteins in the development and progression of this cancer.

Deletion of the thrombin cleavage domain of osteopontin mediates breast cancer cell adhesion, proteolytic activity, tumorgenicity, and metastasis

BACKGROUND

Osteopontin (OPN) is a secreted phosphoprotein often overexpressed at high levels in the blood and primary tumors of breast cancer patients. OPN contains two integrin-binding sites and a thrombin cleavage domain located in close proximity to each other.

METHODS

To study the role of the thrombin cleavage site of OPN, MDA-MB-468 human breast cancer cells were stably transfected with either wildtype OPN (468-OPN), mutant OPN lacking the thrombin cleavage domain (468-ΔTC) or an empty vector (468-CON) and assessed for in vitro and in vivo functional differences in malignant/metastatic behavior.

RESULTS

All three cell lines were found to equivalently express thrombin, tissue factor, CD44, αvβ5 integrin and β1 integrin. Relative to 468-OPN and 468-CON cells, 468-ΔTC cells expressing OPN with a deleted thrombin cleavage domain demonstrated decreased cell adhesion (p < 0.001), decreased mRNA expression of MCAM, maspin and TRAIL (p < 0.01), and increased uPA expression and activity (p < 0.01) in vitro. Furthermore, injection of 468-ΔTC cells into the mammary fat pad of nude mice resulted in decreased primary tumor latency time (p < 0.01) and increased primary tumor growth and lymph node metastatic burden (p < 0.001) compared to 468-OPN and 468-CON cells.

CONCLUSIONS

The results presented here suggest that expression of thrombin-uncleavable OPN imparts an early tumor formation advantage as well as a metastatic advantage for breast cancer cells, possibly due to increased proteolytic activity and decreased adhesion and apoptosis. Clarification of the mechanisms responsible for these observations and the translation of this knowledge into the clinic could ultimately provide new therapeutic opportunities for combating breast cancer.

Hedgehog signaling induced by breast cancer cells promotes osteoclastogenesis and osteolysis

Bone integrity is maintained by a dynamic equilibrium between the activities of bone-forming osteoblasts and bone-resorbing osteoclasts. Osteolytic lesions are a painful consequence of metastasis of breast cancer cells to bone in an overwhelming majority of breast cancer patients. Factors secreted by breast cancer cells propel a cascade of events that trigger osteoclastogenesis and elevated bone resorption. In the present study, we show that the Hedgehog (Hh) ligands secreted by breast cancer cells promote osteoclast differentiation and potentiate the activity of mature osteoclasts. Paracrine Hh signaling induced by breast cancer cells mediates a detrimental chain of events by the up-regulation of osteopontin (OPN), which in turn enhances osteoclastic activity by up-regulating cathepsin K and MMP9. Hh signaling is essential for osteoclasts because blocking the Hh pathway using the pharmacological Hh inhibitor, cyclopamine, results in an overall decrease in osteoclastogenesis and resorptive activity. Our studies suggest that inhibiting Hh signaling interferes with the ability of pre-osteoclasts to respond to the stimulatory effects of the breast cancer cells, indicating that Hh signaling is vital to osteoclast activity.

The transcription factor EGR1 regulates metastatic potential of v-src transformed sarcoma cells

Metastatic spreading of cancer cells is a highly complex process directed primarily by the interplay between tumor microenvironment, cell surface receptors, and actin cytoskeleton dynamics. To advance our understanding of metastatic cancer dissemination, we have developed a model system that is based on two v-src transformed chicken sarcoma cell lines-the highly metastatic parental PR9692 and a non-metastasizing but fully tumorigenic clonal derivative PR9692-E9. Oligonucleotide microarray analysis of both cell lines revealed that the gene encoding the transcription factor EGR1 was downregulated in the non-metastatic PR9692-E9 cells. Further investigation demonstrated that the introduction of exogenous EGR1 into PR9692-E9 cells restored their metastatic potential to a level indistinguishable from parental PR9692 cells. Microarray analysis of EGR1 reconstituted cells revealed the activation of genes that are crucial for actin cytoskeleton contractility (MYL9), filopodia formation (MYO10), the production of specific extracellular matrix components (HAS2, COL6A1-3) and other essential pro-metastatic abilities.

Role of the metastasis-promoting protein osteopontin in the tumour microenvironment

Osteopontin (OPN) is a secreted protein present in bodily fluids and tissues. It is subject to multiple post-translational modifications, including phosphorylation, glycosylation, proteolytic cleavage and crosslinking by transglutamination. Binding of OPN to integrin and CD44 receptors regulates signalling cascades that affect processes such as adhesion, migration, invasion, chemotaxis and cell survival. A variety of cells and tissues express OPN, including bone, vasculature, kidney, inflammatory cells and numerous secretory epithelia. Normal physiological roles include regulation of immune functions, vascular remodelling, wound repair and developmental processes. OPN also is expressed in many cancers, and elevated levels in patients’ tumour tissue and blood are associated with poor prognosis. Tumour growth is regulated by interactions between tumour cells and their tissue microenvironment. Within a tumour mass, OPN can be expressed by both tumour cells and cellular components of the tumour microenvironment, and both tumour and normal cells may have receptors able to bind to OPN. OPN can also be found as a component of the extracellular matrix. The functional roles of OPN in a tumour are thus complex, with OPN secreted by both tumour cells and cells in the tumour microenvironment, both of which can in turn respond to OPN. Much remains to be learned about the cross-talk between normal and tumour cells within a tumour, and the role of multiple forms of OPN in these interactions. Understanding OPN-mediated interactions within a tumour will be important for the development of therapeutic strategies to target OPN.

Overexpression of human osteopontin increases cell proliferation and migration in human embryo kidney-293 cells

Malignant tumors are characterized by dysregulated cell growth and the metastasis of secondary tumors. Numerous studies have documented that osteopontin (OPN) plays a key role in regulating tumor progression and metastasis. Here, we show that the overexpression of OPN in human embryo kidney-293 cells significantly increases both the level of cell proliferation, by provoking the G(1)/S transition, and the level of cell migration in vitro. These findings suggest that augmented OPN contributes to cell growth and motility. Inhibiting OPN or the pathway it stimulates may therefore represent a novel approach for the treatment of primary tumors and associated metastases.

Downregulation of osteopontin contributes to metastasis suppression by breast cancer metastasis suppressor 1

Breast cancer metastasis suppressor 1 (BRMS1) inhibits the ability of multiple human and murine cancer cell lines to metastasize to lymph nodes, bones and lungs. Comparison of mRNA expression in metastatic MDA-MB-435 human carcinoma cells (435) and metastasis-suppressed BRMS1 transfectants (435/BRMS1) showed a marked (>90%) reduction of osteopontin (OPN) mRNA and protein expression in BRMS1-overexpressing cells. OPN expression is associated with disease progression in patients, with higher levels of OPN produced by cancer cells associated with poorer patient survival. Furthermore, OPN has been suggested to promote survival of cancer cells in response to stress, although the mechanisms by which this may occur remain poorly understood. This study tested the hypothesis that re-expression of OPN in metastasis-suppressed 435/BRMS1 cells would reverse metastasis suppression and confer protection from stress-induced apoptosis. A stable pooled population of OPN overexpressing 435/BRMS1 cells was created (435/BRMS1/OPN). OPN re-expression did not affect in vitro cell growth rates; however, increased anchorage independent growth/survival and protection from hypoxia-induced apoptosis was observed (p < 0.05). In vivo, OPN re-expression in BRMS1 transfected cells did not affect in vivo primary tumor growth but did increase the incidence of spontaneous metastasis to lymph nodes and lungs in mice. These novel findings suggest that OPN downregulation by BRMS1 may be responsible, at least in part, for BRMS1-mediated metastasis suppression by sensitizing cancer cells to stress induced apoptosis. These studies clarify one mechanism by which BRMS1 can suppress metastasis.

CD44-epidermal growth factor receptor interaction mediates hyaluronic acid-promoted cell motility by activating protein kinase C signaling involving Akt, Rac1, Phox, reactive oxygen species, focal adhesion kinase, and MMP-2

Hyaluronic acid (HA) is known to play an important role in motility of tumor cells. However, the molecular mechanisms associated with HA-promoted melanoma cell motility are not fully understood. Treatment of cells with HA was shown to increase the production of reactive oxygen species (ROS) in a CD44-dependent manner. Antioxidants, such as N-acetyl-l-cysteine and seleno-l-methionine, prevented HA from enhancing cell motility. Protein kinase C (PKC)-alpha and PKCdelta were responsible for increased Rac1 activity, production of ROS, and mediated HA-promoted cell motility. HA increased Rac1 activity via CD44, PKCalpha, and PKCdelta. Transfection with dominant negative and constitutive active Rac1 mutants demonstrated that Rac1 was responsible for the increased production of ROS and cell motility by HA. Inhibition of NADPH oxidase by diphenylene iodonium and down-regulation of p47Phox and p67Phox decreased the ROS level, suggesting that NADPH oxidase is the main source of ROS production. Rac1 increased phosphorylation of FAK. FAK functions downstream of and is necessary for HA-promoted cell motility. Secretion and expression of MMP-2 were increased by treatment with HA via the action of PKCalpha, PKCdelta, and Rac1 and the production of ROS and FAK. Ilomastat, an inhibitor of MMP-2, exerted a negative effect on HA-promoted cell motility. HA increased interaction between CD44 and epidermal growth factor receptor (EGFR). AG1478, an inhibitor of EGFR, decreased phosphorylation of PKCalpha, PKCdelta, and Rac1 activity and suppressed induction of p47Phox and p67Phox. These results suggest that CD44-EGFR interaction is necessary for HA-promoted cell motility by regulating PKC signaling. EGFR-Akt interaction promoted by HA was responsible for the increased production of ROS and HA-promoted cell motility. In summary, HA promotes CD44-EGFR interaction, which in turn activates PKC signaling, involving Akt, Rac1, Phox, and the production of ROS, FAK, and MMP-2, to enhance melanoma cell motility.

Increased expression of osteopontin in patients with triple-negative breast cancer

BACKGROUND

Patients with triple-negative [oestrogen receptor (ER) negative, progesterone receptor (PR) negative, and human epidermal growth factor receptor 2 (HER-2/neu) negative] breast cancer, accounting for about 15% of breast cancer cases, are associated with aggressive histology, poor prognosis and shorter survival. Osteopontin is a chemokine-like phosphorylated glycoprotein that plays important role in cancer progression and is found to be a metastasis-associated protein in breast cancer. The goal of the study was to evaluate osteopontin protein expression levels in triple-negative breast carcinomas to determine if they correlated with clinicopathological parameters, thus providing additional support for osteopontin functioning and better understanding of triple-negative breast cancer.

MATERIALS AND METHODS

A database of 239 patients, in whom all three markers (ER, PR, and HER-2/neu) were available, was reviewed. We performed osteopontin protein expression analyses by means of immunohistochemistry on 117 breast carcinoma tissue samples, and then assessed the mean value of osteopontin expression against triple-negative status and clinicopathological parameters.

RESULTS

Of the 239 patients in the study, 47 were classified as triple negative. Of the 117 osteopontin-test patients in this cohort, mean osteopontin levels were significantly higher in the triple-negative breast cancers than in non-triple-negative subtype (P = 0.035). TNM (tumours, nodes, metastases) stage were significantly associated with osteopontin levels (P = 0.038). Univariate analysis showed tumour cell osteopontin positivity above an optimized cut-point to be significantly associated with decreased disease-free survival, but not overall survival. In the multivariate model, osteopontin was an independent prognostic factor for disease-free survival.

CONCLUSIONS

Patients with osteopontin overexpression develop predominantly triple-negative tumours. Osteopontin overexpression is associated with tumour aggressiveness and poor prognosis.

Breast tumor microenvironment: proteomics highlights the treatments targeting secretome

Tumor secreted substances (secretome), including extracellular matrix (ECM) components, act as mediators of tumor-host communication in the breast tumor microenvironment. Proteomic analysis has emphasized the value of the secretome as a source of prospective markers and drug targets for the treatment of breast cancers. Utilizing bioinformatics, our recent studies revealed global changes in protein expression after the activation of ECM-mediated signaling in breast cancer cells. A newly designed technique integrating a capillary ultrafiltration (CUF) probe with mass spectrometry was demonstrated to dynamically sample and identify in vivo and pure secretome from the tumor microenvironment. Such in vivo profiling of breast cancer secretomes may facilitate the development of novel drugs specifically targeting secretome.

The thrombin inhibitor Argatroban reduces breast cancer malignancy and metastasis via osteopontin-dependent and osteopontin-independent mechanisms

Osteopontin (OPN) has been clinically and experimentally associated with breast cancer metastasis. Proteolytic cleavage of OPN by thrombin has been reported to increase its biologic activity. The purpose of this study was to determine if inhibition of thrombin could reduce the malignancy-promoting effects of OPN on breast cancer cell behavior in vitro and in vivo. MDA-MB-468 human breast cancer cells were stably transfected to overexpress OPN (468-OPN) or a control vector (468-CON) and compared for functional differences in malignant/metastatic behavior in response to treatment with the thrombin-specific inhibitor Argatroban. Western blot analysis revealed that both 468-CON and 468-OPN cells produce thrombin and the thrombin-related protein tissue factor, and express very low levels of thrombin receptor (PAR-1). In vitro assays demonstrated that Argatroban treatment (25 microg/ml) of 468-OPN cells resulted in decreased cell growth, colony-forming ability, adhesion, and migration relative to untreated controls (P < 0.05), but did not have a significant effect on 468-CON cells. Following mammary fat pad injection, treatment with Argatroban (9 mg/kg/day) increased the in vivo tumor latency of both 468-CON and 468-OPN cells, and reduced primary tumor growth of 468-OPN cells (relative to untreated controls; P < 0.05). Furthermore, Argatroban treatment significantly decreased lymphatic metastasis of both 468-CON (P < 0.04) and 468-OPN (P < 0.01) cells relative to untreated controls. These novel findings indicate that inhibition of thrombin can reduce malignant and metastatic behavior of MDA-MB-468 breast cancer cells using both OPN-dependent and OPN-independent mechanisms, and suggest that thrombin inhibitors such as Argatroban may hold potential as therapeutic agents to combat breast cancer progression.

Pathophysiological role of osteopontin in hepatic inflammation, toxicity, and cancer

Osteopontin (OPN) is a highly modified integrin-binding extracellular matrix glycophosphoprotein produced by cells of the immune system, epithelial tissue, smooth muscle cells, osteoblasts, and tumor cells. Extensive research has elucidated the pivotal role of OPN in cell signaling that controls inflammation, tumor progression, and metastasis. OPN interaction with the integrin receptors expressed on inflammatory cells through its arginine-glycine-aspartate (RGD) and non-RGD motifs promote migration and adhesion of cells. In the liver, it has been reported that hepatic Kupffer cells secrete OPN facilitating macrophage infiltration into necrotic areas following carbon tetrachloride liver toxicity. Recent work has highlighted the role of OPN in inflammatory liver diseases such as alcoholic and nonalcoholic liver disease and T-cell-mediated hepatitis. The role of OPN in hepatocellular carcinoma (HCC) has also generated significant interest, especially with regards to its role as a prognostic factor. OPN therefore appears to play an important role during liver inflammation and cancer. In this review we will present data to demonstrate the key role played by OPN in mediating hepatic inflammation (neutrophils, monocytes/macrophages, and lymphocytes) and its role in HCC. Greater understanding of the pathophysiologic role of OPN in hepatic inflammation and cancer may enable development of novel inflammation and cancer treatment strategies.

Putative role of hyaluronan and its related genes, HAS2 and RHAMM, in human early preimplantation embryogenesis and embryonic stem cell characterization

Human embryonic stem cells (hESC) promise tremendous potential as a developmental and cell therapeutic tool. The combined effort of stimulatory and inhibitory signals regulating gene expression, which drives the tissue differentiation and morphogenetic processes during early embryogenesis, is still very poorly understood. With the scarcity of availability of human embryos for research, hESC can be used as an alternative source to study the early human embryogenesis. Hyaluronan (HA), a simple hydrating sugar, is present abundantly in the female reproductive tract during fertilization, embryo growth, and implantation and plays an important role in early development of the mammalian embryo. HA and its binding protein RHAMM regulate various cellular and hydrodynamic processes from cell migration, proliferation, and signaling to regulation of gene expression, cell differentiation, morphogenesis, and metastasis via both extracellular and intracellular pathways. In this study, we show for the first time that HA synthase gene HAS2 and its binding receptor RHAMM are differentially expressed during all stages of preimplantation human embryos and hESC. RHAMM expression is significantly downregulated during differentiation of hESC, in contrast to HAS2, which is significantly upregulated. Most importantly, RHAMM knockdown results in downregulation of several pluripotency markers in hESC, induction of early extraembryonic lineages, loss of cell viability, and changes in hESC cycle. These data therefore highlight an important role for RHAMM in maintenance of hESC pluripotency, viability, and cell cycle control. Interestingly, HAS2 knockdown results in suppression of hESC differentiation without affecting hESC pluripotency. This suggests an intrinsic role for HAS2 in hESC differentiation process. In accordance with this, addition of exogenous HA to the differentiation medium enhances hESC differentiation to mesodermal and cardiac lineages. Disclosure of potential conflicts of interest is found at the end of this article.

Hyaluronic acid induces transglutaminase II to enhance cell motility; role of Rac1 and FAK in the induction of transglutaminase II

The role of transglutaminase II (TGase II) in hyaluronic acid (HA)-promoted melanoma cell motility was investigated. HA induced the expression of TGase II via the nuclear factor kappaB (NF-kB) in melanoma cells. HA increased the Rac1 activity and phosphorylation of focal adhesion kinase (FAK). Transfection by lipofectamine of dominant-negative Rac1, and FAK-related non-kinase (FRNK), an endogenous inhibitor of FAK, suppressed the induction of TGase II. This suggests that Rac1 and FAK mediate induction of TGase II by HA. HA-promoted melanoma cell motility was inhibited by cystamine, an inhibitor of TGase II, and overexpression of TGase II enhanced melanoma cell motility through reactive oxygen species. Taken together, HA promotes melanoma cell motility through activation of Rac1, FAK, and induction of TGase II.

Heregulin-mediated ErbB2-ERK signaling activates hyaluronan synthases leading to CD44-dependent ovarian tumor cell growth and migration

Heregulin (HRG)-induced cell responses are mediated by the ErbB family of tyrosine kinase receptors. In this study we have investigated HRG activation of ErbB2, extracellular signal-regulated kinase (ERK) signaling, and their role in regulating hyaluronan synthase (HAS) activity in human ovarian tumor cells (SK-OV-3.ipl cells). Immunological and biochemical analyses indicate that ErbB2, ErbB3, and ErbB4 are all expressed in SK-OV-3.ipl cells and that ErbB4 (but not ErbB3) is physically linked to ErbB2 following HRG stimulation. Furthermore, our data indicate that the HRG-induced ErbB2.ErbB4 complexes stimulate ErbB2 tyrosine kinase, which induces both ERK phosphorylation and kinase activity. The activated ERK then increases the phosphorylation of HAS1, HAS2, and HAS3. Consequently, all three HAS isozymes are activated resulting in hyaluronan (HA) production. Because HRG-mediated HAS isozyme phosphorylation/activation can be effectively blocked by either AG825 (an ErbB2 inhibitor) or thiazolidinedione compound (an ERK blocker), we conclude that ErbB2-ERK signaling and HAS isozyme phosphorylation/HA production are functionally coupled in SK-OV-3.ipl cells. HRG also promotes HA- and CD44-dependent oncogenic events (e.g. CD44-Cdc42 association, p21-activated kinase 1 activation, and p21-activated kinase 1-filamin complex formation) and tumor cell-specific behaviors in an ErbB2-ERK signaling-dependent manner. Finally, we have found that the down-regulation of HAS isozyme expression (by transfecting cells with HAS1/HAS2/HAS3-specific small interfering RNAs) not only inhibits HRG-mediated HAS phosphorylation/activation and HA production but also impairs CD44-specific Cdc42-PAK1/filamin signaling, cytoskeleton activation and tumor cell behaviors. Taken together, these findings clearly indicate that HRG activation of ErbB2-ERK signaling modulates HAS phosphorylation/activation and HA production leading to CD44-mediated oncogenic events and ovarian cancer progression.

Osteopontin overexpression in breast cancer: Knowledge gained and possible implications for clinical management

Osteopontin (OPN) is a secreted protein that is overexpressed in a number of human cancers, and has been associated with increased metastatic burden and poor prognosis in breast cancer patients. The OPN protein contains several conserved structural elements including heparin- and calcium-binding domains, a thrombin-cleavage site, a CD44 binding site, and two integrin-binding sites. Experimental studies have shown that the ability of OPN to interact with a diverse range of factors, including cell surface receptors (integrins, CD44), secreted proteases (matrix metalloproteinases, urokinase plasminogen activator), and growth factor/receptor pathways (TGFalpha/EGFR, HGF/Met) is central to its role in malignancy. These complex signaling interactions can result in changes in gene expression, which ultimately lead to alterations in cell properties involved in malignancy such as adhesion, migration, invasion, enhanced tumor cell survival, tumor angiogenesis, and metastasis. Therefore, OPN is not merely associated with cancer, but rather it plays a multi-faceted functional role via complex molecular cross-talk with other factors. This review will focus on the role of OPN in breast cancer, in particular on the malignancy-promoting aspects of OPN that may reveal opportunities for new approaches to the clinical management of breast cancer.