Osteopontin stimulates cell motility and nuclear factor kappaB-mediated secretion of urokinase type plasminogen activator through phosphatidylinositol 3-kinase/Akt signaling pathways in breast cancer cells

Enzyme-free and rapid colorimetric analysis of osteopontin via triple-helix aptamer probe coupled with catalytic hairpin assembly reaction

BACKGROUND

Osteopontin (OPN) is closely associated with tumorigenesis, growth, invasion, and immune escape and it serves as a plasma biomarker for hepatocellular carcinoma (HCC). Nevertheless, the accurate and rapid detection of low-abundance OPN still poses significant challenges. Currently, the majority of protein detection methods rely heavily on large precision instruments or involve complex procedures. Therefore, developing a simple, enzyme-free, rapid colorimetric analysis method with high sensitivity is imperative.

RESULTS

In this study, we have developed a portable colorimetric biosensor by integrating the triple-helix aptamer probe (THAP) and catalytic hairpin assembly (CHA) strategy, named as T-CHA. After binding to the OPN, the trigger probe can be released from THAP, then initiates the CHA reaction and outputs the signal through the formation of a G-quadruplex/Hemin DNAzyme with horseradish peroxidase-like activity. Consequently, this colorimetric sensor achieves visual free-labeled detection without additional fluorophore modification and allows for accurate quantification by measuring the optical density of the solution at 650 nm. Under optimal conditions, the logarithmic values of various OPN concentrations exhibit satisfactory linearity in the range of 5 pg mL-1 to 5 ng mL-1, with a detection limit of 2.04 pg mL-1. Compared with the widely used ELISA strategy, the proposed T-CHA strategy is rapid (∼105 min), highly sensitive, and cost-effective.

SIGNIFICANCE

The T-CHA strategy, leveraging the low background leakage of THAP and the high catalytic efficiency of CHA, has been successfully applied to the detection of OPN in plasma, demonstrating significant promise for the early diagnosis of HCC in point-of-care testing. Given the programmability of DNA and the universality of T-CHA, it can be readily modified for analyzing other useful tumor biomarkers.

A Novel MAO-B/SSAO Inhibitor Improves Multiple Aspects of Dystrophic Phenotype in mdx Mice

Duchenne muscular dystrophy (DMD) is one of the most frequent and severe childhood muscle diseases. Its pathophysiology is multifaceted and still incompletely understood, but we and others have previously shown that oxidative stress plays an important role. In particular, we have demonstrated that inhibition of mitochondrial monoamine oxidases could improve some functional and biohumoral markers of the pathology. In the present study we report the use of dystrophic mdx mice to evaluate the efficacy of a dual monoamine oxidase B (MAO-B)/semicarbazide-sensitive amine oxidase (SSAO) inhibitor, PXS-5131, in reducing inflammation and fibrosis and improving muscle function. We found that a one-month treatment starting at three months of age was able to decrease reactive oxygen species (ROS) production, fibrosis, and inflammatory infiltrate in the tibialis anterior (TA) and diaphragm muscles. Importantly, we also observed a marked improvement in the capacity of the gastrocnemius muscle to maintain its force when challenged with eccentric contractions. Upon performing a bulk RNA-seq analysis, PXS-5131 treatment affected the expression of genes involved in inflammatory processes and tissue remodeling. We also studied the effect of prolonged treatment in older dystrophic mice, and found that a three-month administration of PXS-5131 was able to greatly reduce the progression of fibrosis not only in the diaphragm but also in the heart. Taken together, these results suggest that PXS-5131 is an effective inhibitor of fibrosis and inflammation in dystrophic muscles, a finding that could open a new therapeutic avenue for DMD patients.

NF-κB signaling in neoplastic transition from epithelial to mesenchymal phenotype

NF-κB transcription factors are critical regulators of innate and adaptive immunity and major mediators of inflammatory signaling. The NF-κB signaling is dysregulated in a significant number of cancers and drives malignant transformation through maintenance of constitutive pro-survival signaling and downregulation of apoptosis. Overactive NF-κB signaling results in overexpression of pro-inflammatory cytokines, chemokines and/or growth factors leading to accumulation of proliferative signals together with activation of innate and select adaptive immune cells. This state of chronic inflammation is now thought to be linked to induction of malignant transformation, angiogenesis, metastasis, subversion of adaptive immunity, and therapy resistance. Moreover, accumulating evidence indicates the involvement of NF-κB signaling in induction and maintenance of invasive phenotypes linked to epithelial to mesenchymal transition (EMT) and metastasis. In this review we summarize reported links of NF-κB signaling to sequential steps of transition from epithelial to mesenchymal phenotypes. Understanding the involvement of NF-κB in EMT regulation may contribute to formulating optimized therapeutic strategies in cancer. Video Abstract.

Thrombin Cleavage of Osteopontin and the Host Anti-Tumor Immune Response

Osteopontin (OPN) is a multi-functional protein that is involved in various cellular processes such as cell adhesion, migration, and signaling. There is a single conserved thrombin cleavage site in OPN that, when cleaved, yields two fragments with different properties from full-length OPN. In cancer, OPN has tumor-promoting activity and plays a role in tumor growth and metastasis. High levels of OPN expression in cancer cells and tumor tissue are found in various types of cancer, including breast, lung, prostate, ovarian, colorectal, and pancreatic cancer, and are associated with poor prognosis and decreased survival rates. OPN promotes tumor progression and invasion by stimulating cell proliferation and angiogenesis and also facilitates the metastasis of cancer cells to other parts of the body by promoting cell adhesion and migration. Furthermore, OPN contributes to immune evasion by inhibiting the activity of immune cells. Thrombin cleavage of OPN initiates OPN's tumor-promoting activity, and thrombin cleavage fragments of OPN down-regulate the host immune anti-tumor response.

Lateral flow assays for detection of disease biomarkers

Early diagnosis saves lives in many diseases. In this sense, monitoring of biomarkers is crucial for the diagnosis of diseases. Lateral flow assays (LFAs) have attracted great attention among paper-based point-of-care testing (POCT) due to their low cost, user-friendliness, and time-saving advantages. Developments in the field of health have led to an increase of interest in these rapid tests. LFAs are used in the diagnosis and monitoring of many diseases, thanks to biomarkers that can be observed in body fluids. This review covers the recent advances dealing with the design and strategies for the development of LFA for the detection of biomarkers used in clinical applications in the last 5 years. We focus on various strategies such as choosing the nanoparticle type, single or multiple test approaches, and equipment for signal transducing for the detection of the most common biomarkers in different diseases such as cancer, cardiovascular, infectious, and others including Parkinson's and Alzheimer's diseases. We expect that this study will contribute to the different approaches in LFA and pave the way for other clinical applications.

Endocrine regulation and metabolic mechanisms of osteopontin in the development and progression of osteosarcoma, metastasis and prognosis

Osteosarcoma is the most common type of malignant bone tumor, occurring in adolescents and patients over 60. It has a bimodal onset and a poor prognosis, and its development has not yet been fully explained. Osteopontin (OPN) is a high protein consisting of 314 amino acid residues with a negative charge and is involved in many biological activities. OPN is not only an essential part of the regulation of the nervous system and endocrine metabolism of skeletal cells. Still, it is also involved in several other important biological activities, such as the division, transformation, and proliferation of skeletal cells and their associated cells, such as bone tumor cells, including bone marrow mesenchymal stem cells, hematopoietic stem cells, osteoblasts, and osteoclasts. Osteoblasts and osteocytes. Recent studies have shown a strong correlation between OPN and the development and progression of many skeletal diseases, such as osteosarcoma and rheumatoid arthritis. This review aims to understand the mechanisms and advances in the role of OPN as a factor in the development, progression, metastasis, and prognosis of osteosarcoma in an attempt to provide a comprehensive summary of the mechanisms by which OPN regulates osteosarcoma progression and in the hope of contributing to the advancement of osteosarcoma research and clinical treatment.

Suppression of breast cancer-associated bone loss with osteoblast proteomes via Hsp90ab1/moesin-mediated inhibition of TGFβ/FN1/CD44 signaling

Background: Bone is a frequent site of metastases from breast cancer, but existing therapeutic options are not satisfactory. Although osteoblasts have active roles in cancer progression by assisting the vicious bone-destructive cycle, we employed a counterintuitive approach of activating pro-tumorigenic Wnt signaling and examined the paradoxical possibility of developing osteoblast-derived tumor-suppressive, bone-protective secretomes. Methods: Wnt signaling was activated by the overexpression of Lrp5 and β-catenin in osteoblasts as well as a pharmacological agent (BML284), and the therapeutic effects of their conditioned medium (CM) were evaluated using in vitro cell cultures, ex vivo breast cancer tissues, and a mouse model of osteolysis. To explore the unconventional regulatory mechanism of the action of Wnt-activated osteoblasts, whole-genome proteomics analysis was conducted, followed by immunoprecipitation and gain- and loss-of-function assays. Results: While osteoblasts did not present any innate tumor-suppressing ability, we observed that the overexpression of Lrp5 and β-catenin in Wnt signaling made their CM tumor-suppressive and bone-protective. The growth of breast cancer cells and tissues was inhibited by Lrp5-overexpressing CM (Lrp5 CM), which suppressed mammary tumors and tumor-driven bone destruction in a mouse model. Lrp5 CM also inhibited the differentiation and maturation of bone-resorbing osteoclasts by downregulating NFATc1 and cathepsin K. The overexpression of Lrp5 upregulated osteopontin that enriched Hsp90ab1 (Hsp90 beta) and moesin (MSN) in Lrp5 CM. Hsp90ab1 and MSN are atypical tumor-suppressing proteins since they are multi-tasking, moonlighting proteins that promote tumorigenesis in tumor cells. Importantly, Hsp90ab1 immuno-precipitated latent TGFβ and inactivated TGFβ, whereas MSN interacted with CD44, a cancer stem-cell marker, as well as fibronectin 1, an ECM protein. Furthermore, Hsp90ab1 and MSN downregulated KDM3A that demethylated histones, together with PDL1 that inhibited immune responses. Conclusion: In contrast to inducing tumor-enhancing secretomes and chemoresistance in general by inhibiting varying oncogenic pathways in chemotherapy, this study presented the unexpected outcome of generation tumor-suppressive secretomes by activating the pro-tumorigenic Wnt pathway. The results shed light on the contrasting role of oncogenic signaling in tumor cells and osteoblast-derived secretomes, suggesting a counterintuitive option for the treatment of breast cancer-associated bone metastasis.

Aptamer grafted nanoparticle as targeted therapeutic tool for the treatment of breast cancer

Breast carcinomas repeat their number and grow exponentially making it extremely frequent malignancy among women. Approximately, 70-80% of early diagnosed or non-metastatic conditions are treatable while the metastatic cases are considered ineffective to treat with current ample amount of therapy. Target based anti-cancer treatment has been in the limelight for decades and is perceived significant consideration of scientists. Aptamers are the 'coming of age' therapeutic approach, selected using an appropriate tool from the library of sequences. Aptamers are non-immunogenic, stable, and high-affinity ligand which are poised to reach the clinical benchmark. With the heed in nanoparticle application, the delivery of aptamer to the specific site could be enhanced which also protects them from nuclease degradation. Moreover, nanoparticles due to robust structure, high drug entrapment, and modifiable release of cargo could serve as a successful candidate in the treatment of breast carcinoma. This review would showcase the method and modified method of selection of aptamers, aptamers that were able to make its way towards clinical trial and their targetability and selectivity towards breast cancers. The appropriate usage of aptamer-based biosensor in breast cancer diagnosis have also been discussed.

Evaluation of SPP1/osteopontin expression as predictor of recurrence in tamoxifen treated breast cancer

Breast cancer patients treated with tamoxifen may experience recurrence due to endocrine resistance, which highlights the need for additional predictive and prognostic biomarkers. The glyco-phosphoprotein osteopontin (OPN), encoded by the SPP1 gene, has previously shown to be associated with poor prognosis in breast cancer. However, studies on the predictive value of OPN are inconclusive. In the present study, we evaluated tissue SPP1 mRNA and OPN protein expression as markers of recurrence in estrogen receptor- positive (ER+) breast cancer tissue. Tamoxifen- treated patients with recurrence or non-recurrence were selected using a matched case-control design. SPP1 mRNA expression was analysed using qPCR (n = 100) and OPN protein by immunohistochemistry (n = 116) using different antibodies. Odds ratios were estimated with conditional logistic regression. The SPP1 expression increased the risk of recurrence with an odds ratio (OR) of 2.50 (95% confidence interval [CI]; 1.30–4.82), after adjustment for tumour grade, HER 2 status and other treatments to OR 3.62 (95% CI; 1.45–9.07). However, OPN protein expression was not associated with risk of recurrence or with SPP1-gene expression, suggesting SPP1 mRNA a stronger prognostic marker candidate compared to tumor tissue OPN protein.

A highly sensitive and specific lateral flow aptasensor for the detection of human osteopontin

The rapid determination of human osteopontin (OPN) protein, a potential cancer biomarker, holds substantial promise for point-of-care diagnostics and biomedical applications. To date, most reported platforms for OPN detection are apparatus-dependent, time-consuming, and expensive. Herein, we established a lateral flow biosensor (LFB) for OPN detection. A biotinylated aptamer was used for OPN pre-capture from samples, an antibody for OPN was immobilized on the test line for a second specific target identification, and streptavidin-modified gold nanoparticles were sprayed on the conjugation pad for color detection. This LFB achieved as low as 0.1 ng mL^-1 OPN sensitivity with a good dynamic detection between 10 and 500 ng mL^-1 within 5 min. Intriguingly, the LFB allowed a qualitative and semi-quantitative detection of OPN in serum at clinically cut-off levels as in cancer patients, and can discriminate OPN from interfering proteins with high specificity. Thus, it is a promising alterative approach for point-of-care OPN screening and detection.

Curcumin and o-Vanillin Exhibit Evidence of Senolytic Activity in Human IVD Cells In Vitro

Curcumin and o-Vanillin cleared senescent intervertebral disc (IVD) cells and reduced the senescence-associated secretory phenotype (SASP) associated with inflammation and back pain. Cells from degenerate and non-mildly-degenerate human IVD were obtained from organ donors and from patients undergoing surgery for low back pain. Gene expression of senescence and SASP markers was evaluated by RT-qPCR in isolated cells, and protein expression of senescence, proliferation, and apoptotic markers was evaluated by immunocytochemistry (ICC). The expression levels of SASP factors were evaluated by enzyme-linked immunosorbent assay (ELISA). Matrix synthesis was verified with safranin-O staining and the Dimethyl-Methylene Blue Assay for proteoglycan content. Western blotting and ICC were used to determine the molecular pathways targeted by the drugs. We found a 40% higher level of senescent cells in degenerate compared to non-mildly-degenerate discs from unrelated individuals and a 10% higher level in degenerate compared to non-mildly-degenerate discs from the same individual. Higher levels of senescence were associated with increased SASP. Both drugs cleared senescent cells, and treatment increased the number of proliferating as well as apoptotic cells in cultures from degenerate IVDs. The expression of SASP factors was decreased, and matrix synthesis increased following treatment. These effects were mediated through the Nrf2 and NFkB pathways.

Osteopontin as a biomarker for osteosarcoma therapy and prognosis

Osteosarcoma (OS) is the most common bone malignancy, and is particularly prevalent in children and adolescents. OS is an aggressive tumor with a tendency to metastasize and invade to para-carcinoma tissues. The primary treatment for this tumor is a combination of surgery and chemotherapy. However, the prognosis remains poor due to chemoresistance and early metastasis. Osteopontin (OPN), a multifunctional secreted protein, has emerged as an important potential biomarker for diagnosing and treating cancer. The overexpression of OPN has been found in numerous malignant tumors, including breast, lung, gastric and ovarian cancer, as well as melanoma. Recent studies have suggested that OPN may provide an important function in the diagnosis and treatment of OS. The present review summarizes current knowledge and progress in understanding the potential role of OPN as a biomarker in OS.

Perinatal Hypoxic-Ischemic Encephalopathy and Neuroprotective Peptide Therapies: A Case for Cationic Arginine-Rich Peptides (CARPs)

Perinatal hypoxic-ischemic encephalopathy (HIE) is the leading cause of mortality and morbidity in neonates, with survivors suffering significant neurological sequelae including cerebral palsy, epilepsy, intellectual disability and autism spectrum disorders. While hypothermia is used clinically to reduce neurological injury following HIE, it is only used for term infants (>36 weeks gestation) in tertiary hospitals and improves outcomes in only 30% of patients. For these reasons, a more effective and easily administrable pharmacological therapeutic agent, that can be used in combination with hypothermia or alone when hypothermia cannot be applied, is urgently needed to treat pre-term (≤36 weeks gestation) and term infants suffering HIE. Several recent studies have demonstrated that cationic arginine-rich peptides (CARPs), which include many cell-penetrating peptides [CPPs; e.g., transactivator of transcription (TAT) and poly-arginine-9 (R9; 9-mer of arginine)], possess intrinsic neuroprotective properties. For example, we have demonstrated that poly-arginine-18 (R18; 18-mer of arginine) and its D-enantiomer (R18D) are neuroprotective in vitro following neuronal excitotoxicity, and in vivo following perinatal hypoxia-ischemia (HI). In this paper, we review studies that have used CARPs and other peptides, including putative neuroprotective peptides fused to TAT, in animal models of perinatal HIE. We critically evaluate the evidence that supports our hypothesis that CARP neuroprotection is mediated by peptide arginine content and positive charge and that CARPs represent a novel potential therapeutic for HIE.

Krüppel-like factor 17 inhibits urokinase plasminogen activator gene expression to suppress cell invasion through the Src/p38/ MAPK signaling pathway in human lung adenocarcionma

Krüppel-like factor 17 (KLF17) has been reported to be involved in invasion and metastasis suppression in lung cancer, but the molecular mechanisms underlying the anti-invasion and anti-metastasis roles of KLF17 in lung cancer are not fully illustrated. Here, we showed that KLF17 inhibited the invasion of A549 and H322 cells; the anti-invasion effect of KLF17 was associated with the suppression of urokinase plasminogen activator (uPA/PLAU) expression. KLF17 can bind with the promoter of uPA and inhibit its expression. Enforced expression of uPA abrogated the anti-invasion effect of KLF17 in A549 and H322 cells. In addition, immunohistochemistry staining showed that the protein expression of KLF17 was negatively correlated with that of uPA in archived samples from patients with lymph node metastasis of lung adenocarcinoma (rho = −0.62, P = 0.01). The mutually exclusive expression of KLF17 with uPA could predict lymph node metastasis for lung adenocarcinoma (AUC = 0.758, P = 0.005). Enforced expression of KLF17 inhibited the expression of phosphorylated Src and phosphorylated p38/MAPK in A549 and H322 cells. The invasiveness of the cells were suppressed by treating with sb203580 (p38/MAPK inhibitor) or HY-13805 (PP2, Src inhibitor). furthermore, p38/MAPK inhibition could block the KLF17-induced reduction of p-p38/MAPK and uPA, and Src inhibition enhanced the KLF17-induced suppression of p-Src and uPA in A549 and H322 cells. In conclusion, our study indicated that KLF17 suppressed the uPA-mediated invasion of lung adenocarcinoma. The Src and p38/MAPK signaling pathways were suggested as mediators of KLF17-induced uPA inhibition, thus providing evidence that KLF17 might be a potential anti-invasion candidate for lung adenocarcinoma.

Biological role of site-specific O-glycosylation in cell adhesion activity and phosphorylation of osteopontin

Osteopontin (OPN) is an extracellular glycosylated phosphoprotein that promotes cell adhesion by interacting with several integrin receptors. We previously reported that an OPN mutant lacking five O-glycosylation sites (Thr¹³⁴/Thr¹³⁸/Thr¹⁴³/Thr¹⁴⁷/Thr¹⁵²) in the threonine/proline-rich region increased cell adhesion activity and phosphorylation compared with the wild type. However, the role of O-glycosylation in cell adhesion activity and phosphorylation of OPN remains to be clarified. Here, we show that site-specific O-glycosylation in the threonine/proline-rich region of OPN affects its cell adhesion activity and phosphorylation independently and/or synergistically. Using site-directed mutagenesis, we found that OPN mutants with substitution sets of Thr¹³⁴/Thr¹³⁸ or Thr¹⁴³/Thr¹⁴⁷/Thr¹⁵² had decreased and increased cell adhesion activity, respectively. In contrast, the introduction of a single mutation into the O-glycosylation sites had no effect on OPN cell adhesion activity. An adhesion assay using function-blocking antibodies against αvβ3 and β1 integrins, as well as αvβ3 integrin-overexpressing A549 cells, revealed that site-specific O-glycosylation affected the association of OPN with the two integrins. Phosphorylation analyses using phos-tag and LC-MS/MS indicated that phosphorylation levels and sites were influenced by the O-glycosylation status, although the number of O-glycosylation sites was not correlated with the phosphorylation level in OPN. Furthermore, a correlation analysis between phosphorylation level and cell adhesion activity in OPN mutants with the site-specific O-glycosylation showed that they were not always correlated. These results provide conclusive evidence of a novel regulatory mechanism of cell adhesion activity and phosphorylation of OPN by site-specific O-glycosylation.

Dapper homolog 1 alpha suppresses metastasis ability of gastric cancer through inhibiting planar cell polarity pathway

Dapper homolog 1 alpha (DACT1α) is a member of DACT family and an important regulator in the planar cell polarity pathway. We aim to clarify its functional role in metastasis ability of gastric cancer. DACT1α was silenced in all gastric cancer cell lines (8/8), but expressed in normal gastric tissue. Ectopic expression of DACT1α in silenced gastric cancer cell lines (AGS, BGC823 and MGC803) by stable transfection significantly suppressed cancer cell spreading (P < 0.05), migration (P < 0.01) and invasion (P < 0.01). These effects were associated with downregulation of planar cell polarity pathway related genes involved in cell proliferation (PDGFB, VEGFA), adhesion (ITGA1, ITGA2, ITGA3, ITGB3) and migration/invasion (PLAU, MMP9, MCAM, Dvl-2 and JNK). DACT1α promoter methylation was detected in 205 gastric cancers and 20 normal controls by direct bisulfite genomic sequencing. DACT1α methylation was detected in 29.3% (60/205) of gastric cancer patients, but not in normal tissues. DACT1α methylation was associated with poor survival of gastric cancer patients. In conclusion, DACT1α plays a pivotal role as a potential tumor suppressor in migration and invasion of gastric cancer. DACT1α methylation may serve as a biomarker for the prognosis of gastric cancer.

Prognostic implications of the co-detection of the urokinase plasminogen activator system and osteopontin in patients with non-small-cell lung cancer undergoing radiotherapy and correlation with gross tumor volume

BACKGROUND

The urokinase plasminogen activator system (uPA, uPAR, PAI‑1) is upregulated in cancer and high plasma levels are associated with poor prognosis. Their interaction with hypoxia-related osteopontin (OPN) which is also overexpressed in malignant tumors suggests potential clinical relevance. However, the prognostic role of the uPA system in the radiotherapy (RT) of non-small-cell lung cancer (NSCLC), particularly in combination with OPN, has not been investigated so far.

METHODS

uPA, uPAR, PAI‑1 and OPN plasma levels of 81 patients with locally advanced or metastasized NSCLC were prospectively analyzed by ELISA before RT and were correlated to clinical patient/tumor data and prognosis after RT.

RESULTS

uPAR plasma levels were higher in M1; uPA and PAI‑1 levels were higher in M0 NSCLC patients. uPAR correlated with uPA (p < 0.001) which also correlated with PAI‑1 (p < 0.001). The prognostic impact of OPN plasma levels in the RT of NSCLC was previously reported by our group. PAI‑I plasma levels significantly impacted overall (OS) and progression-free survival (PFS). Low PAI‑1 levels were associated with a significantly reduced OS and PFS with a nearly 2‑fold increased risk of death (p = 0.029) and tumor progression (p = 0.029). In multivariate analysis, PAI‑1 levels remained an independent prognostic factor for OS and PFS with a 3‑fold increased risk of death (p = 0.001). If PAI‑1 plasma levels were combined with OPN or tumor volume, we found an additive prognostic impact on OS and PFS with a 2.5- to 3‑fold increased risk of death (p = 0.01).

CONCLUSION

Our results suggest that PAI-1 but not uPA and uPAR might add prognostic information in patients with advanced NSCLC undergoing RT. High pretreatment PAI-1 plasma levels were found predominantly in M0-stage patients and indicate a favorable prognosis as opposed to OPN where high plasma levels are associated with poor survival and metastasis. In combination, PAI-1 and OPN levels successfully predicted outcome and additively correlated with prognosis. These findings support the notion of an antidromic prognostic impact of OPN and PAI-1 plasma levels in the RT of advanced NSCLC.

Cancer-associated Fibroblast-derived IL-6 Promotes Head and Neck Cancer Progression via the Osteopontin-NF-kappa B Signaling Pathway

Osteopontin (OPN), a chemokine-like protein, plays a crucial role in the proliferation and metastasis of various cancers. However, how tumor stroma modulates the expression of neoplastic OPN and the multifaceted roles of OPN in head and neck cancer (HNC) are unclear. In this study, we tried to investigate the bridging role of OPN between tumor stroma and cancer cells.

Methods: Immunohistochemical staining and quantitative real-time PCR were used to detect OPN expression in HNC tissues, and the correlations between OPN expression and clinicopathologic features were then analyzed. We used a co-culture assay to study the modulatory role of IL-6 on OPN expression and immunoprecipitation analysis was used to determine the endogenous interaction between OPN and integrin αvβ3. Furthermore, a xenograft assay was carried out to confirm the tumor-promoting role and the potential therapeutic value of OPN in HNC.

Results: We found that OPN was significantly up-regulated in HNCs, and the elevated OPN was correlated with poor prognosis. Moreover, we identified IL-6 secreted by cancer-associated fibroblasts (CAFs) as the major upstream molecule that triggers the induction of neoplastic OPN. As such, during the interaction of fibroblasts and cancer cells, the increased neoplastic OPN induced by stromal IL-6 accelerated the growth, migration and invasion of cancer cells. More importantly, we also showed that soluble OPN could promote HNC progression via the integrin αvβ3-NF-kappa B pathway, and the combination of OPN and IL-6 had a better prognostic and diagnostic performance in HNC than either molecule alone.

Conclusion: Our study identified a novel modulatory role for OPN in HNC progression and further demonstrated that the combination of OPN and IL-6 might be a promising prognostic and diagnostic indicator as well as a potential cancer therapeutic target.

Osteopontin is a multi-faceted pro-tumorigenic driver for central nervous system lymphoma

Osteopontin (OPN) is the most upregulated gene in primary central nervous system lymphoma (PCNSL) compared to non-CNS diffuse large B cell lymphoma (DLBCL). We show here that OPN is a key mediator of intracerebral tumor growth, invasion, and dissemination in CNS lymphoma, and that these effects depend upon activation of NF-κB. We further show that activation of NF-κB by OPN occurs through a unique mechanism in which intracellular OPN (iOPN) causes transcriptional downregulation of the NF-κB inhibitors, A20/TNFAIP3 and ABIN1/TNIP1, and secretory OPN (sOPN) promotes receptor-mediated activation of NF-κB. We also identify NF-κB-mediated induction of matrix metalloproteinase-8 (MMP-8) as a specific feature of OPN-mediated tissue invasion. These results implicate OPN as a candidate for development of targeted therapy for patients with PCNSL.

NF‑κB inhibition is associated with OPN/MMP‑9 downregulation in cutaneous melanoma

The development of cutaneous melanoma is influenced by genetic factors, including BRAF mutations and environmental factors, such as ultraviolet exposure. Its progression has been also associated with the involvement of several tumour microenvironmental molecules. Among these, nuclear factor‑κB (NF‑κB) has been indicated as a key player of osteopontin (OPN) and matrix metalloproteinase‑9 (MMP‑9) activation. However, whether NF‑κB plays a role in the development and progression of melanoma in association with the OPN/MMP‑9 axis according to the BRAFV600E mutation status has not been investigated in detail to date. Thus, in the present study, in order to shed light on this matter, 148 patients with melanoma and 53 healthy donors were recruited for the analysis of OPN, MMP‑9 and NF‑κB. Significantly higher circulating levels of OPN and MMP‑9 were observed in the patients with melanoma when compared to the healthy donors. Similar data were obtained for NF‑κB p65 activity. The OPN levels did not differ significantly between melanomas with or without BRAFV600E mutation. However, as regards NF‑κB and MMP‑9, significant differences were observed between the melanomas with or without BRAFV600E mutation. To determine whether NF‑κB inhibition is associated with a decrease in the levels of OPN and MMP‑9, peripheral blood mononuclear cells from 29 patients with melanoma were treated with the NF‑κB inhibitor, dehydroxymethylepoxyquinomycin (DHMEQ), with or without OPN. As expected, the inhibition of NF‑κB induced a marked decrease in both the OPN and MMP‑9 levels. Furthermore, the decrease in MMP‑9 levels was higher among melanomas harbouring the BRAFV600E mutation. Overall, our data suggest that the activation of MMP‑9 is associated with the BRAFV600E mutation status. Furthermore, such an activation is mediated by NF‑κB, suggesting its role as therapeutic target in patients with melanoma.

Signature of cytokines and angiogenic factors (CAFs) defines a clinically distinct subgroup of gastric cancer

BACKGROUND

Little is known about cytokine and angiogenic factors (CAFs) in gastric cancer (GC) in terms of tumor classification and prognostic value. Here, we aimed to correlate CAF signature with overall survival (OS) in GC.

METHODS

We measured pretreatment serum levels of 52 kinds of CAFs in 68 GC patients who were treated with fluoropyrimidine and platinum combination chemotherapy using multiplex bead immunoassays and enzyme-linked immunosorbent assay. We evaluated correlations between CAF levels and pathological features and OS.

RESULTS

Three distinct patient groups were identified: one with high levels of proangiogenic factors, another with high levels of proinflammatory factors, and the other with high levels of both factors. Eleven CAFs [interleukin (IL)-2 receptor-alpha, growth-regulated alpha protein, hepatocyte growth factor, macrophage colony-stimulating factor, stromal cell-derived factor, IL-6, IL-8, IL-10, interferon-gamma, vascular endothelial growth factor, and osteopontin] were independently correlated with poor OS. Clustering analysis of these 11 CAFs revealed distinct high and low 11-CAF signature groups. High 11-CAF signature was associated with shorter OS (10.1 vs. 17.9 months, p = 0.026) along with poor performance status, and the presence of signet ring cell components in multivariate analysis of OS (HR 1.76, p = 0.029). The patients' traditional clinicopathological characteristics were not significantly different between the high and low 11-CAF signature groups.

CONCLUSION

Serum CAF profiling differentiated GC patient groups. A high 11-CAF signature could identify GC patients with a poor prognosis when treated with standard chemotherapy who need urgent new treatment strategies.

Zerumbone Suppresses Osteopontin-Induced Cell Invasion Through Inhibiting the FAK/AKT/ROCK Pathway in Human Non-Small Cell Lung Cancer A549 Cells

Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer deaths in the United States and Korea. We have previously demonstrated that osteopontin (OPN) induces cell invasion through inactivating cofilin. Inactivation of cofilin is mediated by the FAK/AKT/Rho-associated kinase (ROCK) pathway in human nonsmall cell lung cancer (NSCLC) cells. Zerumbone (1) has been shown to exert anticancer activities. In this study, whether and how 1 affects OPN-induced cell invasion was determined in NSCLC A549 cells. Results from Boyden chamber assays suggested that OPN induced invasion of A549 cells and that 1 strongly suppressed this activity without affecting cell viability. Compound 1 effectively inhibited OPN-induced protein expression of ROCK1, the phosphorylation of LIM kinase 1 and 2 (LIMK1/2), and cofilin. In addition, immunofluorescence staining showed that OPN caused a significant increase in lamellipodia formation at the leading edge of cells. However, 1 dramatically decreased OPN-induced lamellipodia formation. Compound 1 impaired OPN-induced phosphorylation of FAK and AKT, as determined by Western blot analysis. Taken together, these results suggest that 1 causes considerable suppression of OPN-induced cell invasion through inhibiting the FAK/AKT/ROCK pathway in NSCLC A549 cells.

Osteopontin promotes a cancer stem cell-like phenotype in hepatocellular carcinoma cells via an integrin-NF-κB-HIF-1α pathway

There is increasing evidence to suggest that hepatocellular carcinomas (HCCs) are sustained by a distinct subpopulation of self-renewing cells known as cancer stem cells. However, the precise signals required for maintenance of stemness-like properties of these cells are yet to be elucidated. Here, we demonstrated that the level of oncoprotein osteopontin (OPN) in tumor cells of the edge of bulk tumors was significantly correlated with the clinical prognosis of patients with HCC. OPN was highly expressed in side population fractions of HCC cell lines, as well as in dormant cells, spheroids and chemo-resistant cancer cells, all of which are considered as having stemness-like cellular features. Depletion of OPN in HCC cell lines resulted in a reduction in the proportion of side population fractions, formation of hepato-spheroids, expression of stem-cell-associated genes and decreased tumorigenecity in immunodeficient mice. Mechanistically, OPN was demonstrated to bind to integrin α_vβ₃ and activate the transcription factor NF-κB, which resulted in upregulation of HIF-1α transcription and its downstream gene, BMI1, to mediate maintenance of the stemness-like phenotype. Suppression of the α_vβ₃–NF-κB–HIF-1α pathway decreased OPN-mediated self-renewal capabilities. Levels of OPN protein expression were significantly correlated with HIF-1α protein levels in HCC tumor tissue samples. OPN might promote a cancer stem cell-like phenotype via the α_vβ₃–NF-κB–HIF-1α pathway. Our findings offer strong support for OPN requirement in maintaining stem-like properties in HCC cells.

Osteopontin induces vascular endothelial growth factor expression in articular cartilage through PI3K/AKT and ERK1/2 signaling

The expression of osteopontin (OPN) and vascular endothelial growth factor (VEGF) are associated with the severity of cartilage destruction in osteoarthritis. However, the biological connection between OPN and VEGF in osteoarthritis remains to be elucidated. The present study was performed to investigate the effect of OPN on VEGF expression in articular cartilage. Rat articular chondrocytes were isolated and cultured in monolayer conditions, and they were treated with OPN for different time periods (0, 2, 8, 12 or 24 h) and dosages (0, 0.1, 0.25 or 0.5 µM). VEGF expression was assessed by reverse transcription‑quantitative polymerase chain reaction and western blotting. The activation of the phosphoinositide 3‑kinase (PI3K)/AKT and extracellular signal‑regulated kinase (ERK)1/2 pathway was analyzed by detecting the expression of pPI3K, pAKT and pERK1/2. To inhibit the PI3K/AKT and ERK1/2 pathway, LY294002 and PD98059 were used, respectively or in combination. It was identified that OPN increased the expression of VEGF in a dose‑ and time‑dependent manner. The PI3K/AKT and ERK1/2 pathways were activated following OPN stimulation and the effect was concomitant with the upregulation of VEGF. Finally, the regulation of VEGF was inhibited by LY294002 and PD98059, and their combination exhibited a synergistic effect. In conclusion, these findings suggest that OPN may directly upregulate VEGF expression through the PI3K/AKT and ERK1/2 pathway. Further studies are required to reveal the mechanism of action of OPN on cartilage angiogenesis and cartilage destruction.

Rho-associated kinase signaling is required for osteopontin-induced cell invasion through inactivating cofilin in human non-small cell lung cancer cell lines

Osteopontin (OPN) is involved in tumor progression such as invasion and metastasis, and poor prognosis of lung cancer. However, how OPN affects the invasive behavior of lung cancer is not well defined. Here, we examined the underlying molecular mechanism of OPN-induced invasion in human non-small cell lung cancer (NSCLC) cell lines including A549 cells. OPN markedly increased the phosphorylation of LIM kinase 1 and 2 (LIMK1/2), and cofilin without affecting their total forms. The expression of Rho-associated kinase 1 (ROCK1), but not p21-activated kinase 1 and 2 (PAK1/2), was increased by OPN treatment as an upstream effector of LIMK/cofilin. The phosphorylation of cofilin by OPN was suppressed when cells were pretreated with ROCK inhibitor Y27632 by Western blot. Moreover, it verified that OPN inactivated cofilin through ROCK signaling in other NSCLC cell lines. OPN induced the phosphorylation of FAK and AKT. FAK inhibitor FAKi-14 and PI3K inhibitor wortmannin decreased the expressions of ROCK1, and phosphorylation of LIMK1/2 and cofilin. OPN caused a significant increase in the lamellipodia formation and cell invasion, and these are suppressed by FAK inhibitor FAKi-14, PI3K inhibitor wortmannin and ROCK inhibitor Y27632. Taken together, these results suggest that OPN triggers ROCK signaling mediated by FAK/PI3K/AKT pathway, which in turn induces the lamellipodia formation to allow the invasion of lung cancer cells through inactivating cofilin.

Mechanisms involved in breast cancer liver metastasis

Liver metastasis is a frequent occurrence in patients with breast cancer; however, the available treatments are limited and ineffective. While liver-specific homing of breast cancer cells is an important feature of metastasis, the formation of liver metastases is not random. Indeed, breast cancer cell factors contribute to the liver microenvironment. Major breakthroughs have been achieved recently in understanding breast cancer liver metastasis (BCLM). The process of liver metastasis consists of multiple steps and involves various factors from breast cancer cells and the liver microenvironment. A further understanding of the roles of breast cancer cells and the liver microenvironment is crucial to guide future work in clinical treatments. In this review we discuss the contribution of breast cancer cells and the liver microenvironment to liver metastasis, with the aim to improve therapeutic efficacy for patients with BCLM.

DJ-1 knockdown inhibits growth and xenograft‑induced tumor generation of human hepatocellular carcinoma cells

The aim of this study was to identify potential downstream effectors of the oncogene DJ-1 in hepatocellular carcinoma (HCC) cell lines, and examine its role in the Akt signaling pathway and HCC oncogenesis. Expression of the DJ-1 protein was assessed by immunoblotting in several human HCC cell lines. Knockdown of DJ-1 was achieved by transfecting DJ-1-specific short hairpin RNAs into the HepG2 HCC cell line. The effect of DJ-1 downregulation on phosphatase and tensin homolog (PTEN) and phosphorylated Akt was evaluated. In addition, cell cycle, proliferation, adhesion and invasion were analyzed in the DJ-1 knockdown of HepG2 cells. The growth of HepG2‑induced tumor was evaluated in a nude mouse model after DJ-1 silencing. Stable DJ-1 knockdown was achieved in HepG2 cells using a shRNA eukaryotic expression vector. Downregulation of DJ-1 increased PTEN expression but decreased phosphorylation of Akt in HepG2 cells. In addition, DJ-1 knockdown resulted in the decreased proliferation, adhesion and invasion of HepG2 cells in vitro, and inhibited the growth of HepG2-induced tumor in vivo. DJ-1 knockdown altered the malignant behavior of HepG2 cells, potentially through the Akt signaling pathway, suggesting a crucial role for DJ-1 in the oncogenesis of HCC.

Osteopontin, a possible modulator of cancer stem cells and their malignant niche

The reciprocal interaction between cancer stem cells and their niche is important for oncogenesis and tumor progression, but the factors involved in this interrelationship remain largely unknown. We have recently demonstrated that osteopontin plays a crucial role in the crosstalk between CD44⁺ colorectal cancer stem cells and tumor-associated macrophages.

Osteopontin promotes the progression of gastric cancer through the NF-κB pathway regulated by the MAPK and PI3K

To elucidate the biological functions of osteopontin (OPN) in gastric tumors and to better understand the molecular events of OPN responsible for the malignancy, the present studies were performed. Growth curve, apoptosis assay, invasion assay and migration assay revealed that OPN status significantly affected proliferation, apoptosis, invasion and migration in gastric cancer cell lines. In mouse xenograft models of human gastric cancer, OPN silencing significantly inhibited tumor growth and the incidence of metastasis compared with non-silenced control. Mechanistic investigations revealed that OPN silencing inhibited the mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K) and phosphoinositide 3-kinase (NF-κB) pathways, and OPN-mediated NF-κB activity was reduced in the presence of MAPK or PI3K inhibitor. Our findings also indicated that OPN through the NF-κB pathway promotes the expression of matrix metalloproteinase 2 (MMP-2), MMP-9 and urokinase-type plasminogen activator (uPA), the activation of MMP-2 and MMP-9, and the inhibition of caspase-3. Taken together, our results reveal that OPN promotes the progression of gastric cancer through the NF-κB pathway, which is regulated by the MAPK and PI3K pathways and leads to MMP-2, MMP-9 and uPA activation and caspase-3 inhibition. These findings identify OPN as a novel oncogene in gastric cancer and suggest that OPN is an attractive therapeutic target for this aggressive malignancy.

Curcumin induces cross-regulation between autophagy and apoptosis in uterine leiomyosarcoma cells

OBJECTIVE

Uterine leiomyosarcoma (LMS) has an unfavorable response to standard chemotherapy. A natural occurring compound, curcumin, has been shown to have inhibitory effects on cancers. We previously demonstrated that curcumin reduced uterine LMS cell proliferation by targeting the AKT-mTOR pathway and activating apoptosis. To further explore the anticancer effect of curcumin, we investigated the efficacy of curcumin on autophagy in LMS cells.

METHODS

Cell proliferation in human uterine LMS cell lines, SKN and SK-UT-1, was assessed after exposure to rapamycin or curcumin. Autophagy was detected by Western blotting for light chain 3 and sequestosome 1 (SQSTM1/p62) expression. Apoptosis was confirmed by Western blotting for cleaved poly (ADP-ribose) polymerase (PARP).

RESULTS

Both rapamycin and curcumin potently inhibited SKN and SK-UT-1 cell proliferation in a dose-dependent manner. Curcumin induced autophagy and apoptosis in SKN and SK-UT-1 cells, whereas rapamycin, a specific mTOR inhibitor, did not. Curcumin increased extracellular signal-regulated kinase 1/2 activity in both SKN and SK-UT-1 cells, whereas PD98059, an MEK1 inhibitor, inhibited both the extracellular signal-regulated kinase 1/2 pathway and curcumin-induced autophagy.

CONCLUSIONS

These experimental findings suggest that curcumin is a potent inhibitor of cell proliferation in uterine LMS and provide new insights about ongoing signaling events leading to the possible development of a new therapeutic agent.

Urokinase-type plasminogen activator expression and Rac1/WAVE-2/Arp2/3 pathway are blocked by pterostilbene to suppress cell migration and invasion in MDA-MB-231 cells

Breast cancer is the most common malignancy among females, and cancer invasion and metastasis are the leading causes of cancer death in breast cancer patients. Pterostilbene, a naturally occurring dimethylether analogue of resveratrol, has been demonstrated to possess anti-cancer effects. However, inhibitory effects of pterostilbene on cell migration and invasion and its underlying mechanisms are not fully understood. In this study, we investigated the anti-invasive mechanisms of pterostilbene in human breast cancer cell line MDA-MB-231 cells. Pterostilbene effectively inhibited serum-induced migration and invasion without affecting the viability of breast cancer cells. The mRNA expression and activity of urokinase-type plasminogen activator (uPA) were markedly reduced by pterostilbene treatment. Moreover, pterostilbene attenuated nuclear factor κB (NF-κB) transcriptional activity and DNA binding of NF-κB on uPA promoter. In addition, pterostilbene significantly impaired the activity of Rac1 and the expression of WASP-family verprolin-homologous protein-2 (WAVE-2) and actin-related protein 2/3 (Arp2/3). Overall, these results suggest that pterostilbene caused considerable suppression of cell migration and invasion through blocking NF-κB-mediated uPA expression and Rac1/WAVE/Arp2/3 pathway.

Nonclassical activation of Hedgehog signaling enhances multidrug resistance and makes cancer cells refractory to Smoothened-targeting Hedgehog inhibition

The Hedgehog (Hh) pathway is critical in normal development. However, it has been reported to be up-regulated in numerous cancers and implicated in tumorigenicity and metastasis. Classical activation of Hh signaling initiated by Hh ligands results in activation of Smoothened (SMOH) and culminates in the activation of the GLI transcription factors. Classical Hh signaling is autocrine or paracrine (involving interaction between tumor cells and their stroma/microenvironment). The tumor milieu is rich in inflammatory cytokines that can modulate tumor cell behavior. Here, we show for the first time that the Hh pathway can be nonclassically up-regulated by the inflammatory cytokine, osteopontin (OPN). OPN-initiated Akt-GSK3β signaling mediates the subcellular distribution and activation of GLI1 resulting in the modulation of epithelial mesenchymal plasticity and drug resistance. Interestingly, the SMOH inhibitor cyclopamine was unable to uncouple the effects of OPN on Hh signaling, indicating that OPN nonclassically activates GLI-mediated transcription. Given the fact that OPN is itself transcriptionally activated upon Hh signaling, our current findings highlight the possibility of a feedforward vicious cycle such that the Hh pathway might be turned on nonclassically by stimuli from the tumor milieu. Thus, drugs that target the classical Hh ligand-mediated activation of Hh signaling may be compromised in their ability to interfere with the functioning of the pathway.

Osteopontin expression in papillary thyroid carcinoma and its relationship with the BRAF mutation and tumor characteristics

Purpose

We evaluated the relationship between the degree of osteopontin (OPN) expression in papillary thyroid carcinoma (PTC) specimens and the presence of the BRAF mutation and clinicopathologic variables.

Methods

Fifty-six snap-frozen thyroid tumor samples, including those of 49 PTCs, four follicular adenomas, two follicular carcinomas, and one Hürthle cell adenoma, were studied. We performed reverse transcription-polymerase chain reaction (RT-PCR) to assess the OPN expression levels. We also tested the BRAF codon 599 mutations using RT-PCR with the direct sequencing method. All of the tumors were microscopically reexamined by a pathologist with a special interest in thyroid neoplasia.

Results

OPN mRNA was significantly overexpressed in the PTC samples compared with other thyroid tumors (P = 0.011). In PTCs, the OPN expression level was higher in the BRAF mutation group than in the wild-type group (P = 0.041). Among the clinicopathologic variables, nonfollicular variant histologic subtypes (P = 0.002) and the presence of lymph node metastases (P = 0.042) were correlated with elevated level of OPN expression.

Conclusion

OPN might play a crucial role in tumorigenesis and the progression of PTC.

Interleukin enhancer-binding factor 3 promotes breast tumor progression by regulating sustained urokinase-type plasminogen activator expression

Sustained urokinase-type plasminogen activator (uPA) expression is detected in aggressive breast tumors. Although uPA can be transiently upregulated by diverse extracellular stimuli, sustained, but not transiently upregulated uPA expression contributes to breast cancer invasion/metastasis. Unfortunately, how sustained uPA expression is achieved in invasive/metastatic breast cancer cells is unknown. Here, we show that sustained and transiently upregulated uPA expression are regulated by distinct mechanisms. Using a collection of transcription factor-targeted small-interfering RNAs, we discovered that interleukin enhancer-binding factor 3 (ILF3) is required for sustained uPA expression. Two discrete mechanisms mediate ILF3 action. The first is that ILF3 activates uPA transcription by binding to the CTGTT sequence in the nucleotides -1004∼-1000 of the uPA promoter; the second is that ILF3 inhibits the processing of uPA mRNA-targeting primary microRNAs (pri-miRNAs). Knockdown of ILF3 led to significant reduction in in vitro cell growth/migration/invasion and in vivo breast tumor development. Importantly, immunohistochemistry (IHC) showed that nuclear ILF3, but not cytoplasmic ILF3 staining correlates with elevated uPA level and higher grades of human breast tumor specimens. Nuclear localization of ILF3 highlights the role of ILF3 in sustained uPA expression as a transcription activator and pri-miRNA processing blocker. In conclusion, this study shows that ILF3 promotes breast tumorigenicity by regulating sustained uPA expression.

Silencing of skeletal metastasis-associated genes impairs migration of breast cancer cells and reduces osteolytic bone lesions

Bone sialoprotein (BSP) and osteopontin (OPN) are important factors in the metastasis of breast cancer, which were examined as targets for antineoplastic therapy by siRNA. In addition, the effect of gene silencing on their transcription factor Runx2 and their interaction partners integrin β(3) and matrix metalloproteinase 2 was studied. The effect of siRNAs directed against these genes was assessed by monitoring expression levels followed by functional assays in cell culture as well as skeletal metastases caused by human MDA-MB-231(luc) breast cancer cells in nude rats. Upon silencing of the targets, cell migration was profoundly impaired (p < 0.001 for BSP-siRNA), but the impact on proliferation was low. Systemic administration by osmotic mini-pumps of BSP-siRNA but not OPN-siRNA decreased osteolytic lesions (p = 0.067). Extraosseous tumour growth was not affected. As an alternative approach, non-viral, polymeric based formulations of siRNAs in nanoparticles (NP) were developed. Locoregional administration of the two siRNAs targeting OPN and BSP encapsulated in these biodegradable NP reduced skeletal lesions even more efficiently (p = 0.03). Compared to systemic administration, this treatment caused not only a more pronounced anti-osteolytic effect at a 25-fold lower total siRNA dose, but also had a slight reducing effect on tumour incidence (p = 0.095). In conclusion, the siRNA treatment had a small effect on cellular proliferation but a significant efficacy against migration of and osteolysis induced by MDA-MB-231 cells. Our data underline that siRNA mediated knockdown is a powerful tool for identifying targets for pharmacological intervention. In addition, encapsulation of siRNA into biodegradable NP is a strategy, which promises well for using siRNA.

S-Allylcysteine inhibits tumour progression and the epithelial–mesenchymal transition in a mouse xenograft model of oral cancer

Oral cancer is prevalent worldwide. Studies have indicated that an increase in the osteopontin (OPN) plasma level is correlated with the progression of oral cancer. Our previous report showed that the aqueous garlic extract S-allylcysteine (SAC) inhibited the epithelial–mesenchymal transition (EMT) of human oral cancer CAL-27 cells in vitro. Therefore, the present study investigated whether SAC consumption would help prevent tumour growth and progression, including the EMT, in a mouse xenograft model of oral cancer. The results demonstrated that SAC dose-dependently inhibited the growth of oral cancer in tumour-bearing mice. The histopathological and immunohistochemical staining results indicated that SAC was able to effectively suppress the tumour growth and progression of oral cancer in vivo. The chemopreventive effect of SAC was associated with the suppression of carcinogenesis factors such as N-methylpurine DNA glycosylase and OPN. SAC significantly suppressed the phosphorylation of Akt, mammalian target of rapamycin, inhibitor of κBα and extracellular signal-regulated kinase 1/2 in tumour tissues. The results demonstrated that the SAC-mediated suppression of cyclin D1 protein was associated with an augmented expression of the cell-cycle inhibitor p16Ink4. Furthermore, SAC inhibited the expression of cyclo-oxygenase-2, vimentin and NF-κB p65 (RelA). These results show that SAC has potential as an agent against tumour growth and the progression of oral cancer in a mouse xenograft model.

Loss of tumor suppressor Merlin in advanced breast cancer is due to post-translational regulation

Unlike malignancies of the nervous system, there have been no mutations identified in Merlin in breast cancer. As such, the role of the tumor suppressor, Merlin, has not been investigated in breast cancer. We assessed Merlin expression in breast cancer tissues by immunohistochemistry and by real-time PCR. The expression of Merlin protein (assessed immunohistochemically) was significantly decreased in breast cancer tissues (although the transcript levels were comparable) simultaneous with increased expression of the tumor-promoting protein, osteopontin (OPN). We further demonstrate that the loss of Merlin in breast cancer is brought about, in part, due to OPN-initiated Akt-mediated phosphorylation of Merlin leading to its proteasomal degradation. Restoring expression of Merlin resulted in reduced malignant attributes of breast cancer, characterized by reduced invasion, migration, motility, and impeded tumor (xenograft) growth in immunocompromised mice. The possibility of developing a model using the relationship between OPN and Merlin was tested with a logistic regression model applied to immunohistochemistry data. This identified consistent loss of immunohistochemical expression of Merlin in breast tumor tissues. Thus, we demonstrate for the first time a role for Merlin in impeding breast malignancy, identify a novel mechanism for the loss of Merlin protein in breast cancer, and have developed a discriminatory model using Merlin and OPN expression in breast tumor tissues.

Osteopontin--an important downstream effector of S100A4-mediated invasion and metastasis

Substantial evidence has linked the small calcium-binding protein S100A4 to metastatic progression. S100A4-mediated effects include stimulation of angiogenesis, regulation of cell death and increased cell motility and invasion, but the exact molecular mechanisms by which the protein exerts these effects are incompletely elucidated. In the present study, we demonstrate that S100A4 induces NF-κB-dependent expression and secretion of osteopontin (OPN) in a selection of osteosarcoma cell lines. OPN is, as S100A4, known to result in a variety of cellular effects potentially leading to increased angiogenesis and metastasis, and several of the activated signaling pathways are common for the two proteins. In our study, extracellular S100A4 was found to upregulate enzymes of the plasminogen activator system and matrix metalloproteinase (MMP) family, especially urokinase plasminogen activator and MMP-13. Furthermore, increased motility and invasion was observed in vitro as a result of S100A4 treatment. OPN expression was inhibited by the use of siRNA molecules, and a partial blocking of S100A4-induced effects on protease expression and invasive capacity was detected. In conclusion, our results suggest regulation of OPN as a downstream molecular mechanism of S100A4 signaling. This novel finding adds more information to how S100A4 mediates tumor development and metastatic progression. The observation of a link between S100A4 and OPN, and also identification of common downstream effect molecules, highlights them, their receptors or downstream proteins, as targets for therapeutic approaches.

Abnormal expression of the ERG transcription factor in prostate cancer cells activates osteopontin

Osteopontin (OPN) is an extracellular matrix glycophosphoprotein that plays a key role in the metastasis of a wide variety of cancers. The high level of OPN expression in prostate cells is associated with malignancy and reduced survival of the patient. Recent studies on prostate cancer (PCa) tissue have revealed recurrent genomic rearrangements involving the fusion of the 5' untranslated region of a prostate-specific androgen-responsive gene with a gene coding for transcription factors from the ETS family. The most frequently identified fusion gene is TMPRSS2:ERG, which causes ERG protein overexpression in PCa cells. ERG is a transcription factor linked to skeletogenesis. This study was designed to test whether ERG and the product of the TMPRSS2:ERG fusion gene modulate OPN gene expression in PCa cells. To characterize ERG and TMPRSS2:ERG transcriptional activity of OPN, we focused on ETS binding sites (EBS) localized in conserved regions of the promoter. Using in vitro and in vivo molecular assays, we showed that ERG increases OPN expression and binds to an EBS (nt -115 to -118) in the OPN promoter. Moreover, stable transfection of prostate tumor cell lines by TMPRSS2:ERG upregulates endogenous OPN expression. Finally, in human prostate tumor samples, detection of the TMPRSS2:ERG fusion gene was significantly associated with OPN overexpression. Taken together, these data suggest that OPN is an ERG-target gene in PCa where the abnormal expression of the transcription factor ERG, due to the TMPRSS2:ERG fusion, disturbs the expression of genes that play an important role in PCa cells and associated metastases.

Betulinic acid inhibits high glucose-induced vascular smooth muscle cells proliferation and migration

The proliferation of vascular smooth muscle cells may perform a crucial role in the pathogenesis of diabetic vascular disease. The principal objective of this study was to determine the effects of betulinic acid (BA) on human aortic smooth muscle cell (HASMC) proliferation induced by high glucose (HG). In this study, [(3) H]-thymidine incorporation under 25 mM HG was accelerated significantly as compared with 5.5 mM glucose, and this increase was inhibited significantly by BA treatment. We utilized Western blotting analysis to evaluate the effects of BA on cell-cycle regulatory proteins. HG induced the expression of cyclins/CDKs and reduced the expression of p21(waf1/cip1) /p27(kip1). However, BA also attenuated the expression of HG-induced cell-cycle regulatory proteins. The results of gelatin zymography demonstrated that the HG-treated HASMC secreted gelatinases, probably including MMP-2/-9, which may be involved in the invasion and migration of HASMC. Additionally, BA suppressed the protein and mRNA expression levels of MMP-2/-9 in a dose-dependent manner. BA inhibited the production of HG-induced hydrogen peroxide (H(2)O(2)) and the formation of DCF-sensitive intracellular reactive oxygen species (ROS). Further, BA suppressed the nuclear translocation and phosphorylation of IκB-α of NF-κB under HG conditions. Our results showed that BA exerts multiple effects on HG-induced HASMC proliferation and migration, including the inhibition of both MMP-2 and MMP-9 transcription, protein activity, and the downregulation of ROS/NF-κB signaling, thereby suggesting that BA may be a possible therapeutic approach to the inhibition of diabetic vascular disease.

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.

Osteopontin promotes CCL5-mesenchymal stromal cell-mediated breast cancer metastasis

The interaction between cancer and its local microenvironment can determine properties of growth and metastasis. A critical component of the tumor microenvironment in this context is the cancer-associated fibroblast (CAF), which can promote tumor growth, angiogenesis and metastasis. It has been hypothesized that CAF may be derived from mesenchymal stromal cells (MSC), derived from local or distant sources. However, the signaling mechanisms by which tumors and MSCs interact to promote CAF-dependent cancer growth are largely unknown. In this study with in vitro and in vivo models using MDA-MB231 human breast cancer cells, we demonstrate that tumor-derived osteopontin (OPN) induces MSC production of CCL5; the mechanism involves OPN binding to integrin cell surface receptors and activator protein-1 c-jun homodimer transactivation. In a murine xenograft model, concomitant inoculation of MSC with MDA-MB231 cells induces: (i) significantly increased growth and metastasis of MB231 cells and (ii) increased MSC migration to metastatic sites in lung and liver; this mechanism is both OPN and CCL5 dependent. MSCs retrieved from sites of metastases exhibit OPN-dependent expression of the CAF markers, α-smooth muscle actin, tenascin-c, CXCL12 (or stromal cell-derived factor 1) and fibroblast-specific protein-1 and the matrix metalloproteinases (MMP)-2 and MMP-9. Based upon these results, we propose that tumor-derived OPN promotes tumor progression via the transformation of MSC into CAF.

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.

Regulation of Erk1/2 activation by osteopontin in PC3 human prostate cancer cells

BACKGROUND

Osteopontin (OPN) has been shown to play many roles in the progression of cancer. We have recently demonstrated the activation of Akt by OPN. Integrin-linked kinase and PI3-kinase are integral proteins in OPN/AKT pathway in PC3 cells. To investigate the role of the extracellular receptors in OPN signaling, we have examined the spatio-temporal regulation of CD44 and integrin αvβ3 receptor in OPN-induced Akt activation in PC3 cells.

RESULTS

Here, our studies demonstrate that OPN can activate Akt either through the αVβ3 integrin or the CD44 cell surface receptor. Members of the Mitogen Activated Protein Kinase (MAPK) family have been shown to be up-regulated in a variety of human cancers and have been implicated in the metastatic behavior. Our studies have demonstrated an increase in the phosphorylation of c-Raf at Ser259 and Ser338 in PC3 cells over-expressing OPN. This increase matches up with the Erk1/2 phosphorylation at Thr202/204 and activation. However, the inhibition of Akt activity augments the phosphorylation state of ERK1/2 to two to three fold with a concomitant reduction in the phosphorylation state of c-Raf at Ser259.

CONCLUSIONS

Regulation c-Raf phosphorylation at Ser259 has a role in the anti-apoptotic pathways mediated by Akt or Raf/MEK/ERK proteins. OPN may have dual effects in the activation of Erk1/2. We propose this based on the observations that while OPN activates c-Raf and Erk1/2; it also acts to inhibit c-Raf and Erk1/2 activation through Akt pathway. Our observations suggest that the activation of c-Raf-ERK cascade may promote cell cycle arrest in prostate cancer cells and OPN signaling has a role in the anti-apoptotic mechanism.

Osteopontin, a single marker for predicting the prognosis of patients with tumor-node-metastasis stage I hepatocellular carcinoma after surgical resection

BACKGROUND AND AIM

Osteopontin (OPN) has been linked to clinical outcomes in several solid tumors. However, it has not been fully evaluated whether OPN could be used as a single marker for the prognosis of patients with hepatocellular carcinoma (HCC), particularly in patients of the tumor-node-metastasis (TNM) stage I.

METHODS

A total of 151 patients with HCC who underwent surgical resection were enrolled, including 112 patients of the TNM stage I. OPN expression was evaluated using immunohistochemistry in the tissue microarrays derived from these patients. Immunoreactivity was classified according to the percentage and intensity of staining: negative (-), weak (+) and strong (++). The impact of OPN expression on survival of patients was analyzed.

RESULTS

In total, 65.6% (99 of 151) of HCC tissues expressed OPN. Overall survival in patients of OPN (-) group was significantly higher than those of OPN (+) or OPN (++) group (P = 0.049 and P = 0.001). Interestingly, in patients of the TNM stage I, OPN expression was correlated with the early recurrence after surgical resection (P = 0.001). Multivariate analysis showed that OPN expression was an independent prognostic factor for overall survival and disease-free survival in patients with the TNM stage I HCC (hazard ratio, 2.272, P = 0.014 and 1.982, P = 0.037).

CONCLUSIONS

These results suggest that OPN is commonly expressed in HCC and is a useful marker for predicting the prognosis of patients with the TNM stage I HCC, contributing to determining which individual patient needs adjuvant therapy to prevent the early recurrence after surgical resection.

Osteopontin promotes gastric cancer metastasis by augmenting cell survival and invasion through Akt-mediated HIF-1alpha up-regulation and MMP9 activation

Osteopontin (OPN) is a secreted, integrin-binding matrix phosphorylated glycoprotein. OPN has been shown to facilitate the progression and metastasis of malignancies and has prognostic value in several types of cancer, including gastric cancer. However, the functional mechanism of OPN mediated metastatic growth in gastric cancer remains unclear. Here, using multiple in vitro and in vivo models, we report that OPN strongly promoted the progression and metastasis of gastric cancer. Immunohistochemical staining revealed that OPN, matrix metalloproteinase (MMP)9 and hypoxia-inducible factor (HIF)-1alpha have statistically significant different expression patterns between well- and poorly differentiated tissue samples (P < 0.05). Correlations existed between OPN and MMP9, and between OPN and HIF-1 (r(1) = 0.872, p(1) < 0.01 and r(2) = 0.878, p(2) < 0.01). Furthermore, OPN dramatically increased colony formation and invasion of gastric cancer cells in vitro and promoted tumour growth and metastasis in vivo. In addition, OPN potently protected gastric cancer cells from serum depletion-induced apoptosis. Further study shows that OPN activated phosphoinositide 3-kinase/Akt survival pathway and up-regulated HIF-1alpha via binding to v3 integrins in gastric cancer cells. Moreover, we found that OPN could activate MMP9 and upregulate MMP2. Taken together, our results suggest that the survival-promoting function is crucial for OPN to promote the development of gastric cancer, and HIF-1 and MMP9 may play key roles during this process. Thus, targeting OPN and its related signalling network may develop an effective therapeutic approach for the management of gastric cancer.