Fibronectin supports TNF-alpha-induced osteopontin expression through beta1 integrin and ERK in HN-22 cells

RAB6A functions as a critical modulator of the stem-like subsets in cholangiocarcinoma

RAB6A is a member of RAB GTPase family and plays an important role in the targeted transport of neurotrophic receptors and inflammatory cytokines. RAB6A-mediated secretory pathway is involved in many physiological and pathological processes. Defects in RAB6A-mediated secretory pathway may lead to the development of many diseases, including cancer. However, its role in cholangiocarcinoma (CCA) has not yet been revealed. We explored the regulatory role of RAB6A in the stem-like subsets of CCA. We showed that RAB6A knockdown (KD) impedes cancer stem cells (CSCs) properties and epithelial-mesenchymal transition in vitro and that suppression of RAB6A inhibits tumor growth in vivo. We screened target cargos of RAB6A in CCA cells and identified a extracellular matrix component as the target cargo. RAB6A binds directly to OPN, and RAB6A KD suppressed OPN secretion and inhibited the interaction between OPN and αV integrin receptor. Moreover, RAB6A KD inhibited the AKT signaling pathway, which is a downstream effector of the integrin receptor signaling. In addition, shRNA targeting OPN blocked endogenous expression of OPN and consequently weakened CSCs properties in RAB6A-formed spheres. Similarly, inhibitor of AKT signaling, MK2206 also impedes oncogenic function of RAB6A in the stem-like subsets of CCA cells. In conclusion, our findings showed that RAB6A sustains CSCs phenotype maintenance by modulating the secretion of OPN and consequentially activating the downstream AKT signaling pathway. Targeting the RAB6A/OPN axis may be an effective strategy for CCA therapy.

Osteopontin Expression in Thyroid Cancer: Deciphering EMT-Related Molecular Mechanisms

Thyroid cancer is the most common tumor arising from the endocrine system and generally presents good prognosis. However, its aggressive subtypes are related to therapeutic resistance and early metastasis. Epithelial–mesenchymal transition (EMT) and its reverse process, the mesenchymal–epithelial transition (MET), are key events mediating cancer progression, including in thyroid cancer. The matricellular protein osteopontin (OPN) has been reported as a master regulator of EMT in many tumor types. Although high OPN expression has been described and associated with important aspects of thyroid cancer progression, there is no clear evidence regarding OPN as a regulator of EMT in thyroid cancer. Thus, taking together the known roles of OPN in the modulation of EMT in cancer and the information reporting the expression of OPN in thyroid tumor progression, this review aims at summarizing and discussing data related to EMT in thyroid cancer and its putative relation to the roles of OPN in the development of thyroid cancer. These data provide new insights into the molecular mechanisms by which OPN could potentially modulate EMT in thyroid tumors, generating evidence for future studies that may contribute to new therapeutic, prognostic and/or diagnostic tools.

Squalene synthase promotes the invasion of lung cancer cells via the osteopontin/ERK pathway

Cholesterol is the major component of lipid rafts. Squalene synthase (SQS) is a cholesterol biosynthase that functions in cholesterol biosynthesis, modulates the formation of lipids rafts and promotes lung cancer metastasis. In this study, we investigated the lipid raft-associated pathway of SQS in lung cancer. Gene expression microarray data revealed the upregulation of secreted phosphoprotein 1 (SPP1; also known as osteopontin, OPN) in CL1-0/SQS-overexpressing cells. Knockdown of OPN in SQS-overexpressing cells inhibits their migration and invasion, whereas an OPN treatment rescues the migration and invasion of SQS knockdown cells. High OPN expression is associated with lymph node status, advanced stage and poor prognosis in patients with lung cancer. Moreover, patients with high SQS expression and high OPN expression show poor survival compared with patients with low SQS expression and low OPN expression. SQS induces the phosphorylation of Src and ERK1/2 via OPN, resulting in increased expression of MMP1 and subsequent metastasis of lung cancer cells. Based on our findings, SQS expression increases the expression of OPN and phosphorylation of Src through cholesterol synthesis to modulate the formation of lipid rafts. SQS may represent a therapeutic strategy for lung cancer.

Mesalazine, an osteopontin inhibitor: The potential prophylactic and remedial roles in induced liver fibrosis in rats

Liver fibrosis is a major health issue leading to high morbidity and mortality. The potential anti-fibrotic activity and the effect of mesalazine on osteopontin (OPN), an extra cellular matrix (ECM) component were evaluated in TAA-induced liver fibrosis in rats. For this purpose, forty-two adult male Wistar rats were divided into six groups. All animals, except the normal control, were intraperitoneally injected with TAA (200 mg/kg) twice per week for 6 weeks. In the hepato-protective study, animals were administered mesalazine (50 and 100 mg/kg, orally) for 4 weeks before induction of liver fibrosis then concomitantly with TAA injection. In the hepato-therapeutic study, animals were administered mesalazine for 6 weeks after TAA discontinuation with the same doses. In both studies, mesalazine administration improved liver biomarkers through decreasing serum levels of AST, ALT and total bilirubin when compared to fibrotic group with significant increase in total protein and albumin levels. Mesalazine significantly decreased hepatic MDA level and counteracted the depletion of hepatic GSH content and SOD activity. Additionally, it limits the elevation of OPN and TGF-β1 concentrations and suppressed TNF-α as well as α-SMA levels in hepatic tissue homogenate. Histopathologically, mesalazine as a treatment showed a good restoration of the hepatic parenchymal cells with an obvious decreased intensity and retraction of fibrous proliferation, while as a prophylaxis it didn't achieve enough protection against the harmful effect of TAA, although it decreased the intensity of portal to portal fibrosis and pseudolobulation. Furthermore, mesalazine could suppress the expression of both α-SMA and caspase-3 in immunohistochemical sections. In conclusion, mesalazine could have a potential new indication as anti-fibrotic agent through limiting the oxidative damage and altering TNF-ɑ pathway as an anti-inflammatory drug with down-regulating TGF-β1, OPN, α-SMA and caspase-3 signaling pathways.

Osteopontin-integrin interaction as a novel molecular target for antibody-mediated immunotherapy in adult T-cell leukemia

Background

Adult T-cell leukemia (ATL) is a CD4⁺ T-cell neoplasm with a poor prognosis. A previous study has shown that there is a strong correlation between the secreted matricellular protein osteopontin (OPN) level and disease severity in ATL patients. Here, we investigated the role of OPN in ATL pathogenesis and the possible application of anti-OPN monoclonal antibody (mAb) for ATL immunotherapy in NOD/Shi-scid,IL-2Rg^null (NOG) mice.

Results

Subcutaneous inoculation of ATL cell lines into NOG mice increased the plasma level of OPN, which significantly correlated with metastasis of the inoculated cells and survival time. Administration of an SVVYGLR motif-recognizing anti-OPN mAb resulted in inhibition not only of tumor growth but also of tumor invasion and metastasis. The number of fibroblast activating protein-positive fibroblasts was also reduced by this mAb. We then co-inoculated mouse embryonic fibroblasts (MEFs) isolated from wild-type (WT) or OPN knockout mice together with ATL-derived TL-OmI cells into the NOG mice. The mice co-inoculated with WT MEFs displayed a significant decrease in survival relative to those injected with TL-OmI cells alone and the absence of OPN in MEFs markedly improved the survival rate of TL-OmI-inoculated mice. In addition, tumor volume and metastasis were also reduced in the absence of OPN.

Conclusion

We showed that the xenograft NOG mice model can be a useful system for assessment of the physiological role of OPN in ATL pathogenesis. Using this xenograft model, we found that fibroblast-derived OPN was involved in tumor growth and metastasis, and that this tumor growth and metastasis was significantly suppressed by administration of the anti-OPN mAbs. Our findings will lead to a novel mAb-mediated immunotherapeutic strategy targeting against the interaction of OPN with integrins on the tumor of ATL patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-015-0225-x) contains supplementary material, which is available to authorized users.

Osteopontin - a multi-modal marker and mediator in atherosclerotic vascular disease

Atherosclerosis is a chronic inflammatory process of the vessel wall with systemic correlates. It is now well established that patients' outcome is tightly linked to atherosclerotic plaque stability, potentially more so than to the mere plaque size. Osteopontin (OPN) is an integrin-binding ligand, N-linked glycoprotein, which was recognized as a significant participant in the atherosclerotic inflammatory milieu. Evidence from several genetic mouse models suggests that OPN is an enhancer of atherosclerosis. This may be mediated by its capacity to enhance inflammation in the atherosclerotic plaque. Interestingly, OPN may also possess potentially protective vascular effects, such as attenuation of vascular calcification. In humans circulating levels of OPN were found to be independently associated with the severity of coronary atherosclerosis. Moreover, several studies report that high plasma OPN levels were associated with increased risk for major adverse cardiac events. This review aims to critically assess current understanding of the role of OPN in the atherosclerotic process, from animal models to clinical practice. Specific focus is given to evaluating whether OPN could serve as a marker for monitoring coronary atherosclerosis severity, and in parallel, assess the evidence for its role as a mediator in the pathogenic pathways leading to atherosclerotic vascular disease.

Modification of osteopontin and MMP-9 levels in patients with psoriasis on anti-TNF-α therapy

Psoriasis is a chronic skin inflammatory disease in which a pleiotropic cytokine, tumor necrosis factor alpha (TNF-α), plays a central role, as demonstrated by the clinical success of anti-TNF-α therapy. Among the multiple effects of TNF-α on keratinocytes, the induction of matrix metalloproteinase-9 (MMP-9), a collagenase implicated in joint inflammation, might be one of the key mechanisms in psoriasis pathogenesis. Interestingly, MMP-9 expression can be enhanced also by osteopontin (OPN), a glycosylated protein whose levels are increased in skin and peripheral blood mononuclear cells (PBMC) of psoriasis patients. The aim of the current study is to investigate the relationship between OPN, MMP-9 and TNF-α in psoriasis. Our survey identified high levels of both OPN and MMP-9 in PBMC as well as skin of psoriatic patients with respect to healthy controls. Significant reduction of OPN and MMP-9 levels in PBMC, plasma and lesional skin of psoriasis patients was observed after 24 weeks of anti-TNF-α therapy. Moreover, OPN and MMP-9 were enhanced by TNF-α and down-regulated by anti-TNF-α treatment in healthy PBMC. These findings may suggest that OPN and MMP-9 may be regulated by TNF-α, indicating a possible role in the pathogenesis of psoriasis.