Lung Tumor Cell Recruitment Assay

To investigate the molecular mechanisms governing tumor metastasis, various assays using the mouse as a model animal have been proposed. Here, we ...

Tokyo Women's Medical University

Serum amyloid A (SAA) 3 is a major component of the acute phase of inflammation. We previously reported that SAA3 served as an endogenous peptide ligand for TLR4 to facilitate lung metastasis. Because these experiments were performed with SAA3 recombinant proteins purified from Escherichia coli or mammalian cells, we could not rule out the possibility of LPS contamination. In this study, we used SAA3 synthetic peptides to eliminate the presence of LPS in SAA3. We found that the SAA3 synthetic peptide (aa 20-86) (20-86) stimulated cell migration and activated p38 in a manner dependent on TLR4, MD-2, and MyD88. SAA3 (20-86) also activated NF-κB and Rho small GTPase. Using surface plasmon resonance analysis, the binding constant KD values between SAA3 (20-86) or SAA3 (43-57) and TLR4/MD-2 protein highly purified by the baculovirus system were 2.2 and 30 μM, respectively. FLAG-tagged SAA3 tightly bound to protein A-tagged MD-2, but not to TLR4 in baculovirus coinfection experiments. Although SAA3 (20-86) caused a low, but appreciable level of endocytosis in TLR4, it induced the upregulation of both IL-6 and TNF-α, but not IFN-β1. An i.v. injection of SAA3 (43-57) induced the lung recruitment of CD11b(+)Gr-1(+) cells at an estimated serum concentration around its KD value toward TLR4/MD-2. Taken together, these results suggest that SAA3 directly binds MD-2 and activates the MyD88-dependent TLR4/MD-2 pathway.

Serum amyloid A3 binds MD-2 to activate p38 and NF-κB pathways in a MyD88-dependent manner.

The deregulation of Eph/ephrin protein expression has been shown to lead to tumor development and progression. Both mRNA and protein expression analyses using clinical samples have demonstrated that ephrin-A1 is over-expressed in various cancers and positively correlates with a poor prognosis for cancer patients. The prognosis of cancer patients depends on metastasis to distant organs. We previously demonstrated that ADAM12 metalloproteinase cleaved ephrin-A1 and ADAM12-cleaved ephrin-A1 enhanced vascular permeability by degrading VE-cadherin and the EphA2 receptor at the plasma membrane. An increase of soluble ephrin-A1 levels in the serum facilitated tumor cell recruitment to the lungs, which resulted in lung metastasis. We also found that ephrin-A1 was overexpressed in 3LL tumors, a highly metastatic tumor, in mice and TNFα, an authentic positive regulator of ephrin-A1, was not elevated in the tumors, whereas S100A8 was. Moreover, S100A8 induced ephrin-A1 expression mediated by the toll-like receptor 4 (TLR4). S100A8 is known to be an endogenous ligand for TLR4 and its expression was shown to be increased in the lungs at the premetastatic phase. Thus, S100A8 and ephrin-A1 contribute to lung metastasis. Therefore, elucidating the regulation mechanism of ephrin-A1 overexpression is of importance and may lead to the development of therapeutic drugs against tumor growth and metastasis. 

Ephrin-A1 expression induced by S100A8 is mediated by the toll-like receptor 4.

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is commonly used as a spice, food additive or dietary pigment. Accumulating evidence suggests that curcumin has several pharmacologic effects, including anti-inflammatory, anti-oxidant and anti-cancer activities. The molecular mechanisms underlying the targets of curcumin are diverse and involve combinations of multiple signaling pathways, including NF-κB and STAT3 signaling. Thus, curcumin is one of the most promising phytochemicals that target various cancers and inflammation-mediated diseases. Clinical trials have been ongoing or completed for various cancers, including breast, pancreatic and colorectal cancers, and multiple myeloma. In this review, the molecular mechanisms and the issue of bioavailability are mainly discussed. 

Curcumin targets in inflammation and cancer.

TLRs are very important players to regulate innate immune responses. TLR4 controls the host defense by sensing an exotic pathogen, such as lipopolysaccharides. At the same time, some endogenous proteins, including HMGB1 and S100A8, could also function to be a ligand to elicit inflammatory reactions. These facts make TLR4 signaling system very complicated. For instance, the application of TLR4 ligands in cancer therapies is desirable for enhancement of anti-tumor immunity in terms of its reparative nature, but undesirable for enhancement of metastatic growth of cancer cells. In this manuscript, in order to make a novel molecular design to disrupt an interaction between TLR4/MD-2 and endogenous ligands, we provide a potential binding style of the TLR4/MD-2 complex with HMGB1 by using their 3D structural data and docking simulations, and also discuss S100A8 binding to TLR4/MD-2. 

Drug Targeting Based on a New Concept-Targeting Against TLR4 as an Example.

Multiple myeloma (MM) is a relapsed and refractory disease, one that highlights the need for developing new molecular therapies for overcoming of drug resistance. Addition of panobinostat, a histone deacetylase (HDAC) inhibitor, to bortezomib and dexamethasone improved progression-free survival (PFS) in relapsed and refractory MM patients. Here, we demonstrate how calcineurin, when inhibited by immunosuppressive drugs like FK506, is involved in myeloma cell growth and targeted by panobinostat. mRNA expression of , a catalytic subunit of calcineurin, was high in advanced patients. Panobinostat degraded PPP3CA, a degradation that should have been induced by inhibition of the chaperone function of heat shock protein 90 (HSP90). Cotreatment with HDAC inhibitors and FK506 led to an enhanced antimyeloma effect with a greater PPP3CA reduction compared with HDAC inhibitors alone both in vitro and in vivo. In addition, this combination treatment efficiently blocked osteoclast formation, which results in osteolytic lesions. The poor response and short PFS duration observed in the bortezomib-containing therapies of patients with high  suggested its relevance to bortezomib resistance. Moreover, bortezomib and HDAC inhibitors synergistically suppressed MM cell viability through PPP3CA inhibition. Our findings underscore the usefulness of calcineurin-targeted therapy in MM patients, including patients who are resistant to bortezomib.

Article	Year
Serum amyloid A3 binds MD-2 to activate p38 and NF-κB pathways in a MyD88-dependent manner. Journal of immunology (Baltimore, Md. : 1950)\| PubMed ID: 23858030	2013
Ephrin-A1 expression induced by S100A8 is mediated by the toll-like receptor 4. Biochemical and biophysical research communications\| PubMed ID: 24103748	2013
Curcumin targets in inflammation and cancer. Endocrine, metabolic & immune disorders drug targets\| PubMed ID: 25772169	2015
Drug Targeting Based on a New Concept-Targeting Against TLR4 as an Example. Endocrine, metabolic & immune disorders drug targets\| PubMed ID: 26004773	2015
Histone deacetylase inhibitor panobinostat induces calcineurin degradation in multiple myeloma. JCI insight\| PubMed ID: 27699258	2016

Atsuko Deguchi

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