Osteoactivin (GPNMB) ectodomain protein promotes growth and invasive behavior of human lung cancer cells.
Female; Humans; Animals; Mice; Apoptosis; GPNMB; *Cell Movement; Neoplasm Invasiveness; Membrane Glycoproteins/*metabolism; Biomarkers; *Cell Proliferation; cell adhesion; Cell Adhesion; integrin; lung cancer; Lung Neoplasms/metabolism/*pathology; NSCLC; Protein Domains; Xenograft Model Antitumor Assays; Carcinoma; Cultured; Tumor Cells; Nude; Non-Small-Cell Lung/metabolism/*pathology; Tumor/*metabolism
The potential application of GPNMB/OA as a therapeutic target for lung cancer will require a greater understanding of the impact of GPNMB/OA ectodomain (ECD) protein shedding into tumor tissues. Thus, in this work we characterized GPNMB/OA expression and extent of shedding of its ECD protein while evaluating the impact on lung cancer progression using three non-small cell lung cancer (NSCLC) cell lines: A549, SK-MES-1 and calu-6. We observed a direct correlation (R2 = 0.89) between GPNMB/OA expression on NSCLC cells and the extent of GPNMB/OA ECD protein shedding. Meanwhile, siRNA-mediated knockdown of GPNMB/OA in cancer cells significantly reduced GPNMB/OA ECD protein shedding, migration, invasion and adhesion to extracellular matrix materials. Also, exogenous treatment of cancer cells (expressing low GPNMB/OA) with recombinant GPNMB/OA protein (rOA) significantly facilitated cell invasion and migration, but the effects of rOA was negated by inclusion of a selective RGD peptide. Further studies in athymic (nu/nu) mice-bearing calu-6 showed that intratumoral supplementation with rOA effectively facilitated in vivo tumor growth as characterized by a high number of proliferating cells (Ki67 staining) coupled with a low number of apoptotic cells. Taken together, our results accentuate the relevance of GPNMB/OA ECD protein shedding to progression of lung cancer. Thus, strategies that suppress GPNMB/OA expression on lung cancer cells as well as negate shedding of GPNMB/OA ECD protein are worthy of consideration in lung cancer therapeutics.
Oyewumi Moses O; Manickavasagam Dharani; Novak Kimberly; Wehrung Daniel; Paulic Nikola; Moussa Fouad M; Sondag Gregory R; Safadi Fayez F
Oncotarget
2016
2016-03
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.18632/oncotarget.7323" target="_blank" rel="noreferrer noopener">10.18632/oncotarget.7323</a>
Osteoactivin inhibition of osteoclastogenesis is mediated through CD44-ERK signaling.
*MAP Kinase Signaling System; *Signal Transduction; Animals; Cell Differentiation; Cells; Cultured; Eye Proteins/*metabolism; Hyaluronan Receptors/*metabolism; Inbred C57BL; Male; Membrane Glycoproteins/*metabolism; Mice; Osteoclasts/*cytology/metabolism; RANK Ligand/metabolism; Recombinant Proteins/metabolism
Osteoactivin is a heavily glycosylated protein shown to have a role in bone remodeling. Previous studies from our lab have shown that mutation in Osteoactivin enhances osteoclast differentiation but inhibits their function. To date, a classical receptor and a signaling pathway for Osteoactivin-mediated osteoclast inhibition has not yet been characterized. In this study, we examined the role of Osteoactivin treatment on osteoclastogenesis using bone marrow-derived osteoclast progenitor cells and identify a signaling pathway relating to Osteoactivin function. We reveal that recombinant Osteoactivin treatment inhibited osteoclast differentiation in a dose-dependent manner shown by qPCR, TRAP staining, activity and count. Using several approaches, we show that Osteoactivin binds CD44 in osteoclasts. Furthermore, recombinant Osteoactivin treatment inhibited ERK phosphorylation in a CD44-dependent manner. Finally, we examined the role of Osteoactivin on receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteolysis in vivo. Our data indicate that recombinant Osteoactivin inhibits RANKL-induced osteolysis in vivo and this effect is CD44-dependent. Overall, our data indicate that Osteoactivin is a negative regulator of osteoclastogenesis in vitro and in vivo and that this process is regulated through CD44 and ERK activation.
Sondag Gregory R; Mbimba Thomas S; Moussa Fouad M; Novak Kimberly; Yu Bing; Jaber Fatima A; Abdelmagid Samir M; Geldenhuys Werner J; Safadi Fayez F
Experimental & molecular medicine
2016
2016-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1038/emm.2016.78" target="_blank" rel="noreferrer noopener">10.1038/emm.2016.78</a>
Multiple binding sites for [125I]RTI-121 and other cocaine analogs in rat frontal cerebral cortex.
*Membrane Transport Proteins; *Nerve Tissue Proteins; *Symporters; Animals; Binding; Binding Sites; Carrier Proteins/*metabolism; Cocaine/*analogs & derivatives/pharmacokinetics; Competitive; Corpus Striatum/*metabolism; Dopamine Plasma Membrane Transport Proteins; Dopamine/metabolism; Frontal Lobe/*metabolism; Iodine Radioisotopes/*pharmacokinetics; Kinetics; Male; Membrane Glycoproteins/*metabolism; Norepinephrine Plasma Membrane Transport Proteins; Norepinephrine/metabolism; Rats; Regression Analysis; Serotonin Plasma Membrane Transport Proteins; Serotonin/metabolism; Sprague-Dawley
In an effort to identify novel binding sites for cocaine and its analogs, we carried out binding studies with the high-affinity and selective ligand [125I]RTI-121 in rat frontal cortical tissue. Very low densities of binding sites were found. Saturation analysis revealed that the binding was to both high- and low-affinity sites. Pharmacological competition studies were carried out with inhibitors of the dopamine, norepinephrine, and serotonin transporters. The various transporter inhibitors inhibited the binding of 15 pM [125I]RTI-121 in a biphasic fashion following a two-site binding model. The resultant data were complex and did not suggest a simple association with any single transporter. Correlational analysis supported the following hypothesis: [125I] RTI-121 binds to known transporters and not to novel sites; these include dopamine, norepinephrine, and serotonin transporters. Immunoprecipitation of transporters photoaffinity labeled with [125]RTI-82 and subsequent analysis of SDS-page gels revealed the presence of authentic dopamine transporters in these samples; displacement of the photoaffinity label occurred with a typical dopamine transporter pharmacology. These data are compatible with the binding properties of RTI-121 and the presence of several known transporters in the tissue studied.
Boja J W; Carroll F I; Vaughan R A; Kopajtic T; Kuhar M J
Synapse (New York, N.Y.)
1998
1998-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/(SICI)1098-2396(199809)30:1%3C9::AID-SYN2%3E3.0.CO;2-7" target="_blank" rel="noreferrer noopener">10.1002/(SICI)1098-2396(199809)30:1%3C9::AID-SYN2%3E3.0.CO;2-7</a>