In this review most of the various known, suspected, or postulated functions of osteopontin, a secreted highly acidic phosphoprotein, are discussed in terms of what we currently know about the protein. These include 1) binding of OPN both to cells via a GRGDS cell adhesion sequence that recognizes the alpha v beta 3 integrin and to extracellular matrix components via poorly characterized motifs, 2) regulation of the formation and remodeling of mineralized tissue, 3) recruiting and stimulating macrophages and lymphocytes as part of a nonspecific response to microbial infections, 4) multiple interactions with Ca2+ that likely influence OPN protein conformation and may be important in Ca(2+)-mediated or Ca(2+)-dependent processes, 5) inhibiting the growth of calcium oxalate crystals by disruption of the growing crystal lattice, 6) effects on gene expression, Ca2+ regulation, and nitric oxide production, and 7) involvement in cell migration. OPN production is frequently augmented when cell signaling pathways are activated by any of a variety of stimuli, for example in cancer cells.

Osteopontin: a protein with diverse functions.

Angiosarcomas apparently derive from blood vessel endothelial cells; however, occasionally their histological features suggest mixed origin from blood and lymphatic endothelia. In the absence of specific positive markers for lymphatic endothelia the precise distinction between these components has not been possible. Here we provide evidence by light and electron microscopic immunohistochemistry that podoplanin, a ∼38-kd membrane glycoprotein of podocytes, is specifically expressed in the endothelium of lymphatic capillaries, but not in the blood vasculature. In normal skin and kidney, podoplanin colocalized with vascular endothelial growth factor receptor-3, the only other lymphatic marker presently available. Complementary immunostaining of blood vessels was obtained with established endothelial markers (CD31, CD34, factor VIII-related antigen, and Ulex europaeus I lectin) as well as podocalyxin, another podocytic protein that is also localized in endothelia of blood vessels. Podoplanin specifically immunolabeled endothelia of benign tumorous lesions of undisputed lymphatic origin (lymphangiomas, hygromas) and was detected there as a 38-kd protein by immunoblotting. As paradigms of malignant vascular tumors, poorly differentiated (G3) common angiosarcomas ( n = 8), epitheloid angiosarcomas ( n = 3), and intestinal Kaposi's sarcomas ( n = 5) were examined for their podoplanin content in relation to conventional endothelial markers. The relative number of tumor cells expressing podoplanin was estimated and, although the number of cases in this preliminary study was limited to 16, an apparent spectrum of podoplanin expression emerged that can be divided into a low-expression group in which 0–10% of tumor cells contained podoplanin, a moderate-expression group with 30–60% and a high-expression group with 70–100%. Ten of eleven angiosarcomas and all Kaposi's sarcomas showed mixed expression of both lymphatic and blood vascular endothelial phenotypes. By double labeling, most podoplanin-positive tumor cells coexpressed endothelial markers of blood vessels, whereas few tumor cells were positive for individual markers only. From these results we conclude that (1) podoplanin is a selective marker of lymphatic endothelium; (2) G3 angiosarcomas display a quantitative spectrum of podoplanin-expressing tumor cells; (3) in most angiosarcomas, a varying subset of tumor cells coexpresses podoplanin and endothelial markers of blood vessels; and (4) all endothelial cells of Kaposi's sarcomas expressed the lymphatic marker podoplanin.

/pdf/angiosarcomas-express-mixed-endothelial-phenotypes-of-blood-2ud0dk5k7w.pdf

Angiosarcomas Express Mixed Endothelial Phenotypes of Blood and Lymphatic Capillaries: Podoplanin as a Specific Marker for Lymphatic Endothelium

Within the vascular system, the mucin‐type transmembrane glycoprotein T1α/podoplanin is predominantly expressed by lymphatic endothelium, and recent studies have shown that it is regulated by the lymphatic‐specific homeobox gene Prox1 . In this study, we examined the role of T1α/podoplanin in vascular development and the effects of gene disruption in mice. T1α/podoplanin is first expressed at around E11.0 in Prox1‐positive lymphatic progenitor cells, with predominant localization in the luminal plasma membrane of lymphatic endothelial cells during later development. T1 α/ podoplanin−/− mice die at birth due to respiratory failure and have defects in lymphatic, but not blood vessel pattern formation. These defects are associated with diminished lymphatic transport, congenital lymphedema and dilation of lymphatic vessels. T1α/podoplanin is also expressed in the basal epidermis of newborn wild‐type mice, but gene disruption did not alter epidermal differentiation. Studies in cultured endothelial cells indicate that T1α/podoplanin promotes cell adhesion, migration and tube formation, whereas small interfering RNA‐mediated inhibition of T1α/podoplanin expression decreased lymphatic endothelial cell adhesion. These data identify T1α/podoplanin as a novel critical player that regulates different key aspects of lymphatic vasculature formation.

/pdf/t1a-podoplanin-deficiency-disrupts-normal-lymphatic-xuuqmzokzy.pdf

T1α/podoplanin deficiency disrupts normal lymphatic vasculature formation and causes lymphedema

Osteoblast and chondroblast differentiation.

The mucin-type glycoprotein podoplanin is specifically expressed by lymphatic but not blood vascular endothelial cells in culture and in tumor-associated lymphangiogenesis, and podoplanin deficiency results in congenital lymphedema and impaired lymphatic vascular patterning. However, research into the biological importance of podoplanin has been hampered by the lack of a generally available antibody against the human protein, and its expression in normal tissues and in human malignancies has remained unclear. We generated a human podoplanin-Fc fusion protein and found that the commercially available mouse monoclonal antibody D2-40 specifically recognized human podoplanin, as assessed by enzyme-linked immunosorbent assay and Western blot analyses. We found that, in addition to lymphatic endothelium, podoplanin was also expressed by peritoneal mesothelial cells, osteocytes, glandular myoepithelial cells, ependymal cells, and by stromal reticular cells and follicular dendritic cells of lymphoid organs. These findings were confirmed in normal mouse tissues with anti-podoplanin antibody 8.1.1. Podoplanin was also strongly expressed by granulosa cells in normal ovarian follicles, and by ovarian dysgerminomas and granulosa cell tumors. Although podoplanin was primarily absent from normal human epidermis, its expression was strongly induced in 22 of 28 squamous cell carcinomas studied. These findings suggest a potential role of podoplanin in tumor progression, and they also identify the first commercially available antibody for the specific staining of a defined lymphatic marker in archival human tissue sections, thereby enabling more widespread studies of tumor lymphangiogenesis in human cancers.

/pdf/up-regulation-of-the-lymphatic-marker-podoplanin-a-mucin-1wh61kflvz.pdf

Up-Regulation of the Lymphatic Marker Podoplanin, a Mucin-Type Transmembrane Glycoprotein, in Human Squamous Cell Carcinomas and Germ Cell Tumors

Growth factors and tumor-promoting phorbol esters induce various types of "early response" genes, most of which encode transcription factors. To identify possible target genes for these early response gene products, we isolated complementary DNA clones of genes that were induced later by 12-O-tetradecanoylphorbol-13-acetate. A complementary DNA library was constructed using mRNA from mouse osteoblastic cells (MC3T3-E1) treated with 12-O-tetradecanoylphorbol-13-acetate for 4 h, and the library was screened by differential hybridization. Five independent clones were isolated. All of these genes were induced maximally 4 to 8 h after 12-O-tetradecanoylphorbol-13-acetate addition. Sequencing showed that three of them (OTS-1, -3, and -4) were those of the metallothionein II gene, and one (OTS-5) was identical to the osteopontin/2ar gene. The other (OTS-8) had no significant homology with known sequences and was considered to be a novel gene. The induction of OTS-5 and OTS-8 was decreased in the presence of cycloheximide. In mice, OTS-8 mRNA was detected in the lungs but not at appreciable levels in other organs. Open reading frame of OTS-8 complementary DNA and its in vitro transcription/translation product suggested that this gene encodes an Mr 26,000 protein. OTS-8 mRNA was induced by epidermal growth factor but not by serum. The steady-state levels of OTS-5 and OTS-8 mRNAs were significantly elevated in v-ras-transformed MC3T3 cells.

http://cgd.aacrjournals.org/cgi/reprint/1/11/511.pdf

Isolation of a gene sequence induced later by tumor-promoting 12-O-tetradecanoylphorbol-13-acetate in mouse osteoblastic cells (MC3T3-E1) and expressed constitutively in ras-transformed cells.

Enhanced Ferroelectric Properties of Nitrogen‐Doped Bi4Ti3O12 Thin Films

Impact of Rapid Thermal Oxidation at Ultrahigh-Temperatures on Oxygen Precipitation Behavior in Czochralski-Silicon Crystals

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2889%2980634-9

Decrease in CuZn-superoxide dismutase mRNA level during differentiation of human monocytic and promyelotic leukemia cells.

The effect of argon ion bombardment on a silicon oxide film prepared on a Si(111) surface by dry oxidation was investigated by measuring partial yield spectra in addition to the oxygen induced Si 2p core level shift. The experimental observations can be understood such that the SiO2 network is decomposed at the initial stage of argon ion bombardment. In the following stage of bombardment, the silicon oxide films are sputter etched resulting in a decrease in the oxide film thickness.

Hiroyuki Saito

Papers

Isolation of a gene sequence induced later by tumor-promoting 12-O-tetradecanoylphorbol-13-acetate in mouse osteoblastic cells (MC3T3-E1) and expressed constitutively in ras-transformed cells.

Enhanced Ferroelectric Properties of Nitrogen‐Doped Bi4Ti3O12 Thin Films

Impact of Rapid Thermal Oxidation at Ultrahigh-Temperatures on Oxygen Precipitation Behavior in Czochralski-Silicon Crystals

Decrease in CuZn-superoxide dismutase mRNA level during differentiation of human monocytic and promyelotic leukemia cells.

Initial stage of sputtering in silicon oxide