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      Cinobufagin Suppresses The Characteristics Of Osteosarcoma Cancer Cells By Inhibiting The IL-6-OPN-STAT3 Pathway

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          Current clinical treatments for osteosarcoma are limited by disease recurrence and primary or secondary chemoresistance. Cancer stem-like cells have been proposed to facilitate the initiation, progression, recurrence and chemoresistance of osteosarcoma. Furthermore, previous studies have reported that IL-6-STAT3 pathway is overexpressed in various types of cancer and contributes to cell proliferation, apoptosis, invasion/migration, chemoresistance and modulation of stemness features.


          To examined the effect of cinobufagin on cancer progression and modulation of stemness features in osteosarcoma, and investigated the molecular mechanisms underlying such effects.


          Human osteosarcoma cell lines U2OS/MG-63 were recruited in this study. Cell proliferation, migration, and invasion were determined by MTT assay, colony formation assay,wound healing assay, and cell invasion assay respectively. Its effect on stemness was assessed by flow cytometry and mammosphere formation. The protein expression levels of related proteins were detected by Western blot. The xenograft model, immunofluorescence staining and immunohistochemistry were used to determine the effect of cinobufagin on tumorigenicity in vivo experiment.


          We found that cinobufagin suppressed the viability of U2OS/MG-63 spheroids/parent cells in a time-and dose-dependent manner. Notably, cinobufagin had no effect on the viability of hFOB 1.19 cells. Moreover, cinobufagin induced apoptosis, increased the width of wounds, reduced invasive osteosarcoma spheroids/parent cell numbers and reduced EMT phenotype and OPN levels in U2OS/MG-63 spheroids as well as U2OS/MG-63 parent cells lines. Noticeablely, we found that OPN levels were higher in spheroids group than that in parent cells. In addition, cinobufagin ameliorated the proportion of CD133-positive cells, the size of spheroids and Nanog, Sox-2 and Oct3/4 protein levels. Our in vivo experiments showed that cinobufagin consistently reduced tumor volume,the expressions of OPN, Sox-2, Oct3/4, Nanog and p-STAT3 by the immuno histochemistry staining as well as CD133 expression in tumor tissues by immunofluorescence analysis. From a mechanistic point of view, cinobufagin was shown to inhibit IL-6-OPN-STAT3 signaling pathway. Exogenous IL-6/OE-OPN/overexpression STAT3 attenuated the induction of cinobufagin-mediated apoptosis and the suppression of stemness properties respectively.


          Collectively, our data demonstrated that cinobufagin inhibited the viability and tumorigenesis capability of osteosarcoma cells by blocking IL-6- OPN-STAT3 signaling pathway. Cinobufagin may therefore represent a promising therapeutic agent for osteosarcoma management.

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          Most cited references 46

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           J Sodek,  B Ganss,  M.D. McKee (2016)
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            Osteogenic BMPs promote tumor growth of human osteosarcomas that harbor differentiation defects.

            Osteosarcoma (OS) is the most common primary malignancy of bone. Here, we investigated a possible role of defective osteoblast differentiation in OS tumorigenesis. We found that basal levels of the early osteogenic marker alkaline phosphatase (ALP) activity were low in OS lines. Osteogenic regulators Runx2 and OSX, and the late marker osteopontin (OPN) expressed at low levels in most OS lines, indicating that most OS cells fail to undergo terminal differentiation. Furthermore, OS cells were refractory to osteogenic BMP-induced increases in ALP activity. Osteogenic BMPs were shown to upregulate early target genes, but not late osteogenic markers OPN and osteocalcin (OC). Furthermore, osteogenic BMPs failed to induce bone formation from human OS cells, rather effectively promoted OS tumor growth in an orthotopic OS model. Exogenous expression of early target genes enhanced BMP-stimulated OS tumor growth, whereas osteogenic BMP-promoted OS tumor growth was inhibited by exogenous Runx2 expression. These results suggest that alterations in osteoprogenitors may disrupt osteogenic differentiation pathway. Thus, identifying potential differentiation defects in OS tumors would allow us to reconstruct the tumorigenic events in osteoprogenitors and to develop rational differentiation therapies for clinical OS management.
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              Biologic sequelae of interleukin-6 induced PI3-K/Akt signaling in multiple myeloma.

              Previous studies demonstrate that interleukin-6 (IL-6) mediates growth and survival in human multiple myeloma (MM) cells via the MEK/MAPK and JAK/STAT signaling pathways, respectively. IL-6 also confers protection against Dexamethasone (Dex)-induced apoptosis via activation of protein tyrosine phosphatase (SHP2). In the current study, we characterized IL-6 triggered phophatidylinositol-3 kinase/Akt kinase (PI3-K/Akt) signaling in MM cells. IL-6 induces Akt/PKB phosphorylation in a time and dose dependent manner in MM.1S MM cells. IL-6 also induced phosphorylation of downstream targets of Akt, including Bad, GSK-3beta, and FKHR, confirming Akt activation. Inhibition of Akt activation by the PI3-K inhibitor LY294002 partially blocked IL-6 triggered MEK/MAPK activation and proliferation in MM.1S cells, suggesting cross-talk between PI3-K and MEK signaling. We demonstrate that Dex-induced apoptosis in MM.1S cells is mediated by downstream activation of caspase-9, with resultant caspase-3 cleavage; and conversely, that IL-6 triggers activation of PI3-K and its association with SHP2, inactivates caspase-9, and protects against Dex-induced apoptosis. LY294002 completely abrogates this signaling cascade, further confirming the importance of PI3-K/Akt signaling in conferring the protective effect of IL-6 against Dex-induced apoptosis. Finally, we show that IL-6 triggered PI3-K/Akt signaling in MM.1S cells inactivates forkhead transcriptional factor (FKHR), with related G1/S phase transition, whereas LY294002 blocks this signaling, resulting in upregulation of p27(KIP1) and G1 growth arrest. Our data therefore suggest that PI3-K/Akt signaling mediates growth, survival, and cell cycle regulatory effects of IL-6 in MM.

                Author and article information

                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                04 December 2019
                : 13
                : 4075-4090
                [1 ]Luoyang Orthopaedic-Traumatological Hospital and Henan Orthopaedic Hospital , Luoyang, Henan 471002, People’s Republic of China
                Author notes
                Correspondence: Kun Ma; Wu-Yin Li Luoyang Orthopaedic-Traumatological Hospital , 82 QiMing Road, Luoyang, Henan471002, People’s Republic of China Email makun@lyzhenggu.cn; lyzg090915@hotmail.com

                These authors contributed equally to this work

                © 2019 Zhang et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                Page count
                Figures: 8, References: 55, Pages: 16
                Original Research


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