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    Netzwerk zur Erforschung von Knochenmetastasen - SkelMetNet

    Die gemeinsame Arbeit beginnt Früchte zu tragen.


    Die DFG hat unsere überregionale Forschergruppen-Initiative Initiative zum Thema "Mesenchymale und osteogene Signalwege in der Knochenmetastasierung" positiv begutachtet und der Verbund wird als DFG-Forschergruppe gefördert. Beteiligt sind die Universitäten Dresden, Kiel, Würzburg, und die Helmholtz-Gesellschaft in München. Derzeit laufen bereits die Vorbereitungen für die Zwischenbegutachtung, die Ende Mai in Dresden stattfinden wird.

     

    Sie finden mehr Informationen unter der SkelMet Webseite http://www.skelmet.de/


    Mehrere gemeinsame Publikation der Arbeitsgruppen in Dresden und Würzburg zum Thema Bisphosphonate und Krebszellen sind mittlerweile erschienen:

     
    Rachner TD, Göbel A, Thiele S, Rauner M, Benad-Mehner P, Hadji P, Bauer T, Muders MH, Baretton GB, Jakob F, Ebert R, Bornhäuser M, Schem C, Hofbauer LC. Dickkopf-1 is regulated by the mevalonate pathway in breast cancer. Breast Cancer Res. 2014 Feb 14;16(1):R20. [Epub ahead of print] 

    INTRODUCTION:
    Amino-bisphosphonates and statins inhibit the mevalonate pathway, and may exert anti-tumor effects. The Wnt inhibitor dickkopf-1 (DKK-1) promotes osteolytic bone lesions by inhibiting osteoblast functions and has been implicated as an adverse marker in multiple cancers. We assessed the effects of mevalonate pathway inhibition on DKK-1 expression in osteotropic breast cancer.

    METHODS:
    Regulation of DKK-1 by bisphosphonates and statins was assessed in human breast cancer cell lines, and the role of the mevalonate pathway and downstream targets was analyzed. Moreover, the potential of breast cancer cells to modulate osteoblastogenesis via DKK-1 was studied in mC2C12 cells. Clinical relevance was validated by analyzing DKK-1 expression in the tissue and serum of women with breast cancer exposed to bisphosphonates.

    RESULTS:
    DKK-1 was highly expressed in receptor-negative breast cancer cell lines. Patients with receptor-negative tumors displayed elevated levels of DKK-1 at the tissue and serum level compared to healthy controls. Zoledronic acid and atorvastatin potently suppressed DKK-1 in vitro by inhibiting geranylgeranylation of CDC42 and Rho. Regulation of DKK-1 was strongest in osteolytic breast cancer cell lines with abundant DKK-1 expression. Suppression of DKK-1 inhibited the ability of breast cancer cells to block WNT3A-induced production of alkaline phosphates and bone-protective osteoprotegerin in preosteoblastic C2C12 cells. In line with the in vitro data, treatment of breast cancer patients with zoledronic acid decreased DKK-1 levels by a mean of 60% after 12 months of treatment.

    CONCLUSION:
    DKK-1 is a novel target of the mevalonate pathway that is suppressed by zoledronic acid and atorvastatin in breast cancer.


    Im Folgenden werden weitere aktuelle gemeinsame Publikationen und Abstrakts aufgelistet:

    Ebert R, Zeck S, Meissner-Weigl J, Klotz B, Rachner TD, Benad P, Klein-Hitpass L, Rudert M, Hofbauer LC, Jakob F. Krüppel-like factors KLF2 and 6 and Ki-67 are direct targets of zoledronic acid in MCF-7 cells. Bone. 2011 Dec 7.

    Bisphosphonates (BP) are used for the treatment of osteoporosis and bone metastases due to breast and prostate cancer. Recent clinical studies indicated a benefit in survival and tumor relapse with the supportive treatment of breast cancer using zoledronic acid (ZA), thus stimulating the debate about its putative anti-tumor activity in vivo. MCF-7 breast cancer cells were treated for 3h (pulse treatment) and 72h (permanent treatment) with ZA, and apoptosis rates and cell viability, defined as ATP content, were determined after 72h. Permanent and pulse stimulation with ZA inhibited the viability of MCF-7 cells, which could partly be rescued by atorvastatin (Ator) pre-treatment but not by geranylgeranyl pyrophosphate (GGPP) co-treatment. Microarray analysis of ZA treated MCF-7 cells identified genes of the mevalonate pathway as significantly upregulated, which was verified by qPCR. Additionally the putative tumor suppressors krüppel-like factor 2 and 6 (KLF2 and KLF6) were markedly upregulated, while the classical proliferation marker Ki-67 was clearly downregulated. The expression of all three genes was confirmed by qPCR on mRNA level and by immunocytochemistry or Western blot staining. Expression of target genes were also analyzed in other breast (MDA-MB-231, BT-20, ZR75-1, T47D) and prostate (LNCaP, PC3) cancer cell lines by qPCR. ZA responsiveness of KLF2, KLF6 and Ki-67 could be verified in PC3 and T47D cells, KLF6 responsiveness in LNCaP and KLF2 responsiveness in MDA-MB-231 and BT-20 cells. Here we demonstrate in the apoptosis insensitive MCF-7 cell line a remarkable impact of ZA exposure on cell viability and on the regulation of putative tumor suppressors of the KLF family. The molecular mechanism involved might be the accumulation of isopentenyl pyrophosphate (IPP) and ApppI, since we could partly rescue the ZA effect by Ator pre-treatment and GGPP co-treatment. These data should stimulate further research into both the role of the mevalonate pathway and the accumulation of pyrophosphate compounds like ApppI in tumorigenesis and differentiation and their potential apart from the inhibition of mitochondrial ADP/ATP translocase and apoptosis, since such effects might well be responsible for the adjuvant ZA treatment benefit of patients suffering from breast cancer.


    Thiele S, Rauner M, Goettsch C, Rachner TD, Benad P, Fuessel S, Erdmann K, Hamann C, Baretton GB, Wirth MP, Jakob F, Hofbauer LC. Expression profile of WNT molecules in prostate cancer and its regulation by aminobisphosphonates. J Cell Biochem. 2011 Jun;112(6):1593-600.

    Skeletal metastases represent a frequent complication in patients with advanced prostate cancer (PCa) and often require bisphosphonate treatment to limit skeletal-related events. Metastasized PCa cells disturb bone remodeling. Since the WNT signaling pathway regulates bone remodeling and has been implicated in tumor progression and osteomimicry, we analyzed the WNT profile of primary PCa tissues and PCa cell lines and assessed its regulation by bisphosphonates. Prostate tissue (n = 18) was obtained from patients with benign prostate hyperplasia (BPH) and PCa patients with different disease stages. Serum samples were collected from 62 patients. Skeletal metastases were present in 17 patients of whom 6 had been treated with zoledronic acid. The WNT profile and its regulation by bisphoshonates were analyzed in tissue RNA extracts and serum samples as well as in osteotropic (PC3) and non-osteotropic (DU145, LNCaP) PCa cell lines. Several members of the WNT pathway, including WNT5A, FZD5, and DKK1 were highly up-regulated in PCa tissue from patients with advanced PCa. Interestingly, osteotropic cells showed a distinct WNT profile compared to non-osteotropic cells. While WNT5A, FZD5, and DKK1 were highly expressed in PC3 cells, WNT1 and SFRP1 mRNA levels were higher in DU145 cells. Moreover, zoledronic acid down-regulated mRNA levels of WNT5A (-34%), FZD5 (-60%), and DKK1 (-46%) in PC3 cells. Interestingly, patients with skeletal metastases who received zoledronic acid had twofold higher DKK1 serum levels compared to bisphosphonate-naive patients. The WNT signaling pathway is up-regulated in advanced PCa, differentially expressed in osteotropic versus non-osteotropic cells, and is regulated by zoledronic acid.


    Rachner T, Singh S; Schoppet M, Bornhäuser M, Ellenrieder V, Ebert R, Jakob F, Hofbauer LC. Zoledronic acid induces apoptosis and changes the TRAIL/OPG ratio in breast cancer cells. Cancer Lett. 2010 Jan 1;287(1):109-16. Epub 2009 Jul 3.

    Breast cancer has a propensity to metastasize to bone, thus causing pathological fractures. Bisphosphonates are established drugs in the treatment of bone metastasis that inhibit osteoclast activity and interrupt the vicious cycle of osteoclast-tumor cell interactions. We evaluated the direct effects of zoledronic acid on estrogen receptor (ER)-negative MDA-MB-231 and ER-positive MCF-7 breast cancer cells. While zoledronic acid (100muM) inhibited MDA-MB-231 cell proliferation after 72h, and induced apoptosis via activation of caspase-3 and -7, it had only minor effects on MCF-7 cells. In addition, zoledronic acid induced apoptosis by up-regulating TNF-related apoptosis-inducing ligand (TRAIL) in MDA-MB-231 cells (p<0.01), but had no effect on the expression of its decoy receptor osteoprotegerin (OPG). In MCF-7 cells, both cytokines were suppressed by zoledronic acid. In conclusion, zoledronic acid enhanced the TRAIL-to-OPG ratio in TRAIL-sensitive MDA-MB-231 cells, indicating that the TRAIL/OPG cytokine system is a bisphosphonate-responsive target in breast cancer.


    Weitere aktuelle gemeinsame Publikationen und Abstrakts:

      • Thiele S, Rauner M, Goettsch C, Rachner TD, Benad P, Fuessel S, Erdmann K, Hamann C, Baretton GB, Wirth MP, Jakob F, Hofbauer LC. Expression profile of WNT molecules in prostate cancer and its regulation by aminobisphosphonates. J Cell Biochem. 2011 Jun;112(6):1593-600. doi: 10.1002/jcb.23070.
      • Ebert R, Zeck S, Krug R, Meissner-Weigl J, Schneider D, Seefried L, Eulert J, Jakob F. Pulse treatment with zoledronic acid causes sustained commitment of bone marrow derived mesenchymal stem cells for osteogenic differentiation.Bone. 2009 May;44(5):858-64. Epub 2009 Jan 23.
      • Jakob F, Benisch P, Klotz B, Seefried L, Mentrup B, Raaijmakers N, Ebert R, Hofbauer L. Sexualsteroide in der Homöostase des Knochens. Osteologie / Osteology 2 / 2010 im Druck
      • Benad P, Rachner TD, Rauner M, Bornhäuser M, Hofbauer LC. Ambivalente Wirkung von Glukokortikoiden auf Mammakarzinomzellen. Osteologie 2 / 2010, im Druck.
      • Günther KP, Hofbauer L, Defer A, Dreinhöfer K, Duda G, Goldhahn J, Jakob F, Kurth A, Linde I, Raschke MJ, Rueger JM, Steinbronn R, Stroszczynski C, Unger L, Zwipp H. Current application of osteoporosis guidelines - expert recommendations of the German Society of Orthopaedic Surgery and Traumatology. Z Orthop Unfall. 2009;147:542-546.
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