Development and characterization of murine models of medulloblastoma extraneural growth in bone

Authors

Jessica M. Grunda, Dezhi Wang, Gregory A. Clines

Abstract

Medulloblastoma is a malignant pediatric brain neoplasm with an unusual predilection for metastasis to the skeleton. The objective of this study was to generate and characterize murine models of medulloblastoma extraneural growth in bone as ‘discovery tools’ for the identification of unrecognized signal transduction pathways and factors driving metastatic bone disease. To this end, the human Daoy and D283 medulloblastoma cell lines were inoculated into the intratibial medullary space of athymic nude mice. Daoy injected mice developed a primarily osteolytic radiographic and histological phenotype. In contrast, both areas of osteolytic and osteosclerotic activity were evident in D283 inoculated bones. D283 and Daoy cell conditioned media increased in vitro osteoblast differentiation and is consistent with the enhanced bone turnover characteristic of bone metastases. Daoy cells also significantly increased bone marrow osteoclast formation, consistent with the robust in vivo osteolytic phenotype. A survey of secreted factors implicated in bone metastasis and expressed by D283 and Daoy was performed. High expression of the bone-homing factor, CXCR4, was observed in both Daoy and D283 tissues. Consistent with the skeletal phenotypes, Daoy cells, while secreting the osteoblastic factor ET-1, abundantly produced the osteolytic factors RANKL, PTHrP and TNFα. D283 cells produced high levels of both RANKL and ET-1. These newly described animal models of medulloblastoma bone metastasis are expected to serve as platforms to aid in the elucidation of novel bone metastasis signaling cascades and to test therapeutics that target both medulloblastoma metastasis and the primary tumor.

Link to Article

http://dx.doi.org/10.1007/s10585-013-9577-6

PTH prevents the adverse effects of focal radiation on bone architecture in young rats

Authors

Abhishek Chandra, Shenghui Lan, Ji Zhu, Tiao Lin, Xianrong Zhang, Valerie A. Siclari, Allison R. Altman, Keith A. Cengel, X. Sherry Liu, Ling Qin

Abstract

Radiation therapy is a common treatment regimen for cancer patients. However, its adverse effects on the neighboring bone could lead to fractures with a great impact on quality of life. The underlying mechanism is still elusive and there is no preventive or curative solution for this bone loss. Parathyroid hormone (PTH) is a current therapy for osteoporosis that has potent anabolic effects on bone. In this study, we found that focal radiation from frequent scans of the right tibiae in 1-month-old rats by micro-computed tomography severely decreased trabecular bone mass and deteriorated bone structure. Interestingly, PTH daily injections remarkably improved trabecular bone in the radiated tibiae with increases in trabecular number, thickness, connectivity, structure model index and stiffness, and a decrease in trabecular separation. Histomorphometric analysis revealed that radiation mainly decreased the number of osteoblasts and impaired their mineralization activity but had little effects on osteoclasts. PTH reversed these adverse effects and greatly increased bone formation to a similar level in both radiated and non-radiated bones. Furthermore, PTH protects bone marrow mesenchymal stem cells from radiation-induced damage, including a decrease in number and an increase in adipogenic differentiation. While radiation generated the same amount of free radicals in the bone marrow of vehicle-treated and PTH-treated animals, the percentage of apoptotic bone marrow cells was significantly attenuated in the PTH group. Taken together, our data demonstrate a radioprotective effect of PTH on bone structure and bone marrow and shed new light on a possible clinical application of anabolic treatment in radiotherapy.

Link to Article

http://dx.doi.org/10.1016/j.bone.2013.02.023

Antagonism of Inhibitor of Apoptosis Proteins Increases Bone Metastasis via Unexpected Osteoclast Activation

Authors

Chang Yang, Jennifer L. Davis, Rong Zeng, Paras Vora, Xinming Su, Lynne I. Collins, Suwanna Vangveravong, Robert H. Mach, David Piwnica-Worms, Katherine N. Weilbaecher, Roberta Faccio, and Deborah Veis Novack

Abstract

Inhibitor of apoptosis (IAP) proteins play a central role in many types of cancer, and IAP antagonists are in development as anticancer agents. IAP antagonists cause apoptosis in many cells, but they also activate alternative NF-κB signaling through NF-κB–inducing kinase (NIK), which regulates osteoclasts. In bone metastasis, a positive feedback loop between tumors and osteoclasts promotes tumor growth and osteolysis. We therefore tested the effect of IAP antagonists on the bone microenvironment for metastasis. In both drug-sensitive and drug-resistant tumors, growth in bone was favored, as compared with other sites during IAP antagonist treatment. These drugs also caused osteoporosis and increased osteoclastogenesis, mediated by NIK, and enhanced tumor-associated osteolysis. Cotreatment with zoledronic acid, a potent osteoclast inhibitor, reduced IAP antagonist–enhanced tumor growth in bone and osteolysis. Thus, IAP antagonist–based cancer treatment may be compromised by osteoporosis and enhanced skeletal metastasis, which may be prevented by antiresorptive agents. Significance: Although IAP antagonists are a class of anticancer agents with proven efficacy in multiple cancers, we show that these agents can paradoxically increase tumor growth and metastasis in the bone by stabilizing NIK and activating the alternative NF-κB pathway in osteoclasts. Future clinical trials of IAP antagonist–based therapy may require detailed examination of this potential for enhanced bone metastasis and osteoporosis, as well as possible combination with antiresorptive agents.

Link to Article

http://dx.doi.org/10.1158/2159-8290.CD-12-0271

Halofuginone inhibits the establishment and progression of melanoma bone metastases

Authors

Patricia Juárez, Khalid S. Mohammad, Juan Juan Yin, Pierrick G. J. Fournier, Ryan C. McKenna, Holly W Davis, Xiang H. Peng, Maria Niewolna, Delphine Javelaud, John M Chirgwin, Alain Mauviel, and Theresa A. Guise

Abstract

Transforming growth factor (TGF-β) derived from bone fuels melanoma bone metastases by inducing tumor secretion of pro-metastatic factors that act on bone cells to change the skeletal microenvironment. Halofuginone is a plant alkaloid derivative that blocks TGF-β signaling with antiangiogenic and antiproliferative properties. Here, we demonstrate for the first time that halofuginone therapy decreases development and progression of bone metastasis caused by melanoma cells through inhibition of TGF-β signaling. Halofuginone treatment of human melanoma cells inhibited cell proliferation, phosphorylation of SMAD proteins in response to TGF-β, and TGF-β-induced SMAD-driven transcription. In addition, halofuginone reduced expression of TGF-β target genes that enhance bone metastases, including PTHrP, CTGF, CXCR4, and IL11. Also, cell apoptosis was increased in response to halofuginone. In nude mice inoculated with 1205Lu melanoma cells, a preventive protocol with halofuginone inhibited bone metastasis. The beneficial effects of halofuginone treatment were comparable to those observed with other anti-TGF-β strategies, including systemic administration of SD208, a small molecule inhibitor of TGF-β receptor I kinase, or forced overexpression of Smad7, a negative regulator of TGF-β signaling. Furthermore, mice with established bone metastases treated with halofuginone had significantly less osteolysis than mice receiving placebo assessed by radiographys. Thus, halofuginone is also effective in reducing the progression of melanoma bone metastases. Moreover, halofuginone treatment reduced melanoma metastasis to the brain, showing the potential of this novel treatment against cancer metastasis.

Link to Article

http://dx.doi.org/10.1158/0008-5472.CAN-12-1444

RANKL inhibition combined with tamoxifen treatment increases anti-tumor efficacy and prevents tumor-induced bone destruction in an estrogen receptor-positive breast cancer bone metastasis model

Authors

Jude Canon, Rebecca Bryant, Martine Roudier, Daniel G. Branstetter and William C. Dougall

Abstract

Tumor cells in bone can induce the activation of osteoclasts, which mediate bone resorption and release of growth factors and calcium from the bone matrix, resulting in a cycle of tumor growth and bone breakdown. Targeting the bone microenvironment by the inhibition of RANKL, an essential mediator of osteoclast function, not only prevents tumor-induced osteolysis but also decreases skeletal tumor burden in preclinical models. The inhibition of skeletal tumor progression after the inhibition of osteoclasts is via interruption of the “vicious cycle” of tumor/bone interactions. The majority of breast cancer patients at risk for bone metastases harbor estrogen receptor-positive (ER+) tumors. We developed a mouse model for ER+ breast cancer bone metastasis and evaluated the effect of RANKL inhibition on tumor-induced osteolysis and skeletal tumor growth both alone and in combination with tamoxifen. Luciferase-labeled MCF-7 cells (MCF-7Luc) formed metastatic foci in the hind limbs following intracardiac injection and caused mixed osteolytic/osteoblastic lesions. RANKL inhibition by OPG-Fc treatment blocked osteoclast activity and prevented tumor-induced osteolysis, as well as caused a marked decrease in skeletal tumor burden. Tamoxifen as a single agent reduced MCF-7Luc tumor growth in the hind limbs. In a combination experiment, OPG-Fc plus tamoxifen resulted in significantly greater tumor growth inhibition than either single agent alone. Histologic analysis revealed a decrease in the proliferation of tumor cells by both single agents, which was enhanced in the combination treatment. Upon treatment with OPG-Fc alone or in combination with tamoxifen, there was a complete absence of osteolytic lesions, demonstrating the ability of RANKL inhibition to prevent skeletal related morbidity in an ER+ model. The combination approach of targeting osteoclasts and the bone microenvironment by RANKL inhibition and the tumor directly via hormonal therapy may provide additional benefit to reducing skeletal tumor progression in ER+ breast cancer patients.

Link to Article

http://dx.doi.org/10.1007/s10549-012-2222-2

Effects of androgen deprivation therapy and bisphosphonate treatment on bone in patients with...

Authors

Colm Morrissey, Martine P. Roudier, Alex Dowell, Lawrence D. True, Melanie Ketchanji, Christopher Welty, Eva Corey, Paul H. Lange, Celestia S. Higano, Robert L. Vessella

Abstract

Qualitative and quantitative bone features were determined in nondecalcified and decalcified bone from 20 predetermined bone sites in each of 44 patients who died with castration resistant prostate cancer (CRPC), some of which received bisphosphonate treatment (BP) in addition to androgen deprivation therapy (ADT). Thirty nine of the 44 patients (89%) had evidence of bone metastases. By histomorphometric analysis, these bone metastases were associated with a range of bone responses from osteoblastic to osteolytic with a wide spectrum of bone responses often seen within an individual patient. Overall, the average bone volume/tissue volume (BV/TV) was 25.7% confirming the characteristic association of an osteoblastic response to prostate cancer bone metastasis when compared to the normal age-matched weighted mean BV/TV of 14.7%. The observed new bone formation was essentially woven bone and this was a localized event. In comparing BV/TV at metastatic sites between patients who had received BP treatment and those that had not, there was a significant difference (28.6% vs 19.3%, respectively). At bone sites that were not invaded by tumor, the average BV/TV was 10.1% indicating significant bone loss due to ADT that was not improved (11%) in those patients who had received BPs. Surprisingly there was no significant difference in the number of osteoclasts present at the metastatic sites between patients treated or not treated with BPs but in bone sites where the patient had been treated with BPs, giant osteoclasts were observed. Overall, 873 paraffin embedded specimens and 661 methylmethacrylate embedded specimens were analyzed. Our results indicate that in CRPC patients, ADT induces serious bone loss even in patients treated with BP. Furthermore, in this cohort of patients, BP treatment increased BV and did not decrease the number of osteoclasts in prostate cancer bone metastases compared to bone metastases from patients who did not receive BP.

Link to Article

http://dx.doi.org/10.1002/jbmr.1749