Sequential treatment with Dox followed by Zol elicited substantial antitumor effects in subcutaneous breast tumors in vivo, in the absence of bone disease.

Purpose: Clinical trials in early breast cancer have suggested that benefits of adjuvant bone-targeted treatments are restricted to women with established menopause. We developed models that mimic pre-and postmenopausal status to investigate effects of altered bone turnover on growth of disseminated breast tumor cells. Here, we report a differential antitumor effect of zoledronic acid (ZOL) in these two settings.Experimental design: Twleve-week-old female Balb/c-nude mice with disseminated MDA-MB-231 breast tumor cells in bone underwent sham operation or ovariectomy (OVX), mimicking the pre-and postmenopausal bone microenvironment, respectively. To determine the effects of bone-targeted therapy, sham/OVX animals received saline or 100 mg/kg ZOL weekly. Tumor growth was assessed by in vivo imaging and effects on bone by real-time PCR, micro-CT, histomorphometry, and measurements of bone markers. Disseminated tumor cells were detected by two-photon microscopy.Results: OVX increased bone resorption and induced growth of disseminated tumor cells in bone. Tumors were detected in 83% of animals following OVX (postmenopausal model) compared with 17% following sham operation (premenopausal model). OVX had no effect on tumors outside of bone. OVX-induced tumor growth was completely prevented by ZOL, despite the presence of disseminated tumor cells. ZOL did not affect tumor growth in bone in the sham-operated animals. ZOL increased bone volume in both groups.Conclusions: This is the first demonstration that tumor growth is driven by osteoclast-mediated mechanisms in models that mimic post-but not premenopausal bone, providing a biologic rationale for the differential antitumor effects of ZOL reported in these settings. Clin Cancer Res; 20(11); 2922-32. Ó2014 AACR.

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability), which negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process; long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

BackgroundWe have recently identified interleukin 1B (IL-1B) as a potential biomarker for predicting breast cancer patients at increased risk for developing bone metastasis. In mouse models, IL-1B and its receptor (IL-1R1) are upregulated in breast cancer cells that metastasise to bone compared with cells that do not. We have now investigated the functional role of IL-1 by blocking IL-1R signalling with the clinically licensed antagonist, anakinra.Methodology6-week old female BALB/c mice received a subcutaneous or intra-venous injection of MDA-MB-231-IV or MCF7 cells. Anakinra (1mg/kg/day) or placebo was administered 3 days before (preventative) or 7 days later (treatment). Tumour volume, apoptosis (TUNEL, Caspase 3), proliferation (Ki67) and angiogenesis (CD34, VEGF and endothelin) were analysed. Effects on bone were measured by uCT, and TRAP, P1NP, IL-1B, TNF alpha and IL-6 ELISA.ResultsAnakinra significantly reduced growth of MDA-MB-231-IV tumours in bone from 6.50+/3.00mm2 (placebo) to 2.56+/−1.07mm2 (treatment) and 0.63+/−0.18mm2 (preventative). Anakinra also reduced the number of mice that developed bone metastasis from 90% (placebo) to 40% (treatment) and 10% (preventative). Anti-tumour effects were not confined to bone, subcutaneous tumour volumes reduced from 656.68mm3 (placebo) to 160.47mm3 (treatment) and 31.08mm3 (preventative). Anakinra did not increase tumour cell apoptosis but reduced proliferation and angiogenesis in addition to exerting significant effects on the tumour environment reducing bone turnover markers, IL-1B and TNF alpha.ConclusionsOur novel data demonstrate a functional role of IL-1 signalling in breast tumour progression and metastasis, supporting that anakinra could be repurposed for the treatment of breast cancer bone metastasis.