Osteolytic Bone Metastases Research Articles

Radiation therapy combined with bone-modifying agents ameliorates local control of osteolytic bone metastases in breast cancer.

Bone-modifying agents (BMAs) are frequently used for the treatment of bone metastases. Both BMA and radiation therapy (RT) are effective; however, there are few studies that have evaluated the efficacy of the combination treatment. We evaluated the effectiveness of RT + BMA in breast cancer-induced osteolytic bone metastasis as compared to BMA alone. A total of 43 lesions in 25 patients were evaluated. The median follow-up period was 18 (range, 2–90) months. None of the lesions was treated with chemotherapy or molecular targeted drugs during the follow-up period for evaluating the local response. Patients with complete or partial response were considered as responders, while those with stable or progressive disease were considered as non-responders. The rate of response with RT + BMA was significantly higher than that with BMA alone (P = 0.001). The cumulative incidence rate of response at 6 months was 54.4% in the RT + BMA group and 27.5% in the BMA alone group. The median time to response was 4 (range, 2–11) months in the RT + BMA group and 6 (range, 4–16) months in the BMA alone group. The overall survival rate in the responder group (83.1% at 1 year) was significantly higher than that in the non-responder group (37.5% at 1 year) (P = 0.029). In conclusion, RT combined with BMA was found to be more effective than BMA alone for the treatment of osteolytic bone metastasis, which thereby improves the prognosis.

TIE2 Induces Breast Cancer Cell Dormancy and Inhibits the Development of Osteolytic Bone Metastases.

Breast cancer (BCa) cells disseminating to the bone can remain dormant and resistant to treatments for many years until relapsing as bone metastases. The tyrosine kinase receptor TIE2 induces the dormancy of hematopoietic stem cells, and could also induce the dormancy of BCa cells. However, TIE2 is also a target for anti-angiogenic treatments in ongoing clinical trials, and its inhibition could then restart the proliferation of dormant BCa cells in bone. In this study, we used a combination of patient data, in vitro, and in vivo models to investigate the effect of TIE2 in the dormancy of bone metastases. In BCa patients, we found that a higher TIE2 expression is associated with an increased time to metastases and survival. In vitro, TIE2 decreased cell proliferation as it increased the expression of cyclin-dependent kinase inhibitors CDKN1A and CDKN1B and arrested cells in the G0/G1 phase. Expression of TIE2 also increased the resistance to the chemotherapeutic 5-Fluorouracil. In mice, TIE2 expression reduced tumor growth and the formation of osteolytic bone metastasis. Together, these results show that TIE2 is sufficient to induce dormancy in vitro and in vivo, and could be a useful prognostic marker for patients. Our data also suggest being cautious when using TIE2 inhibitors in the clinic, as they could awaken dormant disseminated tumor cells.

Lung Cancer Cells Derived Circulating miR-21 Promotes Differentiation of Monocytes into Osteoclasts.

ObjectiveOsteoclastogenesis is a key process in osteolytic bone metastasis (BM). Previous studies indicated that some miRNAs could regulate cancers progression and osteoclastogenesis. Our purpose was to investigate the roles of lung cancer cells-derived circulating miR-21 on osteoclastogenesis and its clinical significance in BM patients.Materials and MethodsThe difference of miRNA expression in two lung cancer cell lines SBC-5 (with characteristic BM ability) and SBC-3 (without BM ability) were analyzed by microarray and qRT-PCR. Circulating miR-21 levels of lung cancer patients with or without BM were compared by qRT-PCR. The TRAP staining was used to investigate the effects of conditioned media from lung cancer cell lines or patients’ plasma with different miR-21 levels on osteoclastogenesis. ROC curve was used to evaluate the diagnostic performance of circulating miR-21 in BM patients.ResultsWe found that miR-21 expression was specifically higher in SBC-5 than that in SBC-3 cells. The supernatants of SBC-5 cells with higher-level miR-21 promoted osteoclastogenesis. Moreover, we demonstrated that the circulating miR-21 level was significantly higher in BM patients than that in non-BM patients. The plasma from BM patients with higher-level miR-21 could also promote osteoclastogenesis. Mechanistically, lung cancer cells-derived circulating miR-21 could be transferred into osteoclast precursor cells and promote osteoclastogenesis probably by inhibiting PTEN. Finally, clinical data showed that circulating miR-21 had a potential for the diagnosis of BM.ConclusionOverall, our findings suggested that circulating miR-21 played important roles in osteoclastogenesis of lung cancer patients and may serve as a biomarker to diagnose BM of lung cancer.

Longitudinal evaluation of Wnt inhibitors and comparison with others serum osteoimmunological biomarkers in osteolytic bone metastasis

Bone and the immune system are closely linked: bone regulates the hematopoietic stem cells, which are precursors of immune cells, and several immunoregulatory cytokines influence the differentiation of bone cells, thus defining the osteoimmunological system. Cytokines and growth factors produced by immune and bone cells promote tumors in bone, supporting the vicious cycle of bone metastasis. Therefore osteoimmunological molecules linking the immune and bone systems could have diagnostic and prognostic potential for bone metastases. The osteoimmunologic Wnt pathway has been recently described as an important pathway with a vital role in bone carcinogenesis and metastatic progression. We examined the Wnt inhibitor DKK-1, sclerostin and several other osteoimmunological biomarkers involved in bone metastatic progression: RANKL, OPG, OPN, matrix metalloproteinase MMP-3 and the Receptor of Advanced Glycosylated End-products sRAGE. OPN and sclerostin proved good biomarkers of metastatic bone progression; the RANKL/OPG ratio was a good indicator of bone erosion in the metastatic process, while sRAGE had a protective role against metastatic progression in bone. These results serve to define a panel of new osteoimmunological biomarkers that could be useful in assessing the progress of osteolytic bone metastases.

Retrospective analysis of CT-guided percutaneous cryoablation for treatment of painful osteolytic bone metastasis

This study aimed to evaluate the safety and effectiveness of CT-guided percutaneous cryoablation for treatment of painful osteolytic bone metastases. A total of 26 patients (36 bone metastases) treated with CT-guided percutaneous cryoablation between May 2012 and June 2016 were enrolled in this retrospective study. All procedures were performed under local anesthesia. A visual analog scale (VAS) was used to evaluate pain before the procedure and at 1 day, 1 month, 3 months, and 6 months after the procedure. Complications during and after the procedure were recorded and graded by the Clavien–Dindo classification. The mean VAS pain score was 7.1 ± 1.1 (range, 4–10) before cryoablation. It was significantly lower at all timepoints after treatment: 2.1 ± 1.7 (P < 0.0001) at 1 day after treatment, 1.3 ± 1.8 (P < 0.0001) at 1 month, 1.6 ± 1.7 (P < 0.0001) at 3 months, and 1.8 ± 1.3 (P < 0.0001) at 6 months. The response rates were 91.7%, 94.4%, 91.7%, and 94.4%, respectively, at 1 day, 1 month, 3 months, and 6 months after cryoablation; the complete response rates were 22.2%, 41.7%, 36.1%, and 22.2%, respectively. Adverse events (skin frostbite, nerve injury, pathologic fracture) occurred in 3 patients. CT-guided percutaneous cryoablation under local anesthesia appears to be a safe and effective treatment for painful osteolytic bone metastases. Prospective clinical trials on large samples needed to confirm this conclusion.

LIGHT/TNFSF14 Promotes Osteolytic Bone Metastases in Non-small Cell Lung Cancer Patients.

Tumor necrosis factor superfamily member 14 (TNFSF14), LIGHT, is a component of the cytokine network that regulates innate and adaptive immune responses, which promote homeostasis of lymphoid organs, liver, and bone. Metastatic tumors often disrupt the tissue microenvironment, thus altering the homeostasis of the invaded organ; however, the underlying mechanisms required further studies. We investigated the role of LIGHT in osteolytic bone disease induced by metastatic non-small cell lung cancer (NSCLC). Patients diagnosed with NSCLC bone metastasis show significantly higher levels of LIGHT expressed in monocytes compared with non-bone metastatic tumors and healthy controls. Serum LIGHT levels were also higher in patients with bone metastases than in controls, suggesting a role for LIGHT in stimulating osteoclast precursors. In bone metastatic patients, we also detected increased RNA expression and serum RANKL levels, thus by adding anti-LIGHT or RANK-fragment crystallizable region (RANK-Fc) in PBMC cultures, a significant inhibition of osteoclastogenesis was observed. To model this observation in mice, we used the mouse lung cancer cell line LLC-1. After intratibial implantation, wild-type mice showed an increased number of osteoclasts but reduced numbers of osteoblasts and decreased osteoid formation. In contrast, Tnfsf14-/- mice showed no significant bone loss or other changes in bone homeostasis associated with this model. These data indicate LIGHT is a key control mechanism for regulating bone homeostasis during metastatic invasion. Thus, LIGHT may be a novel therapeutic target in osteolytic bone metastases. © 2019 American Society for Bone and Mineral Research.

Clinical features and prognostic factors in patients with esophageal cancer with bone metastasis.

There have been few reports on bone metastases (BMs) from esophageal cancer (EC). The aim of the present study was to investigate the clinicopathological features and prognostic factors in patients with EC with BMs. The present study retrospectively collected data from 58 patients with BMs from EC who were treated at our institution between 2007 and 2016. Patient, tumor and BM-associated characteristics were analyzed. Kaplan-Meier survival curves were constructed and analyzed using the univariate log-rank test. Multivariate analyses were conducted using the Cox proportional hazards model. The median patient age was 67 years (range, 39–84 years). Multiple BMs were detected in 38 patients (65.5%) and 52 patients (89.7%) exhibited osteolytic BMs. Skeletal-related events (SREs) occurred in 53 patients (91.4%). The one-year overall survival (OS) was 25.3%, and the median OS was 5 months (range, 0–54). Univariate analyses revealed that performance status, visceral or brain metastasis, serum carcinoembryonic antigen (CEA), C-reactive protein, albumin level, and receipt of chemotherapy following BM diagnosis were significantly associated with OS. Multivariate analyses of these factors demonstrated that higher serum CEA levels and no chemotherapy were significant risk factors for poor OS. Multiple osteolytic BMs are frequently observed in patients with EC with BMs, and SREs commonly occur. The prognoses of patients with EC with BMs are poor, but chemotherapy administration following the BM diagnosis should confer a survival benefit.

A CTGF-RUNX2-RANKL Axis in Breast and Prostate Cancer Cells Promotes Tumor Progression in Bone.

Metastasis to bone is a frequent occurrence in patients with breast and prostate cancers and inevitably threatens the patient's quality of life and survival. Identification of cancer-derived mediators of bone metastasis and osteolysis may lead to novel therapeutic strategies. In this study, we established highly bone-metastatic PC3 prostate and MDA-MB-231 (MDA) breast cancer cell sublines by in vivo selection in mice. In bone-metastatic cancer cells, the expression and secretion of connective tissue growth factor (CTGF) were highly upregulated. CTGF knockdown in bone-metastatic cells decreased invasion activity and MMP expression. RUNX2 overexpression in the CTGF knockdown cells restored the invasion activity and MMP expression. In addition, CTGF increased RUNX2 protein stability by inducing its acetylation via p300 acetyl transferase. The integrin αvβ3 receptor mediated these effects of CTGF. Furthermore, CTGF promoted RUNX2 recruitment to the RANKL promoter, resulting in increased RANKL production from the tumor cells and subsequent stimulation of osteoclastogenesis from precursor cells. In addition, animal model with injection of CTGF knocked-down prostate cancer cells into 6-week old BALB/c male mice showed reduced osteolytic lesions. More importantly, the expression levels of CTGF and RANKL showed a strong positive correlation in human primary breast tumor tissues and were higher in bone metastases than in other site metastases. These findings indicate that CTGF plays crucial roles for osteolytic bone metastasis both by enhancing invasiveness of tumor cells and by producing RANKL for osteoclastogenesis. Targeting CTGF may lead to the development of effective preventive and therapeutic strategies for osteolytic metastasis. © 2019 American Society for Bone and Mineral Research.

Tumor ablation using novel photothermal NaxWO3 nanoparticles against breast cancer osteolytic bone metastasis.

BackgroundsProfiting from the development of nanomaterials, photothermal therapy (PTT) has been discovered as efficient tumor ablation strategy for breast cancer.Materials and methodsNovel oxygen vacancy-rich tungsten bronze nanoparticles (NaxWO3) were synthesized through a simple pyrogenic decomposition process. TEM, XRD, UV-vis-NIR, photothermal conversion ability, and photothermal stability were performed. The viabilities of 293T and 4T1 cells after treating with 200 μg/mL NaxWO3 nanoparticles for 24 or 48 hrs were both above 80%, which proved the good biosafety and cytotoxicity of NaxWO3 in vitro. Two in vivo breast cancer models, namely percutaneous and intratibial 4T1 models were established and NaxWO3 (20 mg/kg) with power intensity of 1.5 W/cm2 980 nm laser photothermal treatment was used in vivo.ResultsWe successfully synthesized ~150 nm NaxWO3 nanoparticles with desirable PTT effects, as evidenced by the temperature increase from 25.8°C to 41.8°C in 5 mins under the irradiation of 980 nm laser (1 mg/mL). Also, cellular compatibility of NaxWO3 nanoparticles was found upon physiologic 293T cells, in contrast with significant cytotoxicity against breast cancer 4T1 cell in vitro dose-dependently. Besides, two in vivo breast cancer models showed the decent tumor ablation ability of NaxWO3 nanoparticles, demonstrating percutaneous 4T1 tumor elimination without recurrence during 2 weeks observation as well as intratibial breast cancer inhibition with decreased bone destruction and tumor volume after NaxWO3+PTT in vivo.ConclusionFor the first time, we developed a novel oxygen vacancy-rich tungsten bronze nanoparticles (NaxWO3) through a simple pyrogenic decomposition process for PTT. Both in vitro and in vivo experiments showed the good PTT ability and tumor ablation effects of synthesized NaxWO3 nanoparticles against breast cancer osteolytic bone metastasis. Additionally, our oxygen-deficient NaxWO3 nanoparticles will expand the research horizons of PTT nanomaterials.

Abstract 1970: Melatonin inhibits osteolytic bone metastasis through interrupting cancer cells-derived osteolytic factor and reduce osteoclast differentiation

Abstract Osteolytic bone metastasis is seen in lung, breast, and prostate cancer and is associated with severe complications such as bone pain, fractures and hypercalcemia. In the bone microenvironment, osteoclasts play an important role in bone remodeling and bone resorption. Metastatic cancer cells may increase osteoclast differentiation and activity by releasing inflammatory cytokines including receptor activator of nuclear factor kappa-B ligand (RANKL), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and IL-8, leading to bone resorption and osteolytic lesions. The endogenous hormone melatonin is known to modulate bone resorption. Increasing evidence suggests that melatonin inhibits cancer cell proliferation, angiogenesis and metastasis. Up until now, the inhibitory role of melatonin in osteolytic bone metastasis has remained unclear. In In vitro study, we observed that melatonin inhibits the differentiation of precursor osteoclasts and promotes apoptosis in mature osteoclasts. We injected mice tibia with luciferase-labeled osteolytic cancer cell lines (lung cancer: A549, prostate cancer: PC-3) to establish bone metastasis. After 4 weeks of intraperitoneal injection with melatonin, IVIS fluorescence signaling indicated that melatonin inhibited tumor growth. X-ray imaging of the bone revealed an improvement in bone resorption after melatonin treatment. In In vitro melatonin also reduced RANKL protein and mRNA expression in the A549 and PC-3 cell lines. Our data indicate that melatonin improves bone mass by inhibiting the expression of cancer-derived osteolytic factors and by promoting apoptosis in mature osteoclasts. Our future investigations will seek to determine the signaling pathway involved in melatonin-regulated RANKL expression in cancer cells. In summary, our findings provide insight into the benefits of melatonin treatment in osteolytic bone metastasis. Citation Format: Jyun-Lin Lai, An-Chen Chang, Po-Chun Chen, Chih-Hsin Tang. Melatonin inhibits osteolytic bone metastasis through interrupting cancer cells-derived osteolytic factor and reduce osteoclast differentiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1970.

Abstract 3134: CCN3 is a prognostic biomarker and functional mediator of prostate cancer bone metastasis

Abstract Background: Prostate cancer commonly metastasizes to the bone, resulting in pathological fractures and poor prognosis. CCN3/NOV (Nephroblastoma overexpressed) is a secreted protein with a known role in breast cancer metastasis to bone. However, in prostate cancer, CCN3 has been ascribed conflicting roles; some studies suggest that CCN3 promotes prostate cancer metastasis while others argue a tumor suppressor role for CCN3 in this disease. Indeed, in the latter context, CCN3 has been shown to sequester the androgen receptor (AR) and suppress AR signaling. The C-terminal domain of CCN3 is thought to mediate many the protein’s pro-metastatic functions given its role in binding to growth factors and promoting dimerization of CCN family members. We hypothesize that the CCN3 CT domain is required to promote osteolytic PC bone metastasis and that CCN3 represents a prognostic biomarker in primary PC tumors to predict recurrence to bone. Methods: CCN3WT and CCN3ΔCT were overexpressed in LNCaP C4-2 cells. The role of CCN3 was assessed with in vitro proliferation, migration and invasion assays, and in vivo through intracardiac injection in male Nude mice (Nu/Nu). Ex vivo µCT scans were performed on murine bone metastasis specimens. CCN3 expression was assessed in two unique tissue microarrays (TMA) comprising over 1500 human primary prostate tumor using different anti-CCN3 antibodies with immunohistochemistry and immunohistofluorescnece, respectively. Results: While CCN3WT and CCN3ΔCT had little effect in vitro on cell proliferation, migration or invasion, intracardiac injection of CCN3WT resulted in increased incidence of bone metastasis compared to empty vector control and CCN3ΔCT. Ex vivo µCT revealed decreased bone mineral density in bones from mice injected with CCN3WT cells compared to empty vector control and CCN3ΔCT expressing LNCaP C4-2 cells. In both TMAs studied, high CCN3 expression in tumor epithelium correlated with increased risk of biochemical relapse and bone metastasis at 5 years and 15 years post- surgical resection, respectively. Conclusion: CCN3 requires its C-terminal domain for its bone metastatic function, and CCN3 is correlated with aggressive disease biology in primary prostate cancer specimens. These findings point to CCN3 protein expression as a biomarker that can be useful in predicting prostate cancer aggressiveness and recurrence to bone, while providing clarity on CCN3’s functional role as a mediator of prostate cancer bone metastasis. Citation Format: Matthew Dankner, Veronique Ouellet, Laudine Desreumaux-Communal, Estelle Schmitt, Dru Perkins, Matthew G. Annis, Veronique Barres, Christine Caron, Anne-Marie Mes-Masson, Fred Saad, Peter M. Siegel. CCN3 is a prognostic biomarker and functional mediator of prostate cancer bone metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3134.

Abstract 3936: Efficacy of single agent radium-223 in the syngeneic MBT-2 bladder cancer bone growth model in mice

Abstract Radium-223 dichloride (Ra-223, Xofigo®) is a targeted alpha therapy which prolongs the survival of castration-resistant prostate cancer (CRPC) patients with symptomatic bone metastases. As a calcium-mimetic, Ra-223 selectively binds to hydroxyapatite and targets areas of high bone turnover such as bone metastases. Here, we report the effects of Ra-223 on development and progression of osteolytic bone lesions and on survival in the syngeneic intratibial MBT-2 murine bladder cancer model in immunocompetent mice. Female 5-7-week-old C3H/HeNHsd mice were injected intratibially with 5x105 MBT-2 cells on day 0. The mice were stratified based on body weight (n=40 per group) on day 5 and Ra-223 (300 kBq/kg, i.v.) or vehicle control was administered on days 5, 33, and 61. The tumor-induced osteolytic lesion area was imaged using radiography on days 10, 18, 25, 76, and at sacrifice. The mice were sacrificed when they met the pre-defined sacrifice criteria (&amp;gt; 20% body weight loss, palpable tumor outgrowth from the bone or general deterioration of health status). The study was terminated on day 158. In this study, the first mice met the sacrifice criteria on study day 24 and the survival curves plateaued at 52% after 84 days in the control group and at 68% after 112 days in the Ra-223 treatment group. Survival on day 40 was significantly improved in the Ra-223 treatment group compared to the vehicle control (p&amp;lt; 0.001), but the effect was not statistically significant at the end of the study. Based on X-ray imaging 25 days after cancer cell inoculation, Ra-223 treatment also significantly decreased the bone lesion area compared to the vehicle treatment (p=0.0041). After initially sacrificing the mice with extensive bone lesions, tumor growth in bone was stabilized around day 25. The main reason for sacrifice at a later stage was breathing difficulties due to lung metastases, and in the Ra-223-treated mice only one mouse was sacrificed due to bone metastases. Ra-223 treatment was well-tolerated; no body weight loss was observed. In summary, radium-223 dichloride (Xofigo®) demonstrates moderate single agent in vivo efficacy in the intratibial MBT-2 murine bladder cancer model of osteolytic bone metastasis. Retaining a functional immune system in syngeneic mouse models is particularly relevant for the characterization of potential immune-stimulatory effects of Ra-223. The promising results obtained in this model warrant further investigation of Ra-223 in combination with immuno-oncological treatments like checkpoint inhibitors. Citation Format: Tiina E. Kähkönen, Mari I. Suominen, Jenni H. Mäki-Jouppila, Birgitta Sjöholm, Ilmari Ahonen, Dominik Mumberg, Karl Ziegelbauer, Jussi M. Halleen, Sanna-Maria Käkönen, Arne Scholz. Efficacy of single agent radium-223 in the syngeneic MBT-2 bladder cancer bone growth model in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3936.

Abstract 3002: Bone-protective curcumin circulates as a pro-drug conjugate that is activated in bone by β-glucuronidase

Abstract Curcumin (CURC), a turmeric-derived dietary polyphenol, prevents osteoclast formation and bone resorption in murine models of arthritis, post-menopausal osteoporosis, and bone metastatic breast cancer despite being rapidly conjugated upon ingestion in both rodents and humans to form curcumin-glucuronide (G-CURC). However, recent studies from our laboratory demonstrate that aglycone CURC is enriched in bone relative to the circulation. Studies were therefore undertaken to compare the anti-resorptive effects of aglycone CURC vs G-CURC and to elucidate mechanisms responsible for enrichment of aglycone CURC in bone, including clinically relevant influences of age, sex, and reproductive status. CURC dose-dependently inhibited RANKL-stimulated osteoclast formation in RAW264.7 cell cultures, while G-CURC was without effect. Likewise, CURC dose-dependently inhibited TGFβ-stimulated PTHrP secretion from MDA-MB-231 breast cancer cells, which readily form PTHrP-driven osteolytic bone metastases in vivo. In wild type (WT) C57BL/6J mice, heparanase (HPSE) and β-glucuronidase (GUSB) were the only enzymes with reported deglucuronidation activity expressed in bone (Western). However, only GUSB was able to recognize G-CURC as a substrate, deconjugating G-CURC to form CURC (LC/MS). Consistent with these findings, tissue-specific levels of CURC were highest in bone (vs. heart, muscle, or kidney) and proportional to tissue specific GUSB enzyme activity. To verify the role of GUSB in CURC bone enrichment, CURC metabolism and GUSB enzyme expression and activity were compared among mice with normal levels of GUSB (C57BL/6J) vs. partial (C3H/HeJ) or complete (mucopolysaccharidosis VII (mps/mps]) deficiencies in GUSB expression. As expected, partial (55% of WT) or complete deficiencies in GUSB expression significantly reduced CURC enrichment in bone. While GUSB can be positively regulated by pharmacologic doses of androgens, neither male sex nor ovariectomy (OVX) altered GUSB activity (per protein) in bone relative to intact females, although a small but statistically significant increase in free curcumin was demonstrated in males (17%) and OVX females (10%). Age did not significantly change the enrichment of CURC in bone of 4 vs 28-week mice. These findings suggest bio-inactive G-CURC acts as pro-drug that is converted to active CURC within bone, independent of sex, age or reproductive status, where it can inhibit the formation of bone resorbing osteoclasts or secretion of osteolytic PTHrP from breast cancer bone metastases. Citation Format: Andrew Kunihiro, Julia A. Brickey, jennifer B. Frye, Paula B. Luis, Claus Schneider, Janet L. Funk. Bone-protective curcumin circulates as a pro-drug conjugate that is activated in bone by β-glucuronidase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3002.

FOXF2 reprograms breast cancer cells into bone metastasis seeds

Bone metastases occur in most advanced breast cancer patients and cause serious skeletal-related complications. The mechanisms by which bone metastasis seeds develop in primary tumors and specifically colonize the bone remain to be elucidated. Here, we show that forkhead box F2 (FOXF2) functions as a master transcription factor for reprogramming cancer cells into an osteomimetic phenotype by pleiotropic transactivation of the BMP4/SMAD1 signaling pathway and bone-related genes that are expressed at early stages of bone differentiation. The epithelial-to-osteomimicry transition regulated by FOXF2 confers a tendency on cancer cells to metastasize to bone which leads to osteolytic bone lesions. The BMP antagonist Noggin significantly inhibits FOXF2-driven osteolytic bone metastasis of breast cancer cells. Thus, targeting the FOXF2-BMP/SMAD axis might be a promising therapeutic strategy to manage bone metastasis. The role of FOXF2 in transactivating bone-related genes implies a biological function of FOXF2 in regulating bone development and remodeling.

Lung Cancer Derived Circulating miR-21 Promotes Bone Metastasis by Activating Differentiation of Monocytes to Osteoclasts

Background: Osteoclastogenesis is a key process in osteolytic bone metastasis (BM). Previous studies indicated that miRNAs could regulate cancer progression and osteoclastogenesis. Our purpose was to investigate the roles of lung cancer cells-derived circulating miR-21 on osteoclastogenesis and its clinical significance in BM patients. Methods: The difference of miRNA expression in two lung cancer cell lines SBC-5 (with characteristic BM ability) and SBC-3 (without BM ability) were analyzed. Circulating miR-21 levels of lung cancer patients with or without BM were compared. The effects of conditioned media from lung cancer cell lines or patients' plasma with different miR-21 levels on osteoclastogenesis were investigated. The diagnostic performance of circulating miR-21 in BM patients was evaluated. Findings: We found that miR-21 expression was specifically higher in SBC-5 than that in SBC-3 cells. The supernatants of SBC-5 cells with higher level miR-21 promoted osteoclastogenesis. Moreover, we demonstrated that the circulating miR-21 level was significantly higher in BM patients than that in non-BM patients. The plasma from BM patients with higher level miR-21 could also promot osteoclastogenesis. Mechanistically, lung cancer cells-derived circulating miR-21 could be transferred into osteoclast precursor cells and promot osteoclastogenesis probably by inhibiting PTEN (Phosphatase and tensin homologue). Finally, we indecated that circulating miR-21 had a potential for the diagnosis of BM. Interpretation: Our findings suggested circulating miR-21 played important roles in BM of lung cancer and may service as a biomarker to diagnose BM in lung cancer patients. Funding: This work was supported by grants from the National Natural Science Foundation of China (No. 81572639, 81770875, 81370969), Department of Science and Technology of Sichuan Province (2018SZ0142), and Sichuan University (2018SCUH0093). Declaration of Interest: No potential conflicts of interest were disclosed. Ethical Approval: The study was approved by the hospital research ethics committee of West China Hospital of Sichuan University and conducted in accordance with the International Ethical Guidelines for Biomedical Research Involving Human Subjects. All patients included in this study had signed the informed consent form.

Paradoxical effects of JZL184, an inhibitor of monoacylglycerol lipase, on bone remodelling in healthy and cancer-bearing mice

BackgroundCancer-associated bone disease is a serious complication in bone sarcomas and metastatic carcinomas of breast and prostate origin. Monoacylglycerol lipase (MAGL) is an enzyme of the endocannabinoid system, and is responsible for the degradation of the most abundant endocannabinoid in bone, 2-arachidonoyl glycerol (2AG). MethodsThe effects of the verified MAGL inhibitor on bone remodelling were assessed in healthy mice and in mouse models of bone disease caused by prostate and breast cancers and osteosarcoma. FindingsJZL184 reduced osteolytic bone metastasis in mouse models of breast and prostate cancers, and inhibited skeletal tumour growth, metastasis and the formation of ectopic bone in models of osteosarcoma. Additionally, JZL184 suppressed cachexia and prolonged survival in mice injected with metastatic osteosarcoma and osteotropic cancer cells. Functional and histological analysis revealed that the osteoprotective action of JZL184 in cancer models is predominately due to inhibition of tumour growth and metastasis. In the absence of cancer, however, exposure to JZL184 exerts a paradoxical reduction of bone volume via an effect that is mediated by both Cnr1 and Cnr2 cannabinoid receptors. InterpretationMAGL inhibitors such as JZL184, or its novel analogues, may be of value in the treatment of bone disease caused by primary bone cancer and bone metastasis, however, activation of the skeletal endocannabinoid system may limit their usefulness as osteoprotective agents.

The RANKL-RANK Axis: A Bone to Thymus Round Trip.

The identification of Receptor activator of nuclear factor kappa B ligand (RANKL) and its cognate receptor Receptor activator of nuclear factor kappa B (RANK) during a search for novel tumor necrosis factor receptor (TNFR) superfamily members has dramatically changed the scenario of bone biology by providing the functional and biochemical proof that RANKL signaling via RANK is the master factor for osteoclastogenesis. In parallel, two independent studies reported the identification of mouse RANKL on activated T cells and of a ligand for osteoprotegerin on a murine bone marrow-derived stromal cell line. After these seminal findings, accumulating data indicated RANKL and RANK not only as essential players for the development and activation of osteoclasts, but also for the correct differentiation of medullary thymic epithelial cells (mTECs) that act as mediators of the central tolerance process by which self-reactive T cells are eliminated while regulatory T cells are generated. In light of the RANKL-RANK multi-task function, an antibody targeting this pathway, denosumab, is now commonly used in the therapy of bone loss diseases including chronic inflammatory bone disorders and osteolytic bone metastases; furthermore, preclinical data support the therapeutic application of denosumab in the framework of a broader spectrum of tumors. Here, we discuss advances in cellular and molecular mechanisms elicited by RANKL-RANK pathway in the bone and thymus, and the extent to which its inhibition or augmentation can be translated in the clinical arena.

Discovery of a natural small-molecule compound that suppresses tumor EMT, stemness and metastasis by inhibiting TGF\u03b2/BMP signaling in triple-negative breast cancer

BackgroundThe transforming growth factor β (TGFβ) and bone morphogenetic protein (BMP) signaling pathways are both constitutively activated in triple-negative breast cancer (TNBC). We are interested in isolating the naturally-derived small-molecule inhibitor that could simultaneously targeting TGFβ/BMP pathways and further studying its anti-proliferative/−metastatic effects as well as the underlying mechanisms in multiple tumor models.MethodsMultiple in vitro cell-based assays are used to examine the compound’s inhibitory efficacy on TNBC cell growth, stemness, epithelial-mesenchymal transition (EMT), invasion and migration by targeting TGFβ/BMP signaling pathways. Transgenic breast cancer mouse model (MMTV-PyMT), subcutaneous xenograft and bone metastasis models are used to examine ZL170’s effects on TNBC growth and metastasis potentials in vivo.ResultsZL170 dose-dependently inhibits cell proliferation, EMT, stemness, invasion and migration in vitro via specifically targeting canonical TGFβ/BMP-SMADs pathways in TNBC cells. The compound significantly hinders osteolytic bone metastasis and xenograft tumor growth without inflicting toxicity on vital organs of tumor-bearing nude mice. ZL170 strongly inhibits primary tumor growth and lung metastases in MMTV-PyMT transgenic mice. ZL170-treated tumors exhibit impaired TGFβ/BMP signaling pathways in both epithelial and stromal compartments, thereby creating a suppressive tumor microenvironment characterized by reduced extracellular matrix deposition and decreased infiltration of stromal cells.ConclusionsZL170 inhibits tumor EMT, stemness and metastasis and could be further developed as a potent anti-metastatic agent used in combination with cytotoxic drugs for treatment of TNBC and other advanced metastatic cancers.

CCN3/NOV as a functional driver and prognostic biomarker of prostate cancer bone metastasis.

182 Background: Prostate cancer commonly metastasizes to the bone, resulting in pathological fractures and poor prognosis. CCN3/NOV (Nephroblastoma overexpressed) has been implicated in promoting the formation of osteolytic prostate cancer (PC) bone metastases. The C-terminal domain of CCN3 binds growth factors, heparin sulfate proteoglycans, activates Notch signaling and promotes dimerization of CCN family members. We hypothesize that the CCN3 CT domain is required to promote osteolytic PC bone metastasis and that CCN3 represents a prognostic biomarker in primary PC tumors to predict recurrence to bone. Methods: CCN3WT and CCN3∆CT were overexpressed in LNCaP C4-2 cells. The role of CCN3 was assessed with in vitro proliferation, migration and invasion assays, and in vivo through intracardiac injection in male Nude mice (Nu/Nu). Ex vivo µCT scans were performed on bone specimens. CCN3 expression was assessed in two unique tissue microarrays (TMA) comprising over 1,500 primary prostate tumor using different anti-CCN3 antibodies with immunohistochemistry and immunohistofluorescnece, respectively. Results: While CCN3WT and CCN3∆CT had little effect in vitro on cell proliferation, migration or invasion, intracardiac injection of CCN3WT resulted in increased incidence of bone metastasis compared to empty vector control and CCN3∆CT. Ex vivo µCT revealed decreased bone mineral density in bones from mice injected with CCN3WT cells compared to control and CCN3∆CT expressing cells. In both TMAs studied, high CCN3 expression in tumor epithelium correlated with increased risk of biochemical relapse and bone metastasis at 5 years and 15 years post-resection, respectively. Conclusions: CCN3 requires its C-terminal domain for its bone metastatic function, and CCN3 is correlated with aggressive disease biology in prostate cancer. These findings point to CCN3 as a biomarker that can be useful to predict prostate cancer aggressiveness, while providing clarity on its role as a functional mediator of prostate cancer bone metastasis.

Sema4D expression and secretion are increased by HIF-1α and inhibit osteogenesis in bone metastases of lung cancer.

Most lung cancer bone metastasis are characterized by osteolytic destruction and osteoblastic activity is significantly decreased, suggesting that hypoxia may play a critical role in the process, but the underlying mechanisms remain unknown. Semaphorin 4D (Sema4D) is a recently discovered osteogenic inhibitory factor that is expressed at high levels in lung cancers. Here, CoCl2-induced hypoxia significantly enhanced the inhibitory effect of lung cancer cell conditioned media on osteoblast differentiation by inducing the expression and secretion of Sema4D in a HIF-1α- but not HIF-2α-dependent manner. Moreover, HIF-1α directly regulated Sema4D expression by binding to bases 1171 to 798 in the Sema4D promoter. Furthermore, hypoxia increased Sema4D secretion by upregulating a disintegrin and metalloproteinase 17 (ADAM17) expression in lung cancer in a HIF-1α-dependent manner. In bone metastasis samples from 49 patients with lung cancer, Sema4D and ADAM17 expression significantly correlated with HIF-1α expression and strongly correlated with a poor differentiation status and osteolytic bone destruction. These results provide the first evidence that HIF-1α-induced Sema4D expression and secretion play important roles in lung cancer osteolytic bone metastasis by inhibiting osteoblast differentiation, thereby providing potential strategies for the treatment of bone metastasis via targeting osteoblasts.