Sclerostin blockade promotes bone metastases of Wnt-responsive breast cancer cells.

The secreted protein sclerostin is primarily produced by osteocytes and suppresses osteoblast differentiation and function by inhibiting the canonical Wnt signaling pathway. Genetic and pharmacological inhibition of sclerostin has been shown to increase bone formation and an anti-sclerostin antibody has been clinically approved for the treatment of osteoporosis. Canonical Wnt signaling is also involved in the progression of several types of cancers including breast cancer. Here, we studied the effects of sclerostin inhibition on the development of bone metastases of breast cancer using mouse models. TOPFLASH assay and real-time PCR analysis of AXIN2, a target of canonical Wnt signaling, revealed that, among four cell lines tested, MDA-MB-231 human breast cancer cells responded highly to the canonical Wnt ligand Wnt3a, whereas other cell lines exhibited marginal responses. Consistent with these results, treatment with an anti-sclerostin antibody significantly increased the bone metastases of MDA-MB-231 but not those of other breast cancer cells. Immunohistochemical studies demonstrated that an anti-sclerostin antibody induced intracellular accumulation of ß-catenin in bone-colonized MDA-MB-231 cells. Suspension culture assays showed that Wnt3a accelerated the tumorsphere formation of MDA-MB-231 cells, whereas monolayer cell proliferation and migration were not affected. Furthermore, the numbers of osteoclasts and their precursor cells in bone metastases of MDA-MB-231 were significantly increased in mice treated with an anti-sclerostin antibody. These results collectively suggest that sclerostin blockade activates canonical Wnt signaling in ligand-responsive breast cancer cells metastasized to bone, thereby increasing bone metastases, likely to have been mediated at least in part by enhancing stem cell-like properties of cancer cells and osteoclastogenesis.

Altered immunolocalization of FGF23 in murine femora metastasized with human breast carcinoma MDA-MB-231 cells.

INTRODUCTION: After the onset of bone metastasis, tumor cells appear to modify surrounding microenvironments for their benefit, and particularly, the levels of circulating fibroblast growth factor (FGF) 23 in patients with tumors have been highlighted. MATERIALS AND METHODS: We have attempted to verify if human breast carcinoma MDA-MB-231 cells metastasized in the long bone of nu/nu mice would synthesize FGF23. Serum concentrations of calcium, phosphate (Pi) and FGF23 were measured in control nu/nu mice, bone-metastasized mice, and mice with mammary gland injected with MDA-MB-231 cells mimicking primary mammary tumors. RESULTS AND CONCLUSIONS: MDA-MB-231 cells revealed intense FGF23 reactivity in metastasized lesions, whereas MDA-MB-231 cells cultured in vitro or when injected into the mammary glands (without bone metastasis) showed weak FGF23 immunoreactivity. Although the bone-metastasized MDA-MB-231 cells abundantly synthesized FGF23, osteocytes adjacent to the FGF23-immunopositive tumors, unlike intact osteocytes, showed no FGF23. Despite significantly elevated serum FGF23 levels in bone-metastasized mice, there was no significant decrease in the serum Pi concentration when compared with the intact mice and mice with a mass of MDA-MB-231 cells in mammary glands. The metastasized femora showed increased expression and FGFR1 immunoreactivity in fibroblastic stromal cells, whereas femora of control mice showed no obvious FGFR1 immunoreactivity. Taken together, it seems likely that MDA-MB-231 cells synthesize FGF23 when metastasized to a bone, and thus affect FGFR1-positive stromal cells in the metastasized tumor nest in a paracrine manner.

Establishment and characterization of a C57BL/6 mouse model of bone metastasis of breast cancer.

Bone is one of the most common sites of metastasis in patients with advanced breast cancer; however, the mechanisms of bone metastasis remain to be fully elucidated. Animal models are essential research tools for investigating the mechanisms of diseases and drug actions. To date, there have only been a few reports in which C57BL/6 mice were used for the study of bone metastases of breast cancer. In the current study, we found that intracardiac inoculation of C57BL/6 mouse-derived parental E0771 breast cancer cells (E0771/Pa) frequently lead to bone metastases in C57BL/6 mice within 2 weeks. The bone-metastatic clone of E0771 (E0771/Bone) established by sequential in vivo selection demonstrated a higher bone-metastatic potential. Although there were no apparent differences in cell morphology or proliferation in monolayer cultures, E0771/Bone showed increased tumorsphere formation in suspension cultures and tumor formation in the orthotopic mammary fat pad in C57BL/6 mice compared with E0771/Pa. Furthermore, E0771/Bone expressed breast cancer stem-like cell surface markers CD24-/CD44+. These findings suggest that E0771/Bone possesses cancer stem-like properties. Quantitative PCR analysis revealed that mRNA expression of parathyroid hormone-related protein (PTHrP), the most common mediator of osteolytic bone metastases of breast cancer, was significantly upregulated in E0771/Bone. Thus, cancer stem-like properties and elevated PTHrP expression likely contribute to the enhanced metastatic potential of E0771/Bone. We believe that this new mouse model is a useful tool for in vivo studies of bone metastases of breast cancer, especially for those using genetically engineered mice with a C57BL/6 background.

Decreased sensory nerve excitation and bone pain associated with mouse Lewis lung cancer in TRPV1-deficient mice.

Bone pain is one of the most common and life-limiting complications of cancer metastasis to bone. Although the mechanism of bone pain still remains poorly understood, bone pain is evoked as a consequence of sensitization and excitation of sensory nerves (SNs) innervating bone by noxious stimuli produced in the microenvironment of bone metastases. We showed that bone is innervated by calcitonin gene-related protein (CGRP)+ SNs extending from dorsal root ganglia (DRG), the cell body of SNs, in mice. Mice intratibially injected with Lewis lung cancer (LLC) cells showed progressive bone pain evaluated by mechanical allodynia and flinching with increased CGRP+ SNs in bone and augmented SN excitation in DRG as indicated by elevated numbers of pERK- and pCREB-immunoreactive neurons. Immunohistochemical examination of LLC-injected bone revealed that the tumor microenvironment is acidic. Bafilomycin A1, a selective inhibitor of H+ secretion from vacuolar proton pump, significantly alleviated bone pain, indicating that the acidic microenvironment contributes to bone pain. We then determined whether the transient receptor potential vanilloid 1 (TRPV1), a major acid-sensing nociceptor predominantly expressed on SNs, plays a role in bone pain by intratibially injecting LLC cells in TRPV1-deficient mice. Bone pain and SN excitation in the DRG and spinal dorsal horn were significantly decreased in TRPV1 -/- mice compared with wild-type mice. Our results suggest that TRPV1 activation on SNs innervating bone by the acidic cancer microenvironment in bone contributes to SN activation and bone pain. Targeting acid-activated TRPV1 is a potential therapeutic approach to cancer-induced bone pain.

Expression and localization of CRAMP in rat tooth germ and during reparative dentin formation.

OBJECTIVES: Cathelicidin-related antimicrobial peptide (CRAMP) is an antimicrobial peptide in mice and rats homologous to LL-37 in humans. In addition to its antibacterial activity, CRAMP has various physiological functions by binding to formyl peptide receptor 2 (FPR2). However, the role of these peptides in teeth is unknown. Therefore, we investigated the role of CRAMP and FPR2 in tooth development, reparative dentin formation, and defense response. MATERIAL AND METHODS: First, we examined the localization of CRAMP and FPR2 during tooth development by immunohistochemical analysis. Next, we investigated the localization of CRAMP, FPR2, and CD68-positive macrophages by immunohistochemical analysis during pulp inflammation and reparative dentin formation after cavity preparation. Finally, we analyzed the effect of lipopolysaccharide (LPS) on the expression of CRAMP and FPR2 in dental pulp cells by real-time reverse transcription PCR. RESULTS: At the late bell stage in tooth development, CRAMP was detected in odontoblasts, and FPR2 was observed in the sub-odontoblastic layer. In mature teeth, CRAMP was not detected, but FPR2 continued to be localized in the sub-odontoblastic layer. After cavity preparation, CRAMP-positive cells and macrophages were found in dental pulp tissues below the cavity at an early stage of repair. At subsequent stages of reparative dentin formation, CRAMP was observed in odontoblast-like cells that contacted reparative dentin. FPR2 immunoreactivity was also detected in odontoblast-like cells and neighboring cells. LPS stimulated the expression of CRAMP mRNA in dental pulp cells in vitro. CONCLUSIONS: Localization of CRAMP and its receptor FPR2-positive cells were observed during physiological and reparative dentin formation. CLINICAL RELEVANCE: CRAMP/LL-37 has a possibility that induce reparative dentin formation.

Hypoxic Microenvironment and Metastatic Bone Disease.

Hypoxia is a common feature of solid tumors and is associated with an increased risk of metastasis and a poor prognosis. Recent imaging techniques revealed that bone marrow contains a quite hypoxic microenvironment. Low oxygen levels activate hypoxia signaling pathways such as hypoxia-inducible factors, which play critical roles in the key stages of metastatic dissemination including angiogenesis, epithelial-mesenchymal transition, invasion, maintenance of cancer stem cells, tumor cell dormancy, release of extracellular vesicles, and generation of pre-metastatic niches. Hypoxia also affects bone cells, such as osteoblasts and osteoclasts, and immune cells, which also act to support the development and progression of bone metastases. Paradoxically, hypoxia and related signaling molecules are recognized as high-priority therapeutic targets and many candidate drugs are currently under preclinical and clinical investigation. The present review focuses on our current knowledge of the potential roles of hypoxia in cancer metastasis to bone by considering the interaction between metastatic cancer cells and the bone microenvironment. Current therapeutic approaches targeting hypoxia are also described.

EpCAM expression in breast cancer cells is associated with enhanced bone metastasis formation.

Epithelial cell adhesion molecule (EpCAM) has been implicated in multiple cellular functions including cell adhesion. EpCAM has also recently been identified as a marker for cancer stem cells (CSCs). Here, we examined the roles of EpCAM in the development of bone metastasis of breast cancer by using well-characterized animal models. Morphological and real-time reverse transcriptase-polymerase chain reaction data showed that the EpCAM-negative and -positive (EpCAM(neg) and EpCAM(pos) ) cell populations isolated from breast cancer cell lines exhibited mesenchymal and epithelial phenotypes, respectively. Flow cytometric analysis revealed that EpCAM(pos) , but not EpCAM(neg) , cells possessed self-renewal and differentiation potentials. Tumorsphere formation in suspension cultures and tumorigenicity in the orthotopic mammary fat pad of mice were significantly greater in EpCAM(pos) cells than in EpCAM(neg) cells. The development of bone metastases induced by an intracardiac injection was markedly increased in mice inoculated with EpCAM(pos) cells. Furthermore, intracardiac inoculations of parental cells demonstrated that the EpCAM(pos) population in cancer cells that colonized in bone was significantly higher than that in parental cells. However, stable transduction of EpCAM into EpCAM(neg) cells failed to reproduce the phenotypes of EpCAM(pos) cells. These results suggest that the expression of EpCAM in breast cancer cells is associated with CSC-like phenotypes, which contribute to the promotion of bone metastases by enhancing tumorigenicity. Our results also support the possibility that the epithelial phenotypes of EpCAM-expressing cells confer advantageous properties for the development of bone metastases, at least after entering the circulation, while EpCAM is likely not solely responsible for the phenotypes of EpCAM(pos) cells.

Identification of three exercise-induced mortality risk factors in patients with COPD.

The survival rate of chronic obstructive pulmonary disease (COPD) patients with severely reduced exercise capacity is extremely low. We recently identified three life-threatening pathophysiological conditions during cardiopulmonary exercise testing (CPET): (1) exercise-induced hypoxemia, (2) sympathetic overactivity, and (3) progressive respiratory acidosis at low-intensity exercise. The present prospective observation study aimed to determine whether these parameters constitute risk factors of mortality in moderate-to-very severe COPD. Ninety-six COPD patients were followed-up, monthly, for >3 years. Subsequently, spirometry and CPET were performed to examine parameters of exercise-induced hypoxemia ([PaO2 slope, mmHg/L · min(-1)] = Decrease in PaO2/ΔV˙ O2 (Difference in ΔV˙ O2 between at rest and at peak exercise)), progression of acidosis ([ΔpH/ΔV˙ O2,/L · min(-1)] = Decrease in pH/ΔV˙ O2), and sympathetic overactivity ([Δnorepinephrine (NE)/ΔV˙ O2, ng/mL/L · min(-1)] = Increase in NE/ΔV˙ O2). Univariate analysis revealed a significant association between the three conditions with increased mortality. Kaplan-Meier analysis showed that the quartile combining the steepest PaO2 slope (≤-55 mmHg/ΔV˙ O2 [L/min]), steepest decrease in arterial blood pH (≤ -1.72/ΔV˙ O2 [L/min]), and most rapid increase in plasma NE level (≥ 5.2 ng/VO2 [L/min]) during incremental exercise was associated with higher all-cause mortality. These conditions showed cumulative effects on COPD patients' survival. Multivariate analyses revealed that these three life-threatening factors are also independent predictors of mortality based on age, heart rate and PaO2 at rest, body mass index, and forced expiratory volume in 1 s. Thus, these new exercise-induced mortality risk factors may lead to more efficient pulmonary rehabilitation programs for COPD patients based on patient-specific exercise-induced pathophysiological profiles.

[Molecular mechanisms of bone cancer pain].

Bone pain is one of the most frequent complications of bone metastasis, leading to a marked reduction in the quality of life of patients. The mechanisms of bone cancer pain are highly complicated ; however, noxious stimuli produced by cancer tissues and cancer-induced nerve injury are considered to be the major causes. Recent studies also suggest the possible involvement of acidic microenvironments created by cancer tissues and osteoclasts in cancer-induced bone pain. Understanding the molecular events may lead to the design of novel mechanism-based approaches for the management of bone pain associated with cancer metastasis.

Immunotherapy targeting PD­1/PD­L1: A potential approach for the treatment of cancer bone metastases (Review).

Immune checkpoint molecules, such as programmed cell death 1 (PD­1) and programmed cell death ligand 1 (PD­L1), have a critical role in regulating immune responses, including in tumor tissues. Monoclonal antibodies against these molecules, known as immune checkpoint inhibitors (ICIs), have been shown to be effective against a variety of cancers; however, significant patient populations are resistant to such treatment. Clinical studies to date have shown that ICIs are less effective in cancer patients with bone metastases. The effect of anti­PD­1/PD­L1 antibodies on bone metastases, as assessed by the bone metastasis­specific response classification criteria, was relatively low. In addition, the presence of bone metastases showed a trend toward worse progression­free survival and overall survival in cancer patients treated with ICIs. To improve the efficacy of ICIs in bone metastases, several combination therapies are under investigation and certain studies have reported better responses. The present review summarizes the current understanding of the effects of anti­PD­1/PD­L1 antibodies on bone metastases based on the reported clinical and preclinical studies.

Primary tumor-induced immunity suppresses bone metastases of breast cancer in syngeneic immunocompetent mouse models.

The immune system plays a crucial role in cancer development and progression. More than a century ago, mouse models showed that primary tumors suppressed the growth of newly implanted secondary tumors. This phenomenon, in which tumor-primed T cells mediate the rejection of tumor growth at a distant site, is known as concomitant tumor immunity. Here, we investigated the role of concomitant immunity in the development of breast cancer bone metastases using newly developed syngeneic immunocompetent mouse models. The presence of primary breast tumors developed by tumor cell injection into the mammary fat pads (MFPs) significantly reduced bone metastases of mouse breast cancer 4T1 and EMT6 cells induced by cell injection through the caudal artery (CA). Similar results were obtained when primary tumors were surgically resected prior to CA injection of tumor cells. In contrast, no inhibition was found when MFP and CA injections were performed using different cell combinations. Immunohistochemical studies revealed that the number of CD8+ T cells in bone metastases of 4T1 and EMT6 cells was significantly increased in the presence of primary tumors. The primary tumor-induced inhibition of bone metastases was not reproduced in T cell-deficient athymic nude mice. Furthermore, depletion of CD8+ T cells using an anti-CD8α antibody also abolished the primary tumor-induced inhibition of bone metastases. Taken together, these results suggest that immune cell priming by orthotopic breast tumors inhibits the development of breast cancer bone metastases, which is predominantly mediated by CD8+ cytotoxic T lymphocytes.

De novo steroidogenesis in tumor cells drives bone metastasis and osteoclastogenesis.

Osteoclasts play a central role in cancer-cell-induced osteolysis, but the molecular mechanisms of osteoclast activation during bone metastasis formation are incompletely understood. By performing RNA sequencing on a mouse breast carcinoma cell line with higher bone-metastatic potential, here we identify the enzyme CYP11A1 strongly upregulated in osteotropic tumor cells. Genetic deletion of Cyp11a1 in tumor cells leads to a decreased number of bone metastases but does not alter primary tumor growth and lung metastasis formation in mice. The product of CYP11A1 activity, pregnenolone, increases the number and function of mouse and human osteoclasts in vitro but does not alter osteoclast-specific gene expression. Instead, tumor-derived pregnenolone strongly enhances the fusion of pre-osteoclasts via prolyl 4-hydroxylase subunit beta (P4HB), identified as a potential interaction partner of pregnenolone. Taken together, our results demonstrate that Cyp11a1-expressing tumor cells produce pregnenolone, which is capable of promoting bone metastasis formation and osteoclast development via P4HB.

Localization of SUMOylation factors and Osterix in odontoblast lineage cells during dentin formation and regeneration.

Small ubiquitin-related modifier (SUMO) conjugation (SUMOylation) is a post-translational modification involved in various cellular processes including the regulation of transcription factors. In this study, to analyze the involvement of SUMOylation in odontoblast differentiation, we examined the immunohistochemical localization of SUMO-1, SUMO-2/3, and Osterix during rat tooth development. At the bud and cap stages, localization of SUMOs and Osterix was hardly detected in the dental mesenchyme. At the bell stage, odontoblasts just beginning dentin matrix secretion and preodontoblasts near these odontoblasts showed intense immunoreactivity for these molecules. However, after the root-formation stage, these immunoreactivities in the odontoblasts decreased in intensity. Next, to examine whether the SUMOylation participates in dentin regeneration, we evaluated the distribution of SUMOs and Osterix in the dental pulp after cavity preparation. In the coronal pulp chamber of an untreated rat molar, odontoblasts and pulp cells showed no immunoreactivity. At 4 days after cavity preparation, positive cells for SUMOs and Osterix appeared on the surface of the dentin beneath the cavity. Odontoblast-like cells forming reparative dentin were immunopositive for SUMOs and Osterix at 1 week, whereas these immunoreactivities disappeared after 8 weeks. Additionally, we further analyzed the capacity of SUMO-1 to bind Osterix by performing an immunoprecipitation assay using C2C12 cells, and showed that Osterix could undergo SUMOylation. These results suggest that SUMOylation might regulate the transcriptional activity of Osterix in odontoblast lineage cells, and thus play important roles in odontoblast differentiation and regeneration.

Effects of ghrelin treatment on exercise capacity in underweight COPD patients: a substudy of a multicenter, randomized, double-blind, placebo-controlled trial of ghrelin treatment.

BACKGROUND: The aim of this substudy of the ghrelin treatment, multicenter, randomized, double-blind, placebo-controlled trial was to investigate the effects of ghrelin administration on exercise capacity and the underlying mechanisms in underweight patients with chronic obstructive pulmonary disease (COPD) using cardiopulmonary exercise testing. METHODS: Twenty underweight COPD patients were randomized to pulmonary rehabilitation with intravenous ghrelin (2 µg/kg, n = 10) or placebo (n = 10) twice daily for 3 weeks in a double-blind fashion. The primary outcome was changes in peak oxygen uptake V•o2. Secondary outcomes included changes in exertional cardio-respiratory functions: O2-pulse, physiologic dead space/tidal volume-ratio (VD/VT), ventilatory equivalent for oxygen V•E/V•o2, and ventilatory equivalent for carbon dioxide V•E/V•co2. RESULTS: With incremental exercise, at peak exercise, there was a significant difference in the mean difference (ghrelin minus placebo), i.e., treatment effect in: i) peak V•o2 (1.2 mL/kg/min, 95% CI: 0.2-2.3 mL/kg/min, between-group p = 0.025); ii) V•E/V•o2 (-4.2, 95% CI: -7.9 to -0.5, between-group p = 0.030); iii) V•E/V•co2 (-4.1, 95% CI: -8.2 to -0.1, between-group p = 0.045); iv) VD/VT (-0.04, 95% CI: -0.08 to -0.00, between-group p = 0.041); and v) O2-pulse (0.7 mL/beat, 95% CI: 0.3 to 1.2 mL/beat, between-group p = 0.003). Additionally, repeated-measures analysis of variance (ANOVA) indicated a significant time-course effect of ghrelin versus placebo in the peak V•o2 (p = 0.025). CONCLUSION: Ghrelin administration was associated with improved exertional capacity and improvements in ventilatory-cardiac parameters. TRIAL REGISTRATION: UMIN (University Hospital Medical Information Network in Japan) C000000061.

Thy-1-positive cells in the subodontoblastic layer possess high potential to differentiate into hard tissue-forming cells.

The cells of the subodontoblastic cell-rich layer in dental pulp are speculated to contain odontoblast progenitor cells because of their positional relationship with odontoblasts as well as their high alkaline phosphatase (ALP) activity. However, it has yet to be determined whether these cells have the ability to differentiate into odontoblastic cells. In the present study, we firstly found that the majority of cells in the subodontoblastic layer expressed Thy-1, a cell-surface marker of stem and progenitor cells. Then, we evaluated the capacity of Thy-1 high- and low-expressing (Thy-1(high) and Thy-1(low)) cells separated from rat dental pulp cells by use of a fluorescence-activated cell sorter to differentiate into hard tissue-forming cells in vitro and in vivo. Following stimulation with bone morphogenetic protein-2, Thy-1(high) cells in vitro showed accelerated induction of ALP activity and formation of alizarin red-positive mineralized matrix compared with Thy-1(low) cells. Furthermore, subcutaneous implantation of Thy-1(high) cells efficiently induced the formation of bone-like matrix. These results collectively suggest that Thy-1-positive dental pulp cells localized in the subodontoblastic layer had the ability to differentiate into hard tissue-forming cells, and thus these cells may serve as a source of odontoblastic cells.

Effects of oxygen on exertional dyspnoea and exercise performance in patients with chronic obstructive pulmonary disease.

BACKGROUND AND OBJECTIVE: The results of studies on the oxygen response in patients with COPD should provide important clues to the pathophysiology of exertional dyspnoea. We investigated the exercise responses to hyperoxia in relation to dyspnoea profile, as well as cardiopulmonary, acidotic and sympathetic parameters in 35 patients with stable COPD (mean FEV(1) 46% predicted). METHODS: This was a single-blind trial, in which patients breathed 24% O(2) or compressed air (CA) in random order during two incremental cycle exercise tests. RESULTS: PaO(2) and PaCO(2) were higher (P < 0.0001 and P < 0.05, respectively) at each exercise point while patients were breathing 24% O(2) compared with CA. At a standardized time point near peak exercise, use of O(2) resulted in reduced plasma lactate and plasma noradrenaline concentrations (P < 0.01). Peak minute ventilation/indirect maximum voluntary ventilation was similar while breathing 24% O(2) and CA. At peak exercise, the dyspnoea score, pH and plasma noradrenaline concentrations were similar while breathing 24% O(2) and CA. The dyspnoea-ratio (%) of Δoxygen uptake (peak minus resting oxygen uptake) curve reached a break point that occurred at a similar exercise point while breathing 24% O(2) or CA. CONCLUSIONS: Regardless of whether they breathed CA or 24% O(2) , patients with COPD did not develop ventilatory compensation for exertional acidosis, and the pH values measured were similar. Hyperoxia during a standardized exercise protocol did not alter the pattern of exertional dyspnoea in these patients, compared with breathing CA, although hyperoxia resulted in miscellaneous effects.

Opposing Effects of Granulocyte Colony-Stimulating Factor on the Initiation and Progression of Breast Cancer Bone Metastases.

Granulocyte colony stimulating factor (G-CSF), an essential cytokine regulating granulopoiesis, is expressed in a substantial proportion of breast cancers, and it has been implicated in cancer progression. Here, we examined effects of G-CSF on the development of bone metastases of breast cancer using immunocompetent mouse models. The expression of CXC chemokine ligand 12 (CXCL12) in bone marrow stromal cells, which plays a critical role in the maintenance of hematopoietic stem cells and also in cancer cell homing to bone, was markedly decreased in mice treated with G-CSF. Flow cytometric analysis revealed that pretreatment of mice with G-CSF reduced the number of bone-homing cancer cells. G-CSF also increased the population of myeloid-derived suppressor cells (MDSCs) in bone marrow. Depletion of MDSCs using anti-Gr-1 antibody treatment significantly decreased the metastatic tumor burden in bone. The overall effects of G-CSF on bone metastases were finally examined using two different treatment protocols. When mice were treated with G-CSF prior to the tumor cell inoculation, G-CSF did not change bone metastatic-tumor burden. In contrast, when G-CSF treatment was started after the tumor cells had homed to bone, G-CSF significantly accelerated bone metastases formation. These results suggest that G-CSF suppressed cancer cell homing to bone by downregulating CXCL12 expression in bone marrow stromal cells, whereas G-CSF stimulated the progression of bone metastases at least in part by MDSC-mediated mechanisms. IMPLICATIONS: G-CSF had opposing effects on the initiation and progression of bone metastases of breast cancer and the balance may regulate the metastatic tumor burden.

Administration of the bisphosphonate zoledronic acid during tooth development inhibits tooth eruption and formation and induces dental abnormalities in rats.

Bisphosphonates (BPs) are potent inhibitors of osteoclastic bone resorption and widely used for the treatment of osteoporosis and metastatic bone diseases. Recently, BPs have also been shown to benefit children with primary and secondary osteoporosis, including osteogenesis imperfecta; however, their long-term safety has not been established yet. Clinical and experimental studies have demonstrated that BPs delay or inhibit tooth eruption. The failure of tooth eruption causes several dental abnormalities. In this study, to determine the effects of BPs on tooth formation, the BP zoledronic acid (ZOL) was injected into 7- and 14-day-old rats, and the development of the mandibular teeth was examined. X-ray analysis demonstrated that ZOL inhibited the eruption of both incisors and molars and their formation, especially in the molar roots. Histological examination showed that, in ZOL-treated animals, alveolar bone remained unresorbed around tooth crowns, which injured ameloblasts and enamel matrix, leading to defects of the enamel. Furthermore, haphazard proliferation of odontogenic epithelium and mesenchyme associated with primitive tooth structures, which resembles human odontomas, was induced at the basal end of incisors but not around the molars. Tooth ankylosis to alveolar bone was occasionally observed in molars. These results suggest that administration of BPs during tooth development has the potential to inhibit tooth eruption and formation and to induce several types of dental abnormalities, which may be attributed to the altered osteoclastic activities.

Zoledronic acid delays wound healing of the tooth extraction socket, inhibits oral epithelial cell migration, and promotes proliferation and adhesion to hydroxyapatite of oral bacteria, without causing osteonecrosis of the jaw, in mice.

Nitrogen-containing bisphosphonates such as zoledronic acid (ZOL) and pamidronate have been widely and successfully used for the treatment of cancer patients with bone metastases and/or hypercalcemia. Accumulating recent reports have shown that cancer patients who have received these bisphosphonates occasionally manifest bisphosphonate-related osteonecrosis of the jaw (BRONJ) following dental treatments, including tooth extraction. However, little is known about the pathogenesis of BRONJ to date. Here, to understand the underlying pathogenesis of BRONJ, we examined the effects of ZOL on wound healing of the tooth extraction socket using a mouse tooth extraction model. Histomorphometrical analysis revealed that the amount of new bone and the numbers of blood vessels in the socket were significantly decreased in ZOL-treated mice compared to control mice. Consistent with these results, ZOL significantly inhibited angiogenesis induced by vascular endothelial growth factor in vivo and the proliferation of endothelial cells in culture in a dose-dependent manner. In contrast, etidronate, a non-nitrogen-containing bisphosphonate, showed no effects on osteogenesis and angiogenesis in the socket. ZOL also suppressed the migration of oral epithelial cells, which is a crucial step for tooth socket closure. In addition, ZOL promoted the adherence of Streptococcus mutans to hydroxyapatite and the proliferation of oral bacteria obtained from healthy individuals, suggesting that ZOL may increase the bacterial infection. In conclusion, our data suggest that ZOL delays wound healing of the tooth extraction socket by inhibiting osteogenesis and angiogenesis. Our data also suggest that ZOL alters oral bacterial behaviors. These actions of ZOL may be relevant to the pathogenesis of BRONJ.

[Susceptibility to rifabutin and novel fluoroquinolones in Mycobacterium avium complex isolates from patients with sputum culture-positive pulmonary disease who are undergoing standard chemotherapy].

We investigated the susceptibility to conventional and newer antimycobacterial agents including rifabutin (RBT) and novel fluoroquinolones (NFQs) among 48 clinical Mycobacterium avium complex (MAC) isolates from patients with sputum culture-positive MAC disease who were undergoing standard chemotherapy. RBT and NFQs were superior to conventional agents because of higher rates of susceptibility and lower minimum inhibitory concentration. NFQs showed cross-resistance among quinolones. In contrast, RBT did not show cross-resistance to RFP. Most clarithromycin-resistant or rifampicin-resistant cases were susceptible to RBT and NFQs. In conclusion, RBT and NFQs possess good in vitro antimicrobial activity among clinical isolates of culture-positive pulmonary MAC disease, which suggests that a combination of such microbiologically active agents may improve clinical effectiveness more than standard chemotherapy regimens.