Genetic depletion and pharmacological targeting of αv integrin in breast cancer cells impairs metastasis in zebrafish and mouse xenograft models.

INTRODUCTION: Increased expression of αv integrins is frequently associated with tumor cell adhesion, migration, invasion and metastasis, and correlates with poor prognosis in breast cancer. However, the mechanism by which αv integrins can enhance breast cancer progression is still largely unclear. The effects of therapeutic targeting of αv integrins in breast cancer also have yet to be investigated. METHODS: We knocked down αv integrin in MDA-MB-231 and MCF10A-M4 breast cancer cells, or treated these cells with the αv antagonist GLPG0187. The effects of αv integrin depletion on mesenchymal markers, transforming growth factor-ß (TGF-ß)/Smad signaling and TGF-ß-induced target gene expression were analyzed in MDA-MB-231 cells by RNA analysis or Western blotting. The function of αv integrin on breast cancer cell migration was investigated by transwell assay in vitro, and its effect on breast cancer progression was assessed by both zebrafish and mouse xenografts in vivo. In the mouse model, GLPG0187 was administered separately, or in combination with the standard-of-care anti-resorptive agent zoledronate and the chemotherapeutic drug paclitaxel, to study the effects of combinational treatments on breast cancer metastasis. RESULTS: Genetic interference and pharmacological targeting of αv integrin with GLPG0187 in different breast cancer cell lines inhibited invasion and metastasis in the zebrafish or mouse xenograft model. Depletion of αv integrin in MDA-MB-231 cells inhibited the expression of mesenchymal markers and the TGF-ß/Smad response. TGF-ß induced αv integrin mRNA expression and αv integrin was required for TGF-ß-induced breast cancer cell migration. Moreover, treatment of MDA-MB-231 cells with non-peptide RGD antagonist GLPG0187 decreased TGF-ß signaling. In the mouse xenografts GLPG0187 inhibited the progression of bone metastasis. Maximum efficacy of inhibition of bone metastasis was achieved when GLPG0187 was combined with the standard-of-care metastatic breast cancer treatments. CONCLUSION: These findings show that αv integrin is required for efficient TGF-ß/Smad signaling and TGF-ß-induced breast cancer cell migration, and for maintaining a mesenchymal phenotype of the breast cancer cells. Our results also provide evidence that targeting αv integrin could be an effective therapeutic approach for treatment of breast cancer tumors and/or metastases that overexpress αv integrin.

Prostate cancer cells home to bone using a novel in vivo model: modulation by the integrin antagonist GLPG0187.

Micrometastasis is a barrier to the development of effective cancer therapies for prostate cancer metastasis to bone. The mechanisms remain incompletely characterised, primarily due to an inability to adequately monitor the initial metastatic events in vivo. This study aimed to establish a new model, allowing the tracking of prostate cancer cells homing to bone, and furthermore, to evaluate the response of this approach to therapeutic modulation, using the integrin antagonist GLPG0187. A single murine metatarsal was engrafted into a dorsal skinfold chamber implanted on a SCID mouse. Fluorescently-labeled human prostate (PC3-GFP) or oral (SCC4-GFP) cancer cells were administered via intracardiac (i.c) injection, with simultaneous daily GLPG0187 or vehicle-control treatment (i.p. 100 mg/kg/day) for the experimental duration. Metatarsal recordings were taken every 48 h for up to 4 weeks. Tissue was harvested and processed for microCT, multiphoton analysis, histology and immunohistochemistry. Cell viability, proliferation and migration in vitro were also quantified following treatment with GLPG0187. Metatarsals rapidly revascularised by inosculation with the host vasculature (day 5-7). PC3-GFP cells adhered to the microvascular endothelium and/or metatarsal matrix 3 days after administration, with adhesion maintained for the experimental duration. GLPG0187 treatment significantly (p < 0.05) reduced PC3 cell number within the metatarsal in vivo and reduced migration (p < 0.05) and proliferation (p < 0.05) but not cell viability in vitro. This new model allows evaluation of the early events of tumour-cell homing and localisation to the bone microenvironment, in addition to determining responses to therapeutic interventions.

Preclinical characterization of GLPG0634, a selective inhibitor of JAK1, for the treatment of inflammatory diseases.

The JAKs receive continued interest as therapeutic targets for autoimmune, inflammatory, and oncological diseases. JAKs play critical roles in the development and biology of the hematopoietic system, as evidenced by mouse and human genetics. JAK1 is critical for the signal transduction of many type I and type II inflammatory cytokine receptors. In a search for JAK small molecule inhibitors, GLPG0634 was identified as a lead compound belonging to a novel class of JAK inhibitors. It displayed a JAK1/JAK2 inhibitor profile in biochemical assays, but subsequent studies in cellular and whole blood assays revealed a selectivity of ∼30-fold for JAK1- over JAK2-dependent signaling. GLPG0634 dose-dependently inhibited Th1 and Th2 differentiation and to a lesser extent the differentiation of Th17 cells in vitro. GLPG0634 was well exposed in rodents upon oral dosing, and exposure levels correlated with repression of Mx2 expression in leukocytes. Oral dosing of GLPG0634 in a therapeutic set-up in a collagen-induced arthritis model in rodents resulted in a significant dose-dependent reduction of the disease progression. Paw swelling, bone and cartilage degradation, and levels of inflammatory cytokines were reduced by GLPG0634 treatment. Efficacy of GLPG0634 in the collagen-induced arthritis models was comparable to the results obtained with etanercept. In conclusion, the JAK1 selective inhibitor GLPG0634 is a promising novel therapeutic with potential for oral treatment of rheumatoid arthritis and possibly other immune-inflammatory diseases.

Characterization of GLPG0492, a selective androgen receptor modulator, in a mouse model of hindlimb immobilization.

BACKGROUND: Muscle wasting is a hallmark of many chronic conditions but also of aging and results in a progressive functional decline leading ultimately to disability. Androgens, such as testosterone were proposed as therapy to counteract muscle atrophy. However, this treatment is associated with potential cardiovascular and prostate cancer risks and therefore not acceptable for long-term treatment. Selective Androgen receptor modulators (SARM) are androgen receptor ligands that induce muscle anabolism while having reduced effects in reproductive tissues. Therefore, they represent an alternative to testosterone therapy. Our objective was to demonstrate the activity of SARM molecule (GLPG0492) on a immobilization muscle atrophy mouse model as compared to testosterone propionate (TP) and to identify putative biomarkers in the plasma compartment that might be related to muscle function and potentially translated into the clinical space. METHODS: GLPG0492, a non-steroidal SARM, was evaluated and compared to TP in a mouse model of hindlimb immobilization. RESULTS: GLPG0492 treatment partially prevents immobilization-induced muscle atrophy with a trend to promote muscle fiber hypertrophy in a dose-dependent manner. Interestingly, GLPG0492 was found as efficacious as TP at reducing muscle loss while sparing reproductive tissues. Furthermore, gene expression studies performed on tibialis samples revealed that both GLPG0492 and TP were slowing down muscle loss by negatively interfering with major signaling pathways controlling muscle mass homeostasis. Finally, metabolomic profiling experiments using 1H-NMR led to the identification of a plasma GLPG0492 signature linked to the modulation of cellular bioenergetic processes. CONCLUSIONS: Taken together, these results unveil the potential of GLPG0492, a non-steroidal SARM, as treatment for, at least, musculo-skeletal atrophy consecutive to coma, paralysis, or limb immobilization.

IRAK4 inhibition dampens pathogenic processes driving inflammatory skin diseases.

Innate immunity not only shapes the way epithelial barriers interpret environmental cues but also drives adaptive responses. Therefore, modulators of innate immune responses are expected to have high therapeutic potential across immune-mediated inflammatory diseases. IRAK4 is a kinase that integrates signaling downstream of receptors acting at the interface between innate and adaptive immune responses, such as Toll-like receptors (TLRs), interleukin-1R (IL-1R), and IL-18R. Because effects of IRAK4 inhibition are stimulus, cell type, and species dependent, the evaluation of the therapeutic potential of IRAK4 inhibitors requires a highly translational approach. Here, we profiled a selective IRAK4 inhibitor, GLPG2534, in an extensive panel of models of inflammatory skin diseases, translationally expanding evidence from in vitro to in vivo and from mouse to human. In vitro, IRAK4 inhibition resulted in substantial inhibition of TLR and IL-1 responses in dendritic cells, keratinocytes, granulocytes, and T cells but only weakly affected dermal fibroblast responses. Furthermore, disease activity in murine models of skin inflammation (IL-23-, IL-33-, imiquimod-, and MC903-induced) was markedly dampened by IRAK4 inhibition. Last, inhibiting IRAK4 reversed pathogenic molecular signatures in human lesional psoriasis and atopic dermatitis biopsies. Over the variety of models used, IRAK4 inhibition consistently affected central mediators of psoriasis (IL-17A) and atopic dermatitis (IL-4 and IL-13). Overall, our data highlight IRAK4 as a central player in skin inflammatory processes and demonstrate the potential of IRAK4 inhibition as a therapeutic strategy in chronic inflammatory skin diseases.

Discovery of the S1P2 Antagonist GLPG2938 (1-[2-Ethoxy-6-(trifluoromethyl)-4-pyridyl]-3-[[5-methyl-6-[1-methyl-3-(trifluoromethyl)pyrazol-4-yl]pyridazin-3-yl]methyl]urea), a Preclinical Candidate for the Treatment of Idiopathic Pulmonary Fibrosis.

Mounting evidence from the literature suggests that blocking S1P2 receptor (S1PR2) signaling could be effective for the treatment of idiopathic pulmonary fibrosis (IPF). However, only a few antagonists have been so far disclosed. A chemical enablement strategy led to the discovery of a pyridine series with good antagonist activity. A pyridazine series with improved lipophilic efficiency and with no CYP inhibition liability was identified by scaffold hopping. Further optimization led to the discovery of 40 (GLPG2938), a compound with exquisite potency on a phenotypic IL8 release assay, good pharmacokinetics, and good activity in a bleomycin-induced model of pulmonary fibrosis.

The Medium-Chain Fatty Acid Receptor GPR84 Mediates Myeloid Cell Infiltration Promoting Steatohepatitis and Fibrosis.

Medium-chain fatty acids (MCFAs) have been associated with anti-steatotic effects in hepatocytes. Expression of the MCFA receptor GPR84 (G protein-coupled receptor 84) is induced in immune cells under inflammatory conditions and can promote fibrogenesis. We aimed at deciphering the role of GPR84 in the pathogenesis of non-alcoholic steatohepatitis (NASH), exploring its potential as a therapeutic target. GPR84 expression is upregulated in liver from patients with non-alcoholic fatty liver disease (NAFLD), correlating with the histological degree of inflammation and fibrosis. In mouse and human, activated monocytes and neutrophils upregulate GPR84 expression. Chemotaxis of these myeloid cells by GPR84 stimulation is inhibited by two novel, small molecule GPR84 antagonists. Upon acute liver injury in mice, treatment with GPR84 antagonists significantly reduced the hepatic recruitment of neutrophils, monocytes, and monocyte-derived macrophages (MoMF). We, therefore, evaluated the therapeutic inhibition of GPR84 by these two novel antagonists in comparison to selonsertib, an apoptosis signal-regulating kinase 1 (ASK1) inhibitor, in three NASH mouse models. Pharmacological inhibition of GPR84 significantly reduced macrophage accumulation and ameliorated inflammation and fibrosis, to an extent similar to selonsertib. In conclusion, our findings support that GPR84 mediates myeloid cell infiltration in liver injury and is a promising therapeutic target in steatohepatitis and fibrosis.

Discovery of 9-Cyclopropylethynyl-2-((S)-1-[1,4]dioxan-2-ylmethoxy)-6,7-dihydropyrimido[6,1-a]isoquinolin-4-one (GLPG1205), a Unique GPR84 Negative Allosteric Modulator Undergoing Evaluation in a Phase II Clinical Trial.

GPR84 is a medium chain free fatty acid-binding G-protein-coupled receptor associated with inflammatory and fibrotic diseases. As the only reported antagonist of GPR84 (PBI-4050) that displays relatively low potency and selectivity, a clear need exists for an improved modulator. Structural optimization of GPR84 antagonist hit 1, identified through high-throughput screening, led to the identification of potent and selective GPR84 inhibitor GLPG1205 (36). Compared with the initial hit, 36 showed improved potency in a guanosine 5'-O-[γ-thio]triphosphate assay, exhibited metabolic stability, and lacked activity against phosphodiesterase-4. This novel pharmacological tool allowed investigation of the therapeutic potential of GPR84 inhibition. At once-daily doses of 3 and 10 mg/kg, GLPG1205 reduced disease activity index score and neutrophil infiltration in a mouse dextran sodium sulfate-induced chronic inflammatory bowel disease model, with efficacy similar to positive-control compound sulfasalazine. The drug discovery steps leading to GLPG1205 identification, currently under phase II clinical investigation, are described herein.

Increased bone resorption and osteopenia in Dlx5 heterozygous mice.

Distal-less (Dlx) homeobox transcription factors play a central role in the control of osteogenesis. In particular, Dlx5 regulates osteoblasts/osteoclasts coupling during perinatal bone formation. We analyze here the effect of Dlx5 allelic reduction in the control of bone remodeling. We first show that Dlx5 expression persists during postnatal bone development. We then compare the skeletal phenotype of 10- and 20-week-old Dlx5(+/-) mice to that of wild-type (WT) littermates. Dlx5(+/-) male mice exhibit lower bone mineral density (BMD) at both ages while only 20-week-old females are affected. microCT analyses reveal a reduction in cortical thickness of femoral midshafts in Dlx5(+/-) mice. Histomorphometry on distal femora shows no changes in trabecular structure and confirms a reduction in Dlx5(+/-) cortical thickness. The cortical decrease of 10-week-old mice does not derive from a reduction in periosteal bone apposition, but results from increased bone resorption with a significantly higher number of endosteal osteoclasts per bone surface and a larger marrow diameter. Urinary level of deoxypyridinoline is also higher in heterozygous mice confirming an increase in bone resorption activity. Our findings might be relevant for understanding complex, multifactorial diseases such as osteoporosis in which quantitative deregulation of gene expression leads to disruption of bone homeostasis.

Bone protection by estrens occurs through non-tissue-selective activation of the androgen receptor.

The use of estrogens and androgens to prevent bone loss is limited by their unwanted side effects, especially in reproductive organs and breast. Selective estrogen receptor modulators (SERMs) partially avoid such unwanted effects, but their efficacy on bone is only moderate compared with that of estradiol or androgens. Estrens have been suggested to not only prevent bone loss but also exert anabolic effects on bone while avoiding unwanted effects on reproductive organs. In this study, we compared the effects of a SERM (PSK3471) and 2 estrens (estren-alpha and estren-beta) on bone and reproductive organs to determine whether estrens are safe and act via the estrogen receptors and/or the androgen receptor (AR). Estrens and PSK3471 prevented gonadectomy-induced bone loss in male and female mice, but none showed true anabolic effects. Unlike SERMs, the estrens induced reproductive organ hypertrophy in both male and female mice and enhanced MCF-7 cell proliferation in vitro. Estrens directly activated transcription in several cell lines, albeit at much higher concentrations than estradiol or the SERM, and acted for the most part through the AR. We conclude that the estrens act mostly through the AR and, in mice, do not fulfill the preclinical efficacy or safety criteria required for the treatment or prevention of osteoporosis.

Tumor alphavbeta3 integrin is a therapeutic target for breast cancer bone metastases.

In breast cancer bone metastasis, tumor cells stimulate osteoclast-mediated bone resorption, and bone-derived growth factors released from resorbed bone stimulate tumor growth. The alphavbeta3 integrin is an adhesion receptor expressed by breast cancer cells and osteoclasts. It is implicated in tumor cell invasion and osteoclast-mediated bone resorption. Here, we hypothesized that the therapeutic targeting of tumor alphavbeta3 integrin would prevent bone metastasis formation. We first showed that, compared with mock-transfected cells, the i.v. inoculation of alphavbeta3-overexpressing MDA-MB-231 breast cancer cells in animals increased bone metastasis incidence and promoted both skeletal tumor burden and bone destruction. The direct inoculation of alphavbeta3-overexpressing transfectants into the tibial bone marrow cavity did not however enhance skeletal tumor burden and bone destruction, suggesting that alphavbeta3 controls earlier events during bone metastasis formation. We next examined whether a nonpeptide antagonist of alphavbeta3 (PSK1404) exhibits meaningful antitumor effects in experimental breast and ovarian cancer bone metastasis. A continuous PSK1404 treatment, which inhibited osteoclast-mediated bone resorption in an animal model of bone loss, substantially reduced bone destruction and decreased skeletal tumor burden. Importantly, a short-term PSK1404 treatment that did not inhibit osteoclast activity also decreased skeletal tumor burden and bone destruction. This dosing regimen caused a profound and specific inhibition of bone marrow colonization by green fluorescent protein, alphavbeta3-expressing tumor cells in vivo and blocked tumor cell invasion in vitro. Overall, our data show that tumor alphavbeta3 integrin stands as a therapeutic target for the prevention of skeletal metastases.

A convenient clinically relevant model of human breast cancer bone metastasis.

Breast cancer patients with advanced disease exhibit bone metastases, leading to the formation of osteolytic lesions for which the only currently available treatments are palliative. Here, we describe how we refined a mouse model of human breast cancer metastasis into bone, characterized its transcriptome and demonstrated its clinical relevance. Cells were selected from bone metastases caused by MDA-MB-231 cells after several in vivo passages, and engineered to express luciferase. Whole body bioluminescence live imaging indicated that the selected isogenic B02 clone was unique in its ability to form rapidly growing osteolytic bone metastases. B02 cells were detected as early as 10 days after tail vein injection, as opposed to 1 month after cardiac injection in other haematogenous models. Whole transcriptomic analysis identified 114 upregulated and 247 downregulated genes in B02 cells compared to the parental cells, several of which represent novel targets. In addition, there was a 50% overlap between the B02 signature and a recently described signature obtained from human breast cancer bone metastases. Consistent with the plasticity of an aggressive metastatic variant, 10% of the regulated genes are involved in proliferation, migration, invasion and angiogenesis. Strikingly, B02 cells also express osteoblast-specific genes, thus mimicking a process referred to as osteomimicry in the clinic. The B02 cells "human bone metastatic signature", the expression of bone-specific genes, as well as the live imaging of this convenient model highlight its clinical relevance and usefulness during drug development.

A functional androgen receptor is not sufficient to allow estradiol to protect bone after gonadectomy in estradiol receptor-deficient mice.

Although the role of estradiol in maintaining bone mass is well established, the relative contributions of the estradiol receptors ERalpha and ERbeta and of the androgen receptor (AR) remain controversial. To determine the role of ERalpha-mediated, ERbeta-mediated, and non-ER-mediated mechanisms in maintaining bone mass, gonadectomy and estradiol treatment were studied in ER-knockout mice. Estradiol treatment of ovariectomized ERalphabeta(-/-) mice failed to prevent bone loss, precluding significant effects of estradiol on bone through non-ER-signaling pathways. In contrast, estradiol prevented ovariectomy-induced bone loss in ERbeta(-/-) mice, as in WT males and females, indicating that ERalpha is the major mediator of estradiol effects in bone. No response of bone to estradiol was detected in orchidectomized ERalpha(-/-) mice, suggesting estradiol cannot protect bone mass via the AR in vivo. In contrast to female ERalphabeta(-/-) and male ERalpha(-/-) mice, female ERalpha(-/-) mice were partially protected against ovariectomy-induced bone loss by estradiol, confirming that ERbeta mediates estradiol effects in bone, but only in females and with a lower efficacy than ERalpha. We conclude that ERalpha is the main effector of estradiol's protective function in bone in both male and female mice, and that, in its absence, AR is not sufficient to mediate this response.

Deletion of a single allele of the Dkk1 gene leads to an increase in bone formation and bone mass.

UNLABELLED: Wnt/beta-catenin signaling has been proven to play a central role in bone biology. Unexpectedly, the Wnt antagonist Dkk2 is required for terminal osteoblast differentiation and mineralized matrix formation. We show that Dkk1, unlike Dkk2, negatively regulates osteoblast differentiation and bone formation. INTRODUCTION: The Wnt co-receptor LRP5 is a critical regulator of bone mass. Dickkopf (Dkk) proteins act as natural Wnt antagonists by bridging LRP5/6 and Kremen, inducing the internalization of the complex. Wnt antagonists are thus expected to negatively regulation bone formation. However, Dkk2 deficiency results in increased bone, questioning the precise role of Dkks in bone metabolism. MATERIALS AND METHODS: In this study, we investigated specifically the role of Dkk1 in bone in vitro and in vivo. Using rat primary calvaria cells, we studied the effect of retroviral expression of Dkk1 on osteoblast differentiation. In addition, the effect of Dkk1 osteoblast was studied in MC3T3-E1 cells by means of recombinant protein. Finally, to address the role of Dkk1 in vivo, we analyzed the bone phenotype of Dkk1(+/-) animals. RESULTS: Retroviral expression of Dkk1 in rat primary calvaria cells resulted in a complete inhibition of osteoblast differentiation and formation of mineralized nodules, with a marked decrease in the expression of alkaline phosphatase. Dkk1 expression also increased adipocyte differentiation in these cell cultures. Recombinant murine Dkk1 (rmDkk1) inhibited spontaneous and induced osteoblast differentiation of MC3T3-E1 cells. To determine the role of Dkk1 in vivo and overcome the embryonic lethality of homozygous deletion, we studied the bone phenotype in heterozygous Dkk1-deficient mice. Structural, dynamic, and cellular analysis of bone remodeling in Dkk1(+/-) mice showed an increase in all bone formation parameters, with no change in bone resorption, leading to a marked increase in bone mass. Importantly, the number of osteoblasts, mineral apposition, and bone formation rate were all increased several fold. CONCLUSIONS: We conclude that Dkk1 protein is a potent negative regulator of osteoblasts in vitro and in vivo. Given that a heterozygous decrease in Dkk1 expression is sufficient to induce a significant increase in bone mass, antagonizing Dkk1 should result in a potent anabolic effect.

Targeting of alpha-v integrins reduces malignancy of bladder carcinoma.

Low survival rates of metastatic cancers emphasize the need for a drug that can prevent and/or treat metastatic cancer. αv integrins are involved in essential processes for tumor growth and metastasis and targeting of αv integrins has been shown to decrease angiogenesis, tumor growth and metastasis. In this study, the role of αv integrin and its potential as a drug target in bladder cancer was investigated. Treatment with an αv integrin antagonist as well as knockdown of αv integrin in the bladder carcinoma cell lines, resulted in reduced malignancy in vitro, as illustrated by decreased proliferative, migratory and clonogenic capacity. The CDH1/CDH2 ratio increased, indicating a shift towards a more epithelial phenotype. This shift appeared to be associated with downregulation of EMT-inducing transcription factors including SNAI2. The expression levels of the self-renewal genes NANOG and BMI1 decreased as well as the number of cells with high Aldehyde Dehydrogenase activity. In addition, self-renewal ability decreased as measured with the urosphere assay. In line with these observations, knockdown or treatment of αv integrins resulted in decreased metastatic growth in preclinical in vivo models as assessed by bioluminescence imaging. In conclusion, we show that αv integrins are involved in migration, EMT and maintenance of Aldehyde Dehydrogenase activity in bladder cancer cells. Targeting of αv integrins might be a promising approach for treatment and/or prevention of metastatic bladder cancer.

Triazolopyridines as selective JAK1 inhibitors: from hit identification to GLPG0634.

Janus kinases (JAK1, JAK2, JAK3, and TYK2) are involved in the signaling of multiple cytokines important in cellular function. Blockade of the JAK-STAT pathway with a small molecule has been shown to provide therapeutic immunomodulation. Having identified JAK1 as a possible new target for arthritis at Galapagos, the compound library was screened against JAK1, resulting in the identification of a triazolopyridine-based series of inhibitors represented by 3. Optimization within this chemical series led to identification of GLPG0634 (65, filgotinib), a selective JAK1 inhibitor currently in phase 2B development for RA and phase 2A development for Crohn's disease (CD).

Increased expression of a set of genes enriched in oxygen binding function discloses a predisposition of breast cancer bone metastases to generate metastasis spread in multiple organs.

Bone is the preferential site of distant metastasis in breast carcinoma (BrCa). Patients with metastasis restricted to bone (BO) usually show a longer overall survival compared to patients who rapidly develop multiple metastases also involving liver and lung. Hence, molecular predisposition to generate bone and visceral metastases (BV) represents a clear indication of poor clinical outcome. We performed microarray analysis with two different chip platforms, Affymetrix and Agilent, on bone metastasis samples from BO and BV patients. The unsupervised hierarchical clustering of the resulting transcriptomes correlated with the clinical progression, segregating the BO from the BV profiles. Matching the twofold significantly regulated genes from Affymetrix and Agilent chips resulted in a 15-gene signature with 13 upregulated and two downregulated genes in BV versus BO bone metastasis samples. In order to validate the resulting signature, we isolated different MDA-MB-231 clonal subpopulations that metastasize only in the bone (MDA-BO) or in bone and visceral tissues (MDA-BV). Six of the signature genes were also significantly upregulated in MDA-BV compared to MDA-BO clones. A group of upregulated genes, including Hemoglobin B (HBB), were involved in oxygen metabolism, and in vitro functional analysis of HBB revealed that its expression in the MDA subpopulations was associated with a reduced production of hydrogen peroxide. Expression of HBB was detected in primary BrCa tissue but not in normal breast epithelial cells. Metastatic lymph nodes were frequently more positive for HBB compared to the corresponding primary tumors, whereas BO metastases had a lower expression than BV metastases, suggesting a positive correlation between HBB and ability of bone metastasis to rapidly spread to other organs. We propose that HBB, along with other genes involved in oxygen metabolism, confers a more aggressive metastatic phenotype in BrCa cells disseminated to bone.

Discovery of diarylhydantoins as new selective androgen receptor modulators.

A novel selective androgen receptor modulator scaffold has been discovered through structural modifications of hydantoin antiandrogens. Several 4-(4-hydroxyphenyl)-N-arylhydantoins displayed partial agonism with nanomolar in vitro potency in transactivation experiments using androgen receptor (AR) transfected cells. In a standard castrated male rat model, several compounds showed good anabolic activity on levator ani muscle, dissociated from the androgenic activity on ventral prostate, after oral dosing at 30 mg/kg. (+)-4-[3,4-Dimethyl-2,5-dioxo-4-(4-hydroxyphenyl)imidazolidin-1-yl]-2-(trifluoromethyl)benzonitrile ((+)-11b) displayed anabolic potency with a strong dissociation between levator ani muscle and ventral prostate (A(50) = 0.5 mg/kg vs 70 mg/kg). The binding modes of two compounds, including (+)-11b, within the AR ligand-binding domain have been studied by cocrystallization experiments using a coactivator-like peptide. Both compounds bound to the same site, and the overall structures of the AR were very similar.

Targeting of α(v)-integrins in stem/progenitor cells and supportive microenvironment impairs bone metastasis in human prostate cancer.

Acquisition of an invasive phenotype by cancer cells is a requirement for bone metastasis. Transformed epithelial cells can switch to a motile, mesenchymal phenotype by epithelial-mesenchymal transition (EMT). Recently, it has been shown that EMT is functionally linked to prostate cancer stem cells, which are not only critically involved in prostate cancer maintenance but also in bone metastasis. We showed that treatment with the non-peptide α(v)-integrin antagonist GLPG0187 dose-dependently increased the E-cadherin/vimentin ratio, rendering the cells a more epithelial, sessile phenotype. In addition, GLPG0187 dose-dependently diminished the size of the aldehyde dehydrogenase high subpopulation of prostate cancer cells, suggesting that α(v)-integrin plays an important role in maintaining the prostate cancer stem/progenitor pool. Our data show that GLPG0187 is a potent inhibitor of osteoclastic bone resorption and angiogenesis in vitro and in vivo. Real-time bioluminescent imaging in preclinical models of prostate cancer demonstrated that blocking α(v)-integrins by GLPG0187 markedly reduced their metastatic tumor growth according to preventive and curative protocols. Bone tumor burden was significantly lower in the preventive protocol. In addition, the number of bone metastases/mouse was significantly inhibited. In the curative protocol, the progression of bone metastases and the formation of new bone metastases during the treatment period was significantly inhibited. In conclusion, we demonstrate that targeting of integrins by GLPG0187 can inhibit the de novo formation and progression of bone metastases in prostate cancer by antitumor (including inhibition of EMT and the size of the prostate cancer stem cell population), antiresorptive, and antiangiogenic mechanisms.

No evidence for a bone phenotype in GPRC6A knockout mice under normal physiological conditions.

GPRC6A is a seven-transmembrane receptor mediating signaling by a wide range of L-alpha-amino acids, a signaling augmented by the divalent cations Ca(2)(+) and Mg(2)(+). GPRC6A transcripts are detected in numerous mammalian tissues, but the physiological role of the receptor is thus far elusive. Analogously to the closely related calcium-sensing receptor, GPRC6A has been proposed to function as a metabolic sensor of Ca(2)(+) and amino acids in bone and other tissues. In the present study, we have generated the first GPRC6A knockout mice and studied their phenotype with particular focus on bone homeostasis. The generated GPRC6A knockout mice are viable and fertile, develop normally, and exhibit no significant differences in body weight compared with wild-type littermates. Assessment of bone mineral density, histomorphometry, and bone metabolism demonstrated no significant differences between 13-week-old knockout and wild-type mice. In conclusion, our data do not support a role for GPRC6A in normal bone physiology.