Bone Metastasis Of Cancer Cells Research Articles

AMPK activation attenuates cancer-induced bone pain by reducing mitochondrial dysfunction-mediated neuroinflammation.

Bone metastasis of cancer cells leads to severe pain by disrupting bone structure and inducing central sensitization. Neuroinflammation in the spinal cord plays a decisive role in the maintenance and development of pain. In the current study, male Sprague-Dawley (SD) rats are used to establish a cancer-induced bone pain (CIBP) model by intratibial injection of MRMT-1 rat breast carcinoma cells. Morphological and behavioral analyses verify the establishment of the CIBP model, which represents bone destruction, spontaneous pain and mechanical hyperalgesia in CIBP rats. Activation of astrocytes marked by upregulated glial fibrillary acidic protein (GFAP) and enhanced production of the proinflammatory cytokine interleukin-1β (IL-1β) are accompanied by increased inflammatory infiltration in the spinal cord of CIBP rats. Furthermore, activation of the NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is consistent with increased neuroinflammation. Adenosine monophosphate-activated protein kinase (AMPK) activation is involved in attenuating inflammatory pain and neuropathic pain. Intrathecal injection of the AMPK activator AICAR in the lumbar spinal cord reduces dynamin-related protein 1 (Drp1) GTPase activity and suppresses NLRP3 inflammasome activation. This effect consequently alleviates pain behaviors in CIBP rats. Cell research on C6 rat glioma cells indicates that AICAR treatment restores IL-1β-induced impairment of mitochondrial membrane potential and elevation of mitochondrial reactive oxygen species (ROS). In summary, our findings indicate that AMPK activation attenuates cancer-induced bone pain by reducing mitochondrial dysfunction-mediated neuroinflammation in the spinal cord.

Protein Kinase D2 and D3 Promote Prostate Cancer Cell Bone Metastasis by Positively Regulating Runx2 in a MEK/ERK1/2–Dependent Manner

Advanced-stage prostate tumors metastasize to the bone, often causing death. The protein kinase D (PKD) family has been implicated in prostate cancer development; however, its role in prostate cancer metastasis remains elusive. This study examined the contribution of PKD, particularly PKD2 and PKD3 (PKD2/3), to the metastatic potential of prostate cancer cells and the effect of PKD inhibition on prostate cancer bone metastasis invivo. Depletion of PKD2/3 by siRNAs or inhibition by the PKD inhibitor CRT0066101 in AR-positive and AR-negative castration-resistant prostate cancer cells potently inhibited colony formation and cell migration. Depletion or inhibition of PKD2/3 significantly blocked tumor cell invasion and suppressed the expression of genes related to bone metastasis in the highly invasive PC3-ML cells. The reduced invasive activity resulting from PKD2/3 depletion was in part mediated by the transcription factor Runx2, as its silencing decreased PKD2/3-mediated metastatic gene expression through the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 signaling axis. Furthermore, inhibition of PKD by CRT0066101 potently decreased the frequency of bone micrometastases in a mouse model of bone metastasis based on intracardiac injection of PC3-ML cells. These results indicate that PKD2/3 plays an important role in the bone metastasis of prostate cancer cells, and its inhibition may be beneficial for the treatment of advanced prostate cancer.

BMP2 as a promising anticancer approach: functions and molecular mechanisms.

Bone morphogenetic protein 2 (BMP2), a pluripotent factor, is a member of the transforming growth factor-beta (TGF-β) superfamily and is implicated in embryonic development and postnatal homeostasis in tissues and organs. Experimental research in the contexts of physiology and pathology has indicated that BMP2 can induce macrophages to differentiate into osteoclasts and accelerate the osteolytic mechanism, aggravating cancer cell bone metastasis. Emerging studies have stressed the potent regulatory effect of BMP2 in cancer cell differentiation, proliferation, survival, and apoptosis. Complicated signaling networks involving multiple regulatory proteins imply the significant biological functions of BMP2 in cancer. In this review, we comprehensively summarized and discussed the current evidence related to the modulation of BMP2 in tumorigenesis and development, including evidence related to the roles and molecular mechanisms of BMP2 in regulating cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), cancer angiogenesis and the tumor microenvironment (TME). All these findings suggest that BMP2 may be an effective therapeutic target for cancer and a new marker for assessing treatment efficacy.

Au Nanoparticles Attenuate RANKL-Induced Osteoclastogenesis by Suppressing Pre-Osteoclast Fusion.

Osteoclasts are multinucleated terminal cells that originate from a hematopoietic monocyte/macrophage lineage. Excessive osteoclast formation in vivo can lead to bone metabolic diseases such as postmenopausal osteoporosis, multiple myeloma, rheumatoid arthritis, and lytic bone metastases of cancer cells. Au nanoparticles (AuNPs) are inorganic nanoparticles with outstanding biocompatibility. We assessed their effect on osteoclastogenesis and found that pre-osteoclast fusion induced by receptor activator of nuclear factor kappa-B ligand (RANKL) and macrophage colonystimulating factor (M-CSF) was suppressed by AuNPs. Cell migration and actin ring formation were also significantly inhibited. Finally, AuNPs reduced osteoclast bone absorption function. Interestingly, we observed altered fusogenic gene expression in treated pre-osteoclasts. Our results suggest that AuNPs have potential as a therapeutic agent for osteoclast-related bone metabolism diseases.

Artemisinin-Daumone Hybrid Inhibits Cancer Cell-Mediated Osteolysis by Targeting Cancer Cells and Osteoclasts

Background/Aims: Bone metastasis of cancer cells decreases patient survival and quality of life. Hybridization via the covalent coupling of two bioactive natural products is a useful strategy for developing more potent anticancer agents by enhancing their bioavailability and avoiding drug resistance. Methods: The in vivo activities of artemisinin-daumone hybrid 15 (ARTD) were estimated in cancer cell-inoculated mice and ovariectomized mice. The viability, migration, and invasion of cancer cells were measured via MTT, wound-healing, and transwell invasion assays. ARTD-regulated transcription factors were detected with an RT² profiler PCR array kit and Western blotting. Osteoclastogenesis and osteoclast activity were detected with tartrate-resistant acid phosphatase staining, a pit formation assay, gelatin zymography, and a cathepsin K ELISA assay. Results: ARTD blocked cancer-associated osteolysis more potently than artemisinin in mice with intratibially inoculated breast cancer or lung cancer cells. ARTD inhibited the viability, migration, and invasion of breast and lung cancer cells in the absence or presence of transforming growth factor-β1. ARTD treatment induced the expression of tumor suppressive activating transcription factor 3 and inhibited oncogenic E2F transcription factor 1 expression at the mRNA and protein levels. ARTD inhibited receptor activator of nuclear factor kappa-B ligand-induced osteoclast formation and bone resorbing activity by reducing the secreted levels of matrix metalloproteinase-9 and cathepsin K. Furthermore, ARTD prevented estrogen deficiency-induced bone loss in ovariectomized mice. Conclusion: ARTD may be a promising candidate for inhibiting cancer-induced bone destruction. The application of ARTD may be extended to patients with chemotherapy-induced ovarian failure or postmenopausal osteoporosis.

Surface vacuolar ATPase in ameloblastoma contributes to tumor invasion of the jaw bone.

Ameloblastoma is the most common benign odontogenic tumor in Japan. It is believed that it expands in the jaw bone through peritumoral activation of osteoclasts by receptor activator of nuclear factor kappa-B ligand (RANKL) released from the ameloblastoma, as in bone metastases of cancer cells. However, the clinical features of ameloblastoma, including its growth rate and patterns of invasion, are quite different from those of bone metastasis of cancer cells, suggesting that different underlying mechanisms are involved. Therefore, in the present study, we examined the possible mechanisms underlying the invasive expansion of ameloblastoma in the jaw bone. Expression levels of RANKL assessed by western blotting were markedly lower in ameloblastoma (AM-1) cells than in highly metastatic oral squamous cell carcinoma (HSC-3) cells. Experiments coculturing mouse macrophages (RAW264.7) with AM-1 demonstrated low osteoclastogenic activity, as assessed by tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cell formation, probably because of low release of RANKL, whereas cocultures of RAW264.7 with HSC-3 cells exhibited very high osteoclastogenic activity. Thus, RANKL release from AM-1 appeared to be too low to generate osteoclasts. However, AM-1 cultured directly on calcium phosphate-coated plates formed resorption pits, and this was inhibited by application of bafilomycin A1. Furthermore, vacuolar-type H+-ATPase (V-ATPase) and H+/Cl- exchange transporter 7 (CLC-7) were detected on the surface of AM-1 cells by plasma membrane biotinylation and immunofluorescence analysis. Immunohistochemical analysis of clinical samples of ameloblastoma also showed plasma membrane-localized V-ATPase and CLC-7 in the epithelium of plexiform, follicular and basal cell types. The demineralization activity of AM-1 was only 1.7% of osteoclasts demineralization activity, and the growth rate was 20% of human normal skin keratinocytes and HSC-3 cells. These results suggest that the slow expansion of several typical types of ameloblastomas in jaw bone is attributable to its slow growth and low demineralization ability.

MacroH2A acts as a key regulator of osteolytic bone metastasis of cancer cells

MacroH2A acts as a key regulator of osteolytic bone metastasis of cancer cells

PKCε Is an Essential Mediator of Prostate Cancer Bone Metastasis.

The bone is a preferred site for metastatic homing of prostate cancer cells. Once prostate cancer patients develop skeletal metastases, they eventually succumb to the disease; therefore, it is imperative to identify key molecular drivers of this process. This study examines the involvement of protein kinase C epsilon (PKCε), an oncogenic protein that is abnormally overexpressed in human tumor specimens and cell lines, on prostate cancer cell bone metastasis. PC3-ML cells, a highly invasive prostate cancer PC3 derivative with bone metastatic colonization properties, failed to induce skeletal metastatic foci upon inoculation into nude mice when PKCε expression was silenced using shRNA. Interestingly, while PKCε depletion had only marginal effects on the proliferative, adhesive, and migratory capacities of PC3-ML cells in vitro or in the growth of xenografts upon s.c. inoculation, it caused a significant reduction in cell invasiveness. Notably, PKCε was required for transendothelial cell migration (TEM) as well as for the growth of PC3-ML cells in a bone biomimetic environment. At a mechanistic level, PKCε depletion abrogates the expression of IL1β, a cytokine implicated in skeletal metastasis. Taken together, PKCε is a key factor for driving the formation of bone metastasis by prostate cancer cells and is a potential therapeutic target for advanced stages of the disease. This study uncovers an important new function of PKCε in the dissemination of cancer cells to the bone; thus, highlighting the promising potential of this oncogenic kinase as a therapeutic target for skeletal metastasis.

TGFβ-Mediated induction of SphK1 as a potential determinant in human MDA-MB-231 breast cancer cell bone metastasis.

Mechanistic understanding of the preferential homing of circulating tumor cells to bone and their perturbation on bone metabolism within the tumor-bone microenvironment remains poorly understood. Alteration in both transforming growth factor β (TGFβ) signaling and sphingolipid metabolism results in the promotion of tumor growth and metastasis. Previous studies using MDA-MB-231 human breast cancer-derived cell lines of variable metastatic potential were queried for changes in sphingolipid metabolism genes to explore correlations between TGFβ dependence and bone metastatic behavior. Of these genes, only sphingosine kinase-1 (SPHK1) was identified to be significantly increased following TGFβ treatment. Induction of SPHK1 expression correlated to the degree of metastatic capacity in these MDA-MB-231-derived cell lines. We demonstrate that TGFβ mediates the regulation of SPHK1 gene expression, protein kinase activity and is critical to MDA-MB-231 cell viability. Furthermore, a bioinformatic analysis of human breast cancer gene expression supports SPHK1 as a hallmark TGFβ target gene that also bears the genetic fingerprint of the basal-like/triple-negative breast cancer molecular subtype. These data suggest a potential new signaling axis between TGFβ/SphK1 that may have a role in the development, prognosis or the clinical phenotype associated with tumor-bone metastasis.

Study on 41Ca-AMS for diagnosis and assessment of cancer bone metastasis in rats

The annual incidence of new cancer patients in China is about 2 million, 30–40% of which will end up with bone metastasis. Profound study on the preclinical model and early diagnosis of cancer bone metastasis in rats are very significant for the drug development, better understanding and treatment of bone metastases. In order to monitor the process of bone metabolism and early detection of bone metastasis of cancer cells, a technique of 41Ca isotope tracer combined with AMS has been developed and applied in the study on the bone metastasis of cancer cells by rat model. In this work, 3-month-old female Sprague–Dawley (SD) rats were randomly divided into different groups, and tumor cells injected respectively into the tail vein, femoral artery, femoral cavity and the thigh muscle to establish the rat models for bone metastases. The most appropriate model, i.e., the thigh muscle group, was finally adopted in our real metastases experiment. Each rat in this group was intramuscularly (i.m.) injected with 250μlCaCl2 solution (containing 1.4mgCa and 5nCi 41Ca). About 40days later, the rat mammary gland carcinoma cells (Walker 256) were injected into these rats following the established protocol. After bone metastasis, medicine interventions were performed. The sequential urine and blood samples were collected and analyzed for 41Ca (by AMS) and N-terminal telopeptide (Ntx), respectively. Bone Mineral Density (BMD) values in the femur and the tibia were measured by CT scan. The results of 41Ca/Ca in longitudinal urinary samples can sensitively reveal the skeletal perturbations caused by bone metastasis of rats, suggests that 41Ca might be similarly developed for human use and improve clinical management through the assessment of the curative effect and non-invasive detection of the earliest stages of cancer growth in bone.

Marine algae Sargassum horneri bioactive factor suppresses proliferation and stimulates apoptotic cell death in human breast cancer MDA-MB-231 cells in vitro

Marine algae Sargassum horneri (S. horneri) bioactive factor has been shown to possess anabolic bone e! ects due to stimulating osteblastic bone formation and suppressing osteoclastogenes. However, the e! ects of S. horneri on cancer cell bone metastasis have not been investigated. is study was undertaken to determine the e! ects of S. horneri bioactive component on human breast cancer MDA-MB-231 bone metastatic cells in vitro. Proliferation of MDA-MB-231 cells was suppressed by culture with S. horneri active component (less than 3000 molecular weight; 10-200 µg/ml) for 5 and 10 days. S. horneri active component was suggested to inhibit G1 and G2/M phase cell cycle arrest in MDA-MB-231 cells using inhibitors of cell-cycle arrest. Moreover, S. horneri active component stimulated apoptotic cell death. is e! ect was prevented in the presence of caspase-3-inhibitor. us, S. horneri active component was found to suppress cell proliferation and stimulate apoptotic cell death in human breast cancer MDA-MB-231 bone metastatic cells in vitro, demonstrating an anticancer e! ect.

Curcumin analog UBS109 prevents bone marrow osteoblastogenesis and osteoclastogenesis disordered by coculture with breast cancer MDA-MB-231 bone metastatic cells in vitro.

UBS109 is a curcumin analog that possessesantitumor properties has been shown to stimulate osteoblastogenesis and suppress osteoclastogenesis in vitro. This study was undertaken to determine whether UBS109 might alleviate the inhibitory activity of breast cancer cells on osteoblastic mineralization and stimulatory effects on osteoclastogenesis. Mouse bone marrow cells werecocultured with breast cancer MDA-MB-231 bone metastatic cells in vitro. UBS109 stimulated osteoblastic mineralization and suppressed adipogenesis and osteoclastogenesis in bone marrow culture. Coculture with MDA-MB-231 cells suppressed osteoblastic mineralization and enhanced osteoclastogenesis in bone marrow culture. Effects that were reserved by UBS109 (50-200nM). Mineralization in preosteoblastic MC3T3-E1 cells was suppressed by coculture with MDA-MB-231 cells, while MDA-MB-231 cells did not have effects on osteoclastogenesis of RAW267.4 cells in vitro. UBS109 (500nM) revealed toxic effects on MDA-MB-231 bone metastatic cells. This study demonstrates that UBS109, which is anantitumor agent, reveals restorative effects on bone marrow cell differentiation disordered by coculture with breast cancer MDA-MB-231 bone metastatic cells in vitro. This in vitro model may be a useful tool to evaluate the mechanism of breast cancer cell bone metastasis.

Curcumin analogue UBS109 prevents bone loss in breast cancer bone metastasis mouse model: involvement in osteoblastogenesis and osteoclastogenesis.

Bone metastasis of breast cancer typically leads to osteolysis, which causes severe pathological bone fractures and hypercalcemia. Bone homeostasis is skillfully regulated through osteoblasts and osteoclasts. Bone loss with bone metastasis of breast cancer may be due to both activation of osteoclastic bone resorption and suppression of osteoblastic bone formation. This study was undertaken to determine whether the novel curcumin analogue UBS109 has preventive effects on bone loss induced by breast cancer cell bone metastasis. Nude mice were inoculated with breast cancer MDA-MB-231 bone metastatic cells (10(6) cells/mouse) into the head of the right and left tibia. One week after inoculation, the mice were treated with control (vehicle), oral administration (p.o.) of UBS109 (50 or 150mg/kg body weight), or intraperitoneal administration (i.p.) of UBS109 (10 or 20mg/kg body weight) once daily for 5days per week for 7weeks. After UBS109 administration for 7weeks, hind limbs were assessed using an X-ray diagnosis system and hematoxylin and eosion staining to determine osteolytic destruction. Bone marrow cells obtained from the femurs and tibias were cultured to estimate osteoblastic mineralization and osteoclastogenesis ex vivo and in vitro. Remarkable bone loss was demonstrated in the tibias of mice inoculated with breast cancer MDA-MB-231 bone metastatic cells. This bone loss was prevented by p.o. administration of UBS109 (50 and 150mg/kg body weight) and i.p. treatment of UBS109 (10 and 20mg/kg) in vivo. Culture of bone marrow cells obtained from the bone tissues of mice with breast cancer cell bone metastasis showed suppressed osteoblastic mineralization and stimulated osteoclastogenesis ex vivo. These changes were not seen after culture of the bone marrow cells obtained from mice treated with UBS109. Moreover, UBS109 was found to stimulate osteoblastic mineralization and suppress lipopolysaccharide (LPS)-induced osteoclastogenesis in bone marrow cells obtained from normal nude mice in vitro. These findings suggest that the novel curcumin analogue UBS109 prevents breast cancer cell bone metastasis-induced bone loss by stimulating osteoblastic mineralization and suppressing osteoclastogenesis.

Osteoporosis Treatment with Functional Food Factor: Vitamin K2

Bone homeostasis is maintained through a delicate balance between osteoblastic bone formation and osteoclastic bone resorption [1]. Numerous pathological processes have the capacity to disrupt this equilibrium leading to conditions where the rate of bone resorption outpaces the rate of bone formation leading to osteoporosis, a devastating bone disease that is widely recognized as a major public health threat. Bone loss is accelerated with increasing age, inducing elderly osteoporosis. Postmenopausal osteoporosis, a consequence of ovarian hormone deficiency, is the archetypal osteoporotic condition in women after menopause and leads to bone destruction though complex and diverse metabolic and biochemical changes [2]. Moreover, osteoporosis is induced through obesity, diabetes, and inflammation and cancer cell bone metastasis. The most dramatic expression of this disease is represented by bone fractures.

New Development in Osteoporosis Treatment: The Synergistical Osteogenic Effects with Vitamin D3, Menaquinone-7, Genistein and Zinc

Copyright: © 2013 Yamaguchi M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Bone is a dynamic tissue that undergoes continual adaptation during vertebrate life to attain and preserve skeletal size, shape, and structural integrity and to regulate mineral homeostasis. Two processes, remodeling and modeling, underpin development and maintenance of the skeletal system [1]. Bone modeling is responsible for growth and mechanically induced adaptation of bone and requires the processes of bone formation and bone removal (resorption). Bone remodeling is responsible for removal and repair of damaged bone to maintain integrity of the adult skeletal and mineral homeostasis. Bone homeostasis, which maintains bone mass, is skillfully regulated through osteoclasts, osteoblasts and osteocytes, which are major cells in bone tissues. Bone homeostasis is regulated through various physiological systems including many hormones and cytokines and immune systems, and it is disturbed through various pathophysiological states that induce osteoporosis. Aging induces a reduction in bone mass with a decrease in osteoblastic bone formation and an increase in osteoclastic bone resorption. Osteoporosis with its accompanying decrease in bone mass is widely recognized as a major public health problem. The most dramatic expression of the disease is represented by fractures of the proximately femur, and the number of which increase as the population ages [2,3]. Moreover, bone loss has been shown to stimulate in various pathophysiologic states including inflammation, obesity, diabetes, and cancer cell bone metastasis [4]. Malnutrition or undernutrition is often observed with increasing ages, and it appears to be more intense in patients with hip fracture than in the general aging population [5]. The deficiency in both micronutrients and macronutrients appears to be strongly implicated in the pathogenesis and consequences of hip fracture in the osteoporotic elderly. This may generate the concept that bone homeostasis is regulated through various nutritional and food factors in maintaining bone health in long life. There is growing evidence that nutritional and functional food factors have a role in the prevention of bone loss with increasing age [6]. Food life style may help to prevent bone loss with aging. Chemical factors including vitamins and minerals in food and plants, which regulate bone homeostasis, have been to be notice. Recent studies have been shown that these factors stimulate osteoblastic bone formation and suppress osteoclastic bone resorption in osteoporosis animal models and human subjects [6], thereby increasing bone mass. Supplemental intake of ingredients plays an important role in maintaining bone health and in the prevention of bone loss. This may provide a new tool in the treatment of osteoporosis.

The role of versican G3 domain in regulating breast cancer cell motility including effects on osteoblast cell growth and differentiation in vitro– evaluation towards understanding breast cancer cell bone metastasis

BackgroundVersican is detected in the interstitial tissues at the invasive margins of breast carcinoma, is predictive of relapse, and negatively impacts overall survival rates. The versican G3 domain is important in breast cancer cell growth, migration and bone metastasis. However, mechanistic studies evaluating versican G3 enhanced breast cancer bone metastasis are limited.MethodsA versican G3 construct was exogenously expressed in the 66c14 and the MC3T3-E1 cell line. Cells were observed through light microscopy and viability analyzed by Coulter Counter or determined with colorimetric proliferation assays. The Annexin V-FITC apoptosis detection kit was used to detect apoptotic activity. Modified Chemotactic Boyden chamber migration invasion assays were applied to observe tumor migration and invasion to bone stromal cells and MC3T3-E1 cells. Alkaline phosphatase (ALP) staining and ALP ELISA assays were performed to observe ALP activity in MC3T3-E1 cells.ResultsIn the four mouse breast cancer cell lines 67NR, 66c14, 4T07, and 4T1, 4T1 cells expressed higher levels of versican, and showed higher migration and invasion ability to MC3T3-E1 cells and primary bone stromal cells. 4T1 conditioned medium (CM) inhibited MC3T3-E1 cell growth, and even lead to apoptosis. Only 4T1 CM prevented MC3T3-E1 cell differentiation, noted by inhibition of alkaline phosphatase (ALP) activity. We exogenously expressed a versican G3 construct in a cell line that expresses low versican levels (66c14), and observed that the G3-expressing 66c14 cells showed enhanced cell migration and invasion to bone stromal and MC3T3-E1 cells. This observation was prevented by selective EGFR inhibitor AG1478, selective MEK inhibitor PD 98059, and selective AKT inhibitor Triciribine, but not by selective JNK inhibitor SP 600125. Versican G3 enhanced breast cancer cell invasion to bone stromal cells or osteoblast cells appears to occur through enhancing EGFR/ERK or AKT signaling. G3 expressing MC3T3-E1 cells showed inhibited cell growth and cell differentiation when cultured with TGF-β1 (1 ng/ml), and expressed enhanced cell apoptosis when cultured with TNF-α (2 ng/ml). Enhanced EGFR/JNK signaling appears to be responsible for G3 enhanced osteoblast apoptosis and inhibited osteoblast differentiation. Whereas repressed expression of GSK-3β (S9P) contributes to G3 inhibited osteoblast growth. Versican G3 functionality was dependent on its EGF-like motifs. Without the structure of EGF-like repeats, the G3 domain would not confer enhancement of tumor cell migration and invasion to bone with concordant inhibition of osteoblast differentiation and promotion of osteoblast apoptosis.ConclusionsVersican enhances breast cancer bone metastasis not only through enhancing tumor cell mobility, invasion, and survival in bone tissues, but also by inhibiting pre-osteoblast cell growth, differentiation, which supply favorable microenvironments for tumor metastasis.

Differential secretome analysis reveals CST6 as a suppressor of breast cancer bone metastasis

Bone metastasis is a frequent complication of breast cancer and a common cause of morbidity and mortality from the disease. During metastasis secreted proteins play crucial roles in the interactions between cancer cells and host stroma. To characterize the secreted proteins that are associated with breast cancer bone metastasis, we preformed a label-free proteomic analysis to compare the secretomes of four MDA-MB-231 (MDA231) derivative cell lines with varied capacities of bone metastasis. A total of 128 proteins were found to be consistently up-/down-regulated in the conditioned medium of bone-tropic cancer cells. The enriched molecular functions of the altered proteins included receptor binding and peptidase inhibition. Through additional transcriptomic analyses of breast cancer cells, we selected cystatin E/M (CST6), a cysteine protease inhibitor down-regulated in bone-metastatic cells, for further functional studies. Our results showed that CST6 suppressed the proliferation, colony formation, migration and invasion of breast cancer cells. The suppressive function against cancer cell motility was carried out by cancer cell-derived soluble CST6. More importantly, ectopic expression of CST6 in cancer cells rescued mice from overt osteolytic metastasis and deaths in the animal study, while CST6 knockdown markedly enhanced cancer cell bone metastasis and shortened animal survival. Overall, our study provided a systemic secretome analysis of breast cancer bone tropism and established secreted CST6 as a bona fide suppressor of breast cancer osteolytic metastasis.

Structure-based development of specific inhibitors for individual cathepsins and their medical applications

Specific inhibitors for individual cathepsins have been developed based on their tertiary structures of X-ray crystallography. Cathepsin B-specific inhibitors, CA-074 and CA-030, and cathepsin L specific inhibitors, CLIK-148 and CLIK-195, were designed as the epoxysuccinate derivatives. Cathepsin S inhibitor, CLIK-060, and cathepsin K inhibitor, CLIK-166, were synthesized. These inhibitors can use in vitro and also in vivo, and show no toxicity for experimental animals by the amounts used as the cathepsin inhibitor.Various cathepsins are used in the processing of antigenic proteins. The CLIK-060 treatment to the autoimmune disease, Sjögren model mice, led to strongly suppress the expression of the pathological symptoms. Cathepsins L or K participates to the degradation of bone collagen. The CLIK-148 protects osteoporosis in animals and also protects the bone metastasis of cancer cells. Cathepsin L also enhances insulin-induced glucose uptake into 3T3-L1 adipocytes, suggesting cathepsin L plays the roles in adipogenesis and glucose tolerance in type 2 diabetes.

Osteoporosis as a potential contributor to the bone metastases

Bone metastasis is a serious complication of patients with tumor, and most primary tumors can metastasize to bone. And the main threat and the reason for most cancer deaths are not the primary neoplasias, but secondary tumors, the metastases. To minimize the morbidity and economic expenditure associated with bone metastases, it is important to decrease the etiological factors of bone metastasis. Although current evidence suggested that the therapies to the underlying malignancy bone metastasis might result in bone loss leading to osteoporosis, no studies have shown direct evidence the successful seeding of bone metastases of cancer cells is the part played by osteoporosis. In the state of osteoporosis, for the enhancement of the osteolysis, the increased inflammatory factors could make blood vessels leakier, resulting in the easier hematogenous metastasis to bone and bone marrow. Moreover, leptin, which was positive correlation with osteoporosis, has been showed to exert angiogenic effects and could regulate VEGF expression, promoting the proliferation of the cancer blood vessel. In addition, the increased growth factors in osteoporosis could enrich the local microenvironment, promoting the growth of the metastasis mass. Given the above background, we hypothesize that osteoporosis may be a potential contributor to the bone metastases.

RANKL-induced CCL22/macrophage-derived chemokine produced from osteoclasts potentially promotes the bone metastasis of lung cancer expressing its receptor CCR4

Chemokines are now known to play an important role in cancer growth and metastasis. Here we report that differentiating osteoclasts constitutively produce CCL22 (also called macrophage-derived chemokine) and potentially promote bone metastasis of lung cancer expressing its receptor CCR4. We first examined expression of chemokines by differentiating osteoclasts. CCL22 was selectively upregulated in osteoclast-like cells derived from RAW264.7 cells and mouse bone marrow cells upon stimulation with RANKL (receptor activator of nuclear factor-kappaB ligand). In addition, a human lung cancer cell line SBC-5 that efficiently metastasized to bone when intravenously injected into NK cell-depleted SCID mice was found to express CCR4. Stimulation of SBC-5 cells with CCL22 induced cell migration and also enhanced phosphorylation of protein kinase B/Akt and extracellular signal-regulated kinase (ERK). Furthermore, immunohistochemical analysis of bone metastasis lesions demonstrated close co-localization of tartrate-resistant alkaline phosphatase (TRAP)-positive osteoclasts expressing CCL22 and SBC-5 cells expressing CCR4. Collectively, these results suggest that osteoclasts may promote bone metastasis of cancer cells expressing CCR4 in the bone marrow by producing its ligand CCL22.