Docetaxel enhances the therapeutic effect of the angiogenesis inhibitor TNP-470 (AGM-1470) in metastatic human transitional cell carcinoma.

We demonstrated recently that chronic frequent administration of an adequate biological dose of the angiogenesis inhibitor TNP-470 (AGM-1470, O-chloracetyl-carbamoyl fumagillol) completely inhibits spontaneous lymph node metastasis but does not have a complete response on tumor growth of nonestablished or established human metastatic transitional cell carcinoma (TCC) 253J B-V growing orthotopically into athymic nude mice. Therefore, in this study, we evaluated whether docetaxel (Taxotere) enhances the therapeutic effect of TNP-470, especially on tumor growth. Docetaxel enhanced in vitro antiproliferation but not basic fibroblast growth factor down-regulation by TNP-470 in 253J B-V and human umbilical vascular endothelial cells. Docetaxel significantly enhanced in vitro apoptosis by TNP-470 in human umbilical vascular endothelial cells but not in 253J B-V. In vivo combination was most effective when docetaxel was administered before TNP-470, and increased significantly the complete response on tumor growth of nonestablished and established TCCs growing orthotopically into athymic nude mice compared with either therapy alone (P < 0.05). The incidence of spontaneous lymph node metastasis was inhibited completely by the combination therapy (P < 0.05). Drug-induced body weight loss was not significantly different in any treatment groups. The combination of TNP-470 and docetaxel inhibited intratumor neovascularization, the expression of bFGF and matrix metalloproteinases type-9 compared with controls (P < 0.005), and enhanced apoptosis in tumors compared with each therapy alone (P < 0.005). These studies indicate that docetaxel markedly enhances the ability of TNP-470 to inhibit tumorigenicity and metastasis in both nonestablished and established TCCs. These effects are mediated, in part, by the complementary cytotoxicities of angiogenesis inhibition, down-regulation of bFGF and matrix metalloproteinases type-9, and induction of apoptosis.     

Ipriflavone inhibits osteolytic bone metastasis of human breast cancer cells in a nude mouse model

Osteolytic bone metastasis is a frequent problem in the treatment of cancer. Ipriflavone, a synthetic isoflavone that inhibits osteoclastic bone resorption, has been used for the treatment of osteoporosis in some countries. Some other isoflavones also exhibit an antitumor effect in vitro and in vivo. Here, we studied the effects of ipriflavone on osteolytic bone metastasis of MDA-231 human breast cancer cells injected intracardially into athymic nude mice (ICR-nu/nu). Daily oral administration of ipriflavone at 12 mg/mouse significantly inhibited the development of new osteolytic bone metastases (p < 0.05) and the progression of established osteolytic lesions (p = 0.01), prolonging the life of tumor-bearing mice (p = 0.01 vs. control). In addition, ipriflavone reduced the number of osteoclasts at the bone-cancer interface with no severe adverse effects on the host. In vitro, ipriflavone inhibited the proliferation and DNA synthesis of MDA-231 cells and blocked the ligand-induced phosphorylation of Tyr(845) of the EGFR. Ipriflavone did not promote apoptosis of MDA-231 cells. Our results show that ipriflavone not only directly inhibits the growth of cancer cells but also reduces osteoclasts to prevent the soft tissue tumor burden and osteolytic bone metastases. These findings raise the possibility that ipriflavone may be of use as a therapeutic agent against osteolytic bone metastasis.     

Modulation of bone microenvironment with zoledronate enhances the therapeutic effects of STI571 and paclitaxel against experimental bone metastasis of human prostate cancer

Prostate cancer cells metastasize to the bone where their interaction with osteoclasts and osteoblasts can lead to alterations in the structure of the bone. We determined whether the systemic administration of the bisphosphonate, zoledronate, could prevent bone lysis and halt the proliferation of human prostate cancer cells injected into the tibia of nude mice. Zoledronate did not affect the in vitro proliferation of human prostate cancer PC-3MM2 cells. The in vivo administration of zoledronate produced significant bone preservation but did not inhibit the progressive growth of PC-3MM2 cells. The systemic administration of STI571 (imatinib mesylate, Gleevec), an inhibitor of phosphorylation of the platelet-derived growth factor receptor, in combination with paclitaxel, produced apoptosis of tumor cells and bone- and tumor-associated endothelial cells. The systemic administration of zoledronate with STI571 and paclitaxel produced a significant preservation of bone structure, a decrease in tumor incidence and weight, and a decrease in incidence of lymph node metastasis. This therapeutic activity was correlated with inhibition of osteoclast function, inhibition of tumor cell proliferation, and induction of apoptosis in tumor-associated endothelial cells and tumor cells. Cancer is a heterogeneous disease that requires multimodality therapy. The present data recommend the combination of a bisphosphonate agent with protein tyrosine kinase inhibitor and an anticycling drug for the treatment of prostate cancer bone metastasis.     

Frequent administration of angiogenesis inhibitor TNP-470 (AGM-1470) at an optimal biological dose inhibits tumor growth and metastasis of metastatic human transitional cell carcinoma in the urinary bladder.

PURPOSE: The angiogenic inhibitor TNP-470 (AGM-1470, O-chloracetyl-carbamoyl fumagillol) has been reported to inhibit the growth of human transitional cell carcinoma (TCC) in the urinary bladder. However, it is still unknown whether TNP-470 inhibits metastasis of TCC. Here, we identify an efficient protocol using TNP-470, and optimize its antitumor and antimetastatic effects on human TCC in the urinary bladder. EXPERIMENTAL DESIGN: In vitro, the human metastatic TCC cell line 253J B-V and human umbilical vascular endothelial cells were treated with TNP-470, and examined for cell growth and protein production of angiogenic factors. To study in vivo effects of TNP-470, 253J B-V cells were implanted orthotopically into athymic nude mice. TNP-470 was administered in several dosing and scheduling regimens, and its effects on tumor growth, metastasis, intratumor neovascularization, and mRNA expression of angiogenic factors were determined in both nonestablished and established tumors. RESULTS: In vitro treatment with TNP-470 inhibited cell growth and production of basic fibroblast growth factor protein in 253J B-V and human umbilical vascular endothelial cells in a dose-dependent manner. In vivo daily administration of TNP-470 significantly inhibited tumor growth (P < 0.001), metastasis (P < 0.05), intratumor neovascularization (P < 0.005), and mRNA expression of basic fibroblast growth factor and MMP-9 (P < 0.005), in both nonestablished and established tumors. Increasing the daily dose did not increase the effect on tumor growth, metastasis, and angiogenesis; however, the drug-induced toxicity did increase in a dose-dependent manner. CONCLUSIONS: Frequent administration of TNP-470 at an optimal biological dose provided maximal antitumor and antimetastatic effects of human TCC of the urinary bladder. It may function by down-regulating angiogenic factors.     

Adenoviral-mediated gene therapy of human bladder cancer with antisense interleukin-8

We previously demonstrated the importance of interleukin-8 (IL-8) as a mediator of angiogenesis, tumorigenicity, and metastasis of transitional cell carcinoma (TCC) of the bladder. In the present study, we evaluated the feasibility of adenoviral mediated antisense IL-8 gene transfer (Ad IL-8-AS) as therapy for established TCC. In vitro, Ad IL-8-AS inhibited endothelial cell proliferation and enhanced endothelial cell apoptosis. The highly metastatic human TCC cell line 253J B-V(R) was implanted into the subcutis of athymic nude mice, and intralesional therapy with Ad IL-8-AS commenced when the tumors reached a diameter between 5 and 7 mm. Tumor growth was significantly inhibited compared with therapy in controls (saline and beta-galactosidase adenovirus). Ad IL-8-AS therapy decreased the in vivo expression of IL-8 and matrix metalloproteinase type 9 (MMP-9), reduced microvessel density, and enhanced endothelial cell apoptosis. These results indicate that Ad IL-8-AS therapy targets both tumor cells and host endothelial cells resulting in endothelial cell apoptosis and significant inhibition of tumor growth.     

Treatment of human metastatic transitional cell carcinoma of the bladder in a murine model with the anti-vascular endothelial growth factor receptor monoclonal antibody DC101 and paclitaxel.

Vascular endothelial cell growth factor (VEGF) regulates angiogenesis and metastasis of bladder cancer (transitional cell carcinoma, TCC) through binding to VEGF receptor-2 (VEGFR-2). In this study, we evaluated whether the anti-VEGFR monoclonal antibody (Mab) DC101 in combination with paclitaxel inhibited tumorigenesis, angiogenesis, and metastasis of human TCC growing within the bladder of athymic nude mice. In vivo therapy with Mab DC101 and paclitaxel induced significant regression of bladder tumors compared with either agent alone. Median bladder weights were reduced from 601 mg in untreated controls, 422 mg in mice treated with paclitaxel alone (P < 0.005), 361 mg in mice treated with DC101 alone (P < 0.005), and 113 mg in mice that received combination therapy (P < 0.0005). Only one of nine mice developed spontaneous lymph node metastasis after combined treatment, compared with seven of seven untreated controls (P < 0.0005), six of eight after DC101 (P < 0.01), and five of eight mice after paclitaxel (P < 0.05). Combined treatment with both paclitaxel and DC101 inhibited tumor-induced neovascularity compared with all other groups (P < 0.005), without altering the expression of VEGF or flk1. Mab DC101 and paclitaxel combined enhanced apoptosis in the tumor and endothelial cells compared with other treatment (P < 0.005). These studies indicate that Mab DC101, which blocks VEGFR-2 function, has significant efficacy against human TCC, especially when combined with the chemotherapeutic agent paclitaxel. The antitumor effect was mediated by inhibition of angiogenesis and induction of both tumor cell and endothelial cell apoptosis.     

Pathophysiology of bone metastases: how this knowledge may lead to therapeutic intervention

Bone metastases are common in many advanced cancers and are a clinically relevant source of skeletal morbidity. The bone mineral matrix contains numerous growth factors that are released during normal bone remodeling, providing a fertile microenvironment for tumor cell colonization and proliferation. Tumor cells then release a variety of growth factors that promote bone resorption and increase the risk of skeletal complications. Bisphosphonates are potent inhibitors of osteoclast activity that have demonstrated efficacy in the treatment of bone metastases. Bisphosphonates bind avidly to the bone matrix, are released during bone resorption, and are subsequently internalized by osteoclasts, where they interfere with biochemical pathways and induce osteoclast apoptosis. Bisphosphonates also antagonize osteoclastogenesis and promote the differentiation of osteoblasts. As a result, bisphosphonates inhibit tumor-induced osteolysis and reduce skeletal morbidity. Furthermore, preclinical studies suggest that bisphosphonates possess antitumor activity and can inhibit proliferation and induce apoptosis of tumor cell lines. In addition, zoledronic acid, a new-generation bisphosphonate, appears to inhibit tumor cell invasion of the extracellular matrix. These data suggest that zoledronic acid and other bisphosphonates may play a role in the reduction of skeletal tumor burden and the prevention of bone metastasis.     

Combination with third‐generation bisphosphonate (YM529) and interferon‐alpha can inhibit the progression of established bone renal cell carcinoma

The aim of this study was to investigate whether the third‐generation nitrogen‐containing bisphosphonate (YM529) can inhibit the progression of established bone renal cell carcinoma (RCC) and to elucidate its mechanism. Antiproliferative effect and apoptosis induction of RCC cells and mouse osteoclasts by YM529 and/or interferon‐alpha (IFN‐α) were evaluated in vitro using cell counting and in vivo using soft X‐ray, the TUNEL method and tartrate‐resistant acid phosphatase stain. For the in vivo study, male athymic BALB/cA Jc1‐nu nude mice bearing human RCC cell line RBM1‐IT4 cells were treated with YM529 and/or IFN‐α. The biological activity of osteoclasts was evaluated using the pit formation assay. The antiangiogenetic effect by YM529 and/or IFN‐α was analyzed using micro‐vessel density and in situ mRNA hybridization. Osteoclast number in bone tumors was decreased in YM529‐treated mouse. YM529 also inhibited osteoclast activity and proliferation in vitro, whereas basic fibroblast growth factor expressions and micro‐vessel density within tumors were inhibited by IFN‐α. Neither YM529 nor IFN‐α alone significantly inhibited the growth of established bone metastatic tumors. Combined treatment with YM529 and IFN‐α may be beneficial in patients with human RCC bone metastasis. Their effects are mediated by osteoclast recruitment inhibition and inactivation by YM529 and antiangiogenesis by IFN‐α.     

Gene therapy of human bladder cancer with adenovirus-mediated antisense basic fibroblast growth factor.

We previously investigated the role of basic fibroblast growth factor (bFGF) as a mediator of angiogenesis, tumorigenicity, and metastasis of transitional cell carcinoma (TCC) of the bladder. In the present study, we determined whether adenoviral-mediated antisense bFGF gene transfer therapy (Ad bFGF-AS) would inhibit TCCs growing in the subcutis of nude mice. In vitro, Ad bFGF-AS inhibited endothelial cell proliferation and enhanced apoptosis. The highly metastatic human TCC cell line 253J-BV(R) was implanted ectopically in the subcutis of athymic nude mice, and therapy was begun when the tumors reached a diameter between 5 and 7 mm. Intralesional therapy with Ad bFGF-AS decreased the in vivo expression of bFGF and matrix metalloproteinase type 9 mRNA and protein, and reduced microvessel density and enhanced endothelial cell apoptosis. Tumor growth was significantly inhibited by Ad bFGF-AS (mean, 58 mg) compared with controls [saline (mean, 562 mg), beta-galactosidase adenovirus (mean, 586 mg), and sense bFGF adenoviral therapy (Ad bFGF-S; mean, 3012 mg)]. These results suggest that Ad bFGF-AS therapy affects endothelial cells directly and tumor cells indirectly through down-regulation of bFGF and matrix metalloproteinase type 9, resulting in endothelial cell apoptosis and significant tumor growth inhibition. Furthermore, these studies confirm that bFGF expression is a valid target for the therapy of bladder cancer.     

Cilengitide inhibits metastatic bone colonization in a nude rat model

Integrins αvβ3 and αvβ5 are considered to play an important role in the pathogenesis of breast cancer bone metastases. This study investigates the effects of the αvβ3/αvβ5 integrin-specific inhibitor cilengitide during early metastatic bone colonization. The impact of cilengitide on the migration, invasion and proliferation of MDA-MB-231 human breast carcinoma cells as well as on bone resorption by osteoclasts was investigated in vitro. For in vivo experiments, nude rats were treated with cilengitide for 30 days starting one day after site-specific tumor cell inoculation in the hind leg, and the course of metastatic changes in bone was followed using flat-panel volumetric computed tomography (VCT) and magnetic resonance imaging (MRI). Vascular changes in bone metastases were investigated using dynamic contrast-enhanced (DCE-) MRI-derived parameters amplitude A and exchange rate coefficient kep. In vitro, cilengitide treatment resulted in a decrease in proliferation, migration and invasion of MDA-MB-231 cells, as well as of osteoclast activity. In vivo, the development of bone metastasis in the hind leg of rats was not prevented by adjuvant cilengitide treatment, but cilengitide reduced the volumes of osteolytic lesions and respective soft tissue tumors of developing bone metastases as assessed with VCT and MRI, respectively. DCE-MRI revealed significant changes in the A and kep parameters including decreased relative blood volume and increased vessel permeability after cilengitide treatment indicating vessel remodeling. In conclusion, during early pathogenic processes of bone colonization, cilengitide treatment exerted effects on tumor cells, osteoclasts and vasculature reducing the skeletal lesion size of experimental skeletal metastases.     

2-Methoxyestradiol suppresses osteolytic breast cancer tumor progression in vivo

2-Methoxyestradiol (2ME(2)), a physiologic metabolite of 17beta-estradiol (estrogen), has emerged as a promising cancer therapy because of its potent growth-inhibitory and proapoptotic effects on both endothelial and tumor cells. 2ME(2) also suppresses osteoclast differentiation and induces apoptosis of mature osteoclasts, and has been shown to effectively repress bone loss in an animal model of postmenopausal osteoporosis. Given these observations, we have examined whether 2ME(2) could effectively target metastasis to bone, osteolytic tumors, and soft tissue tumors. A 4T1 murine metastatic breast cancer cell line was generated that stably expressed Far Red fluorescence protein (4T1/Red) to visualize tumor development and metastasis to bone. In an intervention study, 4T1/Red cells were injected into bone marrow of the left femur and the mammary pad. In the latter study, 2ME(2) (10, 25, and 50 mg/kg/d) treatment began on the same day as surgery and was continued for the 16-day duration of study. Tumor cell growth and metastasis to bone were monitored and bone volume was determined by micro-computed tomography. 2ME(2) inhibited tumor growth in soft tissue, metastasis to bone, osteolysis, and tumor growth in bone, with maximum effects at 50 mg/kg/d. Furthermore, tumor-induced osteolysis was significantly reduced in mice receiving 2ME(2). In vitro, 2ME(2) repressed osteoclast number by inducing apoptosis of osteoclast precursors as well as mature osteoclasts. Our data support the conclusion that 2ME(2) could be an important new therapy in the arsenal to fight metastatic breast cancer.     

Synergistic inhibition of tumor growth and metastasis by combined treatment with TNP-470 and docetaxel in a human prostate cancer PC-3 model

TNP-470, a potent inhibitor of angiogenesis, was reported to synergistically enhance the antitumor effects of cytotoxic agents. The objective of this study was to evaluate the effectiveness of combined treatment with TNP-470 and docetaxel both in vitro and in vivo using androgen-independent human prostate cancer PC-3 cells. The in vitro growth-inhibitory and apoptotic effects of docetaxel and/or TNP-470 on PC-3 cells were assessed using MTT and TUNEL assays. The combined effect of docetaxel and TNP-470 therapy after subcutaneous and orthotopic injection of PC-3 cells into athymic nude mice was evaluated. In vivo effects of this combined regimen on PC-3 tumors were analyzed by the TUNEL assay and immunohistochemical staining of CD31 to quantify microvessel density (MVD). Combined treatment with TNP-470 and docetaxel synergistically inhibited PC-3 cell growth in vitro through the enhanced induction of apoptotic cell death compared with treatment with either agent alone, a result explained, at least in part, by the down-regulation as well as phosphorylation of potential anti-apoptotic genes, Bcl-2 and Bcl-XL. Combined treatment with TNP-470 and docetaxel synergistically suppressed subcutaneous PC-3 tumor growth compared with treatment with either agent alone. Furthermore, this combined regimen significantly inhibited orthotopic PC-3 tumor growth and reduced the incidence of lymph node metastasis. Immunohistochemical analysis of the subcutaneous tumor after each treatment demonstrated that administration of docetaxel as well as TNP-470 significantly induced apoptotic cell death; in contrast, a significant reduction in MVD was observed only after TNP-470. These findings suggest that docetaxel and TNP-470 act synergistically to inhibit PC-3 tumor growth and metastasis, by enhancing apoptosis and suppressing angiogenesis.     

Osteoprotegerin inhibits osteolysis and decreases skeletal tumor burden in syngeneic and nude mouse models of experimental bone metastasis

Certain malignancies, including breast cancer, frequently metastasize to bone, where the tumor cells induce osteoclasts to locally destroy bone. Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor family, is a negative regulator of osteoclast differentiation, activation, and survival. We tested the ability of recombinant OPG to inhibit tumor-induced osteoclastogenesis, osteolysis, and skeletal tumor burden in two animal models. In a syngeneic model, mouse colon adenocarcinoma (Colon-26) cells were injected into the left ventricle of mice. Treatment with OPG dose-dependently decreased the number and area of radiographically evident lytic bone lesions, which, at the highest dose, were undetectable. Histologically, OPG also decreased skeletal tumor burden and tumor-associated osteoclasts. In a nude mouse model, OPG treatment completely prevented radiographic osteolytic lesions caused by human MDA-MB-231 breast cancer cells. Histologically, OPG decreased skeletal tumor burden by 75% and completely eradicated MDA tumor-associated osteoclasts. In both models, OPG had no effect on metastatic tumor burden in a panel of soft tissue organs. These data indicate that OPG may be an effective therapy for preventing osteolysis and decreasing skeletal tumor burden in patients with bone metastasis.     

Propriétés antitumorales du bisphosphonate zolédronate et implications thérapeutiques potentielles en clinique

Zoledronate, just as other bisphosphonates, inhibit osteoclast mediated bone resorption. This is the reason why they are used in the treatment of bone metastasis, in order to block osteolysis. Zoledronate and some other bisphosphonates (clodronate, pamidronate, ibandronate, alendronate, risédronate, minodronate) also exhibit antitumor properties in vitro. They act directly on tumor cells by blocking tumor cell adhesion, invasion and proliferation, and by inducing tumor cell apoptosis. However, their high bone mineral affinity decreases their bioavailability to a significant extent and, thus, should weaken their in vivo antitumor potential. Despite of this, several studies (most of them being performed with zoledronate) show that bisphosphonates have an in vivo antitumor activity. This review focuses on zoledronate and on results obtained in several experimental models showing that this bisphosphonate interferes with the growth of tumors and metastases which are thriving in tissues others than the skeletal tissue. The significance of these findings is discussed in the light of several ongoing clinical trials which examine the benefits of using zoledronate and other bisphosphonates in the adjuvant treatment of cancers at an early stage of the disease.     

The inhibition of RANKL/RANK signaling by osteoprotegerin suppresses bone invasion by oral squamous cell carcinoma cells

Oral squamous cell carcinomas (OSCCs) are malignant tumors that frequently invade the maxilla and mandibular bone. However, the molecular mechanisms underlying bone invasion by OSCC are unclear. Recent studies showed that receptor activator of nuclear factor κB (RANK) was expressed not only in osteoclast precursors but also in tumor cells. Therefore, we examined whether RANK ligand (RANKL)/RANK signaling regulates bone invasion by OSCC cells in vivo and in vitro. We first injected human OSCC B88 cells into the masseter region of nude mice. Mice were treated for 3 weeks with osteoprotegerin (OPG), the decoy receptor for RANKL. Treatment with OPG decreased bone invasion by B88 cells, reduced the number of osteoclasts and increased B88 cell apoptosis. However, OPG did not affect apoptosis and proliferation in B88 cells in vitro, suggesting that the effects of OPG on apoptosis in B88 cells are restricted in a bone environment. RANK was expressed in the B88 cells and in OSCC cells from patients. RANKL induced NF-κB activation and extracellular signal-regulated kinase phosphorylation in B88 cells and enhanced B88 cell migration in a modified chemotaxis chamber equipped with a gelatin-coated filter. OPG inhibited RANKL-induced NF-κB activation, extracellular signal-regulated kinase phosphorylation and cell migration. Our data clearly indicate that RANKL/RANK inhibition suppresses bone invasion by inhibiting osteoclastogenesis and cancer cell migration and by inducing apoptosis of cancer cells via indirect anticancer action in vivo.     

miR‐92a‐3p encapsulated in bone metastatic mammary tumor cell–derived extracellular vesicles modulates mature osteoclast longevity

Aberrant osteoclast formation and activation are the hallmarks of osteolytic metastasis. Extracellular vesicles (EVs), released from bone metastatic tumor cells, play a pivotal role in the progression of osteolytic lesions. However, the mechanisms through which tumor cell–derived EVs regulate osteoclast differentiation and function have not been fully elucidated. In this study, we found that 4T1 bone metastatic mouse mammary tumor cell–derived EVs (4T1‐EVs) are taken up by mouse bone marrow macrophages to facilitate osteoclastogenesis. Furthermore, treatment of mature osteoclasts with 4T1‐EVs promoted bone resorption, which was accompanied by enhanced survival of mature osteoclasts through the negative regulation of caspase‐3. By comparing the miRNA content in 4T1‐EVs with that in 67NR nonmetastatic mouse mammary tumor cell–derived EVs (67NR‐EVs), miR‐92a‐3p was identified as one of the most enriched miRNAs in 4T1‐EVs, and its transfer into mature osteoclasts significantly reduced apoptosis. Bioinformatic and Western blot analyses revealed that miR‐92a‐3p directly targeted phosphatase and tensin homolog (PTEN) in mature osteoclasts, resulting in increased levels of phospho‐Akt. Our findings provide novel insights into the EV‐mediated regulation of osteoclast survival through the transfer of miR‐92a‐3p, which enhances mature osteoclast survival via the Akt survival signaling pathway, thus promoting bone resorption.     

Inhibition of tumorigenicity and metastasis of human bladder cancer growing in athymic mice by interferon-beta gene therapy results partially from various antiangiogenic effects including endothelial cell apoptosis.

We determined whether the IFN-beta gene could suppress angiogenesis, tumor growth, and metastasis of human bladder transitional cell carcinoma. The highly tumorigenic and metastatic 253J B-V(R) human bladder transitional cell carcinoma (TCC) cell line (resistant to the antiproliferative effects of IFN-beta) was infected in vitro with adenoviral beta-galactosidase (Ad-LacZ), murine adenoviral IFN-beta (Ad-mIFN-beta), or human adenoviral IFN-beta (Ad-hIFN-beta) and implanted into the bladders of athymic nude mice. Ad-mIFN-beta and Ad-hIFN-beta were used because of the species specificity of IFN-beta. The transient production of mIFN-beta and hIFN-beta from the infected 253JB-V(R) tumor cells significantly inhibited tumorigenicity and spontaneous lymph node metastasis. Subsequently, the 253J B-V(R) cells were implanted into the subcutis of athymic nude mice, and established tumors were treated by direct intratumoral injection with Ad-mIFN-beta, Ad-hIFN-beta, Ad-LacZ, or PBS. By in situ hybridization (ISH) and immunohistochemical analysis (IHC), expression of hIFN-beta and mIFN-beta mRNA and protein within the tumors was demonstrated after Ad-hIFN-beta and Ad-mIFN-beta gene therapy, respectively. The therapy also induced necrosis in both the Ad-mIFN-beta- and Ad-hIFN-beta-treated tumors. IHC revealed decreased tumor cell proliferation and the sequestration of activated macrophages within the tumors after Ad-mIFN-beta therapy. In addition, the expression of the proangiogenic factors bFGF, and MMP-9 protein (by IHC) was significantly down-regulated by Ad-hIFN-beta gene therapy. Double-immunofluorescent IHC for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) and CD-31 demonstrated tumor and endothelial cell apoptosis in those tumors treated with Ad-hIFN-beta gene therapy. Tumor-induced angiogenesis, as determined by the microvessel density, was decreased in tumors treated with both Ad-mIFN-beta and Ad-hIFN-beta. These data suggest that the inhibition of tumorigenicity and the metastasis of the 253J B-V(R) cells after infection with Ad-IFN-beta is caused by the inhibition of angiogenesis and the activation of host effector cells.     

Bone marrow mesenchymal stem cells provide an alternate pathway of osteoclast activation and bone destruction by cancer cells

The bone is the third most common site of cancer metastasis. To invade the bone, tumor cells produce osteoclast-activating factors that increase bone resorption by osteoclasts. Here we report that human neuroblastoma cells that form osteolytic lesions in vivo do not produce osteoclast-activating factors but rather stimulate osteoclast activity in the presence of human bone marrow mesenchymal stem cells. This alternative pathway of osteoclast activation involves a nonadhesive interaction between neuroblastoma cells and bone marrow mesenchymal stem cells. Stimulated bone marrow mesenchymal stem cells express markedly increased levels of interleukin-6, which is then responsible for osteoclast activation. This report describes a critical role of bone marrow mesenchymal stem cells in bone destruction in cancer.     

RANKL inhibition combined with tamoxifen treatment increases anti-tumor efficacy and prevents tumor-induced bone destruction in an estrogen receptor-positive breast cancer bone metastasis model

Tumor cells in bone can induce the activation of osteoclasts, which mediate bone resorption and release of growth factors and calcium from the bone matrix, resulting in a cycle of tumor growth and bone breakdown. Targeting the bone microenvironment by the inhibition of RANKL, an essential mediator of osteoclast function, not only prevents tumor-induced osteolysis but also decreases skeletal tumor burden in preclinical models. The inhibition of skeletal tumor progression after the inhibition of osteoclasts is via interruption of the "vicious cycle" of tumor/bone interactions. The majority of breast cancer patients at risk for bone metastases harbor estrogen receptor-positive (ER+) tumors. We developed a mouse model for ER+ breast cancer bone metastasis and evaluated the effect of RANKL inhibition on tumor-induced osteolysis and skeletal tumor growth both alone and in combination with tamoxifen. Luciferase-labeled MCF-7 cells (MCF-7Luc) formed metastatic foci in the hind limbs following intracardiac injection and caused mixed osteolytic/osteoblastic lesions. RANKL inhibition by OPG-Fc treatment blocked osteoclast activity and prevented tumor-induced osteolysis, as well as caused a marked decrease in skeletal tumor burden. Tamoxifen as a single agent reduced MCF-7Luc tumor growth in the hind limbs. In a combination experiment, OPG-Fc plus tamoxifen resulted in significantly greater tumor growth inhibition than either single agent alone. Histologic analysis revealed a decrease in the proliferation of tumor cells by both single agents, which was enhanced in the combination treatment. Upon treatment with OPG-Fc alone or in combination with tamoxifen, there was a complete absence of osteolytic lesions, demonstrating the ability of RANKL inhibition to prevent skeletal related morbidity in an ER+ model. The combination approach of targeting osteoclasts and the bone microenvironment by RANKL inhibition and the tumor directly via hormonal therapy may provide additional benefit to reducing skeletal tumor progression in ER+ breast cancer patients.