Journal Article

MDA-MB-231-D3H2Ln, IVIS, Bioluminescence

Cellular senescence acts as a barrier to cancer progression, and microRNAs (miRNAs) are thought to be potential senescence regulators. However, whether senescence-associated miRNAs (SA-miRNAs) contribute to tumor suppression remains unknown. Here, we report that miR-22, a novel SA-miRNA, has an impact on tumorigenesis. miR-22 is up-regulated in human senescent fibroblasts and epithelial cells but down-regulated in various cancer cell lines. miR-22 overexpression induces growth suppression and acquisition of a senescent phenotype in human normal and cancer cells. miR-22 knockdown in presenescent fibroblasts decreased cell size, and cells became more compact. miR-22-induced senescence also decreases cell motility and inhibits cell invasion in vitro. Synthetic miR-22 delivery suppresses tumor growth and metastasis in vivo by inducing cellular senescence in a mouse model of breast carcinoma. We confirmed that CDK6, SIRT1, and Sp1, genes involved in the senescence program, are direct targets of miR-22. Our study provides the first evidence that miR-22 restores the cellular senescence program in cancer cells and acts as a tumor suppressor.

Journal Article

MDA-MB-231-D3H2Ln, IVIS, Bioluminescence

Tumor progression is associated with the release of signaling substances from the primary tumor into the bloodstream. Tumor-derived cytokines are known to promote the mobilization and the recruitment of cells from the bone marrow, including endothelial progenitor cells (EPC). Here, we examined whether such paracrine influence could also influence the capacity of EPC to interfere with circulating metastatic cells. We therefore consecutively injected EPC pre-stimulated by tumor conditioned medium (CM-EPC) and luciferase-expressing B16 melanoma cells to mice. A net decrease in metastases spreading (vs non-stimulated EPC) led us to carry out a 2D-DIGE proteomic study to identify possible mediators of EPC-driven protection. Among 33 proteins exhibiting significant changes in expression, SPARC presented the highest induction after EPC exposure to CM. We then showed that contrary to control EPC, SPARC-silenced EPC were not able to reduce the extent of metastases when injected with B16 melanoma cells. Using adhesion tests and the hanging drop assay, we further documented that cell-cell interactions between CM-EPC and melanoma cells were promoted in a SPARC-dependent manner. This interaction led to the engulfment of melanoma cells by CM-EPC, a process prevented by SPARC silencing and mimicked by recombinant SPARC. Finally, we showed that contrary to melanoma cells, the pro-metastatic human breast cancer cell line MDA-MB231-D3H2 reduced SPARC expression in human EPC and stimulated metastases spreading. Our findings unravel the influence of tumor cells on EPC phenotypes through a SPARC-driven accentuation of macrophagic capacity associated with limitations to metastatic spread.

Journal Article

MDA-MB-231-D3H2Ln, IVIS, Bioluminescence, Activins/*metabolism; Animals; Bone Neoplasms/*complications/pathology/physiopathology/secondary; Bone Resorption/*etiology/pathology/physiopathology/*prevention & control; Calcification, Physiologic/drug effects; Cell Line, Tumor; HEK293 Cells; Humans; Mice; Multiple Myeloma/complications/pathology/physiopathology; Neoplasm Transplantation; Organ Size/drug effects; Osteoblasts/drug effects/pathology; *Osteogenesis/drug effects; Osteolysis/blood/complications/physiopathology/prevention & control; Paraproteins/metabolism; Recombinant Fusion Proteins/pharmacology; *Signal Transduction/drug effects; Survival Analysis; Tumor Burden/drug effects

Cancers that grow in bone, such as myeloma and breast cancer metastases, cause devastating osteolytic bone destruction. These cancers hijack bone remodeling by stimulating osteoclastic bone resorption and suppressing bone formation. Currently, treatment is targeted primarily at blocking bone resorption, but this approach has achieved only limited success. Stimulating osteoblastic bone formation to promote repair is a novel alternative approach. We show that a soluble activin receptor type IIA fusion protein (ActRIIA.muFc) stimulates osteoblastogenesis (p < .01), promotes bone formation (p < .01) and increases bone mass in vivo (p < .001). We show that the development of osteolytic bone lesions in mice bearing murine myeloma cells is caused by both increased resorption (p < .05) and suppression of bone formation (p < .01). ActRIIA.muFc treatment stimulates osteoblastogenesis (p < .01), prevents myeloma-induced suppression of bone formation (p < .05), blocks the development of osteolytic bone lesions (p < .05), and increases survival (p < .05). We also show, in a murine model of breast cancer bone metastasis, that ActRIIA.muFc again prevents bone destruction (p < .001) and inhibits bone metastases (p < .05). These findings show that stimulating osteoblastic bone formation with ActRIIA.muFc blocks the formation of osteolytic bone lesions and bone metastases in models of myeloma and breast cancer and paves the way for new approaches to treating this debilitating aspect of cancer.

Journal Article

Xen36, Xen 36, Staphylococcus aureus Xen36, IVIS, Animals; Arthroplasty; Biofilms/growth & development; Bone Wires/microbiology; Interleukin-1beta/*metabolism; Male; Mice; Mice, Congenic; Mice, Inbred C57BL; Myeloid Differentiation Factor 88/metabolism; Neutrophil Infiltration; Prosthesis-Related Infections/*immunology/metabolism; Staphylococcal Infections/*immunology/metabolism; Staphylococcus aureus; Toll-Like Receptor 2/*metabolism

MyD88 is an adapter molecule that is used by both IL-1R and TLR family members to initiate downstream signaling and promote immune responses. Given that IL-1beta is induced after Staphylococcus aureus infections and TLR2 is activated by S. aureus lipopeptides, we hypothesized that IL-1beta and TLR2 contribute to MyD88-dependent protective immune responses against post-arthroplasty S. aureus infections. To test this hypothesis, we used a mouse model of a post-arthroplasty S. aureus infection to compare the bacterial burden, biofilm formation and neutrophil recruitment in IL-1beta-deficient, TLR2-deficient and wild-type (wt) mice. By using in vivo bioluminescence imaging, we found that the bacterial burden in IL-1beta-deficient mice was 26-fold higher at 1 day after infection and remained 3- to 10-fold greater than wt mice through day 42. In contrast, the bacterial burden in TLR2-deficient mice did not differ from wt mice. In addition, implants harvested from IL-1beta-deficient mice had more biofilm formation and 14-fold higher adherent bacteria compared with those from wt mice. Finally, IL-1beta-deficient mice had approximately 50% decreased neutrophil recruitment to the infected postoperative joints than wt mice. Taken together, these findings suggest a mechanism by which IL-1beta induces neutrophil recruitment to help control the bacterial burden and the ensuing biofilm formation in a post-surgical joint.

Journal Article

Xen36, Xen 36, Staphylococcus aureus Xen36, IVIS

Wear of metal-on-metal (cobalt-chromium, Co-Cr particles) and metal-on-polyethylene (ultra-high-molecular-weight polyethylene, UHMWPE particles) bearing surfaces in hip prostheses is a major problem in orthopedics. This study aimed to compare the influence of Co-Cr and UHMWPE particles on the persistence of infection. Bioluminescent Staphylococcus aureus Xen36 were injected in air pouches prepared in subcutaneous tissue of immuno-competent BALB/c mice (control), as a model for the joint space, in the absence or presence of Co-Cr or UHMWPE particles. Bioluminescence was monitored longitudinally up to 21 days, corrected for absorption and reflection by the particles and expressed relative to the bioluminescence found in the presence of staphylococci only. After termination, air pouch fluid and air pouch membrane were cultured and histologically analyzed. Bioluminescence was initially lower in mice exposed to UHMWPE particles with staphylococci than in mice injected with staphylococci only, possibly because UHMWPE particles initially stimulated a higher macrophage presence in murine air pouch membranes. For mice exposed to Co-Cr particles with staphylococci, bioluminescence was observed to be higher in two out of six animals compared to the presence of staphylococci alone. In the majority of mice, infection risk in the absence or presence of Co-Cr and UHMWPE particles appeared similar, assuming that the longevity of an elevated bioluminescence is indicative of a higher infection risk. However, the presence of Co-Cr particles yielded a higher bioluminescence in two out of six mice, possibly because the macrophage degradative function was hampered by the presence of Co-Cr particles. (c) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.