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Receptor activator for nuclear factor-kappa B ligand (RANKL) is an essential mediator of osteoclastogenesis. We hypothesized that administration of soluble RANKL to mice would result in high turnover and deleterious effects on both cortical and trabecular bone. For 10 days, 10-week-old C57BL/6J female mice (n = 12/group) were given twice-daily subcutaneous injections of human recombinant RANKL (0.4 or 2 mg/kg/day) or inert vehicle (VEH). Bone turnover was greatly accelerated by RANKL, as evidenced by the 49-84% greater levels of serum TRAP-5b (bone resorption marker) and 300-400% greater levels of serum alkaline phosphatase (bone formation marker). RANKL resulted in significantly greater endocortical bone erosion surface (79-83%) and periosteal bone formation rate (64-87%) vs. VEH. Microcomputed tomographic (microCT) analysis of the proximal tibia indicated a reduction in trabecular volume fraction (-84%) for both doses of RANKL. Cortical bone geometry and strength were also negatively influenced by RANKL. MicroCT analysis of the femoral diaphysis indicated significantly lower cortical bone volume (-10% to -13%) and greater cortical porosity (8-9%) relative to VEH. Biomechanical testing of the femur diaphysis revealed significantly lower maximum bending load (-19% to -25%) vs. VEH. Bone strength remained correlated with bone mass, independent of RANKL stimulation of bone turnover. These findings are consistent with the hypothesis that soluble RANKL could be an important etiologic factor in pathologic bone loss. RANKL also has potential utility as a model for studying the consequences of high bone turnover on bone quality and strength in animals. [ABSTRACT FROM AUTHOR]

Multiple antitumor modalities may be necessary to overcome lung tumor-mediated immunosuppression and effectively treat non-small cell lung cancer (NSCLC). To evaluate a multimodality gene therapy approach for control of local tumor growth, a weakly immunogenic murine alveolar cell carcinoma, L1C2, was transduced with either the interleukin-7/hygromycin-herpes simplex thymidine kinase (IL-7/HyHSVtk) internal ribosome entry site (IRES) retroviral vector or a vector containing the HyHSVtk, but not the IL-7 gene. Of the many cytokines available for gene transfer, IL-7 was chosen for these studies because it both stimulates CTL responses and down-regulates tumor production of the immunosuppressive peptide TGF-β. Following selection in hygromycin, IL-7 transduction was confirmed by ELISA. Clones produced 1.25 to 10 ng of IL-7/ml/106 cells per 24 h. In vitro, genetically modified tumor cells were significantly more sensitive to ganciclovir (GCV) than unmodified parental tumor cells. The in vivo growth of ex vivo modified L1C2 cells was evaluated. There was a dose–response relationship between the amount of IL-7 secreted in vitro and the growth of genetically modified murine tumor in vivo. Transduced tumor cells regressed in mice following GCV therapy. Although ex vivo gene modification of tumor cells led to complete resolution of the tumor following implantation in vivo, IL-7 and HSVtk gene modified tumor cells were not effective in treating established parental tumors. However when 5 × 105 bone marrow-derived, in vitro activated dendritic cells (DC) were administered in combination with transduced tumor and GCV, 5 day old established tumors were eradicated in 80% of mice. These studies suggest that multicomponent vaccines may facilitate improved host responses by replacing host immune deficits and thus could have a role in adjuvant therapy and local control of NSCLC. [ABSTRACT FROM AUTHOR]