Osteosacarcoma (OS) lung metastases are often resistant to chemotherapy. Most anticancer drugs are administered systemically. In many cases this is followed by dose-dependent toxicity, which may not allow the achievement of therapeutic levels in lungs to eradicate metastases. We determined the efficacy of gemcitabine (GCB) by administering it directly to the lungs via aerosol and studied the role of the Fas pathway in response to the therapy. We used 2 osteosarcoma lung metastases animal models: human LM7 cells that form lung metastases in mice following intravenous injection and murine LM8 cells, which grows subcutaneously in mice and spontaneously metastasize to the lung. Treatment was initiated when the presence of lung metastases had been established. Aerosol GCB inhibited the growth of lung metastases in mice. Intraperitoneal GCB administration at similar dosage had no effect on lung metastases. Besides its direct effect on lung metastases, aerosol GCB suppressed the growth of subcutaneous LM8 tumor. Histopathological examination of mice receiving aerosol GCB showed no evidence of toxicity. Lungs are distinguished from other tissues by the constitutive expression of FasL. Since exposure of tumor cells to GCB upregulated Fas expression, we hypothesized that the susceptibility of the tumor cells to ligandinduced cell death by resident lung cells may be increased. Therefore, the Fas pathway may contribute to the therapeutic effect of aerosol GCB. ' 2005 Wiley-Liss, Inc. Key words: Fas; lung environment; toxicityThe most common site for metastatic spread of OS is the lungs. Patients with OS lung metastases have a poor prognosis with limited therapeutic options. Metastatic and relapsed disease is often resistant to salvage chemotherapy. Our laboratory's goal is to identify new therapeutic approaches for these patients.GCB has been shown to have limited efficacy in the treatment of advanced sarcomas, including OS, 1 but this may be explained in part because systemic administration of GCB does not achieve therapeutic levels in the lungs. We hypothesized that targeted delivery of GCB to the lungs via aerosol will circumvent this problem, yielding a higher drug concentration in the area of the tumor and offer a unique therapeutic opportunity for patients with lung metastases. Indeed, we previously demonstrated that the intranasal administration of GCB at a dose 8-fold lower than the i.v. dose induced the regression of established OS lung metastases. 2 However, the intranasal delivery of drugs to the lungs in humans is not ideal as the drugs will not reach the peripheral regions of the lungs where metastases often develop.Aerosol delivery can bypass this limitation. The clinical feasibility of aerosol drug delivery has been demonstrated with both 9-nitrocamptothecin and GM-CSF. 3,4 In our study, we investigated the efficacy of aerosol GCB in treating OS lung metastases using 2 OS animal model. Aerosol GCB significantly inhibited the growth of primary tumors and of established lung metastases and also prevented metast...

Purpose: Pulmonary metastases continue to be a significant problem in osteosarcoma. Apoptosis dysfunction is known to influence tumor development. Fas (CD95, APO-1)/FasL is one of the most extensively studied apoptotic pathways. Because FasL is constitutively expressed in the lung, cells that express Fas should be eliminated by lung endothelium. Cells with low or no cell surface Fas expression may be able to evade this innate defense mechanism. The purpose of these studies was to evaluate Fas expression in osteosarcoma lung metastases and the effect of gemcitabine on Fas expression and tumor growth. Experimental Design and Results: Using the K7M2 murine osteosarcoma model, Fas expression was quantified using immunohistochemistry. High levels of Fas were present in primary tumors, but no Fas expression was present in actively growing lung metastases. Blocking the Fas pathway using Fas-associated death domain dominant-negative delayed tumor cell clearance from the lung and increased metastatic potential. Treatment of mice with aerosol gemcitabine resulted in increased Fas expression and subsequent tumor regression. Conclusions: We conclude that corruption of the Fas pathway is critical to the ability of osteosarcoma cells to grow in the lung. Agents such as gemcitabine that up-regulate cell surface Fas expression may therefore be effective in treating osteosarcoma lung metastases. These data also suggest that an additional mechanism by which gemcitabine induces regression of osteosarcoma lung metastases is mediated by enhancing the sensitivity of the tumor cells to the constitutive FasL in the lung.

9-NC liposome aerosol was strikingly effective in the treatment of three human cancer xenografts growing subcutaneously over the thorax in nude mice at doses much smaller than those traditionally used in mice administered by other routes.

Purpose: The process of metastasis requires the single tumor cell that seeds the metastatic clone to complete a complex series of steps. Identifying factors responsible for these steps is essential in developing and improving targeted therapy for metastasis. Resistance to receptor-mediated cell death, such as the Fas/Fas ligand pathway, is one mechanism commonly exploited by metastatic cell populations.Experimental Design and Results: LM7, a subline of the SAOS human osteosarcoma cell line with low Fas expression, was selected for its high metastatic potential in an experimental nude mouse model. When transfected with the full-length Fas gene (LM7-Fas), these cells expressed higher levels of Fas than the parental LM7 cells or LM7-neo control-transfected cells. These cells were also more sensitive to Fas-induced cell death than controls. When injected intravenously into nude mice, the LM7-Fas cell line produced a significantly lower incidence of tumor nodules than control cell lines. Lung weight and tumor nodule size were also decreased in those mice injected with LM7-Fas. Levels of Fas were quantified in osteosarcoma lung nodules from 17 patients. Eight samples were Fas negative, whereas the remaining 9 were only weakly positive compared with normal human liver (positive control).Conclusions: Our results demonstrate that altering Fas expression can impact the metastatic potential of osteosarcoma cells. We conclude that the increase of Fas on the surface of the LM7 osteosarcoma cells increased their sensitivity to Fas-induced cell death in the microenvironment of the lung, where Fas ligand is constitutively expressed. Thus, loss of Fas expression is one mechanism by which osteosarcoma cells may evade host resistance mechanisms in the lung, increasing metastatic potential. Fas may therefore be a new therapeutic target for osteosarcoma.