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...