RESUMEN
Neo-vascular targeting by cationic colloidal carriers enables to realize an innovative approach for tumor therapy. EndoTag-2 is a novel vascular targeting agent, comprising the mammalian topoisomerase I inhibitor camptothecin in its carboxylate form complexed to cationic lipid (cationic lipid complexed camptothecin). Here we studied tumor vascular targeting properties, antitumoral effects and mode of action of EndoTag-2. Tumor vascular targeting properties of fluorescently labelled EndoTag-2 were investigated by in vivo microscopy using A-MEL-3 tumors grown in the dorsal skinfold chamber preparation and by fluorescence histology of s.c. LLC-1 carcinomas. Therapeutic effects have been investigated in the s.c. LLC-1 carcinoma model and the L3.6pl human pancreatic cancer model implanted orthotopically in athymic nude mice. Antivascular effects have been studied by histological investigation of tumor microvessel density and non invasive investigation of tumor blood flow by dynamic contrast enhanced MRI imaging (DCE-MRI). EndoTag-2 selectively targeted tumor microvessels as confirmed by quantitative fluorescence microscopy. Compared to controls EndoTag-2 revealed remarkable antitumoral efficiency in s.c. LLC-1 carcinomas implanted in C57/Bl6 mice. Growth and metastasis of orthotopic L3.6pl human pancreatic tumors was significantly inhibited by EndoTag-2 treatment. Quantitative analysis of tumor microvessel density revealed significant reduction of microvessel density in lewis lung carcinomas up to 50%. DCE-MRI confirmed significant reduction of intratumoral vascular volume as well as tumor perfusion upon EndoTag-2 treatment. In conclusion this study shows that cationic lipid complexed camptothecin (EndoTag-2) is a markedly active antitumor agent based on an innovative vascular targeting approach.
Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Camptotecina/farmacología , Cationes , Neoplasias Pancreáticas/inmunología , Neoplasias Pancreáticas/terapia , Animales , Línea Celular Tumoral , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Desnudos , Microscopía Fluorescente , Trasplante de Neoplasias , Neovascularización Patológica , Neoplasias Pancreáticas/patologíaRESUMEN
De novo malignancies and recurrence of tumors are some of the biggest threats to allograft recipients subjected to chronic immunosuppression. FTY720, a synthetic myriocin analogue, is an immunosuppressant that induces apoptosis of activated lymphocytes and prevents infiltration of lymphocytes into allografts, thereby prolonging allograft survival in a dose-dependent manner. Additionally, FTY720 was shown to prevent tumor growth and metastasis. Therefore, we examined the effect of FTY720 on angiogenesis in a HUVEC spheroid model. To substantiate our in vitro findings the effect of FTY720 was also tested in C57/B16 mice subcutaneously injected with Lewis Lung Carcinoma (LLC1) cells. After establishment of a palpable tumor the animals were treated daily with either saline or 1, 5, or 10 mg/kg FTY720. Subsequently, the tumor size was measured, periodically. In our experiments FTY720 showed a strong antiangiogenic effect, overcoming the stimulating effect of VEGF (20 ng/mL) even at subnanomolar concentrations. In vivo, FTY720 showed a dose-dependent inhibition of subcutaneous tumors, and the tumor size of animals treated with 10 mg/kg FTY720 was less than half of the size of tumors in control animals. In conclusion, FTY-720 demonstrated a strong antiangiogenic effect in vitro and a substantial antitumor effect in vivo. Presumably, the stabilizing effect of surrounding pericytes limits the effect of FTY720 in our mouse model. Therefore, a combination of FTY720 with an mTOR inhibitor might be the most favorable immunosuppressive drug combination for allograft recipients at risk for tumor development.