Initial characterization of FOXP3 blockade in brain tumor model using gene therapy vectors

S.SAGRIPANTI; M.IMSEN; F.ZANETTI; A. NICOLA CANDIA; A.ABT; C.ZUCCATO; M.CANDOLFI; A.ASAD; M.GARCIA FALLIT; A. SEILICOVICH

Mar del Plata

Congreso; LXIX Reunión de la Sociedad Argentina de Investigación Clínica; 2019

Our previous results indicate that systemic administration of a cell penetrating peptide (P60) that inhibits Foxp3, a transcription factor required for Treg function, improves the efficacy of antitumor vaccines in experimental breast cancer models. In order to develop a gene therapeutic strategy to deliver P60 in vivo, we have generated an adenovector that encodes the P60 sequence as well as a fluorescent reporter gene dTomato (Ad.P60.dTomato), which successfully transduced breast tumor cells in vitro and in vivo. Here we aimed to perform an initial characterization of Ad.P60.dTomato in experimental glioblastoma. This vector successfully transduced glioblastoma cells in vitro and in vivo in mice bearing intracranial GL26 syngeneic tumors that received intratumor injections of Ad.P60.dTomato or its control vector (6x107 pfus) 21 d post-tumor inoculation. Expression of d-Tomato was also detected in the normal mouse brain 3 and 5 days post-injection of Ad.P60.dTomato. We next injected Ad.P60.dTomato in intracranial GL26 tumors growing in transgenic C57BL/6 mice that express Foxp3 fused to fluorescent GFP protein, in order to easily detect Tregs by flow citometry. Seven days after adenovector injection we observed a significant decrease in the number of tumor infiltrating Tregs in mice treated with Ad.P60.dTomato (p