In order to assess the effects of treatment with PC61 in vivo, we analyzed the presence of Foxp3+ CD4+ Tregs infiltrating the GBM mass as well as in the draining lymph nodes and the spleen after intraperitoneal injection of PC61 (days 15 and 24) or the rat IgG1 isotype control (day 15 days) into tumor bearing mice. The gene discussed is CD4; the disease is glioblastoma.