PRF1 and glioblastoma: In support of the dual role of these pathways in Treg suppression function, Choi et al. reported that human Tregs can use the granzyme–perforin to kill glioblastoma cells when redirected by a bispecific antibody, demonstrating the potential for granzyme B and perforin contribution to Treg-mediated cytotoxicity beyond their traditional suppressive roles [68].